Based on the actual project, a three-dimensional simulation model is constructed to study the deformation and stress characteristics of the special-shaped soil-rock foundation pit excavation of the suspended pile. By adopting bar demolition method, a strength redundancy expression method based on the ultimate bearing capacity of the inner support is proposed, and two inner support importance evaluation indexes of the associated bar and the correlation coefficient are proposed. The findings indicate: (1) Deformation of special-shaped soil-rock foundation pit with the suspended pile mainly concentrates in the upper soil layers, the position of the positive angle and the middle of the longest side of the foundation pit., achieving a peak value of 17.02 mm. This deformation is linked to the geometric composition and stiffness distribution of the support system itself. Notably, the upper deformation of the supporting structure at the positive corner of the foundation pit is larger, and the influence range is about 2 times that at the negative corner; (2) The strength redundancy based on ultimate bearing capacity can comprehensively and quantitatively evaluate the redundancy of deep foundation pits, where the associated bar can pinpoint which component would be most affected after damage occurs, while the correlation coefficient can, to some extent, reflect critical components within support structures; (3) The redundancy of the inner support based on the ultimate bearing capacity is related to its own load and the arrangement of adjacent support bars. The minimum is 4.18. The associated bar are mainly concentrated in the adjacent bars. In the design of the correlation coefficient, should be optimized to decrease the correlation coefficient of the bar and improve the overall reliability of the support structure.

In order to study the dynamic changes and amplitude values of groundwater level in karst mountainous areas, taking the karst mountainous city of Guiyang as an example, selecting daily monitoring data and precipitation data from nine groundwater level dynamic observation points from 2022 to 2023, autocorrelation and cross-correlation analysis are used to analyze the response of groundwater level to precipitation and explore the influence of runoff and drainage conditions and terrain slope on the dynamic changes of groundwater level. The results show that: (1) The groundwater level in the study area is buried at a depth of 1.21 ~ 27.68 m, with an annual variation range of 1.54 ~ 11.99 m, and there are significant differences in the spatiotemporal distribution of groundwater level dynamics; (2) The relevant analysis results indicate that there is a significant lag in the response of groundwater level to precipitation signals in the study area, with an average lag time of 0~4 days, and it gradually increases from the supply area to the discharge area; (3) The terrain slope is an important factor affecting the amplitude of groundwater level variation in karst mountainous areas. The terrain slope in the study area is positively correlated with the amplitude and variation of groundwater level, with linear goodness of fit (R²) of 0.65 and 0.78, respectively; (4) The depth of groundwater level gradually decreases from the recharge area to the discharge area, and the range of water level changes from the runoff area to the recharge area to the discharge area.

Understanding the resistance coefficient along the tunnel wall is helpful to optimize the ventilation design of tunnel construction and improve the rationality of ventilation scheme. The influence of the height, shape and spacing of rough elements on the resistance coefficient along the tunnel wall is studied. Through the model test and the numerical model, the difference between the empirical formula and the numerical simulation results was explored. The results show that: With the higher height of the rough element on the tunnel wall, the influence on the resistance coefficient along the tunnel wall is less. The shape of rough elements on the tunnel wall has a great influence on the resistance coefficient along the tunnel, and the semi-spherical rough elements have the smallest resistance coefficient along the way. Comparing the calculated results of empirical formula with the numerical simulation results, the difference between them is relatively stable, which is related to the height of rough elements. The correction coefficient α is proposed for the empirical formula, and the corresponding relationship between α and the average roughness height Δ of the wall is α = 1.29+0.024 8Δ.

At present, the actual pollutant emissions under slag removal stage have not been fully considered in the ventilation of tunnel construction, greatly increasing the required air volume for tunnel construction and causing huge energy waste. On-site testing of CO concentration and wind speed was conducted based on a certain tunnel, the changes in CO concentration over time under different processes were studied, and the effects of engineering vehicle emissions and fan air supply on the distribution of CO concentration and wind speed in the tunnel were analyzed. The results show that: The CO concentration on the palm face remained basically unchanged within 25 minutes after blasting, about 200 mg/m³; During the slag removal stage, the CO concentration on the palm surface decreases linearly and reaches the standard limit (30 mg/m³) after 90 minutes of ventilation; The actual required air volume for tunnel construction during the slag removal stage is much lower than the standard requirements. As the supply air volume increases, the CO concentration in the return air section decreases exponentially. Based on the research results, an empirical calculation formula for CO concentration in highway tunnel construction ventilation is proposed, which takes into account the coupling effects of CO emissions and supply air volume.

The underground caverns has the advantages of safe concealment, environmental protection, and land saving. However, due to its enclosed space, pollutants are easily accumulated during construction. Consequently, improving the operation efficiency of the ventilation system and reducing energy consumption during the construction period are the keys to ensuring the safety of personnel and the normal operation of equipment. Taking an underground cavern project as the object, a theoretical calculation is used to determine the frequency conversion control strategy of the cavern fan, and numerical simulation (Fluent) is used to analyze the concentration changes of benzene and dust pollutants in the underground cavern before and after frequency conversion under the pressure ventilation condition, the field environmental quality monitoring data are compared and validated. The results show that: the concentration of pollutants on the longitudinal section of each cavern before and after continuous ventilation frequency conversion increases gradually and then stabilizes. The gradual conservation of pollutant generation and emission rates, with pollutant concentrations at breathing height below the limit values, verifies the effectiveness of the variable frequency strategy. In the construction site, the ventilation dynamic control system is established to realize the variable air volume control. When the axial flow fan maintains an energy-saving rate of around 25% and the jet fan maintains an energy-saving rate of over 60%, the pollutant concentration in the cavern remains within the limit range. This not only ensures the safety of construction personnel but also reduces energy consumption. The study can provide reference for the ventilation frequency conversion design of multi-face construction in underground caverns.

Subways, as a primary component of urban public transportation, harbor particulate matter within their microenvironments that pose health risks to commuters. To enhance the health of individuals during their subway commutes, a study was conducted to analyze the spatiotemporal heterogeneity of fine particulate matter (PM_2.5) concentrations in the subway microenvironment. The results show that: The PM_2.5 concentration in underground train carriages on weekdays (113.67 μg/m³) is higher than on non-working days (47.62 μg/m³), and the PM_2.5 concentration in underground train carriages is significantly higher than in above-ground and elevated sections (seven times higher) ; lines constructed earlier have higher PM_2.5 concentrations than newly built lines; the PM_2.5 concentration on platforms exhibit a cyclical trend with the arrival and departure of trains; fully enclosed screen doors are more effective than full-height security doors in controlling the accumulation of particles; the PM_2.5 concentration during off-peak hours (75 μg/m³) is lower than during peak hours (102 μg/m³). Furthermore, the study analyzed the potential impact of off-peak travel strategies on the PM_2.5 exposure levels of commuters, the results suggests that off-peak travel could reduce exposure by 25.58% during a single commute. The results of the study provide data support for the prevention.