Hydraulic stimulation technology is widely employed to enhance the permeability of geothermal reservoirs.Nevertheless,accurately predicting hydraulic fracture propagation in complex geological conditions remains chall...Hydraulic stimulation technology is widely employed to enhance the permeability of geothermal reservoirs.Nevertheless,accurately predicting hydraulic fracture propagation in complex geological conditions remains challenging,thereby hindering the effective utilization of existing natural fractures.In this study,a phase field model was developed utilizing the finite element method to examine the influence of fluid presence,stress conditions,and natural fractures on the initiation and propagation of hydraulic fractures.The model employs Biot's poroelasticity theory to establish the coupling between the displacement field and the fluid field,while the phase field theory is applied to simulate fracture behavior.The results show that whenσ_(x0)/σ_(y0)<3 or qf<20 kg/(m^(3)·s),the presence of natural fractures can alter the original propagation direction of hydraulic fractures.Conversely,in the absence of these conditions,the propagation path of natural fractures is predominantly influenced by the initial stress field.Furthermore,based on the analysis of breakdown pressure and damage area,the optimal intersection angle between natural fractures and hydraulic fractures is determined to range from 45°to 60°.Finally,once a dominant channel forms,initiating and propagating hydraulic fractures in other directions becomes increasingly difficult,even in highly fractured areas.This method tackles the challenges of initiating and propagating hydraulic fractures in complex geological conditions,providing a theoretical basis for optimizing Enhanced Geothermal System(EGS)projects.展开更多
During fully mechanized caving mining of thick coal seams,a large amount of strain energy accumulates in the roof,especially when the roof is thick and hard,making it difficultfor the roof to collapse naturally.When t...During fully mechanized caving mining of thick coal seams,a large amount of strain energy accumulates in the roof,especially when the roof is thick and hard,making it difficultfor the roof to collapse naturally.When the roof eventually collapses,the accumulated energy is released instantaneously,exerting a strong impact on the roadway.To address this issue,we proposed the synergistic control method of directional comprehensive pressure relief and energy-absorbing support(PREA)for roadways with hard roofs.In this study,we developed a three-dimensional physical model test apparatus for roof cutting and pressure relief.The 122108 ventilation roadway at the Caojiatan Coal Mine,which has a thick and hard roof,was taken as the engineering example.We analyzed the evolution patterns of stress and displacement in both the stope and the roadway surrounding rocks under different schemes.The PREA reinforcement mechanism for the roadway was investigated through comparative model tests between the new and original methods.The results showed that,compared to the original method,the new method reduced surrounding rock stress by up to 60.4%,and the roadway convergence decreased by up to 52.1%.Based on these results,we proposed corresponding engineering recommendations,which can guide fieldreinforcement design and application.The results demonstrate that the PREA method effectively reduces stress and ensures the safety and stability of the roadway.展开更多
KeLa-2 gas reservoir is the largest uncompartimentalized gas field so far discovered in China, with a reserve of hundreds of billions of cubic meters of dry gas. It has such features as extremely long interval (550m)...KeLa-2 gas reservoir is the largest uncompartimentalized gas field so far discovered in China, with a reserve of hundreds of billions of cubic meters of dry gas. It has such features as extremely long interval (550m), high pressure (74.5MPa) and pressure coefficient (2.022). Gas reservoirs with a pressure coefficient of over 2.0 are not commonly found. The abnormal high-pressure reservoirs are quite different in characteristic and performance during the process of depletion exploitation. Therefore, it is necessary to know the property of pressure sensitivity for this abnormal high-pressure reservoir. The aim of this paper is to test the reservoir pressure sensitivity and to analyze its effect on the deliverability of gas. Through some experiments, the permeability change with the confining pressure of rock samples from KeLa-2 abnormal high-pressure gas reservoir is measured. A power function is used to match the measured data, and to derive an empirical equation to describe the change of permeability through the change of the reservoir pressure or effective overburden pressure. Considering the permeability change during the development of reservoirs, a conventional deliverability equation is modified, and the deliverability curve for KeLa-2 gas reservoir is predicted. The research indicates that the extent of the pressure sensitivity of rock samples from KeLa-2 is higher than that from the Daqing oilfield. KeLa-2 reservoir rock has the feature of an undercompaction state. The pressure sensitivity of a reservoir may decrease the well deliverability. It is concluded that for KeLa-2 reservoir the predicted absolute open flow (AOF), when the pressure sensitivity is taken into account, is approximately 70% of the AOF when permeability is constant and does not change with pressure.展开更多
During the test on transient pressure signal in explosion field,false trigger caused by field interference can lead to test failure.To improve the stability of test system,a signal detection and recognition technology...During the test on transient pressure signal in explosion field,false trigger caused by field interference can lead to test failure.To improve the stability of test system,a signal detection and recognition technology is proposed for transient pressure test system.In the process of signal acquisition,firstly,electrical levels are monitored in real time to find effective abrupt changes and mark them;then the effective data segments are detecdted totected;thus the effective signals can be acquired in turn finally.The experimental results show that the shock wave signal can be collected effectively and the reliability of the test system can be improved after removal of interferences.展开更多
