Advance Geological Prediction And Deformation Mechanism Of Tunnel Under Complex Geological Conditions

In the construction of long-buried long tunnels,bad geologic bodies such as fracture zone,karst and water-rich zone are often encountered,and these complex geologic bodies are often not known or handled improperly in advance,eventually leading to water flooding and instability in the face of the hand,or even it is a serious accident such as landslides and burial.Once these above-mentioned geological disasters occur,the quality of engineering accidents and the progress of construction will lag behind.On the other hand,there will be a large number of casualties,damage to the tunnel itself,and major economic losses.According to the geological survey data of the Niuyu'nanping Tunnel in this project,there are water-rich zone,fracture zone and fissure zone in the local tunnel strata,and there may even exist complex geology such as caverns.In order to ensure the smooth construction of the tunnel construction task and avoid or reduce the accidents caused by the above complex geological bodies during the construction of the tunnel,advance geological forecasting technology was introduced into the projectconstruction.Based on the work of advanced prediction of Niuyu'nanping Tunnel,combined with relevant research results at home and abroad,the basic principles and applications of advanced geological prediction are comprehensively studied.Through the project overview of the tunnel and combined with the construction experience of the previous tunnel,the use of geological radar equipment for field exploration,and then carry out related geological prediction work of the tunnel.After comparing the radar detection results with the characteristics of the surrounding rock exposed after the tunnel excavation,it is finally verified that the advanced forecasting geological radar method is more ideal fortheabovecomplex geological body detection results,and thedetectionaccuracy can reachat least 80%.For the karst problems encountered in this project,the FLAC3 D software was used to simulate the caverns with different shapes and locations during tunnel excavation.Through analysis and research,the general rule of the effect of caverns of two shapes and five locations on excavation deformation of surrounding rock under the condition of the same length and approximate volume is: When the cuboid and cylinder caverns appear on the left and right side of the face When the location near the wall is near,the influence on the deformation of the surrounding rock on the face is small;when the two kinds of karst caves are located near the vault and the invert,the deformation after the excavation of the surrounding rock is very large;the cuboidal cave is in five positions.The maximum value of deformation displacement of the surrounding rock is slightly larger than that of the cavern.The resulting numerical simulation results can be applied to the adjustment of tunnel support forms and parameters andthe improvement ofconstruction techniques.