With the continuous development in drilling and blasting technology, smooth wall blasting (SWB) has been widely applied in tunnel construction to ensure the smoothness of tunnel profile, diminish overbreak and underbreak, and preserve the tunnel’s interior design shape. However, the complexity of the actual engineering environment and the deficiency of current optimization theories have posed certain challenges to the optimization of SWB parameters under arbitrary geological conditions, on the premise that certain control targets are satisfied. Against the above issue, a genetic algorithm (GA) and back propagation (BP) neural network-based computational model for SWB design parameter optimization is proposed. This computational model can comprehensively reflect the relation among geological conditions, design parameters, and results by training and testing the 285 collected sets of test data samples at different conditions. Moreover, it automatically searches optimal blasting design parameters through the control of SWB targets to acquire the optimal design parameters based on specific geological conditions of surrounding rocks and under the specified control targets. When the optimization algorithm is compared with other current optimization algorithms, it is shown that this algorithm has certain computational superiority over the existing models. When the optimized results are applied in practical engineering, it is shown that in overall consideration of the geological conditions, control targets, and other influencing factors, the proposed GA_BP-based model for SWB parameter optimization has high feasibility and reliability, and that its usage can be generalized to analogous tunneling works.

The concrete-filled double steel tube (CFDST) has been more and more widely used in infrastructure due to its greater moment of inertia compared to the ordinary concrete-filled steel tube (CFST). With the increase in collision accidents occurring in recent years, the research on CFDST under impact needs more attention. To study the dynamic responses of CFDST columns under lateral impact, the finite element package ABAQUS was used to simulate the impact force and mid-span deflection of the column under the coupling action of axial force and lateral impact based on the comparison of experimental data in the literature. The influence of hollow ratio, axial compression ratio, slenderness ratio, impact energy, and material strength on the dynamic responses of the CFDST column are studied. The results show that with the increase in the hollow ratio from 0.3 to 0.8, the residual mid-span deflection of the CFDST column decreases by 77.9%. The mid-span deflection shows an increasing trend following a decreasing one with the axial compression ratio increasing. With the increase in the slenderness ratio from 30 to 60, the plateau impact force decreases by 62.5%, and the residual mid-span deflection increases by 240.5%. The practical formulas for the impact-bearing capacity and residual mid-span deflection of the CFDST column are suggested with high accuracy.

With the improvement of informatization and standardization of mine development, it is an inevitable trend to apply computer technology to the intelligent design of tunnel blasting excavation. Seeking to the problems existing in the intelligent design system of blasting excavation, a new intelligent design system of blasting excavation is constructed from the perspective of database technology. The new intelligent design system adopts the design of central database system and subuser rights to meet the data synchronization and sharing among different users. At the same time, the new system also extracts blasting design parameters and actual engineering data and designs a more reasonable and comprehensive database structure, database logic, and data word table. Based on the T-S fuzzy neural network model, the intelligent search rules of excavation blasting data are also constructed in the new system. Finally, based on Oracle and VB.NET as the new system development platform, MFC, and ADO as the new system development technology, the new intelligent design system for tunnel blasting and excavation was completed. The implementation of the new system addresses the needs of blasting data information storage and search and lays a foundation for the informatization and standardization of tunnel excavation blasting.

With the progress of deep mining in mine exploitation, the effect of the in situ stress field plays a more and more significant and crucial role in rock blasting. To uncover the impact of in situ stress field on empty‐hole effect during parallel‐hole cutting, the distribution and the trend of changes in dynamic stress around empty hole during blasting under different in situ stress conditions are simulated based on the basic model for parallel‐hole cutting using 3D finite element analysis software ANSYS/LS‐DYNA and implicit‐explicit analysis method. Subsequently, the law of variation in the empty‐hole effect under different in situ stress conditions is determined, and the effects of horizontal and vertical stress fields are analyzed in detail. The simulation results show that the overall increase in in situ stress can facilitate compressive failure and inhibit tensile failure in the rock mass around an empty hole during blasting. When empty holes are arranged horizontally, the effect of the vertical stress field is consistent with that of the in situ stress field, while the effect of the horizontal stress field is opposite to that of the in situ stress field. With the increased stress, the inhibitive effect of the vertical stress field on tensile stress around an empty hole is remarkably stronger than that of the horizontal stress field. Finally, the numerically simulated results are verified by the theoretical calculation. This study can provide new insight and a simple but accurate numerical simulation method to investigate how the in situ stress field affects the empty‐hole effect, especially in deep mining.

High-strength concrete (HSC) is widely used in coastal regions, but its durability and structural safety is threatened by chloride ingress in marine environments. This study investigates the effects of different curing methods, normal, steam, and high-temperature autoclave on the chloride resistance of HSC using the electric flux test. A critical chloride concentration of 4.5% was identified, and accelerated deterioration tests were conducted to evaluate mechanical properties development (compressive strength, elastic modulus, toughness, specific toughness) under the various curing conditions. Additionally, the development of hydration products and microstructural characteristics were analyzed to elucidate the mechanisms underlying the observed differences. The results indicate that steam and autoclave curing enhance cement hydration and the initial mechanical properties of HSC but also increase permeability and susceptibility to chloride ion penetration compared to normal curing. Chloride penetration was found to be most severe at moderate chloride concentrations (~4.5%), while higher concentrations resulted in reduced ion migration. Although intensive curing under elevated temperature and pressure improves early strength and stiffness, it accelerates mechanical degradation under chloride exposure, highlighting a trade-off between short-term performance and long-term durability.

During the period of service, the infrastructure is subjected to various forms of impact. To investigate the impact responses of a reinforced concrete (RC) beam, a numerical model of the RC beam under impact was developed by the finite element package LS-DYNA in this study. The numerical model was verified by using the drop hammer test on the RC beam. Using the numerical model, the midspan displacement of the RC beam is analyzed under the interaction of impact mass and impact velocity. The results show that the response surface of midspan displacement can be fitted as a binary power function of impact mass and impact velocity. The midspan displacement under various impact conditions with equal impulse or equal impact energy is different. Within the scope of a low-speed impact, the midspan displacement decreases with an increase in the impact mass under the equal impulse, while it increases with an increase in the impact mass under the equal impact energy. In addition, the impact failure of the RC beam is judged by the deformation criterion. The threshold value of the ductility coefficient is recommended to be set as 15 in the impact-resistant design for RC beams in civil engineering structures within the scope of a low-speed impact.