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Mine tailings have shown viability as the fine–grained layer in a capillary barrier structure for controlling acid mine drainage in a circular economy. Their saturated hydraulic conductivities (ksat) under wetting–drying cycles and freeze–thaw cycles remain unexplored. In this study, modified tailings with a weight ratio of 95:5 (tailings/hydrodesulfurization (HDS) clay from waste–water treatment) and an initial water content of 12% were used. The ksat of specimens was measured after up to 15 wetting–drying cycles, each lasting 24 h, with a drying temperature of 105 °C. The ksat for wetting–drying cycles decreased from 3.9 × 10−6 m/s to 9.5 × 10−7 m/s in the first three cycles and then stabilized in the subsequent wetting–drying cycles (i.e., 5.7 × 10−7 m/s–6.3 × 10−7 m/s). Increased fine particles due to particle breakage are the primary mechanism for the ksat trend. In addition, the migration of fines and their preferential deposition near the pore throat area may also promote this decreasing trend through the shrinking and potentially clogging–up of pore throats. This could be explained by the movement of the meniscus, increased salinity, and, subsequently, the shrinkage of the electrical diffuse layer during the drying cycle. Similar specimens were tested to measure ksat under up to 15 freeze–thaw cycles with temperatures circling between −20 °C and 20 °C at 12 h intervals. Compared to the untreated specimen (i.e., 3.8 × 10−6 m/s), the ksat after three freeze–thaw cycles decreased by 77.6% (i.e., 8.5 × 10−7 m/s) and then remained almost unchanged (i.e., 5.6 × 10−7 m/s–8.9 × 10−7 m/s) in subsequent freeze–thaw cycles. The increased fine grain content (i.e., 3.1%) can be used to explain the decreased ksat trend. Moreover, the migration of fines toward the pore throat area, driven by the advancing and receding of ice lens fronts and subsequent deposition at the pore throat, may also contribute to this trend. © 2024 by the authors.

Root-associated bacteria play a vital role in the soil ecosystem and plant productivity. Previous studies have reported the decline of bacterial community and rhizosphere soil quality in the cultivation of some medicinal plants (i.e., Pseudostellaria heterophylla). Phosphorus (P)-modified biochar has the potential to improve soil health and quality. However, its influence on the bacterial community and diversity in the rhizosphere of medicinal plants is not well understood. Therefore, this study aims to investigate the effects of P-modified biochar on the bacterial community and diversity in the rhizosphere of P. heterophylla. Soil samples were collected from the rhizosphere of 4-month P. heterophylla under control (no biochar), 3% unmodified and 3% P-modified biochar treatments, respectively. Compared with control and unmodified biochar treatment, P-modified biochar significantly increased the relative abundance of plant-beneficial bacteria (P < 0.05), particularly Firmicutes, Nitrospirae and Acidobacteria. The relative abundance of Bacillus, belonging to Firmicutes, was dramatically raised from 0.032% in control group to 1.723% in P-modified biochar-treated group (P < 0.05). These results indicate the potential enhancement of soil quality for the growth of medicinal plants. The application of biochar significantly increased bacterial richness and bacterial diversity (P < 0.05). P modification of biochar did not have significant effects on soil bacterial richness (P > 0.05), while it reduced Shannon and increased Simpson diversity index of soil bacterial communities significantly (P < 0.05). It indicates a decrease in bacterial diversity. This research provides a new perspective for understanding the role of P-modified biochar in the rhizosphere ecosystem. © 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

Carbon emissions from landfill construction and management have become a global concern. Life cycle analysis (LCA) has been widely used to assess the environmental impacts of engineered infrastructures over their lifetimes. LCA has also been applied to landfill leachate and gas management, but rarely to landfill final cover systems. This paper reports the results of an LCA of the following landfill final cover systems: compacted clay cover, geomembrane cover, cover with capillary effects (CCBE), dual capillary barrier cover, three-layer landfill cover system using natural soils, three-layer cover using recycled concrete aggregate (RCA) and biochar-amended three-layer landfill cover system using RCA. The LCA assessment of landfill cover considers the cost, carbon emissions and carbon sequestration during the production, construction and operation phases. The effects of landfill cover on global warming, freshwater eutrophication, terrestrial ecotoxicity, freshwater ecotoxicity, marine ecotoxicity and fossil resource scarcity are also evaluated. In addition, the sensitivities of cost and carbon emission to the use of electric-powered machines and transportation distance are analysed. It is revealed that the three-layer cover system using RCA and biochar has the lowest unit cost and carbon emission of all of the covers, up to 88 % and 66 % lower, respectively, than those of the other six covers. In addition, this cover system has the highest carbon sequestration rate, with a value of 47.9 kg CO2/(y·m2), four times higher than that of the compacted clay cover. Finally, this sustainable cover mitigates global warming and reduces adverse environmental impacts by up to 82 %. Therefore, the biochar amended three-layer cover system using RCA without geomembrane offers the greatest economic benefits, performs effectively in terms of the pursuit of carbon neutrality and promotes sustainable development. © 2023 Elsevier B.V.

