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对于既有工程桩,其顶面非裸露自由,常规低应变法难以有效检测其桩底深度,而旁孔透射波法则对此有着良好的应用前景。旁孔透射波法可以在桩侧采用竖向、斜向和水平横向敲击的激振方式。通过建立三维有限元模型,对既有工程桩在桩侧竖向、斜向下45°、水平向敲击下进行旁孔透射波法测试模拟分析。读取不同深度信号的首至波走时并进行分段线性拟合的结果表明:在桩侧竖向或斜向敲击时,主要是基于桩身一维P波信号进行分析;在桩侧水平向敲击时,应主要基于桩身的弯曲波信号进行测试。当地基土饱和时,桩身弯曲波波速与土的P波波速相差较小,采用现行的桩身和桩底土拟合直线交点法难以较为可靠地确定桩底深度,而采用在桩侧竖向或斜向敲击方式更为适宜。
For the existing engineering piles, the top surface is not exposed, and conventional low strain method is difficult to effectively detect the depth of the pile bottom, and the side hole transmission wave method has a good application prospect. The parapore transmission method can use the vertical, horizontal and horizontal horizontal percussion excitation modes on the pile side. Through the establishment of a three-dimensional finite element model, a side hole transmission wave method was used to simulate and analyze the existing engineering piles in the vertical, oblique downward 45°, horizontal stroke. The results of reading the first-to-wave travel times of different depth signals and performing piecewise linear fitting show that when the vertical or oblique percussion is performed on the pile side, the analysis is mainly based on the one-dimensional P-wave signal of the pile body; When tapping, the test should be based mainly on the bending wave signal of the pile body. When the local soil is saturated, the difference between the bending wave speed of the pile and the P wave velocity of the soil is relatively small. It is difficult to determine the depth of the pile bottom reliably by using the current straight line intersection method of the pile body and the pile bottom soil. Or oblique strike is more appropriate.