Side Of Optimum Moisture Content Research Articles

WITHDRAWN: Pullout Capacity of Piles in Unsaturated High Plasticity Clayey Soil: An Experimental Model Study

Unsaturated soils exhibit distinct physical and mechanical characteristics compared to dry or saturated soils. Ignoring the influence of unsaturation (matric suction) and assuming either dry or saturated conditions can lead to unreliable predictions of pile behavior in unsaturated soils. In this study, the pullout capacity of different physical model piles driven in an unsaturated Kaolinite-Bentonite matrix is investigated. A series of lab-scale pullout tests were carried out to examine the influence of matric suction, pile type, pile L/D ratio, and undrained cohesion (cu) of soil on the ultimate pullout capacity of model piles. Soil samples were prepared and compacted in a tank, and holes were created using a pile. Four model piles (solid and hollow stainless steel) were driven into the holes, ensuring proper spacing. Incremental loading was applied until the piles slipped out, with displacement measured by an LVDT. The pile pullout capacity increased with increased matric suction and undrained cohesion. The uplift capacity increased by 50 % to 136% as matric suction increased by 157.97% as the compaction state was changed from 0.95 γd(max) on the wet side of optimum moisture content (OMC) to 0.95 γd(max) on the dry side of OMC of the compaction curve. However, for the compaction state of 0.90 γd(max), the matric suction increased by 398.80%, leading to a 275% to 800 % increase in the uplift capacity. As the cohesion of the five samples increased from 17.84 kPa to 137.84 kPa, the uplift capacity of all the model piles increased. In Kaolinite-Bentonite mixes compacted on the dry side of OMC, hollow model piles resisted higher pull-out loads than solid model piles. The increase in uplift capacity was found to be in the range of 11.11% to 75% for different combinations of pile type and compaction density (matric suction). The results from the study imply a strong influence of matric suction, undrained cohesion, L/D ratio, and pile type on pullout capacity for piles driven in unsaturated Kaolinite-Bentonite mix.

Influence of matric suction on resilient modulus and CBR of compacted Ballina clay

Road infrastructure is often built above the groundwater table. The materials used are usually compacted and thus generally remain under unsaturated conditions throughout their service life. This paper presents experimental results that highlight the influence of matric suction on the resilient modulus (MR) and California bearing ratio (CBR) of a compacted subgrade Ballina clay (typically found in NSW, Australia). The soil specimens were prepared in a range of water contents and dry unit weights, tested using a series of repeated load triaxial tests and CBR tests, and the associated matric suction was measured using the filter paper method. The tests were complemented by the study of the macrostructure of the compacted specimens using X-ray computed tomography (CT). Test results show that there are intimate relationships between the soil suctions and resilient modulus as well as CBR on the compacted clay at different moisture contents and that both parameters can be defined empirically through matric suction. A linear trend was established between matric suction and MR with a high coefficient of correlation of 0.99. CT scan results reveal that increasing soil moisture increased the inter-pores volume and the aggregations became more compressible and present probable matrix-dominated macrostructure during compaction. While soils compacted at the dry side of optimum moisture content yield distinct aggregations owing to the flocculation and aggregation of soil structure.

Correlating unsoaked CBR with UCC strength for SC and SP soil

Most of the civil engineering structures are constructed on the ground and are supported by soil strata or rock strata present at the site. As soil is heterogeneous, its properties vary from one place to another within a distance of few meters. Thus it is tough to predict the behavior of soil without studying its engineering properties in detail. One of the important laboratory test that is generally conducted for the flexible pavement design is California Bearing Ratio (CBR) test. CBR test is a laborious and time consuming process and may lead to delay in execution of construction projects and thus cause increase in construction costs. Thus an effort has been made to correlate unsoaked CBR value of soil with the UCC strength of soil by Simple Linear Regression Analysis (SLRA) so that based on the UCC strength of soil unsoaked CBR value of soil can be predicted. In this project, 2 types of disturbed soil samples were collected from in and around Chennai region and were classified as Clayey Sand (SC) and Poorly Graded Sand (SP) based on the index properties of each soil. Unconfined Compression (UCC) test and unsoaked CBR test were conducted on the two soil samples by varying the moisture content (MC), to determine whether the maximum strength gain was observed on the dry side or wet side of optimum moisture content (OMC) and to study the extent of increase in UCC and CBR strength compared to control specimen (CS) prepared at OMC. From the results, it was observed that maximum strength gain was attained on the dry side of optimum.

