Characteristic Experiment Of Deformation Failure And Field Application For Overlying Rock Of Shallow Double Arched Tunnel

With rapid transport infrastructure construction, more and more highway tunnels are being built in our country. Due to appearance of smooth, less cover area, and bridge and tunnel easily convergence, double arched tunnel becomes more and more popular. But it ususally has a large span and its construction process cumbersome, there are still some difficult problems in its design and constrution. In this paper, it takes Changchengling double arched tunnel as the engineering background, applies model test, numberical simulation and field test to study the characteristics of overlying rock deformation failure.Firstly, based on the similarity principle, a large-scale three-dimensional geomechanical model test which takes Changchengling Tunnel as engineering backeground was carried out in the laboratory. In the model test, the main mechanics parameters are monitorde by testing instrument, and the mechanical variation characteristics can be analyzed by the monitoring data. Then, a numberical simulation is also implemented to silmulate the model test tunnel excavation phase by using FLAC3D. Through comprehensive analysis of experimental data and simulation results, the mechanical behavior of shallow double arched tunnel during excavation was summaried in the conclusion.Secondly, based on the model test of the first part, a geomechanical simulation test of overlying rock collapse for shallow double arched tunnel was carried out in the following part. Through artificially simulating the collapse conditions, weakening the support and imposing disturbance, the geomechanical rock collapse simulation test showed the whole collapse phase; then, the UDEC software was used to simulate the phase. After a comprehensive analysis of the experimental phenomena and numerical simulation results, the construction recommendations are proposed.Thirdly, because seepage water is a common and difficult problem in double arched tunnel, especially for the V-shape area upon middle wall, the third part mainly show the influence of ground water seepage on double-arch shallow tunnel. By using UDEC software, the numerical simulations with discrete fracture network seepage model is carried on. Based on the simulation results, we propose that it can improve the rock mass by cement grouting and construct middle wall with four steps of waterproofing and drainage measures.Finally, field tests are carried on in Changchengling Tunnel. After the above-mentioned recommendations were put into practice, site monitoring measurements and electric resistivity measurement test are implemented. The monitoring and measuring data can show the displacement, ground settlement and stress changes, which can guide tunnel construction. The electric resistivity measurement can reveal the extent of rock damage during the construction phase.