混凝土灌注桩桩周土力学参数反分析方法研究
发布时间：2019-06-25 16:00
【摘要】：桩基础的承载能力主要取决于桩周土的极限承载能力,土的强度主要体现在抗剪强度上。因此,土的抗剪强度指标是决定桩基础承载力的主要因素。土的强度参数包括黏聚力c和内摩擦角φ,目前,这两个参数的取得通常是通过土工试验完成,包括直接剪切试验、三轴压缩试验等。但由于土工试验需要将试样脱离其工作环境,而且无法精确地模拟真实工作条件下土的破裂面,因此土工试验得到的强度参数存在较大误差。国内外专家通过一系列改进的试验来模拟土的真实工作状态,但仍未能完全达到预期目标。本文根据桩周土材料受力特性与三轴压缩试验中土样的力学特性的关联性分析,分别研究了桩侧土和桩端土的应力状态；应用弹性力学理论,推导了1/4无限平面弹性体在一侧受到均布正应力和均布切应力的条件下的应力解,使用明德林解求解桩端地基单元的应力,进而确定土单元破裂面,求解其第一主应力和第三主应力；结合岩土材料离散的特性,提出了桩侧土的应力衰减系数,进而应用莫尔-库伦准则和应力路径理论提出反分析方法—莫尔应力圆图解法,求解土的强度参数。对于桩侧土,采用本文推导的桩侧土单元应力解,求解桩侧土单元应力并应用衰减系数公式进行修正,通过应力路径理论,确定桩侧土极限平衡状态所在位置。对于桩端土,采用集中力作用于地基内部条件下的明德林解计算桩端土有效压缩层厚度范围内的土单元应力,通过应力路径理论,确定桩端土极限平衡状态所在位置。然后,分别对黏性土材料和无黏性土材料应用对应的莫尔应力圆图解法,确定桩周土的黏聚力和内摩擦角。在建立强度参数反分析方法后,应用混凝土灌注桩静载荷试验的荷载和位移数据,对混凝土灌注桩桩周土材料强度参数反分析求解,将反分析得到的强度参数分别应用于有限元强度折减法、荷载增量法的极限荷载分析,荷载增量法计算的P-s曲线较好的拟合了静荷载试验P-s曲线；使用有限元强度折减法研究了桩基础的极限荷载问题,进一步证明本文提出的莫尔应力圆图解法可以求解满足工程设计要求的强度参数。
[Abstract]:The bearing capacity of pile foundation mainly depends on the ultimate bearing capacity of soil around pile, and the strength of soil is mainly reflected in shear strength. Therefore, the shear strength index of soil is the main factor to determine the bearing capacity of pile foundation. The strength parameters of soil include cohesion force c and internal friction angle 蠁. At present, these two parameters are usually obtained by geotechnical tests, including direct shear test, triaxial compression test and so on. However, because the geotechnical test needs to separate the specimen from its working environment, and can not accurately simulate the fracture surface of the soil under the real working conditions, there is a big error in the strength parameters obtained from the geotechnical test. Experts at home and abroad simulate the real working state of soil through a series of improved experiments, but they still fail to achieve the expected goal. According to the correlation analysis between the stress characteristics of soil around pile and the mechanical properties of soil samples in triaxial compression test, the stress states of soil on pile side and soil at pile end are studied in this paper. Based on the theory of elasticity, the stress solution of 1 鈮，
本文编号：2505810
[Abstract]:The bearing capacity of pile foundation mainly depends on the ultimate bearing capacity of soil around pile, and the strength of soil is mainly reflected in shear strength. Therefore, the shear strength index of soil is the main factor to determine the bearing capacity of pile foundation. The strength parameters of soil include cohesion force c and internal friction angle 蠁. At present, these two parameters are usually obtained by geotechnical tests, including direct shear test, triaxial compression test and so on. However, because the geotechnical test needs to separate the specimen from its working environment, and can not accurately simulate the fracture surface of the soil under the real working conditions, there is a big error in the strength parameters obtained from the geotechnical test. Experts at home and abroad simulate the real working state of soil through a series of improved experiments, but they still fail to achieve the expected goal. According to the correlation analysis between the stress characteristics of soil around pile and the mechanical properties of soil samples in triaxial compression test, the stress states of soil on pile side and soil at pile end are studied in this paper. Based on the theory of elasticity, the stress solution of 1 鈮，
本文编号：2505810
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