For the shock wave overpressure signal measurement of explosion field, the type and equivalent of the ammunition as well as the distance from test nodes to ground zero have a great influence on the characteristics of ...For the shock wave overpressure signal measurement of explosion field, the type and equivalent of the ammunition as well as the distance from test nodes to ground zero have a great influence on the characteristics of shock wave signal. To ensure that shock wave signal with different characteristic parameters can be collected completely in the test of shooting range, a tran- sient pressure signal storage system with configurable parameters is presented. In order to meet the requirements of different test nodes, the system can set parameters of all test nodes by wireless communication in explosion field. The feasibility and re- liability of the system are fully verified through transient pressure measurement in explosion field.展开更多
Aiming at harsh environment of cluster bombs center tube explosion dispersion and difficulties in installation of traditional test systems,a storage test system based on 16-bit ultra-low power microcontroller MSP430 i...Aiming at harsh environment of cluster bombs center tube explosion dispersion and difficulties in installation of traditional test systems,a storage test system based on 16-bit ultra-low power microcontroller MSP430 is designed in order to acquire gas pressure during cluster bombs dispersion.To meet the requirement of low power consumption,the working states of system＇s modules during data acquisition are elaborated and the equation to calculate the gas pressure change during cylindrical center tube opening the hatch is deduced.The field test is conducted and good test results are obtained.展开更多
A significant temperature raise within hydrogen vehicle cylinder during the fast filling process will be observed, while the strength and fatigue life of the cylinder will dramatically decrease at high temperature. In...A significant temperature raise within hydrogen vehicle cylinder during the fast filling process will be observed, while the strength and fatigue life of the cylinder will dramatically decrease at high temperature. In order to evaluate the strength and fatigue of composite hydrogen storage vessel, a 70-MPa fatigue test system using hydrogen medium was set up. Experimental study on the fatigue of composite hydrogen storage vessels under real hydrogen environment was performed. The experimental results show that the ultimate strength and fatigue life both decreased obviously compared with the values under hydraulic fatigue test. Furthermore, fatigue property, failure behavior, and safe hydrogen charging/discharging working mode of onboard hydrogen storage vessels were obtained through the fatigue tests.展开更多
The accuracy of fluctuating pressure test in wind tunnel is affected by the tube system. By employing contradistinctive experimental method, systematic study was conducted to investigate the effects of the tube system...The accuracy of fluctuating pressure test in wind tunnel is affected by the tube system. By employing contradistinctive experimental method, systematic study was conducted to investigate the effects of the tube system on fluctuating pressure. The analyzed tube system parameters include tube length, inside diameter, curvature, deflection angle, thickness, material, restrictor length,restrictor inside diameter, and restrictor place. It is found that all the tube system parameters mentioned above except tube curvature have non-negligible effects on fluctuating pressure. Based on the research results, test methods were presented for the fluctuating pressure measurement in low-speed wind tunnel, which can obviously improve the data accuracy but not lose test efficiency. The effectiveness of the method is verified by the wind tunnel test.展开更多
To obtain the vertical earth pressure on a soft foundation box culvert and investigate the interaction of the soil-culvert-foundation system, both a centrifugal model test and a numerical simulation were conducted and...To obtain the vertical earth pressure on a soft foundation box culvert and investigate the interaction of the soil-culvert-foundation system, both a centrifugal model test and a numerical simulation were conducted and the comparisons with the current methods to determine the load on a culvert were completed. The results of the model test and numerical analysis are in satisfactory agreement, which shows that the direction of the shear stress between the culvert and the adjacent embankment depends on the differential settlement between them. A vertical earth pressure concentration appears on the culvert with a rigid piles foundation because of a downward shear stress. The ratio of the load on a soft foundation culvert and the overburden pressure above the culvert raises first and then decreases as the backfill height increases. In order to reduce the load on a culvert, it is suggested to limit the stiffness difference of the foundations under the culvert and embankment and to use a light backfill over the culvert.展开更多
An in-situ test of bore pressure on a sheet-pile groin is carried out to investigate the characteristics of the bore pressure of fide in the Qian-tang River. The histories of bore pressure and the rule of the distribu...An in-situ test of bore pressure on a sheet-pile groin is carried out to investigate the characteristics of the bore pressure of fide in the Qian-tang River. The histories of bore pressure and the rule of the distribution of bore pressure on the sheet-pile groin are obtained through the test, which shows that the bore pressure on the sheet-pile groin are varies with time and space. The peak value of bore pressure on sheet-pile groin at different heights occurs almost at the same time. vertical distribution of bore pressure on the sheet-pile groin is linear above the still water level. The maximum bore pressure on the sheet-pile groin occurs at the still water level. Then a numerical method is also used to further study the characteristics of bore pressure. The standard k - ε turbulence model and VOF （volume of fluid） method for surface tracking are used to simulate the bore against the sheet-pile groin. The numerical results show flow fields, the position of free surface and time history and spatial distribution of bore pressure on the sheet-pile groin. The numerical and test resuits show good agreement.展开更多
