Engineering geological properties and hazard effects of Hipparion laterite in Baoji, Shaanxi Province

Hipparion laterite extensively exists at the bottom of thick loess on the northern bank of Weihe River in Baoji, Shaanxi Province, and its physical and mechanical properties control the occurrence of landslide hazard. Through test analysis, the authors have reached some conclusions: ①Clay content of Hipparion laterite is high (generally 37%~55%), so is the content of expansive clay minerals, such as smectite and smectite/illite (the relative content is 55%~75%, and the absolute content is 21.99%~33.98%). Effective smectite content is 18.61%~27.56%, and the mean value of specific surface area ranges from 204.7m2/g to 262.9m2/g. These data indicate that it belongs to expansive clay and it is physically and chemically active; ②The Hipparion laterite is characterized by pre-existence of microfissures and poor cementation as well as easy disintegration. It is gumbo under natural state, but presents plastic/soft plastic state when saturated and significant expansibility; ③Natural intensity of Hipparion laterite is relatively high. Its cohesion and internal friction angle are reduced obviously when it is saturated, and the decreasing amplitude of peak intensity and residual shearing strength is 47%~63%. Therefore, the strength of Hipparion laterite will be reduced obviously under the effect of underground water; and it will turn into weak strata on high and steep slope and form the shear zone to control the development and distribution of landslides in loess tableland area of Weibei.