Expansive Clay Soils Research Articles

Effect of Lime and Fly ash on Load Bearing Capacity of Expansive Clay soil

Expansive soil is a problematic soil which found in wide part of the world that has a high degree of sensitivity, nature of expansion and shrink behavior during water adding and removing this caused insufficient bearing capacity, excessive differential settlement and instability on excavation and embankment forming those conditions accelerate damage of building structure, road highway and dam. Attempt to undertake construction in such type of soil result will be bearing capacity failure, settlement problem. One of the well-known application of Lime and fly ash were improve Atterberg limits, compaction characteristics, bearing capacity and prevention of swelling problem of expansive clay that is why the main reason to select lime and fly ash in this project, both are good binding material to increase the cohesion force and shear strength of soil and assured to established rigid pavements and foundations. The mixing proportion of lime, fly ash and combination of lime and fly ash are (0%, 2 %, 4 % ), (10%, 15% ,20% ), (2 %+10 %, 2 % +15 %, 2 % +20 %) and (4 %+10 %, 4 % + 15 % , 4 %+ 20 %) with expansive soil respectively and then explored how much it modify the characteristics of soil like maximum dry density moisture content, consistency limits, FSI, UCS and CBR value which compare to untreated soil. Lime and fly ash treated soil carried out various tests Such as Moisture content test, consistency limit, compaction test, Unconfined Compression swelling index test and California bearing ratio test then after justify weather the bearing capacity of soil is good or not . Classification of soil was determined by conducting plasticity index and swelling index tests. Effect of lime and fly ash on soil index properties were assessed by conducting Atterberg limits test, strength of soil were assessed by conducting compaction test, UCS tests and CBR test and swelling properties were checked by conducting swelling index test. Expansive clay soil were mixed with lime, fly ash and combination of lime - fly ash by replacement process of soil and then cured for 7, 14 and 28 days.

ANALYZING THE CHARACTERISTICS OF LANDFILL LEACHATE ON EXPANSIVE SOIL AND ITS IMPACT ON LINER MATERIALS REINFORCED WITH DISCRETE RANDOM FIBERS

This research work is an insight into the various properties of liner materials utilized in landfill sites to control the leachate. Although expansive clay soil is inorganic, it is problematic. The soil owes this aspect to erratic fluctuations in its behavior due to the movement of water. Urbanization, increase in population and industries generate enormous amounts of waste in different forms. Disposal of these wastes in the landfill without any scientific manner creates a major problem to the surrounding soil and groundwater. In this study, an attempt was taken to identify the effect of soil properties and groundwater quality due to the continuous generation of leachate in the dumping sites. To prevent such an environmental problem, highly impermeable sand–bentonite mixture is used as a liner material in the waste disposal sites. Therefore, various mixtures of sand–bentonite were prepared by varying sand contents and different sieve sizes, i.e. 2–0.075[Formula: see text]mm; 2–0.425[Formula: see text]mm and 0.425–0.075[Formula: see text]mm were used. And also to improve the strength and hydraulic conductivity of the liner materials, discrete random fiber is mixed with various proportions to these mixtures and examined.

Desiccation-Induced Volumetric Shrinkage Characteristics of Highly Expansive Tropical Black Clay Treated with Groundnut Shell Ash for Barrier Consideration

