Altered rock,often encountered in major engineering projects,can seriously affect the stability of rocks and slopes surrounding deeply buried tunnels.This study addressed the alteration mechanism,alteration degree cla...Altered rock,often encountered in major engineering projects,can seriously affect the stability of rocks and slopes surrounding deeply buried tunnels.This study addressed the alteration mechanism,alteration degree classification,and mechanical parameters of altered rock in engineering project areas using field testing,thin slice identification,X-ray diffraction,and major element testing.Results showed that the altered rock types in the areas of the Pingjiang Pumped Storage Power Station,Hunan Province,and a diversion tunnel in northern Xinjiang Uygur Autonomous Region include biotite granodiorite,biotite monzogranite,and cataclastic granite,and that the main alteration mechanisms are chloritization of biotite and clayization of feldspar minerals.The altered rocks were classified as slightly,moderately,or strongly altered according to their apparent characteristics,rebound value,longitudinal wave velocity,metamorphic mineral content,and porosity.The bulk density,elastic modulus,cohesion,and internal friction angle(Poisson’s ratio)of the altered rocks decreased(increased)with increase in the degree of alteration.Numerical simulations showed that in altered rock slope areas,the zone of strong rock alteration and the moderate-strong alteration contact zone exhibit locally large deformations that represent a certain hazard to engineering projects.These results provide valuable guidance and support for major projects in altered rock areas.展开更多
The bulge test is a widely utilized method for assessing the mechanical properties of thin films,including metals,polymers,and semiconductors.However,as film thickness diminishes to nanometer scales,boundary condition...The bulge test is a widely utilized method for assessing the mechanical properties of thin films,including metals,polymers,and semiconductors.However,as film thickness diminishes to nanometer scales,boundary conditions dominated by weak van der Waals forces significantly impact mechanical responses.Instead of sample fracture,interfacial shear deformation and delamination become the primary deformation modes,thereby challenging the applicability of conventional bulge models.To accommodate the interfacial effect,a modified mechanical model based on the bulge test has been proposed.This review summarizes recent advancements in the bulge test to highlight the potential challenges and opportunities for future research.展开更多
Because of complexity and non-predictability of the tunnel surrounding rock,the problem with the determination of the physical and mechanical parameters of the surrounding rock has become a main obstacle to theoretica...Because of complexity and non-predictability of the tunnel surrounding rock,the problem with the determination of the physical and mechanical parameters of the surrounding rock has become a main obstacle to theoretical research and numerical analysis in tunnel engineering.During design,it is a frequent practice,therefore,to give recommended values by analog based on experience.It is a key point in current research to make use of the displacement back analytic method to comparatively accurately determine the parameters of the surrounding rock whereas artificial intelligence possesses an exceptionally strong capability of identifying,expressing and coping with such complex non-linear relationships.The parameters can be verified by searching the optimal network structure,using back analysis on measured data to search optimal parameters and performing direct computation of the obtained results.In the current paper,the direct analysis is performed with the biological emulation system and the software of Fast Lagrangian Analysis of Continua(FLAC3D.The high non-linearity,network reasoning and coupling ability of the neural network are employed.The output vector required of the training of the neural network is obtained with the numerical analysis software.And the overall space search is conducted by employing the Adaptive Immunity Algorithm.As a result,we are able to avoid the shortcoming that multiple parameters and optimized parameters are easy to fall into a local extremum.At the same time,the computing speed and efficiency are increased as well.Further,in the paper satisfactory conclusions are arrived at through the intelligent direct-back analysis on the monitored and measured data at the Erdaoya tunneling project.The results show that the physical and mechanical parameters obtained by the intelligent direct-back analysis proposed in the current paper have effectively improved the recommended values in the original prospecting data.This is of practical significance to the appraisal of stability and informationization design of the surrounding rock.展开更多
The failure of cement sheath integrity can be easily caused by alternating pressure during large-scale multistage hydraulic fracturing in shale-gas well.An elastic-plastic mechanical model of casing-cement sheath-form...The failure of cement sheath integrity can be easily caused by alternating pressure during large-scale multistage hydraulic fracturing in shale-gas well.An elastic-plastic mechanical model of casing-cement sheath-formation(CSF)system under alternating pressure is established based on the Mohr-Coulomb criterion and thick-walled cylinder theory,and it has been solved by MATLAB programming combining global optimization algorithm with Global Search.The failure mechanism of cement sheath integrity is investigated,by which it can be seen that the formation of interface debonding is mainly related to the plastic strain accumulation,and there is a risk of interface debonding under alternating pressure,once the cement sheath enters plasticity whether in shallow or deep well sections.The matching relationship between the mechanical parameters(elastic modulus and Poisson's ratio)of cement sheath and its integrity failure under alternating pressure in whole well sections is studied,by which it has been found there is a“critical range”in the Poisson's ratio of cement sheath.When the Poisson's ratio is below the“critical range”,there is a positive correlation between the yield internal pressure of cement sheath(SYP)and its elastic modulus.However,when the Poisson's ratio is above the“critical range”,there is a negative correlation.The elastic modulus of cement sheath is closely related to its Poisson's ratio,and restricts each other.Scientific and reasonable matching between mechanical parameters of cement sheath and CSF system under different working conditions can not only reduce the cost,but also protect the cement sheath integrity.展开更多
