Research on the correlation between the geological environmental evolution and landslides of Badong county in the Three Gorgers Reservoir

摘要

There are some ancient landslides in Badong town in the Three Gorgers Reservoir, i.e. Huangtupo landslide, Zhaoshuling landslide etc. In order to investigate the relation between the geological environmental evolution and landslides, Firstly, based on geological prospecting data of monitoring profile (300m in depth) in the town, the sedimentary environment and vertical zoning characteristics of rock mass was analyzed by tine section identification, x-ray diffraction and structure observing. Secondly, the history of tectonic activity was studied by analyzed spatial distribution of discontinuities. Finally, the formation mechanism of landslides influenced by exogenous tectonic process was presented. The results show that the Third segment of Middle Triassic Badong Formation (T2b3) is facility-sliding petrofabric. The sedimentation of T2b3 underwent a repetitious process of marine transgression and regression, which includes soft-hard alternated rock mass and multi-soft interlayer. Facility-sliding strata are mainly distributed in two kinds of sedimentary facies composed of open platform (shelf lagoon) and restricted platform (inter-tidal belt). Tectonic process resulted in consequent slope and several strikes of faults under multi-stage horizontal extrusion. Thirteen strips transfixing weak zones were formed in the T2b3 strata. Following valley cut and groundwater intenerating weak zones, the rock slope deformed, toppled, rotated and crept along the zones. The slope developed easily into the whole sliding while the faults occurred in the boundaries. The close correlation between the geological environmental evolution and landslides is suggested. The formation of facilitysliding structure during geologic period is controlling factor of landslide. The slope deformation may aggravate under long-term soak when the water level of the Three Gorges Reservoir will be uplifted to 175m.