Swelling and shrinkage due to moisture-change is one of the characteristics of the expansive soil,which is similar to the behavior of most materials under thermal effect,If the deformation is restricted,stress in expa...Swelling and shrinkage due to moisture-change is one of the characteristics of the expansive soil,which is similar to the behavior of most materials under thermal effect,If the deformation is restricted,stress in expansive soil is caused by the swell-shrinking.The stress is defined as "moisture-change stress" and is adopted to analyze swell-shrinkage deformation based on the elasticity mechanics theory.The state when the total stress becomes equal to the soil tensile strength is considered as the cracking criterion as moisture-change increases.Then,the initial cracking mechanism due to evaporation is revealed as follows:Different rates of moisture loss at different depths result in greater shrinkage deformation on the surface while there is smaller shrinkage deformation at the underlayer in expansive soil;cracks will grow when the nonuniform shrinkage deformation increases to a certain degree.A theoretical model is established,which may be used to calculate the stress caused by moisture-change.The depth of initial cracks growing is predicted by the proposed model in expansive soil,A series of laboratory tests are carried out by exposing expansive soil samples with different moisture-changes.The process of crack propagation is investigated by resistivity method.The test results show good consistency with the predicted results by the proposed theoretical model.展开更多
As a result of a sustained drought in the Southwestern United States, and in order to maintain existing water capacity in the Las Vegas Valley, the Southern Nevada Water Authority constructed a new deep- water intake ...As a result of a sustained drought in the Southwestern United States, and in order to maintain existing water capacity in the Las Vegas Valley, the Southern Nevada Water Authority constructed a new deep- water intake (Intake No. 3) located in Lake Mead. The project included a 185 m deep shaft, 4.7 km tunnel under very difficult geological conditions, and marine works for a submerged intake. This paper presents the experience that was gained during the design and construction and the innovative solutions that were developed to handle the difficult conditions that were encountered during tunneling with a dual- mode slurry tunnel-boring machine (TBM) in up to 15 bar (l bar = l0s Pa) pressure. Specific attention is given to the main challenges that were overcome during the TBM excavation, which included the mode of operation, face support pressures, pre-excavation grouting, and maintenance; to the construction of the intake, which involved deep underwater shaft excavation with blasting using shaped charges; to the construction of the innovative over 1200 t concrete-and-steel intake structure; to the placement of the intake structure in the underwater shaft; and to the docking and connection to an intake tunnel excavated by hybrid TBM.展开更多
About 75% water-inrush accidents in China are caused by geological structure such as faults, therefore, it is necessary to investigate the water-inrush mechanism of faults to provide references for the mining activity...About 75% water-inrush accidents in China are caused by geological structure such as faults, therefore, it is necessary to investigate the water-inrush mechanism of faults to provide references for the mining activity above confined water. In this paper, based on the fluid-solid coupling theory, we built the stress-seepage coupling model for rock, then we combined with an example of water-inrush caused by fault, studied the water-inrush mechanism by using the numerical software COMSOL Mutiphysics, analyzed the change rule of shear stress, vertical stress, plastic area and water pressure for stope with a fault, and estimated the water-inrush risk at the different distances between working faces and the fault. The numerical simula- tion results indicate that: (1) the water-inrush risk will grow as the decrease of the distance between working face and the fault; (2) the failure mode of the rock in floor with fault is shear failure; (3) the rock between water-containing fault and working face failure is the reason for water-inrush.展开更多
Three Gorges Project (TGP),the largest water resources and hydropower project in the world with huge scale and complex techniques,has great comprehensive benefits mainly in flood control,power generation and navigatio...Three Gorges Project (TGP),the largest water resources and hydropower project in the world with huge scale and complex techniques,has great comprehensive benefits mainly in flood control,power generation and navigation improvement.Through 17-year construction and practice,the project has been successfully completed.Some valuable experience from the successful construction of TGP has been gained for the management system and mechanism of hydropower project construction in China.Its construction management mode produces important influences on the management system of domestic capital construction.With combination of the construction management practice of TGP,the characteristics of management system and mechanism are summarized,and the suggestions on current hydropower development system and construction management mode are put forward.展开更多
