Tropical Lateritic Soils Research Articles

Experimental and numerical analysis of instrumented caissons in tropical soil

This paper presents an experimental and numerical study on the behavior of three (3) instrumented caissons in a tropical laterite soil in the Planalto Central, DF, Brazil. The concrete caissons have a shaft diameter of 0.6 m, a bell diameter of 1.2 m and 1.3 m and lengths of 8.9 to 14.4 m. Static load tests were conducted out to investigate the behavior of the caissons. The results of load vs displacement and their interactions with the tropical soil were measured and evaluated using the methodology of Camapum de Carvalho et al. (2008, 2010) and numerical modeling with back-calculation of static load tests in the Plaxis 3D software. The paper presents the analysis of the load transfer lines and the comparison with the proposed methods. The results pointed to a constant load transfer along the shaft, with a significant contribution from the skin friction, developed for a fraction of the displacement necessary for its mobilization. The accuracy of using the Camapum de Carvalho et al. methodology stands out (2008, 2010), identifying the region dominated by skin friction, tip and plasticization of the foundation, confirming the authors’ predictions for a tropical soil in the Distrito Federal/DF, Brazil. The numerical method using the Plaxis 3D software, proves that for the limit test load there was a significant contribution from skin friction, which must be consider in the analysis of the behaviour of caissons.

Experimental study on strength and microstructural properties of hydrous magnesium alkalization in colligation with tropical laterite soil at ambient temperature

Experimental study on strength and microstructural properties of hydrous magnesium alkalization in colligation with tropical laterite soil at ambient temperature

Analysis of the geotechnical behavior of a piled raft in tropical lateritic soil based on long-term monitoring of columns, piles, and raft–soil interface

This paper aims to analyze and describe the geotechnical behavior of a piled raft foundation of a tall building (53 floors, 172.4 m high) through the monitoring of strains in the building’s columns and piles, the stresses at the raft–soil interface, and the foundation settlements. Field and laboratory tests were performed, and associated with axisymmetric and three-dimensional finite element analysis to the assessment of the measured data. The monitoring of the pile strains suggests the occurrence of soil expansion, caused by the raft excavation process, up to approximately 6 months after the excavation was completed. The presence of different soil profiles under the raft, with different mechanical properties, affected the distribution of the foundation settlements and the pile loads. Initially, the average pile loads were concentrated in the perimeter elements, but, as the construction of the building evolved, they tended to become more uniform. The effect of the superstructure stiffness caused successive load redistributions in the columns, which contributed to the maintenance of the maximum angular distortion of the building within the allowable values and reduced the load difference between the piles positioned in opposite soil profiles.

Geotechnical performance of tropical laterite soil using palm oil fuel ash and activator magnesium oxide stabilizer

Agricultural by-products waste, such as palm oil fuel ash (POFA) and magnesium oxide (MgO) activator, were utilized to achieve the chemical stabilization of laterite soil. This approach is environmental friendly as it aims at eliminating the potential hazards related to improper waste disposal methods and decreasing greenhouse gas emission generated by cement production to enhance the compressive strength of the soil. In this work, different percentages of additives ranging between (10% and 40%) with the addition of MgO between (2.5%and10%) were incorporated into the examined soil and cured at room temperature. Unconfined compressive strength (UCS) test, flexural strength (FS) test, scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis were conducted to examine the stabilized soil samples. The results showed that UCS values of LS-POFA-MgO sample increased up to 3.56 and 5.05 MPa after 7 and 28 curing days when the POFA-MgO was used at a ratio of 30:10, respectively. An increase of approximately 17 times greater than the untreated soil was also found. The FS LS-POFA-MgO showed a significant increase, exhibiting an enhanced peak behavior, thereby reducing deflection with brittleness. The findings were also substantiated by the pozzolanic activity enhancement of the former composition, as validated by the EDX patterns and SEM analyses. Therefore, the use of POFA based MgO activator is effective in addressing some soil issues and selecting the best soil mixtures. Furthermore, the soil's compressive strength improved significantly, making it suitable for utilisation as a material for the pavement base.

