Simulation Calculation of Excavation and Support Design for Shallow-Buried Soft Rock Underground Powerhouses
In the excavation of shallow-buried soft rock underground powerhouses,the low compressive and tensile strength of soft rock can lead to significant deformation and instability of the surrounding rock if not properly supported.This paper,based on an underground powerhouse of a hydropower station abroad,employs finite element simulation to analyze the excavation and support of the cavern.Initially,the analysis focuses on deep-buried tunnels using the Mohr-Coulomb yield criterion to calibrate the variation patterns and accuracy of yield zones under different residual cohesion and friction angles.Subsequently,the excavation of the underground powerhouse is simulated.The results indicate that the plastic zone is concentrated near the weak surrounding rock,expanding along the dip direction.Lower residual cohesion and friction angles will increase the yield range of the surrounding rock and the number of yielding units in rock bolts.When the residual friction angle of the surrounding rock is tanφ'=(0.7～0.9)tanφ,and the residual cohesion is not less than 0.5 times the original,the maximum deformation of the surrounding rock ranges from 18 to 31 cm.Based on the original design,measures such as pipe-shed support,sheet piles,and rock mass replacement are used to control deformation at key parts of the cavern.Simulation results show that the deformation of the surrounding rock is controlled,meeting stability requirements.
underground powerhousesurrounding rock stabilityshallow-buried soft rockresidual strength
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