Contamination of underground water as a result of excessive crack on clay liner material is a prevalent phenomenon in an engineered landfill. Volumetric shrinkage strain (VSS) is one of the veritable properties considered for selection of materials suitable for liners and cover in waste containment systems. Material devoid of excessive shrinkage and cracking during climate change could possibly make a better barrier material that will eventually limit or control infiltration of leachate in an engineered landfill. Hence, to obtain a clay liner and covers system that are safe and robust, stabilization of such soil (expansive clay soils) becomes imperative. In order to stabilize or reduce excessive cracking and shrinkage of this soil, earlier researchers have employed cement, chemicals, and fibers. However, in recent times, the ill effects of these stabilizers on the environment have been realized, and hence their replacement with sustainable materials that are mostly agro and or industry by-products is becoming necessary. Tropical dark grey clay treated with up to 8 % Groundnut shell ash (GSA), was carried out. Specimen were compacted using British standard light (BSL) and British standard heavy (BSH) compactive efforts; at water contents between 2% dry and 4% wet of optimum. The compacted specimens were extruded and subjected to drying under laboratory conditions to evaluate its desiccation induced shrinkage and hence its suitability as a cover material in waste containment facilities. Results of this study show that changes in mass and volumetric shrinkage strain were large within the first five days of drying. Volumetric shrinkage strain increased with higher moulding water contents (MWC) and water contents relative to optimum (WRO). The effect of GSA treatment on VSS was not consistent from -2 to +2 % of optimum moisture content. For specimen prepared at +4 % of optimum moisture content, VSS decreased up to a threshold of 28% at 6 % GSA and 30% at 4% GSA for BSH and BSL compactive effort, respectively. Generally, lower compactive effort (BSL) with higher moulding water content and lower dry density produced higher VSS. A regression function was developed from the data to estimate VSS given the compaction water content relative to optimum (WRO), groundnut shell ash content (GSA), plasticity index (PI), percentage fine content (PF) and compactive effort (CE). Compaction water content relative to optimum significantly correlated with VSS, thus should be strictly regulated during field compaction to realize a durable hydraulic barrier. Keywords: Atterberg limit, compaction, desiccation, expansive soil, groundnut shell ash, statistical analysis DOI : 10.7176/CER/11-8-06 Publication date :September 30 th 2019

Coupled Effect of Wet-Dry Cycles and Rainfall on Highway Slope Made of Yazoo Clay

Expansive Yazoo clay soil is susceptible to volumetric deformation and is dominant in central Mississippi and other neighboring southern states of the United States. Recurring shrink-swell behavior causes a significant problem to infrastructures in the area. Although Yazoo clay causes a significant problem in the deep southern states, limited study has been conducted on the behavior of Yazoo clay, especially in the presence of rainfall. The objective of this current study is to investigate the coupled effect of changes in void ratio due to wet-dry cycles and rainfall on the stability of highway slopes made of Yazoo clay. The finite element method in Plaxis 2D by Bentley System (https://www.plaxis.com/) has been utilized to investigate the coupled effect of changes in mechanical properties and rainfall using flow-deformation and stability analysis. Reconstituted expansive clay soil samples were used for the laboratory experiment. The reconstituted Yazoo clay samples were subjected to 3, 5, and 7 wetting and drying cycles in an enclosed chamber for a 24-h period. The axial deformation of the samples and the change in void ratios at each number of the cycle was closely monitored. The strength change at each wet and dry cycle was also investigated and used for slope stability analysis in the presence of rainfall. The test results indicate that the void ratio increases with the increasing number of wet-dry cycles. A continuous increment in void ratios from 0.99 in an undisturbed state with no wet-dry cycle to 1.49 at the 7th wet-dry cycle, indicating a 48.9% increase, as the wetting and drying cycle increases was recorded; in turn, decreasing the cohesion of the soil by 77%. The factor of safety considering the effect of two total rainfall periods of Rv = 126.2 mm (2 h) and Rv = 271.7 mm (3 days) reduced from 1.7 to 1.2 and 1.68 to 1.02, considering the effect of the 7th wet-dry cycle at the topsoil. The changes in the void ratio due to the wetting and drying cycle of Yazoo clay soil reduces the shear strength to a fully softened condition, increasing the possibility of slope failure. This condition further worsens in the presence of a perched water condition due to the infiltration of rain water.

The Performance of Shear Strength and Volume Changes of Expansive Soils Utilizing Different Additives

Some clayey soils are generally classified as expansive soils which cause extensive damage to civil engineering structures due to change in its water content and the amount and type of clay size particles. Other important factors affecting the expansion behavior include the amount of non-expansive materials. This paper based on comparing two solutions to improve the soil parameters: the first solution to improve the soil with steel fiber and the second solution to improve the soil strength and volume changes with plastic waste material. Various tests conducted to study the effect of using different percentages of steel fiber and plastic waste material (4%, 8% and 12%) for each additives by dry weight of soil. The results presents that the steel fiber and plastic waste material significantly improved the soil strength and volume changes besides the physical properties of expansive clay soil which have susceptibility of swelling.

