No abstract

Considering the importance of lining thickness in lining safety, and realizing the synchronization of safety evaluation and information development, this paper combines the methods of literature research and field investigation, focuses on six influencing factors, such as the deterioration of lining materials, the deformation of lining and the lack of tunnel clearance, et al. An evaluation index system of structural safety classification is established, and then substantiates each index and defines its quantitative or qualitative evaluation criteria. Through the normalization processing, the state of the evaluation index can be characterized by the normalized value. Analysing the characteristics, structure, relationship, trend and the mode of their mutual connection between the indexes by set pair analysis method, the calculation formula of the connection degree is obtained, and then the set pair potential vector is obtained. According to the principle of maximum set pair potential, the safety evaluation of lining structure is divided into five levels: safe, safer, less safe, unsafe and extremely unsafe. With the help of App Designer tool in MATLAB software, a program suitable for lining safety evaluation is designed and developed independently. Combined with a tunnel project in Chongqing, the above method is used to judge the lining safety of the tunnel project in order to provide a quick way for tunnel safety evaluation.

No abstract

How to quickly eliminate outburst in long-distance through-coal seam tunnels is one of the major challenges faced by the tunnel industry in mountainous areas. Compared with coal mine rock crosscut coal uncovering, the work surrounding the rock of through-coal seam tunnels has a high degree of breakage, large cross-section of coal uncovering, and tight time and space. In this paper, a method of networked slotting in long-distance through-coal seam tunnels for rapid pressure relief and outburst elimination is proposed. Based on this method, the corresponding mathematical governing equations and numerical simulation models have been established. The optimal borehole arrangement spacing and the slot arrangement spacing obtained by numerical optimization are 2.85 m and 3.1 m, respectively. Field gas production data of through-coal seam tunnels show that compared with the traditional dense-borehole gas extraction, the method of networked slotting in long-distance through-coal seam tunnels for rapid pressure relief and outburst elimination can shorten the extraction time by about 66%, the net quantity of peak extraction is increased by 3.55 times, and the total quantity of gas extraction when reaching the outburst prevention index is increased by 1.26 times, which verifies the feasibility of this method and the reliability of numerical simulation results. This study could be used as a valuable example for other coal deposits being mined under similar geological conditions.