Study On Space-time Evolution Laws Of Surrounding Rockmass Deformation In Deep Mixed Strata Tunnel Excavated By TBM

To solve the problem of space-time evolution law of rock deformation in deep mixed strata by TBM, the space-time evolution law was studied by use of digital photogrammetry technology and artificial plaque making method. Using numerical simulation software called FLAC3 D, threedimensional model of TBM tunnel in deep composite formation was established. The impact of the support form, buried depth, tunneling speed, over break clearance, advance supporting strength, driving speed, supporting time, compound formation form on the stability of surrounding rock was analyzed. Main research results are as follows:(1) Through digital photogrammetry technology, the temporal evolution law of interior deformation and cracking in roadway model of transparent rock was obtained. Firstly, with the increase of load, the rock at the roadway roof would probably present integrity shear slip along the two arcs on both sides of the roadway hance inclining upward towards the inside of the roadway itself eventually. Secondly, the rock radial displacement on the left wall, right wall and roof was eonential attenuation relationship with load.(2) Using the new experiment technology of transparent rock, the deformation and cracking law of the profile were obtained. Firstly, with the increase of load, the rock in front of the working face in the range of 25 mm and the top rock would present slide down as a whole, outside the 25 mm, rock would slide inclining downward to the tunnel along the arc line in the direction of 55 degrees arc. Secondly, the upper rock in the center line along the line of 30°arc to slide into the tunnel. Thirdly, the horizontal displacement of rock in front of the working face was double eonential attenuation relationship with the load of tunnel. Fourthly, arc shear zone appearred in front of the working face and the model boundary.(3) Using experiment method of common similar material, upper-soft lower-hard ground was analyzed with digital photogrammetry eeriment. The experimental results showed that disturbed zone in surrounding rock appeared and two shear bands detected in the surrounding rock, a vertical to the soft and hard strata cross boundary, and another with soft ground at the junction of the coincidence on the top of the line, resulting in the general shear failure at the top of rock.(4) Using FLAC3 D finite difference software, space-time evolution law of rock deformation in deep mixed strata by TBM was obtained. Firstly, the plastic zone of TBM formed an “X” type where shear failure mainly occurred. Secondly, displacement of surrounding rock increased with depth which was linear relationship. When computing steps increased, the proportion of the unbalance released by the excavation was not increasing, the impact on the stability of the surrounding rock was small. The bigger overcut was and the longer the time lag of the support, the greater the deformation of the tunnel surrounding rock was. Thirdly, TBM tunneling made working face space effect, and stratum deformation occurred in front of the excavation face of 3 times square hole scope, the displacement of working face had reached to 55 percent of the total displacement. Fouthly, TBM shield area surrounding rock supported by the excavation front side for the excavation of rock, suppresses the move to the tunnel surrounding rock in the area.