The structure of tropical lateritic soils as an impacting factor in the shape of soil-water characteristic curves

The presence of unsaturated flow in tropical lateritic soils of unknown hydromechanical behavior may lead to severe geotechnical problems. It is known that soil-water characteristic curves (SWCC) are a valuable tool to define this behavior and facilitate the suction estimation, acting on tests performed with no control of such parameter. This article aimed to determine and model the SWCC for 3 unprecedented tropical soils, in the undisturbed and the compacted conditions, from the Paraná state, located in the south of Brazil. The soils studied are one clay and two sands, all lateritic. The pressure plate and the filter paper methods were used to determine the SWCC. The samples were carved and submitted to the drying paths. Furthermore, Mercury Intrusion Porosimetry (MIP) tests were performed in samples of the studied soils in order to obtain the pore size distribution (PSD), contributing to the bimodal definition of curves and the prediction of SWCC main parameters. Both techniques (pressure plate and filter paper) were combined and the SWCC was adjusted by Gitirana & Fredlund model, which efficiently represents the shape of the traditional curves for tropical soils. Furthermore, the SWCCs were predicted by PSD and obtained satisfactory numerical fits. All SWCC presented air entry values in the macropores that are characteristic of soils as the lateritic, given that its structure was considered a key factor in the shape of the curves.

Settlement of bored piles with expander body system in lateritic soils

The Expander Body pile (EB) is a combination of a cast-in-situ pile method with an inflated, pump-grouted tip. The EB system's pioneering conjunction with the conventional drilling pile technique has improved work load, foundation security, cost reductions and abrupt displacements in lateritic, porous, unsaturated soils. The aim of this article is to analyze settlement estimates of bored piles equipped with the Expander Body System on tropical lateritic soil, using a deformability modulus obtained from laboratory and field tests. The piles were subjected to compression and uplift load tests. In addition, the estimates of the pile settlement are compared with the measured values, and the findings are discussed. The results strongly support that PMT and SPT tests present the optimal ratios between the measured and estimated settlements for both bored piles and bored piles with the Expander Body System. It can also be observed that CPT tests presented reasonable estimates for tensioned piles. Ultimately, it is verified that straightforward elastic models for the settlement assessment of bored piles can be used reliably in practice for piles equipped with the Expander Body System on tropical unsaturated soils.

Evaluation of Pulverized Cow Bone Ash and Waste Glass Powder on the Geotechnical Properties of Tropical Laterite

This research evaluated the ternary blend of agricultural waste in cow bone ash, industrial waste glass powder and cement in improving the Geotechnical properties of tropical lateritic soil. Soil samples were collected at depths ranging from 0.25 to 1.5 meters from two different pits dug inside the premises of Federal University Oye Ekiti, Ikole Campus. Preliminary tests were performed on the soil samples in their natural states and when stabilized with varying percentage of cement. Pulverized Cow Bone Ash and Waste Glass (PCBAWG) in the ratio 1:1 were introduced to the soil in varying proportions of 2 %, 4 %, 6 %, 8 % and 10 % along with optimum cement by weight of the soil sample. The strength index of the soil was assessed by examining the maximum dry density, optimum moisture content and the California Bearing Ratio (CBR) of the soil as well as the shear stress. The results of the preliminary investigation revealed the soil samples according AASHTO soil grouping; as A-2-4 lateritic clay and A-3 silty sand (non-plastic). The direct shear test results revealed that A-2-4 grouping had the best Geotechnical characteristics at 1.5m depth of excavation, while A-3 exhibited best Geotechnical soil characteristics at 1.25 m depth. There exists a positive relationship in the maximum dry density and optimum moisture content recorded. At optimum cement, the values of the unsoaked CBR of the soil samples greatly expanded and with the addition of 2 % PCBAWG, the CBR estimation of the lateritic clay decreased from 17.21–15.96 %, while that of silty sand increased from 11.00–16.28 %. The outcome of this research will aid Engineers, Environmentalist and construction workers on the utilization of these wastes in structural foundation construction in track with the sustainable development goals.

