Research On The Numerical Simulation Of The Construction Process Of Changjiashan Tunnel Through The Coal Strata And Gob

As the enlarging investment of highway building in our country, some of highway tunnels are inevitable to cut through the coal strata and gob. But there are a little of tunnels that have been built under the similar engineering geology condition, and the experience of design and construction of them is lack. Based on the Changjiashan tunnel which is an important project of the highway from Qixian to Linfen in Shanxi province, this thesis systemically analyzed the character of engineering geology and the rock's deformation of the coal gob, and analyzed the effect of the excavation and support to the stability of the tunnel in differ classification of surrounding rock from I to IV and in coal gob condition using numerical simulation method. For the selective support scheme, the character of the stress field and the deformation field, and the distributing of the plastic field of each excavation procedure in differ engineering geology condition is worked out.The analyzing result of the numerical simulation can conclude as follows: (1) The plastic field area of the I ,II and III surrounding rock are colsely correlated with the excavation procedure, and the stability of the I ,II and III surrounding rock are easy to be disturbed. Among the excavation procedure, the excavation of the lower section has the biggest impact on the stability of the tunnel. Because of the good the stability of the IV surrounding rock, although the tunnel was fully excavated the plastic field area was few, and the plastic field area is disappeared when the tunnel is supported. (2) On the premise of the thesis, the excavation procedure and the support scheme of Changjiashan tunnel are both feasible. (3) In the coal gob field, the mining is simulated firstly, and then the backfilling of the gob, next the excavating of the tunnel. From the result of the simulation it can be seen: â‘  there still has complex stress field after the backfilling of the gob and bigger stess concentration nearby the coal column; â‘¡ after backfilling the gob, no matter the gob is above or beneath the tunnel,the effect on the stability of the tunnel of each excavation procedure is similar to the effect of the I surrounding rock; â‘¢ when the gob above the tunnel, it has more complex effect on the tunnel than beneath it. Because of the obvious stess concentration nearby the coal column, the relation between the coal column and the tunnel has great effect on the stability of tunnel. It can produce unsymmetrically load when it is nearby the arch of the tunnel.