Bi-directional static loading test adopting load cells is widely used around the world at present,with increase in diameter and length of deep foundations.In this paper,a new simple conversion method to predict the eq...Bi-directional static loading test adopting load cells is widely used around the world at present,with increase in diameter and length of deep foundations.In this paper,a new simple conversion method to predict the equivalent pile head load-settlement curve considering elastic shortening of deep foundation was put forward according to the load transfer mechanism.The proposed conversion method was applied to root caisson foundation in a bridge and to large diameter pipe piles in a sea wind power plant.Some new load cells,test procedure,and construction technology were adopted based on the applications to different deep foundations,which could enlarge the application scopes of bi-directional loading test.A new type of bi-directional loading test for pipe pile was conducted,in which the load cell was installed and loaded after the pipe pile with special connector has been set up.Unlike the conventional bi-directional loading test,the load cell can be reused and shows an evident economic benefit.展开更多
According to the catastrophe model for impact buckling of static loading structures, a new catastrophe model for impact loading failure of a static loading rock system was established, and one dimension (1D) catastrop...According to the catastrophe model for impact buckling of static loading structures, a new catastrophe model for impact loading failure of a static loading rock system was established, and one dimension (1D) catastrophe model was analyzed. The analysis results indicate that the furcation collection where catastrophe may take place is not only decided by mechanical system itself but also relates to exterior loading, which is different from the results obtained under mono-static loading where the bifurcation collection is only determined by mechanics of the system itself and has nothing to do with exterior loading. In addition, the corresponding 1D coupled static-dynamic loading experiment is designed to verify the analysis results of catastrophe model. The test is done with Instron 1342 electro-servo controlled testing system, in which medium strain rate is caused by monotony rising dynamic load. The parameters are obtained combining theoretical model with experiment. The experimental and theoretical curves of critical dynamic load vs static load are rather coincided, thus the new model is proved to be correct.展开更多
Seismic method is usually used for elastic parametric estimation. This is why this method presents dynamic parameters of Earth. Frequency seismic range changes greatly from geodynamic modelling time. Now we have oppor...Seismic method is usually used for elastic parametric estimation. This is why this method presents dynamic parameters of Earth. Frequency seismic range changes greatly from geodynamic modelling time. Now we have opportunity to use geodesy result for some years for elastic parameters estimation. Static solution from elastic theory may be used for the interpretation of long term results. It presents static elastic parameter. The inverse problem for different types of vertical surface loading on one year period is calculated. Two cases of loading with maximal and minimal area are presented. Results are determined by space geodesy and leveling methods. Current relation between atmospheric pressure and vertical displacements was estimated at the center of Siberian Anti Cyclone with size varied from 2000 km to 3000 kin. Pressure-displacement coefficients （PDC） can be achieved by three years obser- vation （0.997 mm/mbar for NVSK GPS station）. It is used for elastic module study of geology medium with maximum thickness up to 600 km. In the context of elastic model, the modulus of rigidity is estimated to be 113 GPa. Vast expanse of anti-cyclone may relate with rheology of crust and upper mantle. Smaller size of surface loading - local loading is seasonal variation of water reservoir. Annual vertical changes were obtained by leveling near the dam of the reservoir. PDC ratio was 1.15 mm/bar for these places. In elastic theory, the Young modulus E = 80 GPa （Poisson ratio = 0.25, the modulus of rigidity - 32 GPa） was calculated by sixteen years of leveling measurements. This result can effectively be represented for upper crust. Our results were checked by solution for coseismic displacement of Chyia- Altai earthquake （Sep. 27, 2003, M = 7.3）. Coseismic results calculated by static modules agree with experimental coseismic GPS data at 10% level.展开更多
An eight-channel force loading system is presented, which adopts position control system and force control system switching model, small flow servo valve controlled capacious cylinder system scheme, intelligent PID al...An eight-channel force loading system is presented, which adopts position control system and force control system switching model, small flow servo valve controlled capacious cylinder system scheme, intelligent PID algorithm and distributed load approach. Through the analyses of the equivalent model of valve controlled cylinder force subsystem, a controller based on intelligent PID algorithm is designed, which is not sensitive to the variation of parameters such as environmental stiffness. According to the coupling of multiple load channels, a distributed load approach is employed in the superior monitor computer. Experimental results show that the system designed has high precision and robustness.展开更多
The deep mining of coal resources is accompanied by severe environmental challenges and various potential engineering hazards.The implementation of NPR(negative Poisson's ratio)bolts are capable of controlling lar...The deep mining of coal resources is accompanied by severe environmental challenges and various potential engineering hazards.The implementation of NPR(negative Poisson's ratio)bolts are capable of controlling large deformations in the surrounding rock effectively.This paper focuses on studying the mechanical properties of the NPR bolt under static disturbance load.The deep nonlinear mechanical experimental system was used to study the mechanical behavior of rock samples with different anchored types(unanchored/PR anchored/2G NPR anchored)under static disturbance load.The whole process of rock samples was taken by high-speed camera to obtain the real-time failure characteristics under static disturbance load.At the same time,the acoustic emission signal was collected to obtain the key characteristic parameters of acoustic emission such as acoustic emission count,energy,and frequency.The deformation at the failure of the samples was calculated and analyzed by digital speckle software.The findings indicate that the failure mode of rock is influenced by different types of anchoring.The peak failure strength of 2G NPR bolt anchored rock samples exhibits an increase of 6.5%when compared to the unanchored rock samples.The cumulative count and cumulative energy of acoustic emission exhibit a decrease of 62.16%and 62.90%,respectively.The maximum deformation of bearing capacity exhibits an increase of 59.27%,while the failure time demonstrates a delay of 42.86%.The peak failure strength of the 2G NPR bolt anchored ones under static disturbance load exhibits an increase of 5.94%when compared to the rock anchored by PR(Poisson's ratio)bolt.The cumulative count and cumulative energy of acoustic emission exhibit a decrease of 47.16%and 43.86%,respectively.The maximum deformation of the bearing capacity exhibits an increase of 50.43%,and the failure time demonstrates a delay of 32%.After anchoring by 2G NPR bolt,anchoring support effectively reduces the risk of damage caused by static disturbance load.These results demonstrate that the support effect of 2G NPR bolt materials surpasses that of PR bolt.展开更多
