Study On Deformation Characteristics And Control Technology Of Small Clear-distance Tunnel When Passing Through The High Ground Stress Active Fault

As a supplement type of separate tunnel, small-distance tunnel can solve some problems such as large area occupied, more excavation earthwork, line development inflexible, high slope and other issues that separated tunnel has because of its minimum clear distance. Under the condition of the terrain restrictions and formation change, Small clear distance paragraphs will appear during the transition period of double hole separated tunnel and single hole large cross section tunnel, so the study of small clear distance tunnel is becoming more and more important. Because the research work of small clear distance tunnel is not comprehensive, especially the design theory and application for small clear distance across the southwest mountainous and active fault are not mature, so it is unable to meet the needs of practical engineering. The engineering of shiziyuan tunnel in chenglan railway based on in the paper is located in the longmenshan fault zone area, its small clear distance passages through two active fault zones and the tectonic stress is noteworthy, so the surrounding rock and supporting structure is easy to damage in the construction process of small clear distance tunnel. Do some research work about deformation characteristics and stress characteristics of small clear distance tunnel through the combination of numerous methods of field research, theoretical research, laboratory test, stress test, numerical simulation and field monitoring while the tunnel goes through fault fracture zone and local high stress.(1) Made a rather clear idea about stratigraphic lithology, geological structure of shiziyuan tunnel through data collection and field investigation. Evaluated the stress of tunnel site environment by comparing and verifying the results of drilling analysis around and the in-situ stress test, analyzing the effect of in-situ stress on the stability of surrounding rock at the same time. Got the physical and mechanical parameters of surrounding rock through the indoor test of sample and obtain rather reliable mechanics parameters by using H-B criterion.(2) Simulating the construction process of small-distance tunnel by large finite difference software Flac3D to get the corresponding stress characteristics and deformation characteristics under the condition of different construction in the case of obtaining tunnel surrounding rock mechanics parameters and understanding the situation of strata structure features, analyzing the influence on the stability of small clear distance tunnel construction that caused by the change of surrounding rock lithology, tunnel clear distance and horizontal stress factors, then acquiring reasonable stability control technology for small clear distance tunnel to go through the fault zone and high stress environment depending on optimization study of lining structure stress by adjusting the design scheme and construction method.(3) Summarizing the changing rule of the stress and displacement of surrounding rock in practical engineering and the influence law of after hole’s construction on adjacent caverns through the statistical analysis of monitoring data in the process of engineering construction such as the stress, deformation, etc, provided a reference for small clear distance paragraph control technology research of this tunnel and the same type of engineering.(4) Analyzing the reason of crack on the inverted arch of shiziyuan tunnel based on the summary of inverted arch cracking mechanism and treatment measures for existing deep soft rock tunnel, put the cracking section regulation method and construction advise of the subsequent period, achieved good results finally.