Compacted Lateritic Soil Research Articles

Diffusion of Municipal Waste Pollutants in Electrokinetic Lead Remediated Compacted Lateritic Soil

Diffusion of Municipal Waste Pollutants in Electrokinetic Lead Remediated Compacted Lateritic Soil

Characterization of water retention behavior of cracked compacted lateritic soil exposed to wet-dry cycles

Characterization of water retention behavior of cracked compacted lateritic soil exposed to wet-dry cycles

Analysis of the unsaturated behaviour of compacted lateritic fine-grained tropical soils for use in transport infrastructure

This article evaluates the unsaturated behaviour of fine-grained tropical soils for application in transport infrastructure. An extensive experimental campaign was conducted covering physical, chemical, mineralogical and mechanical tests. Simulations of a pavement structure were carried out applying the new Brazilian pavement design method (MeDiNa). The results showed highly weathered soils, with classification ranging from A-4 to A-7-6 (TRB), SC, SM, ML and CL (USCS), but of the same class MCT (LA’ – lateritic sandy soils), bimodal SWCC and excellent resilient modulus (394–680 MPa). The compaction directly influenced its unsaturated behaviour. The soils were proved to be suitable for use in the pavement with high traffic, thus enabiling the exploitation of the local materials and reducing costs with transport and acquiring scarce granular materials. Polynomial and linear regression equations were proposed to predict the MR as a function of confining and deviation stresses acting in the subgrade and sub-base layers.

Effect of Polypropylene Fibers on the Shear Strength–Dilation Behavior of Compacted Lateritic Soils

The stress–dilatancy relationship for fiber-reinforced soils has been the focus of recent studies. This relationship can be used as a foundation for the development of constitutive models for fiber-reinforced soils. The present study aims to investigate the effect of recycled polypropylene fibers on the shear strength–dilation behavior of two lateritic soils using the stress–dilatancy relationship for direct shear tests. Results show that fibers improved the shear strength behavior of the composites, observed by increases in the friction angle. Fibers’ orientation at the sheared interface could be observed. The volumetric change during shearing was altered by the presence of fibers in both soils. Overall, results indicate that the stress–dilatancy relationship is affected by inclusions in the soil mix. Results can be used to implement constitutive modeling for fiber-reinforced soils.

Diffusion study of municipal solid waste contaminants in compacted lateritic soil treated with bacillus coagulans

Diffusion study of municipal solid waste contaminants in compacted lateritic soil treated with bacillus coagulans

Reinforcing effect of recycled polypropylene fibers on a clayey lateritic soil in different compaction degrees

The present research investigates the reinforcing effect of recycled polypropylene (R-PP) fibers on a compacted clayey lateritic soil in different compaction degrees. R-PP fibers of 12 mm length were mixed with the soil in the contents of 0.1 and 0.25% of soil dry weight. Unconfined compression strength tests (UCS), direct shear tests and indirect tensile strength (ITS) tests were conducted. Fibers addition showed no significate alterations in the optimum compaction parameters. The study evidenced increases in UCS, changing the soil behavior from a brittle failure to a ductile failure, while fiber contribution was most effective for 0.25% R-PP fibers content and 95% compaction degree. The use of fibers improved the shear stress-strain behavior of the composites and soils compacted at different degrees of compaction showed similar shear behavior, which is coherent to the soil water retention curves (SWRC) results. Significant increases in the tensile behavior of soil-mixtures for both fiber contents used were observed, and fibers increase was more significate than increase in soil degree of compaction. The stretching of the fibers and fibers orientation at the sheared interface in direct shear tests and the fiber “bridge” effect in ITS tests could be observed.

