Landslide is the second largest natural disaster after earthquake. It is of significance to study the evolution laws and failure mechanism of landslides based on its surface 3D deformation information. Based on the ra...Landslide is the second largest natural disaster after earthquake. It is of significance to study the evolution laws and failure mechanism of landslides based on its surface 3D deformation information. Based on the rainfall-triggered waste dump instability model test, we studied the failure mechanisms of the waste dump by integrating surface deformation and internal slope stress and proposed novel parameters for identifying landslide stability. We developed a noncontact measurement device, which can obtain millimeter-level 3D deformation data for surface scene in physical model test;Then we developed the similar materials and established a test model for a waste dump. Based on the failure characteristics of slope surface, internal stress of slope body and displacement contours during the whole process, we divided the slope instability process in model test into four stages: rainfall infiltration and surface erosion, shallow sliding, deep sliding, and overall instability. Based on the obtained surface deformation data, we calculated the volume change during slope instability process and compared it with the point displacement on slope surface. The results showed that the volume change can not only reflect the slow-ultra acceleration process of slope failure, but also fully reflect the above four stages and reduce the fluctuations caused by random factors. Finally, this paper proposed two stability identification parameters: the volume change rate above the slip surface and the relative velocity of volume change rate. According to the calculation of these two parameters in model test, they can be used for study the deformation and failure mechanism of slope stability.展开更多
Weak structural plane deformation is responsible for the non-uniform large deformation disasters in layered rock tunnels,resulting in steel arch distortion and secondary lining cracking.In this study,a servo biaxial t...Weak structural plane deformation is responsible for the non-uniform large deformation disasters in layered rock tunnels,resulting in steel arch distortion and secondary lining cracking.In this study,a servo biaxial testing system was employed to conduct physical modeling tests on layered rock tunnels with bedding planes of varying dip angles.The influence of structural anisotropy in layered rocks on the micro displacement and strain field of surrounding rocks was analyzed using digital image correlation(DIC)technology.The spatiotemporal evolution of non-uniform deformation of surrounding rocks was investigated,and numerical simulation was performed to verify the experimental results.The findings indicate that the displacement and strain field of the surrounding layered rocks are all maximized at the horizontal bedding planes and decrease linearly with the increasing dip angle.The failure of the layered surrounding rock with different dip angles occurs and extends along the bedding planes.Compressive strain failure occurs after excavation under high horizontal stress.This study provides significant theoretical support for the analysis,prediction,and control of non-uniform deformation of tunnel surrounding rocks.展开更多
Mitchell's solution is commonly used to determine the required strength of vertically exposed cemented backfill in mines. Developed for drained backfill, Mitchell model assumed a zero friction angle for the backfi...Mitchell's solution is commonly used to determine the required strength of vertically exposed cemented backfill in mines. Developed for drained backfill, Mitchell model assumed a zero friction angle for the backfill. Physical model tests were performed. Good agreements were obtained between the required strengths predicted by the analytical solution and experimental results. However, it is well-known that zero friction angle can only be possible in terms of total stresses when geomaterials are submitted to unconsolidated and undrained conditions. A revisit to Mitchell's physical model tests reveals that both the laboratory tests performed for obtaining the shear strength parameters of the cemented backfill and the box stability tests were conducted under a condition close to undrained condition. This explains well the good agreement between Mitchell's solution and experimental results. Good agreements are equally obtained between Mitchell's experimental results and FLAC3 D numerical modeling of shortterm stability analyses of exposed cemented backfill.展开更多
Estimation of stressses within the tailings slurry during self-weight consolidation is a critical issue for cost-effective barricade design and efficient backfill planning in underground mine stopes.This process requi...Estimation of stressses within the tailings slurry during self-weight consolidation is a critical issue for cost-effective barricade design and efficient backfill planning in underground mine stopes.This process requires a good understanding of self-weight consolidation behaviors of the tailings slurry within practical stopes,where many factors can have significant effects on the consolidation,including drainage condition and cement addition.In this paper,the prepared tailings slurry with different cement contents(0,4.76wt%,and 6.25wt%)was poured into1.2 m-high columns,which allowed three drainage scenarios(undrained,partial lateral drainage near the bottom part,and full lateral drainage boundaries)to investigate the effects of drainage condition and cement addition on the consolidation behavior of the tailings slurry.The consolidation behavior was analyzed in terms of pore water pressure(PWP),settlement,volume of drainage water,and residual water content.The results indicate that increasing the length of the drainage boundary or cement content aids in PWP dissipation.In addition,constructing an efficient drainage boundary was more favorable to PWP dissipation than increasing cement addition.The final stable PWP on the column floor was not sensitive to cement addition.The final settlement of uncemented tailings slurry was independent of drainage conditions,and that of cemented tailings slurry decreased with the increase in cement addition.Notably,more pore water can drain out from the cemented tailings slurry than the uncemented tailings slurry during consolidation.展开更多
This study proposed the newly-designed Pelagic and demersal trawls for the fishing vessels operating in Cameroonian waters in pelagic and demersal fishing grounds. The engineering performances of both trawls were inve...This study proposed the newly-designed Pelagic and demersal trawls for the fishing vessels operating in Cameroonian waters in pelagic and demersal fishing grounds. The engineering performances of both trawls were investigated using physical modelling method and analytical method based on the predicted equations. In a flume tank, a series of physical model tests based on Tauti’s law were performed to investigate the hydrodynamic and geometrical performances of both trawls and to assess the applicability of the analytical methods based on predicted equations. The results showed that in model scale, the working towing speed and door spread for the pelagic trawl were 3.5 knots and 1.85 m, respectively, and for the bottom trawl net they were 4.0 knots and 1.8 m. At that speed and door spread, the drag force, net opening height, and wing-end spread of the pelagic model trawl were 36.73 N, 0.89 m, and 0.86 m, respectively, and the swept area was 0.76 m<sup>2</sup>. Bottom trawl speed and door spread were 30.43 N, 0.38 m, and 0.45 m, respectively, and the swept area was 0.25 m<sup>2</sup>. The maximum difference between the experimental and analytical results of hydrodynamic performances was less than 56.22% and 41.45%, respectively, for pelagic and bottom trawls, the results of the geometrical performances obtained using predicted equations were close to the experimental results in the flume tank with a maximum relative error less than 12.85%. The newly developed pelagic and bottom trawls had advanced engineering performance for high catch efficiency and selectivity and could be used in commercial fishing operations in Cameroonian waters.展开更多
