To study the heights of the caved zone and water-conducting fracture zone in backfill mining,the failure mechanism of strata during backfill mining was analyzed,and a method for determining the heights of the two zone...To study the heights of the caved zone and water-conducting fracture zone in backfill mining,the failure mechanism of strata during backfill mining was analyzed,and a method for determining the heights of the two zones was proposed based on key strata theory.The movement and failure regularity of the strata above the backfilling panel were revealed through numerical simulation.Considering the geologic conditions of the CT101 backfilling panel,the height of the fracture zone was determined using the proposed method along with empirical calculation,numerical simulation,and borehole detection.The results of the new calculation method were similar to in situ measurements.The traditional empirical formula,which is based on the equivalent mining height model,resulted in large errors during calculation.The findings indicate the reliability of the new method and demonstrate its significance for creating reference data for related studies.展开更多
Aimed at determining the appropriate caving–mining ratio for fully mechanized mining of 20 m thick coal seam, this research investigated the effects of caving–mining ratio on the flow fields of coal and waste rocks,...Aimed at determining the appropriate caving–mining ratio for fully mechanized mining of 20 m thick coal seam, this research investigated the effects of caving–mining ratio on the flow fields of coal and waste rocks, amount of cyclically caved coal and top coal loss by means of numerical modeling. The research was based on the geological conditions of panel 8102 in Tashan coal mine. The results indicated the loose coal and waste rocks formed an elliptical zone around the drawpoint. The ellipse enlarged with decreasing caving–mining ratio. And its long axis inclined to the gob gradually became vertical and facilitating the caving and recovery of top coal. The top coal loss showed a cyclical variation; and the loss cycle was shortened with the decreasing in caving–mining ratio. Moreover, the mean squared error(MSE) of the amount of cyclically caved coal went up with increasing caving–mining ratio, indicating a growing imbalance of amount of cyclically caved coal, which could impede the coordinated mining and caving operations. Finally it was found that a caving–mining ratio of 1:2.51 should be reasonable for the conditions.展开更多
Coal mine underground reservoirs help address the severe water imbalance in ecologically fragile mining regions of western China,but evaluating their storage capacity remains challenging due to the coupled effects of ...Coal mine underground reservoirs help address the severe water imbalance in ecologically fragile mining regions of western China,but evaluating their storage capacity remains challenging due to the coupled effects of gangue deformation,saturation,and goaf geometry.This study investigates the deformation and void evolution of fragmented gangue with varying lithologies,particle sizes,and water contents through an independent-developed testing system and theoretical model.A planar micro-unit model and a three-dimensional spatial structure model are proposed to quantify the storage coefficient and total reservoir capacity of underground water storage structures.These models incorporate the effects of stratified lithologies,saturation-induced softening,and spatially distributed stress conditions.The methodology is applied to the underground reservoir in Chahasu coal mine,and the results show that under increasing stress,storage coefficients decline exponentially,with pronounced differences between single-and double-lithology structures.The storage coefficient in the spatial model demonstrate greater resilience to stress concentration compared to planar models,and further analysis identifies critical thresholds in roof fracture distances and stress-recovery times affecting long-term storage performance.This research provides a comprehensive framework for evaluating underground reservoir storage potential,offering theoretical support and engineering guidance for the sustainable utilization of mine water.展开更多
Tumor recurrence, the Gordian knot of liver transplantation for malignancies, may be attributed to many parameters. The technique of the “classical” recipient hepatectomy is believed to be one of the potential reaso...Tumor recurrence, the Gordian knot of liver transplantation for malignancies, may be attributed to many parameters. The technique of the “classical” recipient hepatectomy is believed to be one of the potential reasons to cause tumor evasion because of the possible increase of circulating tumor cells, thus leading to an increased recurrent rate. On this background, the no-touch oncological recipient hepatectomy technique has been developed. A comprehensive review of the development and the key surgical steps of the no-touch recipient hepatectomy is presented. This technique might improve clinical outcomes, especially for those recipients who are at a high risk for tumor recurrence. Multicenter prospective studies should be set up to further validate the prognostic role of this technique in patients with liver cancer treated with liver transplantation.展开更多
