Study On Optimization Of Excavation And Support Scheme & Secondary Excavation Of High And Steep Slope

Reconstruction and expansion of high and steep slopes will inevitably require the removal of the original support structure,and the high and steep slope without support is easy to be destroyed.Therefore,the stability control technology of high and steep slopes in the secondary excavation is more stringent the first time.At present,the research on the excavation stability of high and steep slope mostly focuses on the initial state and final state of the slope.As for the process of excavation,there are few comprehensive studies on the change of safety factor,evolution of landslide mode,selection of support scheme,optimization of construction procedure and so on.Relying on the K2+060～K2+200 section of the expansion project of Yicheng Avenue in Shenzhen,this thesis makes a numerical model for the reconstruction and expansion of K2+100 section high and steep slope,and analyzes the stable state of slope excavation process under different excavation schemes,support schemes and construction procedures.The main research contents and achievements of this thesis are as follows:(1)Based on the FLAC3 D finite difference program,the FISH language is used for secondary development,and the subprograms are embedded in different constitutive models to carry out triaxial numerical tests on geotechnical specimens.The research shows that the confining pressure has a great influence on the peak strength and residual strength of rock and soil materials.In the process of the gradual failure analysis of the slope,the influence of the confining pressure on the residual cohesion and residual internal friction angle of the rock and soil should be considered.(2)The applicability of horizontal layered excavation mode and slope layered excavation mode in the excavation process of high and steep slope is compared.The analysis of the change of safety factor,the evolution of landslide collapse mode and the development of excavation unloading displacement in the process of slope excavation shows that the final state of slope obtained by different excavation modes is consistent,but the horizontal excavation mode is more consistent with the slope in this thesis.(3)Comparison and analysis of various support schemes such as h-type anti-sliding pile support,ordinary anti-sliding pile support,anchor support and composite support for high and steep slopes are carried out.The analysis contents include the safety factor of the slope,the position of the potential landslide surface,and the volume of the potential landslide body.The results show that,compared with other support schemes,the prestressed anchor cable support has more advantages in terms of engineering quantity and reinforcement effect.(4)Strength reduction analysis and progressive instability analysis are carried out in the construction process of the reconstruction and expansion of the existing high and steep cutting slope.The results show that most of the deformation of the slope in the process of excavation is elastic deformation,and the last excavation has the greatest influence on the stability of the slope.Special attention should be paid to the protection and reinforcement of the slope toe during the secondary excavation of the high and steep slope.