DISCOVERY OF SWELLING DIATOMITE AT TENGCHONG,YUNNAN PROVINCE AND ITS IMPLICATION IN ENGINEERING GEOLOGY

This paper was based on the field investigation of the typical geological sections and multiple methods of laboratory tests on the samples from the slopes along the Baoshan-Tengchong highway and adjacent area in Yunnan Province. It discovered a swelling clayey diatomite in the Neogene lacustrine strata, named Mangbang formation, at Tengchong area Yunnan Province. The clayey diatomite is belonging to a type of both light and strong swelling rock, which has double physical-hydraulic properties of both typical diatomite and swelling clay rock. The former include high porosity, high water absorption capacity, and very strong structure, the later include high plasticity, outstanding swelling and disintegration properties, and the appearance of swelling property mainly connected with the contents of organic matter. The discovery of the swelling clayey diatomite in Mangbang Basin, as well as the researches on its engineering properties, is not only instructive for realization of the mechanism of related geo-hazards along the Baoshan-Tengchong high way, but also helpful to understanding the engineering properties of some lacustrine deposits and their easily causing geo-hazards in southwestern China.