Abstract:

Fifteen kinds of engineering geological problems, i.e. highpressure waterrich karst, large deformation of soft rock, large deformation of archaean metamorphic hard rock,collapse and mud burst of alteration and weathered broken rock, large scale mud burst from fracture zone, large scale collapse of layered strata, collapse of midpleistocene series old loess, mud and sand inrush from neogene system strata, combustion and explosion of combustible gas in mud rock and shale, sand gushing of shear cracks in dolomite, ground settlement of karst, surrounding rock deformation of anhydrite strata，surrounding rock deformation induced by the interaction of fault fracture zone and soft rock, deformation and collapse induced by vertical joints of neogene system silty clay, and water and sand gushing from fault fracture zone in quartz sandstone, are analyzed by taking more than 30 typical tunnels for examples.The causes and characteristics of the mentioned geological problems are analyzed. Discussion are made on 14 kinds of problems, i.e. classification of highpressure waterrich karst, water and sand inrush and large deformation of fault fracture zone, countermeasures for high pressure groundwater, line selection, code for large deformation and its classification, squeezing and unloading large deformation, unsymmetrically loaded tunnel, comparison among 5 kinds of surrounding rock instability, field measurement of tunnel surrounding rock pressure, ground collapse of karst, collapse induced by seepage from vertical joint of Q2 old loess and N2 clay, rheology of weakly consolidated N2 strata， lining cracks of tunnel in anhydrite strata and combustible gas from noncoal strata. Six suggestions have been given in terms of construction legality, geological uncertainty, special geology work, bad rocks, revision of surrounding rock classification and code collection.

Key words: railway tunnel, engineering geology, engineering example, geological disaster