The Fenwei Basin, covered by loess, experiences severe ground fissure disasters. These disasters disrupt the continuity of the loess and pose significant threats to engineering construction safety along transportation...The Fenwei Basin, covered by loess, experiences severe ground fissure disasters. These disasters disrupt the continuity of the loess and pose significant threats to engineering construction safety along transportation routes. Nevertheless, the crack characteristics and the influence zone of ground fissures in the loess layer remain inadequately investigated. To effectively prevent and control ground fissure disasters, physical model tests and the PFC(particle flow code) numerical simulation method are used to investigate the crack mechanism of buried ground fissures in the loess layer. The results show that there are two main cracks in the layer profile, which have a Y-shape morphology. As the dip angle of the preset cracks increased from 60° to 90°, the main deformation zone at the surface gradually shifted towards the footwall. The process of crack propagation from depth to surface is divided into five stages. Additionally, the results confirm the accuracy of the width of the rupture zone d2in the footwall calculated by the cantilever beam theory. These findings can offer theoretical guidance for determining the avoidance distance of ground fissures in loess regions, as well as for implementing disaster prevention and corresponding control measures for various stages of buried ground fissure propagation.展开更多
Motivated by the promising benefits of connected and autonomous vehicles (CAVs) in improving fuelefficiency, mitigating congestion, and enhancing safety, numerous theoretical models have been proposed to plan CAVmulti...Motivated by the promising benefits of connected and autonomous vehicles (CAVs) in improving fuelefficiency, mitigating congestion, and enhancing safety, numerous theoretical models have been proposed to plan CAVmultiple-step trajectories (time–specific speed/location trajectories) to accomplish various operations. However, limitedefforts have been made to develop proper trajectory control techniques to regulate vehicle movements to follow multiplesteptrajectories and test the performance of theoretical trajectory planning models with field experiments. Without aneffective control method, the benefits of theoretical models for CAV trajectory planning can be difficult to harvest. This studyproposes an online learning-based model predictive vehicle trajectory control structure to follow time–specific speed andlocation profiles. Unlike single-step controllers that are dominantly used in the literature, a multiple-step model predictivecontroller is adopted to control the vehicle’s longitudinal movements for higher accuracy. The model predictive controlleroutput (speed) cannot be interpreted by vehicles. A reinforcement learning agent is used to convert the speed value to thevehicle’s direct control variable (i.e., throttle/brake). The reinforcement learning agent captures real-time changes in theoperating environment. This is valuable in saving parameter calibration resources and improving trajectory control accuracy.A line tracking controller keeps vehicles on track. The proposed control structure is tested using reduced-scale robot cars.The adaptivity of the proposed control structure is demonstrated by changing the vehicle load. Then, experiments on twofundamental CAV platoon operations (i.e., platooning and split) show the effectiveness of the proposed trajectory controlstructure in regulating robot movements to follow time-specific reference trajectories.展开更多
To explore the failure mechanism of roadway in layered soft rocks,a physical model with the physically finite elemental slab assemblage(PFESA)method was established.Infrared thermography and a video camera were employ...To explore the failure mechanism of roadway in layered soft rocks,a physical model with the physically finite elemental slab assemblage(PFESA)method was established.Infrared thermography and a video camera were employed to capture thermal responses and deformation.The model results showed that layered soft roadway suffered from large deformation.A three-dimensional distinct element code(3 DEC)model with tetrahedral blocks was built to capture the characteristics of roadway deformation,stress,and cracks.The results showed two failure patterns,layer bending fracture and layer slipping after excavation.The layer bending fracture occurred at positions where the normal direction of layers pointed to the inside of the roadway and the layer slipping occurred in the ribs.Six schemes were proposed to investigate the effects of layered soft rocks.The results showed that the deformation of ribs was obviously larger than that of the roof and floor when the roadway passed through three types of strata.When the roadway was completely in a coal seam,the change of deformation in ribs was not obvious,while the deformation in the roof and floor increased obviously.These results can provide guidance for excavation and support design of roadways in layered soft rocks.展开更多
The waste dump of open-pit coal mine is remade of soil-rock mixture under the action of gravity,dynamic load of transportation equipment and earthquake,etc.By using artificial synthetic transparent soil,the developing...The waste dump of open-pit coal mine is remade of soil-rock mixture under the action of gravity,dynamic load of transportation equipment and earthquake,etc.By using artificial synthetic transparent soil,the developing process and migration law for soil-rock mixture are observed in the remade process.The mixture of fused quartz sand,liquid paraffin and n-tridecane is chosen as the material for synthetic transparent soil which is mixed with liquid paraffin and n-tridecane at a mass ratio of4.4at room temperature of17℃.Physical and mechanical properties of transparent soil are determined by physical test and compared with those in natural sandy soil.The results show that transparent soil and sandy soil have high similarity,in other words,transparent soil can be used for similar simulation experiments of soil-rock mixture.展开更多
The static tests of nine traditional and bird beak square hollow structure(SHS) T-joints with different β values and connection types under axial compression at brace end were carried out. Experimental test schemes, ...The static tests of nine traditional and bird beak square hollow structure(SHS) T-joints with different β values and connection types under axial compression at brace end were carried out. Experimental test schemes, failure modes of specimens, jack load-vertical displacement curves, jack load-deformation of chord and strain intensity distribution curves of joints were presented. The effects of β and connection types on axial compression property of joints were studied. The results show that the ultimate axial compression capacity of common bird beak SHS T-joints and diamond bird beak SHS T-joints is larger than that of traditional SHS T-joint specimens with big values of β. The ultimate axial compression capacity of diamond bird beak SHS T-joints is larger than that of common bird beak SHS T-joints. As β increases, the increase of the ultimate axial compression capacity of diamond bird beak SHS T-joints over that of common bird beak joints grows. The ultimate axial compression capacity and the initial axial stiffness of all kinds of joints increase as β increases, and the initial axial stiffness of the diamond bird beak SHS T-joints is the largest. The ductilities of common bird beak and diamond bird beak SHS T-joints increase as β increases, but the ductility of the traditional SHS T-joints decreases as β increases.展开更多
