In 2018,a catastrophic high-altitude landslide occurred at Baige,located within the tectonic suture zone of the Upper Jinsha River.The failure mechanism of this event remains poorly understood.This study aims to eluci...In 2018,a catastrophic high-altitude landslide occurred at Baige,located within the tectonic suture zone of the Upper Jinsha River.The failure mechanism of this event remains poorly understood.This study aims to elucidate the deformation characteristics and failure mechanism of the Baige landslide by employing a comprehensive methodology,including field geological surveys,analysis of historical remote sensing imagery,high-density electrical resistivity surveys,and advanced displacement monitoring.Additionally,the physical modeling experiments were conducted to replicate the unique failure modes.The findings propose a novel perspective on the failure mechanism of the Baige landslide,which involves two critical stages:first,the brittle shear zone bypasses and fails at the lower locked segment,and second,the failure of the upper locked segment,combined with the shear zone's impact on the lower locked segment,triggers overall slope instability.Physical modeling experiments revealed a transition from initial acceleration to a rapid acceleration phase,particularly marked by a significant increase in velocity following the failure of the upper locked segment.The intensity of acoustic emission signals was found to correlate with the failure of the locked segments and the state of particle collisions post-failure.It offers new insights into the failure mechanisms of tectonic mélange belt large-scale landslides in suture zones,contributing to the broader field of landslide research.展开更多
The impulse waves induced by large-reservoir landslides can be characterized by a low Froude number.However,systematic research on predictive models specifically targeting the initial primary wave is lacking.Taking th...The impulse waves induced by large-reservoir landslides can be characterized by a low Froude number.However,systematic research on predictive models specifically targeting the initial primary wave is lacking.Taking the Shuipingzi 1#landslide that occurred in the Baihetan Reservoir area of the Jinsha River in China as an engineering example,this study established a large-scale physical model(with dimensions of 30 m×29 m×3.5 m at a scale of 1:150)and conducted scaled experiments on 3D landslide-induced impulse waves.During the process in which a sliding mass displaced and compressed a body of water to generate waves,the maximum initial wave amplitude was found to be positively correlated with the sliding velocity and the volume of the landslide.With the increase in the water depth,the wave amplitude initially increased and then decreased.The duration of pressure exertion by the sliding mass at its maximum velocity directly correlated with an elevated wave amplitude.Based on the theories of low-amplitude waves and energy conservation,while considering the energy conversion efficiency,a predictive model for the initial wave amplitude was derived.This model could fit and validate the functions of wavelength and wave velocity.The accuracy of the initial wave amplitude was verified using physical experiment data,with a prediction accuracy for the maximum initial wave amplitude reaching 90%.The conversion efficiency(η)directly determined the accuracy of the estimation formula.Under clear conditions for landslide-induced impulse wave generation,estimating the value ofηthrough analogy cases was feasible.This study has derived the landslide-induced impulse waves amplitude prediction formula from the standpoints of wave theory and energy conservation,with greater consideration given to the intrinsic characteristics in the formation process of landslide-induced impulse waves,thereby enhancing the applicability and extensibility of the formula.This can facilitate the development of empirical estimation methods for landslide-induced impulse waves toward universality.展开更多
The western fault zone of the South China Sea is a strike-slip fault system and consists of four typical strike-slip faults. It is the western border of the South China Sea. The formation of the system is due to the e...The western fault zone of the South China Sea is a strike-slip fault system and consists of four typical strike-slip faults. It is the western border of the South China Sea. The formation of the system is due to the extrusion of Indo - China Peninsula caused by the collision of India with Tibet and the spreading of the South China Sea in Cenozoic. There are five episodes of tectonic movement along this fault zone, which plays an important role in the Cenozoic evolution of the South China Sea. By the physical modeling experiments, it can be seen the strike-slip fault undergoes the sinistral and dextral movement due to the relative movement velocity change between the South China Sea block and the Indo - China block. The fault zone controls the evolution of the pull basins locating in the west of the South China Sea.展开更多
Beishan Rock Carvings in Chongqing,a renowned cultural heritage site in China,flourished during the Tang and Song dynasties and are often referred to as the“Stone Carving Art Museum of the Tang and Song Dynasties.”C...Beishan Rock Carvings in Chongqing,a renowned cultural heritage site in China,flourished during the Tang and Song dynasties and are often referred to as the“Stone Carving Art Museum of the Tang and Song Dynasties.”Cave 168 is a key component of the Beishan Rock Carvings.At present,several through-going cracks have developed in the roof of Cave 168,severely compromising the structural stability of the grotto.The early internal steel plate supports have suffered severe corrosion and can no longer provide effective reinforcement.In addition,the presence of steel columns obstructs visitor access and negatively affects the viewing experience.A new reinforcement method is urgently needed.Therefore,studying the deformation patterns of the structure is of critical importance.This study analyzes the stratigraphic parameters and fracture distribution of Cave 168,considering key influencing factors such as rainfall,self-weight,and the overlying Quaternary soil.On-site monitoring and physical model experiments were conducted to evaluate the changes in roof crack width and displacement before and after reinforcement with negative Poisson's ratio(NPR)anchor cables.The results reveal that the roof of Cave 168 contains several through-going cracks and numerous microcracks,which serve as infiltration channels for surface water.These accelerate the softening of the mudstone and pose a significant threat to the cave's structural safety.During the experiment,the main change in the crack exhibited a“semi-archshaped”propagation pattern.In the first ten minutes,as the rock transitioned from dry to moist conditions,a slight crack closure was observed.As rainfall continued,crack propagation accelerated.After rainfall ceased,crack width remained stable over a short period.Under NPR anchor support,the influence of rainfall on roof settlement was effectively mitigated,ensuring the safety and stability of the roof.The NPR anchors successfully limited the roof settlement to within 0.3 mm and provided effective control over both total and differential settlement.These findings offer valuable insights into the application of NPR anchor cables in the conservation of grotto heritage structures.展开更多
