Study On Lining And System Reliability During Construc-tion Period Of Highway Mountain Tunnel

Structural reliability of highway tunnel is one of the difficult and hot spots in tunnel en-gineering and draws extensive attention of the scholars at home and abroad. The engineering practice has showed that long term reliability of highway mountain tunnel depends on reli-ability of support and lining structure during construction period. Qualitative evaluation and quantitative calculation of structural reliability are important contents for reliability research of highway tunnel structure, but a few researches have been done in such fields by now due to the limitation of calculating tool and theoretical research. Structural reliability and sensitivity is studied using probability finite element method. Further more, lining and structural system reliability of highway tunnel during construction period is discussed. Safety of tunnel struc-ture is analyzed based on field test and laboratory model test. Besides, fuzzy matter-element evaluation method with entropy weight is put forward for comprehensive reliability analysis of lining structure. Detailed research works done in this paper are summarized as follows:1. Uncertainty factors which have influence upon structural reliability of highway tun-nel are analyzed comprehensively and some computational methods of structural reliability are discussed detailed. Discrete methods for random fields and probability finite element methods are introduced based on definite finite element methods. Continuous medium model is selected as the mechanical model in structural reliability analysis for anchor bolt-shotcrete support and concrete lining structure. Latin hypercube Monte Carlo method combined with continuous medium model is put forward to highway tunnel reliability. Furthermore, prob-abilistic reliability of lining structure is calculated based on one highway mountain tunnel.2. Sensitivity analysis method of spearman rank correlation coefficient based on field test and simulated experiments are used to calculation of sensitivity of tunnel structure. Main and minor factors which have influence upon structural reliability of tunnel support and lining are analyzed according to the result of sensitivity calculation. Suggestions for improve the structural reliability are put forward according to the characteristics of highway mountain tunnel.3. System failure modes of highway tunnel structure are discussed from three different levels. Consequently, reliability block diagram of tunnel structure system is set up and meth-ods to improve tunnel reliability of the whole structure system are disscussed. Wide bounds method, probabilistic network evaluation technique and Monte Carlo method combined with response surface method are used to calculate system reliability of the whole highway tunnel. Besides, applicability, robustness and efficiency of all calculation methods discussed above are compared by an applicable example.4. Variation of tunnel failure with time is studied and the discrete process is established according to variable loads and structural resistance. Accordingly, approximate calculation of time-dependent reliability is put forward. Operation status is discussed and Markov chain of highway tunnel system is established with the theory of stochastic process. Besides, the transfer processes of operational status are analyzed detailed. Furthermore, time availability is used to express the reliability level of highway tunnel structure according to experience of tunnel construction, which is in accordance with the practice well.5. Field test of tunnel support and lining structure is done in large scale during con-struction period of Maijishan tunnel which belongs to Tianshui-Baoji expressway. Based on structural safety, bolt axial force, surrounding rock pressure, grid steel frame stress, varying regularity of concrete strain and contact stress of anchor bolt-shotcrete support with concrete lining are discussed and structural reliability of support and lining is analyzed. Also, variation of concrete stain with time is studied according to field tests of concrete lining using fiber grating sensors. Forces between surrounding rock and supporting structure are tested and its characteristics are got using laboratory model test. Damage characteristics of lining structure and limit bearing capacity are analyzed based on laboratory overload test. Furthermore, result of model test and field test are compared with the calculation result of probabilistic reliability.6. Based on non-probabilistic reliability, fuzzy matter-element evaluation method with entropy weight is put forward according to fuzzy matter-element theory. Evaluation model of reliability with Hierarchical structure is established after a thorough and systemic analysis of main factors which has a large effect on structural reliability of highway tunnel. Weights of assessment factors are calculated combining the subjective weights determined by analytic hierarchy process method with the objective ones determined by the entropy method. Ac-cordingly, the lining structural state of one highway tunnel is determined according to the calculation of correlation degree. By using the method combining calculation of probabilistic reliability with non-probabilistic reliability analysis, the reliability evaluation result of high-way mountain tunnel is more reasonable, comprehensive, systemic and scientific.