The configuration of underground powerhouses is crucial in pumped-storage hydropower projects,which play a vital role in maintaining grid stability,facilitating the integration of renewable energy sources,and managing...The configuration of underground powerhouses is crucial in pumped-storage hydropower projects,which play a vital role in maintaining grid stability,facilitating the integration of renewable energy sources,and managing flood risks.However,geotechnical challenges,such as complex joint orientations,anisotropy in in-situ stress,and rock damage caused by excavation,require thorough stability assessments.This research employs the ubiquitous anisotropic joint model within FLAC3D to investigate the effects of joint dip angle,joint dip direction,and the alignment of in-situ stress on the stability of surrounding rock formations.The key parameters analyzed include joint cohesion,friction angle,and the magnitude of in-situ stress.The numerical results indicate that deformation is minimized when the axis of the powerhouse is aligned with the major principal stress.Furthermore,joint dip angles between 65°and 70°lead to a 50%reduction in both displacement and plastic zone volume.Additionally,angles less than 40°between the joint dip direction and the powerhouse axis enhance stability.These findings provide practical recommendations for optimizing the orientation of powerhouses in geomechanical contexts similar to those characterized by foliated sericite phyllite with moderate joint persistence.展开更多
The big underground powerhouse cavern of the China Baihetan hydropower plant is 438m long,34m wide,and 88.7m high.It is cut by a weak interlayer shear zone and its high sidewall poses a huge stability problem.This pap...The big underground powerhouse cavern of the China Baihetan hydropower plant is 438m long,34m wide,and 88.7m high.It is cut by a weak interlayer shear zone and its high sidewall poses a huge stability problem.This paper reports our successful solution of this problem through numerical simulations and a replacement-tunnel scheme in the detailed design stage and close site monitoring in the excavation stage.Particularly,in the detail design stage,mechanical parameters of the shear zone were carefully determined through laboratory experiments and site tests.Then,deformation of the surrounding rocks and the shear zone under high in situ stress conditions was predicted using 3 Dimensional Distinct Element Code(3DEC).Subsequently,a replacement-tunnel scheme was proposed for the treatment on the shear zone to prevent severe unloading relaxation of surrounding rocks.In the construction period,excavation responses were closely monitored on deformations of surrounding rocks and the shear zone.The effect of local cracking in the replacement tunnels on sidewall stability was evaluated using the strength reduction method.These monitoring results were compared with the predicted numerical simulation in the detailed design stage.It is found that the shear zone greatly modified the deformation mode of the cavern surrounding rocks.Without any treatment,rock mass deformation on the downstream sidewall was larger than 125mm and the shearing deformation of the shear zone was 60–70 mm.These preset replacement tunnels can reduce not only the unloading and relaxation of rock masses but also the maximum shearing deformation of the shear zone by 10–20 mm.The predictions by numerical simulation were in good agreement with the monitoring results.The proposed tunnel-replacement scheme can not only restrain the shear zone deformation but also enhance the safety of surrounding rocks and concrete tunnels.This design procedure offers a good reference for interaction between a big underground cavern and a weak layer zone in the future.展开更多
By summarizing the characteristics of the global energy structure and China’s energy resource endowment, this study analyzes the historical context and opportunities for China to build an “energy powerhouse”, and p...By summarizing the characteristics of the global energy structure and China’s energy resource endowment, this study analyzes the historical context and opportunities for China to build an “energy powerhouse”, and proposes pathways and measures for its realization. It is indicated that the energy resource endowment in China is characterized by abundant coal, limited oil and gas, and vast renewable potential, coupled with an energy consumption structure characterized by high coal consumption, low oil and gas consumption, and rapidly growing renewable energy use. The “whole-energy system” approach that integrates multi-energy complementarity, green development, stable supply, smart utilization and carbon neutrality is an effective solution to addressing energy transition and energy independence. To build an “energy powerhouse”, China can follow the approach of the steady and orderly low-carbon development of fossil fuels, the safe and scaled development of new energy, the integrated development of a carbon-neutral “whole-energy system”, and the shared development of the “Belt and Road” energy corridor. The construction of an “energy powerhouse” should follow a “three-phase” strategic pathway: from 2025 to 2030, achieving peak primary energy consumption and “carbon peaking”;from 2031 to 2050, energy production will achieve parity with consumption for the first time, striving for “energy independence”;and from 2051 to 2060, aiming for “carbon neutrality”, and establishing an “energy powerhouse”. Building an “energy powerhouse” will fundamentally safeguard national energy security, advance the achievement of carbon neutrality goals, provide Chinese solutions for global energy transition and green Earth construction, and support the modernization and great rejuvenation of the Chinese nation.展开更多
To investigate the stability of rock mass in high geostress underground powerhouse caverns subjected to excavation,a microseismic(MS)monitoring system was established and the discrete element method(DEM)-based numeric...To investigate the stability of rock mass in high geostress underground powerhouse caverns subjected to excavation,a microseismic(MS)monitoring system was established and the discrete element method(DEM)-based numerical simulation was carried out.The tempo-spatial damage characteristics of rock mass were analyzed.The evolution laws of MS source parameters during the formation of a rock collapse controlled by high geostress and geological structure were investigated.Additionally,a three-dimensional DEM model of the underground powerhouse caverns was built to reveal the deformation characteristics of rock mass.The results indicated that the MS events induced by excavation of high geostress underground powerhouse caverns occurred frequently.The large-stake crown of the main powerhouse was the main damage area.Prior to the rock collapse,the MS event count and accumulated energy release increased rapidly,while the apparent stress sharply increased and then decreased.The amount and proportion of shear and mixed MS events remarkably increased.The maximum displacement was generally located near the spandrel areas.The MS monitoring data and numerical simulation were in good agreement,which can provide significant references for damage evaluation and disaster forecasting in high geostress underground powerhouse caverns.展开更多
