地下水封洞库施工巷道开挖对仰坡稳定性的影响规律

巷道或隧道开挖对洞口仰坡稳定性有重要影响,处理不慎极易酿成工程事故。以山东某地下水封洞库施工巷道洞口风化花岗岩仰坡为研究对象,基于离散元模拟和监测数据,选取仰坡最大位移、塑性区体积及稳定系数作为评价指标,研究了巷道开挖进尺、断面尺寸及W值(上覆地层厚度与巷道跨度之比)对仰坡稳定性的影响。结果表明:随着开挖进尺的增加,坡面最大位移增长速率呈匀速—加速—稳定的变化规律,塑性区体积不断增大,且开挖断面越大,位移、塑性区增长速率越大;仰坡稳定系数随进尺的增加先降低后趋于稳定,且断面尺寸越大其降低速率和幅度越大,最终降低幅度为6.9%~27.6%;随着W值增大,仰坡稳定系数先降低后趋于稳定,降低速率随断面尺寸增大而增大,根据特定断面下稳定系数降低速率不同,将关系曲线划分为骤降区、缓降区、陡降区和平稳区。研究结论可为类似工程洞口段划分、施工及稳定性评价提供参考。

Influence Law of Access Tunnel Excavation on the Stability of the Entrance Slope of Underground Water-Sealed Cavern

Tunnel excavation has an important effect on the stability of the entrance slope,which is very possible to lead to engineering accidents.Based on discrete element simulation and monitoring data,the maximum displacement of slope,the volume of plastic zone and stability coefficient were taken as the evaluation indexes in this paper.It studied the influence of excavation footage,section size and W value(ratio of overlying strata thickness to roadway span)on the stability of a weathered granite slope at the entrance of underground water-sealed tunnel in Shandong province,China.The results showed that with the increase of excavation footage,the maximum displacement growth rate of slope presented a constant,accelerating and stable change rule,and the volume of plastic zone increased continuously.Moreover,the larger the excavation section was,the greater the growth rate of displacement and plastic zone was.With the increase of footage,the slope stability coefficient first decreased and then tended to be stable.Moreover,the larger the section size were,the greater the reduction rate and range of the stability coefficient was,and the final reduction range was 6.9%~27.6%.With the increase of W value,the slope stability coefficient first decreased and then tended to be stable,and the reduction rate increased with the increase of the section size.According to the different reduction rates of the stability coefficient,the relationship curve was divided into the sudden drop area,slow drop area,steep drop area and stable area.The research conclusions provided reference for similar projects to determine the scope of the portal section,construction and stability evaluation.