| More and more tunnels were built in the mountain highway with the development of the highway construction and transportation net.Due to the complicated geological stress-field and different rock-mass construct condition,some engineering disasters took place in the process of tunnel excavation.Such as the failure of tunnel surrounding rock,rock-burst in deep tunnel,seepage and leakage,and so on.To remedy such engineering problems,the author studied deeply and systematically on the prevention and control technology of engineering disaster with the support of the Hunan province transportation science & technology project and the key project of the natural science foundation of China.The main contents of the dissertation are summarized as follows:(1) Based on the principle of distance discriminant analysis theory, a classification model of tunnel surrounding rock was established in this paper and seven indexes reflecting the engineering quality of tunnel surrounding rock were considered.The discriminant functions of model were obtained through training a large set of expansive samples.The re-substitution method was introduced to verify the stability of this model and the ratio of mistake-discrimination is zero.A set of data in two tunnel engineering were used to test the discriminant ability of model and the results show that this model has high prediction accuracy.(2) Based on the principle of Bayes discriminant analysis theory,a discriminant analysis model of prediction of possibility and classification of tunnel rock-burst was established in this paper.Three factor indexes including the ratio ofσθ/σc andσc/σt,and Wet were regarded as discriminant factor of the discriminant model and a series of underground rock projects at home and abroad were taken as the training and testing samples,and the ratio of mistake-distinguish is zero after this model was trained.Rock-bursts of Tongyu tunnel in Cheng-qian highway and Kuo-cang mountain tunnel in Zhu-yong highway were used to verify this model.The results show that the discriminant model can be used to predict the possibility and classification of rock-burst in deep underground engineering and the prediction accuracy is very high.(3) Based on the coupled fluid-mechanics theorem,FLAC3D(Fast Lagrangian Analysis of Continua in 3 Dimension) numerical software has been used for the analysis of mountain multi-arch tunnel design in aquiferous stratum.After tunnel excavation,the groundwater will flow through the rock fissures under the different pore pressure in the network and at last the pore pressure of groundwater has a funnel-shaped distribution in excavation regional.The most leaking places around tunnel concentrate on the vault and the side wall.So it is necessary to make the underground water drain actively.(4) The coupled fluid-mechanics numerical analysis had been done by considering the effect of rock classes,covering depths,underground water tables,construction methods and initial supporting systems.The results show that the surrounding rock classes have most important influence on the stability of tunnels,and so does the tunnel covering depths.The research indicated that the settlement of the vault derived from coupling analysis when considering the seepage flow effect were bigger than that of the seepage flow effect was not considered and the underground water tables influent the stability of tunnels to some degree. Therefore,it is quite necessary to consider the seepage flow effect of the underground water in aquiferous stratum for multi-arch tunnel design.(5) According to the results of theory analysis,the treatment measures which have important pertinence for resolving the problem of tunnel leakage were put forward.The methods include the geology forecast in an aquifer stratum,the technology of grouting and shot concrete with anti-seepage and so on.These treatment measures were adopted to prevent and drain the underground water around the tunnel. The tunnel's construction proved that these measures had achieved a preferable effect to the original design;especially at the places where the leakage always takes place if none treatment measures were adopted.The new gathering and draining groundwater system can gather about 85% underground water which flew into tunnel along the cracks and joint fissures.(6) The measuring results of surrounding displacement was used to analyze the stability of rock-supporting system in multi-arch tunnel.The convergence course of horizontal convergence curves was similar for every section and the difference of final displacement between those convergence curves was very little.Then the modified hyperbola function had been used to regress the displacement convergence curves of surrounding rock.Furthermore,the stability of tunnel was calculated with the formula of fuzzy probability.The present formula and experience could be referenced in the design,construction and researches of similar tunnels.
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