The stability control of surrounding rock for large or super-large section chamber is a difficult technical problem in deep mining condition.Based on the in-site geological conditions of Longgu coal mine,this paper us...The stability control of surrounding rock for large or super-large section chamber is a difficult technical problem in deep mining condition.Based on the in-site geological conditions of Longgu coal mine,this paper used the dynamic module of FLAC3D to study the response characteristics of deep super-large section chamber under dynamic and static combined loading condition.Results showed that under the static loading condition,the maximum vertical stress,deformation and failure range are large,where the stress concentration coefficient is 1.64.The maximum roof-to-floor and two-sides deformations are 54.6 mm and 53.1 mm,respectively.Then,under the dynamic and static combined loading condition:(1)The influence of dynamic load frequency on the two-sides is more obvious;(2)The dynamic load amplitude has the greatest influence on the stress concentration degree,and the plastic failure tends to develop to the deeper;(3)With the dynamic load source distance increase,the response of surrounding rock is gradually attenuated.On this basis,empirical equations for each dynamic load conditions were obtained by using regression analysis method,and all correlation coefficients are greater than 0.99.This research provided reference for the supporting design of deep super-large section chamber under same or similar conditions.展开更多
By means of the improved split Hopkionson pressure bar(SHPB) with axial pre-pressure and confined pressure, two series of experiments on sandstone are carried out to research the failure mode of rock during the course...By means of the improved split Hopkionson pressure bar(SHPB) with axial pre-pressure and confined pressure, two series of experiments on sandstone are carried out to research the failure mode of rock during the course of exploitation of resources in deep. One is under the conditions that the con-fining pressure is fixed and the axial pressure is changeable. The other is under the conditions that the confining pressure becomes and the axial pressure is fixed. It is found that samples break up evenly after impacting when axial static pressures are low, there is great disparity in size of fragments when axial static pressures are high, and the main bodies of samples after the tests under the combination of dy-namic and static loads frequently show the type of V or X. The samples are more close-grained at the elastic stage and impacts make many cracks be generated and developed, as makes samples more crackable. At the initial phase of damage stage, the static pressures make some cracks in the samples which are undeveloped and the impacts′ role is similar to that at the elastic stage. At the metaphase or anaphase of damage stage, these cracks in the samples develop adequately and the impacts mainly accelerate samples′ failure. The main bodies of samples show the type of V or X after impacting due to the confining pressures′ restraining samples′ lateral formation at the elastic stage or the initial phase of damage stage, the main bodies of samples have almost formed at the stage loading static pressures and the results after impacting usually are similar to those under the axial pressures tests.展开更多
The stability control of fissured rock is difficult,especially under static and dynamic loads in deep coal mines.In this paper,the dynamic mechanical properties,strain rate evolution and energy dissipation of fissured...The stability control of fissured rock is difficult,especially under static and dynamic loads in deep coal mines.In this paper,the dynamic mechanical properties,strain rate evolution and energy dissipation of fissured and anchored rocks were respectively obtained by SHPB tests.It was found that bolt can provide supporting efficiency-improving effect for fissured rock against dynamic disturbance,and this effect increased quadratically with decrease in anchoring angles.Then,the energy dissipation mechanism of anchored rock was obtained by slipping model.Furthermore,bolt energy-absorbing mechanism by instantaneous tensile-shear deformation was expressed based on material mechanics,which was the larger the anchoring angle,the smaller the energy absorption,and the less the contribution to supporting efficiency improvement.On this basis,the functional relationship between energy dissipation of anchored rock and energy absorption of bolt was established.Taking the coal-gangue separation system of Longgu coal mine as an example,the optimal anchoring angle can be determined as 57.5°–67.5°.Field monitoring showed fissured rock with the optimal anchoring angle,can not only effectively control the deformation,but also fully exert the energy-absorbing and efficiency-improving effect of bolt itself.This study provides guidance to the stability control and supporting design for deep engineering under the same or similar conditions.展开更多
This study explores the effects of dynamic and static loading on rock bolt performance a key factor in maintaining the structural safety of coal mine roadways susceptible to coal bursts.Employing a housemade load fram...This study explores the effects of dynamic and static loading on rock bolt performance a key factor in maintaining the structural safety of coal mine roadways susceptible to coal bursts.Employing a housemade load frame to simulate various failure scenarios,pretension-impact-pull tests on rock bolts were conducted to scrutinize their dynamic responses under varied static load conditions and their failure traits under combined loads.The experimental results denote that with increased impact energy,maximum and average impact loads on rock bolts escalate significantly under pretension,initiating plastic deformation beyond a certain threshold.Despite minor reductions in the yield load due to impactinduced damage,pretension aids in constraining post-impact deformation rate and fluctuation degree of rock bolts.Moreover,impact-induced plastic deformation causes internal microstructure dislocation,fortifying the stiffness of the rock bolt support system.The magnitude of this fortification is directly related to the plastic deformation induced by the impact.These findings provide crucial guidance for designing rock bolt support in coal mine roadway excavation,emphasizing the necessity to consider both static and dynamic loads for improved safety and efficiency.展开更多
The effects of microstructure on quasi-static transverse loading behavior of 3D circular braided composite tubes were studied. Transverse loading tests were conducted. Transverse load-deflection curves were obtained t...The effects of microstructure on quasi-static transverse loading behavior of 3D circular braided composite tubes were studied. Transverse loading tests were conducted. Transverse load-deflection curves were obtained to analyze the effects of braiding parameters including the braiding angle, the wall thickness, and the diameter on the transverse loading of 3D circular braided composite tubes. Breaking loads, moduli and strengths had also been used to describe the transverse loading behaviors. The failure morphologies were shown to reveal damage mechanisms. From the results, the increase in braiding angle, wall thickness and diameter increases the ability of anti-deformation and breaking load of braided tubes. The breaking load of specimen with a braiding angle of 45° is about 1.68 times that of specimen with a braiding angle of 15°. The breaking load of specimen with 4 layers of yarns is about 2.15 times that of specimen with 2 layers of yarns. The breaking load of the tube with a diameter of 25.5 mm is about 2.39 times that of the tube with a diameter of 20.5 mm.展开更多
