桩锚支护体系中锚杆冻胀响应规律试验研究

Experimental study of frost heaving response of bolt in pile-anchor supporting system

为研究桩锚支护体系中锚杆在冬季冻胀作用下的作用机理,保障深季节冻土区基坑越冬施工的安全,采用物理模拟试验方法和准分布式光栅串测试技术,研究了锚杆受力随着冻深发展的演化规律.结果表明:冻结初期,随着冻结时间增加,冻深基本呈现线性增加规律(33.6μm/min);冻结变形增大之前,即冻结前期230min内,会经历一个锚杆应变整体缩小的阶段,即冻缩现象,最大冻缩应变量约200×10-6;冻结过程中,从自由段到锚固段,随着锚杆受到的约束不断增大,锚杆变形逐渐减小.桩锚支护体系中锚杆的受力随着环境温度的改变会经历受力反复增减的过程,且冻结引起的锚杆受力大约是静止阶段的10倍以上,需要考虑冻结对桩锚支护体系整体稳定性影响.

To ensure the safety of the deep foundation construction in seasonally frozen soil region,the mechanism of deep foundation pit supporting system with anchors and piles under frost heaving during winter was studied by adopting the method of physical simulation and FBG grating array tests.The evolution of anchor rod acting force with the development of frozen depth was also investigated.Results show that at the early stage of freezing,the frozen depth increases linearly with the frozen time at 33.6μm/min.Before the freezing deformation enlarges,namely during the early 230 min,it usually experiences a freezing shrinkage like an overall shrinking phase,with the maximum freezing shrinkage of about 200 micro-strain.From thefree section to anchoring section,the bolt deformation decreases along the growing constraints in the process of freezing.In conclusion,the bolt force of deep foundation pit supporting system with anchors and piles usually goes through a process of repeated changes along the variation in ambient temperature,and the bolt force caused by freezing is about 10 times more than that in the stationary phase.Therefore,the effect of freezing on integral stability of pile-anchor support system should be considered.