Experimental Study on Unconfined Compression Strength of Compacted Granite Residual Soils

Abstract

Granite residual soils are often used as compacted soils in engineering structures such as pavement, embankments and backfills in Xiamen. Many geotechnical problems such as bearing capacity, lateral earth pressures and slope stability require an assessment of the shear strength of soil. Since the geotechnical properties of residual soils are impaired in contact with water, a series of unconfined compression tests are carried out on granite residual soils. Results of tests include effects of degree of compaction, moisture content, degree of saturation and cyclic wetting and drying on unconfined compression strength respectively. The increase in degree of compaction and compacting effort increases unconfined compression strength and the former greatly affects the strength. Moisture content of soils is higher than the optimum one of 2.5% for high strength and it is lower than optimum one of 2.5% for good plasticity in Xiamen areas. The degree of saturation of high unconfined compression strength normally ranges from 64% to 76%. In addition, cyclic wetting and drying causes loss of unconfined compression strength and the maximum loss commonly occurs at the first cycle and then is slowed down by the following cycles till the strength remains approximately constant.