The present paper investigates the collapse process of a pipe-framed greenhouse under static wind loading based on a non-linear finite element analysis.The purpose is to establish a more reasonable wind resistant desi...The present paper investigates the collapse process of a pipe-framed greenhouse under static wind loading based on a non-linear finite element analysis.The purpose is to establish a more reasonable wind resistant design method for such structures.The structures are so flexible that the fluid-structure interaction(FSI)is considered in the analysis.In practice,iterative analyses of the structure’s response and the wind pressure distribution on the deformed structure are made.The wind direction is normal to the ridge.Computational fluid dynamics(CFD)analysis with a RANS turbulence model is used for evaluating the time-averaged wind pressure coefficient distribution on the structure.Both the geometric and the material non-linearity are considered in the structural analysis.The collapse behavior obtained is consistent with the practical one often observed in damage investigations.Based on the results,discussion is made of the validity of the current design guideline commonly used in Japan.The same analysis is carried out for various reinforced models.The effect of each reinforcement method on the improvement of wind resistance of the structure is investigated on the basis of the allowable stress and deformation limits specified in the current design guideline.展开更多
This article uses real engineering projects as examples to analyze how static load test technology is applied in testing the bridge-bearing capacity.The analysis covers aspects such as testing section layout,test load...This article uses real engineering projects as examples to analyze how static load test technology is applied in testing the bridge-bearing capacity.The analysis covers aspects such as testing section layout,test load and efficiency coefficient,loading plan,evaluation optimization,test result modification,and result evaluation.The aim is to support the accurate detection and evaluation of bridge-bearing capacity.展开更多
China's railway prestressed concrete bridge has more than 600000 holes,prestressed engineering is a key force system affecting the safety and durability of the prestressed concrete bridge structure,its constructio...China's railway prestressed concrete bridge has more than 600000 holes,prestressed engineering is a key force system affecting the safety and durability of the prestressed concrete bridge structure,its construction quality is easily affected by traditional manual operation technology,resulting in low construction efficiency and control accuracy,easy to form a hidden danger of quality and safety,it is difficult to meet the needs of less humanized,standardized intelligent construction trend.Based on the research on the intelligent prestressed construction control and testing technology and equipment for railway bridges,this paper proposes the integration of intelligent prestressed tension control and tunnel friction test of railway bridges,intelligent grouting control of tunnel and intelligent testing of beam construction quality,and sets up a complete technical system and integrated equipment for intelligent prestressed construction of bridges based on the industrial Internet of Things(IoT).Overall,improve the quality and efficiency of bridge production,construction,and management.展开更多
Seismicity resulting from the near-or in-field fault activation significantly affects the stability of large-scale underground caverns that are operating under high-stress conditions.A comprehensive scientific assessm...Seismicity resulting from the near-or in-field fault activation significantly affects the stability of large-scale underground caverns that are operating under high-stress conditions.A comprehensive scientific assessment of the operational safety of such caverns requires an in-depth understanding of the response characteristics of the rock mass subjected to dynamic disturbances.To address this issue,we conducted true triaxial modeling tests and dynamic numerical simulations on large underground caverns to investigate the impact of static stress levels,dynamic load parameters,and input directions on the response characteristics of the surrounding rock mass.The findings reveal that:(1)When subjected to identical incident stress waves and static loads,the surrounding rock mass exhibits the greatest stress response during horizontal incidence.When the incident direction is fixed,the mechanical response is more pronounced at the cavern wall parallel to the direction of dynamic loading.(2)A high initial static stress level specifically enhances the impact of dynamic loading.(3)The response of the surrounding rock mass is directly linked to the amplitude of the incident stress wave.High amplitude results in tensile damage in regions experiencing tensile stress concentration under static loading and shear damage in regions experiencing compressive stress concentration.These results have significant implications for the evaluation and prevention of dynamic disasters in the surrounding rock of underground caverns experiencing dynamic disturbances.展开更多
Lightweight structures for gears enable a reduction in material usage while maintaining the technical function of the gear.Previous approaches have pursued the strategy of lightweight structures in the gear wheel body...Lightweight structures for gears enable a reduction in material usage while maintaining the technical function of the gear.Previous approaches have pursued the strategy of lightweight structures in the gear wheel body.By taking inspiration from biological models and utilizing material savings in the gear rim,new design approaches for the lightweight design of gears can be realized.For this reason,a holistic biological design approach for spur gears is presented.In addition to the method of topology optimization,a biologically inspired approach based on diatoms is introduced,which achieves a weight reduction of over 50%compared to conventional solid gears.Diatom structures are extracted from the oceans,digitally modelled,and adapted to the load conditions of a reference gear by parametric design and simulation optimization.For the experimental validation of the design,a manufactured gear is statically loaded in the nominal load range and analyzed using a tactile geometry gear measurement.The measurement results of selected standard gear parameters show that the gear does not exhibit any plastic deformation for the nominal load capacity of 383 Nm,validating the presented design approach.展开更多
