山岭隧道过破碎岩层开挖面塌方机制与位置预测研究

Study on Mechanism and Position Prediction of Excavation Face Collapse of Mountain Tunnel Passing Through the Broken Rock Strata

依托九绵高速梅家沟隧道,针对隧道施工过程中穿越倾斜破碎岩层时出现的塌方频率高、预警效果差的技术难题,采用FLAC^3D数值模拟的方法对隧道台阶法施工过程进行数值计算,分析不同开挖进尺下,破碎岩层的塑性区深度和主应力场分布,揭示了开挖面塌方机制;建立隧道开挖过程的概化模型,基于薄层单元体受力理论,采用理论分析方法建立了隧道塌方判别体系,对塌方空间位置进行预测。工程实践表明,该判别体系对于隧道过中厚倾斜破碎岩层塌方预测具有较高的准确性,可提前采取针对性的技术措施预防开挖面塌方。本文研究成果对于类似工程施工过程中的塌方预判和塌方空间位置预测提供了科学有效的方法,具有较强的理论价值和社会效益。

Based on the Meijiagou Tunnel of Jiuzhaigou-Mianyang highway,aiming at the technical problems of high collapse frequency and poor early warning effect when the tunnel passes through the inclined broken rock strata,this paper uses FLAC^(3D) numerical simulation method to carry out numerical calculation for the tunnel step method construction,analyzes the plastic zone depth and main stress field distribution of the broken rock strata under different excavation footage,and reveals the collapse mechanism of the excavation face.A generalized model of tunnel excavation process is established,and a tunnel collapse discrimination system is built by theoretical analysis method based on the stress theory of thin-layer unit body,and the spatial position of the collapse is predicted.The engineering practice shows that the discrimination system has a high accuracy in predicting the collapse when the tunnel passes through the medium-thick inclined broken rock strata,and the targeted technical measures can be taken in advance to prevent the collapse of the excavation face.The research results of the paper provides a scientific and effective method for the prediction of collapse and space position in the process of similar engineering construction,and has strong theoretical value and social benefits.