Biogas is a kind of regenerable energy which is inexpensive and friendly to the environment, but the potential ofbiogas is difficult to develop fully in China, for most biogas have badly qualities and the utilization ...Biogas is a kind of regenerable energy which is inexpensive and friendly to the environment, but the potential ofbiogas is difficult to develop fully in China, for most biogas have badly qualities and the utilization of it is monotonous. The suitable operation term about biogas upgrading by pressurized water scrubbing was researched through the orthogonal test in this study. Two sorts of scrubber packing included the random multidimensional hollow sphere packing and the structured screen packing were also used, and the effects of experiment factors included packing, water temperature, gas flow speed, water flow speed and washing pressure were studied. The results showed that better effect was got when the screen structured packing was used; all the five test factors affected the processing significantly in the arrange as before and had better and better significant effects.展开更多
Given the problem of the long time required for testing gas pressure, we propose a fast-test method in which we used a technique of fast borehole sealing and air replenishing. Based on the characteristics of gas emiss...Given the problem of the long time required for testing gas pressure, we propose a fast-test method in which we used a technique of fast borehole sealing and air replenishing. Based on the characteristics of gas emission from boreholes to be tested, we built a theoretical model for calculating parameters during the process of increasing natural pressure and aeration. Using this model, we investigated the effect of different aeration conditions on velocity of pressure tests. The result shows that: 1) aerating air into boreholes can speed up gas pressure tests and 2) the more similar the pressure of the aerated air to the original gas pressure, the smaller the gas volume absorbed by coal and the shorter the time needed in pressure test. A case study in the Lu’an mining area shows that the time needed for gas pressure test is only 4 h using our method of aeration and 29 h under conditions of increasing natural pressure, saving time by 86.2%. This case study also indicates that, by using the aeration method, only one hour is needed for gas pressure to reach a stable state, which breaks the record of the shortest time needed for gas pressure tests in China.展开更多
With the increase of underground engineering construction depth,the phenomenon of surrounding rock sudden failure caused by supporting structure failure occurs frequently.The conventional unloading con-fining pressure...With the increase of underground engineering construction depth,the phenomenon of surrounding rock sudden failure caused by supporting structure failure occurs frequently.The conventional unloading con-fining pressure(CUCP)test cannot simulate the plastic yielding and instantaneous unloading process of supporting structure to rock.Thus,a high stress loading-instantaneous unloading confining pressure(HSL-IUCP)test method was proposed and applied by considering bolt’s fracture under stress.The wall thickness of confining pressure plates and the material of bolts were changed to realize different confin-ing pressure loading stiffness(CPLS)and lateral maximum allowable deformation(LMAD).The superio-rity of HSL-ICPU method is verified compared with CUCP.The rock failure mechanism caused by sudden failure of supporting structure is obtained.The results show that when CPLS increases from 1.35 to 2.33 GN/m,rock’s peak strength and elastic modulus increase by 25.18%and 23.70%,respectively.The fracture characteristics change from tensile failure to tensile-shear mixed failure.When LMAD decreases from 0.40 to 0.16 mm,rock’s residual strength,peak strain,and residual strain decrease by 91.80%,16.94%,and 21.92%,respectively,and post-peak drop modulus increases by 140.47%.The test results obtained by this method are closer to rock’s real mechanical response characteristics compared with CUCP.展开更多
Based on the similarity theory, taking the horseshoe, city-gate and round linings as examples, the value and distribution regularities of normal frost heaving pressures （hereinafter as frost heaving pressures） in tu...Based on the similarity theory, taking the horseshoe, city-gate and round linings as examples, the value and distribution regularities of normal frost heaving pressures （hereinafter as frost heaving pressures） in tunnels excavated in fractured rock mass in cold regions under different constraints and freezing depths were studied by a test model. It was found that the larger the frozen depth, the larger the frost heaving pressure, and the stronger the top constraint, the larger the frost heaving pressure. For the horseshoe lining and city-gate lining, the top constraint has a greater effect on the frost heaving pressures on the arch and the inverted arch. For the round lining, the influences of the top constraint on the frost heaving pressure in all linings are almost the same. The frost heaving pressure is maximum on the city-gate lining and minimal on the round lining. The largest frost heaving pressure all occur near the foot of the inverted arch for the three kinds of lining. Thus, the test data basically coincide with the observed in situ data.展开更多
Split Hopkinson pressure bar（SHPB） apparatus, usually used for testing behavior of material in median and high strain-rate, is now widely used in the study of rock dynamic constitutive relation, damage evolvement me...Split Hopkinson pressure bar（SHPB） apparatus, usually used for testing behavior of material in median and high strain-rate, is now widely used in the study of rock dynamic constitutive relation, damage evolvement mechanism and energy consumption. However, the possible reasons of sampling disturbance, machining error and so on often lead to the scattering of test results, and bring ultimate difficulty for forming general test conclusion. Based on the stochastic finite element method, the uncertain parameters of specimen density ps, specimen radius Rs, specimen elastic modulus Es and specimen length Ls in the data processing of SHPB test were considered, and the correlation between the parameters and the test results was analyzed. The results show that the specimen radius Rs has direct correlation with the test result, improving the accuracy in preparing and measuring of specimen is an effective way to improve the accuracy of test and minish the scattering of results for SHPB test.展开更多
