Rao Martand Singh

Dr Rao Martand Singh

Lecturer of Geotechnical Engineering


Affiliations and memberships

Ground Engineering Group ICE Wales
Institute of Ground Source Heat Pump Association (IGSHPA)
Institute of Engineers India (IEI)
Australian Geomechanics Society (AGS)


Research interests

Research collaborations



Taha Sezer, Abubakar Kawuwa Sani, Rao Martand Singh, Liang Cui, David P. Boon, Michael Woods (2024)Numerical investigation of a district scale groundwater heat pump system: A case study from Colchester, UK, In: Applied thermal engineering236(Part E)121915

Nearly 40% of Europe’s total energy consumption is dedicated to buildings and heating/cooling make a significant part of this consumption. Groundwater heat pumps (GWHP) are highly efficient, and low-carbon technology that can supply heating/cooling to buildings on small or large scales. Thus, they contribute to achieving European targets of net-zero greenhouse gas emissions by 2050. In the literature, studies on the utilisation of GWHP at a district scale, particularly in chalk aquifers, are relatively rare. The implementation of district-scale geothermal heat pump (GWHP) systems poses several challenges, including dealing with the scale and complexity of the systems, addressing geological variability, managing high initial investments, balancing energy demand and supply, ensuring proper maintenance and monitoring, and mitigating potential environmental impacts. These challenges require careful consideration and strategic planning to ensure the successful deployment and sustainable operation of these systems., This study numerically investigates a district-scale GWHP system and analyses the thermal plume development created due to the heating operation, offering insights into system performance. A good match was found between field results and simulation results for water level increase and drawdown. However, there is a difference of approximately 11% in system efficiency between field tests and simulations due to the lower abstraction temperature detected in the simulation. The simulation results show that cooler water injection into the fractured chalk aquifer creates a thermal plume radially spanning out to 50 m. The thermal plume has no effect on the abstraction temperature and system performance. This result can be attributed to the large distance between injection and abstraction wells and the low hydraulic gradient.

Abubakar Kawuwa Sani, Rao Martand Singh (2020)Numerical investigation of the performance of group of geothermal energy piles in unsaturated sand, In: J.S. McCartney, I. Tomac (eds.), E3S web of conferences20505025

The use of foundation structures (piles) coupled to a heat pump system, commonly referred to as geothermal energy pile (GEP) system, provides a renewable energy solution of achieving space heating and cooling in buildings; whilst also being utilised for the structural stability of the overlying structures. The system operates by exchanging the low-grade heat energy within the shallow earth surface with the building, via the circulation of heat carrier fluid enclosed in a high-density polyethylene plastic pipes. In summer, heat energy is extracted from the building and transferred into the ground to achieve space cooling. While in winter, the ground heat energy is harnessed and transferred to the building to achieve sustainable space heating. This paper investigates the thermal performance of group of GEP system under the effects of different initial soil pore water content. Through the five-year simulation’s period, it was found that the increase in soil pore water content decreases the possibility of thermal interaction between the GEPs in the group. Also, it was observed that the trend in maximum temperature witnessed within the soil domain decreases nonlinearly during the five years period.

Abubakar Kawuwa Sani, Isaac Olaniyi Olawoore, Rao Martand Singh (2021)Assessment of impregnating phase change materials into lightweight aggregates for development of thermal energy storage aggregate composites, In: Construction & building materials305 Elsevier Ltd

[Display omitted] •Energy storage of four PCMs (palm oil, shea butter, coconut oil, commercial bio-based) was investigated experimentally.•Thermogravimetric analysis and differential scanning calorimetry was carried out on the PCMs.•Simple immersion and vacuum impregnation of bio-based PCM into fly ash and glass lightweight aggregates.•18.56% and 30.66% maximum absorption capacity observed for the FAs and GAs via vacuum impregnation.•Epoxy resin and graphite powder coating provided a tough layer that prevented PCM leakage.•No detriment to the coated LWAs under salt attack, thermal loading, and abrasive forces. This study assesses the feasibility of the impregnation/encasement of phase change materials (PCM) into lightweight aggregates (LWAs) for engineering applications. Four types of plant-based PCMs (PCM1 – unrefined palm oil, PCM2 – unrefined shea butter, PCM3 – unrefined coconut oil, and PCM4 – Crodatherm PCM) are investigated at material level. Similarly, two types of LWAs are used in the investigations, namely, fly–ash aggregates (FA) and glass aggregates (GA). The aggregates are by-products of the fly-ash and glass wastes generated from the construction and demolition activities. The wastes generated are recycled into various forms to reduce/eliminate the need for landfill disposal, thereby, lowering carbon-based emissions, and minimise resource extraction activities within the construction sector. In the initial investigations of this study, PCM4 was found to be the most energy efficient of all the PCMs. PCM4 had a thermal energy storage value of 33.5 kJ/kg per pound sterling (£) in comparison to 21.43 kJ/kg/£, 27.6 kJ/kg/£ and 20.71 kJ/kg/£ for PCM1, PCM2 and PCM3, respectively. PCM4 was adopted and used for impregnation into the pulverised FA and GA LWAs. Maximum absorption capacities of about 18.56% and 30.66% for the FAs and GAs were observed via vacuum impregnation technique in comparison to 5.78% and 12.86% measured using simple immersion method for the FAs and GAs, respectively. To prevent leakage and avoid coalescing of the aggregates, the PCM impregnated LWAs were coated, first, with primer epoxy resin, followed by graphite powder. Two layers of coating were applied to arrive at a durable product that can withstand abrasive forces (abrasive value of 6 and 21% for the double and single coating), heating and cooling temperatures, salt attack and a combination of thermal load and salt attack that are expected during buildings’ construction or infrastructural development in the industry.

Abubakar Kawuwa Sani, Rao Martand Singh (2021)Long-term thermal performance of group of energy piles in unsaturated soils under cyclic thermal loading, In: Energies (Basel)14(14)4122 Mdpi

Geothermal energy piles (GEPs) are an environmentally friendly heat exchange technology that dualizes the role of the structural foundation pile for load support and in meeting the building heating/cooling need. Energy loops made from high-density polyethylene, which allow heat carrier fluid circulation, are fitted into the pile foundation elements to extract or inject and store heat energy in the soil surrounding the pile. This paper reports the results of a numerical study investigating the long-term behaviour of a group of energy piles embedded in unsaturated soils (sand and clay) under continuous cyclic heating and cooling load. Additionally, two scenarios were investigated where: (1) the whole GEPs were heated and cooled collectively; (2) alternate piles were heated and cooled. It was found that the trend of temperature magnitude at all the observed locations decreases with time as a result of the continuous heating and cooling cycles. Furthermore, subjecting alternate GEPs to the heating and cooling cycles result in lower temperature development in comparison to thermally activating all the GEPs in the group. This is attributed to the applied thermal load, which is 0.5 times that considered in the first case. However, this might not be the case where equal thermal load is applied on the GEPs in the two cases investigated.

Abubakar Kawuwa Sani, Rao Martand Singh (2018)Response of unsaturated soils to heating of geothermal energy pile, In: Renewable Energy Elsevier

Geothermal energy piles (GEPs) are an environmentally friendly heat exchange technology that dualizes the role of structural foundation pile for load support and in meeting the building heating/cooling need. Energy loops made from high-density polyethylene which allow heat carrier fluid circulation, are fitted into the pile foundation elements to extract or inject and store heat energy in the soil surrounding the pile. This paper reports the results of a numerical study investigating the response of an energy pile embedded in unsaturated soils (sand, silt and clay) to natural thermal recovery, after heat injection process. It was found that the increase in soil saturation, duration of heating operation i.e. intermittent (8 or 16 h heating) or continuous mode, magnitude of the heat injection rates influences the temperature changes in the soil surrounding the pile, consequently impacting on the system performance. Similarly, it was observed that temperature at all location approached initial state in a duration equal to about twice that of the heating time. In addition, it was found that imposing excessive heat flux on the pile results in the drying up of the surrounding soil leading to lower thermal conductivity thus decreasing the overall GEP system performance.