In this study, we experimentally established the relationship between physical properties, vitrinite reflectance, and microstructure of coal, Taiyuan Formation, Qinshui Basin, China using representative coal samples c...In this study, we experimentally established the relationship between physical properties, vitrinite reflectance, and microstructure of coal, Taiyuan Formation, Qinshui Basin, China using representative coal samples collected from three different mines via the rock mechanics testing system （MTS）. We analyzed the organic macerals, vitrinite reflectance, and microstructure of 11 coal samples using petrography and scanning electron microscopy （SEM）. The experimental results suggest that （1） the elastic parameters can be described by linear equations, （2） both P- and S-wave velocities display anisotropy, （3） the anisotropy negatively correlates with vitrinite reflectance, and （4） the acoustic velocities and Young＇s modulus are negatively correlated with the volume of micropores. The derived empirical equations can be used in the forward modeling and seismic inversion of physical properties of coal for improving the coal-bed methane （CBM） reservoir characterization.展开更多
This study focuses on the evaluation of the differences of physical fitness among soccer players, handball players, and basketball players, and the investigation of the physical fitness structures of those players. Th...This study focuses on the evaluation of the differences of physical fitness among soccer players, handball players, and basketball players, and the investigation of the physical fitness structures of those players. The participants consisted of 160 elite players selected from university teams. Fourteen tests related to health and motor fitness were conducted. The results were subjected to a multivariate analysis of variance (MANOVA) to test the mean vector differences among the three groups of different sport. Nine out of the fourteen tests were of significantly discriminating results regarding to different group, which include side step, abdominal strength, shuttle running, 100m running, pull-up, 1,500m running, trunk flexion, grip strength and broad jump, as determined by a stepwise regression approach. MANOVA showed that there was a significant difference (p<0.001) of the mean vectors of the 9 tests among the three events. Discriminant function analysis showed that three discriminant functions were significant, whose correctness was testified by the classification analysis to be over 80.2%. It is demonstrated that elite handball players are good at agility, elite soccer players are speedy, and successful basketball players apparently possess preeminent muscular strength and endurance.展开更多
The irregularity of jointed network poses a challenge to the determination of field mechanical param-eters of columnar jointed rock mass(CJRM),and a reasonable prediction of deformation and strength characteristics of...The irregularity of jointed network poses a challenge to the determination of field mechanical param-eters of columnar jointed rock mass(CJRM),and a reasonable prediction of deformation and strength characteristics of CJRM is important for engineering construction.The Voronoi diagram and three-dimensional printing technology were used to make an irregular columnar jointed mold,and the irregular CJRM(ICJRM)specimens with different dip directions and dip angles were prepared.Uniaxial compression tests were performed,and the anisotropic strength and deformation characteristics of ICJRM were described.The failure modes and mechanisms were revealed in accordance with the final appearances of the ICJRM specimens.Based on the model test results,the empirical correlations for determining the field deformation and strength parameters of CJRM were derived using the dip angle and modified joint factor.The proposed empirical equations were used in the Baihetan Project,and the calculated mechanical parameters were compared with the field test results and those obtained from the tunneling quality index method.Results showed that the deformation parameters determined by the two proposed methods are all consistent with the field test results,and these two methods can also estimate the strength parameters effectively.展开更多
The failure of slope caused by variations in water levels on both banks of reservoirs is common.Reservoir landslides greatly threaten the safety of reservoir area.Taking large-scale composite deposits located on the L...The failure of slope caused by variations in water levels on both banks of reservoirs is common.Reservoir landslides greatly threaten the safety of reservoir area.Taking large-scale composite deposits located on the Lancang River in Southwest China as a study case,the origin of the deposits was analyzed based on the field investigation and a multi-material model was established in the physical model test.Combined with numerical simulation,the failure mechanism of the composite deposits during reservoir water level variations was studied.The results indicate that the deformation of the large-scale composite deposits is a staged sliding mode during the impoundment process.The first slip deformation is greatly affected by the buoyancy weight-reducing effect,and the permeability of soil and variation in the water level are the factors controlling slope deformation initiation.The high water sensitivity and low permeability of fine grained soil play an important role in the re-deformation of deposits slope.During the impoundment process,the deformation trend of the deposit slope is decreasing,and vertical consolidation of soil and increasing hydrostatic pressure on the slope surface are the main reasons for deformation attenuation.It is considered that the probability of large-scale sliding of the deposits during the impoundment period is low.But the damage caused by local bank collapse of the deposit slope still needs attention.The results of this paper will further improve our understanding of the failure mechanism of composite deposits caused by water level increases and provide guidance for the construction of hydropower stations.展开更多
Introduction:Locomotion is a determinant of intrinsic capacity of older people and can be limited by dysfunction in locomotory organs,characterizing Locomotive Syndrome(LoS).Knowledge on locomotive problems and sarcop...Introduction:Locomotion is a determinant of intrinsic capacity of older people and can be limited by dysfunction in locomotory organs,characterizing Locomotive Syndrome(LoS).Knowledge on locomotive problems and sarcopenia,and their interface with quality of life,in the oldest old in the literature is scarce.Objective:To evaluate the correlation between LoS and sarcopenia and their influence on quality of life in oldest old.Methods:A cross-sectional study of an observational,descriptive and analytical epidemiological survey in independent older adults aged 80 and over from São Paulo,Brazil and who participated in the third wave of the LOCOMOV Project,was carried out.Sociodemographic data,comorbidities,functioning in activities of daily living,physical functioning,quality of life,and presence of sarcopenia and LoS were assessed.The statistical analyses included the Test-for-Comparing-Two-Proportions,Pearson's Correlation Coefficient,the chi-Square test and Student´s t-test.Results:Thirty oldest old with a mean age of 89.1 years were evaluated.The prevalence of LoS was high(53.3%)and correlated significantly with chronic pain(p-value 0.024),worse performance on the SPPB and Gait speed(p-value<0.001).Sarcopenia was not correlated with LoS,but worse quality of life on the physical domain was significantly associated with LoS(p-value<0.001)regardless of the presence of sarcopenia.Conclusions:LoS was highly prevalent among the oldest old studied and negatively impacted their quality of life,regardless of the presence of sarcopenia.展开更多