To study the influence of temperature and water content on ultrasonic wave velocity and to establish the relationship between ultrasonic wave velocity and frozen silty clay strength, ultrasonic tests were conducted to...To study the influence of temperature and water content on ultrasonic wave velocity and to establish the relationship between ultrasonic wave velocity and frozen silty clay strength, ultrasonic tests were conducted to frozen silty clay by using RSM-SY5（T） nonmetal supersonic test meter, and the tensile strength and compressive strength of silty clay were measured under various negative temperatures. Test and analysis results indicate that, ultrasonic wave velocity rapidly changes in the temperature range of-1 ℃ to -5 ℃. Ultrasonic wave velocity increased with an increase of water content until the water content reached the critical water content, while decreased with an increase of water content after the water content exceeded the critical water content. This study showed that there was strong positive correlation between the ul- trasonic wave velocity and the frozen soil strength. As ultrasonic wave velocity increased, either tensile strength or com- pressive strength increased. Based on the experimental data, the relationship between ultrasonic wave velocity and frozen silty clay strength was obtained through regression analysis. It was found that the ultrasonic test technique can be used to test frozen soils and lay the foundation for the determination of frozen soil strength.展开更多
The artificial neutral network(ANN) has the ability that self-study and self-remember, its 3 layers BP network has been applied extensively, but sometimes because of serious multi-correlation between the variables, an...The artificial neutral network(ANN) has the ability that self-study and self-remember, its 3 layers BP network has been applied extensively, but sometimes because of serious multi-correlation between the variables, and a few observations while many variables, there usually will result into paralyzing in study, and the neutral network further development is restricted in the system to some extent. The partial least square regression(PLS) has its advantage of building the calculation model between the variables with strong multi-correlation, especially much effective on a few data and many variables. So a new and effective method-improved neutral network has been introduced-the neutral network based on the PLS. The results of example show the improved method has a few calculations and high accuracy, and provide a new way for valuing the rock mass mechanical parameters.展开更多
To solve the problems of blindness and inefficiency existing in the determination of meso-level mechanical parameters of particle flow code (PFC) models, we firstly designed and numerically carried out orthogonal test...To solve the problems of blindness and inefficiency existing in the determination of meso-level mechanical parameters of particle flow code (PFC) models, we firstly designed and numerically carried out orthogonal tests on rock samples to investigate the correlations between macro-and meso-level mechanical parameters of rock-like bonded granular materials. Then based on the artificial intelligent technology, the intelligent prediction systems for nine meso-level mechanical parameters of PFC models were obtained by creating, training and testing the prediction models with the set of data got from the orthogonal tests. Lastly the prediction systems were used to predict the meso-level mechanical parameters of one kind of sandy mudstone, and according to the predicted results the macroscopic properties of the rock were obtained by numerical tests. The maximum relative error between the numerical test results and real rock properties is 3.28% which satisfies the precision requirement in engineering. It shows that this paper provides a fast and accurate method for the determination of meso-level mechanical parameters of PFC models.展开更多
In this work, a systematic approach is presented to obtain the input-output equations of a single loop 4-bar spatial mechanisms. The dialytic method along with Denavit-Hartenberg parameters can be used to obtain these...In this work, a systematic approach is presented to obtain the input-output equations of a single loop 4-bar spatial mechanisms. The dialytic method along with Denavit-Hartenberg parameters can be used to obtain these equations efficiently. A genetic algorithm （GA） has been used to solve the problem of spatial mechanisms synthesis. Two types of mechanisms, e.g., RSCR and RSPC （R： revolute; S： spherical; C： cylindrical; P： prismatic）, have illustrated the application of the GA to solve the problem of function generation and path generation. In some cases, the GA method becomes trapped in a local minimum. A combined GA-fuzzy logic （GA-FL） method is then used to improve the final result. The results show that GAs, combined with an adequate description of the mechanism, are well suited for spatial mechanism synthesis problems and have neither difficulties inherent to the choice of the initial feasible guess, nor a problem of convergence, as it is the case for deterministic methods.展开更多