Field study on axial behavior of instrumented post-grouted steel pipe micropiles in tropical lateritic soil

This paper presents a field study on the axial behavior of new configuration of steel pipe micropiles in tropical lateritic soil. The micropiles were installed following a two-step grouting process with high injection pressures at a new experimental site located at the University of Campinas (Unicamp). The main innovation of the micropiles relies on the use of high-strength steel pipes as a drilling tool, casing protection, structural component and injection device. Full-scale pile loading tests were performed under compression and tension loads to investigate the axial behavior of the micropiles. The micropiles were instrumented along the shaft with electrical extensometers, and they were monitored during the progress of the loading tests. The load–movement responses, elastic moduli, axial load transfer mechanism, and unit bond stress relating to the micropiles and their interactions with the tropical soil were measured and evaluated. The bearing capacity of the post-grouted micropiles was considerably improved by the proposed post-grouting technique. The ultimate load capacity of the grouted steel pipe micropile under a compression load is approximately the same under a tension load. The average ultimate bond strength was 99 kPa and 100 kPa for the micropile under compression and tension, respectively. The distribution of unit bond stress along the shaft of the micropile under compressive and tensile load presented a post-peak softening behavior. The average ultimate grout-to-ground strength at the soil–micropile interface was 2.4 and 1.7 times greater than other nongrouted and non-injected piles installed in the same soil conditions at Unicamp.

Plasticity modification of a tropical laterite by electrochemical stabilization

This paper reports the changes incurred in Liquid Limit (LL) and Plastic Limit (PL) of a high plasticity Residual Tropical Laterite Soil (RTLS) subjected to electrochemical stabilization (ECS) amended with supporting ions. Calcium ion (Ca2+) from calcium chloride and phosphate ion (PO43−) from phosphoric acid were injected separately and then together into the RTLS under direct electric current (DC) for a period of 5 days. The influence of applied potential difference and polarity reversal on the electrochemical processes was evaluated based on the changes in soil plasticity of the treated RTLS and the concentrations of Ca2+ and PO43− deposited. The data were also analyzed statistically using Analysis of Variance. The results showed downward trend in both the LL and PI values of the treated RTLS with the highest reduction in Ca2+ treated soil. There was significant accumulation of the injected supporting ions in the test soils with highest accumulations of 43-fold and 13-fold in PO43− and Ca2+ concentrations, respectively, based on their original values in RTLS. The applied potential difference and its reversed polarity appeared to affect the PO43− concentration accumulation, while the LL and PI of the RTLS showed the most reduction in those treated electrochemically with Ca2+ as the supporting ion.

Numerical modeling of leachate migration in compacted tropical laterite soil

To protect groundwater from leachate contamination in sanitary landfill involve the use of hydraulic barriers i.e. liners and covers. Nonetheless, can these barriers continue to impede the migration of leachate over a long period? 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 research investigates the long-term performance of compacted tropical laterite soil liners at various gradations against leachate migration in sanitary landfills using numerical modeling. Series of laboratory experimentation were carried out using three different laterite soil gradations (30%, 40% and 50% with respect to fines content) compacted at optimum moisture content using British Standard light energy. Leachate was poured on the compacted soil in an acrylic column and its migration was monitored using Digital Image Technique (DIT). Subsequently, PetraSim computer software a graphical interface used to solve problems related to contaminant transport was applied to predict the velocity of leachate migration. The predicted velocity values for 30%, 40% and 50% fines are 4.5 x 10−7 m/s, 7 x 10−9 m/s, and 8 x 10−10 m/s, respectively. This shows that the laterite soil with 50% fines content is more compatible with the leachate and can be used as soil liner. The outcome of this research would enable designers to use non-destructive method to monitor and predict leachate migration in compacted soil liners to simulate leachate migration in waste containment applications.