Due to the influence of karst cave development and route selection,the location relationship between concealed karst cave and tunnel is more random.In order to explore the influence rule of karst cave location on the ...Due to the influence of karst cave development and route selection,the location relationship between concealed karst cave and tunnel is more random.In order to explore the influence rule of karst cave location on the minimum safe thickness of water-proof rock mass,a simplified calculation model of water-proof rock mass thickness when the karst cave is located at any location around the tunnel is established,and the influence of multiple factors on the overall stability of water-proof rock mass is considered.Based on the cusp catastrophe theory,the analytical expressions for the safety thickness of waterproof rock mass are derived.Based on the finite difference principle,the analytical expressions of the safety thickness of water-proof rock mass are verified.In order to improve the application range of the analytical formula derived in this paper,the analytical formula is optimized based on the instability principle differences between the simplified calculation model and the elastic compressive bar.The research results show that the necessary condition solution is more applicable and much safer than the sufficient condition solution.Tectonic stress,rock beam length and karst cave water pressure are significantly positively correlated with the safe thickness of the waterproof rock mass.The calculated results of the semioptimized formula and the unoptimized formula are constant values,independent of the karst cave location.While the calculated results of the fully optimized formula are variable values,correlated with the karst cave location,the thickness of the waterproof rock mass gradually decreases as the karst cave location moves from the top of the tunnel to the bottom of the tunnel.The unoptimized formula does not consider the influence of the lateral force of the rock beam,and is not suitable for the working condition with large lateral force,the calculation results of the semi-optimized formula and the fully optimized formula are not very different and are biased to safety,so it can be given priority.展开更多
Cave lion(Panthera spelaea)remains have been described in all the Holarctic domain,however,its records in China are very rare.Here we describe an almost complete cranium from Salawusu,Northern China.Even though the de...Cave lion(Panthera spelaea)remains have been described in all the Holarctic domain,however,its records in China are very rare.Here we describe an almost complete cranium from Salawusu,Northern China.Even though the dentition is largely broken or missing,the cranium shows key characters with clear cave lion affinity,particularly from the basicranium region.These features include wide and short nasals,wide rostrum without post-canine constriction,enlarged ectotympanic,flatted entotympanic,separated stylomastoid foramen and hyoid fossa and medially located hypoglossal foramen.The cranium is larger than the known cranial size range of Beringia cave lion P.spelaea vereshchagini,suggesting that the geographical delimitation of cave lion subspecies may be more complex than previously understood.The coexistence of cave lion with Palaeoloxodon in Salawusu indicates a high plasticity in diet and environmental adaptation for this species.展开更多
In Southwestern China,the development of karst landforms and planation surfaces is closely related to local tectonics,fluvial incision,and base level changes,and climate changes.However,researches on when these karst ...In Southwestern China,the development of karst landforms and planation surfaces is closely related to local tectonics,fluvial incision,and base level changes,and climate changes.However,researches on when these karst landforms and planation surfaces formed and how they evolved along drainage development are scarce.Fortunately,horizontal caves with numerous fluvial deposits in high karst mountains can be served as time markers in landform evolution.Here we select large horizontal caves to perform studies of geomorphology,sedimentology,and geochronology.Fieldwork revealed that more than 25 km long horizontal cave passages are perched 1500 m higher than the local base level,but filled with several phases of fluvial sediments and breakdown slabs.The first phase of fluvial gravels and related cave drainage was dated back to 6.4 Ma using cosmogenic nuclide burial dating,and the stalagmite covering the cave collapse was dated by the U-Pb method to be older than 1.56 Ma.These results show that the continuous horizontal cave drainage system and the planation surface were developed before the Late Miocene.The lowering process of the base level as a result of the sharp fluvial incision and water level lowering,along with the regional uplift,led to the abandonment of the horizontal cave and the elevated planation surface at the Late Miocene.After that,the phase of cave collapse,thick fluvial sand,and clay sediments in the recharge of cave areas were deposited at around 1.6 Ma and during the Middle Pleistocene,respectively.Subsequently,speleothems were widely deposited on the collapse and clay sediments during the period from 600 to 90 ka,whereas the deposition of cave fluvial sediments terminated suddenly.The tectonic could control the denudation of surface caprocks and the development of karst conduits before the Late Miocene,whereas the river incision acted as the main driver for the base level lowering and the destruction of the horizontal cave drainage at high altitudes.In addition,the rapid incision and retreat of Silurian gorges finally caused the formation of karst mesas in the Middle Pleistocene.展开更多
This paper deals with a new species of the genus Althepus from Baiyan Cave in the Nangunhe National Nature Reserve,Yunnan,China,named Althepus nangunheensis Chen,Zhang&Yang,sp.nov.(♂♀).Detailed descriptions,phot...This paper deals with a new species of the genus Althepus from Baiyan Cave in the Nangunhe National Nature Reserve,Yunnan,China,named Althepus nangunheensis Chen,Zhang&Yang,sp.nov.(♂♀).Detailed descriptions,photos of living specimens,and morphological characteristics,and geographic distribution map of the new species are provided.Type specimens are deposited in the Institute of Entomoceutics Research,Dali University,China(DUIER).展开更多