Plant roots improve the stability of collapsing walls and prevent their collapse;they are thus important for controlling the degree of Benggang erosion in southern China.The vegetation species on the collapsing walls ...Plant roots improve the stability of collapsing walls and prevent their collapse;they are thus important for controlling the degree of Benggang erosion in southern China.The vegetation species on the collapsing walls are diverse,and the interaction of the root systems with soil affects the stability of the collapsing walls.Most recent studies have only examined the effects of single plants.In order to investigate the effects of the roots of different vegetation types on the shear strength of soil in collapsing walls and their interaction mechanisms of action,this study was conducted using the roots of the herb Dicranopteris dichotoma and the shrub Melastoma candidum.A direct shear test of indoor remodeled soil was carried out by varying water content(15%,25%)and herb to shrub root ratio(100:0,75:25,50:50,25:75,and 0:100).The results showed that the shear strength(96.09 kPa)and cohesion(49.26 kPa)of root-containing soil were significantly higher than plain soil(91.77 kPa,42.17 kPa),and the highest values were obtained when herb to shrub root ratio was 100:0(113.27 kPa,62.85 kPa).Here,tensile tests and scanning electron microscopy revealed that the tensile force and tensile strength of the roots of Dicranopteris dichotoma were weaker but effective for maintaining soil stability because of their abundance roots,which could achieve a stronger bond to soil.Simultaneously,herbaceous roots have a small diameter,the Root Area Ratio(RAR)of the roots is larger under the same mass condition,which can better contact with soil and the mechanical properties of roots are fully utilized.Therefore,the soil shear strength is higher and can better resist external damage when herbaceous roots accounts for a larger proportion.The results of this research have implications for the selection and allocation of ecological measures for prevention and control of Benggang.展开更多
The instability and failure of high rock slopes have a significant impact on the safe mining operations.Therefore,revealing the instability mechanism of high rock slopes is of great research significance.This paper ai...The instability and failure of high rock slopes have a significant impact on the safe mining operations.Therefore,revealing the instability mechanism of high rock slopes is of great research significance.This paper aims to reveal the instability mechanism of high rock slopes through physical model tests and numerical simulations.Taking the slope failure on the west side of Pit 1 of Husab Uranium Mine in Namibia in 2021 as the research background,a physical model of the high rock slope of Husab Uranium Mine was established by combining with on-site geological data.The experimental system was monitored by a GoPro camera,a CCD camera,and strain sensors.The damage evolution process of the high rock slope model was analyzed,and numerical simulation verification was carried out using Flac 3D software.Thus,the instability mechanism of the slope failure in this open-pit mine was revealed from multiple perspectives.The results show that the instability mechanism of the high rock slope was determined through the evolution of the displacement field and strain field during the model excavation process,as well as the deformation characteristics of the images at the time of instability and failure.The slope deformation process can be divided into four stages:the initial inter-layer dislocation stage,the crack generation stage,the crack propagation stage,and the crack penetration and failure stage.The results of the model experiment and numerical simulation confirm the consistency between the failure mode of the model slope and the actual slope failure on-site,providing guidance for the prevention and control projects of similar types of mine failures.展开更多
To address the problems of difficult leveling and poor stability of hill crawler tractors,an attitude adjustment device based on a parallel four-bar mechanism was designed,and the mechanical reasons for the sideslip i...To address the problems of difficult leveling and poor stability of hill crawler tractors,an attitude adjustment device based on a parallel four-bar mechanism was designed,and the mechanical reasons for the sideslip instability of hill crawler tractors were analyzed.On this basis,a posture adjustment mechanism based on a parallel four-bar mechanism was proposed,and the structure of the complete attitude adjustment device was designed.To ensure that this device meets the strength requirements during operation,a mechanical analysis of the key components(active rocker and slave rocker)was carried out to accommodate the load during leveling.Based on ANSYS software,a finite element simulation analysis was used to determine the maximum stress position of the active and slave rockers.Finally,to verify the accuracy of the above simulation analysis results and determine the influence rules of the lateral slope angle,longitudinal slope angle and loading quality on the abovementioned maximum stress,a physical model test bench of the attitude adjustment device was built.An orthogonal regression experiment was carried out with the maximum stresses of the active and slave rockers as the test indices.The experimental data were analyzed by Design-Expert 10 software,and the results show that the order of the primary and secondary factors influencing the maximum stress of the active rocker was the loading mass,lateral slope angle and longitudinal slope angle.The order of the factors influencing the maximum stress of the slave rocker was the longitudinal slope angle,lateral slope angle and loading mass.The active and slave rockers meet the strength requirements.This work provides technical support for the production of hill crawler tractor physical prototypes.展开更多
This paper proposes a structure combined by baffle and submerged breakwater （abbreviated to SCBSB in the following texts）. Such a combined structure is conducive to the water exchange in the harbor, and has strong c...This paper proposes a structure combined by baffle and submerged breakwater （abbreviated to SCBSB in the following texts）. Such a combined structure is conducive to the water exchange in the harbor, and has strong capability on wave dissipation. Our paper focuses on the discussion of two typical structures, i.e., the submerged baffle and rectangular breakwater combined with the upper baffle respectively, which are named as SCBSB 1 and SCBSB2 for short. The eigenfunction method corrected by experimental results is used to investigate the wave dissipation characteristics. It shows that the calculated results agree well with the experimental data and the minimum value of the wave transmission coefficient can be obtained when the distance between the front and rear structures is from 1/4 to 1/2 of the incident wave length.展开更多