The history of the formation of the alpine region is affected by the activities of the glaciers, which have a strong influence on underground works in this area. Mechanized tunneling must adapt to the presence of soun...The history of the formation of the alpine region is affected by the activities of the glaciers, which have a strong influence on underground works in this area. Mechanized tunneling must adapt to the presence of sound and altered rock, as well as to inhomogeneous soil layers that range from permeable gravel to soft clay sediments along the same tunnel. This article focuses on past experiences with tunnel-boring machines (TBMs) in Switzerland, and specifically on the aspects of soil conditioning during a passage through inhomogeneous soft soils. Most tunnels in the past were drilled using the slurry mode (SM), in which the application of different additives was mainly limited to difficult zones of high permeability and stoppages for tool change and modification. For drillings with the less common earth pressure balanced mode (EPBM), continuous foam conditioning and the additional use of polymer and bentonite have proven to be successful. The use of conditioning additives led to new challenges during separation of the slurries (for SM) and disposal of the excavated soil (for EPBM). If the disposal of chemically treated soft soil mate- rial from the earth pressure balanced (EPB) drive in a manner that is compliant with environmental legislation is considered early on in the design and evaluation of the excavation mode, the EPBM can be beneficial for tunnels bored in glacial deposits.展开更多
Analyzed the rule of the Water Flowing Fractured (WFF) zone's development during the fully mechanized top coal caving.Six influence factors of WFF's height were selected,viz.mining thickness,base rock thicknes...Analyzed the rule of the Water Flowing Fractured (WFF) zone's development during the fully mechanized top coal caving.Six influence factors of WFF's height were selected,viz.mining thickness,base rock thickness,dip angle,uniaxial compressing strength of roof,mudstone proportion in overlying rock,and structure of overlying rock. The height-forecasting model of WFF was established based on the Artificial Neural Net-work techniques,and was applied in the first fully mechanized top coal caving face under sea in China.展开更多
The deposit scale in the coal mine shaft usually causes serious accidents, such as making rope broken, cage seized or dropped. To solve this kind of problems, the re-search of the cutting scale mechanism was made, and...The deposit scale in the coal mine shaft usually causes serious accidents, such as making rope broken, cage seized or dropped. To solve this kind of problems, the re-search of the cutting scale mechanism was made, and a new type of removal scale equipment was made with using imported hard alloy material. The cutting experiment and actual cutting show that it can adapt to abominable condition in the shaft, such as narrow space, wet and excessive shaft crevice water and so on, and can work safely and reliably, and has high cutting scale efficiency. It can also cut out the deposit scale in the circular section of shaft.展开更多
According to recent hydropower inventories, the first aim of this paper is to prove that Greece is a real "Archimedean Soft Small Hydro Development Terra Incognita". It is a country in the Era of Transition of nowad...According to recent hydropower inventories, the first aim of this paper is to prove that Greece is a real "Archimedean Soft Small Hydro Development Terra Incognita". It is a country in the Era of Transition of nowadays, having an important unexploited hydropower potential of several TWh and thousands of MW. The second goal is to present the results of rediscovering the old screw pumps and the always-modern Archimedean cochlear screw ideas as a series of soft hydropower turbines with inclined axis rotors and floating spiral screw devices. By following the similarity methodology, a few small-scale models of cochlear rotors were designed, developed and tested in an Armfield hydraulic channel. The conventional and unconventional, low or zero-head screw turbines, could efficiently harness the important and unexploited Greek small potential and kinetic hydraulic energy of all the natural watercourses, the man-made open urban or rural channels and the most important tidal or sea currents, producing useful green electricity. The very promising low-head hydropower inventory of Greece, the preliminary experimental results and the research studies of cochlear projects in watercourses, hydraulic works, tidal conditions of Euripus Strait and in the mysterious "Sea River Current of Cephalonia", seems to give a good answer to the question "Quo Vadis Archimedes nowadays in Greece, in the Era of Transition?".展开更多
The purpose of this paper is to clarify how the Kabu-ido system can be employed to successfully regulate groundwater pumping. This was accomplished by analyzing surviving historical documents, including budgetary note...The purpose of this paper is to clarify how the Kabu-ido system can be employed to successfully regulate groundwater pumping. This was accomplished by analyzing surviving historical documents, including budgetary notes and a diary. The Kabu-ido system was a customary institution for groundwater management in a ring levee area of the Noubi Plain in Japan that consisted of three programs: restriction of groundwater pumping through a permit system, groundwater pricing and economic compensation. The system was created in the 1810s and survived for 100 years. This paper covers the Kabu-ido system from the 1810s to the 1860s, the first half of the 100-year history. Excessive groundwater pumping is not a new environmental problem. Although many case studies have investigated remedial actions, few have investigated how local residents addressed the problem before the 20th century because of a lack of documents. The Kabu-ido system is an exception in which of the procedure was documented in writing. The historical data indicate that it was a pioneering institution for groundwater management.展开更多
