静力触探锥头阻力的近似理论与实验研究进展

APPROXIMATE THEORITICAL AND EXPERIMENTAL RESEARCH DEVELOPMENT OF CONE PENETRATION RESISTANCE IN STATIC CONE PENETRATION TEST

锥头阻力在静力触探试验中扮演着十分重要的角色。从不同角度,对触探中锥头阻力的研究进行简要阐述,对承载力理论、空洞膨胀理论、应变路径法及运动点位错法等几种理论分析方法进行了回顾。另外,对数值分析和实验研究的进展情况进行了叙述。并对各种方法的适用性进行了比较。承载力理论虽然简单,但忽略了土的压缩性和探杆周围初始应力的增加,所以不能精确地模拟锥头的深层贯入。空洞膨胀理论提供了一个分析锥头阻力的简单而较精确的方法,它考虑了土的压缩性(或膨胀性)和锥头贯入过程中锥杆周围应力增加的影响。但这种方法是将锥头贯入与空洞膨胀之间做了一个等效模拟,所以不同的模拟方法,得到的结果差别较大。应变路径法能够有效解决饱和粘土中的不排水贯入,但不适用于砂土.运动点位错法因为考虑了部分排水,所以能较好地预测团结系数,但采用了线弹性分析,故位错法在其他方面的应用还需要大量的试验验证。有限元法在处理锥头贯入这类慢侵彻问题时缺乏一种很好的处理技术,导致它在进行破坏荷载计算时有显著的误差和数值计算困难。标定槽试验将在验证和建立锥头阻力与土的性能关系方面继续起到一个重要作用,但其结果需经过校正后才可应用到现场。最后对该领域的研究趋势进行了讨论。

Cone resistance plays a very important role in static cone penetration tests. The studies on the cone resistance in static cone penetration tests are discussed briefly. Some theoretical methods - bearing capacity theory, cavity expansion theory, strain path method, moving point dislocation method - are reviewed, together with the developments of numerical analysis and experimental research. At the same time, the applicabilities of various methods are compared. Bearing capacity theory is simple, but it cannot be used to simulate accurately the deep penetration of cone because it ignores the compressibility of soil and the increase of the initial stress around the shaft. Cavity expansion theory is a simple and more accurate method of analyzing cone penetration resistance and it considers the influence of compressibility or expansibility of soil and the increase of the stress around the shaft in the process of cone penetration on the penetration resistance. Because cavity expansion theory uses the expansion of cavity to simulate equivalently the penetration of cone, the results obtained from in part and can predict consolidation coefficient well, but its other applications remain to be tested because it is an analytic approach of linear elasticity. Finite- element method lacks a suitable technique in dealing with the slow penetration of cone and this results in significant errors and serious difficulties in calculating failure loads. Calibration chamber tests will continue to play an important role in validating and establishing correlations between cone resistance and soil properties, but the results obtained need to be corrected before they are used in field. Finally, some research trends in the field are discussed.