土遗址用变径木锚杆锚固机理数值模拟研究

基于室内拉拔试验的物理模型,利用FLAC3D建立变径木锚杆拉拔数值计算模型,分析了变径木锚杆锚固系统的荷载传递规律、界面剪应力分布和传递规律、浆体土体应力场和位移场,并通过数值试验研究锚孔直径、锚杆直径和锚固长度对锚固效果的影响。研究结果表明:数值试验结果与室内拉拔试验结果较为吻合,证明数值模拟木锚杆拉拔过程的可行性和科学性;木锚杆浆体界面剪应力沿锚固段分布不均,主要集中在锚固段顶端和末端的0.1m范围内,末端界面剪应力呈增大的趋势与其变径的结构特征有关,其变径的特点在一定程度上提高了木锚杆的抗拔力;变径木锚杆同时具有拉力型和压力型锚杆的特征,径向具有剪胀作用;锚固影响因素中锚孔直径、锚固长度对木锚杆抗拔力影响显著,而锚杆直径对其影响相对较小;提出了木锚杆极限抗拔力计算公式。

Numerical simulation of anchoring mechanism for wood bolt with the variable diameter used in earthen sites

Based on the physical model of laboratory pull-out test,a numerical calculation model of wood bolt with the variable diameter was established by means of FLAC3D.The load transfer mechanism,the interfacial shear stress distribution,the stress field and displacement field of slurry were analyzed.The influence of anchor hole diameter,anchor diameter and anchorage length on anchoring effect were studied by the numerical simulation experiment.The results show that Q-S curve from numerical simulation is in agreement with that from laboratory pull-out test,which proves that the numerical simulation on wooden bolt pull-out process is feasible and scientific.The interfacial shear stress distribution along wood bolt with the variable diameter is uneven,and shear stress mainly concentrates among the distance of 0.1m at the top and the end of anchorage section.Structural characteristics of bolt leads to the increasing trend of shear stress near the anchor end.Furthermore,it strengthens the anchor capacity of wood bolt with comparison to regular bolt.The wood bolt with the variable diameter has the characteristics of tension-type and pressure-type bolt,and radial dilation is another feature.Compared with anchor diameter which has little impact on anchor capacity,the anchor hole diameter and anchorage length have significant influence on the pullout capacity.The formula for the ultimate pullout capacity for wood bolt with the variable diameter is proposed.