Research On The Prediction And Prevention Of Rockburst Of Cuihuashan Super Long Tunnel In Qinling Mountain

The21st century is a new period, in which underground space such as tunnels andmines around the world are exploited and utilized on a large scale. The fast developmentof Chinese economy brings forward an austere test to the transportation capacity. Moreand more underground projects in complicated geological conditions are beingconstructed or having been constructed, the geological disaster-rockbursts, whichcaused by excavation unloading of tunnel engineering, has became the key problem ofthe safe construction of tunnel.With a length of over11271m and a buried depth of625m, Cuihuashan super longtunnel is located in the north of Qinling. The surrounding rock of tunnel body is hardrock, and the geological structure is complex. Geological exploration data obtainedindicate that the tunnel cross several―V‖shape valley and the rock mass is under highgeostress, and rockburst may occur during the construction of the tunnel. Forecastingthe region, section and intensity level of rockburst, proposing reasonable preventionmeasures and thus to ensure the tunnel construction safety, are the key problems duringthe construction of Cuihuashan super long tunnel.Combining the specific geologic regions of the Cuihuashan super long tunnel, thewhole line of the tunnel is divided into12working conditions to do finite elementanalysis. According to the criterion of rock burst adopted, rock burst proneness of thewhole line is evaluated in this paper. Choosing each kind of situation of strong rockburstand weak rockburst, the effect of surrounding rock softening and primary supportmeasurements on rockburst prevention is numerically investigated. Then, combining therockburst field tests of D1K73+860~D1K73+940section, the character of rockburst issummarized and the rockburst prevention scheme is determined, and the specific effect of rockburst prevention measurements is analysised. Finally, rationalization proposals ofrockburst prevention are proposed, which the measurements of combining rocksoftening and primary support are adopted in moderately strong rockburst region, andmeasurements of taking rock softening as the main and primary support as thesubsidiary in weak rockburst region.