锚固长度对锚杆受力影响分析及其临界值计算

Influence of anchorage length on stress in bolt and its critical value calculation

基于锚固界面的一种非线性剪切滑移模型,采用荷载传递方法分析了锚固长度对锚杆受力特性的影响,建立了锚杆临界锚固长度的计算方法,并通过工程案例检验其可行性。结果表明:锚固长度较小时,锚杆荷载-位移曲线为承载力较小的单峰曲线;随着锚固长度的增加,逐渐衍生出一个平缓变化区段;锚固长度越小,界面剪应力分布越均匀,但整体承载力也越小;随着锚固长度增加,界面剪应力分布的不均匀特征逐渐明显,整体承载力也随之提高;锚固长度超过一定取值时,锚固界面软化荷载、抗拔荷载以及整体承载力均趋于定值,与锚固长度无关;计算得到的临界锚固长度与工程实际的锚固长度具有较好的一致性,验证了方法的可行性。

Aiming at the influence of anchorage length on stress conditions in bolt as well as the calculation method for its critical value, a nonlinear stress-slipping model of anchorage interface was introduced to develop shear stress, axial force and displacement solutions of bolts using load transfer method. The influence of anchorage length on stress conditions in bolt, mainly including load-displacement relationship, shear stress distribution as well as softening load and ultimate bearing capacity, was discussed. The calculation method for critical anchorage length was proposed and verified by the engineering applications. The results indicate that the load-displacement relationships of bolts with small anchorage length perform as unimodal curves with low bearing capacities. A slowness changing of the segment aroused accompanying with the increasing of anchorage length. Shear stress distributes uniformly along bolts with small anchorage length and the bearing capacity is very small. The non-uniform characteristics occur with the anchorage length increase and the bearing capacity also increases. The softening loads, ultimate bearing capacities and the bearing capacities of bolts approximate toward constant values after the anchorage length reaches critical value. The calculation results of the critical anchorage lengths show good agreement with the actual values in engineering cases for bearing tests, thus this proposed method is feasible and effective.