An Experimental Study on Geopile Installed in Expansive Clay

Expansive soil is the most predominant geologic hazard which shows a large amount of shrinkage and swelling with changes in their moisture content. This study investigates the macro-mechanical and micro-structural behaviours of dredged natural expansive clay from coal mining treated with ordinary Portland cement or hydrated lime addition. The stabilised expansive soil aims for possible reuse as pavement materials. Mechanical testing determined geotechnical engineering properties, including free swelling potential, California bearing ratio, unconfined compressive strength, resilient modulus, and shear wave velocity. The microstructures of treated soils are observed by scanning electron microscopy, x-ray diffraction, and energy dispersive spectroscopy to understand the behaviour of the expansive clay blended with cement and lime. Test results confirmed that cement and lime are effective agents for improving the swelling behaviour and other engineering properties of natural expansive clay. In general, chemical treatments reduce the swelling and increase the strength and modulus of expansive clay, subjected to chemical content and curing time. Scanning electron microscopy analysis can observe the increase in formation of particle clusters with curing period, and x-ray diffraction patterns display hydration and pozzolanic products from chemical particles. The correlations of mechanical properties and microstructures for chemical stabilised expansive clay are recommended.

This study investigated the stabilizing potential of cement-fly ash on expansive clay with a view to discovering a more effective soil stabilization method for road works. It was carried out between July 2003 and March 2004 in Civil Engineering Department, Obafemi Awolowo University, Ile-Ife, Nigeria.The expansive clay soil samples were first subjected to general classification tests where three classes of samples evolved; 12% cement optimal mix, 9% cement plus 3% fly ash optimal mix, and the 0% (unstabilized) natural clay soil sample. The three different classes of samples were then subjected to engineering tests; Maximum Dry Densities (MDD), Optimum Moisture Contents (OMC), California Bearing Ratio (CBR), Unconfined Compression and the Undrained Triaxial. The results showed that the soil sample stabilized with a mixture of 9% cement plus 3% fly ash was better in respect to MDD, OMC, Bearing Capacity and Shearing Resistance, when compared with sample stabilized with 12% cement plus 0% fly ash. This showed that the addition of a certain percentage of fly ash will improve the stabilizing potential of cement on an expansive clay soil. Keywords: Cement and fly ash stabilization; soil strength; expansive clay; amendment.Journal of Technology and Education in Nigeria Vol. 12 (2) 2007: pp. 1-8

This work investigates the behavior of a silty clay stabilized with 3, 6, 9, and 12 % of ground granulated blast-furnace slag (GGBS), respectively, and 1 % of quicklime used as an activator. The influence of the composite (Quicklime - GGBS) on the immediate behavior of the silty clay is studied by examining the Atterberg limits, the maximum dry density, the optimum moisture content, and the immediate bearing index. The evolution, at different curing periods (1, 7, and 28 days), of the mechanical characteristics of the treated soil, namely unconfined compressive strength, cohesion, and internal angle of friction is also studied. The increase, up to a dosage of 9%, of the GGBS content, leads to an increase in the optimum moisture content, the immediate bearing index, the unconfined compressive strength, and shear strength parameters. Paradoxically, a decrease in the plasticity index and the maximum dry density was observed.

To investigate the soil structure and mechanical behavior of an unsaturated expansive clay soil, triaxial and mercury intrusion tests have been performed and are presented in this paper. Also an optical test system was developed for studying the internal structure evolution of the unsaturated expansive soil during shear-loading tests. The research results show a linear relationship between the cohesion intercept and the degree of saturation of the unsaturated clay for the test data. For the tested soil, the pore-size distribution curves were found to be bimodal. The measurement results from mercury intrusion tests confirm that the micropores of Guangxi expansive soils of this study remain constant, and that the macropores vary with the dry density of soil samples. Comparing the volumetric strain curves with the soil particle area curves, some correlation and dependence on the macropore variation of soil samples during shear-loading tests can be shown to exist.Key words: soil structure, mechanical behavior, unsaturated soil, mercury intrusion, expansive clay.

