基于大变形有限元的CPTU尺寸效应与贯入速率研究
Size effect and penetration rate of CPTU based on ABAQUS
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摘要: 孔压静力触探(CPTU)技术是目前运用最为广泛的原位测试方法之一,但其贯入机理的研究尚未成熟,实测结果分析往往通过经验公式进行推算,准确性不够。通过ABAQUS数值模拟软件对探头在黏土中的贯入进行有限元模拟,分别取半径为0.9,1.8,3.6,4.8 cm的探头对尺寸效应展开研究,同时分别以0.1,1,2,3,4 cm/s的贯入速率进行贯入,进而就贯入速率对贯入阻力的影响进行探讨。研究表明:随着探头尺寸的增加,锥尖与探杆区域附近的塑性区面积都增加,锥尖阻力会发生一定程度的降低,贯入应力影响的最大归一化水平距离也相应减小。不考虑超孔压影响的情况下,随着贯入速率的增加,稳定状态下的锥尖阻力基本不变,但贯入越容易达到稳定状态。Abstract: The piezocone penetration test is one of the most widely used in-situ tests, but the research on the penetration mechanism has not been mature, which results in that empirical equations are always used to assess the behavior of soils with less accuracy. The ABAQUS is used to simulate the penetration process of the cone. The radius of cone is valued as 0.9, 1.8, 3.8 and 4.8 cm respectively to study the “size effect”. The rate of penetration is valued as 0.1, 1, 2, 3 and 4 cm/s to investigate its effect on the cone tip resistance. It is summarized that as the cone radius increases, the plastic zone area around the shaft and cone expands, the cone tip resistance decreases, and the maximum normalized horizontal affected distance decreases. Meanwhile, the steady-state cone resistance keeps constant with the increase of penetration rate without considering the excess pore pressure, but the steady-state condition is more easily reached.