This paper experimentally investigates the wave pressure and pore pressure within a sandy seabed around two pipelines under the action of random waves(currents).The experiments revealed that when the random wave plus ...This paper experimentally investigates the wave pressure and pore pressure within a sandy seabed around two pipelines under the action of random waves(currents).The experiments revealed that when the random wave plus current cases are compared with the random wave-only case,the forward current promotes wave propagation,whereas the reversed backward current inhibits wave propagation.Furthermore,the wave pressure on the downstream pipeline decreases as the relative spacing ratio increases and increases as the diameter increases.However,alterations in the relative spacing ratio or dimensions of the downstream pipeline exert a negligible influence on the wave pressure of the upstream pipeline.Moreover,the relative spacing ratio between the pipelines and the dimensions of the pipelines considerably influence the pore pressure in the sand bed.When the relative spacing ratio remains constant,increasing the downstream pipeline diameter will increase the pore-water pressure of the soil below the downstream pipeline.展开更多
BACKGROUND The six-minute walk test(6MWT)allows to determine,in addition to the main parameters,the time of heart rate recovery(THRR),cardiac function,adaptation index(AI),which characterize the compensatory reserve o...BACKGROUND The six-minute walk test(6MWT)allows to determine,in addition to the main parameters,the time of heart rate recovery(THRR),cardiac function,adaptation index(AI),which characterize the compensatory reserve of patients with chronic heart failure(CHF).At the same time,the significance of these parameters in patients taking beta-blockers for CHF is insufficiently studied,taking into account the negative chronotropic effect of drugs.In this regard,it is relevant to identify factors that can characterize the compensatory capabilities of a patient with CHF during 6MWT,not related to the calculation of heart rate.AIM To identify hemodynamic indicators of the adaptive capabilities of patients with CHF during paired 6MWT depending on their intake of beta-blockers.METHODS Seventy-four patients with compensated CHF due to coronary heart disease and/or hypertension formed the main group,comprising 46 individuals who were taking beta-blockers,and a comparison group comprising 28 individuals who had not been taking beta-blockers for at least one month before 6MWT.All participants underwent Doppler echocardiography(DECG),paired 6MWT,with assessment of hemodynamic parameters before and after both the first and second test.AI,THRR,blood pressure variability(BPV)were calculated.Multivariate,correlation analyses,univariate analysis of variance were used.RESULTS There were no significant associations between adaptation characteristics and DECG parameters or functional class(FC)of CHF in patients of the main group.In the comparison group,the indicators of compensatory reserve were significantly and directly associated with left ventricular ejection fraction(LVEF),and inversely with FC CHF and cardiac cavity size.In both groups,a greater difference in systolic blood pressure between the end of the first and the beginning of the second 6MWT was significantly associated with a higher index of right ventricular systolic dysfunction(Tricuspid annular plane systolic excursion)and LVEF,as well as a smaller left ventricular size and mass,and a lower pulmonary artery systolic pressure in patients in the main group.CONCLUSION Systolic BPV,measured immediately after 6MWT and 20 minutes after its completion,can indirectly characterize the compensatory reserve in patients with CHF,regardless of their beta-blocker intake.展开更多
This study presents a numerical simulation of large-scale shaking table tests on a superstructure supported by a pile group installed in an inclined liquefiable site,fo-cusing on nonlinear interactions between piles a...This study presents a numerical simulation of large-scale shaking table tests on a superstructure supported by a pile group installed in an inclined liquefiable site,fo-cusing on nonlinear interactions between piles and the soil.A three-dimensional finite element model of a soil-pile superstructure system is developed using OpenSeesMP.The temporal and spatial evolution of the radial soil pressure around the pile is evaluated in both liquefied and nonlique-fied sites.Results show that the soil pressure around the pile is significantly influenced by site inclination and soil lateral spreading.In liquefied sites,the soil pressure in the ex-truded zone of the upstream pile is significantly higher than that in the diffused zone.However,higher pressure occurs in the diffused zone for nonliquefied sites.Correspond-ingly,the liquefaction state significantly influences the force characteristics of the pile group system.Additionally,the group effect is more pronounced in liquefied sites.The results also indicate that the soil pressure distribution around the piles is closely related to the relative pile-soil displace-ment and reveals different on-pile force mechanisms under varying site conditions.These findings offer valuable in-sights into the seismic design of pile foundations in inclined liquefied sites.展开更多
This paper introduces model test results of water pressure in a fault, which is located in a slope and 16 different conditions. The results show that the water pressures in fault can be expressed by a linear function,...This paper introduces model test results of water pressure in a fault, which is located in a slope and 16 different conditions. The results show that the water pressures in fault can be expressed by a linear function, which is similar to the theoretical model suggested by Hoek. Factors affecting water pressures are water level in tension crack, dip angle of fault, the height of filling materials and thickness of fault zone in sequence.展开更多
