低强度模拟锚固材料抗弯荷载-位移全过程曲线试验研究

Experimental study of complete load-displacement curve of low strength analog anchoring material in bending process

在大比例尺的地质力学模型中,由于相似模型材料的脆性和低强度,很难测得其抗弯应力-应变或者荷载-位移全过程曲线。对抗弯试验的过程进行力学分析,通过对增加辅助弹性元件方案的假设推导得到弹性元件刚度设计原则。依据该设计原则,组装出一台试验原理样机,测到不同节理(均质、层状和块状)含不同角度锚杆的试件的抗弯荷载-位移全过程曲线。此外,由于相似材料的低强度重度大特性,试验中适当考虑试件的自重对实验结果的影响。试验研究表明,弹性元件的增加对抗弯荷载-位移全过程曲线下降段有着质的改善;当弹性元件与台架的复合刚度大于试件的最大刚度,即可测得抗弯荷载-位移全过程曲线;在抗弯试验中试件自重荷载可以等效为集中力荷载,对于550 mm的标准试件其等效荷载相当于其自身重力1/2的集中荷载,相当于试验中均质试件峰值荷载的9%。

In large-scale geomechanical model,because of the fragility and low strength of similar model material,it is difficult to get its complete bending stress-strain curve or load-displacement curve.This paper performed mechanical analysis on the bending experiment process,and got the stiffness designing principle of elastic element through some derivation for the solution of increasing the auxiliary elastic element.Based on this principle,we assembled a test prototype and obtained complete bending load-displacement curves for the specimens with different joints(homogeneous,layered and massive) containing different angles bolt.In addition,the dead weight of specimen was considered in the experiment due to the similar material's characteristics of low strength and bulk density.Experimental studies have shown that,the increasement of elastic element has a noteworthy improvement for the decreasing segment of the complete bending load-displacement curve.When the composite stiffness of the elastic element and prototype system is greater than the maximum stiffness of the specimen,the curve can be measured.The dead weight of specimen can be equivalent to the concentrated force in the bending experiment,and the equivalent load for the 550 mm long Standard specimen is 50% of its own weight or 9% of the peak load in homogeneous specimen's experiment.