In order to improve rib stability,failure criteria and instability mode of a thick coal seam with inter-band rock layer are analysed in this study.A three-dimensional mechanical model is established for the rib by con...In order to improve rib stability,failure criteria and instability mode of a thick coal seam with inter-band rock layer are analysed in this study.A three-dimensional mechanical model is established for the rib by considering the rock layer.A safety factor is defined foy the rib,and it is observed that the safety factor exhibits a positive correlation with the thickness and strength of the inter-band rock.A calculation method for determining critical parameters of the rock layer is presented to ensure the rib stability.It is revealed that incomplete propagation of the fracture at the hard rock constitutes a fundamental prerequisite for ensuring the rib stability.The influence of the position of the inter-band rock in the coal seam on failure mechanism of the rib was thoroughly investigated by developing a series of physical models for the rib at the face area.The best position for the inter-band rock in the coal seam is at a height of 1.5 m away from the roof line,which tends to provide a good stability state for the rib.For different inter-band rock positions,two ways of controlling rib by increasing supports stiffness and flexible grouting reinforcement are proposed.展开更多
Phyllite fragments are essential for accumulating and generating talus slope at the toes of hillslopes,however,how they are linked to slope failure remains unknown.This paper reports the directional arrangement of phy...Phyllite fragments are essential for accumulating and generating talus slope at the toes of hillslopes,however,how they are linked to slope failure remains unknown.This paper reports the directional arrangement of phyllite fragments(DAPF)in phyllite talus slope at the eastern margin of the Tibetan Plateau.Field investigation,mathematical statistics and model experiments were performed in order to systematically understand the influencing factors,which include fragment shape,flat ratio,dip angle(α),and fine particle content(c).The results show that the quadrilateral fragmentgenerates a similar imbricate structure more easily than the triangular and rod fragments in the phyllite talus slope.Additionally,the flat phyllite fragments easily accumulate as imbricated structures on the phyllitetalus slope.When the dip angle(α)is in the range of 20°–30°,the minimum orientation ratio(P)is more than 50%,which means thatthe DAPF phenomenon is more obviousin the phyllite talus slope.For the fine particle content(c)at the same dip angle(α),the minimum orientation ratio(P)is 54%,and the minimum orientation ratio(P)correlates positively with the fine particle content(c).Therefore,compared with the homogeneous talusslope,the phyllite talusslopedisplays a special DAPF phenomenon.This study provides a valuable reference and presents novel knowledgefor risk assessment and engineering design against the phyllite talus slope failure mechanism.展开更多
Based on the characteristics of injection-production units in fractured-vuggy carbonate reservoirs,nine groups of experiments were designed and performed to analyze the interference characteristics and their influenci...Based on the characteristics of injection-production units in fractured-vuggy carbonate reservoirs,nine groups of experiments were designed and performed to analyze the interference characteristics and their influencing factors during water flooding.Based on percolation theory,an inversion model for simulating waterflooding interferences was proposed to study the influence laws of different factors on interference characteristics.The results show that well spacing,permeability ratio,cave size,and cave location all affect the interference characteristics of water flooding.When the cave is located in high permeability fractures,or in the small well spacing direction,or close to the producer in an injection-production unit,the effects of water flooding are much better.When the large cave is located in the high-permeability or small well spacing direction,the well in the direction with lower permeability or smaller well spacing will see water breakthrough earlier.When the cave is in the higher permeability direction and the reserves between the water injector and producer differ greatly,the conductivity differences in different injection-production directions are favorable for water flooding.When the injection-production well pattern is constructed or recombined,it’s better to make the reserves of caves in different injection-production directions proportional to permeability,and inversely proportional to the well spacing.The well close to the cave should be a producer,and the well far from the cave should be an injector.Different ratios of cave reserves to fracture reserves correspond to different optimal well spacings and optimal permeability ratios.Moreover,both optimal well spacing and optimal permeability ratio increase as the ratio of cave reserves to fracture reserves increases.展开更多
Fishing boats are usually anchored side by side in the harbor because of the small structural size and poor resistance to wind and waves.A series of physical model experiments are conducted to investigate the motion c...Fishing boats are usually anchored side by side in the harbor because of the small structural size and poor resistance to wind and waves.A series of physical model experiments are conducted to investigate the motion characteristics of multiple fishing boats that are moored together.A decay test in calm water is conducted to study the natural period and damping coefficients.Regular wave experiments are performed to analyze the roll motion response of each boat for four modes(different numbers of boats side-by-side).The results indicate that the“natural period”of each boat for the mode of multi-boats especially three or four boats,is slightly smaller than that of a single boat,whereas the damping coefficient is visibly larger than that of a single boat.The maximum roll angle of each boat does not appear at the same time under a 90°incident wave.Small roll motion energy is generated at low frequencies and high frequencies when multiple boats are moored together.The energy decreases with the increasing wave period.The roll motion responses of each boat in four modes exhibit different trends with the increasing wave frequency.The number of boats and boat position have significant effects on roll motion.展开更多
As an important wave energy converter(WEC),the double-buoy device has advantages of wider energy absorption band and deeper water adaptability,which attract an increasing number of attentions from researchers.This pap...As an important wave energy converter(WEC),the double-buoy device has advantages of wider energy absorption band and deeper water adaptability,which attract an increasing number of attentions from researchers.This paper makes an in-depth study on double-buoy WEC,by means of the combination of model experiment and numerical simulation.The Response Amplitude Operator(RAO)and energy capture of the double-buoy under constant power take-off(PTO)damping are investigated in the model test,while the average power output and capture width ratio(CWR)are calculated by the numerical simulation to analyze the influence of the wave condition,PTO,and the geometry parameters of the device.The AQWA-Fortran united simulation sy stem,including the secondary developme nt of AQWA software coupled with the flowchart of the Fortran code,models a new dynamic system.Various viscous damping and hydraulic friction from WEC system are measured from the experimental results,and these values are added to the equation of motion.As a result,the energy loss is contained in the final numerical model the by united simulation system.Using the developed numerical model,the optimal period of energy capture is identified.The power capture reaches the maximum value under the outer buoy's natural period.The paper gives the peak value of the energy capture under the linear PTO damping force,and calculates the optimal mass ratio of the device.展开更多
