A Model Test Research On Prestressed Threshold Of Prestressed Anchor Composite Soil Nailing Based On Synergistic Effect

Composite soil nailing is the thing that combines with traditional soil nailing and stake, anchor, sealing curtain and other structures to compensate for the shortage of soil nailing and expand the range of applications of the soil nailing. Recently, even though the composite soil nailing technique has been used widely, it requires a lot of researches to develop the theory because the theory is still far from sufficient, especially the theory of pre-stressed anchor composite soil nailing. So far, designing the pre-stressed anchor composite soil nailing still uses the simple sum of 1 + 1 = 2 design; in addition, construction depends on engineering experience and comparison with other projects a lot; these two causes lead to the deep excavation accidents occurred frequently. Therefore, it is significantly important to study the theory of pre-stressed anchor composite soil nailing deeply.This paper summarizes the mechanism of soil nail and anchor, elaborates the design theory and methods of pre-stressed anchor composite soil nailing. To solve the insufficient design of pre-stressed anchor composite soil nailing in the excavation engineering, and the issues of achieving coupling while pre-stressed anchor and soil nailing in the synergism, we did the laboratory model test. On the basis of existing research results and the similarity theorem: design and produce the laboratory model box, make a pre-stressed device, test the anchor composite soil nailing under different forms of pre-stressed role of model excavation. According to the deformation of foundation pit and soil nailing, the anchor force change in this process, it gives the following valuable results:The regular pattern of the deformation of foundation pit, including the horizontal displacement on the top of the foundation pitl, the vertical displacement on the top of the foundation pit, the displacement of the surface layer structure, the influence regularity of the deformation under different kinds of pre-stress to the soil nail during anchor composite soil nailing foundation pit excavation; give the guiding advice to the design of composite soil nailing while it is affected by the anchor pre-stress; finally get the reasonable pre-stressed threshold of the pre-stressed anchor composite soil nailing under the synergistic effect.