Stability Analysis And Treatment Research Of A Tunnel's Subsidiary Engineering In Goaf

When the shaft in the excavation process, meeting goaf such complex geological conditions, the stability of the shaft becomes the primary consideration question of design and construction. However this is a deep-rooted problem, and has been a more difficult problem. This topic is then put forward, and provides relevant stability analysis and solution.This paper is taking a tunnel's 1st shaft and the mined-out area as the research target, in adopting means of theoretical analysis, numerical simulation and engineering measurement. The main research contents and results are as follows:(1)Through detailed survey of mined-out area, it can be seen that the subterranean cavitation rate is larger, and it will constitute a certain degree of harm to shaft stability, so should adopt special treatment measures before shaft construction, and treatment difficulty and quantities are bigger. Overall, the goaf stability is bad, and the management grade is 3rd level. Through comprehensive evaluating, mined-out area must be grouted to reinforce it and filling loose rock.(2)Based on accuratly proving-up of goaf, design scheme such as treatment range, grouting quantity and process is calculated and ascertained, and it is changed and optimized to ensure grouting quality.(3)After treatment, according to there checking holes which proved distribution characteristics of goaf's caving and fracture zones, combining indexes of hole's drilling situation, rock core, water-consumption, water-level of eventually hole and the strength and wave velocity values of stone body to judge that grouting effect is better, entity can reachâ…£class surrounding rock strength indexes, ventilation shaft can hereby do corresponding supporting design.(4)By finite element software ANSYS to dynamically simulate shaft's (including goaf) a series process of excavation and supporting, research supporting's state such as force, displacement.And through specific data, knowing that before treatment mined-out area happen plastic deformation, overburden fell and cause surrounding rock extremely unstable, so shaft through it happens deformation, lining structure separate from surrounding rock losing support and hereby destruct; Or because local stress exceed bearing capacity and occur pull-pressure or shear failure. However, after treatment has not occurred plastic deformation damage and internal stress of surrounding rock in mined-out area is uniform.(5)Through numerical simulation analysis about six engineering state of shaft's construction, we can conclude that after treatment displacement and stress which shaft occurs is uniform and stabile and numerical value meets license requirements of engineering. Shaft stability is reliable which can meet the engineering's safety and quality needs. Grouting treatment enhances stability of shaft construction more, so grouting is of great significance.