Seismic Dynamic Response and Instability Mechanism of Slopes in Nyingchi-Bome Section of G318 Highway, Tibet

Strata structures and dynamic responses of slopes are significant factors in slope failures. In order to elucidate the dynamic response differences and dynamic response patterns of slopes with different stratum structures, a numerical simulation model of slope with Kobe seismic wave is established in FLAC3D to analyze typical slopes of four types of strata structures in the Nyingchi-Bome section of G318 highway, Tibet. Through this model, dynamic responses of strain, horizontal displacement and acceleration at the monitoring points located in different parts of slopes (on slope surface and in slope body) are calculated and analyzed under the Kobe seismic wave. Results show that in the soil-rock slopes, the amplification factor of peak ground acceleration (PGA) on the slope surface increases with slope height and reaches a maximum at a certain height. The PGA amplification factor of the slope body increases linearly with slope height, with a maximum value of 10.7, and is bigger in phyllitic slopes than other type of slopes. The horizontal displacements of slopes on both sides of the rock-soil contact zone show great differences between soil and rock, even to nearly one order of magnitude. The deformation inconsistency caused by horizontal displacement is the primary reason for sliding in the rock-soil contact zone. Moreover, the horizontal displacement and PGA amplification factors for different soil slopes are obviously different, and the instability of soil-rock slopes is chiefly controlled by soil textures.