多桩复合地基加固效果评价新思路及波动有限元分析

A New Thought and Wave Finite Element Analysis Method on Piles Composite Foundation

根据桩土应力比计算水泥搅拌桩复合地基承载力理论,提出了利用桩土平均瑞利波速评价复合地基承载力的一种新思路。汲取以往动力测试方法的理论研究和工程实践,根据波动有限元方法并结合人工透射边界条件,基于平面应变假设,计算分析了在脉冲荷载作用下,桩距对水泥搅拌桩复合地基中波的传播的影响,同时结合试测数据,也证明了新思路的可行性。利用信号的互相关分析技术,分析了沿着波的传播方向上地表各点运动的相关性,计算并分析了瑞利波速与地基土、桩的物理力学性质的关系,并分析了桩土平均波速与桩土模量和测点位置的关系。

A new thought is given to appraise improvement effect of composite foundation by use of average Rayleigh velocity of pile and soil, based on the principle of calculating the bearing capacity of cement mixed pile composite foundation by means of stress ratio of pile and soil. Based on the theoretical discussion and engineering practice of the dynamic test methods combined with the theory of finite element for wave motion and artificial transmitting boundary condition, a calculation program is given, which can analyze the wave propagation and its influential factor in the cement mixed pile composite foundation imposed by the impulse load, while feasibility of this thought is validated by using numerical analysis method and test data. Relativity of the movement of each point along the direction of the wave propagation is analyzed by using the correlation analysis theory of the signal and the relation between the velocity of Rayleigh wave and the physical mechanic properties of the foundation soil and pile is also analyzed.Moreover, the relation among the average velocity of wave with, the modulus of pile and soil, and the position of the survey stations, is analyzed, which can provide the theoretical value for on site testing.