某混凝土重力坝加高后新老混凝土结合面处受力特征分析

重力坝加高对老坝的再利用具有很重要的意义,但在加高的工程中会遇到新老混凝土受力不均匀等问题,采用有限元软件ABAQUS,研究了在考虑混凝土老化的前提下大坝加高的可行性,计算了加高后大坝各坝段的应力分布,并分析了老坝表层材料的弹性模量、强度参数及新老混凝土结合面处的摩擦系数对新老材料结合处拉应力和剪应力的影响。计算结果表明,新老结合面间最大拉应力出现在大坝折坡坡顶向下4/5处,最大剪应力出现在坝坡底。最大拉应力对弹性模量的敏感性更高,但幅度很小,弹性模量从90%折减到60%时最大拉应力降低了0.7%,说明在大坝加高工程中,坝面老化对新老界面产生的拉应力影响较小。而剪应力对强度参数的敏感性更高,强度参数从90%折减到70%时最大剪应力升高了1.2%。增大新老混凝土结合面处的摩擦系数可导致结合面处的拉应力降低,这有利于结合面处的稳定性。

Study of Old and New Concrete Surface Force Characteristics after Heightening A Certain Concrete Gravity Dam

Heightening a gravity dam is important to the reuse of old dam. The problem of non-uniform between the new and old concrete appears in the heightening project. By using finite element software ABAQUS, this paper studies the feasibility of heightening the dam on the premise of considering concrete aging. The stress distribution of the dam section after heightening is calculated. The effects of tensile stress and shear stress between new and old contact surface are analyzed by reducing the elastic modulus and the strength parameters of the old dam surface material and considering the roughness of contact surface. The results show that the maximum tensile stress between the new and old contact surface appears 4/5 downward the dam slopes and the maximum shear stress appears at the bottom of the slope. Maximum tensile stress is more sensitive than maximum shear stress of the elastic modulus, but the amplitude is small. Maximum tensile stress is reduced by 0.7% when the elastic modulus is reduced from 90% to 60%. It demonstrates that the influence of aging of the dam surface on the tensile stress between the new and old contact surface is small in the project of heightening the dam. Maximum shear stress is more sensitive than the maximum tensile stress of the strength parameters. Maximum shear stress increases by 1.2% when the strength parameters are reduced from 90% to 70%. The tensile stress will be reduced by increasing the roughness between the new and old joint surface, which is conducive to the stability of the contact surface.