Study On The Hydromechanically Coupling Effect In Water-rich Jointed Rock Mass During Tunnel Excavation

Tunnel engineering in water-rich fractured rock masses is confronted with a lot of problems.On one hand,the seepage law in joints is really complicated.On the other hand,the hydromechanically coupling effect between the seepage field and mechanical field will increase the difficulty of tunnel construction.Therefore,the study of the seepage characteristics in jointed rock masses is of great necessities.In this thesis,the discrete element method is used to analyze the influence of distribution parameters of joints on the seepage field of tunnels and the hydromechanically coupling effect in jointed rock masses.In addition,hydromechanically coupling effect is analyzed with an engineering example.The main conclusions of the study are listed below:(1)In jointed rock masses,due to the discontinuity of joint distribution,the water pressure behind the liner shows a non-uniform distribution in the longitudinal direction.The water pressure behind the liner at the cross-section intersected with the joint is larger,and the water pressure in the other cross-sections is relatively small.As the joint spacing decreases,the water pressure behind the lining exhibits an increasing trend.(2)When the joint dipping angle is 90°,the distribution of water pressure behind the liner is symmetrical.When the joint dip angle is not equal to 90°,the overall distribution of the joints is asymmetric,resulting in the asymmetry of the water pressure behind the liner.When the joint dipping angle is 45° and 135°,the difference between the left and the right liner water pressure is the greatest.As the joint dipping angle changes from 30° to 150°,the water pressure at the vault and the arch bottom exhibits a quadratic parabola with respect to the dip angle.(3)As the joint aperture increases,the water pressure behind the liner increases.The coefficient of transmissivity of joints is proportional to the cubic of joint aperture.(4)When the hydromechanically coupling effect is considered,the displacements of the vault and the arch bottom increase by approximately 30%.In addition,with the consideration of the coupling effect,the aperture of the joints will increase.(5)When the normal stiffness of joints increases,the displacement of tunnel surrounding rock shows a decreasing trend,and the water pressure distribution behind the liner also become smaller.In addition,the greater the joint stiffness,the smaller the change in joint aperture.