Desiccation Induced Shrinkage of Compacted Lateritic Soil Treated via Enzymatic Induced Calcium Carbonate Precipitation Technique

Exploring the biological process to enhance the engineering properties of soil have received enormous recognition in recent years. Enzymatic induced calcium carbonate precipitation (EICP) is one of the bio-inspired methods of utilizing free urease to precipitates calcite from urea and calcium ions for bettering the geotechnical properties of poor soils. In this research, the EICP technique was used to improve the volumetric shrinkage strain of compacted soil liner. In this work, the residual soil was treated with various concentrations of cementations ranging from 0.25 to 1.0 M, and the soil was subjected to Atterberg limit tests, compaction test using British standard light (BSL) and reduced British standard light (RBSL) and desiccation drying volumetric shrinkage strain test. The study's findings revealed a remarkable improvement in the liquid limit and plasticity index of the treated residual soils compared to natural soil. It was also found that the volumetric shrinkage strain of the treated soil reduces progressively from 5.24% of natural to 1.49% at 1.0 M cementation solution when the soils were prepared at 0% OMC and BSL compaction effort. Based on the consideration of permissible VSS of less than 4%, the best treatment was obtained at 1.0 M for both BSL and RBSL prepared samples. Similarly, the best compaction plane is found in the treated with 1.0 M cementation solution.

Evaluation of compacted lateritic soil – bacillus coagulans induced calcite precipitate for landfill application using bacterial foraging optimization algorithm

Evaluation of compacted lateritic soil – Bacillus coagulans (B.coagulans) induced calcite precipitate for landfill application was carried out using Bacterial Foraging Optimization Algorithm (BFOA). Experimental results were obtained through laboratory tests. Measured soil factors include; Coefficient of permeability (hydraulic conductivity) as a dependent factor and void ratio, bulk density, B. coagulans suspension, pH, Compactive effort, water content relative to optimum, plasticity index, viscosity of microbes and liquid limit as self-determining (independent) factors. GeneXproTools 5.0 software was used to develop the fitness (objective) function used for Bacterial Foraging Optimization (BFO) to predict hydraulic conductivity of treated lateritic soil with B. coagulans suspension density. The fitness function was then integrated using BFO codes in Matlab 2016 version to predict the minimum hydraulic conductivity for a given set of self-determining factors. The result shows a strong association between the predicted hydraulic conductivity values and the measured hydraulic conductivity values in the laboratory using a regressed line with coefficient of determination R=0.85. It is clear from the optimization results that the hydraulic conductivity values and the self-determining variables have strong correlation. The least hydraulic conductivity value of 2.38×10−11m/s which falls below the permissible regulatory value of 1.0×10−9 m/s for landfill application was achieved at 100 iterations. Based on all the optimization results, it is recommended that lateritic soil-B.coagulans mixtures be compacted with 1.20×10−9 - 2.40×10−9 cells/ml B.coagulans suspension density compacted using Britsh standard heavy (BSH) energy at 15.3 % moisture content for landfill application.

Unsaturated hydraulic conductivity of compacted bio-cemented lateritic soil in municipal solid waste containment application

Most engineering infrastructures, including municipal solid waste containment facilities, are situated in unsaturated zone. The use of chemical additives for soil improvement has been linked to the adverse environmental issues being experienced globally. Research into more sustainable methods of soil improvement has led to the discovery of a novel and innovative method known as microbial induced calcite precipitation (MICP). Lateritic soil was treated with stepped Sporosarcina pasteurii (S. pasteurii) suspension density up to 2.40 x 109 cells/ml at moulding water content (MWC) -2, 0 and +2 % relative to optimum moisture content (OMC) before compaction using Reduced British Standard light (RBSL), British Standard light (BSL), West African Standard (WAS) or Intermediate and British Standard heavy (BSH) energies. Compacted specimens were saturated with cementation reagent in three cycles with 1/3rd pore volume at 6 hours’ interval to induce calcite precipitation at an ambient laboratory temperature of 24±2°C. The soil-water characteristics curves (SWCC) of the specimens were determined using pressure plate extractor over a pressure range of 10-1500 kPa. Unsaturated hydraulic conductivity values were predicted for the S. pasteurii suspension densities considered using Brooks-Corey, van Genuchten as well as Fredlund and Xing curve fitting prediction models. Results show that the unsaturated hydraulic conductivity values of specimens prepared at lower, MWC relative to OMC were generally higher than at higher MWC regardless of compactive efforts and S. pasteurii suspension densities considered. The Brooks-Corey model gave the best predicted unsaturated hydraulic conductivity values which fit the requirements for waste containment facilities over the matric suction range and S. pasteurii suspension densities considered, than the van Genuchten and Fredlund – Xing, when compared with measured values.