In order to comprehend the dynamic disaster mechanism induced by overburden rock caving during the advancement of a coal mining face, a physical simulation model is constructed basing on the geological condition of th...In order to comprehend the dynamic disaster mechanism induced by overburden rock caving during the advancement of a coal mining face, a physical simulation model is constructed basing on the geological condition of the 21221 mining face at Qianqiu coal mine in Henan Province, China. This study established, a comprehensive monitoring system to investigate the interrelations and evolutionary characteristics among multiple mechanical parameters, including mining-induced stress, displacement, temperature, and acoustic emission events during overburden rock caving. It is suggested that, despite the uniformity of the overburden rock caving interval, the main characteristic of overburden rock lies in its uneven caving strength. The mining-induced stress exhibits a reasonable interrelation with the displacement, temperature, and acoustic emission events of the rock strata. With the advancement of the coal seam, the mining-induced stress undergoes four successive stages: gentle stability, gradual accumulation, high-level mutation, and a return to stability. The variations in other mechanical parameters does not synchronize with the signifcant changes in mining-induced stress. Before the collapse of overburden rock occurs, rock strata temperature increment decreases and the acoustic emission ringing counts surges with the increase of rock strata displacement and mining-induced stress. Therefore, the collaborative characteristics of mining-induced stress, displacement, temperature, and acoustic emission ringing counts can be identifed as the precursor information or overburden rock caving. These results are in good consistent with on-site situation in the coal mine.展开更多
This paper proposes a new continuity model for engineering in rock masses and a new schematic method for reporting the engineering of rock continuity. This method can be used to evaluate the mechanics of every kind of...This paper proposes a new continuity model for engineering in rock masses and a new schematic method for reporting the engineering of rock continuity. This method can be used to evaluate the mechanics of every kind of medium;and is a new way to determine the mechanical parameters used in engineering design in rock masses. In the numerical simulation, the experimental parameters of intact rock were combined with the structural properties of field rock. Theexperimental results for orthogonally-jointed rock are given. The results included the curves of the stress-strain relationship of some rock masses, the curve of the relationship between the dimension Δ and the uniaxial pressure-resistant strength σc of these rock masses, and pictures of the destructive procedure of some rock masses in uniaxial or triaxial tests, etc. Application of the method to engineering design in rock masses showed the potential of its application to engineering practice.展开更多
Gas hydrate(hereinafter,"hydrate"for short)in the marine environment mostly lies in weakly consolidated sediments,so its undisturbed coring is difficult and costly.In view of this,it is necessary to understa...Gas hydrate(hereinafter,"hydrate"for short)in the marine environment mostly lies in weakly consolidated sediments,so its undisturbed coring is difficult and costly.In view of this,it is necessary to understand the relationship between acoustic properties and elastic mechanical properties of hydrates through laboratory experiments.In this paper,samples of hydrate sediments were prepared indoors.Then,petrophysical experiments were carried out on these samples to measure the electric parameters and acoustic parameters of hydrate sediments.Finally,according to the theory of elasticity,the dynamic elastic mechanical parameters under three axial compressions,three particle sizes and three shale contents were calculated to analyze their effects on the dynamic elastic mechanical parameters of hydrate sediments under different conditions.And the following research results were obtained.First,when the hydrate saturation is in a certain range,it is in a proportional relationship with the elastic parameters of sediments.Second,when the hydrate saturation is constant,the dynamic Young's modulus of hydrate sediments increases,but the Poisson's ratio has little to do with the axial compression as particle sizes(0.125-1.180 mm)and axial compression increase and shale content decreases.Third,a model of the relationship between the elastic parameters and the shale content and axial compression is established.In conclusion,the dynamic elastic mechanical indexes of gas hydrate obtained from the acoustic logging methodology will solve the above difficulties and the research results provide a reference for calculating the mechanical properties of hydrate sediments by use of logging data.展开更多
The strength parameters of hydrate-bearing sediments(HBS)are vital to geological risk assessment and control during drilling and production operations.However,current publications mainly focus on the laboratory evalua...The strength parameters of hydrate-bearing sediments(HBS)are vital to geological risk assessment and control during drilling and production operations.However,current publications mainly focus on the laboratory evaluation of strength parameters through triaxial compression,generating results intrinsically deviating from those obtained through petrophysical modeling.In this study,we developed an integrated apparatus that can simultaneously measure wave velocity and the mechanical behaviors of HBS under triaxial compression conditions.A series of experiments were conducted to analyze correlations between wave velocities and strength parameters.Results reveal that the P-and S-wave velocities considerably increase with hydrate saturation and are affected by effective confining pressure.Failure strength and elastic modulus are correlated with P-wave velocity.Finally,semi-empirical models are developed to predict strength parameters based on P-wave velocity and extended to establish longitudinal profiles for strength parameters of hydrate reservoirs in the Nankai Trough.This study offers insights into the acoustic properties of HBS under stress states for the prediction of mechanical parameters during natural gas hydrate development.展开更多
