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

现有的混凝土重力、拱坝和闸门式溢洪道预计在极端事件（如洪水和地震）中会受到破坏，从而导致混凝土开裂，从而引起对保持结构稳定性的重大关注。拟议研究计划的目标是（i）开发创新的三维水力力学建模方法，以量化考虑开裂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的本构参数，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元件（修复方面）修复/加固开裂大坝的措施的有效性。有效和创新的评估/修复混凝土水工结构的战略将允许大量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-使用纤维单元对开裂的混凝土重力坝和溢洪道桥墩进行三维稳定性评估和修复：现有的重力式水工结构（大坝、溢洪道、进水口）是具有有限延性的复杂结构，对过去经常被忽视的横向地震激励敏感。我们将致力于开发一种新的稳健且计算高效的3D耦合非线性流体力学模型，该模型使用（a）材料强度，（B）梁柱理论结合（c）2D截面有限元分析，以解释轴向-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。截面特性将沿单元沿着集成，以形成质量和刚度矩阵，并与其他单元组合以表示完整的结构。将考虑在水工结构范围内可调动的弯曲和剪切强度的失效标准。将模拟沿提升缝（或任意平面）的沿着裂缝，包括裂缝中的水渗透。详细的三维有限元分析将用于验证所提出的宏单元（纤维单元）方法，该方法旨在实现稳健和高效的工业应用。将特别关注过去未广泛研究的以下方面，（i）沿沿着多个平面的同时3D开裂，（ii）存在扬压力和有限旧钢筋时开裂构件的稳定性，（iii）施工阶段的考虑（存在剪切键，修复前的初始应力应变条件），（iv）应用后张拉、钢或混凝土套壳加固薄弱桥墩。 项目2 -通过水泥灌浆和排水加固开裂大坝：灌浆用于恢复开裂大坝的水密性并降低扬压力。然而，灌浆后的应力-应变状态以及抗拉和抗剪强度的增加很难量化。目前还没有关于灌浆大体积混凝土裂缝在代表现场条件的不同荷载路径下的机械强度的研究报告。灌浆大坝的安全评估将通过以下方式进行：（a）在坝体存在排水沟（灌浆后重新钻孔）的情况下，开发一种新型的水力-力学有限元模型，该模型在多个问题中具有排水能力，并耦合不同的水力和机械网格;（B）灌浆大体积混凝土块的三维创新实验测试，以验证灌浆裂缝的本构模型。将开发特殊的粘结（间隙）-摩擦灌浆有限元。将对开裂拱坝进行案例研究。

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.