Due to the strong disintegration and water erosion of completely weathered granite, water and mud inrush disasters are apt to take place in this zone during underwater tunnel construction. The pore, compactness, seepage path length, fracture geometries and their interconnections for water and mud transfer are strongly influenced by confining pressure and waterproof-resistant slab safety thickness. In order to inspect the influence, a series of experiments based on a self-designed testing system and non-Darcy testing method were performed. The results indicated that the water and mud inrush evolution increased with the increase of confining pressure and decreased with the increase of safety thickness. In particular, the confining pressure mainly influences the initial evolution stage, and a critical safety thickness to prevent water and mud inrush is obtained. Besides, the non-Darcy testing method results shows that the water and mud inrush evolution affects the influence of non-Darcy flow. For example, while the safety thickness was smaller than the critical value, the evolution was large and unstable and its behavior transferred into nonlinear. In this case, the flow changed to non-Darcy flow.

This study aims to minimize the carbon emissions of cement and investigate the viability of employing activated coal gangue (CG) as an additional cementitious ingredient. This paper investigated the effects of water-cement ratio, ages, and amount of activated CG dosing on the compressive and flexural strength of cement mortar as well as the effects of activated CG on hydration products, hydration process, and hydration degree. The impacts of activated CG on the hydration products and microstructure of cement were examined using XRD, SEM, and TG/DTG systems. A large amount of active SiO₂ and Al₂O₃ in the activated CG react with Ca(OH)₂ leading to a secondary hydration reaction in cement. The hydrated calcium silicate and hydrated calcium aluminate gels produced by the subsequent hydration process can reduce the porosity of hardened cement and boost cement mortar strength. The 28 days flexural and compressive strengths of specimens with 30wt.% activated CG rise by 11.69% and 11.82%, respectively, in comparison to that of specimens with 30wt.% quartz powder. When activated CG is mixed with cement, the early hydration rate of the cement can be decreased while the later hydration rate is increased.

Failure is a major element that causes deterioration, which in turn affects the serviceability of long span bridges. Currently, the Bayesian network, which relates to probability statistics, is widely used for evaluating fatigue failure reliability. In particular, Bayesian network can not only calculate the fatigue failure at the system level, but also deduce the fatigue failure at the weld level. In this study, a system-level fatigue reliability evaluation model of a bridge deck (BD), which is seen as a parallel system, is proposed based on the Bayesian network. A fatigue probability reliability model of the BD was derived using the master S-N curve. In addition, the Monte Carlo (MC) method was applied to solve the multi-dimensional and complex analytical expressions in the Bayesian network. The applicability of the proposed model was demonstrated by three numerical case studies.

The weatherability of insulation materials directly affects its thermal insulation performance, so it is necessary to carry out the weatherability experiments for insulation materials. In this paper, three kinds of insulation materials, that is, polyurethane (PUR), foam concrete (FC) and vacuum insulation panel (VIP) are chosen to analyze their thermal conductivity under different kinds of weatherability experiments. For the different kinds of weatherability experiments, the experiments of damp-heat, freeze-thaw, high-low temperature and wet-dry are designed to analyze the thermal conductivity of the insulation materials and the microstructure of insulation materials. The experimental results show that thermal conductivity of FC has a downward trend under the damp-heat experiment, and the thermal conductivity of FC has increased in other experiments. The thermal conductivity of PUR increases in all weatherability experiments, but the thermal conductivity of VIP does not change in all weatherability experiments.

Wind field (e.g., wind speed and wind direction) has the characteristics of randomness, nonlinearity, and uncertainty, which can be critical and even destructive on a long-span bridge’s hangers, such as vortex shedding, galloping, and flutter. Nowadays, the finite element method is widely used for model calculation, such as in long-span bridges and high-rise buildings. In this study, the investigated bridge hanger model was established by COMSOL Multiphysics software, which can calculate fluid dynamics (CFD), solid mechanics, and fluid–solid coupling. Regarding the wind field of bridge hangers, the influence of CFD models, wind speed, and wind direction are investigated. Specifically, the bridge hanger structure has symmetrical characteristics, which can greatly reduce the calculation efficiency. Furthermore, the von Mises stress of bridge hangers is calculated based on fluid–solid coupling.

The influences of CaF2 and TiO2 as a mineraliser on the sintering temperature, phase formation, setting times, and the mechanical and hydration properties of calcium sulfoaluminate (C4A3S) were investigated. The results showed that the addition of CaF2 and TiO2 by 0.5 and 0.2 wt.% can reduce the sintering temperature of C4A3S from 1300 to 1100°C. The addition of appropriate amounts of CaF2 and TiO2 promoted hydration and significantly improved the compressive strength of C4A3S cement (CSC). The compressive strength and hydration speed of CSC containing 0.5 wt.% CaF2 increased with an increase in the TiO2 contents from 0 to 0.2 wt.% at all curing ages. However, when the TiO2 content was increased to 0.25 wt.%, a significant reduction in the compressive strength of CSC was observed. The initial and final setting times of CSC containing 0.5 wt.% CaF2 both decreased with increasing TiO2 content. Compared with the control paste, the 15-h and 28-d compressive strength of CSC containing 0.5 wt.% CaF2 and 0.2 wt.% TiO2 increased from 30.4 and 79.2 MPa to 46.2 and 88.3 MPa, respectively. The hydration speed of CSC containing 0.5 wt.% CaF2 and 0.2 wt.% TiO2 was almost three times that of CSC without CaF2 and TiO2. Therefore, the optimum amounts of CaF2 and TiO2 that should be added to C4A3S as a mineraliser are 0.5 and 0.2 wt.%, respectively.