In this paper, the numerical model of the net cage with the grid mooring system in waves is set up by the lumped mass method and rigid kinematics theory, and then the motion equations of floating system, net system, m...In this paper, the numerical model of the net cage with the grid mooring system in waves is set up by the lumped mass method and rigid kinematics theory, and then the motion equations of floating system, net system, mooring system, and floaters are solved by the Runge-Kutta fifth-order method. For the verification of the numerical model, a series of physical model tests have been carried out. According to the comparisons between the simulated and experimental results, it can be found that the simulated and experimental results agree well in each condition. Then, the effects of submerged depth of grid and direction of incident wave propagation on hydrodynamic behaviors of the net cage are analyzed. According to the simulated results, it can be found that with the increase of submerged depth of grid, the forces acting on mooring lines and bridle lines increase, while the forces on grid lines decrease; the horizontal motion amplitudes of floating collar decrease obviously, while the vertical motion amplitudes of floating collar change little. When the direction of incident wave propagation changes, forces on mooring lines and motion of net cage also change accordingly. When the propagation direction of incident wave changes from 0° to 45°, forces on the main ropes and bridle ropes increase, while the forces on the grid ropes decrease. With the increasing propagation direction of incident wave, the horizontal amplitude of the forces collar decreases, while the vertical amplitude of the floating collar has little variation.展开更多
The goaf may face a series of deformation and settlement problems when the room-pillar mining method is used to excavate ore and pillars in the deep strata.To this end,a deep room-pillar model with two levels was made...The goaf may face a series of deformation and settlement problems when the room-pillar mining method is used to excavate ore and pillars in the deep strata.To this end,a deep room-pillar model with two levels was made,and the pillar recovery was carried out.The instantaneous deformation responses during the pillars recovery and the long-term settlements after the pillar recovery were analyzed.During the pillar recovery,different regions of surrounding rocks suffer from different dynamic disturbances which can be divided into three types,including(I)the combined action of blasting disturbance and unloading disturbance,(II)the sequential action of blasting disturbance and unloading disturbance,and(III)the action of unloading disturbance.After the pillar recovery,the settlement above the first recovering pillar is the largest,which has a traction effect on the settlement in other areas.The settlement process can be divided into two stages,stable displacement stage and unstable displacement stage.When the pillar-room system undergoes the unstable displacement stage,rock spalling and further cascading collapse will occur.展开更多
Many landslides in reservoir areas continuously deform under cyclic water level fluctuations due to reservoir operations. In this paper,a landslide model, developed for a typical colluvial landslide in the Three Gorge...Many landslides in reservoir areas continuously deform under cyclic water level fluctuations due to reservoir operations. In this paper,a landslide model, developed for a typical colluvial landslide in the Three Gorges Reservoir area, is used to study the effect of cyclic water level fluctuations on the landslide. Five cyclic water level fluctuations were implemented in the test, and the fluctuation rate in the last two fluctuations doubled over the first three fluctuations. The pore water pressure and lateral landslide profiles were obtained during the test. A measurement of the landslide soil loss was proposed to quantitatively evaluate the influence of water level fluctuations. The test results show that the first water level rising is most negative to the landslide among the five cycles. The fourth drawdown with a higher drawdown rate caused further large landslide deformation. An increase of the water level drawdown rate is much more unfavorable to the landslide than an increase of the water level rising rate. In addition, the landslide was found to have an adaptive ability to resist subsequent water level fluctuations after undergoing large deformation during a water level fluctuation. The landslide deformation and observations in the field were found to support the test results well.展开更多
By combining the results of prototype observation of flood discharge atomization at the Wujiangdu Hydropower Station, and by adopting the serial model test method, the model scale effect was examined, the influences o...By combining the results of prototype observation of flood discharge atomization at the Wujiangdu Hydropower Station, and by adopting the serial model test method, the model scale effect was examined, the influences of the Reynolds and Weber numbers of water flow on the rain intensity of flood discharge atomization were analyzed and a rain intensity conversion relation was established. It is demonstrated that the level of atomization follows the geometric similarity relations and it is possible to ignore the influence of the surface tension of the flow when the Weber number is greater than 500. Despite limitations such as incomplete data sets, it is undoubtedly helpful to study the scale effect of atomization flow, and it is beneficial to identify the rules of the model test results in order to extrapolate to prototype prediction.展开更多
基金funded by the National Key R&D Program of China (Grant No. 2021YFB3901402)the Fundamental Research Funds for the Central Universities (Project No. 2022CDJKYJH037)。
文摘Landslide is the second largest natural disaster after earthquake. It is of significance to study the evolution laws and failure mechanism of landslides based on its surface 3D deformation information. Based on the rainfall-triggered waste dump instability model test, we studied the failure mechanisms of the waste dump by integrating surface deformation and internal slope stress and proposed novel parameters for identifying landslide stability. We developed a noncontact measurement device, which can obtain millimeter-level 3D deformation data for surface scene in physical model test;Then we developed the similar materials and established a test model for a waste dump. Based on the failure characteristics of slope surface, internal stress of slope body and displacement contours during the whole process, we divided the slope instability process in model test into four stages: rainfall infiltration and surface erosion, shallow sliding, deep sliding, and overall instability. Based on the obtained surface deformation data, we calculated the volume change during slope instability process and compared it with the point displacement on slope surface. The results showed that the volume change can not only reflect the slow-ultra acceleration process of slope failure, but also fully reflect the above four stages and reduce the fluctuations caused by random factors. Finally, this paper proposed two stability identification parameters: the volume change rate above the slip surface and the relative velocity of volume change rate. According to the calculation of these two parameters in model test, they can be used for study the deformation and failure mechanism of slope stability.