Rock mass large deformation in underground powerhouse caverns has been a severe hazard in hydropower engineering in Southwest China.During the development of rock mass large deformation,a sequence of fractures was gen...Rock mass large deformation in underground powerhouse caverns has been a severe hazard in hydropower engineering in Southwest China.During the development of rock mass large deformation,a sequence of fractures was generated that can be monitored using microseismic(MS)monitoring techniques.Two MS monitoring systems were established in two typical underground powerhouse caverns featuring distinct geostress levels.The MS b-values associated with rock mass large deformation and their temporal variation are analysed.The results showed that the MS bvalue in course of rock mass deformation was less than 1.0 in the underground powerhouse caverns at a high stress level while larger than 1.5 at a low stress level.Prior to the rock mass deformation,the MS b-values derived from both the high-stress and low-stress underground powerhouse caverns show an incremental decrease over 10%within 10 d.The results contribute to understanding the fracturing characteristics of MS sources associated with rock mass large deformation and provide a reference for early warning of rock mass large deformation in underground powerhouse caverns.展开更多
The stability of the surrounding rocks of large underground powerhouses is always emphasized during the construction process,especially in large-scale underground projects under construction,such as the Baihetan hydro...The stability of the surrounding rocks of large underground powerhouses is always emphasized during the construction process,especially in large-scale underground projects under construction,such as the Baihetan hydropower station in China.According to field investigations,numerical simulations and monitoring data analysis,we present a comparative analysis of the deformation and failure characteristics of the surrounding rocks of underground powerhouses on the left and right banks of the Baihetan hydropower station.The failure characteristics and deformation magnitude of the underground powerhouses on the left and right banks are quite different.Under the disadvantageous condition where the maximum principal stress intersects the axis of the powerhouse at a large angle,the left bank underground powerhouse shows prominent stress-controlled failure characteristics such as spalling,slack collapse and concrete cracking.Although the maximum principal stress is in the favorable condition which intersects the right bank powerhouse at a small angle,the relatively high intermediate principal stress with an angle subvertical to the right bank powerhouse plays an essential role in its deformation and failure,indicating that the influence of high intermediate principal stress cannot be ignored.In addition,structural plane-controlled failure and large deformation are also more evident on the right bank due to the extensive distribution of weak structural planes and complex surrounding rock properties.展开更多
Based on the analyses of data obtained from the underground powerhouse at Jinping I hydropower station,a comprehensive review of engineering rock mechanics practice in the underground powerhouse is first conducted.The...Based on the analyses of data obtained from the underground powerhouse at Jinping I hydropower station,a comprehensive review of engineering rock mechanics practice in the underground powerhouse is first conducted.The distribution of strata,lithology,and initial geo-stress,the excavation process and corresponding rock mass support measures,the deformation and failure characteristics of the surrounding rock mass,the stress characteristics of anchorage structures in the cavern complex,and numerical simulations of surrounding rock mass stability and anchor support performance are presented.The results indicate that the underground powerhouse of Jinping I hydropower station is characterized by high to extremely high geo-stresses during rock excavation.Excessive surrounding rock mass deformation and high stress of anchorage structures,surrounding rock mass unloading damage,and local cracking failure of surrounding rock masses,etc.,are mainly caused by rock mass excavation.Deformations of surrounding rock masses and stresses in anchorage structures here are larger than those found elsewhere:20%of extensometers in the main powerhouse record more than 50 mm with the maximum at around 250 mm observed in the downstream sidewall of the transformer hall.There are about 25%of the anchor bolts having recorded stresses of more than 200 MPa.Jinping I hydropower plant is the first to have an underground powerhouse construction conducted in host rocks under extremely high geo-stress conditions,with the ratio of rock mass strength to geo-stress of less than 2.0.The results can provide a reference to underground powerhouse construction in similar geological conditions.展开更多
It is imperative to understand the spatial and temporal coordination deformation mechanism and develop targeted deformation control technologies for high sidewall—bottom transfixion(HSBT)zones to guarantee the stabil...It is imperative to understand the spatial and temporal coordination deformation mechanism and develop targeted deformation control technologies for high sidewall—bottom transfixion(HSBT)zones to guarantee the stability of rock surrounding underground hydro-powerhouses under complex geological conditions.In this study,the spatial and temporal coordinated deformation control of HSBT zones was addressed from the aspects of the deformation mechanism,failure characteristics,and control requirements,and some coordinated deformation control technologies were proposed.On this basis,a case study was conducted on the deformation control of the HSBT zone of the underground powerhouse at the Wudongde hydropower station,China.The results showed that the relationship between excavation and support,and the mismatch of deformation and support of the surrounding rock mass in the HSBT zone of underground caverns with a large span and high in-situ stress can be appropriately handled.The solution requires proper excavation and construction procedures,fine blasting control,composite and timely support,and real-time monitoring and dynamic feedback.The technologies proposed in this study will ensure the safe,high-quality,and orderly construction of the Baihetan and Wudongde underground caverns,and can be applied to other similar projects.展开更多