Integrating liquid CO_(2)phase transition blasting(LCPTB)technology with hydraulic fracturing(HF)methods can help reduce wellbore damage,create multiple radial fractures,and establish a complex fracture network.This a...Integrating liquid CO_(2)phase transition blasting(LCPTB)technology with hydraulic fracturing(HF)methods can help reduce wellbore damage,create multiple radial fractures,and establish a complex fracture network.This approach significantly increases the recovery efficiency of low-permeability oil and gas fields.Accurately calculating the number of fractures caused by LCPTB is necessary to predict production enhancement effects and optimize subsequent HF designs.However,few studies are reported on large-scale physical model experiments in terms of a method for calculating the fracture number.This study analyzed the initiation and propagation of cracks under LCPTB,derived a calculation formula for crack propagation radius under stress waves,and then proposed a new,fast,and accurate method for calculating the fracture number using the principle of mass conservation.Through ten rock-breaking tests using LCPTB,the study confirmed the effectiveness of the proposed calculation approach and elucidated the variation rule of explosion pressure,rock-breaking scenario,and the impact of varying parameters on fracture number.The results show that the new calculation method is suitable for fracturing technologies with high pressure rates.Recommendations include enlarging the diameter of the fracturing tube and increasing the liquid CO_(2) mass in the tube to enhance fracture effectiveness.Moreover,the method can be applied to other fracturing technologies,such as explosive fracturing(EF)within HF formations,indicating its broader applicability and potential impact on optimizing unconventional resource extraction technologies.展开更多
In recent years,offshore wind turbines have rap-idly developed,and many pile foundations installed earlier are now approaching decommissioning.Thus,the efficient removal of pile foundations has become a critical issue...In recent years,offshore wind turbines have rap-idly developed,and many pile foundations installed earlier are now approaching decommissioning.Thus,the efficient removal of pile foundations has become a critical issue for the sustainable development of offshore wind energy.To ad-dress this issue,this paper systematically investigates three methods for the recovery of pile foundations using physical model experiments:water injection+lifting,air injection+lifting,and air retention+water injection.The experimental results show that the water injection+lifting method exhibits remarkable advantages in recovering large-diameter and in-clined pile foundations;however,realigning inclined piles during recovery remains challenging,and a risk of pile over-turning exists.The air injection+lifting method proves ef-fective for realigning inclined piles but presents a risk of air expulsion failure,which may affect the continuity and stabil-ity of the recovery process.By contrast,the air retention+water injection method combines the characteristics of water injection and air injection techniques,effectively avoiding air expulsion failure and exhibiting pronounced displacement jumps during pile uplift.These findings provide a valuable reference for future decommissioning practices of offshore wind pile foundations,offer important engineering applica-tion value,and contribute positively to the sustainable devel-opment of the offshore wind industry.展开更多
The hydrodynamic lifting force acting on a gate with high head is one of the key factors concerning the safety and reliability of gates. The lifting force is closely related to hydrodynamic pressure, and generally, is...The hydrodynamic lifting force acting on a gate with high head is one of the key factors concerning the safety and reliability of gates. The lifting force is closely related to hydrodynamic pressure, and generally, is obtained through the model test. This work presents a method of numerical simulation based on the VOF method for the flow and FEM for the structure of a gate to investigate this kind of the lifting force. The physical model experiments were conducted about the hydrodynamic pressure and the lifting force to verify the numerical results. The comparisons of those two methods show that the maximum relative error is smaller than 11.40 % and the method presented in this paper is feasible and could be used in the designs of hydropower projects.展开更多
Surface vortex behavior in front of the tunnel intake was investigated in this paper.The critical submergence of vortex was discussed based on the concept of 'critical spherical sink surface'(CSSS).The vortex ...Surface vortex behavior in front of the tunnel intake was investigated in this paper.The critical submergence of vortex was discussed based on the concept of 'critical spherical sink surface'(CSSS).The vortex formation and evolution at the tunnel intake were analyzed based on the theory of CSSS considering the effect of circulation.A theory was proposed to explain the surface vortex.The theoretical development was verified by the physical model experiments of Xiluodu hydropower station.The radial velocity and vortex circulation were considered as the main factors that influence the formation and evolution of surface vortex.Finally,an anti-vortex intake configuration was proposed to weaken the air-core vortex in front of the tunnel intakes of the hydraulic structures.展开更多
基金supported by the National Major Scientific Instruments and Equipment Development Projects of China(No.41827808)the Major Program of the National Natural Science Foundation of China(No.42090055)Supported by Science and Technology Projects of Xizang Autonomous Region,China(No.XZ202402ZD0001)。
文摘In 2018,a catastrophic high-altitude landslide occurred at Baige,located within the tectonic suture zone of the Upper Jinsha River.The failure mechanism of this event remains poorly understood.This study aims to elucidate the deformation characteristics and failure mechanism of the Baige landslide by employing a comprehensive methodology,including field geological surveys,analysis of historical remote sensing imagery,high-density electrical resistivity surveys,and advanced displacement monitoring.Additionally,the physical modeling experiments were conducted to replicate the unique failure modes.The findings propose a novel perspective on the failure mechanism of the Baige landslide,which involves two critical stages:first,the brittle shear zone bypasses and fails at the lower locked segment,and second,the failure of the upper locked segment,combined with the shear zone's impact on the lower locked segment,triggers overall slope instability.Physical modeling experiments revealed a transition from initial acceleration to a rapid acceleration phase,particularly marked by a significant increase in velocity following the failure of the upper locked segment.The intensity of acoustic emission signals was found to correlate with the failure of the locked segments and the state of particle collisions post-failure.It offers new insights into the failure mechanisms of tectonic mélange belt large-scale landslides in suture zones,contributing to the broader field of landslide research.
