Abstract To meet the reinforcement and protection needs for high steep side and front slopes and high-positioned dangerous rockfalls at railway tunnel portals in difficult mountainous areas, based on field survey and mapping, comprehensive exploration, and design practice, this study conducts research on the type classification, major challenges,and control measures for high steep side and front slopes at tunnel portals. The results show that high steep side and front slopes can be divided into four types: shallow cover type, rock exposed type, shallow cover-rock exposed type,and rock exposed-shallow cover type. High-positioned, steep, and concealed side and front slopes face three major challenges: difficulty in surveying and identification, high difficulty in treatment, and difficulty in material and equipment transport and construction. For dangerous rock development areas, the alignment of the railway tunnels should preferably bypass these areas. If bypassing is not feasible, the tunnel entrance should be selected according to the order: "straightly through the ridge → diagonally through the ridge → straightly through the slope → diagonally through the slope," with strict prohibition of setting tunnel portals in valleys or troughs. High-positioned, steep and concealed side and front slopes should adopt integrated "space-air-ground" exploration and identification method, and large-scale surveying should be conducted along ridges or vertical slopes. For unstable high-positioned covered side and front slopes, it should be checked, calculated and designed according to landslide engineering. For prevention and control of dangerous rockfalls, it should follow the principle of "priority removal → active reinforcement → passive protection." The control and prevention works should be considered as part of the overall project along with tunnels, bridge abutments, etc., with the construction sequence following "top-down construction, first protective works, then main tunnel and bridge works."
Abstract：
To meet the reinforcement and protection needs for high steep side and front slopes and high-positioned dangerous rockfalls at railway tunnel portals in difficult mountainous areas, based on field survey and mapping, comprehensive exploration, and design practice, this study conducts research on the type classification, major challenges,and control measures for high steep side and front slopes at tunnel portals. The results show that high steep side and front slopes can be divided into four types: shallow cover type, rock exposed type, shallow cover-rock exposed type,and rock exposed-shallow cover type. High-positioned, steep, and concealed side and front slopes face three major challenges: difficulty in surveying and identification, high difficulty in treatment, and difficulty in material and equipment transport and construction. For dangerous rock development areas, the alignment of the railway tunnels should preferably bypass these areas. If bypassing is not feasible, the tunnel entrance should be selected according to the order: "straightly through the ridge → diagonally through the ridge → straightly through the slope → diagonally through the slope," with strict prohibition of setting tunnel portals in valleys or troughs. High-positioned, steep and concealed side and front slopes should adopt integrated "space-air-ground" exploration and identification method, and large-scale surveying should be conducted along ridges or vertical slopes. For unstable high-positioned covered side and front slopes, it should be checked, calculated and designed according to landslide engineering. For prevention and control of dangerous rockfalls, it should follow the principle of "priority removal → active reinforcement → passive protection." The control and prevention works should be considered as part of the overall project along with tunnels, bridge abutments, etc., with the construction sequence following "top-down construction, first protective works, then main tunnel and bridge works."
CHEN Weizhi LI Anhong WANG Hong YAO Yuchun
.Control Measures for High Steep Side and Front Slopes at Railway Tunnel Portals in Difficult Mountainous Areas[J] MODERN TUNNELLING TECHNOLOGY, 2025,V62(1): 56-65
2025, Vol. 62 