Climate change has resulted in increasing attention being paid to the effects of temperature and humidity on vegetated soil. However, existing constitutive models rarely investigate the thermo-mechanical behaviour, such as accumulation of plastic strain under non-isothermal conditions, of unsaturated vegetated soil. To address this issue, this study develops a comprehensive constitutive model by adopting the state-dependent dilatancy in conjugation with loading, memory, and bounding surfaces. Moreover, root-induced hardening due to pore occupancy and internal bonding is modelled with dependence on root volume ratio. The performance of this newly developed constitutive model is then evaluated using previous laboratory element tests. Comparisons between the computed and measured results reveal that the model is capable of capturing variations in soil state at a range of temperatures, suctions, and root volume ratios. The shearing behaviour of vegetated soil, especially its volumetric response, is well predicted by the model, as confirmed by comparing with triaxial compression test results. Moreover, the model predicts that the accumulated volumetric strain of unsaturated vegetated soil (0.2%) is significantly less than saturated bare soil (1.1%) after 4 thermal cycles. These computed results imply vegetation can mitigate the effects of climate change on soil through both transpiration-induced suction and mechanical reinforcement.

Material properties, crucial design parameters in landfill cover systems, can exhibit spatial variability due to non-uniform particle size and uneven compaction, affecting cover performance. Additionally, cover thickness, another key design parameter, can induce stress variation and influence soil-water retention capability. Previous designs always ignored these uncertainties and stress effects, potentially leading to unreasonable design schemes. This study aims to provide design recommendations for a three-layer landfill cover system under heavy rainfall, considering these factors simultaneously by the random finite element method (RFEM). The stress effects are captured using a stress-dependent soil-water retention curve (SDSWRC) and the hysteresis in the SDSWRC is considered in probabilistic analyses. For practical applications, uncertainties in two easily controllable particle size parameters, D10 and D60, are depicted by copula-based cross-correlated random fields. Based on empirical equations, the spatial variability of SDSWRC and water permeability function (WPF) can be further characterised by D10 and D60 random fields. It is found that considering SDSWRC and its spatial variability (e.g., shape) can overestimate percolation by at least 1.7 times compared to deterministic analysis using SWRC. The spatial variability of SDSWRC shape has a more significant impact than spatially variable saturated water permeability on cover system performance. Among candidate copulas, the CClayton copula (survival copula of Clayton copula) yields the most conservative results due to its upper tail dependence. The particle size and thickness of the bottom layer influence the cover system performance more than the upper two layers. A bottom layer with D10

Field monitoring was conducted to investigate and quantify the long-term effects of peanut shell biochar on soil-grass interaction over three years. Three 10 m × 5 m grassed plots were constructed in completely decomposed granitic soil. Two of them were amended, respectively, with 5% and 10% biochar contents (m3/m3) for grass growth, while the third was without biochar amendment. During the three-year monitoring, plant characteristics, saturated water permeability (ks) of grassed soil and soil suction were measured. The monitored results show that the grass leaf area index (LAI) and root length density (RLD) with biochar amendment were improved by 38% and 200%, respectively. In the grassed plot without biochar, a threshold RLD existed with a value of 1.7 cm/cm3, beyond which ks raised pronouncedly. The threshold RLD increased by 52% when biochar content increased from 0% to 10%. This implies that biochar may restrict the increase in ks of grassed soil due to the rise in the threshold RLD. The presence of biochar and grass can retain over 100% higher suction after heavy rainfalls, while 54% lower peak suction under evapotranspiration (ET) compared with the non-amended plot. Biochar can alleviate the negative effects on hydraulic properties caused by plant growth and reduce ET-induced excessive water loss. A 5% peanut shell biochar content is recommended for the long-term management of vegetated earthen infrastructures. © 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences

The increase in pore-water pressure (PWP) in slopes due to extreme rainfall is one of the major triggering factors for landslides. In recent years, machine learning (ML) techniques have been proposed to predict PWP response under heavy rainfall for slope stability analysis. However, most of these methods neglect the spatiotemporal nature of the problem by treating the PWP dataset as a univariate time-series problem. As such, the trained model remains valid for the given sensor and fails to predict the response when used for other locations. In this paper, a novel multivariate long short-term memory (M-LSTM) is proposed to predict the PWP response by simultaneously using the spatial and temporal PWP data from multiple measurement locations. The choice of optimal measurement locations for model training is made using the principal component analysis (PCA) and silhouette value analysis. The performance of the proposed model is evaluated using five different performance indicators named (i) mean absolute error (MAE), (ii) mean square error (MSE), (iii) root mean square error (RMSE), (iv) coefficient of determination (R2), and (v) Pearson correlation coefficient (PCC). The results obtained with M-LSTM are compared with the predictions from the univariate LSTM algorithm. The comparison shows that the univariate LSTM model is only valid for the location used for training and cannot be applied to other locations, implying the loss of generality of the model. In contrast, the proposed M-LSTM is not hamstrung by the foregoing issue and accurately predicts the PWP response for non-training sensor locations, which can also incorporate the spatial and temporal variation within the data. © 2023 Elsevier B.V.

Biochar has been used as a sustainable amendment to mitigate environmental risks, improve plant growth and soil properties. This study conducted laboratory column tests to investigate the effects of plant-biochar interactions on shrub growth, hydraulic properties and nutrient contents of recycled concrete aggregates (RCAs). In total, three test conditions, namely, vegetated RCA without biochar (R), with 5 % biochar (R5) and 10 % biochar (R10) were subject to drying. With biochar application, total N, P and K of RCA increased by >100 %, 200 % and 31 %, respectively, while pH reduced to 8.3. With shrub growth, the lowest RCA pH was reduced to 7.8. The leaf area index (LAI) of shrub increased by 51 % due to biochar amendment, while the differences in shoot height were insignificant. The water retention capacity of RCA was enhanced by improving the saturated water content and air-entry value by 27 % and 100 %. The slope of the soil suction-LAI correlation for biochar amend cases was 1.6 times lower than R. This indicates that biochar may limit the increase of matric suction and prevent excessive water loss during drying. However, the differences between R5 and R10 were not significant. Therefore, 5 % biochar amendment is highly suggested as it can substantially improve plant growth and soil hydraulic properties during drying. © 2023 Elsevier B.V.

It is clear that the efficient use of recycled construction waste materials can reduce waste generation and preserve natural resources. Although the use of recycled concrete aggregates (RCA) as a CCBE subjected to small intensity rainfall has been reported, no physical model test data and numerical simulation to investigate the use of RCA as a landfill cover subjected to high intensity of rainfall under humid climatic conditions. In this study, one-dimensional (1D) soil column and two-dimensional (2D) flume model tests simulating humid climatic conditions were carried out to evaluate the hydrological performance of a sustainable three-layer landfill cover system using recycled concrete aggregates (RCA) but without a geomembrane. This three-layer system consists of a layer of fine-grained and a layer of coarse-grained recycled aggregates (i.e., FRC and CRC, respectively) overlying the bottom fine-grained completely decomposed volcanic soil (CDV). The effects of vegetation on the three-layer cover system were also considered in the 1D column tests. In addition, numerical simulations were carried out to back analyse the model tests by using the modified Darcy–Richards equation in COMSOL Multiphysics to verify test results and to reveal the water flow mechanisms. Consistent results were obtained between the measured data and numerical predications. Even after the simulated extreme rainfall of Hong Kong with a return period more than 1,000-year, a higher matric suction was well-retained in vegetated cover system than that in bare cover due to evapotranspiration of plants. As revealed in the 2D flume model test and numerical simulation, the middle CRC layer can switch from a capillary barrier layer to a drainage layer to reduce infiltration into the bottom layer even under the heavy rainfall. Most of infiltrated rainfall water (i.e., more than 95% of total precipitation) can be diverted as surface runoff and lateral drainage in the two upper RCA layers. The rest of infilt

