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节理的产状和隧道轴线夹角的不同会极大地影响隧道的稳定性。以榆佳高速公路某隧道为研究对象,利用UDEC离散元软件,建立了0°、85°、120°和150°单层层状节理模型,以及由3组层状节理切割的复杂模型;设计了0.2、0.4、0.6、0.8、1.0MPa初喷混凝土接触面黏聚力计算工况,5、8、10cm初喷厚度计算工况。经计算,对比不同工况的塑性区、应力和监测点位移值,发现:单层节理条件下,节理倾角β对隧道稳定影响不大,0°时塑性区最大,最大位移5.6cm,围岩没有掉块,围岩自稳,无需支护;其余倾角隧道均能自稳,位移不大于1cm。黏聚力大于0.6 MPa为临界值,大于其隧道围岩自稳,洞顶位移值小于1cm,否则会出现掉块。初喷厚度8cm为临界值,大于其隧道围岩自稳,洞顶位移值小于1cm,否则会出现掉块。上述特征值均在单因素变化、其余参数参照基准值条件下获取,这些可以作为隧道设计的极限参考值。
The joint shape and tunnel axis angle will greatly affect the stability of the tunnel. Taking a tunnel of Yujia Expressway as the research object, a single-layered layered model of 0 °, 85 °, 120 ° and 150 ° and a complex model of three layered joints were established by UDEC discrete element software. 0.2,0.4,0.6,0.8,1.0 MPa initial shotcrete contact surface cohesion calculation conditions, 5,8,10 cm initial jet thickness calculation conditions. Comparing the displacement of plastic zone, stress and monitoring point under different working conditions, it is found that under the condition of single-layer joint, the inclination β of the joint has little effect on the stability of the tunnel, and the plastic zone has the largest displacement and the maximum displacement of 5.6 cm at 0 °. No block, rock self-stability, without support; other tilt tunnel can be self-stable, displacement of not more than 1cm. Cohesion greater than 0.6 MPa for the critical value, greater than the tunnel wall rock self-stability, the displacement of the top of the hole is less than 1cm, otherwise there will be dropped block. Initial spray thickness of 8cm for the critical value, greater than its tunnel rock self-stability, the displacement of the top of the hole is less than 1cm, otherwise there will be dropped pieces. The above eigenvalues are all changed by one factor, the other parameters are obtained with reference to the reference values, which can be used as the limit reference value of the tunnel design.