基金The authors would like thank LI Renjiang and HU Bin from the China Three Gorges Corporation for providing many valuable suggestions for the establishment of the physical models.This work was supported by the National Natural Science Foundation of China(No.U23A2045)the China Three Gorges Corporation(YM(BHT)/(22)022)the Scientific Research Project of Chongqing Municipal Bureau of Planning and Natural Resources(Evaluation and Reinforcement Technology of Surge Disaster Caused by High and Steep Dangerous Rocks in Chongqing Reservoir Area of the Three Gorges Project,KJ-2023046).
文摘The impulse waves induced by large-reservoir landslides can be characterized by a low Froude number.However,systematic research on predictive models specifically targeting the initial primary wave is lacking.Taking the Shuipingzi 1#landslide that occurred in the Baihetan Reservoir area of the Jinsha River in China as an engineering example,this study established a large-scale physical model(with dimensions of 30 m×29 m×3.5 m at a scale of 1:150)and conducted scaled experiments on 3D landslide-induced impulse waves.During the process in which a sliding mass displaced and compressed a body of water to generate waves,the maximum initial wave amplitude was found to be positively correlated with the sliding velocity and the volume of the landslide.With the increase in the water depth,the wave amplitude initially increased and then decreased.The duration of pressure exertion by the sliding mass at its maximum velocity directly correlated with an elevated wave amplitude.Based on the theories of low-amplitude waves and energy conservation,while considering the energy conversion efficiency,a predictive model for the initial wave amplitude was derived.This model could fit and validate the functions of wavelength and wave velocity.The accuracy of the initial wave amplitude was verified using physical experiment data,with a prediction accuracy for the maximum initial wave amplitude reaching 90%.The conversion efficiency(η)directly determined the accuracy of the estimation formula.Under clear conditions for landslide-induced impulse wave generation,estimating the value ofηthrough analogy cases was feasible.This study has derived the landslide-induced impulse waves amplitude prediction formula from the standpoints of wave theory and energy conservation,with greater consideration given to the intrinsic characteristics in the formation process of landslide-induced impulse waves,thereby enhancing the applicability and extensibility of the formula.This can facilitate the development of empirical estimation methods for landslide-induced impulse waves toward universality.
基金Acknowledgements This research was supported by the National Natural Science Foundation of China under contract Nos 40476026 and 40406012, the National Natural Science Foundation of Guangdong Province under contract No. 04001309, and the Key Laboratory of Marginal Sea Geology Foundation of South China Sea Institute of 0ceanology, Chinese Academy of Sciences under contract No. MSGL0510. We are grateful to Yan Pin and Liu Hailing for their generous help in providing seismic profiles.
文摘The western fault zone of the South China Sea is a strike-slip fault system and consists of four typical strike-slip faults. It is the western border of the South China Sea. The formation of the system is due to the extrusion of Indo - China Peninsula caused by the collision of India with Tibet and the spreading of the South China Sea in Cenozoic. There are five episodes of tectonic movement along this fault zone, which plays an important role in the Cenozoic evolution of the South China Sea. By the physical modeling experiments, it can be seen the strike-slip fault undergoes the sinistral and dextral movement due to the relative movement velocity change between the South China Sea block and the Indo - China block. The fault zone controls the evolution of the pull basins locating in the west of the South China Sea.
文摘Beishan Rock Carvings in Chongqing,a renowned cultural heritage site in China,flourished during the Tang and Song dynasties and are often referred to as the“Stone Carving Art Museum of the Tang and Song Dynasties.”Cave 168 is a key component of the Beishan Rock Carvings.At present,several through-going cracks have developed in the roof of Cave 168,severely compromising the structural stability of the grotto.The early internal steel plate supports have suffered severe corrosion and can no longer provide effective reinforcement.In addition,the presence of steel columns obstructs visitor access and negatively affects the viewing experience.A new reinforcement method is urgently needed.Therefore,studying the deformation patterns of the structure is of critical importance.This study analyzes the stratigraphic parameters and fracture distribution of Cave 168,considering key influencing factors such as rainfall,self-weight,and the overlying Quaternary soil.On-site monitoring and physical model experiments were conducted to evaluate the changes in roof crack width and displacement before and after reinforcement with negative Poisson's ratio(NPR)anchor cables.The results reveal that the roof of Cave 168 contains several through-going cracks and numerous microcracks,which serve as infiltration channels for surface water.These accelerate the softening of the mudstone and pose a significant threat to the cave's structural safety.During the experiment,the main change in the crack exhibited a“semi-archshaped”propagation pattern.In the first ten minutes,as the rock transitioned from dry to moist conditions,a slight crack closure was observed.As rainfall continued,crack propagation accelerated.After rainfall ceased,crack width remained stable over a short period.Under NPR anchor support,the influence of rainfall on roof settlement was effectively mitigated,ensuring the safety and stability of the roof.The NPR anchors successfully limited the roof settlement to within 0.3 mm and provided effective control over both total and differential settlement.These findings offer valuable insights into the application of NPR anchor cables in the conservation of grotto heritage structures.