The study presents the results of over 30,000 numerical analyses on the stability of lava tubes under lunar conditions.The research considered random irregularities in cave geometry and their impact on stability,with ...The study presents the results of over 30,000 numerical analyses on the stability of lava tubes under lunar conditions.The research considered random irregularities in cave geometry and their impact on stability,with a particular focus on the geometric characteristics of identified collapses.We propose a procedure for extracting the collapse areas and integrating it into the stability analysis results.The results were examined to assess the possibility of describing the geometry characteristics of collapses using commonly applied probability density distributions,such as normal or lognormal distribution.Our aim is to facilitate future risk assessment of lunar caves.Such an assessment will be essential prior to robotically exploring caves beneath the lunar surface and can be extended to be used for planetary caves beyond the Moon.Our findings indicate that several collapse characteristics can be represented by unimodal probability density distributions,which could significantly simplify the candidate selection process.Based on our results,we also highlight several key directions for future research and suggested implications related to their future exploration.展开更多
It is commonly accepted that the formation of oil and gas reservoirs in deep-buried strata is almost impossible due to the huge compaction of in-situ crustal stresses.Nevertheless,recent hydrocarbon explorations in th...It is commonly accepted that the formation of oil and gas reservoirs in deep-buried strata is almost impossible due to the huge compaction of in-situ crustal stresses.Nevertheless,recent hydrocarbon explorations in the Tarim Basin have discovered reservoirs at depths exceeding 8 km.The reservoirs exhibit a strong correlation to the strata’s faults and large fractures,yet the precise underlying mechanical mechanism remains obscure.To illuminate how the faults may facilitate the existence of such deep-buried reservoirs,we consider three ideal scenarios involving unconventional hole-crack interactions under remote biaxial compression.Our focus is on the stress concentration of the hole,influenced by the long main cracks.Closed-form compressive stress solutions are obtained based on our simple theoretical models,showing that long cracks significantly reduce the stress concentration of nearby holes.We quantify the reducing effect of the cracks’angle,surface friction,and pressure on the maximum shear and von Mises stresses around a hole,combining with finite element analysis results.The stress shielding effect is qualitatively consistent with the available experimental observations that the deep-buried caves are often located near the faults and large fractures in carbonate strata.Our results will be beneficial for future exploration of superdeep petroleum reservoirs.展开更多
President Xi Jinping calls for preserving and promoting cultural relics and museums to carry forward Chinese civilization.ON May 19,one day after the International Museum Day,Chinese President Xi Jinping visited the L...President Xi Jinping calls for preserving and promoting cultural relics and museums to carry forward Chinese civilization.ON May 19,one day after the International Museum Day,Chinese President Xi Jinping visited the Longmen Grottoes in Luoyang,central China’s Henan Province.With 2,345 caves and alcoves,nearly 110,000 Buddhist statues,over 2,800 inscriptions,and nearly 80 pagodas,the Longmen Grottoes was recognized by UNESCO as the pinnacle of Chinese stone carving art.展开更多
The Dazu Rock Carvings in Chongqing were inscribed on the World Heritage List in 1999.In recent years,the Dazu Rock Carvings have faced environmental challenges such as geological forces,increased precipitation,pollut...The Dazu Rock Carvings in Chongqing were inscribed on the World Heritage List in 1999.In recent years,the Dazu Rock Carvings have faced environmental challenges such as geological forces,increased precipitation,pollution and tourism,which have led to rock deterioration and structural instability.The multi-source monitoring system for the protection of the rock carvings,based on the Internet of Things,includes Global Navigation Satellite System(GNSS)displacement monitoring,static level displacement monitoring,laser rangefinder displacement monitoring,roof pressure sensor monitoring and environmental damage monitoring.This paper analyses data from each sub-monitoring system within the multi-source monitoring system applied to Yuanjue Cave in the Dazu Rock Carvings.Initially,a correlation analysis between climate monitoring data and roof displacement data was carried out to assess the effect of temperature.Based on the results of the analysis,a temperature correction equation for the laser rangefinder was derived to improve the laser rangefinder displacement monitoring system.The improved system was then used to monitor Cave 168,revealing the deformation and erosion patterns of the roof.The research results demonstrate that the multiparameter monitoring system is capable of accurately measuring and analyzing the stability of the Dazu stone carvings,as well as the effects of environmental conditions on them.The use of the Internet of Things(IoT)and real-time data collection to monitor rock deformation and environmental conditions is an innovative application of technology in cultural heritage conservation.Interpretation of the monitoring system and statistical correlation analysis of temperature and laser rangefinder data highlight the thoroughness of the methodology in this paper and its relevance to sustainable mountain development.In the future,multi-source monitoring systems will have a broader application in the conservation of other UNESCO World Heritage Sites.展开更多
