Study Of Meta-Synthesis Prediction Methods On The Rock Burst And Large Deformation In The Daba Mountain Tunnel

Rock burst and the large deformation are common underground geologicalhazards under high stress. Rock burst is a sudden ejection of rock crack phenomenon,its sudden and bearing on the dynamic characteristics causing a huge security risk onthe underground constructors; The large deformation disasters not only delayconstruction period, and caused a sharp increase in project costs. Therefore, take theappropriate forecasting method to rock burst and the large deformation and make theright prediction, is a top priority to ensure take the prevention and disposal measuresto ensure the construction schedule and the safety of the constructors. And the existingprediction methods are based on the prediction of a single index, this is actually notcomplete understanding of rock burst and the large deformation, natural predictedresults is far from the actual situation. Therefore, the research on the meta-synthesisprediction of rock burst and the Large deformation has important significance on theprediction of underground engineering disasters.Based on the comprehensive research results of former scholars and thecollection of relevant data, this paper provide a comprehensive analysis of factorswhich affect the rock burst, and do the corresponding correction for the selection ofthe rock burst meta-synthesis prediction index by using a combination of qualitativeand quantitative analysis. Establish a corresponding set pair analysis and theefficiency coefficient method for a number of domestic underground rock burstoccurred inversion, select the typical tunnel section rock sample, and do thecorresponding physical and mechanical tests of multiple index to predict rock burst ofdaba mountain tunnel base on Meta-Synthesis method;On large deformationprediction using by geological judgments which type of large deformation will occurs,and then selecting different predictors and weights according to different largedeformation types, study predictors and the weights of this method, finally using theFAHP and efficiency coefficient to predict large deformation of daba mountain tunnelbase on meta-synthesis method.Get the following findings:1. The common rock burst influence factors are: ground stress, lithology, theburied depth, rock mass structure, groundwater, geological structure and theconstruction technology. But what is the most impact on the intensity of rock burst arerock mechanics characteristic, ground stress and the rock mass structure. 2. Strength-stress ratio( c 1 R s )in the stress criterion of rock burst only themaximum principal Stress is considered. But the rock burst mainly caused by stressdifference, so stress-strength ratio( MAX q c s s ) is more reasonable than strength-stressin the rock burst prediction. The experiment proved that rock fragilitycoefficient( c t s s )and rock burst proneness index( ET W ) are related, and thecorrelation coefficient achieves 90% in mechanical properties of rock burst. So it ismore reasonable to choose ET W as the prediction index.3. Generally speaking,the forecasting precision of set pair analysis andefficiency coefficient method utilizes in the prediction of rock burst are high,so thetwo methods are feasible. The merits and faults the two methods are:the rock burstprediction based on efficiency coefficient method considered fully effect of the weightof evaluation Index,on the contrary, set pair analysis is ignored it, although the idea ismore simple, the accuracy is low.4. Daba mountain tunnel on the geological survey found that some sections indeep lots, with high stress and lithology have more complete slightly weatheredsiliceous dolomite and so on. Summing up all the geological conditions, dabamountain tunnel has rock burst. Use efficiency coefficient method and set pairanalysis to predict the tunnel prove that daba mountain tunnel has rock bursttendency,The length of middle rock burst which accounts for 11% of the length of thetunnel, the length of slight rock burst which accounts for 19% of the length of thetunnel. Feedback through the field situation, prediction results and actual condition isidentical.5. Establish different evaluation systems for different types of large deformation,and analysed the index and weight for each a large deformation types. establishmentof FAHP and the efficiency coefficient method to predict that daba mountain tunnelhave large deformation tendency. The length of middle large deformation whichaccounts for 11% of the length of the tunnel, the length of slight large deformationwhich accounts for 12% of the length of the tunnel. Feedback through the fieldsituation, prediction results and actual condition is identical.