Study On Water Pressure Distribution Laws Along Crack Located At Gravity Dam Heel Under Earthquake

Study on crack at concrete gravity dam heel has been listed as a hot research issue during the past few years,nevertheless hydraulic fracturing at concrete gravity dam heel has been also noted by worldwide scholars. The paper studied on gravity dam's cracking by using finite element simulating software ADINA which was used to establish the numerical analysis model. On that basis, it was studied on the influence on rigidity of gravity dam with different crack depth, crack location and crack direction set at crack position factitiously, especially, the changing regularity of crack and character of water in crack were researched under seismic action. The main tasks and results of this paper are as following:(1) This paper selecte engineering case and establish 2D concrete gravity dam models for numerical analysis with concrete model by ADINA. On that basis, it is studied on the influence on natural frequency of gravity dam with different crack depth, crack location and crack direction. The results indicate that for the same crack direction, the longer the depth of the crack,and the lower the natural vibration frequency would be;for the same crack depth and direction, the more the early crack close to the bottom,the higher the natural vibration frequency would be;for the same crack depth and location,the natural frequency increases with crack angle.(2) Tthe solid and fluid element are established based on the fluid-solid coupling function of ADINA ,then the changing regularity of crack and character of water in crack are researched with different crack depth and crack direction set at dam heel under seismic action. It show that when the crack closes, the direction of flow velocity points to crack mouth, water is discharging water from crack;when the crack opens, the direction of flow velocity points to crack tip,water is flowing into crack. At the same time, the flow velocity closes to zero when the fracture closure and crack opening achieve maximum. In the same crack, flow velocity of center place of crack slows down from crack mouth (10mm) to crack tip.(3) The time history curve of joint opening is influenced on the crack depth and direction.For the horizontal cracks, the joint opening increases with the early crack depth;For the inclined cracks, the joint opening decreases when the crack angle enlarges. Meanwhile, changing regularity of crack volume and water pressure are discussed when cracks close. Variable quantity of crack volume decreases when the crack angle increases, but the water pressure increases;the water pressure increase with the crack depth and the crack volume change remarkably.(4) For the same crack angle, the longer the depth of the crack,the lower the maximum pressure at the equal distance from crack mouth will be,while the range of the maximum pressure from crack mouth to crack tip rises;For the same crack depth, the larger the angle of the crack,the higher the maximum pressure at the equal distance from crack mouth will be,while the range of the maximum pressure from crack mouth to crack tip also rises. Finally, stress intensity factor is calculated.The results show that, with the growth of crack length, K_I and K_II are growing, K_e growing larger accordingly. This suggests that the longer that crack length, the more unstable crack.Along with the increase of crack angle, K_I is reducing, and K_II increasing continuously, K ealso decreasing unceasingly.