Based on the underground powerhouse of Shuangjiangkou hydropower station,Octree theory is adopted to define the indices of the microseismic(MS)spatial aggregation degree and the deviation values of MS count and energy...Based on the underground powerhouse of Shuangjiangkou hydropower station,Octree theory is adopted to define the indices of the microseismic(MS)spatial aggregation degree and the deviation values of MS count and energy.The relationship between the MS multiple parameters and surrounding rock mass instability is established from three aspects:time,space,and strength.Supplemented by the center frequency of the signal evolution characteristics,A fuzzy comprehensive evaluation model and the evolution trend of the MS event center frequency are constructed to quantitatively describe the early warning state of the surrounding rock mass instability.The results show that the multilevel tree structure and voxels generated based on the Octree theory fit relatively well with the set of MS points in threedimensional space.The fuzzy comprehensive evaluation model based on MS spatial aggregation and MS count and energy deviation values enables three-dimensional visualization of the potential damage area and damage extent of the surrounding rock mass.The warning time and potential damage zone quantified are highly consistent with the characteristics of MS precursors,with wide recognition and field investigation results,which fully validate the rationality and applicability of the proposed method.These findings can provide references for the early warning of surrounding rock mass instability in similar underground engineering.展开更多
A high-precision microseismic(MS)monitoring system was built to monitor surrounding rock microfractures in the underground powerhouse on the left bank of Shuangjiangkou Hydropower Station.The surrounding rock damage a...A high-precision microseismic(MS)monitoring system was built to monitor surrounding rock microfractures in the underground powerhouse on the left bank of Shuangjiangkou Hydropower Station.The surrounding rock damage area with spatiotemporal clustering of MS activities was studied for qualitative analysis of the damage mechanism of surrounding rock microfractures,based on the source parameters of MS events.The surrounding rock microfracture scale characterized by the source radius of MS events was considered to establish the constitutive relation.MS information was imported into the model for numerical analysis using fast Lagrangian analysis of continuain 3 dimensions(FLAC^(3D)).The results indicated that the numerical simulation results considering MS damage can better reflect the actual situation of the field.The surrounding rock microfractures mainly showed mixed failure characteristics.Shear failures appeared in localized areas while the fracture scale of sections from K0e33 m to K0e15 m on the vault was large.The deformation increment caused by microfracture damage in the shallow surrounding rock of the top arch accounted for 10%e13%,and the stress decrement in the surrounding rock caused by microfracture damage accounted for about 10%.展开更多
With the increase of capacity and size of the hydro-generator unit, the spiral case becomes a more super-giant hydraulic structure with very high HD value, where H and D denote water head and maximum intake diameter o...With the increase of capacity and size of the hydro-generator unit, the spiral case becomes a more super-giant hydraulic structure with very high HD value, where H and D denote water head and maximum intake diameter of spiral case, respectively. Due to the induced lower stiffness by the more giant size and adverse operation conditions, dynamic performances of the powerhouse and the supporting structure for the giant units have become more important and attracted much attention. If the manner of steel spiral case embedded directly in concrete is adopted, on some locations of the concrete surrounding the spiral case, distributed and concentrated cracks will emerge due to high tensile stress. Although the concrete is reinforced well to control the maximum crack width, definitely these cracks will reduce the local and entire stiffness of the powerhouse. Under dynamic loads such as hydraulic forces including water pressure pulsation in flow passage acting on the structure, effect of the cracks on the dynamic characteristics of the local members and entire structure needs to be evaluated. However, research on this subject is few in hydroelectric engineering. In this paper, Three-Gorge Project was taken as an example to evaluate effect of such cracks on natural frequencies and the vibration responses of the powerhouse under hydraulic and earthquake forces in detail. Results show that cracks only reduce the local structural stiffness greatly but have little effect on the entire powerhouse especially the superstructure; vibrations of powerhouse with cracks in concrete surrounding the spiral case are still under the design limits. Results in this paper have been verified by practice of Three-Gorge Project.展开更多
The complicated rock structures and the stability of surrounding rocks of the underground powerhouse were the key rock mechanical problems in Shuibuya hydropower station.In order to overcome the related rock mechanica...The complicated rock structures and the stability of surrounding rocks of the underground powerhouse were the key rock mechanical problems in Shuibuya hydropower station.In order to overcome the related rock mechanical problems encountered during its construction,a comprehensive research was carried out for the underground powerhouse in Shuibuya hydropower station based on a detailed geological survey.It covers the investigations on the initial in-situ stress distribution features,rock mechanical properties,engineering rock mass classifications by different methods,numerical modeling for stability and support analysis,proper measures for rock excavation and support.The results show that the rock excavations of the underground powerhouse under the given geological conditions can be controlled effectively.Some measures,suggested by the designers,are proved to be rational and effective.These measures mainly consist of:(1) the soft rock replacements by concrete in local area below the crane beam,(2) the shotcrete and reinforcement by rock bolts and anchor cables in surrounding rocks,and (3) 2 m concrete placement on the rock bench between adjacent tailrace tubes.The engineering practice shows that the treated surrounding rocks have a good overall stability.The deformation behaviors observed by safety equipments are within the designing limits.The research conclusions on the related rock mechanical problems,prior to the underground powerhouse excavations,are reliable.展开更多