Oluwaseun Ogunleye, Rao Martand Singh, Francesco Cecinato (2021)Assessing the thermal efficiency of energy tunnels using numerical methods and Taguchi statistical approach, In: Applied thermal engineering185116377 Elsevier Ltd

•Identifying the most influential design parameters in energy tunnels is novel.•Concrete diffusivity and total pipe length are the most influential parameters.•Pipe thermal conductivity and absorber fluid diffusivity are the least influential.•Effect of pipe spacing in energy tunnels is not pronounced compared to other GHEs.•Optimisation guidance provided to improve the thermal design of energy tunnels. The use of ground source heat pump systems (GSHPs) with tunnels (so-called energy tunnels) to provide space heating and cooling is one of the latest concepts that has recently raised research interest but has not yet been commercially established. This study represents the first attempt to investigate the influence of design parameters on the energy efficiency of a GSHP using an underground tunnel as the energy geostructure. Seven important design parameters, namely absorber fluid diffusivity, concrete diffusivity, pipe thermal conductivity, pipe diameter, length of pipe, pipe spacing and absorber pipe location were considered. The influence of these design parameters on the tunnel thermal efficiency was studied by using an experimentally validated 3-D numerical model and then deploying the Taguchi method to efficiently explore parameters space. The results show that concrete diffusivity and pipe total length are the most influential parameters, followed by the pipe location and diameter, while spacing was found to be the least influential factor. Hence the overall thermal output of an energy tunnel depends largely on the available area for heat exchange and the thermal properties of the tunnel lining. Results also show that within the range of pipe diameter considered, using a larger pipe diameter in energy tunnels is more efficient from the thermal output and pump power requirements. These results can be used as thermal efficiency optimisation guidance for both researchers and practitioners.

Md A. Rouf, Abdelmalek Bouazza, Rao M. Singh, Will P. Gates, Ronald K. Rowe (2016)Gas migration through geomembrane/ geosynthetic clay liner composite liner with a defect in the geomembrane, In: Japanese Geotechnical Society Special Publication2(57)pp. 1972-1977 Japanese Geotechnical Society

(GMB)/geosynthetic clay liner (GCL) composite liner where the GMB contained a circular defect and the GCL was partially hydrated. The results indicate that gas leakage rate increased with increasing gas differential pressure and increase of the GCL total suction. It was also observed that gas leakage rate reduced with the increase of the gravimetric water content of the GCL.

PJ Cleall, RM Singh, HR Thomas (2011)Non-isothermal moisture movement in unsaturated kaolin: An experimental and theoretical investigation, In: ASTM Geotechnical Testing Journal34(5)pp. 514-524 ASTM International

Non isothermal moisture movement in unsaturated kaolin is investigated in a series of experiments. Vapour transfer is then empirically quantified, and its theoretical representation considered. A thermo-hydraulic cell is used to apply thermal and hydraulic gradients to confined specimens in a number of thermal gradient, thermal-hydraulic gradient, and isothermal-hydraulic tests. Transient measurements of the thermal regime are made, and end of test measurement of moisture content, porosity, and chemical composition from a number of identical tests run for different durations allow pseudo transient variations of these parameters to be established. In each of the tests, where a thermal gradient is applied, the accumulation of chloride ions in the hottest regions indicates a cyclic movement of vapour and liquid moisture. Estimated vapour fluxes are determined by consideration of overall moisture and conservative ion movements in the sealed thermal gradient tests. These vapour fluxes are then compared to those predicted by an established vapour flow theory, and a modification to this theory is proposed based on a variable enhancement factor.

Norma Patricia Lopez-Acosta, Diana Margarita Portillo-Arreguin, David Francisco Barba-Galdamez, Rao Martand Singh (2022)Thermal properties of soft clayey soils from the former Lake Texcoco in Mexico, In: Geomechanics for energy and the environment32100376 Elsevier

Thermal properties of soils are essential for the design of many engineering projects, such as under-ground cable systems, thermal ground improvement techniques, and energy geostructures. Although the thermal properties of typical soils have been widely studied, little research has focused on the thermal characterization of soils with unusual properties, such as the soft clays from the former Lake Texcoco in Mexico. These sediments are known for their exceptionally high water content, plasticity index, and porosities. The present study describes a systematic evaluation of the thermal conductivity, specific heat capacity, and thermal diffusivity of Texcoco clays and their inherent variability. Forty laboratory samples from eleven different locations were studied using the dual-probe heat pulse method, X-ray diffractometry, Scanning Electron Microscopy, and standard soil classification tests. The results showed that the studied samples have lower thermal conductivities and higher specific heat capacities than those previously reported for saturated clays. These differences were mainly attributed to the high porosities of the peculiar clays from the former Lake Texcoco. The thermal conductivity did not show a specific trend with depth. From statistical analyses, it was established that the shifted lognormal distribution and the normal distribution accurately describe the natural variability of the thermal conductivity and specific heat capacity, respectively. Finally, the efficacy of eight selected prediction models for the thermal conductivity of saturated clays was assessed. The geometric mean and the weighted series-parallel heat flow (WSP) models delivered the best fit to the experimental data. This study deepens our understanding of ground thermal properties by providing information about soil with unusual characteristics. Furthermore, it gives an initial database for the thermal properties of Mexican soils that can serve as a reference for the development and design of some of the geotechnical applications previously described. (c) 2022 Elsevier Ltd. All rights reserved.

Thaise da Silva Oliveira Morais, Cristina de Hollanda Cavalcanti Tsuha, Luis Antonio Bandeira Neto, Rao Martand Singh (2020)Effects of seasonal variations on the thermal response of energy piles in an unsaturated Brazilian tropical soil, In: Energy and buildings216109971 Elsevier

A large amount of Brazilian electricity consumption is building related, and mainly consumed by airconditioning systems due to the warm tropical weather; therefore, geothermal energy piles integrated with heat pump seem to be an interesting alternative for the building cooling demand in this country. Tropical residual soils in unsaturated condition cover a significant part of the Brazilian territory, and due to the alternation of dry and rainy periods the groundwater level and the gravimetric water content of the soils vary seasonally. Considering that the efficiency of energy piles as heat exchangers is highly dependent on soil thermal properties, which in turn rely on the soil saturation, to evaluate the seasonal effects on the thermal response of energy piles in a typical site of Brazilian unsaturated tropical soil, an extensive program of field tests and monitoring supplemented by laboratory work was carried out during a period of four years, and is reported in this paper. The results demonstrate that the thermal response of the energy pile investigated is variable throughout the year. The thermal conductivity of the soil surrounding the pile determined at the end of the rainy season can be reduced approximately 32% at the end of the dry season. This finding indicates that the seasonal variation of soil thermal properties should be considered in the design of GSHP systems with energy piles in similar soil and climate conditions. (C) 2020 Elsevier B.V. All rights reserved.