基金support from the National Natural Science Foundation of China (Grant No.42207199)Zhejiang Provincial Postdoctoral Science Foundation (Grant Nos.ZJ2022155 and ZJ2022156).
文摘Weak structural plane deformation is responsible for the non-uniform large deformation disasters in layered rock tunnels,resulting in steel arch distortion and secondary lining cracking.In this study,a servo biaxial testing system was employed to conduct physical modeling tests on layered rock tunnels with bedding planes of varying dip angles.The influence of structural anisotropy in layered rocks on the micro displacement and strain field of surrounding rocks was analyzed using digital image correlation(DIC)technology.The spatiotemporal evolution of non-uniform deformation of surrounding rocks was investigated,and numerical simulation was performed to verify the experimental results.The findings indicate that the displacement and strain field of the surrounding layered rocks are all maximized at the horizontal bedding planes and decrease linearly with the increasing dip angle.The failure of the layered surrounding rock with different dip angles occurs and extends along the bedding planes.Compressive strain failure occurs after excavation under high horizontal stress.This study provides significant theoretical support for the analysis,prediction,and control of non-uniform deformation of tunnel surrounding rocks.
基金financial support from China Scholarship Council(CSC)under the Grant CSC No.201406460041financial support from the Natural Sciences and Engineering Research Council of Canada(NSERC 402318)+4 种基金the Institut de Recherche Robert-Sauvéen Santéet en Sécuritédu Travail(IRSST 2013-0029)Fonds de Recherche du Québec-Nature et Technologies(FRQNT 2015-MI-191676)the industrial partners of Research Institute on Mines and Environment(RIME UQAT-Polytechnique)The financial support from the National Science and Technology Support Program of China(No.2013BAB02B02)the Scientific Research Fund of Beijing General Research Institute of Mining and Metallurgy of China(No.YJ201507)
文摘Mitchell's solution is commonly used to determine the required strength of vertically exposed cemented backfill in mines. Developed for drained backfill, Mitchell model assumed a zero friction angle for the backfill. Physical model tests were performed. Good agreements were obtained between the required strengths predicted by the analytical solution and experimental results. However, it is well-known that zero friction angle can only be possible in terms of total stresses when geomaterials are submitted to unconsolidated and undrained conditions. A revisit to Mitchell's physical model tests reveals that both the laboratory tests performed for obtaining the shear strength parameters of the cemented backfill and the box stability tests were conducted under a condition close to undrained condition. This explains well the good agreement between Mitchell's solution and experimental results. Good agreements are equally obtained between Mitchell's experimental results and FLAC3 D numerical modeling of shortterm stability analyses of exposed cemented backfill.
基金financially supported by the Young Scientist Project of the National Key Research and Development Program of China (No.2021YFC2900600)the Beijing Nova Program (No.20220484057)financial support from China Scholarship Council under Grant CSC No.202110300001。
文摘Estimation of stressses within the tailings slurry during self-weight consolidation is a critical issue for cost-effective barricade design and efficient backfill planning in underground mine stopes.This process requires a good understanding of self-weight consolidation behaviors of the tailings slurry within practical stopes,where many factors can have significant effects on the consolidation,including drainage condition and cement addition.In this paper,the prepared tailings slurry with different cement contents(0,4.76wt%,and 6.25wt%)was poured into1.2 m-high columns,which allowed three drainage scenarios(undrained,partial lateral drainage near the bottom part,and full lateral drainage boundaries)to investigate the effects of drainage condition and cement addition on the consolidation behavior of the tailings slurry.The consolidation behavior was analyzed in terms of pore water pressure(PWP),settlement,volume of drainage water,and residual water content.The results indicate that increasing the length of the drainage boundary or cement content aids in PWP dissipation.In addition,constructing an efficient drainage boundary was more favorable to PWP dissipation than increasing cement addition.The final stable PWP on the column floor was not sensitive to cement addition.The final settlement of uncemented tailings slurry was independent of drainage conditions,and that of cemented tailings slurry decreased with the increase in cement addition.Notably,more pore water can drain out from the cemented tailings slurry than the uncemented tailings slurry during consolidation.
