Application Of Advanced Geological Prediction In Diversion Power Tunnel Excavation Of Xu Jixia Reservoir

Tunnel construction tends to be long in length and deep in burial.However,the accuracy of general geological exploration can hardly meet the requirements of modern construction.In order to prevent disasters,the importance of advanced geological prediction becomes more and more prominent in tunnel excavation.Based on the reservoir gorge diversion power tunnel project,this paper uses seismic wave reflection method to carry out geological advance prediction of adverse geological conditions such as tunnel stratum contact surface,tectonic fractured zone and karst development zone.Combining with geological survey report and advanced geological drilling,the prediction accuracy and reliability are improved,and the accuracy of the results is verified by actual excavation.The advanced geological prediction results are applied to the finite element numerical simulation to study the stress and displacement distribution of the surrounding rock of the diversion power tunnel.The specific work is as follows:(1)Through the advanced geological prediction technology of TGP,geological advance prediction is made for the bad geological conditions such as stratum contact surface,tectonic fracture zone and Karst Development Zone of the diversion and power generation tunnel of the reservoir gorge.The comparative study of overlapping data and results of TGP advanced geological prediction can enhance the reliability of TGP advanced geological prediction technology.Combining with geological prospecting report,it is more accurate to judge the bad geological body in front of the palm and to classify the surrounding rock.(2)Comparing the results of advanced geological prediction of TGP with the actual situation of surrounding rock excavation,it is found that advanced geological prediction of TGP can meet the requirements of construction accuracy of deep and long tunnels.By forecasting the results of section 4+924-5+074 of mileage pile number,it is found that there is a reflection interface at section 5+024 of mileage pile number on the face of the palm,and the negative reflection intensity is high.This indicates that there is a bad geological body and the tunnel axis is cut at section 5+024.After actual excavation,a weak interlayer is found at section 5+024.(3)The accuracy and reliability of the advanced geological prediction of TGP are verified by geological advanced drilling.Using geological drilling in the 4+880-4+900 section of Mileage Pile No.4,it is found that the lithology of the formation has not changed.The lithology is sandy slate,which contains a large amount of groundwater,and there are fractured strata or weak interbeds in the strata.The predicted results are the same as those of TGP.(4)By establishing the finite element model based on the data measured in advance geological prediction,and using the numerical simulation method to study the stress and displacement distribution law of surrounding rock of diversion power tunnel,it is found that the maximum stress of the tunnel reaches 5950 kPa and the displacement is 67.75 mm.