High‐pressure hydraulic fracture (HF) is an important part of the safety assessment of high concrete dams. A stress‐seepage‐damage coupling model based on the finite element method is presented and first applied in HF in concrete dams. The coupling model has the following characteristics: (1) the strain softening behavior of fracture process zone in concrete is considered; (2) the mesh‐dependent hardening technique is adopted so that the fracture energy dissipation is not affected by the finite element mesh size; (3) four coupling processes during hydraulic fracture are considered. By the damage model, the crack propagation processes of a 1 : 40 scaled model dam and Koyna dam are simulated. The results are in agreement with experimental and other numerical results, indicating that the damage model can effectively predict the carrying capacity and the crack trajectory of concrete gravity dams. Subsequently, the crack propagation processes of Koyna dam using three notches of different initial lengths are simulated by the damage model and the coupling model. And the influence of HF on the crack propagation path and carrying capacity is studied. The results reveal that HF has a significant influence on the global response of the dam.

Pipe cooling is one of the most important measures of mass concrete temperature control, but pipe cooling has its advantages and disadvantages. Inappropriate pipe-cooling water temperature may result in excessive stress and crack. Considering the fact that concrete is a type of three-phase composite material and the sizes of cooling pipe and aggregate are basically on the same scale, the mesoscopic heterogeneity of concrete may have a great effect on the stress field surrounding the pipe. This article computes the pipe cooling–induced stress and damage and analyzes the differences between the homogeneous model and heterogeneous model based on mesoscopic mechanics. In this study, both linear elastic analysis and nonlinear damage analysis are performed; elastic modulus and creep are used as a function of concrete age; and several factors such as temperature difference, multistep cooling mode, and earlier cooling are also studied. The research results show that due to the mesoscopic heterogeneity characteristics of concrete, there is a great deal of difference between homogeneous model and heterogeneous model; pipe cooling can lead to large residual stress around the aggregate and produce a large range of damage, and previous homogeneous model indeed underestimates the effect of cooling-induced stress; using multistep cooling and early cooling mode can reduce this damage; the cooling-induced damage has significant influence on the anti-crack performance of concrete. In the final, based on the research results, the temperature difference between the concrete and pipe water of the second-phase cooling was recommended to be controlled at approximately 5°C.

Hardening stresses are generated as concrete hardens when the volume shrinkage of the concrete mortar is restrained by the aggregates. In the early stages of concrete curing, random cracking tends to occur because the structural strength of a concrete structure is relatively low and is likely exceeded by the concrete shrinkage-induced hardening stress. This is the primary cause of the initial damage in concrete. To investigate the initial damage in concrete, an exponential model for strain hardening is combined with a spline interpolation method to characterize the anisotropic hardening process in a three-phase structure that consists of aggregates, cement mortar and an interfacial transition zone (ITZ). A nonlinear analysis using a stress/strain softening damage model is then performed to analyze the characteristics of the shrinkage-induced initial damage in the concrete and the influence of the aggregates on the structural damage. To calculate the magnitude of the initial damage in concrete, damaged and undamaged concrete specimens are subjected to uniaxial loads. The results show that the shrinkage-induced damage initiates at the surfaces of aggregate particles and in the ITZs and then propagates into the cement mortar. The initial damage to the concrete is influenced by the volume fraction and geometric characteristics of the aggregate. These characteristics are analyzed using a random aggregate model and compared with computed tomography images of a cross section of concrete.