The non-linear inversion of rock mechanics parameters based on genetic algorithm is presented. The principIe and step of genetic algorithm is also given. A brief discussion of this method and an application example is...The non-linear inversion of rock mechanics parameters based on genetic algorithm is presented. The principIe and step of genetic algorithm is also given. A brief discussion of this method and an application example is presented at the end of this paper. From the satisfied result, quick, convenient and practical new approach is developed to solve this kind of problems.展开更多
The seepage characteristics of shale reservoirs are influenced not only by multi-field coupling effects such as stress field,temperature field,and seepage field but also exhibit evident creep characteristics during oi...The seepage characteristics of shale reservoirs are influenced not only by multi-field coupling effects such as stress field,temperature field,and seepage field but also exhibit evident creep characteristics during oil and gas exploitation.The complex fluid flow in such reservoirs is analyzed using a combination of theoretical modeling and numerical simulation.This study develops a comprehensive mathematical model that integrates the impact of creep on the seepage process,with consideration of factors including stress,strain,and time-dependent deformation.The model is validated through a series of numerical experiments,which demonstrate the significant influence of creep on the seepage behavior.The results indicate that the rock mechanical parameters and creep constitutive model were determined through triaxial compression tests and uniaxial creep tests.A creep-seepage coupling control equation for shale was established based on the Burgers creep model.The absolute value of the volumetric strain of shale increases rapidly in the initial creep stage,and the increase in vertical stress accelerates the rock’s creep deformation.During the deceleration creep stage,the volumetric strain of the reservoir increases rapidly,leading to a significant decrease in permeability.In the stable creep stage,the pores and fractures in the rock are further compressed,causing a gradual reduction in permeability,which eventually stabilizes.展开更多
With the advancement of unconventional oil and gas exploration and development,tight gravelly sandstone reservoirs have garnered increasing attention.In this study,triaxial compression experiments are conducted on gra...With the advancement of unconventional oil and gas exploration and development,tight gravelly sandstone reservoirs have garnered increasing attention.In this study,triaxial compression experiments are conducted on gravelly sandstone cores,and correlation analysis is employed to establish the relationships between fractal dimensions of the fractures and rock mechanics parameters.For cores of gravelly sandstone,a positive correlation exists between the fractal dimension and the brittleness index.The prediction model reveals that the error between the predicted and actual values for well 3 is relatively large,which can be attributed to the presence of pure sandstone cores in well 3.Under high confining pressure in the deep strata,rocks exhibit a decreasing trend in fractal dimensions,a phenomenon due to the stress-memory effect.In addition,numerical simulation is further employed to study the effect of the factors that could affect the complexity of the fractures,and the results show that the fractal dimension of gravelly sandstone declines with increasing confining pressure,peak compressive strength,and rock elastic modulus as the loading process intensifies.展开更多
Focused ultrasound(FUS)therapy generates sufficient heat for medical interventions like tumor ablation by concentrating energy at the focal point.The complex viscoelastic properties of biological tissues pose challeng...Focused ultrasound(FUS)therapy generates sufficient heat for medical interventions like tumor ablation by concentrating energy at the focal point.The complex viscoelastic properties of biological tissues pose challenges in balancing focusing precision and penetration depth,impacting the safety of surrounding tissues and treatment efficacy.This study develops an acoustic-solid-thermal coupling computational model to elucidate the dynamic mechanical response and energy dissipation mechanisms of soft tissue during FUS thermal therapy using a hyper-viscoelastic constitutive model.Results indicate that the high compressibility and low shear resistance of biological tissues result in a unique shear dissipation mechanism.Energy dissipation efficiency per area is indirectly influenced by load frequency via its effect on the dynamic shear modulus and is directly proportional to load amplitude.Focusing precision,represented by the focal zone width,is inversely controlled by frequency via wavelength.A mathematical model for evaluating temperature rise efficiency is proposed,and an optimal frequency for efficient FUS thermal therapy in brain-like soft materials is identified.This research elucidates the link between viscoelastic tissue behavior and FUS treatment outcomes,offering insights for optimizing FUS applications in various medical fields.展开更多
