Study On Key Technology Of Shallow Buried Tunneling In Water-rich Surrounding Rock

As tunnel construction under shallow buried and water-rich conditions is often faced with greater technical difficulty and high security risk, it is of theoretical importance and practical value to research the key technical problems that exist in tunnel constructions under this condition systematically. So, we carried out a systematic study on the key technical problems existing in a tunnel which crosses the shallow buried and water-rich section in this paper. The research methods included case research, theoretical analysis, numerical simulation and field measurement. The researches are based on the Zhifanggou shallow buried and water-rich section of Manchuanguan Tunnel, which is the key controlling engineering of Shangman highway. The research results are as follows:(1) Aiming at Zhifanggou shallow buried and water-rich section of Manchuanguan Tunnel, we did research on the feasibility of digging method scheme. By the comparative analysis on the two kinds of construction schemes—digging method and cut and cover method, combined with the result of case research, we can see that the use of digging method scheme can guarantee construction security and have incomparable advantages in construction period, investment and environmental protection compared with cut and cover method scheme. Therefore, digging method scheme was recommended as the construction scheme to cross the Zhifanggou section.(2) Aiming at Zhifanggou shallow buried and water-rich section of Manchuanguan Tunnel, these two kinds of digging method plans—bench method and single side-wall pilot method, were numerically simulated and the results show that: Single side-wall pilot method has certain advantage on controlling rock deformation, but both bench method and single side-wall pilot method could control the rock deformation within the allowable range. Considering the ease of construction, investment and other factors, bench method was proposed as the construction plan. And furthermore, the supporting measures of bench method were determined. Single-layer small duct grouting was set to reinforce the formation ahead, with small pipe length 4.5 m, spacing 30 cm, proper upper bench excavation progress 1.5 m.(3) For the bench method as proposed in this paper, the fluid-structure interaction simulation results of the tunnel construction process show that: Compared to not considering the role of groundwater, the ground settlement, crown settlement and tunnel convergence calculated by fluid-structure interaction simulation considering the role of groundwater flow significantly increased, and the numerical value of ground settlement considering the impact of groundwater is closer to measured results, indicating that groundwater has significant effect on the safety of tunnel construction.(4) Based on engineering analogy and theoretical analysis, drainage measures, surface reinforcement program and construction scheme of drilling and blasting method were proposed in Zhifanggou shallow buried and water-rich section, by which we ensured the water discharge effect, enhanced the stability of the upper strata and controlled the effect of the blasting vibration effectively. During the construction process, the tunnel surrounding rocks were stable, the deformation was small, and no accidents like collapse took place. The successful and safe construction of the Manchuanguan Tunnel verifies the correctness of research results mentioned above.