变截面底端扩体型锚杆在粉质黏土中的承载特性模型试验研究

Experimental Study on Bearing Characteristics of Variable Cross-section Bottom-end-expanded Bolt in Silty Clay

为了研究粉质黏土中变截面底端扩体型锚杆的承载特性,通过改变扩体下段的直径、土体含水率、围压等条件进行锚杆拉拔试验,与普通锚杆、等截面底端扩体型锚杆的承载特性进行对比,并根据已有的等截面底端扩体型锚杆承载力公式估算出n阶法组合的变截面底端扩体型锚杆极限承载力公式。结果表明:在围压与土体含水率不变的条件下,变截面底端扩体型锚杆的极限承载力远高于普通锚杆;当扩体下段直径不变时,变截面底端扩体型锚杆的极限承载力大于等截面底端扩体型锚杆;在围压不变条件下,随着土体含水率增加,变截面底端扩体型锚杆极限承载力随之减小;在含水率不变的条件下,变截面底端扩体型锚杆极限承载力随着围压的增大而增大;对于含水率较高、围压较低的地质环境,增加扩体下段直径能有效提高锚杆极限承载力。

In order to study the bearing characteristics of variable cross-section bottom-end-expanded bolt in silty clay,the bolt pull-out test was carried out by changing the diameter of the lower expansion section,soil moisture content,confining pressure and other conditions,and the bearing characteristics were compared with ordinary bolt and constant cross-section bottom-end-expanded bolt. According to the existing formula of bearing capacity of constant cross-section bottom-end-expanded bolt,the formula of ultimate bearing capacity of variable cross-section bottom-end-expanded bolt combined with n-order method was estimated. The results show that under the condition of constant confining pressure and soil moisture content,the ultimate bearing capacity of the variable cross-section bottom-end-expanded bolt is much higher than that of the ordinary bolt. When the diameter of the lower expansion section is unchanged,the ultimate bearing capacity of the variable cross-section bottom-end-expanded bolt is greater than that of the constant cross-section bottom-end-expanded bolt. Under the condition of constant confining pressure,with the increase of soil moisture content,the ultimate bearing capacity of variable cross-section bottom-end-expanded bolt would decrease. Under the condition of constant water content,the ultimate bearing capacity of variable cross-section bottom-end-expanded bolt would increase with the increase of confining pressure. For the geological environment with high water content and low confining pressure,increasing the diameter of the lower expansion section can effectively improve the ultimate bearing capacity of the bolt.