A.S. Acikel, A. Bouazza, W.P. Gates, R.M. Singh, R.K. Rowe (2020)A novel transient gravimetric monitoring technique implemented to GCL osmotic suction control, In: Geotextiles and geomembranes48(6)755pp. 755-767 Elsevier Ltd

A modified osmotic suction control technique for monitoring apparent transient weight changes was successfully adapted to the wetting and drying paths of geosynthetic clay liners (GCLs). Reasonable control was possible, enabling suction equilibrium to be achieved without disruption to the test. The results provide unique insight into the time-dependent changes in water retention properties and the semi-permeable membrane behaviour of the bentonite component in GCLs. The stages of suction equilibrium, related to the tri-modal pore structure of GCLs and the point of capillary break, could also be monitored. While the osmotic method has been traditionally used to control matric suction (up to 10 MPa) in soils, the overall results presented in this paper indicate that its application for total suction control in GCLs is largely due to the membrane behaviour of their bentonite component. Furthermore, because of capillary break between the GCL and the osmotic solution at the water entry (or residual) suction value of a GCL, an upper limit of 2.8 MPa suction is recommended for the application of the osmotic method to measure the water retention properties of GCLs. •Real-time transient weight change monitoring was implemented on osmotic suction control of GCL on wetting and drying paths.•Capillary break, suction equilibrium, and time dependency were monitored without specimen disturbance.•Osmotic technique is recommended for total (instead of matric) suction control of GCLs due to bentonite membrane behavior.•Osmotic technique has an applicable upper limit of 2.8 MPa corresponds to GCL water entry (residual) suction value.

A. S. Acikel, A. Bouazza, R. M. Singh, W. P. Gates, R. K. Rowe (2022)Challenges of the Filter Paper Suction Measurements in Geosynthetic Clay Liners: Effects of Method, Time, Capillarity, and Hysteresis, In: Majdi Othman (eds.), Geotechnical testing journal45(2)GTJ20200168pp. 449-467

Time and method dependencies, lack of sufficient capillary connections, and wetting-drying hysteresis may cause inaccurate results from filter paper tests (FPTs) when used for suction measurements of geosynthetic clay liners (GCLs). These limitations of the filter paper method for suction measurements of GCLs were investigated using initially dry contact, initially wet contact, and noncontact FPTs. Wetting-drying hysteresis was observed in the initially dry contact and noncontact FPTs and was significantly higher in the latter. The initially wet contact and initially dry contact FPTs were reliable in measuring matric and total suction, respectively. These two methods can provide suction measurements from both the cover and the carrier geotextile sides of the GCLs (i.e., from the hydratable surfaces of the GCL after installation on site), thus allowing suction measurements without impacting the integrity of the geotextile-bentonite-geotextile structure. Suction measurements on a granular bentonite-based GCL showed higher time dependency compared with powdered bentonite-based GCLs. For the specific GCLs and conditions tested, the woven and nonwoven scrim-reinforced geotextile structure causes pronounced capillary break effects on the hydratable surface of GCL. In contrast, the woven geotextile structure has a minimal impact. When the FPT procedures are applied to GCLs, the interpretation of the results requires careful consideration of the method and time dependencies, wetting-drying hysteresis, capillary breaks, and how the measurements of total or matric suction are performed.

Kishan Kumar Prajapati, Monika Yadav, Rao Martand Singh, Priti Parikh, Nidhi Pareek, Vivekanand Vivekanand (2021)An overview of municipal solid waste management in Jaipur city, India - Current status, challenges and recommendations, In: Renewable & sustainable energy reviews152111703 Elsevier Ltd

In developing countries, urbanization and rapid population growth has resulted in a substantial increase in generation of Municipal Solid Waste (MSW). Safe collection, transportation and treatment of MSW are among the major issues for Indian cities. Poor MSW management practices have negative impact on public health, environment and climate change. India currently only treats 21% of MSW while the remainder disposed in unsanitary landfill sites with no recycling and treatment technologies. This paper reviews the existing MSW management practices, challenges and provides recommendations for improving MSW management for the city of Jaipur in Rajasthan, India. Despite being the state capital as well as the top tourist destination in northern part of India, there is no detailed study which reviews the waste management strategies of this city along with identifying the key challenges. The study reveals that the major challenges for MSW management in Jaipur include uncontrolled landfilling, inadequate public participation as well as failings of implementation of MSW legislation and waste conversion. Recommendations for improvement include public awareness campaigns, public-private partnership, investment in lined landfills, recycling and waste to energy techniques. Optimization models and life cycle assessment tools should be employed to minimize cost and the environmental impact of MSW management. This study will provide policy makers and private sector stakeholders to develop strategies for future planning, investment and execution of improved MSW management in Indian cities. [Display omitted] •In Jaipur city 50% MSW is treated while rest is subjected to unsanitary landfilling.•Indian cities have inadequate MSW management practices treating only 21% of MSW.•Lack of public participation, proper treatment techniques and sanitary landfill in the city.•Recycling facilities, waste to energy techniques and sanitary landfilling is required.•Role of optimization and LCA models in planning suitable MSW management practices.

Poonam Shekhawat, Gunwant Sharma, Rao Martand Singh (2023)Morphology and microstructure of waste material-based geopolymer with flyash, eggshell powder, and soft soil, In: Materials letters334133621 Elsevier B.V

•The formation of the highest cementitious product and geopolymeric gel NASH for the novel geopolymer.•The CASH gel co-existed along with the highest cementitious product due to the inclusion eggshell powder.•Curing of samples at 50 °C for 7 days resulted in well-reacted precursor particles.•The geopolymeric gel reinforced the clay particles filling the voids.•Eggshell powder-flyash geopolymer can substitute cement in soft soil stabilization. The morphological and microstructural evolution of flyash (FA), eggshell powder (ESP), and soft soil (S) geopolymer was studied. The variable parameters for synthesis was precursor concentration (10 %, 20 %, 30 %, 40 %, and 50 %) in soft soil, whereas ESP:FA ratio as 50:50, Na2SiO3:NaOH ratio as 70:30, and curing condition as 50 °C for 7 days were the fixed parameters. The effect of these parameters on the geopolymerization was explained using field emission gun-scanning electron microscopy including an energy dispersive X-ray spectrometer and mapping. The calcium aluminate silicate hydrate gel co-existed along with the highest cementitious product. The geopolymeric gel structure filled the voids between soft soil particles and reinforced the whole matrix.

Poonam Shekhawat, Gunwant Sharma, Rao Martand Singh (2020)Microstructural and morphological development of eggshell powder and flyash-based geopolymers, In: Construction & building materials260119886 Elsevier Ltd

•Geopolymer was prepared by using eggshell powder and flyash as precursors.•Geopolymer microstructure and morphology altered with change in precursor replacement and thermal curing.•Geopolymers cured at 50 °C for 7 days showed well compacted structure with more reaction products.•EDX and mapping confirmed enhanced dissolution of Si and Al at high activator ratio and thermal curing.•The reaction product contains C-S-H gel co-existing with the main geopolymeric gel N-A-S-H. The microstructural and morphological development of eggshell powder (ESP) and flyash (FA)-based geopolymer, prepared using alkaline liquid activator which is a mixture of sodium silicate and sodium hydroxide solution, was investigated. Various synthesis parameters for geopolymer were adopted to study the microstructural changes viz. precursor combination (70% ESP and 30% FA, 50% ESP and 50% FA, 30% ESP and 70% FA), activator ratio (Na2SiO3/NaOH–0.5, 1, and 2) and curing temperature (25, 50, and 80 °C). Morphological features and structural characterization of raw precursor materials were analyzed using an X-ray diffractometer (XRD), X-ray fluorescent (XRF), and Scanning electron microscopy (SEM) techniques. The process of geopolymerization was explicated using SEM with an energy dispersive X-ray spectrometer (SEM-EDX) and mapping. Increase in curing temperature altered the morphology of ESP-FA geopolymer. Curing of samples at the lower temperature resulted in unreacted precursor particles, whereas curing at the higher temperature resulted in the porous structure. Formation of Nan–(–Si–O–Al–O–Si–O–Si–O–)n– was confirmed in the optimum geopolymer as Si/Al and Na/Al ratios were found greater than 1. The co-existence of calcium silicate hydrate (C-S-H) gel with the main geopolymeric gel and its bonding with the remaining unreacted precursor particles have also been confirmed.