基金Project(2006BAB04A10) supported by the National Science and Technology Pillar Program during the 11th Five Year Plan of ChinaProject(51008117) supported by the National Natural Science Foundation of China
文摘Swelling and shrinkage due to moisture-change is one of the characteristics of the expansive soil,which is similar to the behavior of most materials under thermal effect,If the deformation is restricted,stress in expansive soil is caused by the swell-shrinking.The stress is defined as "moisture-change stress" and is adopted to analyze swell-shrinkage deformation based on the elasticity mechanics theory.The state when the total stress becomes equal to the soil tensile strength is considered as the cracking criterion as moisture-change increases.Then,the initial cracking mechanism due to evaporation is revealed as follows:Different rates of moisture loss at different depths result in greater shrinkage deformation on the surface while there is smaller shrinkage deformation at the underlayer in expansive soil;cracks will grow when the nonuniform shrinkage deformation increases to a certain degree.A theoretical model is established,which may be used to calculate the stress caused by moisture-change.The depth of initial cracks growing is predicted by the proposed model in expansive soil,A series of laboratory tests are carried out by exposing expansive soil samples with different moisture-changes.The process of crack propagation is investigated by resistivity method.The test results show good consistency with the predicted results by the proposed theoretical model.
文摘As a result of a sustained drought in the Southwestern United States, and in order to maintain existing water capacity in the Las Vegas Valley, the Southern Nevada Water Authority constructed a new deep- water intake (Intake No. 3) located in Lake Mead. The project included a 185 m deep shaft, 4.7 km tunnel under very difficult geological conditions, and marine works for a submerged intake. This paper presents the experience that was gained during the design and construction and the innovative solutions that were developed to handle the difficult conditions that were encountered during tunneling with a dual- mode slurry tunnel-boring machine (TBM) in up to 15 bar (l bar = l0s Pa) pressure. Specific attention is given to the main challenges that were overcome during the TBM excavation, which included the mode of operation, face support pressures, pre-excavation grouting, and maintenance; to the construction of the intake, which involved deep underwater shaft excavation with blasting using shaped charges; to the construction of the innovative over 1200 t concrete-and-steel intake structure; to the placement of the intake structure in the underwater shaft; and to the docking and connection to an intake tunnel excavated by hybrid TBM.
基金Supported by the National Basic Research Program of China (2010CB226800) the National Natural Science Foundation of China (50904065) the Program for New Century Excellent Talents in University (NCET-09-0728)
文摘About 75% water-inrush accidents in China are caused by geological structure such as faults, therefore, it is necessary to investigate the water-inrush mechanism of faults to provide references for the mining activity above confined water. In this paper, based on the fluid-solid coupling theory, we built the stress-seepage coupling model for rock, then we combined with an example of water-inrush caused by fault, studied the water-inrush mechanism by using the numerical software COMSOL Mutiphysics, analyzed the change rule of shear stress, vertical stress, plastic area and water pressure for stope with a fault, and estimated the water-inrush risk at the different distances between working faces and the fault. The numerical simula- tion results indicate that: (1) the water-inrush risk will grow as the decrease of the distance between working face and the fault; (2) the failure mode of the rock in floor with fault is shear failure; (3) the rock between water-containing fault and working face failure is the reason for water-inrush.
文摘Three Gorges Project (TGP),the largest water resources and hydropower project in the world with huge scale and complex techniques,has great comprehensive benefits mainly in flood control,power generation and navigation improvement.Through 17-year construction and practice,the project has been successfully completed.Some valuable experience from the successful construction of TGP has been gained for the management system and mechanism of hydropower project construction in China.Its construction management mode produces important influences on the management system of domestic capital construction.With combination of the construction management practice of TGP,the characteristics of management system and mechanism are summarized,and the suggestions on current hydropower development system and construction management mode are put forward.