To address issues such as inefficient top-coal drawing,challenges in simultaneously mining and drawing,and the need for intelligent control in extra-thick coal seams,this study examines the principles of top-coal draw...To address issues such as inefficient top-coal drawing,challenges in simultaneously mining and drawing,and the need for intelligent control in extra-thick coal seams,this study examines the principles of top-coal drawing and explores automation and intelligent equipment solutions within the framework of the group coal drawing method.Numerical simulations were performed to investigate the impact of the Number of Drawing Openings(NDO)and rounds on top-coal recovery,coal draw-ing efficiency,and Top Coal Loss(TCL)mechanism.Subsequently,considering the recovery and coal drawing efficiency and by introducing the instantaneous gangue content and cumulative gangue content in simulations,the top-coal recovery,gangue content,and coal loss distribution when considering excessive coal drawing were analyzed.This established a foun-dation for determining the optimal NDO and shutdown timing.Finally,the key technical principle and automated control of a shock vibration and hyperspectral fusion recognition device were detailed,and an intelligent coal drawing control method based on this technology was developed.This technology enabled the precise control of the instantaneous gangue content(35%)during coal drawing.The top-coal recovery at the Tashan Mine 8222 working face increased by 14.78%,and the gangue content was controlled at~9%,consistent with the numerical simulation results.Thus,the reliability of the numerical simulation results was confirmed to a certain extent.Meanwhile,the single-group drawing method significantly enhanced the production capacity of the 8222 working face,achieving an annual output of 15 million tons.展开更多
Colloids are prevalent in nuclear waste repositories,with bentonite colloids posing an uncontrollable risk factor for nuclide migration processes.In this study,static adsorption experiments were coupled with dynamic s...Colloids are prevalent in nuclear waste repositories,with bentonite colloids posing an uncontrollable risk factor for nuclide migration processes.In this study,static adsorption experiments were coupled with dynamic shower experiments to comprehensively investigate the influence of bentonite colloids on Sr^(2+)migration in granite,considering adsorption capacity.Bentonite colloids have a considerably greater adsorption capacity than both bentonite and granite,with a maximum adsorption of 30.303 mg/g.The adsorption behavior of bentonite colloids on Sr^(2+)is well described by the Langmuir isotherm and pseudo-second-order kinetic models,indicating that a single-layer chemical adsorption process is controlled by the site activation energy.The adsorbed Sr^(2+)is unevenly distributed on the colloids,and the adsorption mechanism may involve ion exchange with Ca.Bentonite colloids exhibit superior adsorption in neutral environments.The cations in groundwater inhibit Sr^(2+)adsorption,and the inhibition efficacy decreases in the order Fe^(3+)>Ca^(2+)>Mg^(2+)>K^(+).The presence of bentonite colloids in a granite column slightly influences the retention of Sr^(2+)in the column while markedly reducing the Sr^(2+)penetration time from 70 h to 18 h.However,the coexistence of Co^(2+),Ni^(2+),and Cs^(+)in a multinuclide system weakens the ability of the colloids to promote Sr^(2+)migration.In comigration of colloid and multinuclide systems,the adsorption of nuclides by bentonite colloids causes the nuclide migration speed to decrease in the order Sr^(2+)>Cs^(+)>Ni^(2+)>Co^(2+).This study provides insights into Sr^(2+)migration in cave repositories for low-and medium-level radioactive waste.展开更多
Caves located in the buried hill reservoir of granite bedrock in Bongor Basin,Chad,are excessively small and cannot be identifi ed in conventional refl ection wave imaging profi les because their refl ection character...Caves located in the buried hill reservoir of granite bedrock in Bongor Basin,Chad,are excessively small and cannot be identifi ed in conventional refl ection wave imaging profi les because their refl ection characteristics are suppressed by the strong refl ection of the weathering crust at the top of the buried hill.In contrast to refl ection wave imaging,which refl ects the refl ection characteristics of continuous interfaces,scattered wave imaging refl ects the reflection characteristics of discontinuous geological bodies.Scattering waves can be produced in the presence of discontinuous points,such as karst caves,fractures,and stratum vanishing points.Scattering imaging can accurately provide the location of discontinuous abnormal bodies,highlight the seismic reflection characteristics of caves with weak reflections,and eliminate continuous strong reflections to strengthen the ability of seismic data to distinguish discontinuous geological bodies and solve the inability of seismic data from conventional poststack refl ection wave imaging to identify small caves in buried hills.Three-parameter wavelet spectral decomposition technology is used to depict the boundary of caves accurately in accordance with the strong energy spectral characteristics of caves in the section of the scattering imaging seismic data of the granite bedrock buried hill reservoir.Compared with the attributes extracted from conventional refl ection wave poststack seismic data,those acquired from scattering imaging bodies are more reliable and consistent with the actual location of caves on boreholes and have higher resolution.For connected wells,the attributes extracted from the conventional poststack seismic data can only predict whether caves are developed,whereas those calculated from scattering imaging can not only predict whether caves are present but also refl ects the degree of cave development.On the plane,the attributes obtained from scattering imaging calculation are more consistent with the geological law of cave development.On the basis of this fi nding and in accordance with the results of the three-parameter wavelet spectral decomposition of scattering imaging seismic data,the degree of cave development is classifi ed,and the favorable location for reservoir development in the study area is identifi ed.This solution provides an eff ective way to improve the exploration accuracy of cave-type granite buried hill reservoirs.展开更多
基金Supported by the National Key R&D Program(2018YFC0604501).