Stabilization Effect of Aluminum Dross on Tropical Lateritic Soil

This experimental research assessed the engineering and geotechnical properties of Aluminum dross (ALDR). Glumly, this solid waste is usually open dumped with detrimental effect on the environment. In a bid to reduce solid waste in the environment and also improve pavement interlayer properties, this research utilized ALDR as a stabilizer for tropical lateritic soil. The lateritic soil was stabilized with the addition of this solid waste at 2% intervals from 2% to 16%. Response surface analysis was used in optimizing the strength and consistency of the stabilized soil sample. The addition of this non-conventional stabilizer helped in modifying the engineering properties of the soil sample, this had indications on the atterberg limit as the liquid limit, and the plasticity index increased from 43% to 54.61% and 28.02%- 40.8% respectively, while the plasticity index reduced from 15.1% - 13.8% signifying soil improvement. The load-bearing capacity of the sample increased from 51.22% to 62.41%. Additionally, the unconfined test showed that addition of ALDR residue improved the consistency of the stabilized soil sample. From the model equation, a positive relationship exists between CBR and UCS. R2value of 0.81 showed the robustness of the model developed. The research showed that aluminum dross is a suitable material for improving the engineering properties of the tropical lateritic soil towards a sustainable road construction.

Influence of Cement Chemistry on the Performance of Cement Stabilized Tropical Lateritic Soil

Chemical composition affects overall performance of cement on other materials such as when used in concrete or for stabilization of lateritic soil. This research studied the influence of chemical composition of three Portland cement types represented as samples A, B and C on engineering performance when mixed with laterite under tropical environmental conditions.The Lateritic soil sample classified according to AASHTO as A-5(4) was collected from a typical tropical region. Performances of these cements were considered at different cement-laterite proportions, varying from 2-14%. Parameters determined include chemical and metallic contents of the cements as well as Maximum Dry Density (MDD), California Bearing Ratio (CBR) and Unconfined Compressive Strength (UCS) of cement-laterite mixat a temperature range of 26-28°C. One-way Anova test was used to validate the significant variation in the chemical composition of cements and the unconfined compressive strength. Results indicate that the bearing capacity and unconfined compressive strength of laterite – cement mix depend on the quantity of lime (CaO) and silicon dioxide (SiO2) content in the cement; results also confirm the influence of Aluminium Oxide (Al2O3) and sulphur trioxide (SO3) content on the setting time of cement.

SUSTAINABILITY IN ROAD CONSTRUCTION: USING BAMBOO STRAW ASH TO IMPROVE THE INDEX PROPERTIES OF LATERITIC SOIL

In a bid to improve sustainability in road construction and reduce the cost of road construction, there is a need for a green alternative. This research improved the geotechnical properties of tropical lateritic soil using Bamboo Straw Ash (BSA). The lateritic soil was stabilized with increasing percentage of BSA at 0%, 2%, 4%, 6%, 8%, 10%, and 12%. The index properties, Compaction (Maximum moisture content, Maximum dry Density), CBR, of the soil samples with BSA were evaluated. Response Surface Analysis was used to model the mathematical relationship between the atterberg limit and the CBR of the BSA stabilized soil sample. The plasticity index of the unstabilized soil sample was 14.01 upon the addition of 16% BSA, the plasticity index reduced to 10.73 which showed an improvement in the soil index properties. The CBR increased from 26.38% to 30.2% at 0% and 8% respectively which signifies an improved strength. From the Respons Surface Analysis, the highest plasticity index achievable with BSA stabilization is 27.18. The model equation showed that the plasticity index and plasticity limit have a positive relationship with the CBR. Ultimately, the use of BSA provides a cost-effective and green alternative to lateritic soil stabilization in road construction. Keywords: Bamboo straw ash, soil stabilization, strength properties, compaction, Pavement material

Influence of electrochemical treatment on a typical laterite

The results of the undrained shear strength (Su) and stiffness (Vs) of electrochemically stabilised residual tropical laterite soil (RTLS) are presented. Calcium (Ca2+) and phosphate (PO43−) ions from calcium chloride and phosphoric acid, respectively, were injected individually and together into remoulded RTLS by applying 1 and 2 V/cm direct current electrical gradient for 5 d to facilitate cementation within the treated soil. Three different systems were employed using 1·0 M calcium chloride or 0·01 M sodium chloride as the anolyte and 1 M phosphoric acid or 0·01 M sodium chloride as the catholyte. Polarity reversal was also employed in some tests. The efficacy of the treatment was based on the soil Su and stiffness. The injection of Ca2+ led to a reduction in both the Su (90%) and stiffness (8%) of the treated RTLS. The injection of PO43− resulted in improvement in both the soil Su (151%) and stiffness (20%) of the treated RTLS. The study concluded that in stabilising the RTLS, injection of PO43− is effective whereas the injection of Ca2+ is not.

