| China's subway has large energy consumption during the construction and operation period.Therefore,it is the main concern of subway design to make the best use of the natural heat and cold sources in the stratum to reduce the cost of energy consumption in the process of subway operation.The optimal design of HVAC system in subway station is closely related to the inter annual variation of ground temperature field in the stratum where the subway tunnel is located and the thermophysical properties of surrounding rock.Conclusion of determining the variation law of temperature field in subway station can provide reliable basis for the optimization design of HVAC system after subway operation.This paper via testing and studying the thermophysical properties of surrounding rock of Lanzhou Metro obtained it's relevant thermal physical parameters,these parameters are references for calculating the temperature field of surrounding rock of subway tunnel and station;The natural temperature distribution law of subway surrounding rock is mastered by long-term testing on set temperature measuring hole on site;Finally,a finite element calculation model is established to simulated the variation of surrounding rock temperature field affected by influence of subway station environment,and the interaction between surrounding rock temperature and station environment temperature,the design and application of subway ventilation and air conditioning system are also carried out.These conclusions can be a reference for the temperature change and control of Lanzhou Metro Station.After the study,the following conclusions are drawn:(1)According to field monitoring results,In the initial geothermal field,the annual variable temperature layer of the Lanzhou Metro is located at the depth 12m from the surface;The annual constant temperature layer is below 12m depth,the temperature is about 15?.In the initial geothermal field,annual ground temperature variation at every depth in the annual variable temperature layer of Lanzhou Metro is similar to the ambient temperature variation,approximately present sinusoidal distribution,but there is a phenomenon of phase lag.The amplitude of ground temperature decreases exponentially with the raise of buried depth in a year.(2)Via measurement of test sample,the thermal conductivity of undisturbed loess soil in the surrounding rock of Lanzhou subway range from 1.14 to 1.48W/(m·K),the thermal diffusivity is between 0.3 and 0.6 mm~2/s.The thermal conductivity of the undisturbed sand is 1.896 W/(m·K),the thermal diffusivity is 0.85mm~2/s.The specific heat is among 2.0~3.0 MJ/(m~3·k).(3)The test results showed that the thermal conductivity of the surrounding rock of Lanzhou subway increases linearly with the water content,it's linear correlation is good,linear equations can be used to describe the relationship between soil thermal conductivity and water content.The thermal diffusivity of all soil layers raises first and then decreases with the increase of water content.The thermal diffusivity of soil reaches the maximum within the range from 7%to 10%.The volume specific heat of each soil layer raises with depth,and its value oscillates from 2.0 to 3.0 MJ/(m~3·k).(4)Based on the calculation results,the ambient temperature is higher than the surrounding rock temperature in subway tunnel,during the operation period of the train,the train will heat release to the tunnel lining and surrounding rock of the tunnel,but its influence on surrounding rock temperature is limited.When the ambient temperature of tunnel wall surface at 30?,the surrounding rock temperature pattern is about 10.0m,the temperature rises of 4.0 to 12.0?.(5)Based on the calculation results,the ambient temperature is higher than the surrounding rock temperature in subway station,during the operation period of the station,the station will heat release to the surrounding rock,but its influence on surrounding rock temperature is limited.When the ambient temperature of subway station at 30?,the surrounding rock temperature pattern is about 12m~15m,the temperature rises of 5.0 to 13.0?.(6)Based on the calculation results,in the operation period of the subway station,environmental heat absorbed by wall surfaces and surrounding rocks lead to reduce station ambient temperature,as a result,station space environment refrigeration cost would be saved effectively.When the ambient temperature is 25?at the station,in the range of 10m to 15m near the wall surface,the ambient temperature can be reduced about 4~6?.The temperature near the subway station wall surface is about19~25?,the surrounding rock has a partly cooling effect on the wall surface.(7)According to the relevant information of Lanzhou Metro,testing thermal physical parameters and numerical results using experiments,the design and application of subway ventilation and air conditioning system are also carried out. |
PDF Full Text Request