In order to study the cooling mechanism of embankment with block stone interlayer under open and closed conditions,an experimental railway section was built and data within one freeze-thaw cycle were collected. The re...In order to study the cooling mechanism of embankment with block stone interlayer under open and closed conditions,an experimental railway section was built and data within one freeze-thaw cycle were collected. The results explain well the cooling mechanism of embankment with block stone interlayer. Under the open condition in cold seasons,the enforced convection effect occurs within block stone interlayer when the wind speed is large;however,the weak air convection occurs within the block stone interlayer near the bottom of the embankment when the wind speed is slow. Under the open condition in warm seasons,heat conduc-tion occurs within block stone interlayer due to the change in wind speed and di-rection. Under the closed condition,however,the enforced convection within block stone interlayer is so weak that heat conduction is dominant in the whole year be-cause wind is blocked. Therefore,the cooling effect of embankment with a block stone interlayer to the soil beneath it is produced by enforced convection and weak free air convection;both its process and the cooling intensity are controlled by the local wind speed and direction. Because of the difference in the cooling effects,the soil temperature beneath the embankment has a temperature difference of 2℃―4℃ between the open and closed conditions.展开更多
Energy consumption of block-cutting machines represents a major cost item in the processing of travertines and other natural stones.Therefore,determining the optimum sawing conditions for a particular stone is of majo...Energy consumption of block-cutting machines represents a major cost item in the processing of travertines and other natural stones.Therefore,determining the optimum sawing conditions for a particular stone is of major importance in the natural stone-processing industry.An experimental study was carried out utilizing a fully instrumented block-cutter to investigate the sawing performances of five different types of travertine blocks during cutting with a circular diamond saw,The sawing tests were performed in the down-cutting mode,Performance measurements were determined by measuring the cutting speed and energy consumption.Then,specific energy was determined.The one main cutting parameter,cutting speed,was varied in the investigation of optimum cutting performance.Furthermore,some physico-mechanical properties of the travertine blocks were determined in the laboratory.As a result,it is found that the energy consumption(specific energy) of block cutting machines is highly affected by cutting speed.It is determined that specific energy value usually decreases when cutting speed increases.When the cutting speed is higher than the determined value,the diamond saw can become stuck in the travertine block;this situation can be a problem for the block-cutting machine,As a result,the optimum cutting speed obtained for the travertine mines examined is approximately 1.5-2.0 m/min.展开更多
基金Supported by the Outstanding Youth Foundation Project, the National Natural Science Foundation of China (Grant No. 40625004)the National Basic Research Program "973 Program" (Grant No. 2002CB412704)
文摘In order to study the cooling mechanism of embankment with block stone interlayer under open and closed conditions,an experimental railway section was built and data within one freeze-thaw cycle were collected. The results explain well the cooling mechanism of embankment with block stone interlayer. Under the open condition in cold seasons,the enforced convection effect occurs within block stone interlayer when the wind speed is large;however,the weak air convection occurs within the block stone interlayer near the bottom of the embankment when the wind speed is slow. Under the open condition in warm seasons,heat conduc-tion occurs within block stone interlayer due to the change in wind speed and di-rection. Under the closed condition,however,the enforced convection within block stone interlayer is so weak that heat conduction is dominant in the whole year be-cause wind is blocked. Therefore,the cooling effect of embankment with a block stone interlayer to the soil beneath it is produced by enforced convection and weak free air convection;both its process and the cooling intensity are controlled by the local wind speed and direction. Because of the difference in the cooling effects,the soil temperature beneath the embankment has a temperature difference of 2℃―4℃ between the open and closed conditions.
文摘Energy consumption of block-cutting machines represents a major cost item in the processing of travertines and other natural stones.Therefore,determining the optimum sawing conditions for a particular stone is of major importance in the natural stone-processing industry.An experimental study was carried out utilizing a fully instrumented block-cutter to investigate the sawing performances of five different types of travertine blocks during cutting with a circular diamond saw,The sawing tests were performed in the down-cutting mode,Performance measurements were determined by measuring the cutting speed and energy consumption.Then,specific energy was determined.The one main cutting parameter,cutting speed,was varied in the investigation of optimum cutting performance.Furthermore,some physico-mechanical properties of the travertine blocks were determined in the laboratory.As a result,it is found that the energy consumption(specific energy) of block cutting machines is highly affected by cutting speed.It is determined that specific energy value usually decreases when cutting speed increases.When the cutting speed is higher than the determined value,the diamond saw can become stuck in the travertine block;this situation can be a problem for the block-cutting machine,As a result,the optimum cutting speed obtained for the travertine mines examined is approximately 1.5-2.0 m/min.