文摘This study proposed the newly-designed Pelagic and demersal trawls for the fishing vessels operating in Cameroonian waters in pelagic and demersal fishing grounds. The engineering performances of both trawls were investigated using physical modelling method and analytical method based on the predicted equations. In a flume tank, a series of physical model tests based on Tauti’s law were performed to investigate the hydrodynamic and geometrical performances of both trawls and to assess the applicability of the analytical methods based on predicted equations. The results showed that in model scale, the working towing speed and door spread for the pelagic trawl were 3.5 knots and 1.85 m, respectively, and for the bottom trawl net they were 4.0 knots and 1.8 m. At that speed and door spread, the drag force, net opening height, and wing-end spread of the pelagic model trawl were 36.73 N, 0.89 m, and 0.86 m, respectively, and the swept area was 0.76 m<sup>2</sup>. Bottom trawl speed and door spread were 30.43 N, 0.38 m, and 0.45 m, respectively, and the swept area was 0.25 m<sup>2</sup>. The maximum difference between the experimental and analytical results of hydrodynamic performances was less than 56.22% and 41.45%, respectively, for pelagic and bottom trawls, the results of the geometrical performances obtained using predicted equations were close to the experimental results in the flume tank with a maximum relative error less than 12.85%. The newly developed pelagic and bottom trawls had advanced engineering performance for high catch efficiency and selectivity and could be used in commercial fishing operations in Cameroonian waters.
基金supported by National Natural Science Foundation of China (Grant NOs. 41877250, 41272284)the Key Laboratory of Earth Fissures Geological Disaster, Ministry of Natural Resources (No. EFGD20240601)the Natural Science Foundation of Shaanxi Province-General Project (grant number 2023-JC-YB-231)-Suitability Evaluation of Precast Prestressed Underground Comprehensive Pipe Gallery Crossing Active Ground Fissure。
文摘The Fenwei Basin, covered by loess, experiences severe ground fissure disasters. These disasters disrupt the continuity of the loess and pose significant threats to engineering construction safety along transportation routes. Nevertheless, the crack characteristics and the influence zone of ground fissures in the loess layer remain inadequately investigated. To effectively prevent and control ground fissure disasters, physical model tests and the PFC(particle flow code) numerical simulation method are used to investigate the crack mechanism of buried ground fissures in the loess layer. The results show that there are two main cracks in the layer profile, which have a Y-shape morphology. As the dip angle of the preset cracks increased from 60° to 90°, the main deformation zone at the surface gradually shifted towards the footwall. The process of crack propagation from depth to surface is divided into five stages. Additionally, the results confirm the accuracy of the width of the rupture zone d2in the footwall calculated by the cantilever beam theory. These findings can offer theoretical guidance for determining the avoidance distance of ground fissures in loess regions, as well as for implementing disaster prevention and corresponding control measures for various stages of buried ground fissure propagation.
基金sponsored by the National Science Foundation(CMMI#1558887 and CMMI#1932452).
文摘Motivated by the promising benefits of connected and autonomous vehicles (CAVs) in improving fuelefficiency, mitigating congestion, and enhancing safety, numerous theoretical models have been proposed to plan CAVmultiple-step trajectories (time–specific speed/location trajectories) to accomplish various operations. However, limitedefforts have been made to develop proper trajectory control techniques to regulate vehicle movements to follow multiplesteptrajectories and test the performance of theoretical trajectory planning models with field experiments. Without aneffective control method, the benefits of theoretical models for CAV trajectory planning can be difficult to harvest. This studyproposes an online learning-based model predictive vehicle trajectory control structure to follow time–specific speed andlocation profiles. Unlike single-step controllers that are dominantly used in the literature, a multiple-step model predictivecontroller is adopted to control the vehicle’s longitudinal movements for higher accuracy. The model predictive controlleroutput (speed) cannot be interpreted by vehicles. A reinforcement learning agent is used to convert the speed value to thevehicle’s direct control variable (i.e., throttle/brake). The reinforcement learning agent captures real-time changes in theoperating environment. This is valuable in saving parameter calibration resources and improving trajectory control accuracy.A line tracking controller keeps vehicles on track. The proposed control structure is tested using reduced-scale robot cars.The adaptivity of the proposed control structure is demonstrated by changing the vehicle load. Then, experiments on twofundamental CAV platoon operations (i.e., platooning and split) show the effectiveness of the proposed trajectory controlstructure in regulating robot movements to follow time-specific reference trajectories.
基金supported by the National Key Research and Development Plan of China(No.2016YFC0600901)the National Natural Science Foundation of China(No.51874311)the Natural Science Foundation of China(No.51904306)。
文摘To explore the failure mechanism of roadway in layered soft rocks,a physical model with the physically finite elemental slab assemblage(PFESA)method was established.Infrared thermography and a video camera were employed to capture thermal responses and deformation.The model results showed that layered soft roadway suffered from large deformation.A three-dimensional distinct element code(3 DEC)model with tetrahedral blocks was built to capture the characteristics of roadway deformation,stress,and cracks.The results showed two failure patterns,layer bending fracture and layer slipping after excavation.The layer bending fracture occurred at positions where the normal direction of layers pointed to the inside of the roadway and the layer slipping occurred in the ribs.Six schemes were proposed to investigate the effects of layered soft rocks.The results showed that the deformation of ribs was obviously larger than that of the roof and floor when the roadway passed through three types of strata.When the roadway was completely in a coal seam,the change of deformation in ribs was not obvious,while the deformation in the roof and floor increased obviously.These results can provide guidance for excavation and support design of roadways in layered soft rocks.
基金Project(2015QNA40)supported by the Fundamental Research Funds for the Central Universities,China
文摘The waste dump of open-pit coal mine is remade of soil-rock mixture under the action of gravity,dynamic load of transportation equipment and earthquake,etc.By using artificial synthetic transparent soil,the developing process and migration law for soil-rock mixture are observed in the remade process.The mixture of fused quartz sand,liquid paraffin and n-tridecane is chosen as the material for synthetic transparent soil which is mixed with liquid paraffin and n-tridecane at a mass ratio of4.4at room temperature of17℃.Physical and mechanical properties of transparent soil are determined by physical test and compared with those in natural sandy soil.The results show that transparent soil and sandy soil have high similarity,in other words,transparent soil can be used for similar simulation experiments of soil-rock mixture.
