基于强度折减动力分析法的围岩稳定性研究

为获得隧道爆破开挖后围岩的稳定性及临界失稳破坏形态,文章以兴泉铁路金井隧道为工程依托,采用强度折减动力分析法原理,结合特征点位移是否突变、塑性区是否贯通、计算是否收敛这三种动力失稳判据,对隧道掌子面围岩进行动力安全系数分析,研究在不同开挖方法、不同开挖进尺、不同围岩等级下爆破对隧道整体安全系数的影响。研究结果表明:全断面爆破开挖的安全系数约为上下台阶开挖的0.96倍;开挖进尺越小,整体安全系数越大;围岩等级越高,爆破开挖下隧道掌子面围岩的稳定性越好;隧道爆破后毛洞安全系数均大于1.30。为了使隧道爆破开挖后围岩更加安全稳定,可以选取上下台阶爆破方法和减小开挖进尺的手段。

Study on Stability of Surrounding Rock Based on Strength Reduction Dynamic Analysis Method

To obtain the stability and critical instability failure mode of surrounding rocks after tunnel blasting excavation,based on Jinjing Tunnel of Xingquan Railway,the dynamic safety factor of surrounding rocks of tunnel face is analyzed by using the strength reduction dynamic analysis method in light of the three dynamic instability criteria,i.e.,whether the displacement of characteristic point is abrupt,whether the plastic zone is through and whether the calculation is convergent,and the effects of tunnel blasting on overall safety factors under different excavation methods,different advance rates and different surrounding rock grades are studied.The results show the safety factor of full-face blasting excavation is about 0.96 times of that of upper and lower bench excavation;the smaller the advance rate,the larger the overall safety factor;the larger the surrounding rock grade,the better the stability of surrounding rock of tunnel working face under blasting excavation;the safety factor of tunnel with no support after blasting is greater than 1.30.The stability of tunnel working face is quantitatively evaluated by safety factor,and reduction of advance rate and upper & lower bench blasting excavation method can be adopted in order to make the surrounding rocks be more safe and stable after excavation.