基坑工程中土体抗剪强度指标的合理选用

发布时间：2019-02-22 18:33

【摘要】：分析基坑工程中影响土体抗剪强度指标的几个重要因素,选取基坑降水前后的土样和基坑开挖后基坑侧壁的土样,采用直接剪切仪和三轴仪分别进行了土样的抗剪强度试验,根据试验结果分析降水、基坑开挖、不同试验方法对基坑工程中土体抗剪强度指标的影响;采用大型通用有限元软件Abaqus来模拟基坑在不同试验组结果下基坑中侧壁及支护结构的应力状态和变形情况。利用规范中推荐的基坑中土压力的计算公式针对不同试验组结果分别计算基坑侧壁土压力,进行基坑支护结构桩长计算和配筋计算,比较分析不同试验组结果值对基坑支护结构设计的影响。通过上述工作得出基坑工程中抗剪强度指标不同的选取方法对基坑工程安全及稳定性的影响规律(1)针对具有降水措施的基坑工程设计时,采用降水前的基坑土样进行试验,设计计算时应适当提高试验结果值的黏聚力大小,否则会造成不必要的浪费;(2)三轴试验中改变围压与常规围压作用下所得的抗剪强度指标值大小存在差异,土样的黏聚力值差异较大,两组对比试验值用于基坑支护结构设计,所得计算结果相近;(3)直剪试验和三轴试验所得的抗剪强度指标值存在差异,三轴剪切仪试验条件更加接近土样的受力变形状态,有三轴设备的前提下基坑设计计算的抗剪强度指标值应选取三轴试验值。
[Abstract]:Several important factors affecting the shear strength of soil in foundation pit engineering are analyzed. Soil samples before and after foundation pit dewatering and soil samples on the side wall of foundation pit after excavation are selected, and the shear strength tests of soil samples are carried out by means of direct shear meter and triaxial apparatus, respectively. According to the test results, the influence of dewatering, excavation of foundation pit and different test methods on the shear strength index of soil in foundation pit engineering is analyzed. The stress state and deformation of the side wall and supporting structure of foundation pit under different test groups were simulated by using the large and universal finite element software Abaqus. According to the results of different test groups, the soil pressure of side wall of foundation pit is calculated according to the formula of earth pressure in foundation pit, which is recommended in the code, and the pile length and reinforcement of foundation pit supporting structure are calculated. The effect of the results of different test groups on the design of foundation pit support structure is compared and analyzed. Based on the above work, the influence of different shear strength indexes on the safety and stability of foundation pit engineering is obtained. (1) in the design of foundation pit with dewatering measures, soil samples of foundation pit before dewatering are used to test. When designing and calculating, the cohesion force of the test result should be increased properly, otherwise it will cause unnecessary waste. (2) in triaxial test, there are differences between the values of shear strength index under the action of confining pressure and conventional confining pressure, and the cohesive force of soil sample is quite different. The two groups of comparative test values are used in the design of foundation pit support structure, and the calculated results are similar. (3) the shear strength index values of direct shear test and triaxial test are different, and the test conditions of triaxial shear meter are closer to the deformation state of soil sample. The triaxial test value should be selected for the shear strength index of foundation pit design and calculation on the premise of triaxial equipment.
【学位授予单位】：吉林建筑大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU753;TU432

【参考文献】