A comparative study of soil-water characteristic curves for compacted lateritic soil – bacillus coagulans mixtures

A comparative study of soil-water characteristic curves (SWCCs) for compacted lateritic soil ̶ Bacillus coagulans (B. coagulans) mixtures for municipal solid waste (MSW) application was studied. Soil treatment was performed at approximately about one-third pore volume of the microbes (i.e., B. coagulans) for suspension densities of 0, 1.5×108, 6.0×108, 1.2×109, 1.8×109 and 2.4×109cells/ml, correspondingly. Soil specimens were prepared at optimum moisture content (OMC) of British Standard light (BSL) compaction energy. Cementation reagent was applied on the compacted soil and permitted to penetrate until partial saturation was achieved. A set-up of pressure plate extractor was employed to measure the volumetric water content, θ (VWC) in the laboratory for varying matric suctions with a minimum of 10 kPa up to a maximum of 1,500 kPa. The unsaturated hydraulic conductivity (UHC) and VWC were assessed using Brooks - Corey (BC) and Fredlund - Xing (FX) models. Largely, BC and FX models overrated the VWC. Also, the VWC decreased with higher matric suction for the two models considered and the laboratory measured values. The UHC predicted for matric suctions of 500 and 1,500 kPa initially decreased for B. coagulans suspension density up to 1.2×109 cells/ml for BC and FX models, with the exception of a few cases, but thereafter increased with increase in microbial density. For FX model at 1,500 kPa, UHC values of 2.42×10–9, 2.02×10–9, 9.31×10–10, 8.09×10–10 , 1.29×10–9 and 2.27×10–9m/s were recorded at 0, 1.5×108, 6.0×108, 1.2×109, 1.8×109 and 2.4×109cells/ml, respectively. In the case of BC model, values of 2.26×10–17, 1.41×10–14, 2.2×10–14, 4.6×10–19 , 3.25×10–17 and 2.45×10–14m/s were recorded at 0, 1.5×108, 6.0×108, 1.2×109, 1.8×109 and 2.4×109cells/ml, respectively. Thus, the FX model met the design maximum hydraulic conductivity value of 1 x 10–9 m/s requirement for MSW system when lateritic soil was treated with B. coagulans suspension density of 1.2×109 cells/ml, while the BC model satisfied the requirement for all the microbial densities considered and it is recommended for modelling of UHC of lateritic soil admixed with B. coagulans for MSW containment application.

Reinforcing Effect of Polypropylene Waste Strips on Compacted Lateritic Soils

This study evaluated the strength properties of compacted lateritic soils reinforced with polypropylene (PP) waste strips cut from recycled plastic packing with the goal of promoting sustainability through using local materials for engineering work and reusing waste materials as low-cost reinforcements. Waste PP strips with widths of 15 mm and different lengths were uniformly mixed with clayey sand (SC) and clay (CL) soils with the goal of using these materials as low-cost fiber reinforcements. The impact of different PP strip contents (0.25% to 2.0%) and lengths (10, 15, 20, and 30 mm) on the unconfined compressive strength (UCS) of the soils revealed an optimum combination of PP strip content and length. Statistical analysis showed that PP strip content has a greater effect than the PP strip length on the UCS for both soils. Results led to the definition of an empirical equation to estimate the UCS of strip-reinforced soils. The results from direct shear tests indicate that the SC soil showed an increase in both apparent cohesion and friction angle after reinforcement, while the CL soil only showed an increase in friction angle after reinforcement. California bearing ratio (CBR) tests indicate that the SC soil experienced a 70% increase in CBR after reinforcement, while the CBR of the CL soil was not affected by strip inclusion.

