ABSTRACT
The Gaoligong Mountain Tunnel along the Dali-Ruili Railway is the longest railway tunnel in the Hengduan Mountains region in southwest China, with a full length of 34.538 km. It is a single-track railway tunnel with a design operating speed of 140 km/h. The tunnel construction commenced in December 2015. By the end of August 2024, 18.3 km of the main tunnel has been excavated, with 47.1% remaining to be excavated, and the duration has exceeded 27 months. The main tunnel is constructed by TBM and the drilling-blasting method and with “1 parallel heading, 1 inclined shaft, and 2 shafts”. Passing through 17 types of strata and 19 faults, the tunnel is subject to the combined action of multiple factors including geologic tectonic, alteration caused by the intrusion of multistage magma, earthquake, and groundwater. As a result, adverse geological conditions such as mud gushing and water inflow, high geotherm, and large deformation of soft rock are extremely prominent. This paper systematically analyzes the difficulties encountered in tunnel construction. Targeted research has been conducted on the TBM tunneling technology under extremely complex geological conditions, the treatment technology for large-scale, high-pressure, water-rich, arenaceous and pelitic granite alteration zones, the high geotherm prevention and control technology, etc. and these results have guaranteed the tunnel construction safety. In the authors’ opinion, the Gaoligong Mountain Tunnel will still face a series of unprecedented technical challenges. For the subsequent project construction, the authors put forward some technical suggestions to ensure the smooth construction of the main tunnel, such as “putting the parallel heading breakthrough first”, auxiliary advance geological exploration, discharging water for pressure decreasing, and advance pretreatment of adverse geological sections, with a view to providing reference for subsequent projects and similar projects.
