Clayey Subgrade Soils Research Articles

Measured effects on engineering properties of clayey subgrade using lime–Homra stabiliser

The engineering properties of clayey subgrade soils may need to be improved for suitability in construction using appropriate stabilisation methods. Stabilisation of pavement subgrade soils has traditionally relied on treatment with lime, cement and sometimes special additives, which are regarded as waste materials. Alternatively, the Egyptian bricks/ceramic industry generates large amount of calcined-clay waste or crushed clay bricks (known as Homra). In this study, standard laboratory soil tests were conducted to measure changes in the engineering properties of clayey soils when treated with a lime+Homra (L+H) blend. Tests were conducted on untreated control soil samples and on varieties of treated samples with L+H ranging from 1% to 11% for lime and 5% to 15% for Homra. The results showed that the L+H clay samples exhibit low plasticity, swelling, maximum dry density and consolidation settlement. On the other hand, results showed a significant increase in California Bearing Ration, soil cohesion and soil strength. The internal friction angle concerning shear strength parameters is also enhanced. It can be summarised that engineering properties of clayey soils can be enhanced using lime and Homra. This is advantageous for work construction in the civil engineering field.

THE INFLUENCE OF WASTE CONSTRUCTION MATERIALS USAGE ON HIGHWAYS SUBGRADE LAYER

Now-a-days disposal of different wastes materials produced from different industries is a great problem. These materials pose environmental pollution in the nearby locality. Their potential for use in the construction of highways suggests that valuable benefits in terms of economic and environmental gains are possible. Two types of wastes materials, rice husk and sawdust were used to improve the properties of the clayey subgrade soil. A procedure was adopted to quantify the beneficial effect of subgrade soils stabilization benefits which base on the extension of pavement service life and reduction in the base course thickness. Results show that both types of wastes materials helps in great improvement of soil properties as California bearing ratio and unconfined compressive strength to use in the construction of highways

Strength Characteristics of Clayey Sub-Grade Soil Stabilized with Fly Ash and Lime for Road Works

In this paper an attempt has been made to improve the strength properties of clayey soil (near NH-6, Burla of Sambalpur, Orissa, India) to be used as sub-grade by using locally available fly ashes as admixtures with lime. It is observed that addition of 3 % lime along with 30 % fly ash by weight of virgin soil showed a remarkable improvement in the California bearing ratio (CBR) values. The soaked (after 4 days soaking curing) CBR value of virgin clayey soil found to be 2.3 %. On the other hand, soil mixed with 30 % fly ash and 3 % lime by weight, the soaked CBR increased to 55.8 % after 8 days moist curing in air with additional 4 days soaking (total 12 days curing). Further it was observed that soil mixed with 30 % fly ash and 2 % lime, the soaked CBR increased to 48 % after same total 12 days curing, which was 21 times of CBR value of virgin soil. Also the modulus of elasticity of 70:30:3 mixes was found to be 230.87 MPa for sub-grade and 501.03 MPa for sub-base of road, where as that of only soil was found to be 24.64 MPa as sub-grade and 53.47 MPa for sub-base respectively. Some other mixes also showed promising values.

Improving fine-grained gypsiferous soil by increased compaction

Presented in this paper is a study of the effect of compactive effort (CE) and long-term soaking on the strength characteristics of a clayey gypsiferous subgrade soil. The tested soil is A-6 (6) soil according to American Association of State Highway and Transportation Officials (AASHTO) soil classification system. To study the effect of CE and long term soaking on the properties of the tested soil, various California bearing ratio soil samples were prepared and compacted at optimum moisture content of the modified AASHTO compaction, but using four different chosen CEs of 12, 25, 56 and 70 blows/layer and then soaked for 0, 4, 7, 15, 30 and 120 days. The California bearing ratio (CBR) tests indicate that the CBR increases significantly in a nonlinear manner with increasing CE for all soaking periods, indicating improvement in soil strength with increased compaction. The rate of increase dies out with increasing CE. The CBR tests reveal also that there is a serious drop in the CBR due to soaking for all CEs.

Resilient Modulus of Cohesive Soils

Resilient modulus tests were performed on three clayey subgrade soils with repeated-loading triaxial test equipment. For the laboratory-compacted samples, stress at 1% axial strain from the conventional unconfined compression test (Su1.0%) was found to be a good indicator of the resilient modulus (MR). An empirical correlation between laboratory-compacted MR and Su1.0% was developed and was found to be applicable for the different cohesive soils tested. Data suggest that the MR and Su1.0% relationship applies to field-compacted specimens as well.

SIGNIFICANCE OF THIXOTROPY IN BEARING VALUE OF COMPACTED CLAYEY SUBGRADE

The reduction in strength of clayey subgrade soils under pavement was obserbed, when the subgrade soil was remolded at the equal water content. This result means that the strength of compacted clayey subgrade increases with time. It is due to thixotropy of clayey soil. The thixotropic effect should be considered when strength of subgrade or specimen immediately after compacting is used for deciding the design strength of the clayey soil. This paper deals with the increment of strength on remolded clayey soil for determination of design strength.