Previous studies have demonstrated the effectiveness of a novel three-layer landfill cover system constructed with recycled concrete aggregates (RCAs) without geomembrane in both laboratory and field. However, no systematic investigation has been carried out to optimize the combination of the particle sizes for fine-grained RCAs (FRC) and coarse-grained RCAs (CRC) that can be used for the three-layer landfill cover system. The aim of this paper is to assist engineers in designing the three-layer landfill cover system under a rainfall of 100-year return period in humid climate conditions using an easily controlled soil parameter D10 of RCAs. The numerical study reveals that when D10 of FRC increases from 0.05 mm to 0.16 mm, its saturated permeability increases by 10 times. As a result, a larger amount of rainwater infiltrates into the cover system, causing a higher lateral diversion in both the top FRC and middle CRC layers. No further changes in the lateral diversion are observed when the D10 value of FRC is larger than 0.16 mm. Both the particle sizes of FRC and CRC layers are shown to have a minor influence on the percolation under the extreme rainfall event. This implies that the selection of particle sizes for the FRC and CRC layers can be based on the availability of materials. Although it is well known that the bottom layer of the cover system should be constructed with very fine-grained soils if possible, this study provides an upper limit to the particle size that can be used in the bottom layer (D10 not larger than 0.02 mm). With this limit, the three-layer system can still minimize the water percolation to meet the design criterion (30 mm/yr) even under a 100-year return period of rainfall in humid climates.

Construction wastes such as recycled concrete have been widely reused in geotechnical engineering to reduce environmental pollution and preserve natural resources. In this study, a one-dimensional (1D) soil column test was carried out to evaluate the hydrological performance of a three-layer landfill cover system using recycled concrete aggregates (RCA) under humid climatic conditions. This three-layer system consists of a layer of fine-grained and a layer of coarse-grained recycled aggregates (i.e. FRC and CRC) overlying the bottom silt refuse soil. Numerical simulations were conducted to analyse the model test and investigate the effects of the bottom layer and climate conditions on the performance of the three-layer landfill cover system. Consistent results were obtained between the measured data and numerical predictions. The matric suctions in the vegetated cover were nearly 80% higher than the bare cover after drying for 14 days from a nearly saturated condition. Even after the simulated extreme rainfall of Hong Kong with a return period of 100 years, a higher suction was also well-retained in vegetated cover. This was due to the initial high suction induced by evapotranspiration of plants, which led to the infiltration rates into grassed cover being up to 30% lower than the bare one. The results from the numerical parametric analysis suggest a bottom soil layer with an effective particle size (d 10) value of 0.02 mm and 0.2 mm to be used in the three-layer landfill cover system under humid and semi-humid climates, respectively. For semi-arid or even arid regions, a two-layer cover with capillary barrier effects (CCBE) is already sufficient for preventing water percolation as the rainfall in those areas is not heavy. © 2023, Springer-Verlag GmbH Germany, part of Springer Nature.

This paper compares the field performance of non-grassed and grassed three-layer landfill cover systems utilising construction waste but without geomembrane at the Shenzhen Xiaping landfill site under humid climates over a monitoring period of 54 months. The top layer of each cover system was constructed by coarse-grained completely decomposed granite (CDG). The middle and bottom layers were compacted with coarse recycled concrete (CRC) and fine-grained CDG, respectively. Numerical analyses were also carried out. During the 54-month monitoring period, the cumulative rainfall recorded was 9800 mm. Retained pore water pressure in the grassed cover was close to that in the non-grassed cover after the heaviest rainfall recorded in Shenzhen during the monitoring period. The pore water pressure retained in the grassed cover can be higher than that in the non-grassed cover due to the increased saturated water permeability (ks) induced by plant growth over three years. Surface runoff and water storage capacity in the grassed cover was about 5 times and 9% higher than those in the non-grassed cover, respectively. However, the long-term behaviour of the cover system on those two aspects was influenced by the increasing of ks due to the growth of grass root. The middle CRC layer diverted infiltrated water by up to 51% of total rainfall. The measured average annual percolation of the non-grassed and grassed covers was about 23 mm and 21 mm, respectively. The measured data are supported by numerical analyses and they meet the US recommended criterion.

