张智慧, 朱文文, 刘洋义等. 成桩后黏性土中超孔压和有效应力试验研究. 力学与实践, 2023, 45(3): 615-626. doi: 10.6052/1000-0879-22-367
引用本文: 张智慧, 朱文文, 刘洋义等. 成桩后黏性土中超孔压和有效应力试验研究. 力学与实践, 2023, 45(3): 615-626. doi: 10.6052/1000-0879-22-367
Zhang Zhihui, Zhu Wenwen, Liu Yangyi, et al. Experimental study on excess pore pressure and effective stress in cohesive soil after pile formation. Mechanics in Engineering, 2023, 45(3): 615-626. doi: 10.6052/1000-0879-22-367
Citation: Zhang Zhihui, Zhu Wenwen, Liu Yangyi, et al. Experimental study on excess pore pressure and effective stress in cohesive soil after pile formation. Mechanics in Engineering, 2023, 45(3): 615-626. doi: 10.6052/1000-0879-22-367

成桩后黏性土中超孔压和有效应力试验研究

EXPERIMENTAL STUDY ON EXCESS PORE PRESSURE AND EFFECTIVE STRESS IN COHESIVE SOIL AFTER PILE FORMATION

  • 摘要: 针对预制桩沉桩挤土效应问题,采用现场原位试验和数值模拟方法,分析了桩土界面超孔压和竖向有效应力随时间的变化规律,并应用水力压裂理论、孔穴扩张理论和修正剑桥(modified Cam-clay, MCC) 模型,揭示了成桩后桩周土体固结过程的超孔压沿桩长的分布形式。结果表明:桩周超孔压大小同孔压与传感器入土深度成正比;在外载荷作用下,黏性土中超孔压和竖向有效应力分别随时间呈“增–减–平”和“平–增–平”的三段式变化趋势;成桩后约25天,超孔压基本消散完毕,竖向有效应力趋于稳定最大值;基于修正理论公式的数值模型得出,不同载荷下,桩侧中下部出现负超孔压,距桩的水平距离和距桩端竖向距离越小,超孔压越大。可为同类静压沉桩挤土效应问题提供参考依据。

     

    Abstract: For the soil compaction effect in a precast pile, the variation with time of excess pore water pressure and vertical effective stress at the pile-soil interface is analyzed by means of in-situ test and numerical simulation. The hydraulic fracturing theory, cavity expansion theory and modified Cam-clay (MCC) model are used in this study. The distribution of excess pore water pressure along the pile length during the consolidation process of soil around the pile is revealed. The results show that the excess pore pressure around the pile is proportional to the depth of the sensor, just like the pore pressure. Under the action of external load, the excess pore pressure and vertical effective stress in cohesive soil show a three-stage trend of “increase–decrease–level” and “level–increase–level” respectively with time. About 25 days after the pile is formed, the excess pore pressure is basically dissipated, and the vertical effective stress tends to the maximum value of stability. Based on the numerical model of the modified theoretical formula, under different loads, negative excess pore pressure appears in the middle and lower part of the pile side. The smaller the horizontal distance from the pile and the vertical distance from the pile end are, the greater the excess pore pressure is. It can provide reference for similar problems of soil squeezing effect of static pressure pile driving.

     

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