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.

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.

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.

To solve the problems of waste accumulation and deep and narrow backfilling of foundation pit in the construction process, by adding polycarboxylate superplasticizer (PCE), cement, phosphogypsum (PG) and water glass (WG), the engineering residue is improved into fluid solidified soil for foundation pit backfill. The effects of various admixtures on the fluidity, strength and drying shrinkage of the improved fluid solidified soil were studied through laboratory mobility test, unconfined compressive strength test, drying shrinkage test and microscopic test, and the improvement mechanism was analyzed. The results show that: The flow property of the material can be greatly improved by adding PCE, but the flow rate decreases rapidly with the increase of cement content. PG can make the sample obtain higher strength in the later stage, while water glass can improve the early performance and drying shrinkage property of the sample. With the incorporation of cement, PG and water glass, various hydration products fill the pores in the soil, and the internal structure of the soil becomes more dense. In addition, the feasibility of using fluid solidified soil as backfill for foundation pit is verified by selecting test section for field backfill. This paper can provide reference for improving the performance of fluid solidified soil and the design of mix ratio.

In order to investigate the impact of pore and fracture structure on the nonlinear deformation characteristics of rocks during the entire stress-strain process, considering the differences in deformation between pores and the matrix, porous rocks are deconstructed into two components: hard springs and soft springs. The Two-part Hooke's Model (TPHM) and statistical damage theory are introduced. Based on the TPHM, the complete stress-strain relationship of rocks is established, and the porosity evolution equation for the entire stress-strain process of rocks is derived. This model overcomes the limitation of the traditional Two-part Hooke's Model, which is unable to represent the plastic deformation of rocks after yielding. It not only accurately characterizes the nonlinear deformation during the pore compaction stage, plastic yielding, stress drop after peak, and residual stress characteristics in the rock compression process, but also effectively represents the porosity variation during the entire stress-strain process of rocks. Extensive experimental data validation has demonstrated that the theoretical curves of this constitutive model align well with the experimental results, with correlation coefficients consistently exceeding 0.9.

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.

Urban underground logistics system is a complex technology and engineering system developed by the cross integration of modern logistics, transportation, vehicle and underground engineering. Based on the concept of the underground logistics system-pipeline-vehicle collaborative design, a set of cargo vehicle design methods for urban underground pipeline logistics is established. Vehicle technology research and design include vehicle scheme research, vehicle structure and new energy function design, vehicle autonomous driving technology design. This paper designs a special cargo vehicle for pipeline logistics, which is a pipe with inner diameter of 3 800 mm and van with exterior dimension length of 5 000 mm, width of 1 500 mm and height of 2 200 mm. The vehicle has automatic driving, high power, long-distance automatic transportation of goods and wireless charging function when the vehicle is driving in the pipeline. The vehicle design adopts the design concept of green, low-carbon, energy saving and integrated application of more new technological innovations. The technical research and design of cargo vehicle conducted in this paper provides a design scheme of cargo vehicle test sample vehicle and a new vehicle design method of underground pipeline logistics for the implementation of commercial urban underground logistics project.

Underground Logistics System (ULS), as a subterranean urban infrastructure with public utility attributes, can effectively meet urban emergency demands through highly resilient freight networks. However, the operational mechanisms and performance assessment methods for ULS in complex emergency logistics scenarios remain underdeveloped. This study examines ULS emergency service capacity, focusing on the impacts of the operational environment, network structure, and scheduling. A model measuring efficiency, effectiveness, and fairness is developed. Simulations based on freight demand and surface road damage, using the Xianlin case in Nanjing, compare ULS and surface truck delivery. Results show that: ULS exhibits significant advantages in emergency freight performance, particularly under conditions of surface traffic congestion and narrow emergency response time windows. Furthermore, increasing node logistics redundancy, optimizing end-point delivery modes, and ensuring local freight fairness are identified as key factors in enhancing ULS emergency service capacity. This research advances ULS planning theory and offers new insights for urban emergency management.

In order to enhance the prediction accuracy of surrounding rock deformation, enable real-time monitoring of deformation status, prevent deformation failure, and ensure construction safety, a novel underground cavern surrounding rock deformation temporal prediction method based on GRU neural network is proposed to tackle the low training efficiency, slow convergence, and poor generalization of traditional methods, along with the establishment of a corresponding prediction framework. Utilizing monitoring data of surrounding rock deformation from the underground powerhouse on the right bank of the Baihetan Dam, predictions are made and subsequently compared and analyzed with the forecasting results generated by the Long Short-Term Memory (LSTM) neural network algorithm. The results indicate that the GRU neural network model effectively addresses the prediction challenges associated with underground cavern surrounding rock deformation, offering advantages such as simplified structure, relatively fewer parameters, rapid training and convergence rates, and high prediction accuracy. Compared to the predictions derived from the LSTM neural network algorithm, the GRU model demonstrates a reduction in training duration by over 70%, with a corresponding decrease in prediction error of more than 50%. The relative error for cumulative maximum deformation is less than 0.3%, the probability of absolute error less than 0.9 mm is as high as 95%, and the maximum absolute error is only 2.05 mm.

To investigate the impact of changes in end-bearing conditions, resulting from shield tunneling, on the bearing capacity of an upper cement-soil pile composite foundation, this study is conducted based on a specific section of the Zhengzhou Metro Line 5 where shield machines cut through cement-soil piles. According to the principle of similarity, a reduced-scale model test of a single cement-soil pile within a composite foundation was designed for laboratory testing. Based on this, a corresponding finite element analysis model was established. By comparing the results from the reduced-scale model test and numerical simulations, the variation patterns of side resistance and end-bearing resistance of the cement-soil pile composite foundation were analyzed as the pile characteristics changed. Studies indicate after the lower part of the cement-soil pile composite foundation undergoes shield tunneling while maintaining a constant vertical load above, there is primarily a redistribution of stress within individual piles, characterized by a transformation between side resistance and end-bearing resistance to balance the upper load. Simultaneously, the neutral point of the side resistance of the cement-soil pile composite foundation moves downward, and its position relative to the pile length is less than that observed in the case where only the pile length is shortened. The change in the length of the cut pile significantly influences the development of side and end-bearing resistances; the contribution of side resistance decreases with an increase in the cut length, whereas the extent to which end-bearing resistance is mobilized slightly increases as the cut length grows.