Research On Application Of Composite Soil Nailing With Anchor In Foundation Pit Engineering

With the rapid development of economy and city, city construction land is limited, and the construction of the modern city into the air and underground development, so a large number of deep foundation pit engineering appear in the city. Soil nailing as a kind of foundation pit supporting forms has many advantages, such as simple construction, short construction period, low cost, this leads that it quickly used in a variety of engineering. Prestressed anchor composite soil nailing is developed on the basis of soil nailing, a modified technique to overcome the limitations of the single soil nailing, can effectively control the displacement of pit wall, make foundation pit engineering more safe and reliable. Due to the influence of many factors, the practice of prestressed anchor composite soil nailing is ahead of theory, certain theory is still not mature. Therefore, we need to improve the theoretical research, to better guide the design and construction.This article will focus on prestressed anchor composite soil nailing supporting technology in the foundation pit engineering safety supporting problem, combined with the practical foundation pit engineering of Beijing, using numerical simulation method. Through the analysis of the simulation results, such as horizontal displacement of slope, axial force of soil nail and anchor, foundation pit stability, under the condition of no supporting, soil nailing and compound soil nail, to study the working performance of soil nailing and anchor composite support, and the results are compared with the monitoring data of the actual project. For no supporting structure of foundation pit, soil nailing supporting of foundation pit and prestressed anchor composite soil nailing supporting of foundation pit makes the simulated analysis respectively. The working performance of soil nailing and anchor composite support is studied by means of comparative analysis, and the results are compared with the monitoring data of the actual project to ensure the reliability of the results. Through the analysis on the slope, soil nail length, inclination of soil nail, anchor position, inclination of anchor, free segment of anchor, anchorage length and prestressed size of the design parameters of composite soil nailing support retaining structure supporting performance influence, summed up the above parameters were investigated, the optimized support scheme of practical engineering is analyzed, and reasonable selection of design parameters analysis method is put forward.Through the analysis and study, get the following conclusions:(1)Compared with pure soil nailing, soil nailing and anchor composite supporting is more safe and reliable. In under the action of prestressed anchor, horizontal displacement of slope are effectively limit, excavation potential slip oriented away from the excavation face offset, the overall stability of foundation pit also greatly improved. (2) The influence of the slope of foundation pit supporting is the largest, the second is the length of soil nail and anchor rod arrangement position, other parameters also have varying degrees of impact. Therefore in design parameters optimization design, the slope, length of soil nail and anchor layout priority should be given. (3) Numerical simulation can not accurately predict the deformation of the foundation pit, but it can well simulate the characteristics of the foundation pit deformation, make the qualitative analysis of the foundation pit, as an important basis for the design and construction. In the case of the existing theory is not perfect, combined with the engineering experience, numerical simulation analysis and the overall stability of the foundation pit to make a comprehensive judgment, is the better optimization design analysis method.