Wall-mounted swirling ventilation is a new type of system in mechanized excavation faces with a dust sup-pression performance that is closely related to the blowing-to-suction flow ratio.Physical and simulation models...Wall-mounted swirling ventilation is a new type of system in mechanized excavation faces with a dust sup-pression performance that is closely related to the blowing-to-suction flow ratio.Physical and simulation models were developed according to the No.C103 mechanized excavation face in the Nahe Coal Mine of the Baise Mining Bureau,Guangxi Province to optimize the blowing-to-suction flow ratio for wall-mounted swirling ventilation.Both the k-εturbulence model and the discrete phase model were utilized to simulate airflow field structures and dust concentration distribution patterns at various blowing-to-suction flow ratios.The results suggest that higher blowing-to-suction flow ratios increase the airflow field disturbance around the working face and weaken the intensity of the axial air curtain.On the other hand,both the intensity of the radial air curtain and the dust suppression effect are enhanced.At a blowing-to-suction flow ratio of 0.8,the wall-mounted swirling ventilation system achieved the most favorable dust suppression performance.Both the total dust and respirable dust had their lowest concentrations with maximum efficiencies of reducing both types at 90.33%and 87.16%,respectively.展开更多
This paper focuses on theoretical analytical models to calculate the limit support pressure and vertical earth pressure on the cutting face for tunnels.The failure zone is divided into two parts:a sliding failure zone...This paper focuses on theoretical analytical models to calculate the limit support pressure and vertical earth pressure on the cutting face for tunnels.The failure zone is divided into two parts:a sliding failure zone and an upper loosen zone,and the limit support pressure calculation equation is derived.To verify the rationality of the theoretical model,it was compared with the existing theory,numerical simulation,and centrifugal test,and then the parameter analysis was carried out.The results show that the results of this paper agree well with the existing theory,numerical simulation,and centrifugal test.The inclination angle of the proposed mechanism is determined based on the results of the existing centrifuge test,and the recommended inclination angle is between 52°+φ/2 and 54°+φ/2.The method is proven to be safe and accurate.It can provide a theoretical basis for similar projects.展开更多
The applicability of the Decision Aids for Tunneling(DAT)as an early construction cost and time predicting tool for large-scale underground cavern construction projects is investigated in this study.For this purpose,t...The applicability of the Decision Aids for Tunneling(DAT)as an early construction cost and time predicting tool for large-scale underground cavern construction projects is investigated in this study.For this purpose,three large-scale underground cavern construction projects in Singapore are presented using the proposed framework.The data from Project A,which is already completed,are used to validate the prediction outcomes.The results show that the proposed workflow can well estimate the construction cost and time at the 95%confidence level.The DAT simulation results of the other two projects,which are in the early planning stages,are compared with Project A to assess the accuracy of the predicted cost and time.The results show that the proposed workflow with the DAT as a predictor is a valuable tool in estimating construction cost and time for large-scale underground cavern projects,particularly for feasibility studies.展开更多
基金support for this work was provided by the National Natural Science Foundation of China(No.51574123)the Scientific Research Project of Hunan Province Office of Education(No.18A185),which are gratefully acknowledged.
文摘Wall-mounted swirling ventilation is a new type of system in mechanized excavation faces with a dust sup-pression performance that is closely related to the blowing-to-suction flow ratio.Physical and simulation models were developed according to the No.C103 mechanized excavation face in the Nahe Coal Mine of the Baise Mining Bureau,Guangxi Province to optimize the blowing-to-suction flow ratio for wall-mounted swirling ventilation.Both the k-εturbulence model and the discrete phase model were utilized to simulate airflow field structures and dust concentration distribution patterns at various blowing-to-suction flow ratios.The results suggest that higher blowing-to-suction flow ratios increase the airflow field disturbance around the working face and weaken the intensity of the axial air curtain.On the other hand,both the intensity of the radial air curtain and the dust suppression effect are enhanced.At a blowing-to-suction flow ratio of 0.8,the wall-mounted swirling ventilation system achieved the most favorable dust suppression performance.Both the total dust and respirable dust had their lowest concentrations with maximum efficiencies of reducing both types at 90.33%and 87.16%,respectively.
基金The authors gratefully acknowledge the financial support provided by the National Natural Science Foundation of China(Grant Nos.51978019 and 51978018)Natural Science Foundation of Beijing Municipality,China(Grant Nos.8222004 and 8222005).
文摘This paper focuses on theoretical analytical models to calculate the limit support pressure and vertical earth pressure on the cutting face for tunnels.The failure zone is divided into two parts:a sliding failure zone and an upper loosen zone,and the limit support pressure calculation equation is derived.To verify the rationality of the theoretical model,it was compared with the existing theory,numerical simulation,and centrifugal test,and then the parameter analysis was carried out.The results show that the results of this paper agree well with the existing theory,numerical simulation,and centrifugal test.The inclination angle of the proposed mechanism is determined based on the results of the existing centrifuge test,and the recommended inclination angle is between 52°+φ/2 and 54°+φ/2.The method is proven to be safe and accurate.It can provide a theoretical basis for similar projects.
基金The authors would like to acknowledge Professor Herbert H.Einstein(MIT)for his valuable comments and revisions.Additionally,the authors would like to thank the Jurong Town Corporation(JTC)for the funding provided to this project and for generously allowing us to use data from the construction of the rock cavern,without which this work would not have been possible.
文摘The applicability of the Decision Aids for Tunneling(DAT)as an early construction cost and time predicting tool for large-scale underground cavern construction projects is investigated in this study.For this purpose,three large-scale underground cavern construction projects in Singapore are presented using the proposed framework.The data from Project A,which is already completed,are used to validate the prediction outcomes.The results show that the proposed workflow can well estimate the construction cost and time at the 95%confidence level.The DAT simulation results of the other two projects,which are in the early planning stages,are compared with Project A to assess the accuracy of the predicted cost and time.The results show that the proposed workflow with the DAT as a predictor is a valuable tool in estimating construction cost and time for large-scale underground cavern projects,particularly for feasibility studies.
