The coal mine roof rating(CMRR) was developed to bridge the gap between geological variation in underground coal mines and engineering design. The CMRR accounts for the compressive strength of the immediate roof, the ...The coal mine roof rating(CMRR) was developed to bridge the gap between geological variation in underground coal mines and engineering design. The CMRR accounts for the compressive strength of the immediate roof, the shear strength and intensity of any discontinuities present, and the moisture sensitivity of the immediate roof. The CMRR has been widely used and validated in Eastern US coal mines, but it has seen limited application in the Western US. This study focuses on roof behavior at a Western coal mine(Mine A). Mine A shows significant lateral geological variation, along with localized faulting and a laterally extensive sandstone channel network. The CMRR is not used to predict roof instability at the mine. It is, therefore, hypothesized that there are other factors that are correlated with roof instability in underground coal mines that could potentially also be considered in conjunction with the CMRR.This hypothesis was tested by collecting 30 CMRR measurements at Mine A. At each measurement location, a binary record of the roof condition(stable or unstable) was made, and other parameters such as depth of cover, presence of faulting, and sandstone channels were also recorded. ANOVA tests showed that the CMRR values and the roof conditions were not strongly correlated, indicating that the CMRR input criteria are not fully predictive of roof stability at this mine. The CMRR values showed statistically significant correlations(p less than 0.05) with faulting as well as with location at an intersection. For areas that had previously experienced roof fall but were currently stable, faulting was correlated with roof condition(p less than 0.05) only when the condition was classified as unstable.展开更多
Since the reform and opening-up to the outside world, China has formed a series of guidelines and policies towards the United States, which are the theoretical foundation of China’s U.S. policy thinking in the New Ce...Since the reform and opening-up to the outside world, China has formed a series of guidelines and policies towards the United States, which are the theoretical foundation of China’s U.S. policy thinking in the New Century. Entering the new century, the international situation has undergone profound and complicated changes, the national strength gap between China and the United States has narrowed, their common interests have expanded, differences and contradictions have increased. Therefore, China stands for both countries to adhere to the direction of developing cooperative partnership, respect each other, abide by the promises, seek equal and mutual benefits and win-win cooperation, and mutually respect each others core interests. The future development of China-U.S. relations still face many challenges and China’s U.S. policy thinking needs to keep abreast with the times.展开更多
基金supported by a NIOSH Capacity Building grant (No. 200-2016-90154) to Drs. G. Walton and E. Holley and collaborators at the Colorado School of Mines
文摘The coal mine roof rating(CMRR) was developed to bridge the gap between geological variation in underground coal mines and engineering design. The CMRR accounts for the compressive strength of the immediate roof, the shear strength and intensity of any discontinuities present, and the moisture sensitivity of the immediate roof. The CMRR has been widely used and validated in Eastern US coal mines, but it has seen limited application in the Western US. This study focuses on roof behavior at a Western coal mine(Mine A). Mine A shows significant lateral geological variation, along with localized faulting and a laterally extensive sandstone channel network. The CMRR is not used to predict roof instability at the mine. It is, therefore, hypothesized that there are other factors that are correlated with roof instability in underground coal mines that could potentially also be considered in conjunction with the CMRR.This hypothesis was tested by collecting 30 CMRR measurements at Mine A. At each measurement location, a binary record of the roof condition(stable or unstable) was made, and other parameters such as depth of cover, presence of faulting, and sandstone channels were also recorded. ANOVA tests showed that the CMRR values and the roof conditions were not strongly correlated, indicating that the CMRR input criteria are not fully predictive of roof stability at this mine. The CMRR values showed statistically significant correlations(p less than 0.05) with faulting as well as with location at an intersection. For areas that had previously experienced roof fall but were currently stable, faulting was correlated with roof condition(p less than 0.05) only when the condition was classified as unstable.
文摘Since the reform and opening-up to the outside world, China has formed a series of guidelines and policies towards the United States, which are the theoretical foundation of China’s U.S. policy thinking in the New Century. Entering the new century, the international situation has undergone profound and complicated changes, the national strength gap between China and the United States has narrowed, their common interests have expanded, differences and contradictions have increased. Therefore, China stands for both countries to adhere to the direction of developing cooperative partnership, respect each other, abide by the promises, seek equal and mutual benefits and win-win cooperation, and mutually respect each others core interests. The future development of China-U.S. relations still face many challenges and China’s U.S. policy thinking needs to keep abreast with the times.