文摘To study the heights of the caved zone and water-conducting fracture zone in backfill mining,the failure mechanism of strata during backfill mining was analyzed,and a method for determining the heights of the two zones was proposed based on key strata theory.The movement and failure regularity of the strata above the backfilling panel were revealed through numerical simulation.Considering the geologic conditions of the CT101 backfilling panel,the height of the fracture zone was determined using the proposed method along with empirical calculation,numerical simulation,and borehole detection.The results of the new calculation method were similar to in situ measurements.The traditional empirical formula,which is based on the equivalent mining height model,resulted in large errors during calculation.The findings indicate the reliability of the new method and demonstrate its significance for creating reference data for related studies.
基金provided by the independent research subject of State Key Laboratory of Coal Resources and Mine Safety of China University of Mining and Technology (No. SKLCRSM12X03)the Scientific Research and Innovation Project for College Graduates in Jiangsu (No. CXZZ13_0947)
文摘Aimed at determining the appropriate caving–mining ratio for fully mechanized mining of 20 m thick coal seam, this research investigated the effects of caving–mining ratio on the flow fields of coal and waste rocks, amount of cyclically caved coal and top coal loss by means of numerical modeling. The research was based on the geological conditions of panel 8102 in Tashan coal mine. The results indicated the loose coal and waste rocks formed an elliptical zone around the drawpoint. The ellipse enlarged with decreasing caving–mining ratio. And its long axis inclined to the gob gradually became vertical and facilitating the caving and recovery of top coal. The top coal loss showed a cyclical variation; and the loss cycle was shortened with the decreasing in caving–mining ratio. Moreover, the mean squared error(MSE) of the amount of cyclically caved coal went up with increasing caving–mining ratio, indicating a growing imbalance of amount of cyclically caved coal, which could impede the coordinated mining and caving operations. Finally it was found that a caving–mining ratio of 1:2.51 should be reasonable for the conditions.
基金supported by the National Natural Science Foundation of China(Nos.52404153,52504157 and 52504156)the Natural Science Foundation of Jiangsu Province(No.BK20241649).
文摘Coal mine underground reservoirs help address the severe water imbalance in ecologically fragile mining regions of western China,but evaluating their storage capacity remains challenging due to the coupled effects of gangue deformation,saturation,and goaf geometry.This study investigates the deformation and void evolution of fragmented gangue with varying lithologies,particle sizes,and water contents through an independent-developed testing system and theoretical model.A planar micro-unit model and a three-dimensional spatial structure model are proposed to quantify the storage coefficient and total reservoir capacity of underground water storage structures.These models incorporate the effects of stratified lithologies,saturation-induced softening,and spatially distributed stress conditions.The methodology is applied to the underground reservoir in Chahasu coal mine,and the results show that under increasing stress,storage coefficients decline exponentially,with pronounced differences between single-and double-lithology structures.The storage coefficient in the spatial model demonstrate greater resilience to stress concentration compared to planar models,and further analysis identifies critical thresholds in roof fracture distances and stress-recovery times affecting long-term storage performance.This research provides a comprehensive framework for evaluating underground reservoir storage potential,offering theoretical support and engineering guidance for the sustainable utilization of mine water.
基金supported in part by grants from National Nat-ural Science Foundation of China (82200726 and U23A20451)Key Program of the National Natural Science Foundation of China (81930016)National Key Research and Development Program of China (2021YFA1100500)。
文摘Tumor recurrence, the Gordian knot of liver transplantation for malignancies, may be attributed to many parameters. The technique of the “classical” recipient hepatectomy is believed to be one of the potential reasons to cause tumor evasion because of the possible increase of circulating tumor cells, thus leading to an increased recurrent rate. On this background, the no-touch oncological recipient hepatectomy technique has been developed. A comprehensive review of the development and the key surgical steps of the no-touch recipient hepatectomy is presented. This technique might improve clinical outcomes, especially for those recipients who are at a high risk for tumor recurrence. Multicenter prospective studies should be set up to further validate the prognostic role of this technique in patients with liver cancer treated with liver transplantation.
