桩土系统分布参数的正反演理论与应用

THEORY AND APPLlCATlON OF DlRECT AND lNVERSE PROBLEM FOR DlSTRlBUTION PARAMETER OF PlLE SOlL SYSTEM

根据静力学理论提出了分层非均匀土质、变截面和非均质桩身的复杂桩土系统在外荷载作用下，桩身位移满足的微分方程和边界条件，推导了线弹性和弹塑性条件下的微分方程解析解。在已知桩土力学参数的条件下，可以计算不同桩顶沉降下对应的荷载大小与桩身相应的内力、摩擦阻力和端承力大小，以及桩底的位移值；也可根据实测的若干个静荷试桩数据，通过作理论计算与实测曲线拟合分析处理，确定桩土系统的力学参数，然后进一步分析桩的受力机理。工程桩静荷试验和内力测试研究结果表明，理论分析的桩底位移和实际试验的残余沉降值比较吻合，计算的桩身内力与实测内力对应性较好，特别是利用４０００ｋＮ的静荷载试验结果进行反演拟合处理求得的桩土系统特性参数，推算外荷载为５２００ｋＮ对应的桩顶沉降值和桩底位移值，与实际５２００ｋＮ静荷载试验的结果很相近。

On the basis of mechanics theory, differential equations and boundary conditions of pile displacement were put forward for the complicate pile soil system with non homogeneous soil and change in pile section and modulus under load on pile top. The corresponding solution was obtained under the condition of linear elasticity and elastoplasticity. With the known condition of mechanics parameters of pile soil system, the corresponding load, the internal force along the pile axis, the frictional resistance and the bearing capacity settlement of the pile can be computed according to the settlement at pile top. On the other hand, the mechanics parameters of pile soil system can be determined by matching the theoretical curve of load settlement and test curve with the data of normal load test, and then the mechanism of pile performance under load can also be analysed. The comparison between theoretical research results and pile test data of load and internal force showed that calculated settlement at pile bottom well matches the residual settlement during loading test and the internal force calculated is much close to the test results. Especilly, comparing with the loading test result of 5 200 kN, it can be successful to applying the parameters of pile soil system which are analysed by matching the loading test result of 4 000 kN to compute the settlements on both top and bottom of pile under acted load of 5 200 kN on pile top.