To reduce risk incidents in large bridge construction, it is necessary to study the interaction mechanisms and dynamic changes among various risk factors during the construction of large bridges. First, the evolution mechanism of construction risks for large bridges is analyzed, and a risk factor structure system is established. Then, based on system dynamics theory, a causal loop diagram and flow–stock diagram are constructed, and system dynamics equations for each variable in the flow diagram are established to build a system dynamics model. Finally, taking a large bridge construction project as an example, the variable equations are assigned actual values, and the construction risk level is simulated and analyzed. The results show that, ➀ continuous investment in safety funds can effectively reduce the overall risk level of the system, ➁ changes in the management risk subsystem have a significant impact on the overall risk level of large bridge construction, and ➂ increasing the safety investment ratio in both the personnel risk subsystem and the management risk subsystem can effectively reduce the total risk level of the system.

Basement anti-flotation design is crucial in modern urban construction. An increase in groundwater buoyancy can cause basement structures to uplift, leading to structural instability or even damage. To ensure the stability and safety of underground structures under various hydrogeological conditions, anti-flotation design must comprehensively consider factors such as construction, design, supervision, structure, and hydrology. During construction, improper dewatering measures or unreasonable construction progress may lead to an abnormal rise in groundwater levels, increasing the risk of anti-flotation. Design considerations must include sufficient safety margins, supervision must fully recognize the impact of groundwater, and the structural dead load must be adequate. Anti-flotation stability verification includes both overall and local anti-flotation, involving the calculation of groundwater buoyancy, structural self-weight, and overburden, and selecting appropriate anti-flotation stability safety factors. The assessment and selection of the anti-flotation design water level are also critical. Common anti-flotation measures include adding counterweights, tension-resistant piles, compression and tension-resistant piles, and hydro-pressure reduction methods, while reinforcement and repair methods include epoxy resin grouting and steel plating reinforcement. Through systematic analysis and comprehensive research, scientific basis and technical support are provided for anti-flotation design, enhancing design efficiency and reliability and ensuring the safety and stability of underground spaces. Future research will develop more accurate calculation methods, improve design standards, and explore new anti-flotation technologies and materials.

The research on and application of electric fields to promote the rapid infiltration of ions into cement concrete have been widely explored. Still, there are few studies on the migration of sulfate ions using electric fields. In this paper, a new test method is designed using the principle of electric fields, that is, to accelerate the attack of sulfate into concrete under the action of the electric field, to test the resistance of concrete to sulfate attack. By testing different water–cement ratios, different pulse frequencies, different ages, and different soaking environments, the influence of the electric field on the sulfate resistance of concrete was analyzed. The results show that the compressive strength of concrete in a sulfate attack environment is smaller than that of conventional attack and water immersion environment when the water–cement ratio is 0.3, 0.4, and 0.5 under the action of the electric field and increases with the increase of water in the water–cement ratio. Compared with a 14 day test, the compressive strength of concrete in a sulfate attack environment decreased by 1.9%, 8.6%, and 2.9%, respectively, at 28 days, which was faster than that of conventional attack and water immersion. The compressive strength of the concrete in the sulfate attack environment during the full immersion test and the semi-immersion test is smaller than that of the conventional attack and water immersion, and the semi-immersion test method is more obvious than the full immersion test method. The microscopic morphology of the test group, the water group, and the solution group were compared. From the microscopic morphology comparison, it can be seen that the electric field accelerates the diffusion of sulfate ions into the cement concrete and accelerates the reaction of sulfate ions with the relevant components in the cement concrete. Given the demand for concrete to resist sulfate attack under the action of the electric field, developing new and efficient protective materials is an important research direction. At present, the market lacks protective materials specifically for such an attack environment. This paper provides the theoretical basis and technical support for improving the effectiveness of concrete surface protection technology and engineering practices.

This paper discusses the potential of adding a self-made super-early-strength agent to produce quick-setting, quick-hardening, and high-strength concrete. A super-early-strength agent is prepared by mixing triethanolamine (TEA), aluminum sulfate (Al₂(SO₄)₃·18H₂O), formic acid (HCOOH), and sodium fluoride (NaF) with a water-reducing agent in different proportions. In this paper, the effects of super-early-strength agent ratio and dosage, water–binder ratio, silica fume content, and cementitious material content on the setting time and compressive strength of high-strength concrete were studied. The hydration characteristics were evaluated by X-ray diffraction (XRD) and TG-DSC thermal analysis. The results show that the high-strength concrete prepared by 42.5R ordinary Portland cement mixed with appropriate amount of silica fume and self-made super-early-strength agent has a compressive strength of 10 MPa in 6 h, a compressive strength of 40 MPa in 1 day, a compressive strength of not less than 80 MPa in 28 days, and a compressive strength of not shrinking in 180 days. Using conventional raw materials and general process methods, the concrete prepared according to the preparation method of this experiment can significantly shorten the setting time and improve the compressive strength. However, it is difficult to form concrete when the amount of super-early-strength agent is too large. Nevertheless, this study provides a theoretical basis for large-scale and high-value utilization of the potential of super-early-strength agents and development to improve efficiency. At the same time, it provides a reference for the application of coating technology in rapid repair engineering.