The mega debris flow occurred on August 13 th 2010 in Qingping town,China(hereafter called '8.13' Debris Flow) have done great damage to the local habitants as well as to the re-construction projects in the qu...The mega debris flow occurred on August 13 th 2010 in Qingping town,China(hereafter called '8.13' Debris Flow) have done great damage to the local habitants as well as to the re-construction projects in the quake-hit areas,and the channel-fill deposit problem caused by the debris flow was the most destructive.Moreover,it is of high possibility that an even severe deposit problem would reappear and result in worse consequences.In order to maximize risk reduction of this problem,relevant departments of the government established a series of emergency river restoration schemes,for which the numerical analysis is an important procedure to evaluate and determine the optimized one.This study presents a numerical analysis by applying a twodimensional debris flow model combined with a relevant water-sediment model to simulate the deposit during the progress of the debris flow,and to calculate and analyze the river flow field under both the present condition and different restoration conditions.The results show that the debris flow model,which takes the confluence of the Wenjia Gully to the main river into account,could simulate the deposit process quite well.In the reproduced debris flow from the simulation of the '8.13' Debris Flow,the original river flow path has switched to a relatively lower place just along the right bank with a high speed of near 7m.s-1 after being blocked by the deposit,which is highly hazardous.To prevent this hazard,a recommended scheme is derived through inter-comparison of different restoration conditions.It shows that the recommended scheme is able to reduce the water level and as well to regulate the flow path.Based on the given conditions of the mainstream and the tributary confluence for the simulated '8.13' Debris Flow,when encountering a debris flow with deposit volume less than 0.5 million m3,the river channel can endure a 20-year return flood;however,when the deposit volume increases to 2 million m3,the flood capacity of the river will be greatly impacted and the scheme becomes invalid.The recommended scheme supported by the present study has been applied to the emergency river restoration after this mega-debris flow.展开更多
Enhanced geothermal system(EGS)is a primary method to develop geothermal resources stored in hot dry rock(HDR),but it faces several key problems,such as unreasonable hydraulic fracture networks at high reservoir tempe...Enhanced geothermal system(EGS)is a primary method to develop geothermal resources stored in hot dry rock(HDR),but it faces several key problems,such as unreasonable hydraulic fracture networks at high reservoir temperature,unclear multi-scale and multi-field coupling regularity,low heat extraction efficiency caused by the flashing flow in geothermal wells,and low thermoelectric conversion efficiency of geothermal fluid,which restricts the large-scale commercial development of geothermal resources.To resolve these major bottleneck problems,systematically reviews and analysis of the research progress and development trend of EGS are conducted in this paper.Particular attentions are devoted to four key technologies involved in the development of HDR geothermal resource by EGS:(1)the hydraulic fracturing technology for HDR reservoirs,including reservoir reconstruction methods,hydraulic fracturing network forming mechanisms and fracture propagation prediction models is illustrated in detail;(2)the fracture characterization methods,mathematical models and solution methods are described from three aspects including pore-scale multi-field coupled models,reservoir-scale multi-field coupled models and upscaling methods;(3)the efficient extraction technology of wellbore thermal fluid,involving the mechanism of flashing flows in geothermal wells and the experimental and numerical methods for investigating the characteristics offlashing flows are discussed;(4)the HDR geothermal power generation technologies,considering the principles of geothermal power generation,the types of power generation systems and the main application markets are introduced.In conclusion,EGS is a technology-intensive system,however,due to the complex working conditions of the underground reservoirs and the instability of the ground equipment,theoretical research tends to be separated from the practice.For the purpose of promoting the applicability of EGS,intimate combination and mutual guidance with the pilot tests are necessary to develop a production-research combined mode,and to raise the awareness and break through the key points in a constant back-and-forth.展开更多
基金supported by the National Basic Research Program of China ("973" Project) (Grant No. 2011CB409903)the National Natural Science Foundation of China (Grant No. 50739002)
文摘The mega debris flow occurred on August 13 th 2010 in Qingping town,China(hereafter called '8.13' Debris Flow) have done great damage to the local habitants as well as to the re-construction projects in the quake-hit areas,and the channel-fill deposit problem caused by the debris flow was the most destructive.Moreover,it is of high possibility that an even severe deposit problem would reappear and result in worse consequences.In order to maximize risk reduction of this problem,relevant departments of the government established a series of emergency river restoration schemes,for which the numerical analysis is an important procedure to evaluate and determine the optimized one.This study presents a numerical analysis by applying a twodimensional debris flow model combined with a relevant water-sediment model to simulate the deposit during the progress of the debris flow,and to calculate and analyze the river flow field under both the present condition and different restoration conditions.The results show that the debris flow model,which takes the confluence of the Wenjia Gully to the main river into account,could simulate the deposit process quite well.In the reproduced debris flow from the simulation of the '8.13' Debris Flow,the original river flow path has switched to a relatively lower place just along the right bank with a high speed of near 7m.s-1 after being blocked by the deposit,which is highly hazardous.To prevent this hazard,a recommended scheme is derived through inter-comparison of different restoration conditions.It shows that the recommended scheme is able to reduce the water level and as well to regulate the flow path.Based on the given conditions of the mainstream and the tributary confluence for the simulated '8.13' Debris Flow,when encountering a debris flow with deposit volume less than 0.5 million m3,the river channel can endure a 20-year return flood;however,when the deposit volume increases to 2 million m3,the flood capacity of the river will be greatly impacted and the scheme becomes invalid.The recommended scheme supported by the present study has been applied to the emergency river restoration after this mega-debris flow.
基金supported by the Key Program of National Natural Science Foundation of China“Thermo-fluid-mechanical-chemical coupling research on heat-mass transport mechanism of enhanced geothermal system”(No.51936001).
文摘Enhanced geothermal system(EGS)is a primary method to develop geothermal resources stored in hot dry rock(HDR),but it faces several key problems,such as unreasonable hydraulic fracture networks at high reservoir temperature,unclear multi-scale and multi-field coupling regularity,low heat extraction efficiency caused by the flashing flow in geothermal wells,and low thermoelectric conversion efficiency of geothermal fluid,which restricts the large-scale commercial development of geothermal resources.To resolve these major bottleneck problems,systematically reviews and analysis of the research progress and development trend of EGS are conducted in this paper.Particular attentions are devoted to four key technologies involved in the development of HDR geothermal resource by EGS:(1)the hydraulic fracturing technology for HDR reservoirs,including reservoir reconstruction methods,hydraulic fracturing network forming mechanisms and fracture propagation prediction models is illustrated in detail;(2)the fracture characterization methods,mathematical models and solution methods are described from three aspects including pore-scale multi-field coupled models,reservoir-scale multi-field coupled models and upscaling methods;(3)the efficient extraction technology of wellbore thermal fluid,involving the mechanism of flashing flows in geothermal wells and the experimental and numerical methods for investigating the characteristics offlashing flows are discussed;(4)the HDR geothermal power generation technologies,considering the principles of geothermal power generation,the types of power generation systems and the main application markets are introduced.In conclusion,EGS is a technology-intensive system,however,due to the complex working conditions of the underground reservoirs and the instability of the ground equipment,theoretical research tends to be separated from the practice.For the purpose of promoting the applicability of EGS,intimate combination and mutual guidance with the pilot tests are necessary to develop a production-research combined mode,and to raise the awareness and break through the key points in a constant back-and-forth.