AIM:To compare the intraocular pressure(IOP)peaks and fluctuations using water drinking tests(WDTs)and mean diurnal IOP among Filipino patients with normal eyes and glaucoma suspectsMETHODS:This prospective study incl...AIM:To compare the intraocular pressure(IOP)peaks and fluctuations using water drinking tests(WDTs)and mean diurnal IOP among Filipino patients with normal eyes and glaucoma suspectsMETHODS:This prospective study included normal and glaucoma suspect patients.Each patient underwent both WDT and mean diurnal examination on separate visits.For mean diurnal examination,IOP was recorded every 2 h for 8 h while in WDT,IOP was recorded prior to WDT,and postWDT at 5,15,30,45,and 60 min.IOP peak was recorded as the highest IOP for both methods,and IOP fluctuation was recorded as highest IOP minus lowest IOP.RESULTS:With the comparison of diagnostic tests,both normal eyes and glaucoma suspect groups,the peak IOP was caught at 15 min.Comparative analysis of both groups also showed that the peak IOP measurements were statistically higher for the WDT compared to mean diurnal IOP(P=0.039,P=0.048 under normal group and P=0.032 and P=0.031 under glaucoma suspect group).Similarly,the WDT had a statistically higher mean IOP fluctuation score than the mean diurnal IOP method in both groups(P=0.003,P=0.011 under normal group;P=0.002 and P=0.005 under glaucoma suspect group).CONCLUSION:This study shows that WDT is a comparable diagnostic exam in predicting IOP fluctuations than mean diurnal measurement.WDT is a promising diagnostic procedure for risk assessment in glaucoma.展开更多
基金supported by the National Key Research and Development Program(2021YFB150740401)National Natural Science Foundation of China(42202336)the CAS Pioneer Hundred Talents Program in China(Y826031C01)。
文摘Hydraulic stimulation technology is widely employed to enhance the permeability of geothermal reservoirs.Nevertheless,accurately predicting hydraulic fracture propagation in complex geological conditions remains challenging,thereby hindering the effective utilization of existing natural fractures.In this study,a phase field model was developed utilizing the finite element method to examine the influence of fluid presence,stress conditions,and natural fractures on the initiation and propagation of hydraulic fractures.The model employs Biot's poroelasticity theory to establish the coupling between the displacement field and the fluid field,while the phase field theory is applied to simulate fracture behavior.The results show that whenσ_(x0)/σ_(y0)<3 or qf<20 kg/(m^(3)·s),the presence of natural fractures can alter the original propagation direction of hydraulic fractures.Conversely,in the absence of these conditions,the propagation path of natural fractures is predominantly influenced by the initial stress field.Furthermore,based on the analysis of breakdown pressure and damage area,the optimal intersection angle between natural fractures and hydraulic fractures is determined to range from 45°to 60°.Finally,once a dominant channel forms,initiating and propagating hydraulic fractures in other directions becomes increasingly difficult,even in highly fractured areas.This method tackles the challenges of initiating and propagating hydraulic fractures in complex geological conditions,providing a theoretical basis for optimizing Enhanced Geothermal System(EGS)projects.
基金supported by the National Natural Science Foundation of China(Grant Nos.U24A2088 and 42277174)the Fundamental Research Funds for the Central Universities,China(Grant No.2024JCCXSB01).
文摘During fully mechanized caving mining of thick coal seams,a large amount of strain energy accumulates in the roof,especially when the roof is thick and hard,making it difficultfor the roof to collapse naturally.When the roof eventually collapses,the accumulated energy is released instantaneously,exerting a strong impact on the roadway.To address this issue,we proposed the synergistic control method of directional comprehensive pressure relief and energy-absorbing support(PREA)for roadways with hard roofs.In this study,we developed a three-dimensional physical model test apparatus for roof cutting and pressure relief.The 122108 ventilation roadway at the Caojiatan Coal Mine,which has a thick and hard roof,was taken as the engineering example.We analyzed the evolution patterns of stress and displacement in both the stope and the roadway surrounding rocks under different schemes.The PREA reinforcement mechanism for the roadway was investigated through comparative model tests between the new and original methods.The results showed that,compared to the original method,the new method reduced surrounding rock stress by up to 60.4%,and the roadway convergence decreased by up to 52.1%.Based on these results,we proposed corresponding engineering recommendations,which can guide fieldreinforcement design and application.The results demonstrate that the PREA method effectively reduces stress and ensures the safety and stability of the roadway.
文摘KeLa-2 gas reservoir is the largest uncompartimentalized gas field so far discovered in China, with a reserve of hundreds of billions of cubic meters of dry gas. It has such features as extremely long interval (550m), high pressure (74.5MPa) and pressure coefficient (2.022). Gas reservoirs with a pressure coefficient of over 2.0 are not commonly found. The abnormal high-pressure reservoirs are quite different in characteristic and performance during the process of depletion exploitation. Therefore, it is necessary to know the property of pressure sensitivity for this abnormal high-pressure reservoir. The aim of this paper is to test the reservoir pressure sensitivity and to analyze its effect on the deliverability of gas. Through some experiments, the permeability change with the confining pressure of rock samples from KeLa-2 abnormal high-pressure gas reservoir is measured. A power function is used to match the measured data, and to derive an empirical equation to describe the change of permeability through the change of the reservoir pressure or effective overburden pressure. Considering the permeability change during the development of reservoirs, a conventional deliverability equation is modified, and the deliverability curve for KeLa-2 gas reservoir is predicted. The research indicates that the extent of the pressure sensitivity of rock samples from KeLa-2 is higher than that from the Daqing oilfield. KeLa-2 reservoir rock has the feature of an undercompaction state. The pressure sensitivity of a reservoir may decrease the well deliverability. It is concluded that for KeLa-2 reservoir the predicted absolute open flow (AOF), when the pressure sensitivity is taken into account, is approximately 70% of the AOF when permeability is constant and does not change with pressure.