文摘The history of the formation of the alpine region is affected by the activities of the glaciers, which have a strong influence on underground works in this area. Mechanized tunneling must adapt to the presence of sound and altered rock, as well as to inhomogeneous soil layers that range from permeable gravel to soft clay sediments along the same tunnel. This article focuses on past experiences with tunnel-boring machines (TBMs) in Switzerland, and specifically on the aspects of soil conditioning during a passage through inhomogeneous soft soils. Most tunnels in the past were drilled using the slurry mode (SM), in which the application of different additives was mainly limited to difficult zones of high permeability and stoppages for tool change and modification. For drillings with the less common earth pressure balanced mode (EPBM), continuous foam conditioning and the additional use of polymer and bentonite have proven to be successful. The use of conditioning additives led to new challenges during separation of the slurries (for SM) and disposal of the excavated soil (for EPBM). If the disposal of chemically treated soft soil mate- rial from the earth pressure balanced (EPB) drive in a manner that is compliant with environmental legislation is considered early on in the design and evaluation of the excavation mode, the EPBM can be beneficial for tunnels bored in glacial deposits.
基金National Science Support Plan of China(2006BAB16B04)
文摘Analyzed the rule of the Water Flowing Fractured (WFF) zone's development during the fully mechanized top coal caving.Six influence factors of WFF's height were selected,viz.mining thickness,base rock thickness,dip angle,uniaxial compressing strength of roof,mudstone proportion in overlying rock,and structure of overlying rock. The height-forecasting model of WFF was established based on the Artificial Neural Net-work techniques,and was applied in the first fully mechanized top coal caving face under sea in China.
文摘The deposit scale in the coal mine shaft usually causes serious accidents, such as making rope broken, cage seized or dropped. To solve this kind of problems, the re-search of the cutting scale mechanism was made, and a new type of removal scale equipment was made with using imported hard alloy material. The cutting experiment and actual cutting show that it can adapt to abominable condition in the shaft, such as narrow space, wet and excessive shaft crevice water and so on, and can work safely and reliably, and has high cutting scale efficiency. It can also cut out the deposit scale in the circular section of shaft.
文摘According to recent hydropower inventories, the first aim of this paper is to prove that Greece is a real "Archimedean Soft Small Hydro Development Terra Incognita". It is a country in the Era of Transition of nowadays, having an important unexploited hydropower potential of several TWh and thousands of MW. The second goal is to present the results of rediscovering the old screw pumps and the always-modern Archimedean cochlear screw ideas as a series of soft hydropower turbines with inclined axis rotors and floating spiral screw devices. By following the similarity methodology, a few small-scale models of cochlear rotors were designed, developed and tested in an Armfield hydraulic channel. The conventional and unconventional, low or zero-head screw turbines, could efficiently harness the important and unexploited Greek small potential and kinetic hydraulic energy of all the natural watercourses, the man-made open urban or rural channels and the most important tidal or sea currents, producing useful green electricity. The very promising low-head hydropower inventory of Greece, the preliminary experimental results and the research studies of cochlear projects in watercourses, hydraulic works, tidal conditions of Euripus Strait and in the mysterious "Sea River Current of Cephalonia", seems to give a good answer to the question "Quo Vadis Archimedes nowadays in Greece, in the Era of Transition?".
文摘The purpose of this paper is to clarify how the Kabu-ido system can be employed to successfully regulate groundwater pumping. This was accomplished by analyzing surviving historical documents, including budgetary notes and a diary. The Kabu-ido system was a customary institution for groundwater management in a ring levee area of the Noubi Plain in Japan that consisted of three programs: restriction of groundwater pumping through a permit system, groundwater pricing and economic compensation. The system was created in the 1810s and survived for 100 years. This paper covers the Kabu-ido system from the 1810s to the 1860s, the first half of the 100-year history. Excessive groundwater pumping is not a new environmental problem. Although many case studies have investigated remedial actions, few have investigated how local residents addressed the problem before the 20th century because of a lack of documents. The Kabu-ido system is an exception in which of the procedure was documented in writing. The historical data indicate that it was a pioneering institution for groundwater management.