Simona Adrinek, Rao Martand Singh, Mitja Janza, Mateusz Zerun, Grzegorz Ryzynski (2022)Evaluation of thermal conductivity estimation models with laboratory-measured thermal conductivities of sediments, In: Environmental earth sciences81(15)380 Springer Nature

Thermal conductivity is one of the key parameters for estimating low-temperature geothermal potential. In addition to field techniques, it can be determined based on physical parameters of the sediment measured in the laboratory. Following the methodology for cohesive and non-cohesive sample preparation, laboratory measurements were carried out on 30 samples of sediments. Density, porosity and water content of samples were measured and used in thermal conductivity estimation models (TCEM). The bulk thermal conductivity (lambda(b)) calculated with six TCEMs was compared with the measured lambda(b) to evaluate the predictive capacity of the analytical methods used. The results show that the empirical TCEMs are suitable to predict the lambda(b) of the analysed sediment types, with the standard deviation of the residuals (RMSE) ranging from 0.11 to 0.35 Wm(-1) K-1. To improve the fit, this study provides a new modified parameterisation of two empirical TCEMs (Kersten and Cote&Konrad model) and, therefore, suggests the most suitable TCEMs for specific sample conditions. The RMSE ranges from 0.11 to 0.29 Wm(-1) K-1. Mixing TCEM showed an RMSE of up to 2.00 Wm(-1) K-1, meaning they are not suitable for predicting sediment 2b. The study provides an insight into the analytical determination of thermal conductivity based on the physical properties of sediments. The results can help to estimate the low-temperature geothermal potential more quickly and easily and promote the sustainable use of this renewable energy source, which has applications in environmental and engineering science.

Habibollah Sadeghi, Amir Ijaz, Rao Martand Singh (2022)Current status of heat pumps in Norway and analysis of their performance and payback time, In: Sustainable energy technologies and assessments54102829 Elsevier

A significant part of energy in Norway is utilized for space heating due to the cold climate and heat pump technology has gained popularity in the country for space heating. According to the European heat pump as-sociation, Norway has the most heat pumps per capita in Europe, providing 16 TWh of heat energy annually. This review paper discusses the most common types of heat pumps in Norway. A comparison between the perfor-mance and payback time of different types of heat pumps in Norway is presented. Ground source heat pumps are more suitable than air source heat pumps due to maintaining a higher coefficient of performance during cold periods. The amount of thermal energy extracted using ground source heat pump systems is estimated to be 3 TWh and expected to be 8 TWh by 2030. However, more than 90% of heat pump installations in Norway are air source heat pumps. Compared to air source heat pumps, ground source heat pumps face many challenges, such as high initial cost, lack of public awareness, and insufficient professional workforce. The sales of heat pumps dropped by 13% in 2020, mainly due to the Covid-19 impact on the market. However, the sales increased significantly in 2021 due to the ongoing energy crisis and increase in energy prices.

Habibollah Sadeghi, Rao Martand Singh (2023)Driven precast concrete geothermal energy piles: Current state of knowledge, In: Building and environment228109790 Elsevier

Geothermal energy piles are increasingly luring attention in the construction industry as a cost-effective and environmental friendly solution for heating and cooling buildings. Energy piles are used as the primary unit in the ground source heat pump systems, which exchange heat with the ground. Energy piles are generally categorized into driven (displacement) and cast-in-place (non-displacement) piles. The present paper aims to review the available methods of design and construction of driven precast concrete energy pile foundations and provides a clear understanding of its construction challenges. Additionally, precast and cast-in-place energy pile foundations are compared. This paper found that precast concrete-driven energy pile foundations are a competitive alternative to cast-in-place energy piles. Driven concrete energy piles have higher quality control and quality assurance in the construction process; they have an easier, faster, and more reliable installation. Several other advantages and limitations related to the technical, economical, and environmental aspects of such piles are discussed in detail. The driven precast concrete foundations have a large worldwide market; however, there is a lack of guidelines, design standards, and experience for using such foundations as energy piles.

Poonam Shekhawat, Gunwant Sharma, Rao Martand Singh (2022)A Comprehensive Review of Development and Properties of Flyash-Based Geopolymer as a Sustainable Construction Material, In: Geotechnical and geological engineering40(11)5607pp. 5607-5629 Springer Nature

Globally, cement is the highest utilized pozzolanic material in construction. Consequently, yearly ordinary Portland cement is manufactured in enormous amounts worldwide. Manufacturing of cement is a natural resource and energy consuming process which involves greenhouse gas CO2 release in the air in vast amount. The utilization of ordinary Portland cement in construction can be lessened by replacing it with some other by-product cementitious material having equal or higher mechanical strength and durability. This paper discusses the impact of cement manufacturing on the environment and gives the background to the requirements for the invention of alternate binders over conventional binders like cement. Many researchers attempted to produce an environmentally friendly binder, "Geopolymer". This paper aims to present an overview of past and recent studies on the utilization of flyash and other waste materials in developing geopolymer as a sustainable construction material. Description of the production of geopolymer, the chemistry of geopolymerization, microstructural analysis, and its relationship with mechanical strength and durability of geopolymer are reviewed. Moreover, the influence of the inclusion of calcium-based waste material in geopolymerization is reviewed and reported. Many researchers reported higher strength of a flyash-based geopolymer composite than the conventional cement composite.

A Bouazza, RM Singh, RK Rowe, F Gassner (2014)Heat and moisture migration in a geomembrane–GCL composite liner subjected to high temperatures and low vertical stresses, In: Geotextiles and Geomembranes,42(5)pp. 555-563

This paper presents the results of an experimental and numerical modelling of heat and moisture migration conducted on a composite liner comprised of a geomembrane (GMB) and a geosynthetic clay liner (GCL), over a compacted subgrade and subjected to prolonged elevated temperatures at low overburden stresses typical of brine storage ponds or solar evaporation ponds. Results are presented for a GMB sitting on a fully hydrated GCL. Heating the top of the composite liner caused a measurable increase in subgrade temperature to at least to 250 mm below the GCL. However, the presence of an air gap, simulating the presence of a wrinkle in the geomembrane, at the interface between the GMB and the GCL reduced the impact of the high temperatures on the subgrade temperature profile with depth. The change in temperature profile was accompanied by moisture migration from the GCL to the subgrade material. However no desiccation cracks were observed in the GCL and the bentonite was still in a gel form at the end of the time period investigated. Numerical modelling using finite element method (FEM) was performed to simulate the results obtained experimentally. It was found to predict accurately the temperature changes that have occurred in the subgrade material and moisture changes that occurred in both the GCL and subgrade materials.

A Bouazza, J Zornberg, JS McCartney, RM Singh (2013)Unsaturated geotechnics applied to geoenvironmental engineering problems involving geosynthetics, In: Engineering Geology165pp. 143-153

Movement of fluids in the unsaturated zone plays an important role in many geoenvironmental engineering problems. Examples include cover and basal liner systems for waste containment facilities where geosynthetics are widely used, amongst many other examples. This paper highlights the importance of assessing the unsaturated characteristics of geosynthetics and their influence on the behaviour of engineered systems where soils and geosynthetics interact under unsaturated conditions. It includes information on the water retention curve and hydraulic conductivity function of geosynthetics such as geotextiles and geosynthetic clay liners (GCLs) with particular focus on capillary barriers, liner performance under elevated temperatures, and interface friction respectively. Mechanisms involved in the development of capillary barriers are evaluated to explain the storage of water at the interface between materials with contrasting hydraulic conductivity (e.g. a fine-grained soil and a nonwoven geotextile). Potential desiccation of GCLs is explained in the light of an application in a liquid waste impoundment.