基金The 11th Postgraduate Technology Innovation Project of North University of China(No.20141142)
文摘During the test on transient pressure signal in explosion field,false trigger caused by field interference can lead to test failure.To improve the stability of test system,a signal detection and recognition technology is proposed for transient pressure test system.In the process of signal acquisition,firstly,electrical levels are monitored in real time to find effective abrupt changes and mark them;then the effective data segments are detecdted totected;thus the effective signals can be acquired in turn finally.The experimental results show that the shock wave signal can be collected effectively and the reliability of the test system can be improved after removal of interferences.
基金The 11th Postgraduate Technological Innovation Project of North University of China(No.20141150)
文摘For the shock wave overpressure signal measurement of explosion field, the type and equivalent of the ammunition as well as the distance from test nodes to ground zero have a great influence on the characteristics of shock wave signal. To ensure that shock wave signal with different characteristic parameters can be collected completely in the test of shooting range, a tran- sient pressure signal storage system with configurable parameters is presented. In order to meet the requirements of different test nodes, the system can set parameters of all test nodes by wireless communication in explosion field. The feasibility and re- liability of the system are fully verified through transient pressure measurement in explosion field.
文摘Aiming at harsh environment of cluster bombs center tube explosion dispersion and difficulties in installation of traditional test systems,a storage test system based on 16-bit ultra-low power microcontroller MSP430 is designed in order to acquire gas pressure during cluster bombs dispersion.To meet the requirement of low power consumption,the working states of system＇s modules during data acquisition are elaborated and the equation to calculate the gas pressure change during cylindrical center tube opening the hatch is deduced.The field test is conducted and good test results are obtained.
文摘A significant temperature raise within hydrogen vehicle cylinder during the fast filling process will be observed, while the strength and fatigue life of the cylinder will dramatically decrease at high temperature. In order to evaluate the strength and fatigue of composite hydrogen storage vessel, a 70-MPa fatigue test system using hydrogen medium was set up. Experimental study on the fatigue of composite hydrogen storage vessels under real hydrogen environment was performed. The experimental results show that the ultimate strength and fatigue life both decreased obviously compared with the values under hydraulic fatigue test. Furthermore, fatigue property, failure behavior, and safe hydrogen charging/discharging working mode of onboard hydrogen storage vessels were obtained through the fatigue tests.
基金supported by the Pre-research Fund of Vibration and Noise Control Technology (No. 51334060101)
文摘The accuracy of fluctuating pressure test in wind tunnel is affected by the tube system. By employing contradistinctive experimental method, systematic study was conducted to investigate the effects of the tube system on fluctuating pressure. The analyzed tube system parameters include tube length, inside diameter, curvature, deflection angle, thickness, material, restrictor length,restrictor inside diameter, and restrictor place. It is found that all the tube system parameters mentioned above except tube curvature have non-negligible effects on fluctuating pressure. Based on the research results, test methods were presented for the fluctuating pressure measurement in low-speed wind tunnel, which can obviously improve the data accuracy but not lose test efficiency. The effectiveness of the method is verified by the wind tunnel test.
基金Project(2012AA112504) supported by the National High Technology Research and Development Program of ChinaProjects(51108048,51478054) supported by the National Natural Science Foundation of China
文摘To obtain the vertical earth pressure on a soft foundation box culvert and investigate the interaction of the soil-culvert-foundation system, both a centrifugal model test and a numerical simulation were conducted and the comparisons with the current methods to determine the load on a culvert were completed. The results of the model test and numerical analysis are in satisfactory agreement, which shows that the direction of the shear stress between the culvert and the adjacent embankment depends on the differential settlement between them. A vertical earth pressure concentration appears on the culvert with a rigid piles foundation because of a downward shear stress. The ratio of the load on a soft foundation culvert and the overburden pressure above the culvert raises first and then decreases as the backfill height increases. In order to reduce the load on a culvert, it is suggested to limit the stiffness difference of the foundations under the culvert and embankment and to use a light backfill over the culvert.
文摘An in-situ test of bore pressure on a sheet-pile groin is carried out to investigate the characteristics of the bore pressure of fide in the Qian-tang River. The histories of bore pressure and the rule of the distribution of bore pressure on the sheet-pile groin are obtained through the test, which shows that the bore pressure on the sheet-pile groin are varies with time and space. The peak value of bore pressure on sheet-pile groin at different heights occurs almost at the same time. vertical distribution of bore pressure on the sheet-pile groin is linear above the still water level. The maximum bore pressure on the sheet-pile groin occurs at the still water level. Then a numerical method is also used to further study the characteristics of bore pressure. The standard k - ε turbulence model and VOF （volume of fluid） method for surface tracking are used to simulate the bore against the sheet-pile groin. The numerical results show flow fields, the position of free surface and time history and spatial distribution of bore pressure on the sheet-pile groin. The numerical and test resuits show good agreement.
基金Supported by National Science and Technology Supporting Plan (2008BADC4B02)
文摘Biogas is a kind of regenerable energy which is inexpensive and friendly to the environment, but the potential ofbiogas is difficult to develop fully in China, for most biogas have badly qualities and the utilization of it is monotonous. The suitable operation term about biogas upgrading by pressurized water scrubbing was researched through the orthogonal test in this study. Two sorts of scrubber packing included the random multidimensional hollow sphere packing and the structured screen packing were also used, and the effects of experiment factors included packing, water temperature, gas flow speed, water flow speed and washing pressure were studied. The results showed that better effect was got when the screen structured packing was used; all the five test factors affected the processing significantly in the arrange as before and had better and better significant effects.
