Recycled Glass-Based Capping Layer for Foundations in Expansive Soils

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℅.

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.

Clay is a soil with low permeability. Clay is considered a problematic soil besides peat soil. The main problem with clay is its mineralogy. Expansive clay soils contain the minerals kaolinite, illite, and montmorillonite. Montmorillonite has weak bonds between its layers. These weak bonds make the soil easily incorporated, one of which is water. Water approaching expansive soil will bond with it and cause swelling. Expansive soil improvement studies have been conducted. One of them is electrokinetic. Expansive soil from Karawang, Indonesia is one of the soils with a high swelling index. This is because montmorillonite is inside. The Karawang expansive soil will be improved by flowing several salt solutions with various voltages. The applied voltage will flow the solution from the cathode to the anode and fill the clay minerals. Four voltage variants will be applied with the same electrokinetic application time. The mineralogy of soil before and after electrokinetic improvement undergone changes. The changes can be seen from SEM and XRF testing. The improved soil changed its physical properties from clay with high plasticity to clay with low plasticity. Chemical elements from salt solution trap in montmorillonite then make positive changes in soil mineralogy, soil physical properties, and mechanical properties. The mechanical properties can be seen in a decrease in the C value and an increase in the soil angle of friction after electrokinetic improvement. After electrokinetic improvement using calcium chloride, the lowest soil cohesion value was 12.356 kg/cm2 at 12 V. After electrokinetic improvement with calcium dioxide, the lowest cohesion value at 12 V voltage is 19.22 kg/cm2. In barium sulfate solution, the lowest soil cohesion at 15 V is 12.16 kg/cm2. The soil swelling value decreased after improvement with calcium chloride to 0.008 % from 0.027 %. The research results in calcium chloride with 12 V give optimized results on soil improvement with electrokinetics

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.

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

Stabilization of expansive soils for use in construction

Construction and maintenance of roadways and irrigation canals in southeastern San Joaquin (Central) Valley of California has entailed passing through large sections of the Porterville soil series, an expansive clay soil. The geologic development of this expansive soil, as shown in outcrops along Highway 180 near Minkler, Fresno County, appears to have been dependent upon two coincident factors of general importance: 1) volcanic eruptions of ash (with approximately andesitic composition) resulting in lahars with some size sorting due to re-deposition; and 2) groundwater with excess Ca ++ ions due to percolation through basic or ultra-basic plutonic rocks. Widespread valley areas may have potential construction problems which are largely due to the erosion and redeposition of the expansive clay of Porterville and Mt. Olive soils. A new method is presented, derived from previous studies of expansive soil, for the measurement of the soil expansion pressure and its correlation with soil moisture and density, with small expansion volume. Methods of controlling volumetric changes in such soils are discussed. The nature of the dominant clay mineral, montmorillonite, and the identification of the other soil minerals is presented, using X-ray diffraction, infra-red spectra, and differential thermal analytical methods.

Disintegration and decomposition of sedimentary materials and igneous/metamorphic rocks in arid and semi-arid plateaus form expansive soils. The parent materials of expansive soils are 5.3 million years (basic igneous rocks) to > 570 million years (basement complex rocks) old. Developing an index property to estimate the fraction of primary minerals that decompose to clay is important as expansive clays drive their moisture-related volume changes. Data of 119 expansive soils from Nigeria, Tanzania, Ethiopia, Sudan, India, Australia, Oman, Chad Basin, Morocco, Kenya, and Zambia are analyzed to develop an index property termed decomposition ratio (Dr) to quantify the fraction of primary minerals that decompose into expansive clay. The sand+silt fractions represent the undecomposed primary mineral content, while the clay fraction represents the fraction of primary minerals that decomposed completely. Expansive soils from India, Sudan and Tanzania are characterized by median Dr values of 0.52–0.74; expansive soils from Ethiopia, Nigeria, Australia, Ghana, Chad Basin, Morocco, Zambia, and Kenya are characterized by median Dr values of 1.02–1.43. Dr values < unity imply that < 50% of primary minerals have decomposed into clay. Analysis of Dr data indicated that clay formation tends towards equilibrium when weathering of parent material depletes their primary mineral contents to 35%. Normalizing liquid limit with Dr regulates variations in liquid limit of expansive soils with similar clay content but formed under different conditions.

