Abstract:

The treatment for tunnels under special geological conditions is the main problem for tunnel construction. In this paper, the main difficulties and their countermeasures for tunnel construction under special geological conditions are summarized and studied. They include: (1) For the problems caused by karst, i.e. irregular karst development and be prone to water and mud gushing, the countermeasures include selecting lines in high position, draining as soon as possible, releasing pressure, making hydrogeologic evaluation and dynamical design. (2) For the problems caused by waterrich fracture zone, i.e. unstable surrounding rock and be prone to water and mud gushing, the countermeasures include draining and releasing pressure in advance, supporting and reinforcing the ground in advance. (3) For the problem, be prone to large deferment, caused by soft rocks with high crustal stress, the countermeasures include controlling the deformation of surrounding rock actively, carrying out supplementary support rather than dismantling, and carrying out rapid excavation, supporting and closing as early as possible. (4) For the irregularity and randomicity of rockburst, the countermeasures include improving the physicomechanical properties of surrounding rocks, adjusting stress conditions and reinforcing the surrounding rock. (5) For the problems caused by Tertiary waterbearing sand, i.e. unstable water condition and be difficult to dewater and grout, the countermeasures include dewatering both on ground surface and in tunnel, disturbing the ground and then grouting to reinforce the ground, and supporting in advance. (6) For the problems caused by high ground temperature, i.e. deteriorated environment and lower working efficiency, the countermeasures include sprinkling water, ventilating, laying ice cakes, mechanically cooling, and personnel protecting. (7) For the problems caused by harmful gas, i.e. risks of burning, outburst and exploring, countermeasures include ventilating, monitoring and inspecting, equipping explosionproof equipment, and implementing safety production management.

Key words: karst,  , water rich fracture zone,  soft rock with high crustal stress,  , rockburst,  , Tertiary water bearing sand,  , high ground temperature,  , gas, railway tunnel