Under The Complex Geological Condition Of Large Span Tunnel Portal Slope Stability Research

With the growing prosperity of China’s socio-economic, infrastructure investment hasgradually expanded. Tunnels and highways and other projects is to support the main drivingforce behind China’s national economic growth, while the stability of the tunnel entranceslope is related to the tunnel project can be smoothly carried. In addition, the surroundingrock of tunnel entrance level, with complex geological conditions, prone to landslides,avalanches and other phenomena. Therefore, the stability of the tunnel entrance slope isparticularly critical.This article take the Zhejiang Lishui Bay Road Tunnel Portal slope as the researchbackground, the combination of domestic and foreign literature, the slope stability analysismethod to carry on the simple elaboration, summarized the effects of slope stability of severalmajor factors, summed up the slope of the main destroy form, and the slope failuremechanism of the corresponding theoretical analysis. Combined with engineering, examplesand literature comparison, summed up the main basis of slope deformation and failure.Combination of geotechnical material strength properties and constitutive relation, incomparison with a variety of constitutive model of rock and soil foundation, is used for finiteelement calculation of the incremental elastoplastic constitutive relation of matrix expression.taking the Zhejiang Lishui Bay Road Tunnel Portal slope as the research object, select thecorresponding physical mechanics parameter of rock and soil, using Ansys finite elementprogram, in considering the bench and Twin-Side heading two kinds of construction methods,the establishment of three-dimensional model, numerical simulation, and the construction ofthe two methods of every step excavation after the stress, displacement is analyzed, and thendraw the following conclusions: Two kinds of method of rock mass under the lesscompressive stress is lower than its compressive strength, and did not appear tensile stress, inthe process of the construction of surrounding rock is generally stable. On the methodselection, from the calculation results of displacement on look, because Twin-Side headingmethod for excavation of each block is smaller, and step by step closure, the lower stepmethod can better control the deformation of surrounding rock, construction process ofsurrounding rock deformation on the lower step method small.