In this paper,three different modeling ranges were selected in the structural analysis for a hydropower house.The analysis was carried out using ABAQUS 6.6.The modeling range has a remarkable effect on finite element ...In this paper,three different modeling ranges were selected in the structural analysis for a hydropower house.The analysis was carried out using ABAQUS 6.6.The modeling range has a remarkable effect on finite element method(FEM) calculation result at the middle position of typical cross-sections where the concrete is relatively thin,and at the region close to turbine floor.If the ventilation barrel,floor slabs and columns above turbine floor are excluded from FEM model,the maximum rise difference of pedestal structure increases by about 24% compared with that of the whole model.It is indicated that different modeling ranges indeed affect FEM calculation result,and the structure above turbine floor in the FEM model should be included.展开更多
Under forced ventilation,the dust diffusion of underground powerhouse construction is investigated using a 3D high Reynolds number k-ε model.The interfacial momentum transfers and the wall roughness in the wall funct...Under forced ventilation,the dust diffusion of underground powerhouse construction is investigated using a 3D high Reynolds number k-ε model.The interfacial momentum transfers and the wall roughness in the wall function are considered.Ventilation in the third layer of underground powerhouse of Xiangjiaba hydropower station is used as a case.The geometric structure has a decisive effect on the airflow distribution.It is concluded that the dust concentration decreases gradually with the increase of the ventilation time.However,iso-concentration curves have the same tendency after 1 800 s.The dust concentration meets the ventilation and dust-prevention health standard after 2 300 s.The prediction by the present model is confirmed by the experimental measurement by Nakayama.展开更多
This year, 70 years after the founding of New China, the Chinese nation has made a historic leap from standing up to becoming rich and strong. In this great change, the textile industry has achieved all-round and deep...This year, 70 years after the founding of New China, the Chinese nation has made a historic leap from standing up to becoming rich and strong. In this great change, the textile industry has achieved all-round and deep-seated development, playing an increasingly important role in serv- ing the overall strategic situation of the country.展开更多
Recent breakthrough achievements such as the launch of DeepSeek's revolutionary AI models and the collection of samples from the far side of the moon are indicators of just how far China has developed in science a...Recent breakthrough achievements such as the launch of DeepSeek's revolutionary AI models and the collection of samples from the far side of the moon are indicators of just how far China has developed in science and technology.展开更多
The construction of an agricultural powerhouse in China is confronted with the practical dilemma of relying mainly on small-scale farming and weak agricultural competitiveness,so an exploration of feasible paths for b...The construction of an agricultural powerhouse in China is confronted with the practical dilemma of relying mainly on small-scale farming and weak agricultural competitiveness,so an exploration of feasible paths for building an agricultural powerhouse is urgently needed.This study constructed indicator systems that reflect the level of agricultural development from three dimensions:resource endowment,output status,and urban-rural relations.On this basis,the gap between China and the world’s representative agricultural powers was analyzed,and the evolutionary characteristics of agricultural policies in the European Union,Japan,and the United States were explored,leading to relevant policy implications.This analysis found that the superficial problems of China's agricultural development lie in the relative scarcity of good resource conditions and insufficient modernization,while the underlying crux lies in the lack of obvious industrial competitive advantages,which is especially reflected in the lack of coordinated development between industry,agriculture,and urban-rural areas.The European Union,Japan,and the United States all focus on improving the international competitiveness of agriculture based on their comparative advantages,attach importance to the comprehensive development of rural areas,and have effectively constructed coordinated industry-agriculture and urban-rural relations,all of which have promoted the comprehensive development of agriculture.China’s construction of an agricultural powerhouse should be based on its national conditions and the general laws governing the building a world-class agricultural powerhouse.The strategy should include focusing on building a diversified food supply system to ensure food security;focusing on the modernization of agricultural science and technology,which will promote the process of agricultural modernization;promoting the development of the entire agricultural industry chain,which will enhance the competitiveness and risk resistance of the agricultural industry;accelerating public policy reform and continuing to promote urban-rural integration.展开更多
China retained its position as the world's second-largest film market in 2023,showcasing a steady upward trajectory in revenue and audience engagement.Meanwhile,the Indian film industry,renowned for its glitz,vibr...China retained its position as the world's second-largest film market in 2023,showcasing a steady upward trajectory in revenue and audience engagement.Meanwhile,the Indian film industry,renowned for its glitz,vibrancy,and drama,has earned global repute as one of the largest cinema hubs in the world.展开更多
文摘The configuration of underground powerhouses is crucial in pumped-storage hydropower projects,which play a vital role in maintaining grid stability,facilitating the integration of renewable energy sources,and managing flood risks.However,geotechnical challenges,such as complex joint orientations,anisotropy in in-situ stress,and rock damage caused by excavation,require thorough stability assessments.This research employs the ubiquitous anisotropic joint model within FLAC3D to investigate the effects of joint dip angle,joint dip direction,and the alignment of in-situ stress on the stability of surrounding rock formations.The key parameters analyzed include joint cohesion,friction angle,and the magnitude of in-situ stress.The numerical results indicate that deformation is minimized when the axis of the powerhouse is aligned with the major principal stress.Furthermore,joint dip angles between 65°and 70°lead to a 50%reduction in both displacement and plastic zone volume.Additionally,angles less than 40°between the joint dip direction and the powerhouse axis enhance stability.These findings provide practical recommendations for optimizing the orientation of powerhouses in geomechanical contexts similar to those characterized by foliated sericite phyllite with moderate joint persistence.
