| The life cycle of tunnel structure includes construction stage,service stage and aging stage,and the reliability is the lowest during the construction stage.Because the displacement of the surrounding rock and supporting system is the direct embodiment of various mechanical behaviors and it is also the easiest mechanical behaviors to be measured in the construction stage.So it is considered to be the main basis various to discriminating the deformation and stability of the surrounding rock and supporting system.In view of the difficult problems in the study of tunnel structure reliability,by analyzing the force mechanism and deformation characteristics of the surrounding rock and supporting system,the main factors that affect the stability of the surrounding rock and supporting system are considered as random variables.The deformation stability function of t of the surrounding rock and supporting system based on displacement is established,and the reliability theory is used to analyze and assesse the stability of the surrounding rock support system.Based on this point of view,the following research works have been carried out.1.According to the mechanical characteristics of the surrounding rock and supporting system during the tunnel construction,the deformation mechanism of the surrounding rock and supporting system is analyzed.According to the characteristic curve of the surrounding rock and the characteristic curve of the supporting structure,the deformation stability limit state of the surrounding rock and supporting system in the construction process is clearly defined.The interaction,the instability mechanism and the instability characteristics of the surrounding rock and supporting system is made.The judgments basis for the stability of the tunnel surrounding rock and supporting system is analyzed,and the main factors affecting the stability of the surrounding rock and supporting system is analyzed.2.The factors that affect the deformation stability of the surrounding rock and supporting system is considered as random variables,and the deformation stability is studied by using the reliability theory.The stability of the s the surrounding rock and supporting system is evaluated with the reliability index or failure probability,and the concept of deformation stability limit state and limit displacement of the surrounding rock and supporting system is introduced.The stability performance function and limit state equation of displacement support system is established.3.Based on the analytical solution of the axisymmetric force and non-axisymmetric stress in the circular section tunnel,the empirical formula of the critical deformation related to the instability of the cavern is deduce by the Platt's theory as the limit displacement.The performance function of the deformation stability of the surrounding rock and supporting system of circular section tunnel is established based on the displacement,and the FOSM method is used to calculate the reliability index.The stability reliability index of surrounding rock and supporting system of circular section tunnel is reliable.4.Based on the analytical solution of the displacement of the surrounding rock and supporting system of a circular section tunnel,the critical settlement of the critical circular tunnel is obtained by the elastoplastic theory as the limit displacement.The deformation stability of the supporting system and the surrounding rock of a circular section tunnel is established when the supporting structure is considered and not considered.The deformation stability reliability index is calculated based on vector projection sampling point response surface method.5.For the circular section tunnel when considering the construction process and the analytical displacement solution that cannot be solved,the sensitivity analysis and finite element method are applied to solve the approximate displacement solution of the surrounding rock and supporting system.In order to improve the calculation precision,the sensitivity analysis of the parameters affecting the displacement of the surrounding rock supporting system is analyzed,and the result of the parameter sensitivity analysis is used as the basis for the value of the random variables when the surrounding rock supporting system can be analyzed.The feasibility of the method is proved by engineering examples.6.The sensitivity analysis and finite element method is applied to solve the analytical displacement of the non-circular section tunnel,which considering the construction process and the displacement analytical solution that cannot be obtain.The approximate expression of the displacement of the surrounding rock and support system is solved,and take the recommended value of the allowable circumference in the specification as the limit displacement,and the performances function of the surrounding rock and support system is establish when the specific construction method is considered.The stability reliability of surrounding rock and supporting system of the railway tunnel is analyzed by using artificial neural network. |
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