地表水平正反敲击激振下孔法剪切波速测试理论依据讨论

Discussion about the theoretical basis of the down-hole method for shear wave velocity test under surface forward and reverse horizontal hammer strikes

地表水平正反敲击激振下孔法常用于现场剪切波速测试。本文基于动力有限元方法建立了地表水平正反敲击激振下孔法剪切波速测试三维分析模型,采用时域集中质量动力有限元显式逐步积分方法求解了地表水平敲击下线弹性半空间波动响应,分析了不同深度点波形特征及地表水平正反敲击激振下孔法剪切波(S波)波速测试理论依据的合理性。结果表明:地表水平正反敲击下孔法S波波速测试的理论依据,即地表水平正反敲击下压缩波(P波)初动不反向而S波初动反向的理论依据不成立。此外,依据地表水平正反激振下线弹性半空间波动解析解,进一步佐证数值模拟结果的可靠性。

The down-hole method under surface horizontal forward and reverse hammer excitation is frequently used for on-site tests of shear wave velocity.Based on the dynamic finite element method,this paper establishes a three-dimensional analysis model of the down-hole method used for shear wave velocity tests under the surface horizontal forward and reverse hammer excitation.Meanwhile,it determines the solutions of the wave response of linear elastic half space under the surface horizontal hammer excitation through explicit stepwise integration of time-domain lumped mass dynamic finite element.Furthermore,it analyzes the waveform characteristics of points at different depths and the rationality of the theoretical basis of shear wave(S-wave)velocity tests under the surface horizontal forward and reverse hammer excitation.As indicated by the results,the theoretical basis of S-wave velocity tests(i.e.,the non-inversion of P-wave onset but inversion of S-wave onset)using the down-hole method under surface horizontal forward and reverse hammer excitation is not tenable.In addition,the numerical simulation results have been further verified reasonable by the analytical solution of the wave motion in the linear elastic half space under the surface horizontal forward and reverse excitation.