The Stability Of High Rock Slope About Penyinla Tunnel Entrance Of Lasa-Rikaze Railway And Its Treatment Scheme

The newly built railway from Lhasa to Shigatse is located at the Yarlung Zangbo Grand Canyon of Tibet Plateau, between north latitude29°～30°. The railway goes through the Yarlung Zangbo Grand Canyon, which is well-known for its steep mountains, fast-flowing waters and intense tectonic activity.The bank slope weathered serious with strong earthquake activities and high geothermal activity in Yarlung Zangbo Grand Canyon region, which causes new challenges for research on slope stability in railway engineering.Under complex conditions of railway construction, high steep slope stability problems have a direct influence on the feasibility of the engineering construction, route selection, and the investment benefit and railway operation safety in the future. Therefore the stability of high steep slope comprehensive evaluation is of great theoretical and practical significance.This paper mainly discusses the slope stability evaluation and control strategies at the Penyinla Tunnel entrance of Lhasa-Shigatse Railway in Yarlung Zangbo area and important conlusions are listed as follows:1. The patterns for slope distortion and damages are discussed. The influence of the discontinuity on the slope stability is studied by determining the rockmass mechanics parameters of discontinuity from Barton model method.2. Stereographic Projection, a qualitative method, is adopted to evaluate the stability of slope. The influence of the joint development on the slope stability is analyzed and J2, J4joint sets with dip direction towards slope are unfavorable for slope stability.3. A proper constitutive model is established and finite element analysis, a quantitative method, is adopted to evaluate the stability of the slope before and after the tunnel’s digging. Potential failure zone is determined around the tunnel excavation face due to tunnel excavation, therefore some measures should be taken during the construction.4. Slope excavation disturbance leads to slope stress redistribution and slope stress releases or transfers resulting in slope unloading rebound deforming toward the free face. Loose zone of slope excavation is calculated using finite element analysis method and control measures of safety and economy are put forward according to loose zone and relevant railway highway design specification.