基金jointly funded by the guangxi Science and Technology Base and Talent Project(AD23026104)the Key Research and Development Program Project in Guangxi(AB23026121)。
文摘Due to the influence of karst cave development and route selection,the location relationship between concealed karst cave and tunnel is more random.In order to explore the influence rule of karst cave location on the minimum safe thickness of water-proof rock mass,a simplified calculation model of water-proof rock mass thickness when the karst cave is located at any location around the tunnel is established,and the influence of multiple factors on the overall stability of water-proof rock mass is considered.Based on the cusp catastrophe theory,the analytical expressions for the safety thickness of waterproof rock mass are derived.Based on the finite difference principle,the analytical expressions of the safety thickness of water-proof rock mass are verified.In order to improve the application range of the analytical formula derived in this paper,the analytical formula is optimized based on the instability principle differences between the simplified calculation model and the elastic compressive bar.The research results show that the necessary condition solution is more applicable and much safer than the sufficient condition solution.Tectonic stress,rock beam length and karst cave water pressure are significantly positively correlated with the safe thickness of the waterproof rock mass.The calculated results of the semioptimized formula and the unoptimized formula are constant values,independent of the karst cave location.While the calculated results of the fully optimized formula are variable values,correlated with the karst cave location,the thickness of the waterproof rock mass gradually decreases as the karst cave location moves from the top of the tunnel to the bottom of the tunnel.The unoptimized formula does not consider the influence of the lateral force of the rock beam,and is not suitable for the working condition with large lateral force,the calculation results of the semi-optimized formula and the fully optimized formula are not very different and are biased to safety,so it can be given priority.
文摘Cave lion(Panthera spelaea)remains have been described in all the Holarctic domain,however,its records in China are very rare.Here we describe an almost complete cranium from Salawusu,Northern China.Even though the dentition is largely broken or missing,the cranium shows key characters with clear cave lion affinity,particularly from the basicranium region.These features include wide and short nasals,wide rostrum without post-canine constriction,enlarged ectotympanic,flatted entotympanic,separated stylomastoid foramen and hyoid fossa and medially located hypoglossal foramen.The cranium is larger than the known cranial size range of Beringia cave lion P.spelaea vereshchagini,suggesting that the geographical delimitation of cave lion subspecies may be more complex than previously understood.The coexistence of cave lion with Palaeoloxodon in Salawusu indicates a high plasticity in diet and environmental adaptation for this species.
基金supported by the foundation of the Institute of Karst Geology,Chinese Academy of Geological Sciences(Nos.201317,2014005,2014034,2016011)National Natural Science Foundation of China(No.41270226)。
文摘In Southwestern China,the development of karst landforms and planation surfaces is closely related to local tectonics,fluvial incision,and base level changes,and climate changes.However,researches on when these karst landforms and planation surfaces formed and how they evolved along drainage development are scarce.Fortunately,horizontal caves with numerous fluvial deposits in high karst mountains can be served as time markers in landform evolution.Here we select large horizontal caves to perform studies of geomorphology,sedimentology,and geochronology.Fieldwork revealed that more than 25 km long horizontal cave passages are perched 1500 m higher than the local base level,but filled with several phases of fluvial sediments and breakdown slabs.The first phase of fluvial gravels and related cave drainage was dated back to 6.4 Ma using cosmogenic nuclide burial dating,and the stalagmite covering the cave collapse was dated by the U-Pb method to be older than 1.56 Ma.These results show that the continuous horizontal cave drainage system and the planation surface were developed before the Late Miocene.The lowering process of the base level as a result of the sharp fluvial incision and water level lowering,along with the regional uplift,led to the abandonment of the horizontal cave and the elevated planation surface at the Late Miocene.After that,the phase of cave collapse,thick fluvial sand,and clay sediments in the recharge of cave areas were deposited at around 1.6 Ma and during the Middle Pleistocene,respectively.Subsequently,speleothems were widely deposited on the collapse and clay sediments during the period from 600 to 90 ka,whereas the deposition of cave fluvial sediments terminated suddenly.The tectonic could control the denudation of surface caprocks and the development of karst conduits before the Late Miocene,whereas the river incision acted as the main driver for the base level lowering and the destruction of the horizontal cave drainage at high altitudes.In addition,the rapid incision and retreat of Silurian gorges finally caused the formation of karst mesas in the Middle Pleistocene.
基金the National Natural Science Foundation of China(32160113)the Yunnan Provincial Key Projects for Basic Research(202401AS070027)for their generous funding support.
文摘This paper deals with a new species of the genus Althepus from Baiyan Cave in the Nangunhe National Nature Reserve,Yunnan,China,named Althepus nangunheensis Chen,Zhang&Yang,sp.nov.(♂♀).Detailed descriptions,photos of living specimens,and morphological characteristics,and geographic distribution map of the new species are provided.Type specimens are deposited in the Institute of Entomoceutics Research,Dali University,China(DUIER).