EFFECT OF ADDING POLYACRYLAMIDE POLYMER WITH LIME AND CEMENT KILN DUST ON THE PROPERTIES OF EXPANSIVE CLAYEY SOILS

Using additives like chemical materials have been determined to be an important procedure forimproving some properties of expansive soils. The present work had attempted to study the influence of addingvarious percentages of Polyacrylamide (PAM) polymer on the clayey expansive soil properties mixed withlime (L) and finely divided particulate Cement Kiln Dust (CKD), which is collected during the production ofPortland cement. The properties are investigated under the influence of adding many percentages ofPolyacrylamide polymer (i.e., 1%, 3% and 5%) with lime and cement kiln dust mixture of (3% lime and 8%cement kiln dust). The Atterberg limits, compaction, swelling potential, unconfined compression strength(UCS) and California Bearing Ratio (CBR) tests are carried out on the prepared samples. The results showedthat addition of Polyacrylamide (PAM) polymer with (LCKD) has improved expansive clay soil propertiesmore than adding (LCKD) alone. The optimum percentage for (LCKD-PAM) that achieves the lower free swellvalue and the maximum UCS and CBR values is at (3% L+8% CKD +5% PAM) which shows reducing in freeswell by about 94.5%, increasing in UCS worth by about 262% and 400% for curing period of 7 and 28 daysrespectively and improving CBR value to 27 from 5.45.

Experimental and Numerical Investigations of Influence on Overland Flow and Water Infiltration by Fracture Networks in Soil

Preferential flow is common in clay or expansive clay soils, involving water bypassing a large portion of the soil matrix. Dye tracer experiment and numerical modeling are used to simulate the surface runoff and subsurface preferential flow patterns influenced by the soil fracture network of a relatively steep hillslope system (slope angle equals to 10 degrees). The result of the experiments indicates that part of the water is infiltrated through cracks, leading to the delay of the initial runoff-yielding time and reduction of the discharge of the surface runoff. The soil water flow is mainly in the matrix when the intensity of precipitation is low. With the increasing of precipitation, soil water movement may become in the form of preferential flow through cracks. In addition, the nonuniformity of soil water infiltration and the depth of the average water infiltration increase as the precipitation intensity increases. To this end, the complete coupling model was established by using the surface-matrix-crack (SMC) model to simulate water flow within discrete fracture as well as to simulate water flow in the soil matrix based on the concept of dual permeability using the traditional Richards’ equation. In this model, the “cubic law” of fluid motion in cracks within smooth parallel plates and the two-dimensional diffusion wave approximation to Saint-Venant equations with momentum term ignored (two-dimensional shallow water equations) were used. The model divides soil water infiltration into two forms and uses the overall method to calculate the exchange of water between the crack networks and matrix regions as well as the exchange water between surface runoff and infiltration water. Results indicate that the SMC model has better performance compared with the traditional equivalent continuum model when those models are used to simulate the surface runoff movement and the soil water movement in the presence of cracks.

Pengaruh Penambahan Abu Ampas Tebu dan Kapur Terhadap Karakteristik Tanah Lempung Ekspansif (Studi Kasus : Tanah di Bojonegoro)

In each region having different types of soil, one type of soil is expansive clay. In Indonesia, more than 1/5 of the land area in Indonesia are an expansive clay. This type of soil will affected by changes in water content and experience significant shrinkage. Therefore, to improve the soil and minimize shrinkage growth, an effort is needed, one of which is soil stabilization. Physical testing of soil with soil samples in the district Ngasem, Kab. Bojonegoro which is expansive clay soil shows that the CBR value is 3.953%, and the swelling value is 6.1858%. With such physical conditions with low carrying capacity it is necessary to stabilize the soil on clay in Bojonegoro. Stabilization efforts carried out are by chemical stabilization by mixing soil samples with additives in the form of bagasse and lime ash. The results of the physical soil test from the preliminary research conducted by the author by mixing bagasse ash in the soil with variations in levels of 8%, 10%, 12%, 14% showed a mixture of 8% bagasse ash was the optimum level for repairs to the soil. So it is used a mixture of 8% bagasse ash with the addition of variations in lime content of 4%, 6% and 8% of the total weight of the mixture. A mixture of 8% bagasse ash and 6% lime content produced a CBR value of 9,324%, this CBR value increased to 135.87%. While the swelling value is 0.1681%, with the same mixture level. This swelling value decreased to 97.28%. For the value of free development it decreased to 217.7% from the previous one which amounted to 70.59% to 22.22%.

