双参数地基横向受荷长桩参数反演方法研究

Parameter Inversion Method for Laterally Loaded Long Pile Under Two-parameter Foundation

为了获取mz+C双参数地基模型下横向受荷长桩参数,基于m法原理,在地基系数等于零的位置建立坐标系,将地面以上桩身视为虚拟段。考虑剪力和弯矩共同作用时的情形,根据荷载效应等效原理,将地面处荷载简化到桩顶,建立了横向受荷长桩双参数计算模型。将桩土相对刚度和z0作为未知参数,提出了地基参数反演模型。该反演模型考虑了土抗力对荷载作用形式、地面处桩身位移和转角的影响。根据桩在地面处的位移和转角实测值反演地基参数,并结合算例通过桩身最大弯矩和地面处土抗力验证了反演方法的可行性。结果表明:本研究方法能够保证桩在地面处位移和转角理论值与实测值相符,最大弯矩及其位置误差很小;与m法相比,地面处土抗力变大对桩身弯矩影响程度沿深度先增大后减小,主要影响范围位于最大弯矩位置附近;桩身抗弯刚度与最大弯矩、地面处土体抗力均成线性关系,对二者影响较大且呈反向变化;根据最大弯矩和地面处土抗力实测值可以求得抗弯刚度的合理取值范围,考虑抗弯刚度随着桩顶荷载或位移的变化能够更好地模拟桩土的实际工作状况,可以提高mz+C双参数地基模型计算精度。

To obtain parameters for laterally loaded long pile with mz+C two-parameter foundation model,based on the principle of m method,the coordinate system was established at zero position of foundation coefficients,and the pile above ground was regarded as a virtual segment.Then,the ground loads were simplified to pile tip according to the theory of equivalent load effect under the combined action of shearing force and moment,and the two-parameter calculation model for laterally loaded long pile was established.Regarding pile-soil relative stiffness and z0 as unknown parameters,the inversion model for foundation parameters was proposed.Soil resistance effect on form of load action,ground displacement and angle was considered by using inversion model.Foundation parameters were inversed according to the measured values of ground displacement and angle.The feasibility of inversion method was verified by the maximum bending moment of pile and resistance of ground soil.The result indicates that the theoretical values of ground displacement and angle are same to the measured values,and calculating errors of the maximum moment and its position are very small with the study method.Compared with m method,the degree of influence caused by increasing ground soil resistance on moment increases first and then reduces varying with depth,and the main influencing area lies nearby the maximum moment.The flexural rigidity of pile is linear with the maximum moment and ground soil resistance,and it has great influence on them and changes in reverse direction.The reasonable value range of flexural rigidity is obtained theoretically according to the measured values of the maximum moment and ground soil resistance.Considering the change of flexural rigidity varying with ground loads or displacement can preferably describe the practical working conditions between pile and soil,and then it can improve calculation accuracy of mz+C model.