| In this paper, the reservoir banks slope in Ya Lu expressway was discussed,on which Gang Zishang tunnel import is. The basic technological route sequence was described as follows,site research - analysis of factors - conceptual model - analysis of deformation and damage - stability assessment - evaluation and optimization of treatment design. Through the slope engineering geological conditions, rock and soil structure and mechanical properties, the analysis of factors affecting slope, the deformation mechanism and failure mode of slopes was studied in-depth,The water impact on the banks as well as the slope stability was mainly discussed ,which caused reservoir recycling, and the methods was used such as Cacho, two (multiple),limit equilibrium to analysis the water impact on reservoir banks and to predict recycling width. Computing software FLAC-3D was used to further simulate the natural state and the state after reservoir water uplift of the slope. Drawning from the stress and deformation characteristics of the slope stability to support design of the slope and provide a theoretical basis. Then, according to the three sets of treatment design, Numerical simulation were used to support evaluation and optimization of design reasonability and finally comprehensively comparative three options pros and cons to determine a second set of programmes on the slope management.Main content and research results are as follows:(1)With site investigation of the reservoir bank slope, the portal slope of Gang Zishang Tunnel was relatively comprehensively studied on its rock mass structure and physics mechanics, especially on the physics mechanics engineering effect of its outwash sediment. Because of the differences between soil and rock debris, tension crack and slide will easily happen along the interface between soil and rock debris when the mixture of soil and rock debris is so forced that deformation happens. Together with water function, the existing weak muddy cementation between coarse grains in outwash sediment will be further weakened or even be wholly lost, so their physical and mechanical strength will also significantly decreased. (2) Affecting factors of the reservoir banks slope stability was studied deeply from both internal and external aspects, and the interaction mechanism of water and rock was focused on, as well as their impacts on slope stability. Three main roles were summarized as follows. First, the wave erosion and the abrasion on the banks of rock and soil after the reservoir was filled; Second, the pore water pressure and the dynamic water pressure due to fluctuation of reservoir water level; Third, the softening influence of water on rock and soil mass below water level, which mainly makes the physical and mechanical strength of rock and soil of reservoir bank slope decrease.(3)Based on main characteristics of reservoir-bank slope, the width of collapse bank was predicted with different methods, i.e., Cacho, two (multiple), and limit equilibrium. Forecasting results from three methods all show that different parts of the slope will have bank collapse in different degrees after the Pubugou Power Station is filled. Among them, the tunnel portal slopes illustrated by 2-2 section and 4-4 section have the largest scale of collapse banks, width up to 83.65 m and 89.04 m, height up to 51.20 m and 54 m, and the elevations of final collapse banks will all arrive at 900 m or so, that is, arrive at the elevation of rode surface around the lake.(4)Deformation mechanism and destruction mode of reservoir banks slopes were analyzed in this thesis. Based on the analysis of water influence on the deformation and destruction mechanism of rock and soil mass of bank slopes, destruction and instability mechanisms were respectively mentioned for rock and soil mass of bank slope below the roadbed ground, as well as for rock and soil mass of portal slope above tunnel. The failure modes of bank slopes are significant different in the filling water process and discharging water process, including back-destruction and gradually advance-decline; The main failure modes of portal slope above the tunnel include (mainly below the road around lake)tension damage to back edge, shear failure to frontage, and the damage shape is similar to an arc.(5)Bank slope in natural state and filling water state was respectively simulated with numerical methods, and the slope stability was analyzed according to the stress and deformation characteristics of numerical analysis. The results indicated that the protruding part of the tunnel inlet most likely generates instability damage after filling water, and the deformation are finite for 1-1 and 3-3 section on both sides of the tunnel inlet of the slope after filling water. There is no obvious shear strain concentration zone inside slope. Therefore, it is believed that the overall stability of the banks is better after storing water, and that the destruction of the overall instability is impossible.(6)According to analysis of deformation and damage mechanism, stability calculations and numerical simulation analysis, together with the consideration to the affected areas and degree of the reconstructed reservoir banks after water filling, three kinds of existing protection design proposals were evaluated, respectively. Finally, by contrast, the rationality of the second set of protection project was determined. Additionally, the proposals of the protection measures of the entire reservoir bank slope were put forward. |
