The Research Of Working Mechanism On Composite Soil Nailing Wall Retaining Structure System

Compound soil-nailing wall is a structural system, which is, besides soil nailing wall, also composed of a combination of one or more things such as pre-stressed anchor rods, waterproof curtains and micro piles and soil-nailing wall. It has been widely used in foundation pit works. It is complicated to analyses its work mechanism on the whole, for reason that it has many combination types. It has influenced their conceptual analysis and flexible uses for designers as well as set limitations on its popularity and application level. Therefore, I have studied the work mechanism of compound soil-nailing walls, explored routes of breeding and development of stresses on different structural components as well as their role played in its overall function of compound Soil-nailing Wall, revealed deformation modes of various compound soil-nailing walls, which would have great meaning in engineering works and theory.It is based on actual works monitoring, build animation models with FLAC3D software, make comparison between data of actual monitoring and computation to verify the software and constitutive models in the text. On its basis, it has studied stresses and deformation disciplines and global stability individually for micro piles+ soil nailing wall, micro piles+anchor ropes+soil nailing wall, curtain+soil nailing wall, curtain+anchor ropes+soil nailing wall and curtain+micro piles+anchor ropes+soil nailing wall, which is common to support structures of foundation pits. The following conclusion has been taken:1) Characteristics for deformation:anchor rope influences its settlement and horizontal displacement tendency, where settlement curve appears sunken shape and horizontal displacement appears swelled abdomen with anchor ropes; while they appear the most on slope top without anchor ropes. For curtain and micro piles, it has no obvious influences on deformation discipline. For curtain and anchor ropes, it has obvious influence on deformation reduction, while micro piles can’t so behave effectively. It can be concluded that strengthening curtain design may reduce deformation, but reinforcing micro piles and improving pre-stressed load can’t behave that.2) Stresses discipline:it has an uniform tendency for stresses distribution of soil nails and anchor ropes for different types of compound soil nailing wall, which appears as jujube stone in shape of axial stress of soil nails, where it is bigger in the middle and smaller at both ends and it dedicates on anchoring section for anchor ropes. The stress is the biggest on anchor ropes at the lowest layer, while it is the smallest on ropes at the top; it is effective to reduce axial stress on soil nails with anchor ropes and curtain, however there are no influence on soil nails and anchor ropes by micro piles. So it is feasible to reduce stresses on soil nails by reinforcing curtain design and there are no obvious effects to reinforce micro piles or increase pre-stressed stress.3) Failure mode:it has influenced failure mode by curtain, where it appears slipping failure mode without curtain and it fails with reinforced body horizontally slipping toward excavated surface, heaving near slope foot and slipping downward beyond the reinforced zones. There is no influence on failure modes for anchor ropes and micro piles. It doesn’t influence failure mode by changing parameters of curtain, micro piles and anchor ropes.