基金Projects(51278209,51478047)supported by the National Natural Science Foundation of ChinaProject(2014FJ-NCET-ZR03)supported by the Program for New Century Excellent Talents in Fujian Provincial Universities,China+1 种基金Project(JA13005)supported by the Incubation Program for Excellent Young Science and Technology Talents in Fujian Provincial Universities,ChinaProject(ZQN-PY110)supported by the Young and Middle-aged Academic Staff of Huaqiao University,China
文摘The static tests of nine traditional and bird beak square hollow structure(SHS) T-joints with different β values and connection types under axial compression at brace end were carried out. Experimental test schemes, failure modes of specimens, jack load-vertical displacement curves, jack load-deformation of chord and strain intensity distribution curves of joints were presented. The effects of β and connection types on axial compression property of joints were studied. The results show that the ultimate axial compression capacity of common bird beak SHS T-joints and diamond bird beak SHS T-joints is larger than that of traditional SHS T-joint specimens with big values of β. The ultimate axial compression capacity of diamond bird beak SHS T-joints is larger than that of common bird beak SHS T-joints. As β increases, the increase of the ultimate axial compression capacity of diamond bird beak SHS T-joints over that of common bird beak joints grows. The ultimate axial compression capacity and the initial axial stiffness of all kinds of joints increase as β increases, and the initial axial stiffness of the diamond bird beak SHS T-joints is the largest. The ductilities of common bird beak and diamond bird beak SHS T-joints increase as β increases, but the ductility of the traditional SHS T-joints decreases as β increases.
基金sponsored by the National Natural Science Foundation of China(No.41274129)the National Research Program of China(No.2008ZX05035-001-006HZ and No.2011ZX05035-005-003HZ)
文摘In this study, we experimentally established the relationship between physical properties, vitrinite reflectance, and microstructure of coal, Taiyuan Formation, Qinshui Basin, China using representative coal samples collected from three different mines via the rock mechanics testing system （MTS）. We analyzed the organic macerals, vitrinite reflectance, and microstructure of 11 coal samples using petrography and scanning electron microscopy （SEM）. The experimental results suggest that （1） the elastic parameters can be described by linear equations, （2） both P- and S-wave velocities display anisotropy, （3） the anisotropy negatively correlates with vitrinite reflectance, and （4） the acoustic velocities and Young＇s modulus are negatively correlated with the volume of micropores. The derived empirical equations can be used in the forward modeling and seismic inversion of physical properties of coal for improving the coal-bed methane （CBM） reservoir characterization.
文摘This study focuses on the evaluation of the differences of physical fitness among soccer players, handball players, and basketball players, and the investigation of the physical fitness structures of those players. The participants consisted of 160 elite players selected from university teams. Fourteen tests related to health and motor fitness were conducted. The results were subjected to a multivariate analysis of variance (MANOVA) to test the mean vector differences among the three groups of different sport. Nine out of the fourteen tests were of significantly discriminating results regarding to different group, which include side step, abdominal strength, shuttle running, 100m running, pull-up, 1,500m running, trunk flexion, grip strength and broad jump, as determined by a stepwise regression approach. MANOVA showed that there was a significant difference (p<0.001) of the mean vectors of the 9 tests among the three events. Discriminant function analysis showed that three discriminant functions were significant, whose correctness was testified by the classification analysis to be over 80.2%. It is demonstrated that elite handball players are good at agility, elite soccer players are speedy, and successful basketball players apparently possess preeminent muscular strength and endurance.
基金This work was supported by the Fundamental Research Funds for the Central Universities,the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX21_0487)the National Natural Science Foundation of China(Grant Nos.41831278,and 51579081).
文摘The irregularity of jointed network poses a challenge to the determination of field mechanical param-eters of columnar jointed rock mass(CJRM),and a reasonable prediction of deformation and strength characteristics of CJRM is important for engineering construction.The Voronoi diagram and three-dimensional printing technology were used to make an irregular columnar jointed mold,and the irregular CJRM(ICJRM)specimens with different dip directions and dip angles were prepared.Uniaxial compression tests were performed,and the anisotropic strength and deformation characteristics of ICJRM were described.The failure modes and mechanisms were revealed in accordance with the final appearances of the ICJRM specimens.Based on the model test results,the empirical correlations for determining the field deformation and strength parameters of CJRM were derived using the dip angle and modified joint factor.The proposed empirical equations were used in the Baihetan Project,and the calculated mechanical parameters were compared with the field test results and those obtained from the tunneling quality index method.Results showed that the deformation parameters determined by the two proposed methods are all consistent with the field test results,and these two methods can also estimate the strength parameters effectively.
基金financed by the National Natural Science Foundation of China(Grant Nos.41472274,41672300)Independent Subject Foundation of SKLGP(SKLGP2017Z010)。
文摘The failure of slope caused by variations in water levels on both banks of reservoirs is common.Reservoir landslides greatly threaten the safety of reservoir area.Taking large-scale composite deposits located on the Lancang River in Southwest China as a study case,the origin of the deposits was analyzed based on the field investigation and a multi-material model was established in the physical model test.Combined with numerical simulation,the failure mechanism of the composite deposits during reservoir water level variations was studied.The results indicate that the deformation of the large-scale composite deposits is a staged sliding mode during the impoundment process.The first slip deformation is greatly affected by the buoyancy weight-reducing effect,and the permeability of soil and variation in the water level are the factors controlling slope deformation initiation.The high water sensitivity and low permeability of fine grained soil play an important role in the re-deformation of deposits slope.During the impoundment process,the deformation trend of the deposit slope is decreasing,and vertical consolidation of soil and increasing hydrostatic pressure on the slope surface are the main reasons for deformation attenuation.It is considered that the probability of large-scale sliding of the deposits during the impoundment period is low.But the damage caused by local bank collapse of the deposit slope still needs attention.The results of this paper will further improve our understanding of the failure mechanism of composite deposits caused by water level increases and provide guidance for the construction of hydropower stations.
