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、拱坝和门控溢洪道在洪水和地震等极端事件中可能会遭受破坏，导致混凝土开裂，这是保持结构稳定性的主要问题。拟议研究计划的目标是(i)开发创新的3D水力学建模方法，以量化考虑裂缝和提升压力的混凝土大坝和溢洪道的安全性（诊断方面），（ii）通过实验确定大质量混凝土的本构参数来模拟接缝/裂缝（验证方面），以及（iii）研究通过灌浆排水修复/加强裂缝大坝的行动的有效性。并添加了钢元素（修复方面）。有效和创新的混凝土水工结构评估/修复策略将大大节省昂贵的修复工作。拟建的研究项目分为两个项目：项目1 -裂缝混凝土重力坝和溢洪道桥墩的三维稳定性评估和纤维元件修复：现有的重力水工结构（大坝、溢洪道、进水口）是复杂的结构，延性有限，对横向地震激励很敏感，在过去常常被忽视。我们将使用(a)材料强度，(b)梁柱理论结合(c)二维截面有限元分析来开发一种新的鲁棒且计算效率高的三维耦合非线性水力学模型，以考虑轴向-弯曲-剪切-扭转相互作用，从而产生适合静力和地震安全评估的“水力学”纤维元件。截面属性将沿单元整合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。失效标准将考虑在水工结构的背景下可以调动的弯曲和剪切强度。裂缝沿升降机接缝（或任意平面）将建模，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观元件（纤维元件）方法，以实现稳健和高效的工业应用。将特别关注以下几个方面，这些方面在过去没有得到广泛的研究，(i)沿着多个平面同时发生三维开裂，（ii）在抬升压力和有限的旧钢筋存在下，开裂部件的稳定性，（iii）施工阶段的考虑（剪切键的存在，修复前的初始应力-应变条件），（iv）应用后张拉，钢或混凝土护套来加固薄弱的桥墩。项目2 -裂缝坝水泥灌浆排水加固：利用灌浆恢复裂缝坝的水密性，降低裂缝坝的上扬压力。然而，注浆后的应力应变状态以及抗拉和抗剪强度的增加是很难量化的。灌浆大体积混凝土裂缝在不同荷载路径下的力学强度研究尚未见报道。灌浆坝的安全评估将通过(a)开发一种新的水力学有限元模型来解决，该模型在坝体中存在排水管的多物理问题中耦合不同的水力和机械网格（灌浆后重新钻孔），以及(b)对灌浆大体积混凝土块进行3D创新实验测试，以验证灌浆裂缝的本构模型。专门的粘（隙）摩擦灌浆有限元将被开发。个案研究将在裂隙拱坝上进行。

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.