隧道边仰坡滑塌处治及二次进洞施工技术实例研究

A case study on the treatment and tunneling technology under collapsed tunnel side and face upward slope condition

以太真隧道工程为例,采用现场调查、数值模拟和现场监测技术,针对隧道进洞施工过程中的边仰坡滑塌机理、处治措施以及二次进洞技术开展研究。研究结果表明:软弱地层条件下,强降雨是诱发依托工程边仰坡滑塌的主要原因。雨水下渗弱化岩土体强度,在隧道进洞施工扰动下,形成贯通性塑性带,进而导致山体大范围坍塌。综合考虑滑塌体本身的稳定性以及隧道再次进洞施工的扰动影响,系统性地提出边仰坡处治以及隧道二次进洞方案,包括:适度清除坍塌体、局部刷方减重+抗滑桩、锚索(杆)加固以及反压回填的边仰坡防护措施;基坑明洞法穿越坍塌体、浅埋暗挖法(加强支护结构和采用双侧壁导坑开挖法)穿越塌方影响段的隧道二次进洞施工技术。数值模拟和现场实测均表明,经综合处治后的边仰坡在隧道二次进洞过程中处于稳定状态,上述方案是可靠的。

Based on project of Taizhen tunnel, field surveys, numerical simulations and on-site monitoring techniques were used to conduct specific studies on the mechanism of collapse of side and face upward slope during construction, as well as its treatments, and the following entrance scheme. The main conclusions are as follows: Under soft ground conditions, heavy rainfall is the main reason for the collapse of side and face upward slope, where the strength of rock and soil is weakened by rainwater infiltration. Further, under the disturbance of the following entrance construction, a penetrative plastic band is formed, which indicates that a large area of mountain collapse. Based on comprehensive consideration of the stability of side and face upward slope and the disturbance of the following entrance construction, the treatment of the side and face upward slope and the following entrance scheme are systematically proposed. The treatments include: moderate clearance of the collapsed body, locally overload cutting combined with anti-slide piles and anchor cables (anchor bolts), back fill;And the scheme are as follows: open-cut tunnel method for the collapsed body, shallow tunneling method (reinforced supporting structure and two side-wall pilot tunnel) for the section influenced by the collapsed slope.The result of numerical simulation and field measurements indicates that after the comprehensive treatment, the side and face upward slope is in a stable state during entrance construction, proving rationality of the treatment.