The Applied Research On The Supporting System Of Micro-piles And Composite Soil Nailing Wall

As a support form of composite soil nailing wall support, support of micro-piles and composite soil nailing wall is common and effective, this support form has some advantages such as convenient construction, short time and low cost. The support form can control the deformation of fundation pit effectively and improve the stability of slope greatly. In the present, study on the mechanism of the support form is less, although the support form is used widely, complete theoretical system on the support form is still not formed.Based on the previous studies, the paper firstly analyzes the interaction mechanism on the supporting system of micro-piles and composite soil nailing wall. Then combined with the reference example, the finite element analysis software MIDAS/GTS is used to establish three-dimensional finite element simulation model and simulate the excavation and supporting process of the pit for two support forms, which are the supporting of micro-piles and composite soil nailing wall and the soil nailing wall support. The paper compares and analysis the computational results of the horizontal displacement of the pit wall, the ground subsidence, the pit uplift and the soil nailing axial force for the two kinds of simulative cases. Finally, based on the finite element analysis software MIDAS/GTS, the paper mainly analyzes the influence of micro-piles factors such as the diameters, the spacings and the embedded depths on the stress and deformation for the supporting system of micro-piles and composite soil nailing wall, and the main research results are as follows:(1) Each row of soil nailing imposed restricts the horizontal displacement of the pit wall obviously.(2) The stress of soil nailing has the obvious excavation effect and time effect.(3) The maximum shear of micro-piles is minus shear and appears in the depth of the den plane. With the increase of the excavation depth, the corresponding maximum shear of micro-piles in each excavation step is increasingly large.(4) The bending moment zone along the length of micro-piles is divided into plus and minus bending moment zone. The maximum bending moment values of the plus and minus bending moment zone are both increasing with the increase of excavation depth, and the place of the maximum bending moment value is down gradually. After each excavation and supporting, the maximum bending moment value of micro-piles appears in the minus bending moment zone and in the depth of the den plane. (5) Through the analysis of the numerical simulation results, we know that, the micro-piles have some effect on controling the horizontal displacement of the pit wall and reducing the axial force of the soil nailing, but have little effect on controling the ground subsidence and the pit uplift.(6) In the design of micro-piles with safety requirements, the diameter of micro-piles has some effect on the axial force of the soil nailing, but has little effect on the pit deformation. The spacing and the embedded depth of micro-piles both have little effect on the pit deformation and the axial force of the soil nailing.