基金supported by the Water Conservancy Science and Technology Project of Fujian Province(KJG21009A)the Significant Science and Technology Projects of the Ministry of Water Resources(SKS-2022073)the Scientific and Technological Innovation Project of Natural Resources in Fujian Province(KY-070000-04-2022-013)。
文摘Plant roots improve the stability of collapsing walls and prevent their collapse;they are thus important for controlling the degree of Benggang erosion in southern China.The vegetation species on the collapsing walls are diverse,and the interaction of the root systems with soil affects the stability of the collapsing walls.Most recent studies have only examined the effects of single plants.In order to investigate the effects of the roots of different vegetation types on the shear strength of soil in collapsing walls and their interaction mechanisms of action,this study was conducted using the roots of the herb Dicranopteris dichotoma and the shrub Melastoma candidum.A direct shear test of indoor remodeled soil was carried out by varying water content(15%,25%)and herb to shrub root ratio(100:0,75:25,50:50,25:75,and 0:100).The results showed that the shear strength(96.09 kPa)and cohesion(49.26 kPa)of root-containing soil were significantly higher than plain soil(91.77 kPa,42.17 kPa),and the highest values were obtained when herb to shrub root ratio was 100:0(113.27 kPa,62.85 kPa).Here,tensile tests and scanning electron microscopy revealed that the tensile force and tensile strength of the roots of Dicranopteris dichotoma were weaker but effective for maintaining soil stability because of their abundance roots,which could achieve a stronger bond to soil.Simultaneously,herbaceous roots have a small diameter,the Root Area Ratio(RAR)of the roots is larger under the same mass condition,which can better contact with soil and the mechanical properties of roots are fully utilized.Therefore,the soil shear strength is higher and can better resist external damage when herbaceous roots accounts for a larger proportion.The results of this research have implications for the selection and allocation of ecological measures for prevention and control of Benggang.
文摘The instability and failure of high rock slopes have a significant impact on the safe mining operations.Therefore,revealing the instability mechanism of high rock slopes is of great research significance.This paper aims to reveal the instability mechanism of high rock slopes through physical model tests and numerical simulations.Taking the slope failure on the west side of Pit 1 of Husab Uranium Mine in Namibia in 2021 as the research background,a physical model of the high rock slope of Husab Uranium Mine was established by combining with on-site geological data.The experimental system was monitored by a GoPro camera,a CCD camera,and strain sensors.The damage evolution process of the high rock slope model was analyzed,and numerical simulation verification was carried out using Flac 3D software.Thus,the instability mechanism of the slope failure in this open-pit mine was revealed from multiple perspectives.The results show that the instability mechanism of the high rock slope was determined through the evolution of the displacement field and strain field during the model excavation process,as well as the deformation characteristics of the images at the time of instability and failure.The slope deformation process can be divided into four stages:the initial inter-layer dislocation stage,the crack generation stage,the crack propagation stage,and the crack penetration and failure stage.The results of the model experiment and numerical simulation confirm the consistency between the failure mode of the model slope and the actual slope failure on-site,providing guidance for the prevention and control projects of similar types of mine failures.
基金This research was conducted at the College of Mechanical and Electronic Engineering,Northwest A&F University and was supported by the National Key Research and Development Plan Program(2016YFD0700503).
文摘To address the problems of difficult leveling and poor stability of hill crawler tractors,an attitude adjustment device based on a parallel four-bar mechanism was designed,and the mechanical reasons for the sideslip instability of hill crawler tractors were analyzed.On this basis,a posture adjustment mechanism based on a parallel four-bar mechanism was proposed,and the structure of the complete attitude adjustment device was designed.To ensure that this device meets the strength requirements during operation,a mechanical analysis of the key components(active rocker and slave rocker)was carried out to accommodate the load during leveling.Based on ANSYS software,a finite element simulation analysis was used to determine the maximum stress position of the active and slave rockers.Finally,to verify the accuracy of the above simulation analysis results and determine the influence rules of the lateral slope angle,longitudinal slope angle and loading quality on the abovementioned maximum stress,a physical model test bench of the attitude adjustment device was built.An orthogonal regression experiment was carried out with the maximum stresses of the active and slave rockers as the test indices.The experimental data were analyzed by Design-Expert 10 software,and the results show that the order of the primary and secondary factors influencing the maximum stress of the active rocker was the loading mass,lateral slope angle and longitudinal slope angle.The order of the factors influencing the maximum stress of the slave rocker was the longitudinal slope angle,lateral slope angle and loading mass.The active and slave rockers meet the strength requirements.This work provides technical support for the production of hill crawler tractor physical prototypes.
基金financially supported by the National Key R&D Program of China(Grant No.2017YFC0405402)
文摘This paper proposes a structure combined by baffle and submerged breakwater （abbreviated to SCBSB in the following texts）. Such a combined structure is conducive to the water exchange in the harbor, and has strong capability on wave dissipation. Our paper focuses on the discussion of two typical structures, i.e., the submerged baffle and rectangular breakwater combined with the upper baffle respectively, which are named as SCBSB 1 and SCBSB2 for short. The eigenfunction method corrected by experimental results is used to investigate the wave dissipation characteristics. It shows that the calculated results agree well with the experimental data and the minimum value of the wave transmission coefficient can be obtained when the distance between the front and rear structures is from 1/4 to 1/2 of the incident wave length.
