Study On The Design Method Of Equivalent Retaining Wall For The Treatment Of Shallow Accumulation Layer Landslide In South Shaanxi With Micro-piles

The mountainous area of South Shaanxi(Hanzhong,Ankang and Shangluo)is located in the Qinba mountain area of China.It has complex geological structure,broken rock mass,special climate and fragile geological environment.It is one of the high-risk areas and disaster areas in China.A large number of shallow accumulation landslides are distributed in this area,which are characterized by large scale,high frequency,sudden occurrence and great harmfulness.The sliding materials of this kind of landslides are generally accumulated by the secondary accumulation in the Quaternary loose accumulation layer,and the sliding surface is generally the contact surface between the accumulation layer and the underlying bedrock.The diameter of the micro pile is less than 300 mm,the length diameter ratio is large,the bending rigidity is small,and the construction disturbance is small.In the actual project,the applicability of the micro pile to the landslide soil is strong,the form of pile arrangement is flexible,and the construction speed is fast.In recent years,with the deepening of people's understanding of the hazards and failure mechanism of landslides,the application of micropiles in shallow landslides has gradually increased,and achieved good engineering results.Combined with numerical simulation,theoretical analysis and a large number of engineering examples,this paper analyzes the interaction mechanism between the pile and the soil mass,the characteristics of the stress and displacement of the soil mass around the pile,and puts forward the design principle and design method of the equivalent retaining wall for the treatment of shallow accumulation layer landslide in South Shaanxi by using the existing mature gravity retaining wall design method It provides a new idea for the treatment of shallow accumulation landslide in southern Shaanxi by micro pile,and can quickly develop the design scheme in emergency rescue engineering.The main work is as follows:(1)to collect and learn a lot of landslides in mountaineous areas survey report and related knowledge,summarize on the development characteristics of accumulation landslide in mountaineous areas,found that regional landslides in southern shaanxi are mainly composed of shallow accumulation landslide,landslide thickness is small,the landslide is mainly composed of clay powder,cuttings,slope wash and eluvial soil composition,the weathering degree is higher,the structure of loose and porous,small cohesive force.(2)the pile-soil complex structure is formed when the soil between piles and piles is controlled by micro-piles in the shallow accumulation landslide in southern Shanxi region.Through numerical simulation displacement calculation and analysis,pile-soil complex structure exists continuously in the area between the top and bottom of the micro-piles,and between the front of the first row of piles and the back of the third row of piles.(3)In this paper,the core supporting system formed by the treatment of shallow accumulation landslides in southern Shaanxi by micro piles is equivalent to the retaining wall supporting structure.By numerical simulation,the characteristics of the force and displacement changes of the landslides under 18 working conditions,including the row spacing of 5D ? 10 d and the pile spacing of 8D ? 10 d,are studied.The design method of the equivalent retaining wall for the treatment of shallow accumulation landslides in southern Shaanxi by micro piles is given The results of numerical simulation are compared between the design of micro pile and the design of equivalent retaining wall.(4)The design principle,specific design method and design flow of the equivalent retaining wall of the shallow accumulation layer landslide in the south of Shaanxi Province are given.The calculation results of different design methods are compared by the example of Yangjiawan village landslide in Hanzhong.