RM Singh, A Bouazza (2013)Thermal conductivity of geosynthetics, In: Geotextiles and Geomembranes39pp. 1-8 Elsevier

Thermal conductivity is a key property that controls heat migration in a variety of applications including municipal solid waste and/or mining/industrial containment facilities. In particular, heat may be encountered in cases where geosynthetic lining systems are exposed to elevated temperatures due to either waste biodegradation, solar radiation, or mining processes. This paper presents the results of an experimental investigation on thermal conductivity of nonwoven geotextiles, geosynthetic clay liners and an HDPE geomembrane. A steady state method was used to measure the thermal conductivity of a selected number of these materials. The thermal conductivity of the HDPE geomembrane was found to be consistent with the thermal conductivity of HDPE polymer. On the other hand, the thermal conductivity of the nonwoven geotextiles depended on water content and whether they are hydrophobic or hydrophilic. The form of bentonite, its mass per area and water content affected the thermal conductivity of GCLs. The results presented in this paper provide a lower bound of thermal conductivities of geosynthetics routinely used in waste containment facilities.

MA Rouf, RM Singh, A Bouazza, RK Rowe, WP Gates (2015)Gas permeability of partially hydrated geosynthetic clay liner under two stress conditions, In: Environmental Geotechnics ICE Publishing

The results of a series of gas permeability tests, with monitoring of gravimetric/volumetric moisture content and total suction, on a commercially available needle-punched geosynthetic clay liner (GCL) are presented. GCL specimens were partially hydrated with deionised water under 2 and 20 kPa confinement prior to testing. The tests were conducted at differential pressures ranging from 1 to 10 kPa. Gas permeability was found to decrease with an increase in gravimetric/volumetric moisture content and a decrease of suction. The effect of the preconditioning stress was found to be more pronounced at gravimetric moisture contents greater than 40% (25% apparent degree of saturation, 0·30 m3/m3 volumetric moisture content), and suctions less than 1·6 MPa.

D Barry-Macaulay, A Bouazza, RM Singh, B Wang, PG Ranjith (2013)Thermal conductivity of soils and rocks from the Melbourne (Australia) region, In: Engineering Geology164pp. 131-138 Elsevier

The thermal conductivity of soils and rocks is an important property for the design of thermally active ground structures such as geothermal energy foundations and borehole heat exchange systems. This paper presents the results of a laboratory study of the thermal conductivity of soils and rocks from around Melbourne, Australia. The thermal conductivity of six soils and three rock types was experimentally measured using both a thermal needle probe and a divided bar apparatus. Soil samples were tested at a wide range of moisture contents and densities. The results demonstrated that the thermal conductivity varied with soil moisture content, density, mineralogical composition and particle size. Coarse grained soils were observed to have a larger thermal conductivity than fine grained soils. In addition, the thermal conductivity of soils increased with an increase in dry density and moisture content. Siltstone, sandstone and basalt rock samples were tested dry and water saturated. They demonstrated an increase in thermal conductivity with an increase in density when dry. However, when water saturated, siltstone and sandstone showed no significant correlation between density and thermal conductivity; whereas a linear increase in thermal conductivity with density was observed for the saturated basalt samples. These differences were attributed to both variations in mineralogy and anisotropy of each sample. The thermal conductivity data obtained from this study provides an initial database for soils and rocks from the Melbourne (Australia) region which can serve for the design of thermo-active structures installed locally and in locations with similar ground conditions.

PJ Cleall, RM Singh, HR Thomas (2013)Vapour transfer in unsaturated compacted bentonite, In: Geotechnique: international journal of soil mechanics63(11)pp. 957-964 ICE Publishing

Results of an experimental and theoretical investigation of heat and moisture movement in unsaturated MX-80 bentonite are presented. A thermo-hydraulic cell that allows measurement of transient temperatures and facilitates the determination of pseudo-transients of moisture content, dry density and chemical composition has been used to perform thermal gradient tests. Results of a number of tests are presented, and observation of the accumulation of chloride ions near the hot end clearly indicates that there is a cycle of vapour and liquid moisture movement, with vapour moving from hotter to cooler regions, condensing, and then moving as liquid towards the hotter regions. An empirical method is applied to calculate approximate vapour fluxes using measured variations in chloride ion concentration and moisture content with time. The vapour fluxes calculated empirically are found to be lower than those determined by some existing vapour flow theories. Subsequently, an existing vapour flow model is modified to represent the observed vapour fluxes more closely.

KL Yu, RM Singh, A Bouazza, HH Bui (2015)Determining Soil Thermal Conductivity Through Numerical Simulation of a Heating Test on a Heat Exchanger Pile, In: Geotechnical and Geological Engineering33(2)pp. 239-252

Heat exchanger pile foundations have a great potential of providing space heating and cooling to built structures. This technology is a variant of vertical borehole heat exchangers. A heat exchanger pile has heat absorber pipes firmly attached to its reinforcement cage. Heat carrier fluid circulates inside the pipes to transfer heat energy between the piles and the surrounding ground. Borehole heat exchangers technology is well established but the heat exchanger pile technology is relatively new and requires further investigation of its heat transfer process. The heat transfer process that affects the thermal performance of a heat exchanger pile system is highly dependent on the thermal conductivity of the surrounding ground. This paper presents a numerical prediction of a thermal conductivity ground profile based on a field heating test conducted on a heat exchanger pile. The thermal conductivity determined from the numerical simulation was compared with the ones evaluated from field and laboratory experiments. It was found that the thermal conductivity quantified numerically was in close agreement with the laboratory test results, whereas it differed from the field experimental value.

RM Singh, A Bouazza, B Wang (2015)Near-field ground thermal response to heating of a geothermal energy pile: Observations from a field test, In: Soils and Foundations55(6)pp. 1412-1426 Elsevier

Field observations from a heating test conducted on a geothermal energy pile, containing two Osterberg cells, installed in a dense sandy material are reported. An instrumented pile and two boreholes were installed for this purpose. The pile was heated for various time intervals and the ground heat response was observed via thermocouples installed at various depths in the two boreholes. A time lag in the diffused heat wavefront arrival was consistently observed in the borehole farthest from the heat source (i.e. pile). This suggests heat diffused slowly in the ground and its intensity reduced with distance from the heat source. Heat transfer was affected by the ground stratigraphy. The pile and the ground were allowed to cool by letting heat dissipate naturally once the heating test was completed. It was found that both the pile and the ground required at least more than twice the heating time to have full thermal recovery from the heating process. A constant heat exchange rate (or heat rejection rate) of 100–125 W/m2 was achieved, despite continuous rise in temperature of the pile and the ground.

B Wang, A Bouazza, RM Singh, C Haberfield, D Barry-Macaulay, S Baycan (2014)Posttemperature Effects on Shaft Capacity of a Full-Scale Geothermal Energy Pile, In: Journal of Geotechnical and Geoenvironmental Engineering141(4)04014125 American Society of Civil Engineers

Shallow geothermal heat exchangers integrated in structural pile foundations have the capability of being an efficient and costeffective solution to cater for the energy demand for heating and cooling of built structures. However, limited information is available on the effects of temperature on the geothermal energy pile load capacity. This paper discusses a field pile test aimed at assessing the impact of thermomechanical loads on the shaft capacity of a geothermal energy pile. The full-scale in situ geothermal energy pile equipped with ground loops for heating/cooling and multilevel Osterberg cells for static load testing was installed at Monash University, Melbourne, Australia in a sandy profile. Strain gauges, thermistors, and displacement transducers were also installed to study the behavior of the energy pile during the thermal and mechanical loading periods. It has been found that the pile shaft capacity increased after the pile was heated and returned to the initial capacity (i.e., initial conditions) when the pile was allowed to cool naturally. This indicated that no losses in pile shaft capacity were observed after heating and cooling cycles. A variance in average vertical thermal strains was observed along the upper section of the pile shaft at the end of the heating periods. These were almost fully recovered at the end of the cooling periods, indicating that they are of an elastic nature. Pile average circumferential strains were found to be relatively uniform at the end of the heating and cooling periods and did not change with depth. They, also, were fully recovered during the cooling period. It was also observed that the increase of temperature during the heating periods prompted the pile shaft to expand radially. Subsequently, as the pile cooled down, the pile shaft slowly contracted and returned closely to its original condition, suggesting a thermoelastic behavior.