基金Program of China Three Gorges Corporation,Grant/Award Number:BHT 0679-1。
文摘The big underground powerhouse cavern of the China Baihetan hydropower plant is 438m long,34m wide,and 88.7m high.It is cut by a weak interlayer shear zone and its high sidewall poses a huge stability problem.This paper reports our successful solution of this problem through numerical simulations and a replacement-tunnel scheme in the detailed design stage and close site monitoring in the excavation stage.Particularly,in the detail design stage,mechanical parameters of the shear zone were carefully determined through laboratory experiments and site tests.Then,deformation of the surrounding rocks and the shear zone under high in situ stress conditions was predicted using 3 Dimensional Distinct Element Code(3DEC).Subsequently,a replacement-tunnel scheme was proposed for the treatment on the shear zone to prevent severe unloading relaxation of surrounding rocks.In the construction period,excavation responses were closely monitored on deformations of surrounding rocks and the shear zone.The effect of local cracking in the replacement tunnels on sidewall stability was evaluated using the strength reduction method.These monitoring results were compared with the predicted numerical simulation in the detailed design stage.It is found that the shear zone greatly modified the deformation mode of the cavern surrounding rocks.Without any treatment,rock mass deformation on the downstream sidewall was larger than 125mm and the shearing deformation of the shear zone was 60–70 mm.These preset replacement tunnels can reduce not only the unloading and relaxation of rock masses but also the maximum shearing deformation of the shear zone by 10–20 mm.The predictions by numerical simulation were in good agreement with the monitoring results.The proposed tunnel-replacement scheme can not only restrain the shear zone deformation but also enhance the safety of surrounding rocks and concrete tunnels.This design procedure offers a good reference for interaction between a big underground cavern and a weak layer zone in the future.
基金Supported by the National Social Science Fund Major Project(24&ZD106)。
文摘By summarizing the characteristics of the global energy structure and China’s energy resource endowment, this study analyzes the historical context and opportunities for China to build an “energy powerhouse”, and proposes pathways and measures for its realization. It is indicated that the energy resource endowment in China is characterized by abundant coal, limited oil and gas, and vast renewable potential, coupled with an energy consumption structure characterized by high coal consumption, low oil and gas consumption, and rapidly growing renewable energy use. The “whole-energy system” approach that integrates multi-energy complementarity, green development, stable supply, smart utilization and carbon neutrality is an effective solution to addressing energy transition and energy independence. To build an “energy powerhouse”, China can follow the approach of the steady and orderly low-carbon development of fossil fuels, the safe and scaled development of new energy, the integrated development of a carbon-neutral “whole-energy system”, and the shared development of the “Belt and Road” energy corridor. The construction of an “energy powerhouse” should follow a “three-phase” strategic pathway: from 2025 to 2030, achieving peak primary energy consumption and “carbon peaking”;from 2031 to 2050, energy production will achieve parity with consumption for the first time, striving for “energy independence”;and from 2051 to 2060, aiming for “carbon neutrality”, and establishing an “energy powerhouse”. Building an “energy powerhouse” will fundamentally safeguard national energy security, advance the achievement of carbon neutrality goals, provide Chinese solutions for global energy transition and green Earth construction, and support the modernization and great rejuvenation of the Chinese nation.
