Abstract: The under-construction Kunming-Tangdian Expressway passes through the basalt and tuff formations of the first to third sections (P_2e¹-P_2e³) of the Permian Emeishan Formation. The project is mainly pavement engineering. The basalt and tuff have great differences in rock mineral composition, structure and structure. Basalt has developed columnar joints and is filled with clay and chlorite. The physical and mechanical properties of the structural plane are poor. The secondary clay and zeolite, with the physical and mechanical characteristics of swelling potential and strong water sensitivity, constitute the weak interlayer in the basalt stratum. During the construction, many slope deformations occurred in the basalt section of the Emeishan Formation, which mainly occurred in the riverside area, followed by the slope area. The circular sliding mode in the shallow soil layer is the main type, followed by the wedge failure mode in the rock layer. The formation lithology mainly occurs in tuff and basalt are second, and the slope deformation is mainly affected by factors such as poor physical and mechanical properties of tuff, unfavorable structural plane, groundwater action and steep slope rate.

Key words: Kun-Tang Expressway, Basalt of Emeishan Formation, Engineering Characteristics, Slope Deformation