Soil Arching Effect Analysis Of The Spares Pile-soil Nail Compound Support In Foundation

The spares pile-soil nail compound support is one type of combined soil nail supports, which forms by summarizing the soil nails and micro-limitations. The spares pile-soil nail compound supporting structure mix the supporting technologies of the row pile, soil-nail wall and composite soil nailing structure, forming the supporting system that the soil arch-row piles-soil nail wall together work. Because of the bearing characteristics of the support, the mechanics of the interaction between sparse pile and soil nail, the rules of the load transfer and the determination of pile spacing, so far there is no unified theory or design method, which needs to be more in-depth researched. Therefore, based on a project, this paper studied internal force calculation and design method by resorting to theoretical analysis and numerical simulation. The main contents are as follows:(1) The mechanism of the soil arching, types and forms of sparse pile-soil nail retaining structure are introduced and analyzed. According to the principle of three-hinged arch in structural mechanics, force analysis of soil arch is made and a formula for calculating critical spacing between beams was given.(2) On the basis of the stress analysis of soil arch between piles, the earth pressure on the anchored bulkhead and stability and the pile spacing were studied respectively. The concrete formulas were given through calculation.(3) Combining the research results about internal force analysis and a formula for critical spacing between beams, the normal design method of the sparse pile-soil nail retaining structure was gained. According to designing the foundation pit of Guangzhou Railway Group's No.1 rise apartment building on the Gonghe west road, the results of theoretical analysis coincide with the in-situ test results.(4) Establish three-dimensional finite difference model to simulate construction process of the sparse pile-soil nail retaining supporting system with Flac3d software. Furthermore, it compares the result with practical monitoring data, the results of theoretical analysis coincide with the in-situ test results.