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For tunnel-support engineering, the bed separation of surrounding rock has a great influence on the support performance of bolts. In order to reveal the mechanical properties of the full-grouted prestressed bolt under the influence of bed separation, three typical working conditions of single-separation, multi-separation and different separation positions were set up, and theoretical models and numerical models were established. Furthermore, the characteristics of bolt axial force and anchorage–interface shear stress were analyzed by numerical method, and the sensitivity based on an orthogonal test was studied by means of range analysis and variance analysis. The results showed that: (1) under the single-separation condition, the separation value has a significant effect on the mechanical properties of the bolt, and with the increase in the separation value, the sliding failure unit of the bolt increases; (2) for multi-separation conditions, if the total separation value is the same, the increase in the number of separation interfaces is beneficial to the force of the bolt; (3) for the case where the separation layer is located at different positions, the separation layer on the right side is more likely to cause the overall slip failure of the bolt; and (4) for the above three influencing factors, the separation value has the greatest influence on the mechanical properties of the bolt, and the separation position has the least influence.

In fracture zones, tunneling with a double-shield Tunnel Boring Machine (TBM) presents significant challenges, including deformation overrun of the surrounding rock, TBM jamming, and excavation face collapse. To assure the tunnel construction safety and efficiency, it is necessary and crucial to conduct a stability analysis of the tunnel surrounding rock when a TBM passes through the fracture zones. The tunnels from Jiadingshan Road Station to Anshan Road Station in Qingdao Metro Line 8 are constructed by double-shield TBMs. It inevitably passes through fracture zones with different deterioration levels and dip angles. In this study, based on this construction section, numerical models of fracture zones with different deterioration levels and dip angles were developed to analyze the displacements of tunnel vaults, inverts, and haunches. In addition, the maximum shear stresses of the surrounding rock were analyzed. Finally, the displacement and shear stress variation patterns of the surrounding rock with different deterioration levels and dip angles were obtained. The findings reveal the stability behavior of tunnels under various fracture zones. They can serve as a valuable reference and theoretical foundation for future tunnel construction projects utilizing double-shield TBMs in areas with fracture zones.

The strength reduction finite element method (SRFEM) needs to modify the input shear strength material parameters manually based on various reduction factors, which is trivial. In order to simplify the computation process, the SRFEM can be achieved by using field variables provided by ABAQUS; there-fore, it can be done automatically in software. By deriving the relationship between field variables and reduc-tion factor and getting the corresponding step time t1 when the calculation cannot converge, then it can quan-titatively calculate the stability coefficient of the slope. According to the different decay extent and speed of shear strength parameters c and φ in the process of slope failure, this paper adopted the dual reduction factors finite element method based on field variables for stability analysis of slope, and verified the feasibility of this method in the stability analysis by combining with classic examples, and found that this method not only im-proves computational efficiency but also the calculation accuracy.

Design parameters such as initial bonding section, prestress, and bonding stiffness have a significant impact on the mechanical properties of the full-length bonded prestressed bolt. In order to understand the influence of the above three parameters on the axial force and shear stress of anchor bolts under the condition of rock separation, theoretical and numerical models were established, and the sensitivity of different parameters was analyzed based on the grey correlation method. Results indicate that the bonding stiffness had the greatest impact on the mechanical properties of the bolt and largely determined the peak axial force, peak interfacial shear stress, and number of sliding elements. Moreover, prestress had a significant impact on the peak axial force and the distribution of shear stress in the initial bonding section, while the length of the initial bonding section had a significant impact on the number of sliding elements and the peak axial force after sliding. The grey correlation method results show that the correlation degrees of the initial bonding section, prestress, and bonding stiffness were 0.8932, 0.9023, and 0.9775, respectively.

Improving coal resource mining rates has long been a focus of coal industry research. The gob-side entry retaining by roof cutting (GERRC) is a new coal mining technology that has gained popularity in China due to its high mining rate and safety. Based on the GERRC technology, the precise technical procedure is elaborated, and the fundamental idea of pressure relief is explored through creating a structural mechanics model of the surrounding rock in this paper. The results of mechanical analysis show that the primary mechanism of roof pressure release is to weaken the integrity of the roof, thereby reducing the ultimate bending moment of the rock stratum. In addition, an additional strategy for pressure release is suggested in this research, involving the weakening of the roof rock by the creation of dense pressure-released holes. The results of the engineering field experimentation demonstrate that the dense pressure-released holes can completely replace the conventional blasting technology of the past to achieve the effect of releasing the roof pressure, thus avoiding the use of hazardous and challenging-to-obtain explosives and demonstrating safety, reliability, and feasibility.

