软弱围岩隧道掌子面极限支护压力研究

Study on Limit Supporting Pressure on Excavation Face for Soft Ground Tunnelling

针对软弱围岩隧道掌子面所需支护力,基于极限平衡理论,建立了掌子面稳定性分析模型,采用水平条分法推导了掌子面极限支护力计算公式,依托计划进行全断面开挖试验的宝兰客专洪亮营黄土隧道,求解了试验段浅埋情况下所需的掌子面支护力,并与数值模型计算结果进行了对比,最后,采用离心模型试验验证了理论分析及数值计算结果。研究结果表明:掌子面所需支护力随着土体黏聚力、内摩擦角的增大近似呈线性和非线性减小关系,随着隧道埋深的增大先增加后趋于稳定,覆跨比1是明显分界点;同时理论分析计算得到的最小支护力较数值计算结果偏小,根据离心模型试验和数值计算结果得出,理论公式计算结果的1.5倍可作为软弱围岩隧道掌子面最小支护力。

Aiming at the supporting force required for the excavation face of tunnel in soft ground, this paper, based on the limit equilibrium theory, established a stability analysis model and deduced the formula of the limit pressure on the excavation face based on the level slice method. According to the data from Hongliangying loess tunnel in which a full section excavation test is in plan, the pressure on the excavation face in shallow burial situation was calculated based on the deduced formula. The results were compared with those calculated by numerical model. In the end, a centrifugal model test was conducted to verify the theoretical analysis and numerical results. The study shows that the limit pressure on the face decreases linearly and nonlinearly with the increase of soil internal friction angle and cohesion. With the increase of the tunnel depth, the limit pressure increases first and then becomes relatively stable. The ratio of depth to tunnel span is an important index, and the numberical value of is the critical point. In addition, the minimum pressure calculated by theoretical analysis is relatively smaller than that calculated by numerical calculation. According to centrifugal model test and numerical calculation results, the 1.5 times of the results calculated by the theoretical formula in this paper can be used as the minimum supporting force of the tunnel face in the soft ground tunnel.