Sulfate attack is one of the crucial causes for the structural performance degradation of reinforced concrete infrastructures. Herein, a comprehensive multiphase mesoscopic numerical model is proposed to systematically study the chemical reaction-diffusion-mechanical mechanism of concrete under sulfate attack. Unlike existing models, the leaching of solid-phase calcium and the dissolution of solid-phase aluminate are modeled simultaneously in the developed model by introducing dissolution equilibrium equations. Additionally, a calibrated time-dependent model of sulfate concentration is suggested as the boundary condition. The reliability of the proposed model is verified by the third-party experiments from multiple perspectives. Further investigations reveal that the sulfate attack ability is underestimated if the solid-phase calcium leaching is ignored, and the concrete expansion rate is overestimated if the dissolution of solid-phase aluminate is not modeled in the simulation. More importantly, the sulfate attack ability and the concrete expansion rate is overestimated if the time-dependent boundary of sulfate concentration is not taken into consideration. Besides, the sulfate ion diffusion trajectories validate the promoting effect of interface transition zone on the sulfate ion diffusion. The research of this paper provides a theoretical support for the durability design of concrete under sulfate attack.

This work presents a comprehensive coupled thermal-hydro-mechanical model to explore the frost heave mechanism of the concrete-lined canal under a freeze–thaw environment. Unlike previous models that regard concrete as a homogeneous material, this model considers concrete a porous medium and considers the effect of the concrete pore structure, as well as the water content, ice content, and ice-water phase transition, on the mechanical deformation of the canal. Firstly, based on the theories of unsaturated soil mechanics, thermodynamics, and poroelasticity, the thermal-hydro-mechanical coupling equations of the soil under the freeze–thaw condition are established. Then, based on the theories of thermodynamics, poroelasticity, and permeability mechanics of porous media, the thermal-hydro-mechanical coupling equations of the concrete under the freeze–thaw condition are established. Finally, the freeze–thaw simulation of a canal is carried out and compared with the referred indoor model test, in which the evolution behavior of temperature, frost depth, and frost heave deformation of the canal are studied. The results show that the freezing process of the soil foundation is a unidirectional process that develops from the surface to the bottom, and the thawing process of the soil foundation is a bidirectional process that thaws from the surface and bottom to the center. The frost heave deformation of the soil foundation at the 1/2~1/3 slope height area is the largest, which may easily lead to frost heave damage to the concrete lining in this area. The frost heave deformation of the canal obtained by the numerical simulation is consistent with the experimental results, which illustrates the validity of the established model for predicting the frost heave deformation of concrete-lined canals.

This study investigates the probabilistic stability of embankment slopes subjected to water level drawdown using the random field finite element method (RFEM) with strength reduction technology. The shear strength of soil properties was controlled by cohesion and internal friction angle for the slope shear failure. The cohesion and internal friction angle were modeled by a random field following the log-normal distribution. The factor of safety (FOS) for the embankment slope with random soil is calculated by strength reduction technology. During the numerical simulation, the limit analysis upper bound and lower bound method are applied to the finite element method, respectively, to obtain the upper bound and lower bound value of the FOS. Seepage action is also considered during the water drawdown by setting five different water levels (WLs). A total of 1000 Monte Carlo simulations are performed for each work condition, resulting in histograms of the FOSs. The results show that the FOSs obtained by the random field model are all lower than those by the deterministic method. Even if the FOSs obtained by the two methods are close, there still exists the possibility of slope failure. Compared to the deterministic results, the RFEM method is more reasonable for evaluating slope stability.