Borehole pressure relief helps prevent rock bursts.However,this may change the physical and mechan-ical properties of the surrounding rock,affect the variation of the plastic zone of the roadway,and lead to the failur...Borehole pressure relief helps prevent rock bursts.However,this may change the physical and mechan-ical properties of the surrounding rock,affect the variation of the plastic zone of the roadway,and lead to the failure of roadway support,thus threatening the safety of the roadway.In this paper,the variable angle shear test of drilled specimens under the action of static and dynamic loads is used to study the evolution of mechanical parameters of the specimens and their influence on the plastic zone of the sur-rounding rock.The shear strength decreases linearly with the increase of drilling diameter.With the increase of pre-static load level and dynamic load amplitude,the cohesion first increases and then decreases,and the internal friction angle decreases.Moreover,the shear failure surface changes from rough to smooth.The reasons include that the static load enhances the tooth cutting effect and the repeated friction of cracks caused by the dynamic load.Borehole pressure relief leads to an increase in the radius of the plastic zone of the surrounding rock following a quadratic function.The research results of this paper provide a theoretical basis for designing drilling unloading parameters and supporting parameters for rock burst roadways.展开更多
The presence of geological structures such as faults, joints, and dykes has been observed near excavation boundaries in many rockburst case histories. In this paper, the role of discontinuities around tunnels in rockb...The presence of geological structures such as faults, joints, and dykes has been observed near excavation boundaries in many rockburst case histories. In this paper, the role of discontinuities around tunnels in rockburst occurrence was studied. For this purpose, the Abaqus explicit code was used to simulate dynamic rock failure in deep tunnels. Material heterogeneity was considered using Python scripting in Abaqus. Rockbursts near fault regions in deep tunnels under static and dynamic loads were studied.Several tunnel models with and without faults were built and static and dynamic loads were used to simulate rock failure. The velocity and the released kinetic energy of failed rocks, the failure zone around the tunnel, and the deformed mesh were studied to identify stable and unstable rock failures. Compared with models without discontinuities, the results showed that the velocity and the released kinetic energy of failed rocks were higher, the failure zone around the tunnel was larger, and the mesh was more deformed in the models with discontinuities, indicating that rock failure in the models with discontinuities was more violent. The modeling results confirm that the presence of geological structures in the vicinity of deep excavations could be one of the major influence factors for the occurrence of rockburst. It can explain localized rockburst occurrence in civil tunnels and mining drifts. The presented methodology in this paper for rockburst analysis can be useful for rockburst anticipation and control during mining and tunneling in highly stressed ground.展开更多
The rotating circular plate is widely used in mechanical engineering, meanwhile the plates are often in the electromagnetic field in modern industry with complex loads. In order to study the resonance of a rotating ci...The rotating circular plate is widely used in mechanical engineering, meanwhile the plates are often in the electromagnetic field in modern industry with complex loads. In order to study the resonance of a rotating circular plate under static loads in magnetic field, the nonlinear vibration equation about the spinning circular plate is derived according to Hamilton principle. The algebraic expression of the initial deflection and the magneto elastic forced disturbance differential equation are obtained through the application of Galerkin integral method. By mean of modified Multiple scale method, the strongly nonlinear amplitude-frequency response equation in steady state is established. The amplitude frequency characteristic curve and the relationship curve of amplitude changing with the static loads and the excitation force of the plate are obtained according to the numerical calculation. The influence of magnetic induction intensity, the speed of rotation and the static loads on the amplitude and the nonlinear characteristics of the spinning plate are analyzed. The proposed research provides the theory reference for the research of nonlinear resonance of rotating plates in engineering.展开更多
As a special geological phenomenon, the character of collapsible loess foundation is collapsible when penetrated by water. This character leads to the soil losing load bearing capacity largely and may lead to foundati...As a special geological phenomenon, the character of collapsible loess foundation is collapsible when penetrated by water. This character leads to the soil losing load bearing capacity largely and may lead to foundation failure. Pile is a popular foundation used in collapsible loess. The squeezed branch and plate pile is a new type of pile developed in recent years and has not be used in a project before. In this paper three squeezed branch and plate piles are tested in collapsible loess after immersion processing. The results may be used for reference in similar construction project, and to provide theoretical references for de- signing of the squeezed branch and plate piles in engineering practice.展开更多
The failure characteristics under coupled static and dynamic loading were investigated by the improved split Hopkinson pressure bar （SHPB） with axial pre-pressure and confining pressure. The results show that the st...The failure characteristics under coupled static and dynamic loading were investigated by the improved split Hopkinson pressure bar （SHPB） with axial pre-pressure and confining pressure. The results show that the stress—strain curve of the rock under static-dynamic coupled loading is a typical class I curve when the dynamic load is comparatively high; With the decrease of the dynamic load, the stress—strain curve transforms to a typical class II curve. The dynamic failure process was recorded by high-speed photography. Analyses of fracture surface morphology show that the failure modes of specimens are tensile failure or combined shear failure when the impact load energy is low, but the failure modes of specimens become tensile failure when the impact load energy is high. The results of fractal dimension show that the elastic potential energy release leads to increase in the degree of crushing of samples when the energy of impact load is low under coupled static and dynamic loads with high stress.展开更多
基金Supported by the National Natural Science Foundation of China(50908048)the Priority Academic Program Development(PAPD)Project of JiangsuHigher Education Institutions
文摘Bi-directional static loading test adopting load cells is widely used around the world at present,with increase in diameter and length of deep foundations.In this paper,a new simple conversion method to predict the equivalent pile head load-settlement curve considering elastic shortening of deep foundation was put forward according to the load transfer mechanism.The proposed conversion method was applied to root caisson foundation in a bridge and to large diameter pipe piles in a sea wind power plant.Some new load cells,test procedure,and construction technology were adopted based on the applications to different deep foundations,which could enlarge the application scopes of bi-directional loading test.A new type of bi-directional loading test for pipe pile was conducted,in which the load cell was installed and loaded after the pipe pile with special connector has been set up.Unlike the conventional bi-directional loading test,the load cell can be reused and shows an evident economic benefit.