基金Project 2006CB202204-3 supported by the National Basic Research Program of China
文摘Given the problem of the long time required for testing gas pressure, we propose a fast-test method in which we used a technique of fast borehole sealing and air replenishing. Based on the characteristics of gas emission from boreholes to be tested, we built a theoretical model for calculating parameters during the process of increasing natural pressure and aeration. Using this model, we investigated the effect of different aeration conditions on velocity of pressure tests. The result shows that: 1) aerating air into boreholes can speed up gas pressure tests and 2) the more similar the pressure of the aerated air to the original gas pressure, the smaller the gas volume absorbed by coal and the shorter the time needed in pressure test. A case study in the Lu’an mining area shows that the time needed for gas pressure test is only 4 h using our method of aeration and 29 h under conditions of increasing natural pressure, saving time by 86.2%. This case study also indicates that, by using the aeration method, only one hour is needed for gas pressure to reach a stable state, which breaks the record of the shortest time needed for gas pressure tests in China.
基金the National Natural Science Foundation of China(Nos.52374218,52174122 and 52374094)Outstanding Youth Fund of Shandong Natural Science Foundation(No.ZR2022YQ49)Taishan Scholar Project in Shandong Province(Nos.tspd20210313 and tsqn202211150).
文摘With the increase of underground engineering construction depth,the phenomenon of surrounding rock sudden failure caused by supporting structure failure occurs frequently.The conventional unloading con-fining pressure(CUCP)test cannot simulate the plastic yielding and instantaneous unloading process of supporting structure to rock.Thus,a high stress loading-instantaneous unloading confining pressure(HSL-IUCP)test method was proposed and applied by considering bolt’s fracture under stress.The wall thickness of confining pressure plates and the material of bolts were changed to realize different confin-ing pressure loading stiffness(CPLS)and lateral maximum allowable deformation(LMAD).The superio-rity of HSL-ICPU method is verified compared with CUCP.The rock failure mechanism caused by sudden failure of supporting structure is obtained.The results show that when CPLS increases from 1.35 to 2.33 GN/m,rock’s peak strength and elastic modulus increase by 25.18%and 23.70%,respectively.The fracture characteristics change from tensile failure to tensile-shear mixed failure.When LMAD decreases from 0.40 to 0.16 mm,rock’s residual strength,peak strain,and residual strain decrease by 91.80%,16.94%,and 21.92%,respectively,and post-peak drop modulus increases by 140.47%.The test results obtained by this method are closer to rock’s real mechanical response characteristics compared with CUCP.
文摘Based on the similarity theory, taking the horseshoe, city-gate and round linings as examples, the value and distribution regularities of normal frost heaving pressures （hereinafter as frost heaving pressures） in tunnels excavated in fractured rock mass in cold regions under different constraints and freezing depths were studied by a test model. It was found that the larger the frozen depth, the larger the frost heaving pressure, and the stronger the top constraint, the larger the frost heaving pressure. For the horseshoe lining and city-gate lining, the top constraint has a greater effect on the frost heaving pressures on the arch and the inverted arch. For the round lining, the influences of the top constraint on the frost heaving pressure in all linings are almost the same. The frost heaving pressure is maximum on the city-gate lining and minimal on the round lining. The largest frost heaving pressure all occur near the foot of the inverted arch for the three kinds of lining. Thus, the test data basically coincide with the observed in situ data.
基金Projects(50490274, 50534030) supported by the National Natural Science Foundation of ChinaProject supported by the Natural Science Foundatin of Hunan Province, China
文摘Split Hopkinson pressure bar（SHPB） apparatus, usually used for testing behavior of material in median and high strain-rate, is now widely used in the study of rock dynamic constitutive relation, damage evolvement mechanism and energy consumption. However, the possible reasons of sampling disturbance, machining error and so on often lead to the scattering of test results, and bring ultimate difficulty for forming general test conclusion. Based on the stochastic finite element method, the uncertain parameters of specimen density ps, specimen radius Rs, specimen elastic modulus Es and specimen length Ls in the data processing of SHPB test were considered, and the correlation between the parameters and the test results was analyzed. The results show that the specimen radius Rs has direct correlation with the test result, improving the accuracy in preparing and measuring of specimen is an effective way to improve the accuracy of test and minish the scattering of results for SHPB test.
基金supported by the National Natural Science Foundation of China(Grant No.52271281)Shandong Provincial High-Level Talent Workstation,Shandong Province Natural Science Foundation Youth project(Grant No.ZR2023QE190)an Open funding project from the Key Laboratory of Ministry of Education for Coastal Disaster and Protection,Hohai University,China(Grant No.202206).
文摘This paper experimentally investigates the wave pressure and pore pressure within a sandy seabed around two pipelines under the action of random waves(currents).The experiments revealed that when the random wave plus current cases are compared with the random wave-only case,the forward current promotes wave propagation,whereas the reversed backward current inhibits wave propagation.Furthermore,the wave pressure on the downstream pipeline decreases as the relative spacing ratio increases and increases as the diameter increases.However,alterations in the relative spacing ratio or dimensions of the downstream pipeline exert a negligible influence on the wave pressure of the upstream pipeline.Moreover,the relative spacing ratio between the pipelines and the dimensions of the pipelines considerably influence the pore pressure in the sand bed.When the relative spacing ratio remains constant,increasing the downstream pipeline diameter will increase the pore-water pressure of the soil below the downstream pipeline.