基金financial support from the National Key Research and Development Program of China (No.2023YFC2907501)the National Natural Science Foundation of China (No.52374106)the Fundamental Research Funds for the Central Universities (No.2023ZKPYNY01)。
文摘In order to improve rib stability,failure criteria and instability mode of a thick coal seam with inter-band rock layer are analysed in this study.A three-dimensional mechanical model is established for the rib by considering the rock layer.A safety factor is defined foy the rib,and it is observed that the safety factor exhibits a positive correlation with the thickness and strength of the inter-band rock.A calculation method for determining critical parameters of the rock layer is presented to ensure the rib stability.It is revealed that incomplete propagation of the fracture at the hard rock constitutes a fundamental prerequisite for ensuring the rib stability.The influence of the position of the inter-band rock in the coal seam on failure mechanism of the rib was thoroughly investigated by developing a series of physical models for the rib at the face area.The best position for the inter-band rock in the coal seam is at a height of 1.5 m away from the roof line,which tends to provide a good stability state for the rib.For different inter-band rock positions,two ways of controlling rib by increasing supports stiffness and flexible grouting reinforcement are proposed.
基金This study has been supported by the National Natural Science Foundation of China(Grant No.41672295)Science and Technology Project of Department of Transportation of Sichuan Province(Grant No.2015B1-1)+1 种基金Sichuan Provincial Science and Technology Plan Project(Grant No.2017JY0264)Scientific and Technological Research and Development Plan of China Railway Corporation(Grant No.P2018G047).
文摘Phyllite fragments are essential for accumulating and generating talus slope at the toes of hillslopes,however,how they are linked to slope failure remains unknown.This paper reports the directional arrangement of phyllite fragments(DAPF)in phyllite talus slope at the eastern margin of the Tibetan Plateau.Field investigation,mathematical statistics and model experiments were performed in order to systematically understand the influencing factors,which include fragment shape,flat ratio,dip angle(α),and fine particle content(c).The results show that the quadrilateral fragmentgenerates a similar imbricate structure more easily than the triangular and rod fragments in the phyllite talus slope.Additionally,the flat phyllite fragments easily accumulate as imbricated structures on the phyllitetalus slope.When the dip angle(α)is in the range of 20°–30°,the minimum orientation ratio(P)is more than 50%,which means thatthe DAPF phenomenon is more obviousin the phyllite talus slope.For the fine particle content(c)at the same dip angle(α),the minimum orientation ratio(P)is 54%,and the minimum orientation ratio(P)correlates positively with the fine particle content(c).Therefore,compared with the homogeneous talusslope,the phyllite talusslopedisplays a special DAPF phenomenon.This study provides a valuable reference and presents novel knowledgefor risk assessment and engineering design against the phyllite talus slope failure mechanism.
基金Supported by the China National Science and Technology Major Project(2016ZX05014-003-004)
文摘Based on the characteristics of injection-production units in fractured-vuggy carbonate reservoirs,nine groups of experiments were designed and performed to analyze the interference characteristics and their influencing factors during water flooding.Based on percolation theory,an inversion model for simulating waterflooding interferences was proposed to study the influence laws of different factors on interference characteristics.The results show that well spacing,permeability ratio,cave size,and cave location all affect the interference characteristics of water flooding.When the cave is located in high permeability fractures,or in the small well spacing direction,or close to the producer in an injection-production unit,the effects of water flooding are much better.When the large cave is located in the high-permeability or small well spacing direction,the well in the direction with lower permeability or smaller well spacing will see water breakthrough earlier.When the cave is in the higher permeability direction and the reserves between the water injector and producer differ greatly,the conductivity differences in different injection-production directions are favorable for water flooding.When the injection-production well pattern is constructed or recombined,it’s better to make the reserves of caves in different injection-production directions proportional to permeability,and inversely proportional to the well spacing.The well close to the cave should be a producer,and the well far from the cave should be an injector.Different ratios of cave reserves to fracture reserves correspond to different optimal well spacings and optimal permeability ratios.Moreover,both optimal well spacing and optimal permeability ratio increase as the ratio of cave reserves to fracture reserves increases.
基金financially supported by Central Public-interest Scientific Institution Basal Research Fund,CAFS(Grant Nos.2023TD88,2024HY-ZC005,and 2024XT0801).
文摘Fishing boats are usually anchored side by side in the harbor because of the small structural size and poor resistance to wind and waves.A series of physical model experiments are conducted to investigate the motion characteristics of multiple fishing boats that are moored together.A decay test in calm water is conducted to study the natural period and damping coefficients.Regular wave experiments are performed to analyze the roll motion response of each boat for four modes(different numbers of boats side-by-side).The results indicate that the“natural period”of each boat for the mode of multi-boats especially three or four boats,is slightly smaller than that of a single boat,whereas the damping coefficient is visibly larger than that of a single boat.The maximum roll angle of each boat does not appear at the same time under a 90°incident wave.Small roll motion energy is generated at low frequencies and high frequencies when multiple boats are moored together.The energy decreases with the increasing wave period.The roll motion responses of each boat in four modes exhibit different trends with the increasing wave frequency.The number of boats and boat position have significant effects on roll motion.
基金supported by the National Natural Science Foundation of China(Grant Nos.11832009,12172095,and 11902085)the Natural Science Foundation of Guangdong Province(Grant No.2021A1515010320)We are also very grateful to the anonymous reviewers for their contributions.
