CPT阻力受土层界面效应影响的数值模拟

Numerical Simulation of CPT Resistance Affected by Soil Interface Effect

因为相邻土层性质差异,导致贯入阻力在穿越土层界面时发生明显变化,成层土中的静力触探试验(CPT)会出现超前、滞后效应,使得依据阻力曲线划分土层的精确性降低。为此设置可变参数,并采用PFC^(2D)软件模拟成层土中的CPT贯入试验。通过对比各组试验获得的阻力曲线,分析贯入阻力受土层界面效应影响的主要因素,并根据颗粒位移和力链分布,研究探头穿越土层界面时的锥土作用机理。结果表明,砂土密实度主要影响超前、滞后深度,而内摩擦角决定阻力稳定值,黏聚力对界面效应影响不大;探头在砂土中超前、滞后深度大于在黏土中的。该研究有助于提高依据CPT阻力曲线识别土层的准确性。

In the cone penetration test(CPT) of layered soil,because of the different properties of adjacent soil layers,the penetration resistance changes obviously when the probe crosses the soil layer interface.The effect of advancing detection appears,which reduces the accuracy of soil layer classification according to the resistance curve.In this paper,variable parameters are set according to previous research results,and PFC~(2D) software is used to simulate CPT penetration test in layered soil.The main factors affecting the penetration resistance affected by the soil interface effect are analyzed,by comparing the resistance curves obtained by each group of tests.According to the distribution of particle displacement and force chain,the action mechanism between the probe and soil when the probe traverses the soil interface is explored.The results show that the compaction of sand mainly affects the depth of detection,while the internal friction angle determines the stability value of resistance,and the cohesion has little effect on the soil interface effect.The depth of detection of the probe is greater in sand than in clay.The results can help to improve the accuracy of soil layer identification based on CPT resistance curve.