Numerical Simulation Of Deep Rock Mass Excavation Unloading Under The Corrosions

With the rapid development of social economy, more engineering have been to the scope of deep rock mass. The use of underground space has become the trend of The Times development at present. Rock mass excavation is unloading process, and the unloading response is different from the loading process. It is difficult to use ordinary load strength criterion and the destruction theory to explain of unloading destruction. Multi field coupling was the unique environment of deep rock mass excavation. When deep rock mass affected by groundwater corrosion, the mechanical properties were changed, and then deformation of rock mass excavation and stress were influenced. Numerical simulation of deep rock mass under the action of corrosion was put forwarded in this paper.Based on the physical model test of deep rock mass excavation in the paper, finite element models of the rock mass excavation were established and ANSYS software was used in numerical simulation, and compared with physical model test. Numerical simulation program was as follows: the size of the models was 30×30 m, the excavation roadway is a 2.6 m diameter half arch tunnel. The rock parameters that the model needed, boundary conditions, the layout of anchor rod, key points of layout and so on were determined. And then considered the three factors such as corrosion condition, corrosion rate and depths, a total of 26 finite element models were established. The deformation of deep mass excavation, the stresses of surrounding rock, the analysis of the bolt support, the displacement at key points and so on were research and analyzed. The results were got as followings:1) The work researched on numerical simulation of deep corrosion deep excavation was carried out by the way of finite element software preferably. The simulation results were accorded with the actual engineering situation. And the way had the advantages of strong practicality, economy, operability, etc.2) In the process of rock mass excavation, the depth of excavation was what affected deformation of roadway and the forces of surrounding rock most, the corrosion conditions was second, the corrosion degrees was the last. Deformation of the tunnels and stress of surrounding rock were increased with the increase of excavation depth. Considering the influence of the corrosion conditions, the strong acids corrosion influence had the most impact, acid corrosion was next, neutral salt corrosion and water corrosion were smallest and the effect after of the corrosions was little difference. Roadway’s distortion was reduced as the order: strong acids corrosion, acid corrosion, neutral salt corrosion, water corrosion, no corrosion. And it was reduced with drop of corrosion degrees as well. The stress values of surrounding rock such as first principal stress, the third principal stress, von Mises stress and shear stress were inverse relationship compared with deformations.3) Excavating deep rock mass were prone to rock burst, generally it was occurred in both sides of the semi-arch and the bottom of the roadway. The deeper the roadway excavate, the more obvious the rock burst phenomenon was. The scope of rock burst was decreased with the corrosion degree increased. But the influences in the same depth were little difference. The rock burst of roadway was affected by different corrosion conditions. In the action of strong acids corrosion, the rocks in inside tunnel was biggest damaged, acid corrosion was second, no corrosion is minimal.4) The deformation of surrounding rock was controlled and reduced by rock-bolt effectively. After researching and analyzing the stress of the anchor rod,it was found that steel bar stress values were peaked in the vault, spandrel, bottom point of the tunnel. The rock-bolt stress values were small change from vault to spandrel; the values were decreased rapidly from spandrel to bottom points; and the values were increased from the point to the middle of the tunnel bottom quickly. The influence of acid effect of bolt reinforcement stress was the largest, acid corrosion was second, neutral corrosion and water corrosion were minimal.