Sustainable Improvement of Tropical Residual Soil Using an Environmentally Friendly Additive

Many tropical residual laterites have relatively poor engineering properties due to the significant percentage of fine-grained soil particles that they contain, which are formed by the soil weathering process. The widespread presence of laterite soils in tropical regions often requires that some form of soil improvement be performed to allow for their use in various civil engineering applications, such as for road base or subbase construction. One of the most commonly utilized stabilization techniques for laterite soils is the application of additives that chemically react with the minerals that are present in soil to enhance its overall strength; effective soil stabilization can allow for the use of site-specific soils, and can consequently result in significant cost savings for a given project. With an increasing focus on the use of more environmentally friendly and sustainable materials in the built and natural environments, there is an emerging interest in eco-friendly additives that are an alternative to traditional chemical stabilizers. The current study examines the viability of xanthan gum as an environmentally friendly stabilizer that can improve the engineering properties of tropical residual laterite soil. Unconfined compressive strength (UCS) tests, standard direct shear tests, Brunauer, Emmett, and Teller (N2-BET) surface area analysis tests and field emission scanning electron microscopy (FESEM) tests were used to investigate the effectiveness of xanthan gum for stabilization of a tropical laterite soil. The UCS test results showed that addition of 1.5% xanthan gum by weight yielded optimum stabilization, increasing the unconfined compressive strength of the laterite soil noticeably. Similarly, direct shear testing of 1.5% xanthan gum stabilized laterite specimens showed increasing Mohr–Coulomb shear strength parameters with increases in curing time. From the FESEM results, it was observed that the stabilization process modified the pore-network morphology of the laterite soil, while also forming new white layers on the surface of the clay particles. Analysis of the test results indicated that xanthan gum stabilization was effective for use on a tropical residual laterite soil, providing an eco-friendly and sustainable alternative to traditional soil stabilization additives such as cement or lime.

Strength Performance Based on Flexibility from Laterite Soil Using Tire Powder and Micro Silica

In terms of environmental issues and human health, one of the advisable techniques to improve soil behavior is the use of scrap tires for soil structures. According to the literature, Tire-Derived Aggregates (TDA) are one of the valuable materials in different field of Geotechnical that can be used. TDA properties correspond to some important factors such as high level of flexible, lightweight, high permeability and economic material comparing with sand. Strength performance based on increasing flexibility from laterite soil is the main goal of this study. For this purpose, tropical laterite soil was mixed using TDA and micro silica (MS). As a research method, unconfined tests were carried for thirteen samples based on different percentage of the additives. As a result, the significant reduction for elasticity modulus and strength was observed when soil mixed just using TDA. In addition, the rate of strain at the peak of the curve was dramatically increased. The best performance was found using 6% additives when the ratio was 3% MS and 3% TDA. In fact, the effect of MS was more to increase strength. To recommend, the seepage controlling will investigate at next.

Physicochemical behavior of tropical laterite soil stabilized with non-traditional additive

Non-traditional soil stabilizers are widely used for treating weak materials. These additives are cost- and time-effective alternatives to more traditional materials such as lime and cement. It has been well established that the treatment of natural soil with chemical additives will gradually affect the size, shape, and arrangement of soil particles. Furthermore, the degree of improvement is dependent on the quantity and the pattern of new products formed on and around the soil particles. In this paper, unconfined compressive strength (UCS) test was performed as an index of soil improvement on mix designs treated with calcium-based powder stabilizer (SH-85). The time-dependent changes in shear strength parameter and compressibility behavior of treated soil were also studied using standard direct shear and one-dimensional consolidation tests. In order to better understand the shape and surface area of treated particles, FESEM, N2-BET, and particle size distribution analysis were performed on soil-stabilizer matrix. From engineering standpoint, the UCS results showed that the degree of improvement for SH-85-stabilized laterite soil was roughly five times stronger than the untreated soil at the early stages of curing (7-day period). Also, a significant increase in the compressibility resistance of treated samples with curing time was observed. Based on the results, less porous and denser soil fabric was seen on the surface of clay particles. FESEM images of the treated mix designs showed the formation of white lumps in the soil fabric with the cementitious gel filling the pores in the soil structure.