基金Project(50490272 ,50490274 ,10472134) supported by the Natural Science Foundation of China project(2005038250)supported by the China Postdoctoral Foundation
文摘According to the catastrophe model for impact buckling of static loading structures, a new catastrophe model for impact loading failure of a static loading rock system was established, and one dimension (1D) catastrophe model was analyzed. The analysis results indicate that the furcation collection where catastrophe may take place is not only decided by mechanical system itself but also relates to exterior loading, which is different from the results obtained under mono-static loading where the bifurcation collection is only determined by mechanics of the system itself and has nothing to do with exterior loading. In addition, the corresponding 1D coupled static-dynamic loading experiment is designed to verify the analysis results of catastrophe model. The test is done with Instron 1342 electro-servo controlled testing system, in which medium strain rate is caused by monotony rising dynamic load. The parameters are obtained combining theoretical model with experiment. The experimental and theoretical curves of critical dynamic load vs static load are rather coincided, thus the new model is proved to be correct.
文摘Seismic method is usually used for elastic parametric estimation. This is why this method presents dynamic parameters of Earth. Frequency seismic range changes greatly from geodynamic modelling time. Now we have opportunity to use geodesy result for some years for elastic parameters estimation. Static solution from elastic theory may be used for the interpretation of long term results. It presents static elastic parameter. The inverse problem for different types of vertical surface loading on one year period is calculated. Two cases of loading with maximal and minimal area are presented. Results are determined by space geodesy and leveling methods. Current relation between atmospheric pressure and vertical displacements was estimated at the center of Siberian Anti Cyclone with size varied from 2000 km to 3000 kin. Pressure-displacement coefficients （PDC） can be achieved by three years obser- vation （0.997 mm/mbar for NVSK GPS station）. It is used for elastic module study of geology medium with maximum thickness up to 600 km. In the context of elastic model, the modulus of rigidity is estimated to be 113 GPa. Vast expanse of anti-cyclone may relate with rheology of crust and upper mantle. Smaller size of surface loading - local loading is seasonal variation of water reservoir. Annual vertical changes were obtained by leveling near the dam of the reservoir. PDC ratio was 1.15 mm/bar for these places. In elastic theory, the Young modulus E = 80 GPa （Poisson ratio = 0.25, the modulus of rigidity - 32 GPa） was calculated by sixteen years of leveling measurements. This result can effectively be represented for upper crust. Our results were checked by solution for coseismic displacement of Chyia- Altai earthquake （Sep. 27, 2003, M = 7.3）. Coseismic results calculated by static modules agree with experimental coseismic GPS data at 10% level.
文摘An eight-channel force loading system is presented, which adopts position control system and force control system switching model, small flow servo valve controlled capacious cylinder system scheme, intelligent PID algorithm and distributed load approach. Through the analyses of the equivalent model of valve controlled cylinder force subsystem, a controller based on intelligent PID algorithm is designed, which is not sensitive to the variation of parameters such as environmental stiffness. According to the coupling of multiple load channels, a distributed load approach is employed in the superior monitor computer. Experimental results show that the system designed has high precision and robustness.
基金provided by the National Natural Science Foundation of China(52074300)the Program of China Scholarship Council(202206430024)+2 种基金the National Natural Science Foundation of China Youth Science(52104139)Yueqi Young Scholars Project of China University of Mining and Technology Beijing(2602021RC84)Guizhou province science and technology planning project([2020]3007,[2020]3008)。
文摘The deep mining of coal resources is accompanied by severe environmental challenges and various potential engineering hazards.The implementation of NPR(negative Poisson's ratio)bolts are capable of controlling large deformations in the surrounding rock effectively.This paper focuses on studying the mechanical properties of the NPR bolt under static disturbance load.The deep nonlinear mechanical experimental system was used to study the mechanical behavior of rock samples with different anchored types(unanchored/PR anchored/2G NPR anchored)under static disturbance load.The whole process of rock samples was taken by high-speed camera to obtain the real-time failure characteristics under static disturbance load.At the same time,the acoustic emission signal was collected to obtain the key characteristic parameters of acoustic emission such as acoustic emission count,energy,and frequency.The deformation at the failure of the samples was calculated and analyzed by digital speckle software.The findings indicate that the failure mode of rock is influenced by different types of anchoring.The peak failure strength of 2G NPR bolt anchored rock samples exhibits an increase of 6.5%when compared to the unanchored rock samples.The cumulative count and cumulative energy of acoustic emission exhibit a decrease of 62.16%and 62.90%,respectively.The maximum deformation of bearing capacity exhibits an increase of 59.27%,while the failure time demonstrates a delay of 42.86%.The peak failure strength of the 2G NPR bolt anchored ones under static disturbance load exhibits an increase of 5.94%when compared to the rock anchored by PR(Poisson's ratio)bolt.The cumulative count and cumulative energy of acoustic emission exhibit a decrease of 47.16%and 43.86%,respectively.The maximum deformation of the bearing capacity exhibits an increase of 50.43%,and the failure time demonstrates a delay of 32%.After anchoring by 2G NPR bolt,anchoring support effectively reduces the risk of damage caused by static disturbance load.These results demonstrate that the support effect of 2G NPR bolt materials surpasses that of PR bolt.