Dynamic Response and Its Frequency Domain Characteristics of Lateritic Soil Subgrade under Traffic Load during Construction

Field tests were carried out on the compacted lateritic soil subgrade of Laibin-Mashan expressway in Guangxi Province to obtain the vertical vibration acceleration and dynamic stress amplitude of each test point under different axle loads and different driving speeds. The distribution law of the dynamic response and its frequency domain characteristics obtained by wavelet analysis emerged. The vibration of the subgrade is clearly aggravated by the increase of speed and load. Specifically, the acceleration of vehicle speed from 20 km/h to 40 km/h has a prominent effect on the vibration of subgrade, and the influence of speed on the vibration of subgrade decreases with subgrade depth. The acceleration has the greatest impact on the vibration energy in the third and fourth frequency bands.

Comparative study on thermal properties of undisturbed and compacted lateritic soils subjected to drying and wetting

Soil thermal properties are essential for investigating the thermal performance of many kinds of underground thermal engineering structure. To investigate the influences of microstructure alteration on soil thermal properties, thermal conductivity, thermal diffusivity and specific heat capacity were measured for both undisturbed and compacted lateritic clay specimens subjected to drying and wetting with the thermal probe method. Results revealed that thermal conductivity and diffusivity of undisturbed specimens were higher than that of compacted specimens. The specific heat capacity of the undisturbed and compacted specimens was roughly the same. For the same volumetric water content, thermal conductivity of specimens produced by drying was higher than that by wetting due to hysteresis effects. Test results from the scanning electron microscope and mercury intrusion porosimetry confirmed that compared with compacted specimens, the undisturbed specimens have a relatively uniform pore system that improves the extent or quality of heat transfer paths through the contact points and water bridges, thus have higher thermal conductivity. The hysteresis effects on soil thermal conductivity can be explained by the ink-bottle effect, effects of pore size distributions induced by shrinkage and swelling, and differences in the volume of entrapped air between drying and wetting.

Reconstruction of a wetting-induced shallow landslide in Shillong, India

The hill slopes of the north eastern region of India often encounters shallow landslide during the rainy season. Forensic study of a failed hill-slope in such areas is useful in improving the understanding of the failure mechanism. An incessant rainfall triggered a shallow landslide in the Umshing Mawkynroh locality of Shillong in North-east India during the rainy season of 2019. In this work, a forensic investigation was carried out by performing a coupled unsteady-state seepage and stability modelling to reconstruct the actual failure surface. The recorded rainfall data, slope geology, and soil hydraulic properties of the compacted laterite soil were used to back-estimate accurately the in situ failure surface. The underlying mechanism responsible for the shallow landslide during the rainfall infiltration was identified from the numerical modelling. The combined effect of wetting front advancement in the initial partial saturation zone and the rise of the perched groundwater table was found to be the mechanism responsible for the failure.

Evaluation of Compacted Laterite Soil Admixed with Cement and Hair Fibres as Road Construction Material

A natural lateritic soil classified as A-5 (4) based on American Association of State Highway and Transportation Officials (AASHTO) soil classification system and ML-CL according to Unified Soil Classification System (USCS), was admixed with ordinary Portland cement and synthetic hair fibres (SHF) was evaluated as road construction material. Soil test specimens were made by admixing lateritic soil with up to 4% cement in 1 % step concentration and up to 12% SHF in step concentration of 2 % by dry weight of the soil and were subjected to British Standard Light (BSL) or Standard Proctor method of compaction, unconfined compressive strength (UCS) and California bearing ratio (CBR) tests. Results indicated a decrease in the values of optimum moisture content (OMC) while no general trend was established for maximum dry density (MDD). The values of UCS and CBR increased as the content of both cement and SHF increased. Analysis of variance (ANOVA) of the results shows some level of statistical significance on some geotechnical properties considered. Regression analysis on the results using Minitab R15 software shows that MDD, OMC, cement and SHF significantly influenced the UCS and CBR values of the stabilized soil with correlation coefficient value (R2) of 82.9 and 83.3% respectively. Based on the results, an optimal blend of 3% cement 9% SHF significantly improved the soil properties and is recommended for improving the geotechnical properties of cement/synthetic hair fibre treated lateritic soil as road construction material.

Interaction of Landfill Leachate with Compacted Lateritic Soil Treated with Bacillus coagulans Using Microbial-Induced Calcite Precipitation Approach

AbstractThe performance of lateritic soil treated with Bacillus coagulans (B. Coagulans) was assessed for use as hydraulic barrier material in municipal solid waste (MSW) containment use. The soil ...