PENGARUH PENAMBAHAN SERBUK CANGKANG KEONG TERHADAP NILAI CBR TANAH LEMPUNG EKSPANSIF

n this research, soil improvement is done by using waste of snail shells (LCK) in Desa Ulak Kembahang II, Kecamatan Lubuk Keliat, Kabupaten Ogan Ilir, Sumatera Selatan and soil from Tanjung Api-api Area, Gasing , Kabupaten Banyuasin, Sumatera Selatan . The soil used is a type of problematic soil that is expansive clay, which is known LL value (Liquid limit) more than 35%. The LCK used is then used as powder. Furthermore, there are 5 variations of percentage of addition of snail shell powder (SCK) with soil, and give the curing time is for 0, 1 and 7 days. Results from CBR Unsoaked (US) Testing resulted in the addition of SCK at a certain percentage and the curing time could increase the value of CBR expansive clay soil. The highest value of CBR Unsoaked on variation of percentage of SCK increase as much as 11% in the curing curing time for 7 days that is equal to 5.6% for the value of CBR US which in the original land has a CBR value of 3.5%. The result analysis of SEM-EDX test on soil mixture and SCK known SCK works as filler which fill the cavity found in soil grains and the main element of soil known as SiO 2 and Al 2 O 3 forming binder material with CaO.

Stabilization of Niger Deltaic Expansive Clay Soils Using Composite Materials

The study examined the hybridization effect of irvinga gabonesis fibre (Bush Mango) ash and cement as composite materials in the modification of weak expansive clay soils found in Iwofe, Chokocho, Ndoni, and Ogbele town roads in the Niger Delta region of South-South part of Nigeria. Preliminary test carried out classified as A – 7 – 6 /CH on the AASHTO classification schemes / Unified Soil Classification System. The soils are dark grey in color with the plastic index of 31.10%, 24.55%, 31.05%, and 32.17% respectively. Experimental results analyzed showed increased in compaction test parameters of MDD and OMC with the increase in additives corresponding percentage ratio to clay soils. Results of unstabilized and stabilized results showed increased values with respect to corresponding percentages with the optimum inclusion of 7.5% + 7.5% to soils ratio. Results showed decreased in plastic index parameters with additives inclusion to soils. Comparative results showed increased in the unconfined compressive strength of stabilized clay soils with respect to the percentage. Entire results showed the use of irvinga gabonesis fibre (Bush Mango) ash and cement as soil stabilizer products.

Malaysian Experiences of Peat Stabilization, State of the Art

Peat has been considered as an organics remnant that suffers decomposition process throughout times under overburden pressure. Composition of peats normally consists of organics materials which sometimes exceed 75% specifically from woods that grows in marshes and places in conditions where deficiencies of oxygen exist. Usually peat area related with swampy and normally a low shear strength region. High compressibility is significant and often related to problematic soil for construction purposes. In this article, extensive number of studies are reviewed to understand the behavior of the peat after being stabilized. New findings indicated that the peat contents differs from one location to another, thus inevitably gives different behavior. Many improvisation methods have been put forward such as chemical stabilization, cement stabilization, deep mixing and fiber reinforcement to name a few to enhance the strength properties of the peat. This is mainly for construction reliability purposes. However, the suitability of the ground improvement for peat thus depend on its fundamental properties and cost involve for any dedicated ground construction work. This paper review the properties of peat in Malaysia and reviewed recent development in the peaty soil stabilization in Malaysia. It is also compared the materials used for the peat stabilization and the expansive clay soils as the main two problematic soils.

Lime-stabilisation of high plasticity swelling clay from Ethiopia

In the present study, highly expansive clay soils from the Highlands of Ethiopia were studied to evaluate the efficiency of lime treatment to improve their mechanical properties for road subgrades. Soils treated with quick lime at 5, 7 and 9% by dry weight of the soil were cured for seven days under controlled temperature of 40 ± 2 °C and geomechanical laboratory tests were conducted to evaluate its impact on the engineering properties of the soil. Test results show substantial improvements in the properties of the soil after lime treatment. Addition of lime significantly reduces the plasticity index and swelling potential of the soil. Similarly, despite the reduction of optimum proctor dry density due to lime treatment, the unconfined compressive strength and the California bearing ratio show considerable improvements. Based on the current study, expansive soils of the studied area can be effectively stabilised for road subgrade works with the addition of 7% quick lime by dry weight of the soil. For very problematic soil, as the one investigated here, the drastic reduction of swelling potential is of particular interest for a possible application of road subgrade.