Volume change behaviour of expansive clays has been one of the leading causes of damage to civil infrastructures worldwide. Contributing factors that lead to failures relate to changes in water content within the soil. Variations of water content can vary significantly based on an area’s climate regime. Trinidad has two seasons, the dry season (January to June) and the wet season (July to December). This variation leads to volume changes of expansive clay, where they exist mainly within the central and south regions of Trinidad. These areas are densely populated by residential and commercial buildings, which can be susceptible to damages from unsaturated expansive clays. The Soil Water Characteristic Curve (SWCC) for expansive clays is critical to estimate their unsaturated properties for the analysis of water flow movement. This study investigates the SWCCs for two expansive clay soil types in Trinidad. A WP4-T (Water Potential Measurement) is used to measure soil suction. The shrinkage curve (SC) test is conducted to consider the volume change of soil. The Fredlund and Xing (1994) SWCC equation and Fredlund and Zhang (2013) SC equation are used to fit the measured data. The SWCCs in terms of gravimetric and volumetric water contents and degree of saturation are compared. It is found that the normalised degree of saturation SWCC can provide a better display of the SWCC and estimation of the air-entry value.

Proceedings of geotechnical sessions at the 2001 Annual Civil Engineering Conference, held in Houston, Texas, October 10-13, 2001. Sponsored by the Shallow Foundation and Soil Properties Committee of the Geo-Institute of ASCE. This Geotechnical Special Publication contains 14 papers that discuss the effects of trees and moisture movements on various lightly loaded foundations on expansive clays. Papers review current state of the practice in foundation design, maintenance, and remediation as it relates to vegetative effects and expansive clays on foundations. Topics include: tree root damage to buildings; predicting volume changes in expansive soils resulting from environmental factors including vegetation; drought; expansive clay soil problems and solutions throughout the world; soil-structure interaction; field test program to obtain geotechnical properties; depth of wetting and active zone in expansive soils; slabs on expansive clay with vegetation considerations; volume change coefficient of expansive clay; in-situ modification of active clays for shallow foundation remediation; cracking of pavement due to drying shrinkage; soil suction measurements; and data base on under-slab moisture contents in Texas.

This paper presents experimental data on the liquid limit (LL), plastic limit, plasticity index (PI), free swell index (FSI), optimum moisture content, maximum dry density (MDD), stress–strain behaviour and unconfined compressive strength (UCS) of an expansive clay blended with varying amounts of cement and ground granulated blast furnace slag (GGBS). Both cement and GGBS were independently added to the expansive clay up to 15% in increments of 5%. FSI, respectively, decreased from 145 to 100% and from 145 to 80% when cement and GGBS contents increased from 0 to 15%. LL and PI, respectively, decreased by 23 and 41% when cement content increased from 0 to 15%. Similarly, LL and PI, respectively, decreased by 14 and 30% when GGBS content increased from 0 to 15%. MDD increased, respectively, by 11 and 9·5% when cement content and GGBS content increased from 0 to 15%. The UCS of the cement–clay blends and the GGBS–clay blends increased with increasing additive contents. For a given additive content, UCS increased significantly with increasing curing period.

Expansive soil is considered a potential natural hazard, which can cause extensive damage to structures if not adequately treated. One of the mitigation techniques of such soil is to mix it with lime. This paper aims to study the effect of the limestone and hydrated lime on the behavior of the highly expansive clay. Ca bentonite is used as the highly expansive clay. The bentonite has been mixed with lime in varying amount ranging from 0 to 10 %. Each bentonite–lime sample was remolded at modified AASHTO density and optimum moisture content. Four series of tests were performed on each mixture included: swelling potential, swelling pressure, California bearing ratio (CBR), and unconfined compression strength test. The results of the study showed that mixing limestone and hydrated lime with expansive clay reduces swelling potential and swelling pressure. There is a further reduction in the swelling pressure and swelling potential with increasing lime percentage. But mixing hydrated lime with clay causes significant reductions in swelling potential and swelling pressure. The swell potential decreases from 34.5 to about 26.5 % and 1 % in case of clay sample mixed with 10 % limestone and 10 % hydrated lime, respectively. The non-treated bentonite implies high values of CBR and unconfined compressive strength. The limestone has a negative effect on the strength of the clay. While the hydrated lime causes increases in the strength of the clay. The strength of the clay–hydrated lime mixtures has further increases with increasing lime content and curing time.