基金Project(2018YFC0604703)supported by the National Key R&D Program of ChinaProjects(51804181,51874190)supported by the National Natural Science Foundation of China+3 种基金Project(ZR2018QEE002)supported by the Shandong Province Natural Science Fund,ChinaProject(ZR2018ZA0603)supported by the Major Program of Shandong Province Natural Science Foundation,ChinaProject(2019GSF116003)supported by the Key R&D Project of Shandong Province,ChinaProject(SDKDYC190234)supported by the Shandong University of Science and Technology,Graduate Student Technology Innovation Project,China。
文摘The stability control of surrounding rock for large or super-large section chamber is a difficult technical problem in deep mining condition.Based on the in-site geological conditions of Longgu coal mine,this paper used the dynamic module of FLAC3D to study the response characteristics of deep super-large section chamber under dynamic and static combined loading condition.Results showed that under the static loading condition,the maximum vertical stress,deformation and failure range are large,where the stress concentration coefficient is 1.64.The maximum roof-to-floor and two-sides deformations are 54.6 mm and 53.1 mm,respectively.Then,under the dynamic and static combined loading condition:(1)The influence of dynamic load frequency on the two-sides is more obvious;(2)The dynamic load amplitude has the greatest influence on the stress concentration degree,and the plastic failure tends to develop to the deeper;(3)With the dynamic load source distance increase,the response of surrounding rock is gradually attenuated.On this basis,empirical equations for each dynamic load conditions were obtained by using regression analysis method,and all correlation coefficients are greater than 0.99.This research provided reference for the supporting design of deep super-large section chamber under same or similar conditions.
基金Supported by National Natural Science Foundation of China(No.10472134 and No.50490274)
文摘By means of the improved split Hopkionson pressure bar(SHPB) with axial pre-pressure and confined pressure, two series of experiments on sandstone are carried out to research the failure mode of rock during the course of exploitation of resources in deep. One is under the conditions that the con-fining pressure is fixed and the axial pressure is changeable. The other is under the conditions that the confining pressure becomes and the axial pressure is fixed. It is found that samples break up evenly after impacting when axial static pressures are low, there is great disparity in size of fragments when axial static pressures are high, and the main bodies of samples after the tests under the combination of dy-namic and static loads frequently show the type of V or X. The samples are more close-grained at the elastic stage and impacts make many cracks be generated and developed, as makes samples more crackable. At the initial phase of damage stage, the static pressures make some cracks in the samples which are undeveloped and the impacts′ role is similar to that at the elastic stage. At the metaphase or anaphase of damage stage, these cracks in the samples develop adequately and the impacts mainly accelerate samples′ failure. The main bodies of samples show the type of V or X after impacting due to the confining pressures′ restraining samples′ lateral formation at the elastic stage or the initial phase of damage stage, the main bodies of samples have almost formed at the stage loading static pressures and the results after impacting usually are similar to those under the axial pressures tests.
基金the financial support from the National Natural Science Foundation of China(Nos.52374094,52174122 and 52374218)Excellent Youth Fund of Shandong Natural Science Foundation(No.ZR2022YQ49)Taishan Scholar Project in Shandong Province(Nos.tspd20210313 and tsqn202211150)。
文摘The stability control of fissured rock is difficult,especially under static and dynamic loads in deep coal mines.In this paper,the dynamic mechanical properties,strain rate evolution and energy dissipation of fissured and anchored rocks were respectively obtained by SHPB tests.It was found that bolt can provide supporting efficiency-improving effect for fissured rock against dynamic disturbance,and this effect increased quadratically with decrease in anchoring angles.Then,the energy dissipation mechanism of anchored rock was obtained by slipping model.Furthermore,bolt energy-absorbing mechanism by instantaneous tensile-shear deformation was expressed based on material mechanics,which was the larger the anchoring angle,the smaller the energy absorption,and the less the contribution to supporting efficiency improvement.On this basis,the functional relationship between energy dissipation of anchored rock and energy absorption of bolt was established.Taking the coal-gangue separation system of Longgu coal mine as an example,the optimal anchoring angle can be determined as 57.5°–67.5°.Field monitoring showed fissured rock with the optimal anchoring angle,can not only effectively control the deformation,but also fully exert the energy-absorbing and efficiency-improving effect of bolt itself.This study provides guidance to the stability control and supporting design for deep engineering under the same or similar conditions.
基金supported by the National Natural Science Foundation of China(Nos.52074151,51927807,and 52274123)Tiandi Science and Technology Co.,Ltd.(No.2022-2-TDMS012)。
文摘This study explores the effects of dynamic and static loading on rock bolt performance a key factor in maintaining the structural safety of coal mine roadways susceptible to coal bursts.Employing a housemade load frame to simulate various failure scenarios,pretension-impact-pull tests on rock bolts were conducted to scrutinize their dynamic responses under varied static load conditions and their failure traits under combined loads.The experimental results denote that with increased impact energy,maximum and average impact loads on rock bolts escalate significantly under pretension,initiating plastic deformation beyond a certain threshold.Despite minor reductions in the yield load due to impactinduced damage,pretension aids in constraining post-impact deformation rate and fluctuation degree of rock bolts.Moreover,impact-induced plastic deformation causes internal microstructure dislocation,fortifying the stiffness of the rock bolt support system.The magnitude of this fortification is directly related to the plastic deformation induced by the impact.These findings provide crucial guidance for designing rock bolt support in coal mine roadway excavation,emphasizing the necessity to consider both static and dynamic loads for improved safety and efficiency.
