Study On Tunnel Construction Risk Evaluation Considering Deformation Standard Of Neighboring Structures

The sharp contradiction between the fast development and large scale of the Chinese tunnels and the underground projects together with the serious safety situation of underground projects decides the necessity and urgency to conduct tunnel risk management. Supported by Postgraduate Innovation Foundation of Hunan Province (3340-74236000004) and Sub-project of R&D project of Railway Ministry (2005K002-D-3), taking Liuyang river tunnel in Wuhan-Guangzhou passenger dedicated line as background, in the dissertation some researches in a technical level and management level is made, such as risk assessment, safety evaluation of adjacent structures and the deformation control standards during construction. The main research contents and achievements are as follows:(1) Expert method, entropy method and hierarchy analytic approaches are combined to put forward the systematic assessment model of man-mechanism-environment for the tunnel risks. Then an open assessment index system is built, the assessment procedure is ensured, and improvement measures are proposed according to assessment results.(2) Deformation control standards under four conditions are studied: no adjacent structures, beneath different type pipes, underpass different highway and neighboring bridges, based on which a risk monitoring and warning system is established. The deformation sensitivity to rock properties is studied by using orthogonal experiments and sensitivity principles.(3) Based on organization and management system in the project department of the contract section XXTJâ…¡, detailed flow chart of risk management with strong operability is put forward as well as risk management of tunnel neighboring structures. Three different risk management levels are established, that is project headquarters, construction unit, and construction frontline staff. Furthermore, a risk warning system based on deformation is developed with Delphi language.(4) An index method and fuzzy theory are applied to evaluate risk neighboring adjacent structures; a new construction method of dynamic subsection benches is originally put forward in the upper-soft lower-hard strata section. Construction safety neighboring structures is assessed through numerical simulation. Furthermore, deformation standard is modified by on-line monitoring results.(5) After detecting geology condition and rock properties in the weathered trough section, principles and inducing reasons of tunnel collapse are analyzed by tunnel mechanics and statistics theory; tunnel collapse risk is evaluated from different aspects using case-based reasoning, extentics theory and strength reducing method. According to assessment results, prevention measures and emergence plan of tunnel collapse are made.