基金Project(2017YFC1501100)supported by the National Key R&D Program of ChinaProjects(51809221,51679158)supported by the National Natural Science Foundation of China。
文摘To investigate the stability of rock mass in high geostress underground powerhouse caverns subjected to excavation,a microseismic(MS)monitoring system was established and the discrete element method(DEM)-based numerical simulation was carried out.The tempo-spatial damage characteristics of rock mass were analyzed.The evolution laws of MS source parameters during the formation of a rock collapse controlled by high geostress and geological structure were investigated.Additionally,a three-dimensional DEM model of the underground powerhouse caverns was built to reveal the deformation characteristics of rock mass.The results indicated that the MS events induced by excavation of high geostress underground powerhouse caverns occurred frequently.The large-stake crown of the main powerhouse was the main damage area.Prior to the rock collapse,the MS event count and accumulated energy release increased rapidly,while the apparent stress sharply increased and then decreased.The amount and proportion of shear and mixed MS events remarkably increased.The maximum displacement was generally located near the spandrel areas.The MS monitoring data and numerical simulation were in good agreement,which can provide significant references for damage evaluation and disaster forecasting in high geostress underground powerhouse caverns.
基金Projects(51809221,51679158)supported by the National Natural Science Foundation of ChinaProject(KFJJ20-06M)supported by the State Key Laboratory of Explosion Science and Technology(Beijing Institute of Technology),China。
文摘Rock mass large deformation in underground powerhouse caverns has been a severe hazard in hydropower engineering in Southwest China.During the development of rock mass large deformation,a sequence of fractures was generated that can be monitored using microseismic(MS)monitoring techniques.Two MS monitoring systems were established in two typical underground powerhouse caverns featuring distinct geostress levels.The MS b-values associated with rock mass large deformation and their temporal variation are analysed.The results showed that the MS bvalue in course of rock mass deformation was less than 1.0 in the underground powerhouse caverns at a high stress level while larger than 1.5 at a low stress level.Prior to the rock mass deformation,the MS b-values derived from both the high-stress and low-stress underground powerhouse caverns show an incremental decrease over 10%within 10 d.The results contribute to understanding the fracturing characteristics of MS sources associated with rock mass large deformation and provide a reference for early warning of rock mass large deformation in underground powerhouse caverns.
基金the support of the National Natural Science Foundation of China (Grant No. 11902210)the Graduate Student’s Research Innovation Foundation of Sichuan University (Grant No. 2018YJSY076)
文摘The stability of the surrounding rocks of large underground powerhouses is always emphasized during the construction process,especially in large-scale underground projects under construction,such as the Baihetan hydropower station in China.According to field investigations,numerical simulations and monitoring data analysis,we present a comparative analysis of the deformation and failure characteristics of the surrounding rocks of underground powerhouses on the left and right banks of the Baihetan hydropower station.The failure characteristics and deformation magnitude of the underground powerhouses on the left and right banks are quite different.Under the disadvantageous condition where the maximum principal stress intersects the axis of the powerhouse at a large angle,the left bank underground powerhouse shows prominent stress-controlled failure characteristics such as spalling,slack collapse and concrete cracking.Although the maximum principal stress is in the favorable condition which intersects the right bank powerhouse at a small angle,the relatively high intermediate principal stress with an angle subvertical to the right bank powerhouse plays an essential role in its deformation and failure,indicating that the influence of high intermediate principal stress cannot be ignored.In addition,structural plane-controlled failure and large deformation are also more evident on the right bank due to the extensive distribution of weak structural planes and complex surrounding rock properties.
基金the valuable support from Yalong River Hydropower Development Company,Ltd.HydroChina Chengdu Engineering Corporation,Ltdthe National Natural Science Foundation of China(Grant Nos.51179014,51579016,51379022,and 51539002)
文摘Based on the analyses of data obtained from the underground powerhouse at Jinping I hydropower station,a comprehensive review of engineering rock mechanics practice in the underground powerhouse is first conducted.The distribution of strata,lithology,and initial geo-stress,the excavation process and corresponding rock mass support measures,the deformation and failure characteristics of the surrounding rock mass,the stress characteristics of anchorage structures in the cavern complex,and numerical simulations of surrounding rock mass stability and anchor support performance are presented.The results indicate that the underground powerhouse of Jinping I hydropower station is characterized by high to extremely high geo-stresses during rock excavation.Excessive surrounding rock mass deformation and high stress of anchorage structures,surrounding rock mass unloading damage,and local cracking failure of surrounding rock masses,etc.,are mainly caused by rock mass excavation.Deformations of surrounding rock masses and stresses in anchorage structures here are larger than those found elsewhere:20%of extensometers in the main powerhouse record more than 50 mm with the maximum at around 250 mm observed in the downstream sidewall of the transformer hall.There are about 25%of the anchor bolts having recorded stresses of more than 200 MPa.Jinping I hydropower plant is the first to have an underground powerhouse construction conducted in host rocks under extremely high geo-stress conditions,with the ratio of rock mass strength to geo-stress of less than 2.0.The results can provide a reference to underground powerhouse construction in similar geological conditions.
基金This work is supported by the National Natural Science Foundation of China(Nos.51979146 and 12102230)the China Three Gorges Corporation Research Program(Nos.WDD/0490,WDD/0578,and BHT/0774)the China Postdoctoral Science Foundation(No.2022M711862).