基金The work was performed based on the research project no.2023/51/D/ST10/01956,financed by the National Science Center,Poland.
文摘The study presents the results of over 30,000 numerical analyses on the stability of lava tubes under lunar conditions.The research considered random irregularities in cave geometry and their impact on stability,with a particular focus on the geometric characteristics of identified collapses.We propose a procedure for extracting the collapse areas and integrating it into the stability analysis results.The results were examined to assess the possibility of describing the geometry characteristics of collapses using commonly applied probability density distributions,such as normal or lognormal distribution.Our aim is to facilitate future risk assessment of lunar caves.Such an assessment will be essential prior to robotically exploring caves beneath the lunar surface and can be extended to be used for planetary caves beyond the Moon.Our findings indicate that several collapse characteristics can be represented by unimodal probability density distributions,which could significantly simplify the candidate selection process.Based on our results,we also highlight several key directions for future research and suggested implications related to their future exploration.
基金supported by the National Natural Science Foundation of China(Grant No.11988102)the Natural Science Foundation of Guangdong Province(Grant No.2019A1515011909)the Science Challenge Project(Grant No.TZ2018002).
文摘It is commonly accepted that the formation of oil and gas reservoirs in deep-buried strata is almost impossible due to the huge compaction of in-situ crustal stresses.Nevertheless,recent hydrocarbon explorations in the Tarim Basin have discovered reservoirs at depths exceeding 8 km.The reservoirs exhibit a strong correlation to the strata’s faults and large fractures,yet the precise underlying mechanical mechanism remains obscure.To illuminate how the faults may facilitate the existence of such deep-buried reservoirs,we consider three ideal scenarios involving unconventional hole-crack interactions under remote biaxial compression.Our focus is on the stress concentration of the hole,influenced by the long main cracks.Closed-form compressive stress solutions are obtained based on our simple theoretical models,showing that long cracks significantly reduce the stress concentration of nearby holes.We quantify the reducing effect of the cracks’angle,surface friction,and pressure on the maximum shear and von Mises stresses around a hole,combining with finite element analysis results.The stress shielding effect is qualitatively consistent with the available experimental observations that the deep-buried caves are often located near the faults and large fractures in carbonate strata.Our results will be beneficial for future exploration of superdeep petroleum reservoirs.
文摘President Xi Jinping calls for preserving and promoting cultural relics and museums to carry forward Chinese civilization.ON May 19,one day after the International Museum Day,Chinese President Xi Jinping visited the Longmen Grottoes in Luoyang,central China’s Henan Province.With 2,345 caves and alcoves,nearly 110,000 Buddhist statues,over 2,800 inscriptions,and nearly 80 pagodas,the Longmen Grottoes was recognized by UNESCO as the pinnacle of Chinese stone carving art.
基金financial support from the National Natural Science Foundation of China(No.42377154)。
文摘The Dazu Rock Carvings in Chongqing were inscribed on the World Heritage List in 1999.In recent years,the Dazu Rock Carvings have faced environmental challenges such as geological forces,increased precipitation,pollution and tourism,which have led to rock deterioration and structural instability.The multi-source monitoring system for the protection of the rock carvings,based on the Internet of Things,includes Global Navigation Satellite System(GNSS)displacement monitoring,static level displacement monitoring,laser rangefinder displacement monitoring,roof pressure sensor monitoring and environmental damage monitoring.This paper analyses data from each sub-monitoring system within the multi-source monitoring system applied to Yuanjue Cave in the Dazu Rock Carvings.Initially,a correlation analysis between climate monitoring data and roof displacement data was carried out to assess the effect of temperature.Based on the results of the analysis,a temperature correction equation for the laser rangefinder was derived to improve the laser rangefinder displacement monitoring system.The improved system was then used to monitor Cave 168,revealing the deformation and erosion patterns of the roof.The research results demonstrate that the multiparameter monitoring system is capable of accurately measuring and analyzing the stability of the Dazu stone carvings,as well as the effects of environmental conditions on them.The use of the Internet of Things(IoT)and real-time data collection to monitor rock deformation and environmental conditions is an innovative application of technology in cultural heritage conservation.Interpretation of the monitoring system and statistical correlation analysis of temperature and laser rangefinder data highlight the thoroughness of the methodology in this paper and its relevance to sustainable mountain development.In the future,multi-source monitoring systems will have a broader application in the conservation of other UNESCO World Heritage Sites.