Due to climate change, extreme rainfalls happen more frequently with different patterns. Biochar and plant roots can affect soil water retention curve (SWRC) and hence slope stability. Until now, no available SWRC model considers soil–plant-biochar interaction, which can also be used for slope stability analysis under extreme rainfalls with different patterns (i.e., advanced, bimodal, and delayed). This study proposes a new SWRC model for vegetated biochar-amended soil by considering the influence of soil–plant-biochar interaction on the void ratio and pore structure. A series of numerical analyses were conducted to investigate the significance of new SWRC model on slope stability under extreme rainfall patterns. Good agreements between laboratory measurements and the new SWRC model predictions were obtained. With an increase of biochar content from 0 to 10%, the number of soil micropores increased by 22%, which improved root volume ratio (Rv) by 130% and hence air entry value (AEV) of vegetated soil by 50%. Based on numerical analysis, the factor of safety (FOS) for vegetated slope under advanced and bimodal rainfall patterns was up to 53% lower than that under the delayed one during rainfall. The rainfall influence depth and FOS of vegetated slope without biochar was nearly 100% deeper and 60% lower than that with biochar, respectively. The lowest FOS was caused by advanced rainfall pattern, which is therefore suggested for slope design. The application of 10% biochar can better stabilize shallow slopes due to its substantial effects on plant root, soil pore structure, and SWRC.

A comprehensive study on dynamic characteristics of GaN MISHEMT with a 5nm-thick in-situ SiNx dielectric is presented. Effects of both negative and positive gate bias on threshold voltage instability were investigated and miniature threshold voltage shift was acquired. The slight shift was considered to be associated with the traps at the insulator/AlGaN interface and in the dielectric layer itself. Pulsed I-V measurements with various gate quiescent biases presented small current collapse (11%) and low enhancement of dynamic Ron for zero quiescent drain bias. When drain quiescent bias was strengthened to 20V, an increased dynamic Ron/static Ron ratio was identified but still limited to a low value of 1.24. The conduction reduction was in a good agreement with measurement results from drain current transient spectroscopy and possibly originates from trap states existed in the access region. Additional current collapse was observed in hard switching-on operation, resulted from energetic hot electrons accelerated by drain-source electrical field during the off-to-on step. The measurement results showed stabilized threshold voltage, a low dynamic Ron/static Ron ratio, and suppressed current collapse via employing a 5-nm thin in-situ SiNx layer in GaN MISHEMT, enabling it a promising solution for high-efficiency power switching applications. © 2013 IEEE.

The spatial variability is an inherent characteristic of soils. In addition to isotropic and transversely anisotropic soils, rotated anisotropic soils can also be observed in nature owing to deposition and weathering. Recent studies revealed that the spatially variable soil strength parameters can significantly affect rotated anisotropically deposited soil slope stability. However, the influence of spatial variability of saturated water permeability (ks) on this type of slope stability has been not fully understood, especially for the three-dimensional (3D) slope analysis. This paper aims to investigate unsaturated soil slope reliability with 3D ks rotated anisotropy random fields under rainfall infiltration. Due to the low efficiency of the covariance matric decomposition method (CMD) in simulating large-scale 3D rotated anisotropy random fields, a modified CMD method is proposed to save the computational cost. Moreover, comparisons between 2D and 3D random finite element analyses are also discussed. The results indicate the modified CMD method can markedly improve computational efficiency by more than 3.3 times compared with the CMD method. Only applying variations of pore water pressure (PWP) of a section or groundwater table (GWT) cannot sufficiently account for the uncertainty of slope stability. The cross-dip slope, where the dip direction of the slope is perpendicular to the dip direction of strata, has a larger reliability index (1.3−3.0 times) than the dip slope and reverse slope at the same soil bedding plane orientation. The most unfavorable soil bedding plane orientation for the cross-dip slope and the dip/reverse slope is 0° (horizontally deposited) and 30° (slightly larger than slope angle), respectively. It is attributed to the relatively low ks along these two orientations being more likely to form the aquiclude, affecting overall variations of PWP, leading to a larger standard deviation of the factor of safety and a lower reliability index. Furtherm