Rock magnetic properties of lateritic soil profiles from southern India: Evidence for pedogenic processes

We report here data on the pH, electrical conductivity (EC) and environmental magnetic properties (χlf, χfd, χARM, IRMs at different field strengths) of modern tropical lateritic soils from Aribail, Miyapadavu and Uliyathadka, all in the Kasaragod District of Kerala, southern India. This study aims to characterize the rock magnetic properties of lateritic soils that formed under tropical high-rainfall conditions and determine the effects of pedogenesis on soil magnetic properties in comparison with temperate soils. The profiles may be divided into two or three zones based on differences in magnetic mineral concentration, grain size and mineralogy. There is no magnetic enhancement of topsoil in any of the profiles studied. As the lateritic rocks in the region are ferruginous, the lateritic soils developed over them contain significant amounts of coarse grained lithogenic magnetite as well as hematite. Because of the presence of this ‘laterite-derived’ magnetite and hematite, the lateritic soils have much higher susceptibility values when compared to temperate soils. The upper zone is characterized by a higher proportion of lithogenic grains and the lower zone by superparamagnetic (SP) grains. This is probably because of iron reduction and dissolution of fine magnetic grains at the profile-top because of the excessively high rainfall (average=~3500mm/year) in the region. The slight increase in χlf and SIRM values toward the top of the Aribail and Miyapadavu profiles is due to the presence of coarse magnetic grains. This characteristic is common to all the three profiles irrespective of the topography. Compared to pre-monsoon samples, post-monsoon samples exhibit an increase in the proportion of SP grains. However, the magnetic grain size of lateritic soils from the three locations is similar to that of temperate soils.

Effect of Non-Traditional Additives on Engineering and Microstructural Characteristics of Laterite Soil

The stabilization of soils with additives is a chemical method that can be used to improve soils with lowengineering properties. The stabilizing mechanisms of TX-85 and SH-85 additives are not fully understood, and their proprietary chemical composition makes it very difficult to evaluate the stabilizing mechanisms and predict their performance. The objective of this study was to investigate the macro- and microstructural properties related to tropical laterite soil mixed with the specified non-traditional soil additives. The tests carried out, i.e., compaction and unconfined compression strength, were used to assess the engineering and shear properties of the stabilized laterite soil, and the physicochemical changes were monitored via field-emission scanning electron microscopy (FESEM) and thermal gravity analysis. Based on the results, it was found that both additives can decrease the dry density and increase the laterite soil strength approximately fourfold in comparison with the natural soil. FESEM results showed that the porosity of untreated soil was filled by the new cementitious products. Also, it was found that the treatment of laterite had a marginal impact on the thermal characteristics of the soil.

Strength behavior and microstructural characteristics of tropical laterite soil treated with sodium silicate-based liquid stabilizer

Although the effects of nontraditional stabilizers on the geotechnical properties of tropical soils has been the issue of investigation in recent years, the micro-structural characteristics of nontraditional soil additives and in particular selected additive (TX-85) have not been fully studied. Nontraditional soil stabilization additives are widely used for stabilizing marginal materials. These additives are low-cost alternatives to traditional construction materials and have different compositions. They also differ from one another while interacting with soil. In line with that, it was the objective of this research to investigate the strength properties and physicochemical mechanisms related to tropical laterite soil mixed with the liquid stabilizer TX-85. Macro-structure study, i.e., compaction, and unconfined compression strength test were used to assess the engineering and shear properties of the stabilized laterite soil. In addition, the possible mechanisms that contributed to the stabilization process were discussed using various spectroscopic and microscopic techniques such as X-ray diffractometry (XRD), energy-dispersive X-ray spectrometry, scanning electron microscopy, and Fourier transform infrared spectroscopy. From engineering point of view, the results indicated that the strength of TX-85 stabilized laterite soil improved significantly. The degree of improvement was approximately four times stronger than natural soil after a 7-day curing period. The XRD showed no crystalline products (gel form). Moreover, weathering effects were obvious in TX-85 treated samples in most of clay minerals’ peak intensities. These effects were reduced especially for kaolinite mineral inside the soil with curing time.