基于总安全系数法的喷锚组合支护承载能力试验研究

Experimental study on bearing capacity of spray anchor combination support based on total safety factor method

为验证总安全系数法中喷锚组合支护的计算模型与安全系数计算方法,从结构试验角度研制大型隧道结构模型试验系统,开展毛洞、不同间距系统锚杆下喷锚组合支护结构的加载试验。采用围岩、细砂材料的三轴试验、锚杆材料的拉伸、拉拔试验,明确模型试验中各材料的物理与力学参数,模拟毛洞与不同锚杆间距下喷锚组合支护的加载破坏全过程,试验中监测获取了围岩应力–应变、锚杆应变、喷层内外侧应变、喷层位移随外荷载的演变规律,分析毛洞、不同锚杆间距下喷锚组合支护的设计承载能力、极限承载能力以及变形受力特征,并与总安全系数法理论计算结果进行对比分析。研究结果表明:喷射混凝土与锚杆能有效地与围岩协同承载,提高围岩的侧限力,发挥锚岩承载拱的支护作用,提高围岩的变形与承载能力;试验得到的喷锚组合支护的承载能力、破坏特征均与理论计算结果较为吻合,表明总安全系数法的喷锚组合支护计算方法是合理的,且该方法偏安全。

In order to validate the calculation model and safety factor calculation method for the combined sprayanchor support in the total safety factor method,this paper developed a large-scale tunnel structure model test system from the perspective of structural test,and carried out the loading test of the spray-anchor combined support structure under the unsupported tunnels and the different anchor spacing.The triaxial test of surrounding rock and fine sand material,and the tensile and pull-out test of anchor material were used to clarify the physical and mechanical parameters of each material in the model test,simulate the whole process of loading and damage of the spray-anchor combination support under different anchor spacing and unsupported tunnels,and monitor the stress and strain of the surrounding rock,anchor strain,inner and outer strain of the spray layer,and the displacement of the spray layer with the external load.Based on this,the design bearing capacity,ultimate bearing capacity,and deformation force characteristics of the unsupported tunnels and the combined spray-anchor support with different anchor spacing were analyzed and compared with the theoretical calculation results of the total safety factor method.The results show that:sprayed concrete and anchor can effectively carry the surrounding rock,improve the lateral limiting force of the surrounding rock,play the supporting role of the anchor rock bearing arch,and improve the deformation and bearing capacity of the surrounding rock;the bearing capacity and damage characteristics of the spray-anchor combination support obtained from the test are more in line with the results of theoretical calculations,which shows that the total safety factor method of spray-anchor combination support calculation method is reasonable and the method is on the safe side.