文摘Introduction:Locomotion is a determinant of intrinsic capacity of older people and can be limited by dysfunction in locomotory organs,characterizing Locomotive Syndrome(LoS).Knowledge on locomotive problems and sarcopenia,and their interface with quality of life,in the oldest old in the literature is scarce.Objective:To evaluate the correlation between LoS and sarcopenia and their influence on quality of life in oldest old.Methods:A cross-sectional study of an observational,descriptive and analytical epidemiological survey in independent older adults aged 80 and over from São Paulo,Brazil and who participated in the third wave of the LOCOMOV Project,was carried out.Sociodemographic data,comorbidities,functioning in activities of daily living,physical functioning,quality of life,and presence of sarcopenia and LoS were assessed.The statistical analyses included the Test-for-Comparing-Two-Proportions,Pearson's Correlation Coefficient,the chi-Square test and Student´s t-test.Results:Thirty oldest old with a mean age of 89.1 years were evaluated.The prevalence of LoS was high(53.3%)and correlated significantly with chronic pain(p-value 0.024),worse performance on the SPPB and Gait speed(p-value<0.001).Sarcopenia was not correlated with LoS,but worse quality of life on the physical domain was significantly associated with LoS(p-value<0.001)regardless of the presence of sarcopenia.Conclusions:LoS was highly prevalent among the oldest old studied and negatively impacted their quality of life,regardless of the presence of sarcopenia.
基金supported by the National Natural Science Foundation of China(Grant No.50809014)the National High Technology Research and Development Program of China(863 Program,Grant No.2006AA100301)the Specialized Research Fund for the Doctoral Program of Higher Education(Grant No.200801411094)
文摘In this paper, the numerical model of the net cage with the grid mooring system in waves is set up by the lumped mass method and rigid kinematics theory, and then the motion equations of floating system, net system, mooring system, and floaters are solved by the Runge-Kutta fifth-order method. For the verification of the numerical model, a series of physical model tests have been carried out. According to the comparisons between the simulated and experimental results, it can be found that the simulated and experimental results agree well in each condition. Then, the effects of submerged depth of grid and direction of incident wave propagation on hydrodynamic behaviors of the net cage are analyzed. According to the simulated results, it can be found that with the increase of submerged depth of grid, the forces acting on mooring lines and bridle lines increase, while the forces on grid lines decrease; the horizontal motion amplitudes of floating collar decrease obviously, while the vertical motion amplitudes of floating collar change little. When the direction of incident wave propagation changes, forces on mooring lines and motion of net cage also change accordingly. When the propagation direction of incident wave changes from 0° to 45°, forces on the main ropes and bridle ropes increase, while the forces on the grid ropes decrease. With the increasing propagation direction of incident wave, the horizontal amplitude of the forces collar decreases, while the vertical amplitude of the floating collar has little variation.
基金Projects(11972378,41630642)supported by the National Natural Science Foundation of China。
文摘The goaf may face a series of deformation and settlement problems when the room-pillar mining method is used to excavate ore and pillars in the deep strata.To this end,a deep room-pillar model with two levels was made,and the pillar recovery was carried out.The instantaneous deformation responses during the pillars recovery and the long-term settlements after the pillar recovery were analyzed.During the pillar recovery,different regions of surrounding rocks suffer from different dynamic disturbances which can be divided into three types,including(I)the combined action of blasting disturbance and unloading disturbance,(II)the sequential action of blasting disturbance and unloading disturbance,and(III)the action of unloading disturbance.After the pillar recovery,the settlement above the first recovering pillar is the largest,which has a traction effect on the settlement in other areas.The settlement process can be divided into two stages,stable displacement stage and unstable displacement stage.When the pillar-room system undergoes the unstable displacement stage,rock spalling and further cascading collapse will occur.
基金funded by the Key Program of National Natural Science Foundation of China (41630643)the National Key Research and Development Program of China (2017YFC1501302)the Fundamental Research Funds for the Central Universities, China University of Geosciences (Wuhan) (CUGCJ1701)
文摘Many landslides in reservoir areas continuously deform under cyclic water level fluctuations due to reservoir operations. In this paper,a landslide model, developed for a typical colluvial landslide in the Three Gorges Reservoir area, is used to study the effect of cyclic water level fluctuations on the landslide. Five cyclic water level fluctuations were implemented in the test, and the fluctuation rate in the last two fluctuations doubled over the first three fluctuations. The pore water pressure and lateral landslide profiles were obtained during the test. A measurement of the landslide soil loss was proposed to quantitatively evaluate the influence of water level fluctuations. The test results show that the first water level rising is most negative to the landslide among the five cycles. The fourth drawdown with a higher drawdown rate caused further large landslide deformation. An increase of the water level drawdown rate is much more unfavorable to the landslide than an increase of the water level rising rate. In addition, the landslide was found to have an adaptive ability to resist subsequent water level fluctuations after undergoing large deformation during a water level fluctuation. The landslide deformation and observations in the field were found to support the test results well.
基金supported by the National Natural Science Foundation of China (Grant No 50579084)the Foundation of the Nanjing Hydraulic Research Institute (Grant No Y10705)
文摘By combining the results of prototype observation of flood discharge atomization at the Wujiangdu Hydropower Station, and by adopting the serial model test method, the model scale effect was examined, the influences of the Reynolds and Weber numbers of water flow on the rain intensity of flood discharge atomization were analyzed and a rain intensity conversion relation was established. It is demonstrated that the level of atomization follows the geometric similarity relations and it is possible to ignore the influence of the surface tension of the flow when the Weber number is greater than 500. Despite limitations such as incomplete data sets, it is undoubtedly helpful to study the scale effect of atomization flow, and it is beneficial to identify the rules of the model test results in order to extrapolate to prototype prediction.