A series of acoustic emission(AE)-integrated conventional triaxial compression tests(CTTs)were conducted to evaluate the mechanical properties of hard red sandstone.Under conventional triaxial stress states,the crack ...A series of acoustic emission(AE)-integrated conventional triaxial compression tests(CTTs)were conducted to evaluate the mechanical properties of hard red sandstone.Under conventional triaxial stress states,the crack closure stress,crack initiation stress,and damage stress ranged in 13.75%-22.34%,31.84%-42.19%,and 63.85%-75.93%of the peak strength of sandstone,respectively.The AE parameters reflected the confining pressure(σ3)effect on microcrack propagation,withσ3=5 MPa identified as the threshold affecting both the timing of numerous AE hits and the distribution range of peak frequencies of AE signals before the final failure of each specimen.The AE property analysis showed that shear cracks played a dominant role in rock failure in CCTs,which ranged in 60%-85%of the total number of cracks.A smallerσ3 value promoted shear failure,whereas a largerσ3 value inhibited it.Furthermore,the appropriate dataset selection range to accurately calculate the cohesion force and internal friction angle in CTTs and variable-angle shear tests was determined.展开更多
Taking the test stopes during continuous mining induced roof caving of Tongkeng ore-body No.92 as example, the calculation flow of unloading analysis was established. According to the unloading region division method ...Taking the test stopes during continuous mining induced roof caving of Tongkeng ore-body No.92 as example, the calculation flow of unloading analysis was established. According to the unloading region division method of the affected zone theory, and the deterioration laws of mechanics parameters of unloading rock mass, the continuous mining process in underground mine was analyzed by the software MIDAS/GTS, the mechanical response of roof rock mass unloading was studied, and the differences were analyzed with the conventional simulation. The result shows that the maximum tensile stress, subsidence displacement and equivalent plastic strain of roof rock mass are 1.5 MPa, 20 cm and 1.5% in the unloading analysis, while 1.0 MPa, 13 cm and 0.9% in the conventional analysis. The values of unloading analysis, which are also closer to the actual situation, are greater than those of conventional analysis; the maximum step in continuous mining is 48 m, which shows that the induced treatment of the roof should be carried out after 2 mining steps展开更多
To enable real-time prediction of rock mechanical parameters during drilling,this study proposes a method based on vibration-while-drilling(VWD)spectral features.Three-component vibration signals were collected experi...To enable real-time prediction of rock mechanical parameters during drilling,this study proposes a method based on vibration-while-drilling(VWD)spectral features.Three-component vibration signals were collected experimentally,and their dominant frequency,low-frequency energy,and spectral centroid were extracted as predictors.A ridge regression model was developed to map these spectral features to rock mechanical parameters.Compared with conventional drilling parameters,the spectral descriptors capture lithology-dependent stiffness more effectively,with the low-frequency(0-20 Hz)energy showing a strong correlation with rock strength.Validation on tuspecimens achieved high accuracy(mean R^(2)>0.80)and stable calibration between predicted and measured values.Bootstrap and permutation analyses conrmed the consistency and interpretability of feature contributions,while ridge-penalty scanning demonstrated strong resistance to overtting.The proposed approach provides an efcient and interpretable framework for realtime eld prediction of rock mechanical parameters and oers a foundation for multi-lithology and physicsinformed model extensions.展开更多
Based on the classical static theory and static numerical simulation,the static method could not accurately reflect the stability of goaf where the rocks on the pillar and roof are influenced by Theological and blasti...Based on the classical static theory and static numerical simulation,the static method could not accurately reflect the stability of goaf where the rocks on the pillar and roof are influenced by Theological and blasting disturbance for a long time.According to the test from the site,an experimental study was made in Theological and dynamic disturbance.After that,on the basis of variable rock mechanics parameters from the experimental data,numerical simulation was used to analyze the vertical stress distribution of goaf,vertical displacement and plastic area of roof in the "deterioration" caused by Theological and blasting,which shows that the mechanics properties of the rock were greatly influenced by Theological,and dynamic disturbance.The results of the experimental study and numerical simulation show that the mechanics properties of rock are greatly influenced by Theological and dynamic disturbance.As a result,the stability of goaf is greatly reduced.Finally,by comparing golf monitoring results with the analysis of theoretical calculation,it was found that the results were approximately the same,which testifies the reliability of the method.This method provides a new way of studying the stability of goaf as well as laying a basic foundation for future safety management.展开更多
基金the National Key Research and Development Project of China(No.2019YFC1509704)the National Natural Science Foundation of China(Nos.U1704243,41741019,41977249 and 42090052)+2 种基金the Henan Province Science and Technology Research Project(Nos.192102310006,232102320035)the Innovation Fund for Doctoral Students of North China University of Water Resources and Electric Power(No.NCWUBC202313)the Key Research Project Plan for Higher Education Institutions in Henan Province(No.24A410003).