M de Moel, PM Bach, A Bouazza, RM Singh, OS JingLiang (2010)Technological advances and applications of geothermal energy pile foundations and their feasibility in Australia, In: Renewable and Sustainable Energy Reviews14(9)pp. 2683-2696 Elsevier

Geothermal energy pile foundations are an alternative energy source for heating and cooling needs. Utilising this source of energy has great potential due to the environmental, economic and social benefits. This paper looks at an extensive amount of literature on the technology behind the system including the overall process, primary considerations for each of the main components including latest developments as well as design implications such as the integration of ground energy systems into structural piles of buildings. Environmental considerations including performance-dependent parameters of the subsurface are described. Main parameters include thermal conductivity, thermal diffusivity, specific heat capacity and moisture content. Temperature and groundwater effects are also discussed and design considerations are provided. Mathematical models are available to aid in the design of these systems but there are various other issues and complex parameters that need to be considered qualitatively. Furthermore, the design of these systems is governed by various standards and government legislation. Case studies are presented to show the application of these systems in practise including assessments of system performance. Examples originate from countries such as Austria, Switzerland, Germany, UK, USA, Japan, Iran, Sweden and Norway. Benefits and limitations of implementing these systems are summarised and finally, the feasibility of geothermal energy pile foundations in Australia is explored. This paper found that these systems, although exhibiting some limitations and possible challenges, are a viable option in terms of an alternative energy source.

Mohammed Faizal, Abdelmalek Bouazza, Rao M. Singh (2016)An experimental investigation of the influence of intermittent and continuous operating modes on the thermal behaviour of a full scale geothermal energy pile, In: Geomechanics for Energy and the Environment8pp. 8-29 Elsevier Ltd

Ground sourced heat pumps coupled with geothermal energy piles operate either continuously or intermittently depending on the heating or cooling needs of a built structure, giving rise potentially to variable thermal loads in the piles. This paper presents an experimental investigation on the influence of intermittent and continuous operations on energy extracted, ground and pile temperatures, and axial thermal strains and stresses of a full scale geothermal energy pile for daily cooling operation. Experiments were conducted for a 24 hours continuous operation (24 h mode), 16 hours operation with 8 hours rest (16 h mode), and 8 hours operation with 16 hours rest (8 h mode). It is generally found that the lower operating hours lead to higher energy extracted from the ground with lower thermal loads on the pile and the ground. The energy extracted was 40.9% and 14.8% higher in the 8 h and 16 h modes, respectively, compared to the 24 h mode. The ground temperatures for the 8 h and 16 h modes were 14.5% and 5.9% higher than the 24 h mode, respectively. The average thermal stresses in the pile for the 8h and 16 h modes were 42.3% and 12.2% lower than the 24 h mode, respectively. The results of the present study also showed that the soil did not affect the elasticity of the axial thermal strains between end of cooling and recovery of the intermittent modes for daily thermal cycles.

Komali Kantamaneni, Xiaoping Du, Sainath Aher, Rao Martand Singh (2017)Building Blocks: A Quantitative Approach for Evaluating Coastal Vulnerability, In: Water9(12) MDPI

Climate change and associated factors such as global and regional sea-level rise; the upsurge in high-intensity flooding events; and coastal erosion are pulse and press disturbances that threaten to increase landslides in coastal regions. Under these circumstances; a rigorous framework is required to evaluate coastal vulnerability in order to plan for future climate change scenarios. A vast majority of coastal vulnerability assessments across the globe are evaluated at the macro level (city scale) but not at the micro level (small town scale); particularly in the United Kingdom (UK). In order to fill this vital research gap; the current study established a coastal vulnerability index termed here as the Micro Town Coastal Vulnerability Index (MTCVI) and then applied it to Barton-on-Sea; which is a small coastal town of the Hampshire region; England; UK. MTCVI was evaluated for Barton-on-Sea coastal vulnerability by integrating both novel and existing parameters. Results suggest that the entire shoreline frontage (2 km) exhibits very high coastal vulnerability and is prone to various coastal hazards such as landslides; erosion; and wave intrusion. This suggests that Barton-on-Sea coastal amenities will require a substantial improvement in shoreline protection measures. In this study; GIS (geographic information system) coastal vulnerability and landslide maps were generated; and these maps can be used by the local authorities; district councils; coastal engineers; and planners to improve and design coastal management strategies under the climate change scenarios. Meanwhile; the methodology used in this study could also be applied to any other suitable location in the world depending on the availability of the data.

Mohammad Ali, Abdelmalek Bouazza, Rao Martand Singh, Will P. Gates, R. Kerry Rowe (2016)Thermal conductivity of geosynthetic clay liners, In: Canadian Geotechnical Journal53(9)pp. 1510-1521 NRC Research Press (Canadian Science Publishing)

The thermal conductivities of powdered and granular bentonite based needle punched geosynthetic clay liners (GCLs) were investigated at different gravimetric water contents under 25, 50, 75, and 100 kPa vertical stresses. Both types of GCLs exhibited an increase in thermal conductivity with increasing vertical stress at all water contents. The effect of vertical stresses was more pronounced for the specimens hydrated at lower gravimetric water contents and this was attributed to their high initial volumetric air content. The variability of water distribution in partially hydrated GCLs has been identified as a factor that may affect their thermal conductivity. The forms of bentonites (i.e., powder or granular) affected their thermal conductivities; however, this effect was less apparent at higher gravimetric water contents due to the reduced air content and gel formation in the bentonites. Finally, the GCL thermal conductivity calculated from the measured thermal conductivities of its various constituents (i.e geotextile and bentonite) components differed from the measured values. This was attributed to the nonuniform water distribution across the GCL specimen and change in material properties when components of GCL were disassembled.

M Faizal, A Bouazza, Rao Singh (2016)Heat transfer enhancement of geothermal energy piles, In: Renewable and Sustainable Energy Reviews57pp. 16-33 Elsevier

Geothermal energy piles utilize the almost constant ground temperature at shallow depths below the ground surface to heat and/or cool built structures. Heat is extracted from and/or injected into the ground through the use of a heat carrier fluid that flows in pipes attached to the reinforcement cage of the pile foundations. The performance of the energy piles can be improved by enhancing the heat exchange between the heat carrier fluid and the ground. The purpose of this paper is to provide evidence from literature on multidisciplinary methods to improve the thermal properties of elements in a geothermal energy pile. Geometrical optimization such as the number of pipes and their arrangement can be done to reduce the total pile thermal resistance. Nanofluids can be used as the heat carrier fluid to enhance the fluid conductive and convective heat transfer. Highly thermally conductive fillers can be mixed with the pipe material to enhance its thermal conductivity. The thermal properties of the concrete can also be enhanced by adding highly thermo-conductive materials to the concrete mix.

A Rouf, A Bouazza, Rao Singh, WP Gates, RK Rowe (2016)Gas flow unified measurement system for sequential measurement of gas diffusion and gas permeability of partially hydrated geosynthetic clay liners, In: Canadian Geotechnical Journal53(6)pp. 1000-1012

A gas flow unified measurement system (UMS-G) for sequential measurement of gas diffusion and gas permeability of geosynthetic clay liners (GCLs) under applied stress conditions (2 to 20 kPa) is described. Measurements made with the UMS-G are compared with measurements made with conventional experimental devices and are found to give similar results. The UMS-G removes the need to rely on two separate systems and increases further the reliability of the gas properties’ measurements. This study also shows that the gas diffusion and gas permeability reduce greatly with the increase of both gravimetric water content and apparent degree of saturation. The effect of applied stress on gas diffusion and gas permeability is found to be more pronounced at gravimetric water content greater than 60%. These findings suggest that at a nominal overburden stress of 20 kPa, the GCL used in the present investigation needs to be hydrated to 134% gravimetric water content (65% apparent degree of saturation) before gas diffusion and gas permeability drop to 5.5 × 10−11 m2·s−1 and 8.0 × 10−13 m·s−1, respectively, and to an even higher gravimetric water content (apparent degrees of saturation) at lower stress.

