砂卵石地层圆形深基坑排桩支护结构受力特征

Mechanical Characteristics of Retaining Piles with Circular Beams for Round Deep Foundation Pit in Sand-Cobble Soils

平面为圆形的深基坑工程近年来逐渐出现在以砂卵石地层为主的成都平原地区,其支护结构型式多为排桩结合圈梁构成的排桩框架结构。这种空间结构受力较为复杂,针对工程实际的迫切需要,基于数值模拟方法,依托成都某圆形深基坑工程,分析了排桩框架结构的内力和变形特征及桩径、桩端地层、基坑直径等因素对其的影响规律。结果表明,围护桩后侧土压力接近三角形分布,可采用Rankine理论近似计算,结果偏于安全,误差约为30%;围护桩具有双向弯曲特征,冠梁和腰梁均以轴向受压为主,腰梁受力较大;随着坑径增大,作用于围护桩上的土压力先减小后增大,其间存在使土压力最小最佳坑径。

In recent years,circular deep foundation pit project has gradually emerged in Chengdu plain area consisting mainly of sandy cobble strata. The support structures are almost retaining piles with circular beams connecting their tops and waists. This spatial structure is in complicated mechanical status. In order to meet the urgent need for practical engineering in Chengdu City,characteristics of internal forces and displacement of the structure and influence of pile diameter,strata surrounding pile bottom,pit diameter on retaining piles are analyzed by numerical simulation method. The results show that earth pressure on a pile is approximately of triangular distribution,which is close to Rankine active earth pressure. The latter is more than the former and the error is about 30 percent. The Pile has bidirectional bending,and the top beam and waist beams are mainly in axial compression but axial force of waist beams is larger than that of top beam. As the pit diameter increases,the earth pressure on the retaining pile is first decreased and then increased,while there is an optimal pit diameter to lead to minimum earth pressure.