Background: The Pediatric Assessment Triangle (PAT) is a rapid evaluation tool that establishes a child’s clinical status and his or her category of illness in order to direct initial management priorities. However, only few studies have examined its accuracy in assessing triage of critically ill patients in the emergency pediatric department (EPD) in China. Objective: To quantitatively validate the accuracy in assessing critically ill medical children and nurses’ acceptance of PAT in the EPD. Methods: This is a prospective observational study performed at The First People’s Hospital of Kunshan from January to May 2019. Ill children arriving to the EPD were assessed by trained nurses with the PAT and Pediatric early warning score (PEWS) at the same time. The five-level triage system used as the gold standard for comparing the accuracy of PAT was tracked following the triage. PEWS was compared with PAT in terms of assessment time and the degree of nurse’ acceptance. Results: A total of 1608 subjects were included in this study, of whom 74 were critically ill. The AUROCC to screen out the critical children evaluated by PAT was 0.963. When the cut-off value of PAT score was 1, its sensitivity, specificity, PPV and NPV were 93.24%, 99.15%, 84.15% and 99.67%, respectively. The maximum value of the YI of PAT scored with 1 was 0.924. For the different categories of diseases, PAT had a better performance in assessing non-respiratory critical diseases (vs. respiratory critical diseases), with values of AUROCC of 0.986 vs 0.930, YI of 0.969 vs 0.858, respectively. For the different age of sick children, PAT had a better performance in assessing critical diseases in children aged 1 to 36 months (vs. 3 to 14 years), with values of AUROCC of 0.978 and 0.899, YI of 0.952 and 0.797, respectively. The assessment time of PAT was 13.81 ± 6.41 s, while PEWS score was 37.24 ± 10.29 s (t = 17.27, p < 0.001). The VAS scores of nurses’ acceptance of PAT and PEWS were 9.27 ± 0.87 and 8.57 ± 1.52, respectively. Conclusions: PAT can be used as a rapid and effective assessment tool in emergency triage in China. When a child’s PAT score is 1 or more, the child’s condition is critical and priority treatment should be arranged.

In view of the shortcomings in the risk assessment of deep-buried tunnels, a dynamic risk assessment method based on a Bayesian network is proposed. According to case statistics, a total of 12 specific risk rating factors are obtained and divided into three types: objective factors, subjective factors, and monitoring factors. The grading criteria of the risk rating factors are determined, and a dynamic risk rating system is established. A Bayesian network based on this system is constructed by expert knowledge and historical data. The nodes in the Bayesian network are in one-to-one correspondence with the three types of influencing factors, and the probability distribution is determined. Posterior probabilistic and sensitivity analyses are carried out, and the results show that the main influencing factors obtained by the two methods are basically the same. The constructed dynamic risk assessment model is most affected by the objective factor rating and monitoring factor rating, followed by the subjective factor rating. The dynamic risk rating is mainly affected by the surrounding rock level among the objective factors, construction management among the subjective factors, and arch crown convergence and side wall displacement among the monitoring factors. The dynamic risk assessment method based on the Bayesian network is applied to the No. 3 inclined shaft of the Humaling tunnel. According to the adjustment of the monitoring data and geological conditions, the dynamic risk rating probability of level I greatly decreased from 81.7% to 33.8%, the probability of level II significantly increased from 12.3% to 34.0%, and the probability of level III increased from 5.95% to 32.2%, which indicates that the risk level has risen sharply. The results show that this method can effectively predict the risk level during tunnel construction.

Given that the forces acting on the inverts of high-speed railway tunnels are complex and their proper accommodation is critical to traffic safety, an in-situ stress test was conducted on the concrete of a reworked invert in the Fuchuan Tunnel on the Lanzhou–Xinjiang High-Speed Railway. In order to study the forces acting on the invert and the associated development of tunnel floor heave, vibrating wire strain gauges were embedded in the reworked invert concrete. The results show that the reworked invert first underwent compression before tensile stress developed in the central region, then stopped increasing and balanced the compressive stress. Based on the in-situ test results, the floor heave of the invert can be divided into slight, moderate, and severe phases. The progression between these phases is associated with the recharging and infiltration of groundwater into the expansive rock beneath the tunnel invert with the release of load, subjecting the concrete above to sharply increased stress. This causes cracking in the invert, leading to increasingly severe floor heave. The results of this study are of significance for the optimization of tunnel design and support systems and can be used to ensure tunnel traffic safety.