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利用孔压静力触探(piezocone penetration test,CPTU)试验结果确定超固结比(over consolidation ration,OCR)不仅能避免传统室内试验方法中土样扰动的问题,还能得到地层剖面上连续的OCR值。将静力触探锥头的挤土模式看作是球形孔的扩张,锥面上的正应力和剪应力分别假定为极限扩孔压力和锥–土接触摩擦力;基于修正剑桥模型中圆孔扩张的近似闭合解,提出了利用CPTU测试结果确定OCR的理论改进方法。分别选取轻超固结和重超固结场地的CPTU试验结果,对提出方法的可靠性进行验证。结果表明,在综合考虑锥面粗糙度以及贯入速率等因素的影响后,预测得到的OCR值较已有理论方法更接近实测结果。最后在连云港海相黏土中对该理论改进方法进行应用,计算表明该土层处于欠固结~轻超固结状态。
Using piezocone penetration test (CPTU) test results to determine the over consolidation ration (OCR) can not only avoid the problem of soil sample disturbance in the traditional indoor test methods, but also obtain the continuous OCR value. The squeezing mode of static probe cone is taken as the expansion of the spherical hole. The normal stress and shear stress on the cone are assumed to be the limit expansion pressure and the cone-soil contact friction respectively. Based on the modified hole model in the Cambridge model Expansion approximate approximation solution, put forward the use of CPTU test results to determine the theoretical improvement of OCR method. The CPTU test results of light overconsolidation and heavy overconsolidation were respectively selected to verify the reliability of the proposed method. The results show that the predicted OCR value is closer to the measured results than the existing theoretical methods after considering the influence of cone roughness and penetration rate. Finally, the theory improvement method is applied in Lianyungang marine clay. The calculation shows that the soil is underconsolidated to light overconsolidated state.