Critical state of compacted lateritic soil and palm kernel shell ash for earth embankments

For most treated soils in compacted form for earth embankments, interest had been limited to the maximum stresses they can sustain before failure. This work studied the stress–strain behaviour of a compacted lateritic soil treated with palm kernel shell ash (PKSA) from 0 to 18% at 3% intervals, with a major focus on the critical-state characteristics (beyond the maximum stresses). The lateritic soil was characterised as A-2-6(0) in the American Association of State Highway and Transportation Officials rating and clayey sand (SC) in the Unified Soil Classification System. The PKSA was found to be pozzolanic. The British Standard light energy level of compaction and drained shear test were carried out on the treated soil. The optimum moisture content increased while the maximum dry density reduced with an increase in PKSA content. The PKSA of 0–18% content by weight of the dry soil improved the strength properties of the lateritic soil by 51·43%. The critical-state parameters (λ, Γ and M) of the soil mixtures were found to be in conformity with the usual range for untreated soils.

Performance Evaluation of a Collapsible Soil Reinforced with Compacted Lateritic Soil Columns

AbstractThis study was carried out to evaluate a technique to improve lateritic soil layers that are susceptible to collapse upon wetting so that they can be used to support shallow foundations. Sp...

Soil water characteristic curves for laterite soil at different water contents and methods as lining system

Preventing groundwater contamination from the most common method of solid waste disposal technique i.e. landfilling is by proving hydraulic barriers. Accordingly, water movement in unsaturated soil is important in the analysis of leachate migration in soil material used as hydraulic barrier in waste containment systems. A full-scale experiment would be prohibitively costly and time consuming. The only feasible recourse therefore is to construct a model, which reasonably portray the behaviour of the full-scale system and simulate the relevant physical parameters and describes the overall significant characteristics of the transport phenomena. This paper presents the trends and patterns of soil water characteristic curves (SWCC) in terms of volumetric water content versus soil suction developed for compacted laterite soil specimens using data from pressure plate tests. Specimens were prepared at three different water contents corresponding to dry of optimum, optimum, and wet of optimum conditions. Models suggested by Brooks and Corey (BC), van Genuchten (VG), and Fredlund and Xing (FX) were used to obtain curve fitting parameters using the program “SWRC Fit” which performed nonlinear fitting of soil water retention curves. The SWRC Fit can simultaneously calculate the fitting parameters of these models with Root Mean Square Error values and draw the fitting curves. By comparing the results of the models using SWRC Fit, the model that best fits the laterite soil investigated will be chosen to be used for further analysis. The results show that the BC model represents the soil water retention curves better than the VG and FX models when the soil has distinct air entry suction. On the other hand, the VG and FX models can fit most soil water retention curves very well when discussion on the pore-size distribution is desired.

Monitoring Leachate Migration in Compacted Soil Using Digital Image Technique

As leachate has been a source of groundwater contamination worldwide, this paper examines the phenomenon of leachate migration on different gradations of compacted laterite soil used as sanitary landfill liners. Three different soil gradations (30%, 40% and 50% with respect to fines content) used in this study were compacted in circular acrylic columns to provide a clear visualization of leachate migration into the soils. Digital image technique was used in capturing photos at successive time intervals to monitor the leachate migration. The captured digital images were fed into Matlab and converted into hue-saturation-intensity (HSI) format. Surfer software then read the HSI and generated 2D contour plots. The results of the experiments showed that the leachate moves downward faster in the soil gradation with the least fines content. Hydraulic conductivity values decrease with increase in time duration and equally with increase in fines content. The hydraulic conductivities of the leachate for 30%, 40% and 50% fines were 3.64×10-9m/s, 2.40×10-9m/s, and 1.24×10-9m/s respectively. This reveals that for tropical laterite soils, gradation containing 50% fines content provides better hydraulic conductivity. The use of noninvasive digital image technique can enable designers/engineers to monitor and visualize the leachate migration in compacted soils in waste containment application systems.