文摘The effects of microstructure on quasi-static transverse loading behavior of 3D circular braided composite tubes were studied. Transverse loading tests were conducted. Transverse load-deflection curves were obtained to analyze the effects of braiding parameters including the braiding angle, the wall thickness, and the diameter on the transverse loading of 3D circular braided composite tubes. Breaking loads, moduli and strengths had also been used to describe the transverse loading behaviors. The failure morphologies were shown to reveal damage mechanisms. From the results, the increase in braiding angle, wall thickness and diameter increases the ability of anti-deformation and breaking load of braided tubes. The breaking load of specimen with a braiding angle of 45° is about 1.68 times that of specimen with a braiding angle of 15°. The breaking load of specimen with 4 layers of yarns is about 2.15 times that of specimen with 2 layers of yarns. The breaking load of the tube with a diameter of 25.5 mm is about 2.39 times that of the tube with a diameter of 20.5 mm.
基金supported by the Steel Structure Research and Education Promotion Project of the Japan Iron and Steel Federation in FY2016.
文摘The present paper investigates the collapse process of a pipe-framed greenhouse under static wind loading based on a non-linear finite element analysis.The purpose is to establish a more reasonable wind resistant design method for such structures.The structures are so flexible that the fluid-structure interaction(FSI)is considered in the analysis.In practice,iterative analyses of the structure’s response and the wind pressure distribution on the deformed structure are made.The wind direction is normal to the ridge.Computational fluid dynamics(CFD)analysis with a RANS turbulence model is used for evaluating the time-averaged wind pressure coefficient distribution on the structure.Both the geometric and the material non-linearity are considered in the structural analysis.The collapse behavior obtained is consistent with the practical one often observed in damage investigations.Based on the results,discussion is made of the validity of the current design guideline commonly used in Japan.The same analysis is carried out for various reinforced models.The effect of each reinforcement method on the improvement of wind resistance of the structure is investigated on the basis of the allowable stress and deformation limits specified in the current design guideline.
文摘This article uses real engineering projects as examples to analyze how static load test technology is applied in testing the bridge-bearing capacity.The analysis covers aspects such as testing section layout,test load and efficiency coefficient,loading plan,evaluation optimization,test result modification,and result evaluation.The aim is to support the accurate detection and evaluation of bridge-bearing capacity.
基金Scientific and Technological Development Project of China Railway Design Group Co.,Ltd.(No.2022A02480005)Technology Development Project of China Railway Design Group Co.,Ltd.(No.2023A0248001).
文摘China's railway prestressed concrete bridge has more than 600000 holes,prestressed engineering is a key force system affecting the safety and durability of the prestressed concrete bridge structure,its construction quality is easily affected by traditional manual operation technology,resulting in low construction efficiency and control accuracy,easy to form a hidden danger of quality and safety,it is difficult to meet the needs of less humanized,standardized intelligent construction trend.Based on the research on the intelligent prestressed construction control and testing technology and equipment for railway bridges,this paper proposes the integration of intelligent prestressed tension control and tunnel friction test of railway bridges,intelligent grouting control of tunnel and intelligent testing of beam construction quality,and sets up a complete technical system and integrated equipment for intelligent prestressed construction of bridges based on the industrial Internet of Things(IoT).Overall,improve the quality and efficiency of bridge production,construction,and management.
基金supported by the National Natural Science Foundation of China (Grant No.52279116)the Key Projects of the Yalong River Joint Fund of the National Natural Science Foundation of China (Grant No.U1865203).
文摘Seismicity resulting from the near-or in-field fault activation significantly affects the stability of large-scale underground caverns that are operating under high-stress conditions.A comprehensive scientific assessment of the operational safety of such caverns requires an in-depth understanding of the response characteristics of the rock mass subjected to dynamic disturbances.To address this issue,we conducted true triaxial modeling tests and dynamic numerical simulations on large underground caverns to investigate the impact of static stress levels,dynamic load parameters,and input directions on the response characteristics of the surrounding rock mass.The findings reveal that:(1)When subjected to identical incident stress waves and static loads,the surrounding rock mass exhibits the greatest stress response during horizontal incidence.When the incident direction is fixed,the mechanical response is more pronounced at the cavern wall parallel to the direction of dynamic loading.(2)A high initial static stress level specifically enhances the impact of dynamic loading.(3)The response of the surrounding rock mass is directly linked to the amplitude of the incident stress wave.High amplitude results in tensile damage in regions experiencing tensile stress concentration under static loading and shear damage in regions experiencing compressive stress concentration.These results have significant implications for the evaluation and prevention of dynamic disasters in the surrounding rock of underground caverns experiencing dynamic disturbances.
基金funded by the Federal Ministry for Economic Affairs and Climate Action as part of the Technology Transfer Program Lightweight Construction(Grant no.03LB1000A).
文摘Lightweight structures for gears enable a reduction in material usage while maintaining the technical function of the gear.Previous approaches have pursued the strategy of lightweight structures in the gear wheel body.By taking inspiration from biological models and utilizing material savings in the gear rim,new design approaches for the lightweight design of gears can be realized.For this reason,a holistic biological design approach for spur gears is presented.In addition to the method of topology optimization,a biologically inspired approach based on diatoms is introduced,which achieves a weight reduction of over 50%compared to conventional solid gears.Diatom structures are extracted from the oceans,digitally modelled,and adapted to the load conditions of a reference gear by parametric design and simulation optimization.For the experimental validation of the design,a manufactured gear is statically loaded in the nominal load range and analyzed using a tactile geometry gear measurement.The measurement results of selected standard gear parameters show that the gear does not exhibit any plastic deformation for the nominal load capacity of 383 Nm,validating the presented design approach.
