The composite performance of steel fiber-reinforced concrete (SFRC) is excellent, and its application potential in subsea tunnel engineering has gradually emerged. This paper discusses three types of laboratory testing methods for studying the corrosion of SFRC induced by chlorides: the ion diffusion method, electric field migration method, and pre-corrosion method. The similar relationship between short-term accelerated deterioration tests and the natural corrosion process, as well as the experimental setup for simulating the coupling effect of multiple factors, requires further exploration. Furthermore, the mechanisms of steel fibers influencing the chloride corrosion resistance of SFRC are explored from four aspects: type, coating, shape, and dosage. Finally, by examining practical case studies of SFRC in subsea tunnel applications, the challenges posed by the multi-directionality of chloride ion corrosion, the diversity of corrosion sources, and the uneven distribution of steel fibers are highlighted. Future research should focus on enhancing the application of SFRC in subsea tunnel linings. This study provides a reference and basis for promoting the application of SFRC in subsea tunnel engineering and indicates future development directions.

In this paper, the effects of the cement content and excavation speed parameters on the improvement effect of the artificial freezing method and the characteristics of frozen walls are studied by means of a field test, numerical simulation and theoretical model. The optimization effect of the cement content in the artificial freezing method is studied. It is found that 10% is the best content, which can maximize the freezing wall thickness and grouting effect, and promote uniform distribution of the temperature field. At the same time, the influence of the excavation speed on the stress and settlement of the foundation soil is analyzed. It is pointed out that the increase of the excavation speed will aggravate the settlement and stress redistribution, which may threaten the building structure. The evaluation method proposed in this paper verifies that the construction deformation and settlement control are within the safety standards and provides theoretical support and construction guidance for tunnel engineering.

With the increasing use of horizontal wells in oil and gas development, measurement-while-drilling (MWD) systems require higher magnetic azimuth accuracy to ensure precise trajectory control. This study proposes a three-stage magnetic azimuth error compensation method based on multi-station analysis (MSA). First, the OPTICS clustering algorithm is utilized to identify and remove noise points, and ellipse fitting is applied to suppress radial magnetic interference. Second, an improved MSA model incorporating wellbore trajectory constraints is developed to minimize axial interference and enhance correction stability. Finally, a Gaussian Process Regression (GPR) model, using accelerometer and magnetometer data as features, is introduced to model and compensate for residual nonlinear errors. Experimental validation under simulated complex magnetic conditions shows that OPTICS-based preprocessing significantly improves ellipse fitting and reduces hard magnetic interference. The improved MSA lowers the mean azimuth error to approximately 2.5°, while integrating GPR further decreases it to below 0.04°. The proposed GPR model achieves an R² of 0.99972 and an RMSE of 0.02928° on the test set, confirming its strong nonlinear compensation capability. Overall, the proposed framework effectively suppresses magnetic interference and enhances azimuth accuracy, providing a robust solution for high-precision MWD applications in horizontal wells.

By employing the whale optimization algorithm’s (WOA) capability to reduce the probability of being stuck in a locally optimal solution, this study proposed an improved WOA-DQN algorithm based on the Deep Q-Network algorithm (DQN). Firstly, the mathematical model of Fiber Bragg Grating (FBG) sensor placement was established to calculate the reward of DQN. Secondly, the effectiveness and applicability of WOA-DQN were validated through experiments in nine cases. It indicated that the algorithm is far superior to other methods (Noisy DQN, Prioritized DQN, DQN, WOA), especially with the learning rate of 0.001, the initial noise 0.4, the hidden layer 3–512, and the updated frequency of 20. Finally, the FBG sensors were placed at [0°, 27°, 30°, 47°, 51°, 111°, 126°, 219°, 221°, 289°] to detect the accurate deformation of the tunnel with the maximum error 8.66 mm, which is better than the traditional placement. In conclusion, the algorithm provides a theoretical foundation for sensor placement and improves monitoring accuracy. It further shows great promise for deformation monitoring in tunnels.

Understanding the long-term durability and degradation mechanisms of steel fiber-reinforced concrete (SFRC) linings in subsea tunnels is critical for ensuring structural safety, cost effectiveness, and sustainability. This study investigated the degradation characteristics of SFRC with varying fiber contents (0%, 0.35%, 0.55%, and 0.75%) and different acceleration durations, using the applied electric field acceleration method and X-ray CT tests. The experimental results revealed the characteristics of the surface crack distribution and evolution patterns in the SFRC specimens. Furthermore, the similarity between the non-uniform corrosion patterns observed in regard to accelerated corrosion under the applied electric fields and those occurring due to natural degradation was verified. The pore structure characteristics and internal crack development of the SFRC specimens were compared. The study found that the degradation process of the specimens was closely related to the fiber content. The incorporation of steel fibers altered the crack initiation and propagation modes, leading to a more scattered crack distribution. The accelerated corrosion method, employing an applied electric field, successfully simulated the non-uniform corrosion process of reinforcement in SFRC linings in subsea tunnels under natural conditions. Under the influence of a unidirectional chloride ingress source, the pronounced accumulation of corrosion products was observed only on the side of the reinforcement exposed to chloride penetration. This method effectively visualized the chloride penetration path and its impact on reinforcement corrosion, providing valuable insights for the anti-corrosion design of SFRC linings in subsea tunnels.

Electrical heating ice removal pavement represents a promising technology for pavement ice melting. Existing studies primarily focus on optimizing cable-heated asphalt pavement through indoor model tests or finite element results. To obtain more accurate and reasonable temperature rise processes and heat transfer results, we propose a new evaluation metric for heat transfer capability and optimization in electric heating asphalt pavement. Firstly, a three-dimensional heat transfer model considering environmental heat exchange is established, and the accuracy of the model is verified by outdoor measured data. A dual-variable control experiment was carried out between the cable buried depth and insulation layer configuration to specifically analyze their influence on the temperature field of the asphalt layer. We further investigated heat transfer performance metrics (entransy dissipation and entransy dissipation thermal resistance), with results indicating that shallower cable burial depths reduce environmental interference on pavement heat transfer; the thermal insulation layer most significantly enhances pavement surface temperature (35.66% improvement) when cables are embedded in the lower asphalt layer. Placing cables within corresponding pavement layers according to burial depth reduces heat transfer loss capacity and thermal resistance, and positioning cables in the lower asphalt layer with a thermal insulation layer significantly decreases thermal resistance in both concrete and lower asphalt layers while reducing heat transfer capacity loss, demonstrating that installing thermal insulation layers under this structure improves heat transfer efficiency. The combined experimental and simulation verification method and fire dissipation evaluation system proposed in this study provide a new theoretical tool and design criterion for the optimization of electric heating road systems.