Study on the Determination of Residual Shear Strength for Expansive Soil

Generally, it is very difficult to obtain the undisturbed soil and keep it in the undisturbed state in practice. In this paper the residual shear strength of Grey-white expansive soil of Ningming was studied based on the analysis of the influencing factors of residual shear strength of expansive soil. The test results of undisturbed samples, compacted samples and samples prepared by static compaction conducted by strain-controlled repeated direct shear test were compared, which show that the differences of the peak shear strengths are very large but the differences of the residual shear strengths are very small. By the comparison and analysis of the test results, it is more reasonable and practical to use the residual shear strength of static compaction sample to represent that of undisturbed sample. Therefore, the residual shear strength (c=10.53 kPa, φ=11.55°) of samples prepared by static compaction can be taken as that of Ningming Grey-white expansive soil.