基金supported by the National Natural Science Foundation of China(Nos.52374100,52525401,and 52304150)Outstanding Young Talent Project of Shanxi Province(No.SJYC2024301)Research Project Supported by Shanxi Scholarship Council of China(No.2023-041).
文摘Borehole pressure relief helps prevent rock bursts.However,this may change the physical and mechan-ical properties of the surrounding rock,affect the variation of the plastic zone of the roadway,and lead to the failure of roadway support,thus threatening the safety of the roadway.In this paper,the variable angle shear test of drilled specimens under the action of static and dynamic loads is used to study the evolution of mechanical parameters of the specimens and their influence on the plastic zone of the sur-rounding rock.The shear strength decreases linearly with the increase of drilling diameter.With the increase of pre-static load level and dynamic load amplitude,the cohesion first increases and then decreases,and the internal friction angle decreases.Moreover,the shear failure surface changes from rough to smooth.The reasons include that the static load enhances the tooth cutting effect and the repeated friction of cracks caused by the dynamic load.Borehole pressure relief leads to an increase in the radius of the plastic zone of the surrounding rock following a quadratic function.The research results of this paper provide a theoretical basis for designing drilling unloading parameters and supporting parameters for rock burst roadways.
基金Financial supports from the Natural Sciences and Engineering Research Council(NSERC)of Canada(CRDPJ 418932-11)Vale,LKAB,CEMI,MIRARCO,and the Open Research Fund of the State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(Grant No.Z015001)for this work are gratefully acknowledged
文摘The presence of geological structures such as faults, joints, and dykes has been observed near excavation boundaries in many rockburst case histories. In this paper, the role of discontinuities around tunnels in rockburst occurrence was studied. For this purpose, the Abaqus explicit code was used to simulate dynamic rock failure in deep tunnels. Material heterogeneity was considered using Python scripting in Abaqus. Rockbursts near fault regions in deep tunnels under static and dynamic loads were studied.Several tunnel models with and without faults were built and static and dynamic loads were used to simulate rock failure. The velocity and the released kinetic energy of failed rocks, the failure zone around the tunnel, and the deformed mesh were studied to identify stable and unstable rock failures. Compared with models without discontinuities, the results showed that the velocity and the released kinetic energy of failed rocks were higher, the failure zone around the tunnel was larger, and the mesh was more deformed in the models with discontinuities, indicating that rock failure in the models with discontinuities was more violent. The modeling results confirm that the presence of geological structures in the vicinity of deep excavations could be one of the major influence factors for the occurrence of rockburst. It can explain localized rockburst occurrence in civil tunnels and mining drifts. The presented methodology in this paper for rockburst analysis can be useful for rockburst anticipation and control during mining and tunneling in highly stressed ground.
基金Supported by National Natural Science Foundation of China(Grant No11472239)Hebei Provincial Natural Science Foundation of China(Grant No.A2015203023)Key Project of Science and Technology Research of Higher Education of Hebei Province of China(Grant No.ZD20131055)
文摘The rotating circular plate is widely used in mechanical engineering, meanwhile the plates are often in the electromagnetic field in modern industry with complex loads. In order to study the resonance of a rotating circular plate under static loads in magnetic field, the nonlinear vibration equation about the spinning circular plate is derived according to Hamilton principle. The algebraic expression of the initial deflection and the magneto elastic forced disturbance differential equation are obtained through the application of Galerkin integral method. By mean of modified Multiple scale method, the strongly nonlinear amplitude-frequency response equation in steady state is established. The amplitude frequency characteristic curve and the relationship curve of amplitude changing with the static loads and the excitation force of the plate are obtained according to the numerical calculation. The influence of magnetic induction intensity, the speed of rotation and the static loads on the amplitude and the nonlinear characteristics of the spinning plate are analyzed. The proposed research provides the theory reference for the research of nonlinear resonance of rotating plates in engineering.
文摘As a special geological phenomenon, the character of collapsible loess foundation is collapsible when penetrated by water. This character leads to the soil losing load bearing capacity largely and may lead to foundation failure. Pile is a popular foundation used in collapsible loess. The squeezed branch and plate pile is a new type of pile developed in recent years and has not be used in a project before. In this paper three squeezed branch and plate piles are tested in collapsible loess after immersion processing. The results may be used for reference in similar construction project, and to provide theoretical references for de- signing of the squeezed branch and plate piles in engineering practice.
基金Projects (10872218, 50934006) supported by the National Natural Science Foundation of ChinaProject (2010CB732004) supported by National Basic Research Program of ChinaProject (2011ssxt276) supported by the Central South University Innovation Fund, China
文摘The failure characteristics under coupled static and dynamic loading were investigated by the improved split Hopkinson pressure bar （SHPB） with axial pre-pressure and confining pressure. The results show that the stress—strain curve of the rock under static-dynamic coupled loading is a typical class I curve when the dynamic load is comparatively high; With the decrease of the dynamic load, the stress—strain curve transforms to a typical class II curve. The dynamic failure process was recorded by high-speed photography. Analyses of fracture surface morphology show that the failure modes of specimens are tensile failure or combined shear failure when the impact load energy is low, but the failure modes of specimens become tensile failure when the impact load energy is high. The results of fractal dimension show that the elastic potential energy release leads to increase in the degree of crushing of samples when the energy of impact load is low under coupled static and dynamic loads with high stress.