基金Supported by Ministry of Health of the Russian Federation titled Development of a Hardware-Software Complex for the Non-Invasive Monitoring and Prediction of Circulatory Decompensation in Patients with Chronic Heart Failure,No.125030703255-7.
文摘BACKGROUND The six-minute walk test(6MWT)allows to determine,in addition to the main parameters,the time of heart rate recovery(THRR),cardiac function,adaptation index(AI),which characterize the compensatory reserve of patients with chronic heart failure(CHF).At the same time,the significance of these parameters in patients taking beta-blockers for CHF is insufficiently studied,taking into account the negative chronotropic effect of drugs.In this regard,it is relevant to identify factors that can characterize the compensatory capabilities of a patient with CHF during 6MWT,not related to the calculation of heart rate.AIM To identify hemodynamic indicators of the adaptive capabilities of patients with CHF during paired 6MWT depending on their intake of beta-blockers.METHODS Seventy-four patients with compensated CHF due to coronary heart disease and/or hypertension formed the main group,comprising 46 individuals who were taking beta-blockers,and a comparison group comprising 28 individuals who had not been taking beta-blockers for at least one month before 6MWT.All participants underwent Doppler echocardiography(DECG),paired 6MWT,with assessment of hemodynamic parameters before and after both the first and second test.AI,THRR,blood pressure variability(BPV)were calculated.Multivariate,correlation analyses,univariate analysis of variance were used.RESULTS There were no significant associations between adaptation characteristics and DECG parameters or functional class(FC)of CHF in patients of the main group.In the comparison group,the indicators of compensatory reserve were significantly and directly associated with left ventricular ejection fraction(LVEF),and inversely with FC CHF and cardiac cavity size.In both groups,a greater difference in systolic blood pressure between the end of the first and the beginning of the second 6MWT was significantly associated with a higher index of right ventricular systolic dysfunction(Tricuspid annular plane systolic excursion)and LVEF,as well as a smaller left ventricular size and mass,and a lower pulmonary artery systolic pressure in patients in the main group.CONCLUSION Systolic BPV,measured immediately after 6MWT and 20 minutes after its completion,can indirectly characterize the compensatory reserve in patients with CHF,regardless of their beta-blocker intake.
基金The National Science Fund for Distinguished Young Scholars (No. 52225807)。
文摘This study presents a numerical simulation of large-scale shaking table tests on a superstructure supported by a pile group installed in an inclined liquefiable site,fo-cusing on nonlinear interactions between piles and the soil.A three-dimensional finite element model of a soil-pile superstructure system is developed using OpenSeesMP.The temporal and spatial evolution of the radial soil pressure around the pile is evaluated in both liquefied and nonlique-fied sites.Results show that the soil pressure around the pile is significantly influenced by site inclination and soil lateral spreading.In liquefied sites,the soil pressure in the ex-truded zone of the upstream pile is significantly higher than that in the diffused zone.However,higher pressure occurs in the diffused zone for nonliquefied sites.Correspond-ingly,the liquefaction state significantly influences the force characteristics of the pile group system.Additionally,the group effect is more pronounced in liquefied sites.The results also indicate that the soil pressure distribution around the piles is closely related to the relative pile-soil displace-ment and reveals different on-pile force mechanisms under varying site conditions.These findings offer valuable in-sights into the seismic design of pile foundations in inclined liquefied sites.
基金This paper is supported by the Research Fund for the Doctoral Program of Higher Education of China.
文摘This paper introduces model test results of water pressure in a fault, which is located in a slope and 16 different conditions. The results show that the water pressures in fault can be expressed by a linear function, which is similar to the theoretical model suggested by Hoek. Factors affecting water pressures are water level in tension crack, dip angle of fault, the height of filling materials and thickness of fault zone in sequence.
文摘AIM:To compare the intraocular pressure(IOP)peaks and fluctuations using water drinking tests(WDTs)and mean diurnal IOP among Filipino patients with normal eyes and glaucoma suspectsMETHODS:This prospective study included normal and glaucoma suspect patients.Each patient underwent both WDT and mean diurnal examination on separate visits.For mean diurnal examination,IOP was recorded every 2 h for 8 h while in WDT,IOP was recorded prior to WDT,and postWDT at 5,15,30,45,and 60 min.IOP peak was recorded as the highest IOP for both methods,and IOP fluctuation was recorded as highest IOP minus lowest IOP.RESULTS:With the comparison of diagnostic tests,both normal eyes and glaucoma suspect groups,the peak IOP was caught at 15 min.Comparative analysis of both groups also showed that the peak IOP measurements were statistically higher for the WDT compared to mean diurnal IOP(P=0.039,P=0.048 under normal group and P=0.032 and P=0.031 under glaucoma suspect group).Similarly,the WDT had a statistically higher mean IOP fluctuation score than the mean diurnal IOP method in both groups(P=0.003,P=0.011 under normal group;P=0.002 and P=0.005 under glaucoma suspect group).CONCLUSION:This study shows that WDT is a comparable diagnostic exam in predicting IOP fluctuations than mean diurnal measurement.WDT is a promising diagnostic procedure for risk assessment in glaucoma.
