Research on the Influence of Confined Karst Caves at Different Positions on Tunnel Construction
As a typical adverse geological condition,a confined karst cave is prone to water and mud burst disasters due to the increase of formation seepage and the development of plastic zones during tunnel construction near it,which poses a threat to the safety of tunnel construction.With the Jinyan Tunnel project as an example,this paper uses numerical simulation to study the displacement and seepage characteristics of strata and tunnel structures in close proximity to the confined karst cave at different positions(the vault,the side wall and the bottom of the arch).The results show that the maximum surface settlement is 3.10 cm,3.00 cm and 2.93 cm,respectively when the karst cave is at the vault,the side wall and the bottom of the arch,which indicates that the surface deformation is the most dangerous when the krast cave is at the vault,while the krast cave at the bottom of the arch has the least impact on the stratum disturbance caused by tunnel construction,and that with the approach to the face,the seepage velocity of strata gradually increases,and it increases sharply when approaching the face.In the three working conditions,the extreme value of seepage velocity is 0.026 cm/s,0.027 cm/s and 0.030 cm/s,respectively,with the maximum seepage velocity at the bottom of the arch,which is caused by the largest buried depth and the maximum pressure head of the karst cave at the bottom of the arch.When the confined karst cave is close to the side wall of the tunnel,the plastic zone of strata penetrates to the krast cave,and combined with the distribution of formation seepage,it can be seen that this working condition is most prone to water and mud burst disasters.
Confined krast caveTunnel constructionFluidsolid couplingPlastic zoneWater and mud inrush
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