Study On Situ Monitor And Evaluation Technology For Surrounding Rock Pressure Caused By Overbreak Or Underbreak During Tunnel Construction

The accident of supporting structure become invalid and lead to failure often happens during tunnel construction, sometime will caused injuries and deaths. There exist big difference between supporting structure geometry and earth pressure theory, and this is the main reason why supporting structure become invalid. On the base of situ monitor and evaluation technology for surrounding rock pressure caused by overbreak or underbreak during tunnel construction is an important approach to distinguish and forecast supporting structure become invalid. Combined with important communication project of Jiangxi province" situ monitor and evaluation technology for earth pressure of surrounding rockmass caused by overbreak or underbreak of dysmorphism tunnel structure"(No.:2009-21), and on the base of situ monitor and statistics; census; numerical statement; vital statistics: census; vital statistics, a on line monitor system of whole section earth pressure has been developed, and then an reliability analysis and safety forecast method for dysmorphism tunnel structure has been established in this paper. The main content includes followings:(1) On the base of situ monitor and statistics, the regular pattern of circumferential, longitudinal deformation profile and earth pressure of dysmorphism tunnel structure has been disclosed. The results show that, range of circumferential deformation is big, and influence factors are complicated, and random probability model is instable; under restrict conditions, the regular pattern of situ earth pressure becomes bad, compared with theoretical value, the monitor value has big difference.(2) The regular pattern of circumferential, longitudinal deformation profile has been disclosed with ANSYS. The conclusion has been gained, i.e. if the are area become thinner, and side wall become thicker, the mechanical performance will be better; during construction, the overbreak in the area between arc roof and spandrel and the underbreak in the area of side wall should be restricted.(3) According to mountain deformation sensor, an new pressure dispersing sensor has been made to monitor the earth pressure, and an new on line monitoring system of earth pressure of whole tunnel section has been established, this has realized the earth pressure of whole tunnel section will be monitored in the whole time. The index of this system are:the circular distance among data sites smaller than20cm, in single300m tunnel, the number of the monitor sections is15,inspection cycle is shorter than5minutes.(4) On the base of geometry parameters of supporting structures and earth pressure of whole section, the two hinged arch mechanics model of dysmorphism supporting structure has been established, and section inner stress calculation formula has been inferred, the calculation program has been compiled. The surrounding rock pressure of dysmorphism supporting structure will be fast monitored.(5) Combined with Monte Carlo random theory, reliability model to analyze the surrounding rock pressure of dysmorphism supporting structure has been established. On the base of Grey system, forecast model of surrounding rock pressure in dysmorphism supporting structure has been put forward, and an effective approach to predict the rockmass safety has been formed.