Uniaxial compression experiments were carried out for brittle marble with pre-existing fissures by the rock mechanics servo-controlled testing system.

Water burst mechanism was discussed from crack zone height,thickness of effective water barrier in roof and hydraulic pressure of aquifer.

It is very important for disaster pre vention and curing and application o f land to find out the caving zones,crack zones formed after coal exploitation and s ubsidence conditions.

810 mining area, simulation of similar materials and simulated analysis by computer, the hydrogeological feature of quaternary, engineering geological feature of mantlerock, growth of maximum caving zone and cracking zone in this area are analyzed systematically.

It has been therefore suggested that the structural fractures were main location of CO2 accumulation, and that the presence of strike--slip faults resulted in the connection between deep and shallow fracture zone, which lead to the formation of CO2 gas field.

According to the experimental data,the maximal height of fracture zone is 92 m.

The reasonable layer selection is the main influencing factors for gas drainage by high level borehole,the borehole parameters is based on the caving & fracture zone height of gob.