承台约束和竖向荷载对双桩水平承载力影响的研究

RESEARCH ON THE EFFECTS OF CAP CONSTRAINT AND VERTICAL LOAD ON HORIZONTAL BEARING CAPACITY OF DOUBLE PILES

实际工程中桩基不仅承受竖向荷载,而且桩顶受到承台的约束,因此采用桩顶自由条件下的单桩水平承载力作为设计依据难以充分反映桩基在水平荷载下的实际工作状态。目前关于承台和竖向荷载对双桩及群桩水平承载性能影响的研究还比较少。为探讨承台约束和竖向荷载等因素对双桩水平承载力的影响,进行了10组现场水平静载荷试验。试验结果表明:桩顶约束对双桩承台短边方向水平承载力的影响不明显,而对长边方向的水平承载力有明显影响;水平受荷方向对双桩水平承载力有明显影响,其中承台长边方向的水平承载力明显大于短边方向的水平承载力;承台长边和短边方向的双桩水平承载力对桩顶竖向荷载的响应不同,当竖向荷载在3倍单桩竖向极限荷载范围内时,两个方向的双桩水平承载力均明显提高。

Due to the existence of vertical load and cap on the top of pile foundation in practice, it is hard to reflect the real behavior of pile under lateral load in pile foundation design according to the lateral bearing capacity of single pile with free head. There were few research concerning factors which affect the lateral bearing capacity of pile group. In order to study the effects of vertical load and cap constraint on the lateral bearing capacity of double piles, ten groups of lateral static load test in field were carried out. The test results showed that the influence of cap restriction on lateral bearing capacity of double piles corresponding to the short side of cap was little, but the influence was significant on the long side;the effect of lateral load action direction on the bearing capacity of double piles was obvious, and the bearing capacity corresponding to the long side of cap was much larger than that of the short side;the lateral responses of double piles to vertical load corresponding to different directions of lateral loading were different, and the lateral bearing capacities in both long side direction and short side direction were significantly increased while the vertical load was within 3 times vertical ultimate load of single pile.