The problems that occur in the Toll Road Project Section 6a of the Sumedang – Dawuan package are subgrade soils including expansive soil types. Where the type of expansive soil is a soil type that is not good with very high clay content, expansion and shrinkage. This potential for shrinkage causes less stability in the road construction so that it affects the safety and comfort of traffic. The general technical properties of expansive soils are that they have a fairly high moisture content and low bearing capacity. Because of these properties, expansive soils are classified as poor soils to be used as subgrades. One way to overcome this is by improving the soil or so-called soil stabilization. In this study, the material used for stabilizing the expansive soil is limestone. Limestone or limestone is a carbonate rock that is formed biologically and biochemically.This research was conducted with the aim of knowing the effect of adding limestone to the physical properties of expansive clay and knowing the optimum level of addition of limestone so as to produce a maximum increase in the stability of the road construction subgrade. The research method used is the experimental method. The study was designed with 5 treatments, namely 0%, 25%, 50%, 75% and 100% of the use of limestone on expansive clay soil.The results showed that the use of limestone as a stabilizing agent for clay in the Section 6a of the Sumedang – Dawuan Toll Road Project affects the physical and mechanical properties of the expansive clay. Where the higher the addition of limestone, the smaller the liquid limit (LL), plasticity limit (PL), moisture content and swelling, while for specific gravity, compaction and CBR the higher. The use of limestone in the Toll Road Project Section 6a Sumedang – Dawuan Package optimum 75% with a ratio of 25% expansive clay with a CBR value of 3.75% < 6% (Minimum requirement of CBR value for road pavement subgrade) and produces a development value ( swelling) 3.85% > 1.25% (maximum limit conditions for pavement subgrade swelling). The CBR value and swelling (swelling) do not meet the requirements as a subgrade for road pavement, in accordance with the expressway technical specifications for a minimum subgrade density of 100℅, a minimum CBR of 6℅ and a maximum swelling of 1.25℅.

Interactions of expansive clay soils with transportation facilities have caused billions of dollars of damage. In the process of determining agents and methodologies to overcome expansive clay behavior, multiple injections of chemical agents into the subgrade to modify clay behavior are most promising. A study was conducted to optimize a potassium-rich solution of four parts. The modifying solution has been injected into expansive clay subgrades with success since the early 1970s. A laboratory methodology was developed to inject specimens multiple times and to conduct swell tests. Screening tests were conducted to evaluate linear effects that each of the four constituents had on swell response through interpretation of a factorial design. Analysis of replicated tests, randomly arranged in blocks, revealed that one constituent had no effect on swell behavior. A central composite experimental design then was used to optimize the remaining constituents. The resulting response surface equation led to an optimal combination for swell abatement, confirmed during short- and long-term verification testing. The optimal blend of constituents was determined to reduce swell from 7.2 percent to 0.84 percent under injection situations simulating the field, and it was found to improve the reduction in swell by 2.6 percent compared with the original blend. In addition, XRD confirmed that modification of clay occurred. This study was unique in its use of laboratory simulation of multiple field injections and in its use of statistical analysis to minimize the number of tests needed to ensure confidence in the optimization sought.

The present research work deals with an expansive high plastic clayey soil with cement kiln dust (CKD) and stabilizer (RBI Grade 81). The physical and engineering properties of soil are plasticity, compaction, unconfined compressive strength (UCS), consolidation and California bearing ratio (CBR) of the clayey soil and clay treated with CKD and stabilizer were determined. Soil chemistry was examined before and after treatment using scanning electron microscope (SEM) and elemental dispersive spectrometer. The clay mixed with CKD, CKD and RBI Grade 81 was found that optimum contents are 10 % (CKD), 15 % CKD with 4 % RBI Grade 81, respectively. The result indicates that CKD alone will decrease maximum dry density and increase optimum moisture content. CKD with RBI Grade 81 slightly increases maximum dry density and decreases optimum moisture content. UCS increased with CKD alone and CKD with RBI Grade 81 from 88.3 to 976 kN/m2, respectively. CBR values were increased by the addition of CKD, CKD with RBI Grade 81 from 1.65 to 21.7 %. With the curing time of 3, 14 and 28 days, UCS and CBR values were increased due to pozzolanic reaction from cementations material. The treated soil has considerable reduction in compression index. SEM images clearly indicate the formation of CSH and CAH gel.

