双锚杆受力机制分析及模型试验研究

Mechanism analysis and model test research on double anchor rods

为了研究锚杆间距对全长黏结锚杆之间相互作用产生的影响,推导出基于Mindlin解的双锚杆锚固段应力分布近似解,并结合单锚和双锚静载拉拔模型试验,得到了锚杆间距改变对双锚杆应力分布、极限承载力及最终破坏形态的影响规律。结果表明:间距减小使得锚杆的轴向应力和侧摩阻力呈现均匀化趋势,且轴向应力随间距减小而增大,锚固段中部增长幅度最大。当锚固系统进入破坏阶段,随着间距减小,锚固系统周边岩体破坏的位置深度增加,破坏锥形体的面积增大,并由单锚的倒锥状破坏转变为复合破坏模式。间距过小时,增加锚杆数量对承载力的提升十分有限,为起到锚固联合作用,锚杆间距应不小于10 D(D为锚杆直径),在软弱岩体中间距取值应加大。

In order to investigate the effect of anchor spacing on the interaction between full-length bonded anchor rods,an approximate solution of stress distribution in the anchorage section of double anchor rods based on the Mindlin solution was derived.By combining with the single and double anchor static load pullout model tests,the effect of changing anchor spacing on the stress distribution,ultimate bearing capacity and final damage pattern of double anchor rods were obtained.The results show that the decrease in spacing makes the axial stress and lateral friction resistance of the anchor rods uniform.The axial stress increases with the decrease in spacing,and the middle of the anchorage section has the largest increase.When the anchor system enters the damage phase,the depth of the rock damage around the anchor system increases with decreasing spacing,and the area of the damage cone increases and changes from inverted cone damage of a single anchor to compound damage mode.When the spacing is too small,the increase in the number of anchor rods is very limited for improving the bearing capacity.In order to exert the joint effect of anchoring,the spacing of anchor rods should be not less than 10 D(D is the diameter of the anchor rod),and the spacing should be larger in soft rock.