基金the Fundamental Research Funds for the Central Universities(2023YQTD02)National Key R&D Program of China(2023YFC2907501)。
文摘To address issues such as inefficient top-coal drawing,challenges in simultaneously mining and drawing,and the need for intelligent control in extra-thick coal seams,this study examines the principles of top-coal drawing and explores automation and intelligent equipment solutions within the framework of the group coal drawing method.Numerical simulations were performed to investigate the impact of the Number of Drawing Openings(NDO)and rounds on top-coal recovery,coal draw-ing efficiency,and Top Coal Loss(TCL)mechanism.Subsequently,considering the recovery and coal drawing efficiency and by introducing the instantaneous gangue content and cumulative gangue content in simulations,the top-coal recovery,gangue content,and coal loss distribution when considering excessive coal drawing were analyzed.This established a foun-dation for determining the optimal NDO and shutdown timing.Finally,the key technical principle and automated control of a shock vibration and hyperspectral fusion recognition device were detailed,and an intelligent coal drawing control method based on this technology was developed.This technology enabled the precise control of the instantaneous gangue content(35%)during coal drawing.The top-coal recovery at the Tashan Mine 8222 working face increased by 14.78%,and the gangue content was controlled at~9%,consistent with the numerical simulation results.Thus,the reliability of the numerical simulation results was confirmed to a certain extent.Meanwhile,the single-group drawing method significantly enhanced the production capacity of the 8222 working face,achieving an annual output of 15 million tons.
基金supported by the General Project of the National Natural Science Foundation of China(No.42377413).
文摘Colloids are prevalent in nuclear waste repositories,with bentonite colloids posing an uncontrollable risk factor for nuclide migration processes.In this study,static adsorption experiments were coupled with dynamic shower experiments to comprehensively investigate the influence of bentonite colloids on Sr^(2+)migration in granite,considering adsorption capacity.Bentonite colloids have a considerably greater adsorption capacity than both bentonite and granite,with a maximum adsorption of 30.303 mg/g.The adsorption behavior of bentonite colloids on Sr^(2+)is well described by the Langmuir isotherm and pseudo-second-order kinetic models,indicating that a single-layer chemical adsorption process is controlled by the site activation energy.The adsorbed Sr^(2+)is unevenly distributed on the colloids,and the adsorption mechanism may involve ion exchange with Ca.Bentonite colloids exhibit superior adsorption in neutral environments.The cations in groundwater inhibit Sr^(2+)adsorption,and the inhibition efficacy decreases in the order Fe^(3+)>Ca^(2+)>Mg^(2+)>K^(+).The presence of bentonite colloids in a granite column slightly influences the retention of Sr^(2+)in the column while markedly reducing the Sr^(2+)penetration time from 70 h to 18 h.However,the coexistence of Co^(2+),Ni^(2+),and Cs^(+)in a multinuclide system weakens the ability of the colloids to promote Sr^(2+)migration.In comigration of colloid and multinuclide systems,the adsorption of nuclides by bentonite colloids causes the nuclide migration speed to decrease in the order Sr^(2+)>Cs^(+)>Ni^(2+)>Co^(2+).This study provides insights into Sr^(2+)migration in cave repositories for low-and medium-level radioactive waste.
文摘Caves located in the buried hill reservoir of granite bedrock in Bongor Basin,Chad,are excessively small and cannot be identifi ed in conventional refl ection wave imaging profi les because their refl ection characteristics are suppressed by the strong refl ection of the weathering crust at the top of the buried hill.In contrast to refl ection wave imaging,which refl ects the refl ection characteristics of continuous interfaces,scattered wave imaging refl ects the reflection characteristics of discontinuous geological bodies.Scattering waves can be produced in the presence of discontinuous points,such as karst caves,fractures,and stratum vanishing points.Scattering imaging can accurately provide the location of discontinuous abnormal bodies,highlight the seismic reflection characteristics of caves with weak reflections,and eliminate continuous strong reflections to strengthen the ability of seismic data to distinguish discontinuous geological bodies and solve the inability of seismic data from conventional poststack refl ection wave imaging to identify small caves in buried hills.Three-parameter wavelet spectral decomposition technology is used to depict the boundary of caves accurately in accordance with the strong energy spectral characteristics of caves in the section of the scattering imaging seismic data of the granite bedrock buried hill reservoir.Compared with the attributes extracted from conventional refl ection wave poststack seismic data,those acquired from scattering imaging bodies are more reliable and consistent with the actual location of caves on boreholes and have higher resolution.For connected wells,the attributes extracted from the conventional poststack seismic data can only predict whether caves are developed,whereas those calculated from scattering imaging can not only predict whether caves are present but also refl ects the degree of cave development.On the plane,the attributes obtained from scattering imaging calculation are more consistent with the geological law of cave development.On the basis of this fi nding and in accordance with the results of the three-parameter wavelet spectral decomposition of scattering imaging seismic data,the degree of cave development is classifi ed,and the favorable location for reservoir development in the study area is identifi ed.This solution provides an eff ective way to improve the exploration accuracy of cave-type granite buried hill reservoirs.