A.S. Acikel, W.P. Gates, R.M. Singh, A. Bouazza, R.K. Rowe (2018)Insufficient initial hydration of GCLs from some subgrades: Factors and causes, In: GEOTEXTILES AND GEOMEMBRANES46(6)pp. 770-781 ELSEVIER SCI LTD

Water retention and hydration tests are reported for three needle punched geosynthetic clay liners (GCLs). GCLs hydration and their maximum hydration capacity were assessed against subgrade soils prepared at different initial gravimetric water contents. The subgrade soil mineralogy and particle size distribution, as well as the carrier geotextiles used in GCLs, are shown to have a significant impact on the GCLs hydration behaviour. This work highlights the need to consider the unsaturated properties of both the GCLs and the subgrade soil when assessing the hydration of the GCLs. At gravimetric water contents above the GCL water entry value (≈30%), some forms of GCL configuration may be better than others with respect to ability to hydrate from a given soil. However, the partial hydration of GCL is mostly controlled by the bentonite microstructure for gravimetric water contents below the water entry value of the GCLs.

V. Agarwal, D. Ho, D. Ho, Y. Galabura, F. Yasin, P. Gong, W. Ye, R. Singh, A. Munshi, M. Saunders, R.C. Woodward, T. St. Pierre, F.M. Wood, M. Fear, D. Lorenser, David Sampson, B. Zdyrko, I. Luzinov, N.M. Smith, K.S. Iyer (2016)Functional Reactive Polymer Electrospun Matrix, In: ACS Applied Materials and Interfaces8(7)pp. 4934-4939 American Chemical Society

Synthetic multifunctional electrospun composites are a new class of hybrid materials with many potential applications. However, the lack of an efficient, reactive large-area substrate has been one of the major limitations in the development of these materials as advanced functional platforms. Herein, we demonstrate the utility of electrospun poly(glycidyl methacrylate) films as a highly versatile platform for the development of functional nanostructured materials anchored to a surface. The utility of this platform as a reactive substrate is demonstrated by grafting poly(N-isopropylacrylamide) to incorporate stimuli–responsive properties. Additionally, we demonstrate that functional nanocomposites can be fabricated using this platform with properties for sensing, fluorescence imaging, and magneto-responsiveness.

D Barry-Macaulay, A Bouazza, B Wang, RM Singh (2015)Evaluation of soil thermal conductivity models, In: Canadian Geotechnical Journal52(11)pp. 1892-1900

Numerous models have been developed to predict the thermal conductivity of soils at a range of different densities and moisture contents. This paper evaluates four thermal conductivity models, developed by various researchers, by comparing their performance against experimental results obtained on 27 different soils prepared at a range of saturation levels and densities. The results demonstrate that, in general, all four models show good agreement between experimental thermal conductivity and modelled thermal conductivity. The only significant shortfall is observed in low-saturated sands when using two of the models. A detailed analysis of the empirical soil parameters used in three of the recent models is presented. It shows that the accuracy of the three models can be improved by modifying the empirical soil parameters to fit the experimental data.

MA Rouf, A Bouazza, RM Singh, WP Gates, RK Rowe (2015)Water vapour adsorption and desorption in GCLs, In: Geosynthetics International23(2)pp. 86-99 ICE Publishing

Super-saturated salt solutions are used to control relative humidity (RH) and to infer the hydration (water uptake and loss) behaviour of three needle-punched geosynthetic clay liners (GCLs) with respect to time under conditions of both free swell and 20 kPa applied stress. It is shown that RH and applied stress play a key role in the hydration behaviour with time when GCL specimens were in equilibrium with water vapour. It was also observed that water uptake and loss was affected by the bentonite form (powdered or granular) and mineralogy of the bentonite. However, the effect of GCL structure (i.e. difference in geotextiles and bonding of needle-punched fibres to the carrier geotextile) on their hydration behaviour for GCLs with similar form of bentonite was not significant for RH ≤ 97.7%. The effect of GCL structure became more apparent at 100% RH (for all GCLs). The results presented in this study can be used to better assess the hydration of GCLs in field applications such as waste containment liners and cover systems at different RH and overburden stress conditions.

AS Acikel, RM Singh, A Bouazza, WP Gates, RK Rowe (2015)Applicability and accuracy of the initially dry and initially wet contact filter paper tests for matric suction measurement of geosynthetic clay liners, In: Geotechnique: international journal of soil mechanics65(9)pp. 780-787 ICE Publishing

An initially wet contact filter paper test (IW-CFPT) and an initially dry contact filter paper test (ID-CFPT) were used to examine the wetting paths of geosynthetic clay liners, including non-contact filter paper tests for comparative purposes. The CFPTs were applied to both geosynthetic clay liner faces to examine the effect of geotextile type on capillary contact. The non-woven geotextile face was found to be more likely to cause capillary breaks than the woven geotextile face. Both IW- and ID-CFPTs were found to be applicable to geosynthetic clay liners within their accurate upper matric suction measurement limits of 146 kPa and 66 kPa, respectively.

Poonam Shekhawat, Gunwant Sharma, Rao Martand Singh (2019)Strength behavior of alkaline activated eggshell powder and flyash geopolymer cured at ambient temperature, In: Construction & building materials223pp. 1112-1122 Elsevier Ltd

•Geopolymerization of eggshell powder and flyash at ambient temperature.•Potential application in sustainable sub-base/subgrade construction.•Mixture of sodium silicate and sodium hydroxide was used as alkaline activator.•10 M sodium hydroxide concentration was used in the alkaline activator solution.•Evaluation of strength with respect to activator ratio and precursor ratio. The eggshell powder (ESP) rich in calcium content is a poultry waste product, generated from grinding waste eggshells. Flyash (FA) is an industrial waste product, generated from the combustion of coal in power plants. Currently, disposal of these kinds of waste products is a global concern. Utilization of waste products as a sustainable construction material can solve many problems related to disposal. The current study aims to determine the possibility of utilization of calcium-rich eggshell powder and industrial waste flyash through geopolymerization, to give a sustainable construction material. Mixtures of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) with fixed 10 M concentration were used as an alkaline activator solution. Modified Proctor test, unconfined compressive strength, and split tensile strength test were performed to analyze the behavior of mechanical strength. Three precursor ratios (ESP:FA) – 30:70, 50:50, and 70:30 and three activator ratios (Na2SiO3/NaOH) – 0.5, 1, and 2 were adopted. The geopolymer composites were cured at ambient temperature (25 ± 2 °C) for 7 days, 28 days, and 56 days to assess the long term strength development. Geopolymer composite 50ESP:50FA with activator ratio 2 was found optimum for unconfined compressive strength and split tensile strength. The optimum composites found in the research have the potential to be employed in sub-base/subgrade application as a sustainable construction material made from waste-by-product.

