Development, experimental validation, and applications of 3D hydro-mechanical concrete fracture models for structural safety evaluation and rehabilitation of concrete hydraulic structures subjected to

现有的混凝土重力坝、拱坝和闸门溢洪道在发生洪水和地震等极端事件时预计会受到破坏，导致混凝土开裂，这引发了对维护结构稳定性的主要担忧。拟议研究计划的目标是(I)开发创新的3D流体力学建模方法，以量化考虑裂缝和扬压力的混凝土大坝和溢洪道的安全性(诊断方面)，(Ii)通过实验确定大体积混凝土本构参数以模拟接缝/裂缝(验证方面)，以及(Iii)研究通过灌浆排水和添加钢材来修复/加固裂缝大坝的行动的有效性(恢复方面)。混凝土水工结构的有效和创新的评估/修复战略将大大节省昂贵的补救工作。拟议的研究计划分为两个项目： 项目1-使用纤维构件对裂缝混凝土重力坝和溢洪道桥墩进行三维稳定性评估和修复：现有的重力水工建筑物(大坝、溢洪道、进水口)是延性有限的复杂结构，对横向地震激励很敏感，这在过去往往被忽视。我们将利用(A)材料强度、(B)梁-柱理论与(C)二维截面有限元分析相结合的方法开发一种新的稳健且计算高效的三维非线性流体力学耦合模型，以考虑轴向-弯曲-剪切-扭转相互作用，从而形成适用于静态和地震安全评估的“流体力学”纤维单元。截面属性将沿单元集成以形成质量和刚度矩阵，该矩阵将与其他单元组装以表示完整的结构。将考虑在水工结构范围内可以调动的弯曲强度和剪切强度的失效标准。将模拟沿提升缝(或任意平面)的裂缝，包括裂缝中的水渗透。详细的3D有限元分析将用于验证所建议的宏单元(纤维单元)方法，该方法旨在实现稳健和高效的工业应用。将特别关注过去没有广泛研究的以下方面：(I)沿多个平面同时进行的三维裂缝；(Ii)在扬压力和有限的旧钢筋存在的情况下，开裂构件的稳定性；(Iii)施工阶段的考虑(存在剪切键，修复前的初始应力-应变状态)；(Iv)后张法、钢或混凝土套筒加固薄弱桥墩的应用。 项目2-水泥灌浆和排水加固裂隙坝：灌浆用于恢复裂隙坝的水密性和降低扬压力。然而，注浆后的应力应变状态以及抗拉强度和抗剪强度的增长是很难量化的。关于灌浆大体积混凝土裂缝在代表现场条件的不同加载路径下的机械强度的研究尚未见报道。灌浆坝的安全评估将通过(A)在坝体有排水口(灌浆后重新钻孔)的情况下，在多物理问题中耦合不同的水力和力学网格，开发一种新的考虑排水的流体力学有限元模型，以及(B)对灌浆大体积混凝土砌块进行三维创新试验，以验证灌浆裂缝的本构模型。开发特殊的粘结(GAP)-摩擦灌浆有限元。将对有裂缝的拱坝进行案例研究。

Existing concrete gravity, arch dams, and gated spillways are expected to sustain damage in the event of extreme events such as floods and earthquakes inducing concrete cracking raising major concerns to maintain structural stability. The objectives of the proposed research program are (i) to develop innovative 3D hydro-mechanical modelling methodologies to quantify the safety of concrete dams and spillways considering cracking and uplift pressures (diagnostic aspects), (ii) to determine experimentally mass concrete constitutive parameters to model joints/cracks (validation aspects), and (iii) to study the effectiveness of actions to repair/strengthen cracked dams by grouting drainage, and added steel elements (rehabilitation aspects). Effective and innovative assessment / rehabilitation strategies of concrete hydraulic structures will permit substantial saving on costly remedial work. The proposed research program is divided into two projects: Project 1 –3D Stability Evaluation and Rehabilitation of Cracked Concrete Gravity Dams and Spillway piers using fiber elements: Existing gravity hydraulic structures (dam, spillway, intake) are complex structures with limited ductility that are sensitive to lateral seismic excitations that have often been ignored in the past. We will pursue the development a novel robust and computationally efficient 3D coupled nonlinear hydro-mechanical model using (a) strength of material, (b) beam-column theory combined with (c) 2D sectional finite element analyses to account for axial-flexure-shear-torsion interactions leading to a "hydro-mechanical" fiber element suitable for static and seismic safety assessment. Sectional properties will be integrated along the element to form the mass and the stiffness matrices to be assembled with other elements to represent the complete structure. Failure criteria will be considered for the flexural and shear strengths that could be mobilised within the context of hydraulic structures. Cracking along lift joints (or arbitrary planes) will be modelled including water penetration in cracks. Detailed 3D FE analyses will be used to validate the proposed macro-element (fiber element) approach directed towards robust and efficient industrial applications. A particular attention will be given to the following aspects that have not been extensively studied in the past, (i) simultaneous 3D cracking along multiple planes, (ii) stability of cracked components in the presence of uplift pressures and limited, old steel reinforcement, (iii) consideration of phases of construction (presence of shear key, initial stress-strain condition before repair), (iv) application of post-tensioning, steel or concrete jacketing to reinforce weak piers. Project 2 -Strengthening of Cracked Dam by Cement Grouting and Drainage: Grouting is used to restore water tightness and reduce uplift pressures in cracked dams. However, the post-grouted stress-strain state and the gains in tensile and shear strengths are very difficult to quantify. No work has been reported on mechanical strength of grouted mass concrete cracks subjected to different load paths representative of in situ conditions. The safety assessment of grouted dam will be tackled by (a) development of a novel hydro-mechanical finite element model with drainage in a multi-physic problem coupling different hydraulic and mechanical meshes in the presence of drains in the dam body (re drilled after grouting), and (b) 3D innovative experimental testing of grouted mass concrete blocks to validate constitutive models for grouted cracks. Special adhesive (gap)-friction grout finite element will be developed. Case studies will be performed on cracked arch dams.