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Analysis of vertical bearing capacity of single pile foundations considering spatial variability of soil parameters
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摘要: 岩土体是自然界的产物，其性质具有较大的空间变异性。在已有土体随机场模拟研究成果基础上，考虑了土体强度参数的变异系数和相关距离，通过数值方法研究了竖向荷载作用下土体空间变异性对桩基础承载力的影响。结果表明，考虑土体空间变异性后，桩基承载力的中值都小于确定性分析得到的桩基承载力；随着变异系数和相关距离的增大，桩基承载力的不确定性越来越大，实际工程中需重点关注土体参数变异性大的工况。考虑土体强度参数空间变异性的桩基竖向承载力分布规律可以用对数正态分布曲线来描述，当样本数足够多时，可依此获取任一荷载下桩基础的失效概率。Abstract: Geotechnical materials are products of the nature, and their properties have great spatial variability. Based on the existing research results of soil random field simulation methods, considering the variability coefficients of soil strength parameters and correlation distance, the influences of soil spatial variability on the vertical bearing capacity of the pile foundation under vertical loading is investigated by the numerical method. The analysis results show that the median value of the bearing capacity of the pile foundation is smaller than that obtained by deterministic analysis, considering the spatial variability of soil. With the increase of coefficient of variation and the correlation distance, the uncertainty of the bearing capacity of the pile foundation becomes more and more. It is necessary to pay attention to the large variability of the soil parameters in practical engineering. The distribution law of the vertical bearing capacity of the pile foundation considering the spatial variability of soil strength parameters can be described by lognormal distribution curves. When the number of samples is enough, the totality can be inferred from the samples, and the failure probability of the pile foundation under any load can be obtained accordingly.
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图 2 样本容量对桩基竖向承载力均值及标准差的影响曲线
Figure 2. Curves of influences of sample capacity on mean value and standard deviation of vertical bearing capacity of pile foundation
图 3 竖向荷载作用下桩基础荷载-位移曲线
Figure 3. Load-displacement curves of pile foundation under vertical loading
图 4 桩基础承载力累计分布曲线
Figure 4. Cumulative distribution curves of vertical bearing capacity of pile foundation
图 5 承载力均值与土体强度参数变异系数关系曲线
Figure 5. Relationships between mean value of bearing capacity and variability coefficient of soil strength parameters
图 6 承载力标准差与土体强度参数变异系数关系曲线
Figure 6. Relationships between standard deviation of bearing capacity and variability coefficient of soil strength parameters
表 1 工况设置及编号
Table 1. Test programs and numbers
变异系数/% 相关距离/m 水平 竖向 水平 竖向 水平 竖向 8 4 8 8 16 8 10 X8Y4Cov01 X8Y8Cov01 X16Y8Cov01 20 X8Y8Cov02 30 X8Y4Cov03 X8Y8Cov03 X16Y8Cov03 40 X8Y8Cov04 50 X8Y4Cov05 X8Y8Cov05 X16Y8Cov05 
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