文摘Altered rock,often encountered in major engineering projects,can seriously affect the stability of rocks and slopes surrounding deeply buried tunnels.This study addressed the alteration mechanism,alteration degree classification,and mechanical parameters of altered rock in engineering project areas using field testing,thin slice identification,X-ray diffraction,and major element testing.Results showed that the altered rock types in the areas of the Pingjiang Pumped Storage Power Station,Hunan Province,and a diversion tunnel in northern Xinjiang Uygur Autonomous Region include biotite granodiorite,biotite monzogranite,and cataclastic granite,and that the main alteration mechanisms are chloritization of biotite and clayization of feldspar minerals.The altered rocks were classified as slightly,moderately,or strongly altered according to their apparent characteristics,rebound value,longitudinal wave velocity,metamorphic mineral content,and porosity.The bulk density,elastic modulus,cohesion,and internal friction angle(Poisson’s ratio)of the altered rocks decreased(increased)with increase in the degree of alteration.Numerical simulations showed that in altered rock slope areas,the zone of strong rock alteration and the moderate-strong alteration contact zone exhibit locally large deformations that represent a certain hazard to engineering projects.These results provide valuable guidance and support for major projects in altered rock areas.
基金supported by the National Natural Science Foundation of China(Grant Nos.22072031,12372107,11832010,and 11890682)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB36000000).
文摘The bulge test is a widely utilized method for assessing the mechanical properties of thin films,including metals,polymers,and semiconductors.However,as film thickness diminishes to nanometer scales,boundary conditions dominated by weak van der Waals forces significantly impact mechanical responses.Instead of sample fracture,interfacial shear deformation and delamination become the primary deformation modes,thereby challenging the applicability of conventional bulge models.To accommodate the interfacial effect,a modified mechanical model based on the bulge test has been proposed.This review summarizes recent advancements in the bulge test to highlight the potential challenges and opportunities for future research.
基金supported by the National Natural Science Foundation of China(No.50609028)
文摘Because of complexity and non-predictability of the tunnel surrounding rock,the problem with the determination of the physical and mechanical parameters of the surrounding rock has become a main obstacle to theoretical research and numerical analysis in tunnel engineering.During design,it is a frequent practice,therefore,to give recommended values by analog based on experience.It is a key point in current research to make use of the displacement back analytic method to comparatively accurately determine the parameters of the surrounding rock whereas artificial intelligence possesses an exceptionally strong capability of identifying,expressing and coping with such complex non-linear relationships.The parameters can be verified by searching the optimal network structure,using back analysis on measured data to search optimal parameters and performing direct computation of the obtained results.In the current paper,the direct analysis is performed with the biological emulation system and the software of Fast Lagrangian Analysis of Continua(FLAC3D.The high non-linearity,network reasoning and coupling ability of the neural network are employed.The output vector required of the training of the neural network is obtained with the numerical analysis software.And the overall space search is conducted by employing the Adaptive Immunity Algorithm.As a result,we are able to avoid the shortcoming that multiple parameters and optimized parameters are easy to fall into a local extremum.At the same time,the computing speed and efficiency are increased as well.Further,in the paper satisfactory conclusions are arrived at through the intelligent direct-back analysis on the monitored and measured data at the Erdaoya tunneling project.The results show that the physical and mechanical parameters obtained by the intelligent direct-back analysis proposed in the current paper have effectively improved the recommended values in the original prospecting data.This is of practical significance to the appraisal of stability and informationization design of the surrounding rock.
基金Research work was financed by the National Natural Science Foundation of China(No.52074232)Sichuan Science and Technology Program(No.2022NSFSC0028,No.2022NSFSC0994).Without their support,this work would not have been possible.
文摘The failure of cement sheath integrity can be easily caused by alternating pressure during large-scale multistage hydraulic fracturing in shale-gas well.An elastic-plastic mechanical model of casing-cement sheath-formation(CSF)system under alternating pressure is established based on the Mohr-Coulomb criterion and thick-walled cylinder theory,and it has been solved by MATLAB programming combining global optimization algorithm with Global Search.The failure mechanism of cement sheath integrity is investigated,by which it can be seen that the formation of interface debonding is mainly related to the plastic strain accumulation,and there is a risk of interface debonding under alternating pressure,once the cement sheath enters plasticity whether in shallow or deep well sections.The matching relationship between the mechanical parameters(elastic modulus and Poisson's ratio)of cement sheath and its integrity failure under alternating pressure in whole well sections is studied,by which it has been found there is a“critical range”in the Poisson's ratio of cement sheath.When the Poisson's ratio is below the“critical range”,there is a positive correlation between the yield internal pressure of cement sheath(SYP)and its elastic modulus.However,when the Poisson's ratio is above the“critical range”,there is a negative correlation.The elastic modulus of cement sheath is closely related to its Poisson's ratio,and restricts each other.Scientific and reasonable matching between mechanical parameters of cement sheath and CSF system under different working conditions can not only reduce the cost,but also protect the cement sheath integrity.