Construction on weak expansive soils is challenging due to their low bearing capacity and high-volume susceptibility under moisture fluctuation. The uplift pressure from expansive clay can induce significant swelling pressure on foundations, but on the other hand, shrinkage of clay can result in substantial foundation settlement during dry seasons. This differential movement of the foundation can distress the superstructure of a building, resulting in serviceable and ultimate limit state failures. The current approach to dealing with foundations in expansive clay soils is to construct a rigid slab that can withstand the anticipated movement or a pier-type approach using engineering design principles or a normal-type slab based on the fill being placed under controlled conditions. We introduce a capping layer under the foundation to control moisture fluctuation and increase the bearing capacity of the foundation using a recycled glass-based stabilization approach. A prototype foundation was constructed in the laboratory using an optimum stabilization mix design that was derived using glass and other sustainable additives. Slab movements and soil conditions were monitored over a 6 month period under simulated dry/wetting moisture fluctuations and operational loads. Results revealed that the performance of the foundation under controlled conditions was outperformed by the capping layered foundation during service loadings including seasonal moisture fluctuation. The outcomes from this research will have a significant impact on improving foundation performance in expansive soils, as well as proposing a sustainable foundation construction process using recycled glass waste.

Laboratory investigations on the swelling behavior of composite expansive clays stabilized with shallow and deep clay-cement mixing methods

This research aimed to determine and evaluate the load carrying capacity of underreamed piles embedded in expansive soils. Eight models of concrete piles were developed to examine the influence of piles’ bulb number and length on ultimate load carrying capacity. The piles used in this work had 20 mm stem diameters and 40 mm bulb diameters, and multi-layer soils (expansive soil above dense sand) were used. The piles used in the experiments were divided into two groups, each with four piles. The first group with l/d=14 had all piles embedded in the expansive soil layer and the pile’s tip set on dense sand while the other group, with l/d=24, had the pile stems embedded in the expansive soil and all bulbs in the dense sand. Experiments were then done under two conditions: optimum moisture content and soil completely saturated with water, with results that showed that the percentage of ultimate load carrying capacity increased in proportion to the l/d ratio on adding one bulb to a straight shaft pile and then increased slowly for piles with 2 or 3 bulbs in saturation conditions. The percentage of ultimate load carrying capacity increased similarly in optimum moisture content conditions. The results also showed a decrease in ultimate load carrying capacity between the two conditions of tests for piles with the same l/d and the same number of bulbs, however.

Rapidly increasing infrastructural activities across the world demand suitable land for founding the substructure. The coming era shall face trouble both with the scarcity of suitable land as well as challenges to deal with the existence of problematic soils at the site. Volumetric changes in the form of swelling and shrinkage with moisture variation are most commonly observed in expansive soils. Large damage/distress to the infrastructure founded on this type soils has been observed. Understanding of swelling and shrinkage of expansive soils with moisture variation is of primary importance. This paper presents an experimental study on determination of swelling–shrinkage and its variation with time and placement moisture content. An experimental setup has been designed and developed to accommodate three soil samples of 100 mm diameter and 100 mm height and swelling pressure measurement through constant volume method. Soils were procured from Delhi–Mumbai Expressway site near Ankleshwar, Gujarat, which was later aired dried and pulverized. Soil samples were prepared at three different preparation moisture content (i) at optimum moisture content, (ii) 5% on the dry side of optimum and (iii) 5% on the wet side of optimum. Experimental findings revealed maximum swelling pressure generation within first 24 h after commencement of the experiment. Swelling pressures of 41.8 kPa, 59.44 kPa and 23.22 kPa were observed for specimen prepared at optimum moisture content, at 5% dry side of optimum and 5% wet side of optimum, respectively. While swelling pressure found to increase till seven days, though at a lower rate, observed swelling pressure values were 55.73 kPa, 83.6 kPa and 37.25 kPa for specimen prepared at optimum moisture content, at 5% dry side of optimum and 5% wet side of optimum, respectively. The % shrinkage area were found as 22%, 33.8% and 15.2% for the samples prepared at OMC, WSO (OMC + 5%) and DSO (OMC-5%), respectively.