Improvement the california bearing ratio of expansive subgrade using SiCC column

In Indonesia, many main roads have been constructed on problematic soil. The chemical improvement is widely used to shallow soil modification and stabilization. This paper introduces the use of a SiCC column to strengthen the load-bearing capacity of the expansive soil. In the road pavement design, California Bearing Ratio (CBR) is a most useful parameter to define the pavement layers. Hence, this paper is aimed to investigate the effect of SiCC column on the CBR of compacted expansive soil. Two groups of specimens were prepared for CBR test under soaked condition. A set of specimens are prepared on the wet side (Specimen A), and a set of specimens are compacted on the dry side of optimum moisture content (Specimen B). The objective of this research is to determine the effect of moisture content and dry density on the CBR value. The experiment results show that the SiCC column significantly increases the CBR of expansive soil on both dry and wet side of optimum moisture content. The specimen compacted on the dry side exhibit a higher CBR than the specimen compacted on the wet side of optimum moisture content.

Influence of Molding Water Content on Shear Strength Characteristic of Compacted Cement Kiln Dust Treated Lateritic Soils for Liners and Covers

A laboratory investigation was carried out to determine the shear strength characteristics of compacted cement kiln dust treated lateritic soils for use in liners and covers with up to 12.5% cement kiln dust by dry weight of soil. Specimens were prepared at molding water contents of -2, 0, +2 and +4% of the optimum moisture content at the compactive energy levels of the British standard light (BSL), West African Standard (WAS) or “intermediate” and British standard heavy (BSH). Specimens treated with cement kiln dust met the minimum UCS value of 200 kN/m 2 requirement. Generally, the recorded UCS values for lateritic soil – cement kiln dust mixtures produced satisfactory UCS values for all the compactive energy levels considered. However, due to the unavailability of water to meet the hydration demand of the cement kiln dust pozolana no significant improvement in UCS values was recorded beyond 2.5% for cement kiln dust treated specimens compacted at BSH energy level and especially on the dry side of optimum moisture content. http://dx.doi.org/10.4314/njt.v34i2.8

A study on the behavior of the compacted bentonite in the presence of salt solutions

Wastes that are generally disposed off in an engineered landfill disposal site produce leachates. These leachates, which are very toxic in nature, once come in contact with percolating rain water, move downwards and pollute the ground water source. In order to prevent the ground water being polluted from the leachate, a liner is provided below the landfill disposal site. Generally, a compacted layer of bentonite is used as a barrier material at the waste disposal site. Because of its high swelling capacity and lower hydraulic conductivity, bentonite is used as a liner material. However, when bentonite comes in contact with salts present in leachates, its swelling property and hence also its hydraulic conductivity change. In this study, the effects of two different salt solutions, i.e. NaCl and CaCl2 by varying concentrations on bentonite were experimentally investigated. Tests were carried out to study the swelling potential, swelling pressure, and hydraulic conductivity of compacted bentonite. In order to study the effect of initial water content, study was carried out on two compacted samples varying in initial water content. Results indicate that liquid limit, plasticity, swell potential, and swell pressure decrease and hydraulic conductivity increases with increase in salt concentration. Result also shows that initial water content has a marginal effect on swelling pressure. However, the samples compacted on the dry side of optimum moisture content (OMC) exhibited a higher swelling pressure in comparison to the samples compacted at OMC.

Delineation of compaction criteria for acceptable hydraulic conductivity of lateritic soil-bentonite mixtures designed as landfill liners

In current geoenvironmental practice, design engineers usually require that soil liners in waste landfills be compacted within a specified range of water content and dry unit weight. This specification is based primarily on the need to achieve a minimum dry unit weight for factors controlling the performance of compacted soil liners most especially the hydraulic conductivity, k. In this study, lateritic soil treated with up to 10% bentonite, prepared at various compaction states (dry of optimum, optimum and wet of optimum moisture content) was compacted with four compactive efforts (i.e., the reduced British Standard Light, British Standard Light, West African Standard, and British Standard Heavy) to simulate the range of compaction energies expected in the field. Prepared soil mixtures were permeated with water and specimens that yielded the permissible limit of k ≤ 1 × 10−9 m/s were enclosed in an envelope (known as the acceptable zone) on the water content–dry unit weight curve. It was observed that compaction conditions resulting in moisture content slightly wet of optimum led to the lowest values of k and that the shapes and boundaries of the acceptable zones gradually increased in extent, shifting to wet side of optimum moisture content as the bentonite content increased to 10%. This approach provides good control over the quality of compacted soils and has great potential for field application.