Expansive clays are found worldwide in arid and semiarid regions. Such soils are considered a natural hazard for civil engineering infrastructures especially when they are lightly loaded. Expansive soils are often unsaturated due to the high absorption capacity of moisture. The damaging effect of expansive soils is intimately related to the distinctive soil‐water characteristic in the surficial soil layers subjected to wetting‐drying cycles. The soil‐water characteristic curve (SWCC) also known as the water‐retention curve shows the fluctuation of suction with the moisture content. It is one of the key parameters that have been developed and used by soil engineers for studying the properties of partially saturated soils. Currently, the SWCCs produced by most of the researchers are grounded on lab testing which is quite different from the field‐obtained curves. In the current study, the SWCCs for Karak expansive soil have been obtained from in situ testing (field). For this purpose, three sites were selected at Amberi Village (Karak) for instrumentation. An open trench of six‐foot depth was excavated in each site and instrumented. Electrical resistivity sensors (G‐blocks) and tensiometers were used for matric suction measurements. The gravimetric moisture content was measured with the help of moisture sensors calibrated with a speedy moisture meter. To check the fluctuation of moisture and suction, these instruments were installed at three different depths, that is, 0–2, 2–4, and 4–6 feet. Based on results, the maximum suction of 705.79 kPa was observed in the site “A” in 0–2‐foot depth (near the ground surface) with a moisture content of 15 percent. The variations in suction and moisture content follow the almost same trend at low suction; however, the trend was slightly different at the moderate suction range. The measured suction showed a strong correlation with the free swell index (FSI) and moisture content. It was found that the upper layers of expansive soil have high suction than lower layers due to more exposure to the environmental agencies and low density.

Measurement of soil suction in expansive clays

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.

Expansive soils have large volume changes due to the variation of water content. Therefore, expansive soils are also known as problematic soils due to its expansive nature. The black cotton soil has very low bearing capacity, high plasticity, high compressibility, low permeability and high swelling and shrinkage properties due to the presence of montmorillonite mineral. Due to these properties, black cotton soils are problematic soils. Therefore, it is necessary to improve its properties by using soil stabilization method. This study aims at conducting stabilization of black cotton soil of Bharuch region in Gujarat state by using combination of two soil stabilizing agents: copper slag and groundnut shell powder. In this research, copper slag is added 5% and 10% and groundnut shell powder is added 2% and 4%, respectively. The research gives comparison between the soil properties of non-treated and treated black cotton soil. Various laboratory tests are carried out such as specific gravity, liquid limit, plastic limit, shrinkage limit, free swell index, standard proctor compaction test, unconfined compressive strength test for both the cases by taking IS:2720 as reference. These laboratory tests results can be helpful to engineers to carry out soil stabilization on field during construction.

Due to intense moisture fluctuations, expansive soil subgrades exhibit swelling and shrinkage behavior which results in the damage of lightweight structures such as pavements, single storied buildings etc. resting on them. Frequently, lime or cement is used as a stabilizer to improve the expansive soils. In addition, low calcium based stabilizers such as fly ash, grounded blast furnace slag etc. have been promoted to treat the expansive soils. In this study, an attempt has been made to study the influence of addition of fly ash on the dynamic properties of expansive soils. A class C fly ash is used to treat a moderately expansive soil having a free swell index of 50 %. A series of resonant column tests were performed to determine the small strain dynamic properties, shear modulus and damping ratio, of the untreated and fly ash treated expansive soils at different curing periods. Results indicate that with an increase in fly ash content, the shear modulus increases and damping ratio of the expansive soil decreases. In addition, with the increase in curing period there is an increase in shear modulus and decrease in damping ratio.

Expansive clay soil has high potential of swelling due to minerals content which bind water, therefore, soil improvement is required to stabilize the swelling behavior by add binder additive such as lime in deep soil mixing method (DSM). In this study, Finite Element model approach was performed with embankment provided on the top of expansive clay layer to provide bearing layer for road construction. As the deep soil mixing is applied on the subgrade (expansive clay layer), some model variation is performed such as diameter variation with 0.4m; 0.6m; 0.8m, depth variation with 5m; 6.5m; 8m and space variation 0.8 m;1.2m;1.6m; 2.4m. Area ratio parameter also used for ease understanding of deep soil mixing behavior with so many model variations provided. Analysis results shows that higher area ratio of deep soil mixing will provide lower displacement value either immediate displacement or consolidation displacement. Moreover, plot result of area ratio shows that area ratio of 0.4 provide effective value regarding consolidation displacement and duration.

Expansive soil is a form of soil that can expand and contract, changing its volume. Montmorillonite, a mineral with the ability to dissolve in water, makes up the majority of these kinds of soils, and by increasing the volume of the soil, it causes the soil to heave. Expansive soils could be a substantial concern for engineered buildings due to their capacity to adjust to seasonal variations by contracting or expanding moisture content. Many researchers focused on soils that were swollen and looked at how they behaved as well as how they could be improved. In this study, the work depends on inserting micro-piles with different depths and configuration widths to investigate which depth and configuration can be obtained to improve the bearing capacity of foundations on expansive soil. The main purpose of this study is to reinforce the expansive soil with micro-piles with different depths (1B, 2B, and 3B) and different configuration widths (under footing only, 1B and 2B). It was concluded that the soil reinforced with micro-piles improved the load-bearing capacity of the expensive soil and decreased the swell pressure. The increasing depth of the micropiles 2B to 3B (B is the width/diameter of the foundation) can increase the bearing capacity by just 6%; therefore, increasing the depth beyond 2B is not beneficial. Also, the increase in width of the configuration of the micro piles from 1B to 2B increases the bearing capacity by just 4%; therefore, the increase in width greater than 1B is not valid. Doi: 10.28991/CEJ-2024-010-01-017 Full Text: PDF