| With the development of tunnel support design theory, New Austrian Tunneling Method has become representation of modern support theory. Especially,because of the application of local monitoring measurement and its combining with theory analysis, New Austrian Tunneling Method has developed into a new design method-local monitoring method (Observational Method) adapting to the characteristic of underground project and current technique degree. At present, local monitoring measurement, dynamic design and dynamic construction have become a kind of developmental trend in the design and construct of tunnel and underground engineering.In this paper, on basis of detailedly illuminating the engineering condition of ZheGu mount tunnel, studying tunnel systematically dynamic and observational with modern monitoring and numerical simulation, there were several important understanding and research results as follows:(1) Systemic, dynamic and observational idea are impenetrated in this paper, and a set of complete research system on stability of surrounding rock is formed.(2) Testing and simulating on the tress field indicates that original stress distributing rule and collective character could be compartmentalized two parts: alteration zone in the surface near sloping and stress calm zone in deep. In the middle of tunnel, maximum principal stress at horizontal is bigger than that at vertical, The magnitude is 17~23MPa, which formed the high stress site.(3) A set of classified scheme is established, and surrounding rock classification fast estimate system based on fuzzy inference is developed, which open a new way for estimating classification of surrounding rock.(4) We gained the stability information of surrounding rock, ensured the zone of move about 1~3 meters and the best support time were 15~22 days in classification IV, 35~49 days in III,and 19~48 days in classification II, by means of monitor and analysis of the displacement, this provides exact information and credible gist for support design and informative construction. On the basis, the rock mechanics parameters is analysed inversively. Its results are: lateral pressure coefficient 1.23~1.31, vertical stress 14~18.4MPa and level maximal stress 22.6 MPa.(5) Analysing the stability of block after excavation in zhegu mount tunnel by using block theory. It indicated the integrated characteristic and general regularity of part block. The instability ways of block were fall at vault and single or double side glide at nance and sidewall.(6) The principal stress direction arised deflexion obviously after excavation, the maximum principal stress paralled to opening, minimum principal stress vertical to sidewall or vault. Theprincipal stress value arised alteration , the magnitude of stress closed to 25~32MPa, its influence scope was within the scope outside of tunnel opening 10~15 meter, maximum tense focused at vault and middle of floor about half meter. Shearing stress focused at corner of vault and wall, always been sheared. Its displacement could reduced to 40 percents at vault and 34 percents at floor in the condition of support, especially in the condition of cable support.(7) The destroyed area came into being in the condition of supports, such as tensile at vault and floor, shearing at nance and corner of wall. Its conclusion that shell was better than cable for preventing destroy of surrounding rock. Shearing destroy are reduced obviously with enhanced support.(8) By monitoring and numerical analyzing, It concluded that the deformation field of surrounding rock went to stabilization after first support. The biggest force of monitoring cable was 130KN(340MPa),it smallest safety factor was 1.25. The biggest force of the piles within 10~ 15KN ,the force of support structure was reasonable. Above all showed that the support design were safe.
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