The Effect of Heat on the Properties of Expansive Clay Soil

The Effect of Heat on the Properties of Expansive Clay Soil

Design of Flexible Pavements on Expansive Soils

“American roads are good not because America is rich, but America is rich because American roads are good.” — John F. Kennedy. India has a road network of over 5, 472, 144 kilometres (3, 400, 233 mi) as on 31 March 2015, the second largest road network in the world. Expansive soils are typically clays that demonstrate extensive volume and strength changes at varying moisture content due to their chemical composition. The main causes of premature failures of road pavements is attributed to expansive subgrade soils and poor drainage, leading to severe cracking and heave on road surface. The amount of certain clay minerals that are present, such as montmorillonite and smectite, directly affect the shrink-swell capacity of soil. This ability to drastically change volume can cause damage to existing structures. The aim of this paper is to highlight issues of expansive subgrades & suggest some workable solutions so that highway engineers can improve design and construction methodology of pavement on expansive soils. As per a report, “Expansive clay soil causes more damage to U.S. commercial and residential property each year than all hurricanes, tornados, earthquakes and floods combined”.

Polymers for Stabilization of Soft Clay Soils

In this study, the influence of two chemical additives, (i.e., poly(vinyl alcohol), PVA and 1,2,3,4 Butane Tetra Carboxylic Acid, BTCA on the engineering properties of an expansive clay soil is investigated. The effect of polymers on the unconfined compression strength of soil samples prepared at maximum dry unit weight (i.e., 16.2kN/m3 and 17% water content) and a lower dry unit weight (i.e. 10.8kN/m3 and 48% water content) was evaluated. PVA and BTCA added at dosages of 0.1% to 1.5% and 0.1% to 0.5% respectively to both compacted soil samples and cured for 1 and 14 days. The results of unconfined compression tests on clay soil samples stabilized with different PVA and BTCA contents cured for 1 and 14 days indicated that such hydrophilic polymers improve the compression strength of both dense and soft clay soils significantly and their strength even increases with curing time. However, the efficiency of the additives is highly dependent on the unit weight of the soil. Furthermore, the durability of stabilized samples was also examined using soaking tests and results revealed that these polymers improve the durability of clay soils once they are soaked under water.

Prediction of Unconfined Compressive Strength of a Stabilised Expansive Clay Soil using ANN and Regression Analysis (SPSS)

Industrial waste stabilization is one of the common techniques used to improve the strength of weak soils as it is very difficult to find suitable soil everywhere for foundation. The strength developed by this stabilization technique depends on percentage addition of additives, soil properties and curing period. In order to reduce the time consuming process of laboratory investigation and for effective utilization of industrial waste additives, a mathematical model is developed relating the gain in strength (UCS) with the variables responsible. In this study, Artificial Neural Network (ANN) and Regression analysis (SPSS) is used for prediction of unconfined compressive strength (UCS) of clay stabilized with industrial waste namely bottom ash and Ecosand. The predictor variables used for developing the models are Curing Period, Bottom Ash and Ecosand dosages, Liquid Limit (LL), Plasticity Index (IP), and Free Swell. Based on laboratory investigations, the data's are divided into three groups based on the additives added. Regression analysis and artificial neural networks prediction showed that acceptable correlations exist between soil properties and unconfined compression strength of the stabilized clay soil. Based on analysis, artificial neural network (R2=0.978) showed closer prediction results when compared to the regression analysis (R2=0.939).

The roles of organic amendments and microbial community in the improvement of soil structure of a Vertisol

Poor soil structure is a serious problem of Vertisol which makes it difficult for agricultural workability and crop growth. Thus, improving soil structure is mandatory as it mediates a range of soil biological and physical processes. This study evaluated the roles of organic amendments and microbial community in the improvement of soil structure of an expansive clay soil, locally called as Shajiang black soil in China. Two organic amendments were straw and straw-derived biochar. Two biocides were fungicide and bactericide. Thus, this study involved 9 treatments: 1) the soil without amendment and biocide as a control, and the soil with 2) fungicide, 3) bactericide, 4) straw, 5) straw+fungicide, 6) straw+bactericide, 7) biochar, 8) biochar+fungicide, 9) biochar+bactericide. Straw amendment significantly enhanced soil respiration, microbial biomass carbon (MBC), and phospholipid fatty acid (PLFA), and hence improved aggregation (P<0.05). But biochar had no impact on soil microbial activity as well as on soil aggregation in comparison to the control (P>0.05) due to its recalcitrant nature. The fungicide application significantly suppressed macroaggregates production, which confirmed dominant positive role of fungi in aggregation. On the contrary, bactericide application did not reduce aggregation, even enhanced it by creating less competitive environments for fungi. Pearson correlation analysis between mean weight diameter (MWD) and PLFA indicated that aggregation was related to fungi (r=0.926) much closer than bacteria (r=0.453). Our study exhibited that straw amendment technique has the potential to be an option to improve soil structure of Shajiang black soil by promoting fungal abundance.

