Optimum Design And Research On Supporting System Of Support - Supported Pile

With the development of economy and urbanization in our country, high-rise buildings and underground structures are emerging constantly owing to short of urban land. The construction of deep foundation of high-rise buildings and the exploitation of underground space are required for large-scale earth excavation, which will involve deep excavation problems. Deep excavation engineering is conducted in a complex environment and uncertainties are abound, so the shape of excavation, the type of support, the properties of soil, the surrounding environment will effect the deformation and stress state of supporting structure. Therefore, analysis and optimization is necessary to the foundation pit support designed with traditional methods.In this paper, for a practical engineering example in Nanjing, using finite element method, the design of foundation pit support with particularity is explored, key parameters analysis and multi-factor orthogonal analysis for support system is achieved, and based on the simulated results, some adjustments to monitoring program is made, the obtained conclusions are shown as follows:(1) According to the simulation of process of the excavation, it shows that:to foundation pit support with irregular shape, the lateral displacement in the middle is greater than the corner with a significant spatial effects, and the maximum stress is in the corner of the upper part of supporting system; lateral deformation shows as a parabola curve along depth direction in single support+piles supporting systems, and the maximum displacement occurs in the lower pit near the bottom of the pit areas;(2) According to the simulation under the trestle horizontal load, the values of deformation in the foundation pit support increased about 6.4%, therefore long-term effect will inevitably influence the structure and it should be strengthen.(3) According to the analysis of four influencing factors:distance of double-row piles, depth of piles, it shows that: ①the increase of distance of double-row piles and diameter of piles double pile are in deformation control of foundation pit, but when increases to a certain extent, the impact of excavation lateral deformation gradually decreases;②the increase of depth of piles and stiffness of ring beam and pull beam are not obvious in deformation control of foundation pit.(4) Conduct orthogonal multivariate test as the target of lateral deformation and engineering budget, analyses the interaction of four factors, proposed optimization design for reduce the cost in the premise of ensuring safety.(5) According to the internal forces and deformation values which based on the simulation of excavation process, find weaknesses branched construction of retaining structures and partial security of the region, to make corresponding adjustments to the Foundation’s monitoring program.