文摘It is imperative to understand the spatial and temporal coordination deformation mechanism and develop targeted deformation control technologies for high sidewall—bottom transfixion(HSBT)zones to guarantee the stability of rock surrounding underground hydro-powerhouses under complex geological conditions.In this study,the spatial and temporal coordinated deformation control of HSBT zones was addressed from the aspects of the deformation mechanism,failure characteristics,and control requirements,and some coordinated deformation control technologies were proposed.On this basis,a case study was conducted on the deformation control of the HSBT zone of the underground powerhouse at the Wudongde hydropower station,China.The results showed that the relationship between excavation and support,and the mismatch of deformation and support of the surrounding rock mass in the HSBT zone of underground caverns with a large span and high in-situ stress can be appropriately handled.The solution requires proper excavation and construction procedures,fine blasting control,composite and timely support,and real-time monitoring and dynamic feedback.The technologies proposed in this study will ensure the safe,high-quality,and orderly construction of the Baihetan and Wudongde underground caverns,and can be applied to other similar projects.
基金the Science Foundation for Distinguished Young Scholars of Sichuan Province(No.2020JDJQ0011)the National Natural Science Foundation of China(Nos.42177143,51809221,and 52274145)the State Key Laboratory for GeoMechanics and Deep Underground Engineering,China University of Mining&Technology(No.SKLGDUEK2013)。
文摘Based on the underground powerhouse of Shuangjiangkou hydropower station,Octree theory is adopted to define the indices of the microseismic(MS)spatial aggregation degree and the deviation values of MS count and energy.The relationship between the MS multiple parameters and surrounding rock mass instability is established from three aspects:time,space,and strength.Supplemented by the center frequency of the signal evolution characteristics,A fuzzy comprehensive evaluation model and the evolution trend of the MS event center frequency are constructed to quantitatively describe the early warning state of the surrounding rock mass instability.The results show that the multilevel tree structure and voxels generated based on the Octree theory fit relatively well with the set of MS points in threedimensional space.The fuzzy comprehensive evaluation model based on MS spatial aggregation and MS count and energy deviation values enables three-dimensional visualization of the potential damage area and damage extent of the surrounding rock mass.The warning time and potential damage zone quantified are highly consistent with the characteristics of MS precursors,with wide recognition and field investigation results,which fully validate the rationality and applicability of the proposed method.These findings can provide references for the early warning of surrounding rock mass instability in similar underground engineering.
基金support from the National Key R&D Program of China(Grant No.2017YFC1501100)the Science Foundation for Distinguished Young Scholars of Sichuan Province(Grant No.2020JDJQ0011)the National Natural Science Foundation of China(Grant No.42177143).
文摘A high-precision microseismic(MS)monitoring system was built to monitor surrounding rock microfractures in the underground powerhouse on the left bank of Shuangjiangkou Hydropower Station.The surrounding rock damage area with spatiotemporal clustering of MS activities was studied for qualitative analysis of the damage mechanism of surrounding rock microfractures,based on the source parameters of MS events.The surrounding rock microfracture scale characterized by the source radius of MS events was considered to establish the constitutive relation.MS information was imported into the model for numerical analysis using fast Lagrangian analysis of continuain 3 dimensions(FLAC^(3D)).The results indicated that the numerical simulation results considering MS damage can better reflect the actual situation of the field.The surrounding rock microfractures mainly showed mixed failure characteristics.Shear failures appeared in localized areas while the fracture scale of sections from K0e33 m to K0e15 m on the vault was large.The deformation increment caused by microfracture damage in the shallow surrounding rock of the top arch accounted for 10%e13%,and the stress decrement in the surrounding rock caused by microfracture damage accounted for about 10%.
基金National Natural Science Foundation of China (No.50679009)Foundations for Young Teachers in Dalian University of Technology(No.893219)
文摘With the increase of capacity and size of the hydro-generator unit, the spiral case becomes a more super-giant hydraulic structure with very high HD value, where H and D denote water head and maximum intake diameter of spiral case, respectively. Due to the induced lower stiffness by the more giant size and adverse operation conditions, dynamic performances of the powerhouse and the supporting structure for the giant units have become more important and attracted much attention. If the manner of steel spiral case embedded directly in concrete is adopted, on some locations of the concrete surrounding the spiral case, distributed and concentrated cracks will emerge due to high tensile stress. Although the concrete is reinforced well to control the maximum crack width, definitely these cracks will reduce the local and entire stiffness of the powerhouse. Under dynamic loads such as hydraulic forces including water pressure pulsation in flow passage acting on the structure, effect of the cracks on the dynamic characteristics of the local members and entire structure needs to be evaluated. However, research on this subject is few in hydroelectric engineering. In this paper, Three-Gorge Project was taken as an example to evaluate effect of such cracks on natural frequencies and the vibration responses of the powerhouse under hydraulic and earthquake forces in detail. Results show that cracks only reduce the local structural stiffness greatly but have little effect on the entire powerhouse especially the superstructure; vibrations of powerhouse with cracks in concrete surrounding the spiral case are still under the design limits. Results in this paper have been verified by practice of Three-Gorge Project.
