【作者】 郭进军；

【导师】 施建勇；

【作者基本信息】 河海大学 ， 岩土工程， 2007， 硕士

【摘要】 土体中静力压入桩承载力的时间效应问题是岩土工程中深受关注的问题，如何合理地估计桩的长期承载力、充分发挥静压桩的特点和优势具有重要的工程实用价值。本文利用GDS应力路径三轴测试系统对标准砂和粉质粘土进行室内试验，分析影响桩基承载力时效的因素，得到一些有意义的结论。本文主要研究工作包括：1)对饱和标准砂采用分别加载的试验方法，分别在不排水和排水条件下利用GDS标准应力路径三轴仪进行应变保持试验。分析对比不同排水条件下的结果，得出砂中沉桩后桩周土体经历的是固结、剪切蠕变问题，而不是应力松弛问题。2)对饱和粉质粘土采用与标准砂同样的试验方法，在排水条件下利用GDS标准应力路径三轴仪进行应变保持试验以及再加载试验。分析试验结果，得出粘性土中沉桩后桩周土体经历的是固结、次固结过程，经过固结、次固结后土体剪切强度提高、初始剪切模量增大。3)对标准砂和粉质粘土的试验结果进行分析对比，说明砂土中桩基承载力的短期时效性取决于桩周土的固结，长期时间效应则是桩周土体膨胀引起挤土应力增大的结果；粘性土中桩基承载力的时效性主要取决于桩周土的固结，次固结对长期时间效应影响不显著。更多还原

【Abstract】 Soil/pile set-up, which is time-dependent increase in jacked-in pile capacity, is an important problem in geotechnical engineering. If it were possible to incorporate the effects of set-up during design, it may be possible to reduce building cost of projects. Based on the results of the experimental tests on ISO sand and silty clay with GDS system, the factors affecting the long-term bearing capacity are analyzed and some useful conclusions are gained as follows.1) A series of drained and undrained Strain-holding tests were implemented on ISO sand with GDS by means of respective-loading manner. Based on the analysis of the results under different drained condition, a conclusion is reached that the soil around the pile in sand experiences the process of consolidation and shearing creep, not stress relaxation.2) The same test procedure is used for silty clay under drained condition, furthermore, some samples were reloaded after axial stress stabilizing. The analysis shows the soil around the pile experiences the process of primary consolidation and secondary consolidation, and both the shear strength and the initial shear modulus increase after consolidation and secondary consolidation.3) The results of tests on ISO sand and silty clay are analyzed and compared, and it shows that: for sand, short-term setup of bearing capacity of the pile depends on the consolidation of surrounding soil, and long-term setup depends on shear swelling, which causes the radial stress to increase around the pile; for the clay, the setup of bearing capacity of the pile depends on the consolidation, and secondary consolidation has not remarkable effect on soil/pile set-up.更多还原