Poonam Shekhawat, Gunwant Sharma, Rao Martand Singh (2020)Potential Application of Heat Cured Eggshell Powder and Flyash-Based Geopolymer in Pavement Construction, In: International journal of geosynthetics and ground engineering6(2) Springer Nature

In this research, the application of eggshell powder (ESP) and flyash (FA) as calcium oxide and alumino-siliceous precursors to produce a feasible geopolymer for pavement construction was studied. Effect of heat curing on long-term mechanical strength development of the geopolymer was also evaluated. The ESP is a waste-by-product produced from crushing waste eggshells, whilst FA is a waste-by-product generated from the coal-fired electricity production plant. Geopolymer composites were produced using three activator ratios Na2SiO3/NaOH -0.5, 1.0, and 2.0 with a fixed 10 M concentration of NaOH. The curing process was done at 50 degrees C and 80 degrees C temperatures for 7 days, 28 days, and 56 days. The optimum activator content (OAC) providing the maximum dry unit weight (MDU) was found to increase with an increment in activator ratio and FA replacement ratio. Na2SiO3/NaOH-2.0 was found as an optimum activator ratio providing the highest unconfined compressive strength (UCS) and the highest split tensile strength (STS). Similarly, optimum precursor ratio providing the highest UCS followed by highest STS was found as ESP50:FA(50). Microstructural analysis showed that cementitious products were formed for the ESP-FA geopolymer at the optimum activator ratio and heat conditions.

Abubakar Kawuwa Sani, Rao Martand Singh, Cristina de Hollanda Cavalcanti Tsuha, Ignazio Cavarretta (2019)Pipe–pipe thermal interaction in a geothermal energy pile, In: Geothermics81pp. 209-223 Elsevier Ltd

•The heat transfer between inlet and outlet leg of energy loops reach steady state in a duration of about 3–5 days.•Number of installed loops is the major factor contributing to heat flow between energy loops in rotary bored energy piles.•Similarly, loops location and thermal conductivity also influences the heat flow between the energy loops installed.•Higher magnitude of thermal interaction occurs in contiguous flight auger (CFA) piles than in rotary bored piles.•The central steel bar used for installing the energy loops in CFA piles contributes towards pipe-pipe thermal interaction. The use of energy loop(s), fitted into the structural foundation piles, also known as geothermal energy piles (GEPs) is on the rise. This dualizes the role of the piles in meeting the structural performance and the thermal comfort demand of the overlying structure. Heat carrier fluid (HCF) is circulated through the loops, to extract or reject heat energy into the ground, during the space heating or cooling operation. However, this results in thermal interaction between the inlet and outlet leg of the loop. This paper presents a numerical study to investigate the pipe–pipe thermal interaction between the inlet and outlet loop–legs. It was found that factors such as the number of loops, pipe location, soil and concrete thermal conductivity have a significant influence on the magnitude of thermal interaction between inlet and outlet pipes. Similarly, it was found that the central steel bar, used in contiguous flight auger (CFA) piles, contributes towards higher thermal interaction.

A. S. Acikel, W. P. Gates, R. M. Singh, A. Bouazza, D. G. Fredlund, R. K. Rowe (2018)Time-dependent unsaturated behaviour of geosynthetic clay liners, In: Canadian geotechnical journal55(12)pp. 1824-1836 CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS

Three different chilled-mirror hygrometer test procedures were developed to investigate the time-dependent unsaturated behaviour of powdered and granular bentonite based needle-punched geosynthetic clay liners (GCLs) on both the wetting and drying paths of the water retention curve (WRC). The CCL structure and bentonite forms governed the effect of measurement time and duration as well as the time-dependent suction changes of the bentonite component at a constant gravimetric water content. A conceptual model is proposed to explain the observed time-dependent unsaturated behaviour of the GCLs. The model suggests that the cross-over points on WRCs correspond to the point where bentonite crystallite separation is maximized within the crystalline swelling regime of smectite, forming a four-layer hydrate state where smectite interlayer spaces are filled with water. At gravimetric water contents below this point, the interlayer space dominated the suction, while at higher water contents, mesopores and macropores played increasingly important roles in determining the suction. The results reported herein provide further proof that the unsaturated behaviour of GCLs is largely controlled by the bentonite component.

FA Al-Otaibi, FM Wegian, AA Alnaki, SKH Almutairi, R Singh (2012)Effect of bitumen addition on the long-term permeability of sabkha soil, In: Kuwait Journal of Science and Engineering39(2(B))pp. 131-148

This study investigates the effect of bitumen addition on the long-term permeability of bitumen mixed sabkha soil. Results will be used to evaluate the effectiveness of using the bitumen mixed sabkha soil as hydraulic barriers to leachate percolation. Eight percent bitumen (by dry weight of sabkha) was selected as a mixing percentage based on density results obtained from modified Proctor tests carried out on sabkha soil samples mixed with different bitumen contents. Long-term permeability studies using distilled water were carried out on undisturbed, natural compacted and 8% bitumen mixed sabkha soil samples. The results displayed significant reduction in the initial and long term permeability values of the 8% bitumen mixed sabkha, as compared to the natural compacted sabkha soil. The reduced permeability values of the 8% bitumen sabkha soil are still higher than the recommended value for soil liners. The results also clearly show that sabkha soil compaction, which is the general practice for liners preparation in Kuwait, is not an effective process.

D Barry-Macaulay, A Bouazza, RM Singh, B Wang (2014)Thermal properties of Victorian soil and rock, In: Australian Geomechanics Journal49(2)pp. 31-44 Australian Geomechanics Society
B Wang, A Bouazza, D Barry-Macaulay, RM Singh, M Webster, C Haberfield, G Chapman, S Baycan (2012)Field and Laboratory Investigation of a Heat Exchanger Pile, In: Proceedings of GeoCongress 2012: State of the Art and Practice in Geotechnical Engineeringpp. 4396-4405

Incorporation of heat exchangers into pile foundations is a relatively novel sustainable technology for the intermittent storage of energy in soils. Energy can be utilised in this way for space heating and cooling of buildings by means of suitable systems integrated into buildings. This paper relates to an ongoing study on the impact of coupled thermo-mechanical loads on heat exchanger pile foundations. This study evaluates the performance of a laboratory scale energy pile under different vertical stress levels, temperature gradients and heat transfer modes and presents the full-scale in situ energy pile setup equipped with ground loops for heating/cooling and multi-level Osterberg cells for static load testing.

A Bouazza, RM Singh, B Wang, D Barry-Macaulay, C Haberfield, G Chapman, S Baycan, Y Carden (2011)Harnessing on site renewable energy through pile foundations, In: Australian Geomechanics Journal46(4)pp. 79-90

Incorporation of heat exchangers into pile foundations is a relatively novel sustainable technology for the intermittent storage of energy in soils with a view of utilising it for space heating and cooling of buildings by means of suitable systems integrated into buildings. This innovative technology can provide not only substantial long-term cost savings in relation to conventional energy systems but also can make an important contribution to environmental protection by reducing fossil energy use and minimising the carbon footprint of built structures. This paper reports on an ongoing project on heat exchanger pile foundations taking place at Monash University. It discusses the basic concept of an energy pile and governing design parameters such as thermo-mechanical loading and soil thermal properties and presents the field test set up currently running.

Rokas Valancius, Jurgita Cerneckiene, Rao Martand Singh (2018)Review of Combined Solar Thermal and Heat Pump Systems Installations in Lithuanian Hospitals, In: Proceedings of EuroSun 2018pp. 1-5 International Solar Energy Society (ISES)

One of the major part of energy demand of a building goes to heating and hot water in countries with a cold climate. It is now clearly recognised that modernization of public buildings must be a mix of measures and not only cover the renovation of building components (e.g. roof, walls, windows etc.), but also HVAC systems and heating sources. Aim of any renovation of a public building is to improve the physical aesthetic, the microclimate in the building and reduce primary energy demands. Seventeen projects with solar thermal systems and heat pumps were implemented in Lithuanian hospital buildings by using Swiss and Lithuanian state funding in 2016. This paper presents the cases and monitoring data of three different integrated solar thermal and heat pump systems in Lithuanian hospitals and prospect of solar thermal and heat pump systems in relation to traditional energy prices, technical barriers and government policy as well as potential of these systems.

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