基金Supported by the National Key Technology R&D Program of China (2008BAB29B01)
文摘The complicated rock structures and the stability of surrounding rocks of the underground powerhouse were the key rock mechanical problems in Shuibuya hydropower station.In order to overcome the related rock mechanical problems encountered during its construction,a comprehensive research was carried out for the underground powerhouse in Shuibuya hydropower station based on a detailed geological survey.It covers the investigations on the initial in-situ stress distribution features,rock mechanical properties,engineering rock mass classifications by different methods,numerical modeling for stability and support analysis,proper measures for rock excavation and support.The results show that the rock excavations of the underground powerhouse under the given geological conditions can be controlled effectively.Some measures,suggested by the designers,are proved to be rational and effective.These measures mainly consist of:(1) the soft rock replacements by concrete in local area below the crane beam,(2) the shotcrete and reinforcement by rock bolts and anchor cables in surrounding rocks,and (3) 2 m concrete placement on the rock bench between adjacent tailrace tubes.The engineering practice shows that the treated surrounding rocks have a good overall stability.The deformation behaviors observed by safety equipments are within the designing limits.The research conclusions on the related rock mechanical problems,prior to the underground powerhouse excavations,are reliable.
基金Supported by National Natural Science Foundation of China(No.50539010)
文摘In this paper,three different modeling ranges were selected in the structural analysis for a hydropower house.The analysis was carried out using ABAQUS 6.6.The modeling range has a remarkable effect on finite element method(FEM) calculation result at the middle position of typical cross-sections where the concrete is relatively thin,and at the region close to turbine floor.If the ventilation barrel,floor slabs and columns above turbine floor are excluded from FEM model,the maximum rise difference of pedestal structure increases by about 24% compared with that of the whole model.It is indicated that different modeling ranges indeed affect FEM calculation result,and the structure above turbine floor in the FEM model should be included.
基金Supported by Natural Science Fund ation for Major Research Plan of China (No.90815019)National Natural Science Foundation of China (No.50879053)National Key Project of Scientific and Technical Supporting Programs Funded by Ministry of Science and Technology of China (No.2006BAB04A13)
文摘Under forced ventilation,the dust diffusion of underground powerhouse construction is investigated using a 3D high Reynolds number k-ε model.The interfacial momentum transfers and the wall roughness in the wall function are considered.Ventilation in the third layer of underground powerhouse of Xiangjiaba hydropower station is used as a case.The geometric structure has a decisive effect on the airflow distribution.It is concluded that the dust concentration decreases gradually with the increase of the ventilation time.However,iso-concentration curves have the same tendency after 1 800 s.The dust concentration meets the ventilation and dust-prevention health standard after 2 300 s.The prediction by the present model is confirmed by the experimental measurement by Nakayama.
文摘This year, 70 years after the founding of New China, the Chinese nation has made a historic leap from standing up to becoming rich and strong. In this great change, the textile industry has achieved all-round and deep-seated development, playing an increasingly important role in serv- ing the overall strategic situation of the country.
文摘Recent breakthrough achievements such as the launch of DeepSeek's revolutionary AI models and the collection of samples from the far side of the moon are indicators of just how far China has developed in science and technology.
基金The National Social Science Fund of China(21&ZD093)The National Natural Science Foundation of China(41871109)The AgriculturalScience and Technology Innovation Program(CAAS-CSAERD-202402,10-IAED-RC-09-2024,10-IAED-04-2024)。
文摘The construction of an agricultural powerhouse in China is confronted with the practical dilemma of relying mainly on small-scale farming and weak agricultural competitiveness,so an exploration of feasible paths for building an agricultural powerhouse is urgently needed.This study constructed indicator systems that reflect the level of agricultural development from three dimensions:resource endowment,output status,and urban-rural relations.On this basis,the gap between China and the world’s representative agricultural powers was analyzed,and the evolutionary characteristics of agricultural policies in the European Union,Japan,and the United States were explored,leading to relevant policy implications.This analysis found that the superficial problems of China's agricultural development lie in the relative scarcity of good resource conditions and insufficient modernization,while the underlying crux lies in the lack of obvious industrial competitive advantages,which is especially reflected in the lack of coordinated development between industry,agriculture,and urban-rural areas.The European Union,Japan,and the United States all focus on improving the international competitiveness of agriculture based on their comparative advantages,attach importance to the comprehensive development of rural areas,and have effectively constructed coordinated industry-agriculture and urban-rural relations,all of which have promoted the comprehensive development of agriculture.China’s construction of an agricultural powerhouse should be based on its national conditions and the general laws governing the building a world-class agricultural powerhouse.The strategy should include focusing on building a diversified food supply system to ensure food security;focusing on the modernization of agricultural science and technology,which will promote the process of agricultural modernization;promoting the development of the entire agricultural industry chain,which will enhance the competitiveness and risk resistance of the agricultural industry;accelerating public policy reform and continuing to promote urban-rural integration.
文摘China retained its position as the world's second-largest film market in 2023,showcasing a steady upward trajectory in revenue and audience engagement.Meanwhile,the Indian film industry,renowned for its glitz,vibrancy,and drama,has earned global repute as one of the largest cinema hubs in the world.
