Stability Analyses Of Anti-overturning And Anti-sliding Of Global Retaining Structures For Hollow Slender Foundation Pits Near Bank Slopes

Hollow slender foundation pit,commonly used in pipe jacking and subway engineering,has the characteristics of strong integrity and obvious spatial effect because of its small plane size and deep depth.This kind of foundation pit is often set on the side of river because of the need of planning,which makes the characteristics,design and construction of foundation pit very complicated.It is found that the hollow slender foundation pit near bank slopes is likely to overturn or slide globally.The current research results about anti-overturning and anti-sliding of support structure for hollow slender foundation were reviewed.It is considered that the current study is still in the preliminary stage and a definite method for calculating the safety factor of antioverturning and anti-sliding of the support structure for hollow slender foundation pit is lacking.The existing method based on plane assumption makes the design of foundation pit support structure not only wasteful but also not safe.The main work and result of this paper includes the following aspects:1.The failure mode of the support structure for the hollow slender foundation pit near bank slopes was studied through the indoor model test,and the influence of the structural stiffness,the depth of bank slope and the distance between the top of the structure and bank slope on the overall overturning and slide of the supporting structure was analyzed.The results show that when the structure has sufficient stiffness,the whole structure overturns around the bottom of the structure when it is loaded on the side away from the bank.When the depth of the bank slope increases and the distance between the top of the structure and the bank slope decreases,the structure is more likely to overturn.2.Using Z-SOIL finite element software,the three-dimensional numerical model of support structure for the hollow slender foundation pit near bank slopes was established,and the phenomenon of indoor model test was simulated.The distribution of displacement and earth pressure in the hollow slender foundation near the bank was analyzed.The physical definition of overturning failure of the supporting structure of hollow slender foundation pit near bank slopes in sandy soil was given: When the inclination angle of the structure exceeds 5°,the structure is considered to overturn.3.The rotating center of the supporting structure of hollow slender foundation pit near bank slopes in sandy soil was defined when it overturns according to the results of model test and numerical analysis,and the calculation method for safety factor of antioverturning and anti-sliding of global retaining structures for hollow slender foundation pits near bank slopes was given.4.The Z-SOIL software was used in simulating the construction process of the foundation pit of Tianjia lake sewage pipe maintenance inspection well,and the simulation results were compared with the two-dimensional design results by using the software of Qim Star.The importance and advantages of overall analysis of hollow slender foundation pit near bank slopes were further demonstrated.