静钻根植能源桩承载特性模型试验研究

Model test on bearing characteristic of static drill rooted energy pile

为了研究静钻根植能源桩在热-力耦合作用下的承载特性,采用自行设计模型试验系统,测试模型桩在黏-砂双层地基中的热力响应。试验结果表明:桩体温度沿深度变化并不均匀,对桩周土的温度影响半径为3倍桩径;3次冷热循环后桩顶和桩周土表面均产生累积沉降,在桩顶荷载达到单桩极限承载力的25%时,桩顶累积沉降达到桩径的3.12‰,是桩顶无荷载情况下的1.77倍;模型桩附加温度应力沿深度分布均表现为中间大两端小,位移变化零点(附加温度应力最大处)随着桩顶荷载增大(约束增强)而上移,桩顶荷载较小时降温引起桩身局部产生拉应力。因此,静钻根植能源桩的承载特性与温度变化条件、桩顶荷载大小和桩端约束条件密切相关,在工程设计中需要综合考虑以确保运行安全性。

In order to study the bearing characteristic of static drill rooted energy piles under thermo-mechanical coupling conditions, a self-designed model test system has been used to evaluate the thermal response of the model pile in the clay-sand double-layered foundation. The results show that the temperature of the pile is non-uniformly distributed along the depth, and the radius of thermally affected region around the pile is 3 times of its diameter. Accumulated settlements are observed on the pile top and the surrounding soil surface after 3 heating-cooling cycles. Driven under the load of 25% of the ultimate bearing capacity on top, the cumulative settlement of single pile reached 3.12‰ of the pile diameter, which is 1.77 times that of the pile top under non loading condition. Larger additional thermal stress performs at the pile middle than both ends, and the null point(where lies maximum additional thermal stress) moves upward with the increase of the pile top load. In fact, it has been observed that under small load on the top, local tensile stress occurs in the pile body due to cooling. Therefore, the bearing characteristic of static drill rooted energy pile is of high relevance to temperature change, load on pile top and stress boundaries of pile ends, and that requires comprehensively consideration in engineering design to guarantee safety service of pile.