Optimization Design Of Pile Anchor Structure For Deep Excavation Engineering In Lanzhou Region

Pile-anchor retaining structure is a kind of support applied extensively in deep foundation excavation, playing a role in controlling actively the deformation of deep foundation excavation effectively by applying prestress to anchor. However, for the new deep foundation excavation, many inevitable additional loads with complex situations on the top of deep foundation excavation often be discovered at the edge of it. When the deep foundation excavation pile-anchor support is designed, the effect caused by different additional load for deep foundation excavation is rarely considered. The existing design methods are difficult to select the reasonable combination of design parameters quickly and accurately, and the design results are also difficult to ensure the combination of design parameters optimal. Therefore, the influence, due to additional load in different conditions, on deep foundation excavation is simulated by using FLAC3 D software, and the deep foundation excavation is optimized by using genetic algorithm. They can be achieved from the following aspects:(1) Numerical model of deep foundation excavation is established using FLAC3 D software. Mohr-Coulomb model is put to use for constitutive model of soil. Pile and anchor are stimulated by structure element. 7 different conditions are set on the top of deep foundation excavation. The influence produced by different additional load with different distances from the edge of deep foundation excavation. Horizontal displacement of deep foundation excavation and internal force of anchor and pile are analyzed. The rules of horizontal deformation of different excavation conditions and internal force of each row anchor will been drawn. When deep foundation excavation pile-anchor retaining is designed, the reference could be provided for how to set parameters of pile and anchor.(2) Firstly, improving the solution method of anti-pulling force of prestressed anchor from the aspect of the self-supporting of soil and the anchor-soil interaction, the calculation method of safety factor of integral stability could be improved from that and sliding surface is searched random based on the genetic algorithm to calculate the safety factor of integral stability. Secondly, the construction cost of pile and anchor in one unit width of wall is taken as the objective function of optimization, and the optimization design system of pile-anchor in deep foundation excavation could be compiled in MATLAB based on genetic algorithm. Last, the results of optimization design and engineering examples were compared. The comparative results show that the optimization design system can obtain a significant economic benefit on the basis of safety of deep foundation excavation, proving the rationality of this optimization design system preliminarily.