基金supported by the National Natural Science Foundation of China (No.41271080 and No.41230630)the Western Project Program of the Chinese Academy of Sciences(KZCX2-XB3-19)the open fund of Qinghai Research and Observation Base, Key Laboratory of Highway Construction and Maintenance Technology in Permafrost Region Ministry of Transport, PRC (2012-12-4)
文摘To study the influence of temperature and water content on ultrasonic wave velocity and to establish the relationship between ultrasonic wave velocity and frozen silty clay strength, ultrasonic tests were conducted to frozen silty clay by using RSM-SY5（T） nonmetal supersonic test meter, and the tensile strength and compressive strength of silty clay were measured under various negative temperatures. Test and analysis results indicate that, ultrasonic wave velocity rapidly changes in the temperature range of-1 ℃ to -5 ℃. Ultrasonic wave velocity increased with an increase of water content until the water content reached the critical water content, while decreased with an increase of water content after the water content exceeded the critical water content. This study showed that there was strong positive correlation between the ul- trasonic wave velocity and the frozen soil strength. As ultrasonic wave velocity increased, either tensile strength or com- pressive strength increased. Based on the experimental data, the relationship between ultrasonic wave velocity and frozen silty clay strength was obtained through regression analysis. It was found that the ultrasonic test technique can be used to test frozen soils and lay the foundation for the determination of frozen soil strength.
基金Supported by Henan Innovation Project for University Prominent Research Talents(2005KYCX015) Henan Innovation Talents Project for University
文摘The artificial neutral network(ANN) has the ability that self-study and self-remember, its 3 layers BP network has been applied extensively, but sometimes because of serious multi-correlation between the variables, and a few observations while many variables, there usually will result into paralyzing in study, and the neutral network further development is restricted in the system to some extent. The partial least square regression(PLS) has its advantage of building the calculation model between the variables with strong multi-correlation, especially much effective on a few data and many variables. So a new and effective method-improved neutral network has been introduced-the neutral network based on the PLS. The results of example show the improved method has a few calculations and high accuracy, and provide a new way for valuing the rock mass mechanical parameters.
基金the National Natural Science Foundation of China (Nos. 50674083 and 51074162) for its financial support
文摘To solve the problems of blindness and inefficiency existing in the determination of meso-level mechanical parameters of particle flow code (PFC) models, we firstly designed and numerically carried out orthogonal tests on rock samples to investigate the correlations between macro-and meso-level mechanical parameters of rock-like bonded granular materials. Then based on the artificial intelligent technology, the intelligent prediction systems for nine meso-level mechanical parameters of PFC models were obtained by creating, training and testing the prediction models with the set of data got from the orthogonal tests. Lastly the prediction systems were used to predict the meso-level mechanical parameters of one kind of sandy mudstone, and according to the predicted results the macroscopic properties of the rock were obtained by numerical tests. The maximum relative error between the numerical test results and real rock properties is 3.28% which satisfies the precision requirement in engineering. It shows that this paper provides a fast and accurate method for the determination of meso-level mechanical parameters of PFC models.
基金Project supported by the CPER (Contrats de Projets Etat Région) Poitou-Charentes 2007-2013 (Program Project 10 "Imageset interactivités")the Tunisian Secretary of State of Scientific Research and Technology (SERST) through the contract LAB-MA 05
文摘In this work, a systematic approach is presented to obtain the input-output equations of a single loop 4-bar spatial mechanisms. The dialytic method along with Denavit-Hartenberg parameters can be used to obtain these equations efficiently. A genetic algorithm （GA） has been used to solve the problem of spatial mechanisms synthesis. Two types of mechanisms, e.g., RSCR and RSPC （R： revolute; S： spherical; C： cylindrical; P： prismatic）, have illustrated the application of the GA to solve the problem of function generation and path generation. In some cases, the GA method becomes trapped in a local minimum. A combined GA-fuzzy logic （GA-FL） method is then used to improve the final result. The results show that GAs, combined with an adequate description of the mechanism, are well suited for spatial mechanism synthesis problems and have neither difficulties inherent to the choice of the initial feasible guess, nor a problem of convergence, as it is the case for deterministic methods.
