【摘要】 跨孔波速试验是一种原位测定土的压缩波和剪切波速度的方法。它以直达波作为解释对象。本文提出了试验中孔间距和测点位置的合理确定方法,以确保直达波先于折射波和其他路径传播的震波到达检波器。更多还原

【Abstract】 The Seismic Crosshole Survey is an effective method for measuring compressional wave and shear wave velocities of soil in situ. As the direct wave is the obiect of interpretation in the testing, it is very important to reasonably arrange borehole spacings and, measuring points. If the borehole spacing is arranged too small, a tiny measuring error of inclination of borehole will give rise to a larger error of wave velocity of the measured layer. If the borehole spacing is very large, the wave velocity of soil adjacent to the interface cannot be measured. When measuring points are placed in thc vicinity of the interface, the refracted wave and other propagation path waves arrive at the detector prior to the direct wave. To make sure the reliability of testing results, the author has derived formulas to determine borehole spacings, L, and measuring point positions, h, in the case of uncased borehole and that of cased boreholes according to the theory of elastic wave propagation in the layering stratum. The formulas are as follows, for uncased boreholes, h/L≥（1-sin（i_c+ψ））/（2cos i _c cosψ） for cased boreholes, h/L≥（n（V₂）/（V₁）cosψ-n-（V₂）/V₁）sinψ)/（2（V₂）/（V₁）cosψ） where ψ is the tilting angle of interface, i_c is the critical angte（i_c=are sin（V₁）/）V₂)), V₁, V₂ are wave velocities of the layers propagating incidence wave and re fracted wave respectively, and n is the ratio of wave uelocity of the casing pipe to that of the measured layer. The formulas above are suitable for a variety of strata which include hard layer, soft layer and bed rock, etc.更多还原