Engineering geological characteristics of basalt residual soils in Leizhou Peninsula

The basalt residual soil in Leizhou Peninsula is special regional soil. Comprehensive and systematic evaluation of engineering geological characteristics of the basalt residual soil can provide a certain theoretical support for its engineering investigation and construction. It is formed from the basalt by a long period of weathering and laterization, and the soil particles in the upper layer are smaller than those in the lower layer. Its clay mineral is mainly kaolin, furthermore, it contains more free iron oxide and free aluminium oxide. Its microstructure is mainly clot and flocculation structure, and the pores with a size of greater than 1 μm are more than 70% of the total porosity. The basalt residual soil has poor physical properties of high porosity, low density, high liquid limit and possesses better mechanical properties of high strength because of special composition and microstructure. The basalt residual soil has small expansibility, great shrinkage, insignificant tamping compatibility, and poor water resistance, and its mechanical properties are deteriorated significantly after immersion in water. And the basalt residual soil is more sensitive to the environmental factors such as temperature and humidity. The cementing materials of skeleton will dehydrate and exhibit aging in hot and wet climate, and thus their structural strength is weakened and microstructure is disturbed and damaged. The soils after immersion show serious disintegration and large collapsible deformation. Therefore, geotechnical engineers should pay close attention to engineering disasters due to strong shrinkage and meteoric water.