深基坑支护双排桩计算模型的改进

当锚索超出规划红线被越来越严格限制后，双排桩支护的应用已越来越多。实践中发现现有规范方法的双排桩计算模型简单方便，但对于软土地层时存在计算位移不够合理的情况。同时，桩间土简化为压缩弹簧未能充分考虑桩和土柱之间的作用，会使计算位移偏大。为改进这些不足，建议了一个新的土压力模式，即基坑面以下的附加压力看作弹性应力，对两排桩与桩间土的作用增加一个等效土柱刚度，对基坑面以下的桩间土弹簧刚度取压缩刚度和m法刚度的大值，使计算的位移更合理，并与有限元和工程实测结果进行了比较，初步检验其合理性。

Improvement of calculation model of double-row piles for supporting deep excavation

When the situation that the anchor is over the planning red line is restricted, the double-row piles supporting for excavation has been widely used. The practice shows that the calculation model of double-row piles in current specifications is simple and convenient, but for the soft soil excavation the calculation results of displacements are not well reasonable. Meanwhile the same time, the soil between piles is simplified as compression springs and the effect of pile and soil column is not fully considered, which makes the calculation results of displacement larger. In order to improve these deficiencies, a new earth pressure model is proposed that the additional pressure under the foundation pit is regarded as elastic stress, the equivalent soil column stiffness is added to strengthen the pile-soil interaction, the larger value of spring stiffness under the foundation pit between compression stiffness and stiffness of “m” method is chose, which is to make the calculating displacements more reasonable. At last it is compared to the results of the finite element method and the engineering tests, and its rationality is preliminary verified.