基金financially supported by the National Key R&D Program of China (Grant No.2018YFB1501900)the Shandong Provincial Natural Science Foundation (Grant No.ZR2021ZD23)+3 种基金Qingdao Postdoctoral Program (Grant No.QDBSH20220201015)the Fundamental Research Funds for the Central Universities (Grant No.202313031)the National Natural Science Foundation of China (Grant No.52071303)the Taishan Scholars Program of Shandong Province (Grant No.ts20190914)。
文摘As an important wave energy converter(WEC),the double-buoy device has advantages of wider energy absorption band and deeper water adaptability,which attract an increasing number of attentions from researchers.This paper makes an in-depth study on double-buoy WEC,by means of the combination of model experiment and numerical simulation.The Response Amplitude Operator(RAO)and energy capture of the double-buoy under constant power take-off(PTO)damping are investigated in the model test,while the average power output and capture width ratio(CWR)are calculated by the numerical simulation to analyze the influence of the wave condition,PTO,and the geometry parameters of the device.The AQWA-Fortran united simulation sy stem,including the secondary developme nt of AQWA software coupled with the flowchart of the Fortran code,models a new dynamic system.Various viscous damping and hydraulic friction from WEC system are measured from the experimental results,and these values are added to the equation of motion.As a result,the energy loss is contained in the final numerical model the by united simulation system.Using the developed numerical model,the optimal period of energy capture is identified.The power capture reaches the maximum value under the outer buoy's natural period.The paper gives the peak value of the energy capture under the linear PTO damping force,and calculates the optimal mass ratio of the device.
基金supported by the National Key R&D Program of China (Grant No.2020YFA0711802).
文摘Integrating liquid CO_(2)phase transition blasting(LCPTB)technology with hydraulic fracturing(HF)methods can help reduce wellbore damage,create multiple radial fractures,and establish a complex fracture network.This approach significantly increases the recovery efficiency of low-permeability oil and gas fields.Accurately calculating the number of fractures caused by LCPTB is necessary to predict production enhancement effects and optimize subsequent HF designs.However,few studies are reported on large-scale physical model experiments in terms of a method for calculating the fracture number.This study analyzed the initiation and propagation of cracks under LCPTB,derived a calculation formula for crack propagation radius under stress waves,and then proposed a new,fast,and accurate method for calculating the fracture number using the principle of mass conservation.Through ten rock-breaking tests using LCPTB,the study confirmed the effectiveness of the proposed calculation approach and elucidated the variation rule of explosion pressure,rock-breaking scenario,and the impact of varying parameters on fracture number.The results show that the new calculation method is suitable for fracturing technologies with high pressure rates.Recommendations include enlarging the diameter of the fracturing tube and increasing the liquid CO_(2) mass in the tube to enhance fracture effectiveness.Moreover,the method can be applied to other fracturing technologies,such as explosive fracturing(EF)within HF formations,indicating its broader applicability and potential impact on optimizing unconventional resource extraction technologies.
基金The National Natural Science Foundation of China (No. 52171274)。
文摘In recent years,offshore wind turbines have rap-idly developed,and many pile foundations installed earlier are now approaching decommissioning.Thus,the efficient removal of pile foundations has become a critical issue for the sustainable development of offshore wind energy.To ad-dress this issue,this paper systematically investigates three methods for the recovery of pile foundations using physical model experiments:water injection+lifting,air injection+lifting,and air retention+water injection.The experimental results show that the water injection+lifting method exhibits remarkable advantages in recovering large-diameter and in-clined pile foundations;however,realigning inclined piles during recovery remains challenging,and a risk of pile over-turning exists.The air injection+lifting method proves ef-fective for realigning inclined piles but presents a risk of air expulsion failure,which may affect the continuity and stabil-ity of the recovery process.By contrast,the air retention+water injection method combines the characteristics of water injection and air injection techniques,effectively avoiding air expulsion failure and exhibiting pronounced displacement jumps during pile uplift.These findings provide a valuable reference for future decommissioning practices of offshore wind pile foundations,offer important engineering applica-tion value,and contribute positively to the sustainable devel-opment of the offshore wind industry.
基金supported by the National Natural Science Foundation of China (Grant No.51079044)
文摘The hydrodynamic lifting force acting on a gate with high head is one of the key factors concerning the safety and reliability of gates. The lifting force is closely related to hydrodynamic pressure, and generally, is obtained through the model test. This work presents a method of numerical simulation based on the VOF method for the flow and FEM for the structure of a gate to investigate this kind of the lifting force. The physical model experiments were conducted about the hydrodynamic pressure and the lifting force to verify the numerical results. The comparisons of those two methods show that the maximum relative error is smaller than 11.40 % and the method presented in this paper is feasible and could be used in the designs of hydropower projects.
基金supported by Tsinghua University Initiative Scientific Research Program (Grant No. 2009THZ07060)the State Key Laboratory of Hydroscience and Engineering of Tsinghua University (Grant No. 2010-TC-2,2009-TC-2)
文摘Surface vortex behavior in front of the tunnel intake was investigated in this paper.The critical submergence of vortex was discussed based on the concept of 'critical spherical sink surface'(CSSS).The vortex formation and evolution at the tunnel intake were analyzed based on the theory of CSSS considering the effect of circulation.A theory was proposed to explain the surface vortex.The theoretical development was verified by the physical model experiments of Xiluodu hydropower station.The radial velocity and vortex circulation were considered as the main factors that influence the formation and evolution of surface vortex.Finally,an anti-vortex intake configuration was proposed to weaken the air-core vortex in front of the tunnel intakes of the hydraulic structures.
