In tunnel approach zones (TAZs), drivers must complete a sequence of tasks, including detecting the tunnel, identifying speed limits, and decelerating to enter safely. However, current standards mandate only stopping sight distance (SSD) compliance of TAZs, which may not suffice for all of these complex driving tasks. In this study, we investigated (1) whether SSDs are sufficient for driving tasks in TAZs, (2) the impacts of restricted visibility conditions on cognitive-behavioral processes, and (3) the appropriate visibility condition of TAZs. We selected tunnels with three visibility conditions to conduct both subjective tests of perception and experiments with real vehicles. We propose a research framework called the task analysis of driving scenarios modified predictive processing model (TADS-MPPM). We then construct a multidimensional framework that includes sequences of behaviors and cognitive tasks (with 4 driving behavior nodes and 4 cognitive nodes) for spatiotemporal profiling, as well as active deceleration coefficients (safety and efficacy coefficients) and cognitive-behavioral workload (measured using the extended Jaccard coefficient). Then, we use an MPPM to visualize the evolution of driving predictions, driving behaviors, and sensory inputs during the approach to the tunnel. Finally, we explore the risk mechanisms of TAZs. The results show that SSD designs (1) delay tunnel detection, speed-limit recognition, and deceleration initiation, as well as compressing behavioral-cognitive chains, and (2) degrade safety and compliance due to overloaded operations and cognition. Conversely, ensuring that critical tunnel information is discernible at a longer decision sight distance provides the necessary margin of safety on the road. This creates adequate space and time to perform progressive deceleration to eliminate task compression and restore composed and smooth driving maneuvers.

The development of large cross-section tunnels is an inevitable trend driven by the intensification of coal mining activities and advancements in mining equipment technology. However, the disturbance stress exerted by adjacent caverns has a more pronounced impact on weakly cemented rock strata in the vicinity of neighboring tunnels. To mitigate deformation in weakly cemented tunnels, grouting and the installation of long anchor cables were employed to reinforce the self-supporting capacity of the surrounding rock, thereby establishing an active support layer. Additionally, U-shaped steel frames combined with the subsequent application of flexible filling materials were utilized to aid the surrounding rock in mobilizing its self-supporting capacity, which resulted in the formation of a passive support layer. A layered collaborative control methodology integrating both active and passive support mechanisms was developed and implemented in engineering practice. The findings demonstrate that the vertical stress was alleviated after cavern excavation and was predominantly transferred toward the adjacent tunnel, with the influence zone extending approximately 7 to 12 times the tunnel height. Conversely, the horizontal stress is primarily dispersed laterally, affecting a region approximately 3 to 6 times the tunnel width. Following the infilling of pebbles between the U-shaped steel frame and the adjacent rock mass, the maximum compressive stress experienced by the U-shaped steel frame decreased by 50%. Additionally, the spatial extent of the maximum axial force was reduced by 65%, whereas the stresses within the rock bolts and cable bolts increased by 30% and 40%, respectively. Grouting reinforcement contributed to bonding and compaction effects on the delamination and fracturing of the roof strata, with the grout predominantly distributed within a range of 1.5 to 5 m from the central region of the roof. The research outcomes presented in this paper can provide valuable reference for a large-section weakly cemented tunnel.

This study investigated the long-term settlement behaviour of piled buildings induced by shield tunnelling in soft ground conditions within urban environments. By integrating a detailed case study with advanced numerical modelling techniques, this study provided a nuanced understanding of the interactions between tunnel construction and existing pile foundations. Central to the investigation is the role of soil consolidation, which significantly contributes to the settlement of piled buildings. To address this, this study emphasizes the critical need for the precise calibration of tunnelling parameters such as face pressure and grouting pressures. These parameters are meticulously controlled to mitigate the adverse effects on nearby piled buildings, ensuring their stability and integrity. It is established that an optimal face pressure, set at 90% of the lateral earth pressure, consistently minimizes the settlement of piled buildings, primarily due to the minimal reduction in the pile toe resistance observed near the tunnel. Similarly, the ideal grouting pressure was identified to be within the range of 120%-160% of the vertical earth pressure, with the smallest building settlement and decrease in pile toe resistance observed at a grouting pressure of 150% of the overburden pressure. This finding elucidates the load transfer mechanism within piled buildings. This study further demonstrated that the settlement induced by the second tunnel excavation is smaller than that caused by the first tunnel excavation owing to the sheltering effects of the adjacent first tunnel and pile foundations. During the consolidation phase following tunnel excavation, the settlement caused by the second tunnel is smaller than that caused by the first tunnel, which is attributed to the dissipation of the negative excess pore pressure around the first tunnel, leading to soil volume expansion. These insights not only validate the effectiveness of the numerical model but also contribute significantly to the field of geotechnical engineering by providing actionable guidelines for future tunnelling projects.

Despite the thriving development of metro-led urban underground public space (UUPS) and its significant benefits and costs, there remains a critical research gap in understanding and evaluating its efficiency. This paper intends to improve the post-evaluation system of metro-led UUPS by proposing an efficiency evaluation framework based on data envelopment analysis. The public and the private sectors are taken as different coexisting decision-makers, and a pair of linear programming is built accordingly (with different assignments of discretionary and non-discretionary inputs) for each decision-making unit. The directional vector is calculated based on CRITIC weights to model the searching process of referential cases in terms of urban renewal. The empirical study of twenty metro-led UUPSs in central Shanghai reveals that (1) the proposed evaluation framework is feasible and discriminative, (2) the efficient form of metro-led UUPS in Shanghai is mainly limited to a compact pattern with a low proportion of pure public space, (3) the essential solution to promote efficiencies is closer cooperation between different parties, and (4) efficiency evaluation is crucial to avoiding the "the-more-the-better" type of development. The findings of this study are expected to shed light on the future planning and operation of metro-led UUPS.