HYPER-SALINE SOLUTION OF QARUN LAKE (MAGNESIUM CHLORIDE) TO CONTROL DUST FROM UNPAVED ROADS AT FAYOUM, EGYPT

Magnesium chloride is a naturally occurring material and is extracted from salt-water in Qarun lake at the Egyptian salts and minerals Co. in Fayoum, Egypt such as those found in seawater. Magnesium chloride can be adapted and designed to provide highest efficiency depending on prevailing dust conditions, anticipated traffic, and type of soil in Fayoum roads. Dilution can also be varied to obtain the greatest possible economy and minimize environmental impact. This soil may be best treated with a Magnesium chloride. The paper includes discussion on the extent of unpaved roads, the consequences of dust, categorization of road additives, and a way to dust control. The effect of on the physical and mechanical properties of soils was evaluated in the laboratory. First, the physical and chemical properties of the soil sample were determined. Next, the swell percentage, California bearing ratio and indirect tensile strength tests were performed at different curing times on samples with and without the additive by compressing the sample to achieve particular compaction characteristics. The results show that dispersive and expansive clay soils can be effectively improved using an additive solution.

Stabilisasi Tanah Lempung dengan Mengunakan Larutan Asam Sulfat (H2so4) pada Tanah Dasar di Daerah Godong - Purwodadi Km 50 Kabupaten Grogogan

An expansive clay soil material that is composed of various minerals include kaolinite, montmorillonite and illite group. Mineral montmorilinite have the sensitivity to the effects of the water is very easy to expand and contract. High and low levels of development (swelling) and shrinkage (shrinkage) expansive clay is determined by the high and low content of montmorillonite on expansive clay granules. Because of these properties are very high content of montmorillonite often cause problems in the building. This study uses a solution of sulfuric acid (H2SO4) as a stabilizer through the compaction process Modified Proctor on OMC Proctor standard by the number of collisions each is 10 x, 25 x and 56 x, and the amount of additional water in cc on dry ground, with variations in increments of 100%, water by 90%:10% H2SO4, water by 80%: 20% H2SO4 and water by 90%: 30% H2SO4. This research was conducted testing-testing in the laboratory include: physical properties, mechanical properties. swelling pressure, swelling potential and CBR with curing and no curing. Results of the test-the test, can increase the value of physical and mechanical properties, while pergujian against swelling pressure and swelling potential is not significantly increased.

Mechanical properties of two expansive clay soils from Sudan

The mechanical responses of two highly expansive plastic alluvial soils from Sudan are reported. When wetted from their in-situ state, such soils frequently lead to damage of civil engineering structures. Disturbed samples of a black cotton clay and a more plastic red clay were collected from two locations in the vicinity of Khartoum. Intrinsic properties were established from reconstituted samples using oedometer and triaxial apparatus. Natural undisturbed block samples of the black cotton clay were obtained and tested in an unsaturated state, as found in situ. Basic characteristics of both soils are presented. Detailed information on the intrinsic properties of both clay soils was established and found to conform with Burland's earlier published framework. Shear planes formed during shearing in almost all triaxial samples and strengths reduced to post-rupture values. K0-consolidated reconstituted samples exhibited a more brittle response to undrained shearing compared with isotropically consolidated samples. Peak failure conditions can be represented by linear failure envelopes for both soils, regardless of consolidation path, although those from shearing in extension do not pass through the origin: reasons for this are discussed. Oedometer tests on the intact black clay soil indicate a high potential for swelling on wetting (volumetric strains of almost 50%), decreasing with increasing stress level (swelling pressure of about 1 MPa). Unconsolidated undrained triaxial tests on the intact unsaturated samples show increasing strength and decreasing brittleness with increasing confining pressure.