考虑空间效应的深基坑双排桩支护结构计算模型

A calculation model for double-row-pile retaining structures in deep foundation pit considering 3D effects

建立一个考虑空间效应的深基坑双排桩支护结构计算模型。该模型具有如下特点:可计算基坑某一长度范围内每根桩顶处的冠梁刚度系数,给出冠梁的弯矩、位移分布;通过杆系有限元法计算任意开挖深度情况下桩身的内力和位移;可考虑任意排距(包括排距为零,即退化为一排桩)以及前排桩、后排桩长度不相同等情况下桩身的内力和位移。基于这一模型,编制了设计计算软件。计算结果表明:在基坑边壁中点处冠梁水平位移大于其它位置的位移,且随开挖深度的增大位移逐渐增大;在支护结构桩顶部,冠梁的作用限制了水平位移的发展,而支护结构桩的中部则有较大的位移;此外,随冠梁刚度系数的增大,桩体的水平位移明显减小,而弯矩则增大。计算结果与现场实测资料对比表明,两者变化规律具有较好的一致性。

A model for double-row-pile retaining structures which considers three dimensional effects of deep foundation pit was proposed. This model has the following characteristics： the stiffness coefficient of top beams along the side of a foundation pit can be calculated, and the displacement and bending moment distributions of top beams can also be obtained; the stresses and displacements along the piles can be calculated using finite element method, including any pile distance （zero pile distance is considered as a single row） and different pile length between the two rows. A calculation program is developed based on the above model. The results show that the horizontal displacements of the top beam are bigger in the middle of the pit side than those at other locations, and the horizontal displacement also increases along with the depth of excavation. The displacements at the top of piles are smaller due to the effects of the top beams, but the displacements at the half height of the piles increase along with the excavation depth. Besides, with the increase of the stiffness coefficients of top beams, the displacements of the piles decrease and the bending moments in piles increase. The calculation results are in good agreement with the measured data in-situ.