In natural slopes, apart from isotropic and transversely anisotropic soil fabric, rotated anisotropic soil fabric is also commonly observed due to deposition and weathering. Previous studies mainly focused on the effects of copula selection on transversely anisotropic soil slope stability. However, the influence of copula selection on rotated anisotropically deposited soil slope stability is still not clear. This study develops a new method to generate copula-based rotated anisotropy random fields for characterizing the spatial variability of soil properties. The index associated with the failure probability and consequence is employed to assess the risk of failure of two cohesive-frictional slopes in spatially variable soils (i.e., a single- and a two-layer slope). The results reveal that the commonly-used Gaussian copula may underestimate the risk of failure of both the single- and two-layer slopes at any soil deposition orientation. The risk of slope failure calculated by four candidate copulas shows a great difference. This difference is mainly affected by slope failure probability. For a single-layer cohesive-frictional slope, the slope with the highest risk of failure occurs at a rotational angle β = 150°. The corresponding soil deposition orientation (30°) is slightly smaller than the slope inclination (45°), independent of copula types. Additionally, when a slope fails, it can be found that the Gaussian copula corresponds to the largest sliding volume for some combination anisotropy cases, which is in reverse to the failure probability. Therefore, for a cohesive-frictional slope, it is suggested to consider both failure probability and failure consequence to assess the potential slope failure risk. Furthermore, the No.16 copula can give a more conservative risk assessment when dependence structure between cohesion and friction angle is uncertain. © 2021 Elsevier Ltd

Nonwoven-geotextile is used to construct soil-geotextile capillary barrier for minimizing water infiltration. However, the sand-geotextile capillary barrier breakthrough can occur due to the low water retention ability and the high saturated permeability coefficient of sand. To address this, enzyme induced carbonate precipitation (EICP) technology was applied to the overlying sand layer to improve its hydraulic properties and enhance the sand-geotextile capillary barrier. The precipitated calcium carbonate has the potential to enhance the capillary barrier effect by coating soil particles and filling the soil macro-pores. To investigate the effect of EICP treatment on the sand-geotextile capillary barrier, three column tests were conducted, including one untreated sand-geotextile column and two sand-geotextile columns treated with 0.5 and 1 mol/L urea-calcium chloride solutions and soybean urease liquid, respectively. Transient seepage analysis was carried out based on the column tests to calibrate the hydraulic parameters. A numerical parametric analysis was conducted to assess the effect of EICP-enhancement on the hydraulic behavior and slope stability of a sand-geotextile capillary barrier retaining wall during exposure to rainfall with a 100-year return period. The results of the column infiltration tests show that the occurrence of breakthrough in the sand-geotextile capillary barrier is significantly delayed with increasing concentration of the urea-calcium chloride solutions. The enhanced capillary barrier effect is attributed to the increased water retention ability and reduced saturated permeability coefficient. The results of the parametric analysis show that the matric suction within the backfill is maintained and the factor of safety remains almost unchanged due to the EICP-enhanced sand-geotextile capillary barrier effect.

The recycling and reuse of construction waste in landfill covers help reduce environmental pollution and promote sustainability. Further enhancement of the performance of the environmentally friendly landfill covers can be made by using vegetation as it is a low-cost, ecologically pleasant solution. Most related studies of vegetation were carried out in single-layer uniform soil while plant effects on water infiltration in layered soil such as a three-layer landfill cover system remain unclear. This keynote presents an integrated research approach combining laboratory one-dimensional tests as well as a 4-year full-scale field trial located in humid climates to explore the hydrological effects of plants on the performance of a novel three-layer landfill cover system using recycled concrete but without the installation of a geomembrane. Matric suction induced by plants was preserved to a greater extent under a novel vegetated three-layer landfill cover than under a bare cover even after an extreme rainfall event with a return period of greater than 1,000 years in humid regions like Hong Kong. During the 4-year field trial, the measured maximum annual percolation was 26 mm in the three-layer bare cover system, which was less than the US EPA-recommended 30 mm. Due to the presence of grass roots, the measured amount of annual percolation in the vegetated landfill cover was further reduced by up to 22%. Both the laboratory tests and field trial demonstrated that the vegetated three-layer landfill cover system using recycled concrete even without a geomembrane can effectively reduce percolation in humid climates. © 2021, Indian Geotechnical Society.