Based on the compensation concept, an improved method for twin-tunnel complementary ventilation design considering differences in key pollutants in the uphill and downhill tunnels was proposed. The results demonstrate that the scheme developed using the improved method is more energy efficient when the energy consumption of the interchange channel is included. Here, a larger design of air volume is allocated to the uphill tunnel, and the admissible pollutant concentration for its exits. The complementary ventilation system of the Qingniling Tunnel, Dabieshan Tunnel, and Lianghekou Tunnel was redesigned for long-term performance using the improved method, and the resulting scheme was compared to that designed using the current method in terms of the total required air volume, interchange air volume, ventilation effects, and energy consumption. The results show that these factors in improved method are significantly smaller than that of the current method with an allowable reduction of ventilation effects. Moreover, the total airflow required in the Qingniling Tunnel was reduced from 889.31 to 796.74 m3/s, with a decrease rate of 10.4%; the interchange air volume was reduced from 203 to 175 m3/s, and the estimated energy consumption was decreased from 2760 to 2065.9 kW. This represents a 26% improvement in energy efficiency. The proposed method can provide a reference for the energy efficient design of ventilation systems in extra-long highway tunnels.
Based on the compensation principle and optimization theory, an energy conservation optimization mode for twin-tunnels complementary ventilation design was proposed. And, compensation concept utilization in energy conservation of long tunnels ventilation was discussed. The energy consumption for long tunnels can be reduced significantly by remoulding longitudinal ventilation to complementary ventilation of single U-type mode or normal mode. The short-term and long-term ventilation systems of the Qingniling Tunnel, Dabieshan Tunnel, and Lianghekou Tunnel were redesigned using the optimization method, and the new scheme was compared to the original design in terms of ventilation effects, and energy consumption. In redesign, the energy consumption of short-term ventilation systems decreased 240 kW, 150 kW, and 390 kW, and energy efficiency increased by 40%, 50%, and 68.4%, respectively. In the long term, the numbers of those were 1185 kW, 1185kW, and 540 kW, and 42.5%, 58.09%, and 45%, while the pollutants concentration increased a little. The study can provide a reference for the energy efficient design of ventilation systems in long and extra-long highway tunnels.
With the continuous improvement of the planning system for urban subway construction, shield tunnels are being more frequently constructed, and thus, the floating problem of shield tunnels in construction has been paid increasingly more attention. In view of this, in this paper, with the combination of numerical simulation and theoretical analysis, the problem of floating segments compressing the overburden in the deep shield tunnel is discussed. The influential factors of the pressure arch effect are analysed using numerical simulation, the compressive displacement of soil in the plastic zone is investigated in a focused manner based on the pressure arch effect, and the problem of floating segments that the Mindlin solution is applied to under the actions of distributed force and concentrated force is solved. The results show the following: (1) the displacement of the segment is composed of the shield tail gap, the compressive displacement of the soil, and the translational displacement of the soil; (2) the intensity of the pressure arch effect is interactively influenced by the thickness-diameter ratio and the soil properties; (3) the compressive displacement of the soil mass accounts for a larger proportion of floating segment-induced displacements; and (4) the perturbation influence calculation formula of the surrounding strata and the building structure is obtained based on the Mindlin solution.
Focuses on rockwool as a Class A fire material of exterior wall system. Analyzed by the climatic characteristics of the region north of Jiangxi, and the pros and cons of the various aspect of performance of rockwool insulation materials and the development trend of the regional building energy efficiency and suitable energy-saving technologies, and rockwool exterior insulation technology applications study, discuss and demonstrate the feasibility of the application of this technology in northern Jiangxi building energy efficiency rockwool exterior insulation technology region in the north of Jiangxi has good generalization.
Vertical compressive stress of the foundation is a vital parameter for determining the coefficient of self-weight collapsibility of loess tunnels. This paper aims to provide a theoretical solution for the vertical compressive stress of shallow neighbourhood loess tunnel foundation. Firstly, the formula of boundary depth for deep-and shallow-buried neighbourhood loess tunnels with the consideration of the construction order of two holes is derived. In addition, solutions for surrounding rock pressure of the first and rear holes are established. Then, calculation of foundation vertical compressive stress of shallow neighbourhood loess tunnel is deduced by basing on the Flamant's elasticity solution. Finally, the Xi'an metro line NO. 2 is taken as a case study to examine and verify the applicability of the proposed theoretical method. The case study results show that the variation between the proposed formula and numerical simulation is less than 15%, which proves the reliability of our proposed formula and its potential application in the construction of shallow neighbourhood loess tunnels.
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