基金supported by the State Key Research Development Program of China(2022YFC3004602)Independent Research fund of Joint NationalLocal Engineering Research Centre for Safe and Precise Coal Mining(Anhui University of Science and Technology)(EC2022001)+2 种基金the National Natural Science Foundation of China(41872205)Beijing Natural Science Foundation(8202041)the Fundamental Research Funds for the Central Universities(2022YJSLJ08,2022JCCXNY03).
文摘In order to comprehend the dynamic disaster mechanism induced by overburden rock caving during the advancement of a coal mining face, a physical simulation model is constructed basing on the geological condition of the 21221 mining face at Qianqiu coal mine in Henan Province, China. This study established, a comprehensive monitoring system to investigate the interrelations and evolutionary characteristics among multiple mechanical parameters, including mining-induced stress, displacement, temperature, and acoustic emission events during overburden rock caving. It is suggested that, despite the uniformity of the overburden rock caving interval, the main characteristic of overburden rock lies in its uneven caving strength. The mining-induced stress exhibits a reasonable interrelation with the displacement, temperature, and acoustic emission events of the rock strata. With the advancement of the coal seam, the mining-induced stress undergoes four successive stages: gentle stability, gradual accumulation, high-level mutation, and a return to stability. The variations in other mechanical parameters does not synchronize with the signifcant changes in mining-induced stress. Before the collapse of overburden rock occurs, rock strata temperature increment decreases and the acoustic emission ringing counts surges with the increase of rock strata displacement and mining-induced stress. Therefore, the collaborative characteristics of mining-induced stress, displacement, temperature, and acoustic emission ringing counts can be identifed as the precursor information or overburden rock caving. These results are in good consistent with on-site situation in the coal mine.
文摘This paper proposes a new continuity model for engineering in rock masses and a new schematic method for reporting the engineering of rock continuity. This method can be used to evaluate the mechanics of every kind of medium;and is a new way to determine the mechanical parameters used in engineering design in rock masses. In the numerical simulation, the experimental parameters of intact rock were combined with the structural properties of field rock. Theexperimental results for orthogonally-jointed rock are given. The results included the curves of the stress-strain relationship of some rock masses, the curve of the relationship between the dimension Δ and the uniaxial pressure-resistant strength σc of these rock masses, and pictures of the destructive procedure of some rock masses in uniaxial or triaxial tests, etc. Application of the method to engineering design in rock masses showed the potential of its application to engineering practice.
基金supported by the National Key R&D Program of China“New technology for solid fluidization testing of marine gas hydrate”(No.:2016YFC0304008).
文摘Gas hydrate(hereinafter,"hydrate"for short)in the marine environment mostly lies in weakly consolidated sediments,so its undisturbed coring is difficult and costly.In view of this,it is necessary to understand the relationship between acoustic properties and elastic mechanical properties of hydrates through laboratory experiments.In this paper,samples of hydrate sediments were prepared indoors.Then,petrophysical experiments were carried out on these samples to measure the electric parameters and acoustic parameters of hydrate sediments.Finally,according to the theory of elasticity,the dynamic elastic mechanical parameters under three axial compressions,three particle sizes and three shale contents were calculated to analyze their effects on the dynamic elastic mechanical parameters of hydrate sediments under different conditions.And the following research results were obtained.First,when the hydrate saturation is in a certain range,it is in a proportional relationship with the elastic parameters of sediments.Second,when the hydrate saturation is constant,the dynamic Young's modulus of hydrate sediments increases,but the Poisson's ratio has little to do with the axial compression as particle sizes(0.125-1.180 mm)and axial compression increase and shale content decreases.Third,a model of the relationship between the elastic parameters and the shale content and axial compression is established.In conclusion,the dynamic elastic mechanical indexes of gas hydrate obtained from the acoustic logging methodology will solve the above difficulties and the research results provide a reference for calculating the mechanical properties of hydrate sediments by use of logging data.
基金supported by the Qingdao Natural Science Foundation(No.23-2-1-54-zyyd-jch)the National Natural Science Foundation of China(Nos.42206233 and 42206231)+2 种基金the National Key Research and Development Pro-gram of China(No.2022YFC2806405)the Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education,Tongji University(No.KLE-TJGE-G2202)the Laoshan Laboratory(No.LSKJ202203506)。
文摘The strength parameters of hydrate-bearing sediments(HBS)are vital to geological risk assessment and control during drilling and production operations.However,current publications mainly focus on the laboratory evaluation of strength parameters through triaxial compression,generating results intrinsically deviating from those obtained through petrophysical modeling.In this study,we developed an integrated apparatus that can simultaneously measure wave velocity and the mechanical behaviors of HBS under triaxial compression conditions.A series of experiments were conducted to analyze correlations between wave velocities and strength parameters.Results reveal that the P-and S-wave velocities considerably increase with hydrate saturation and are affected by effective confining pressure.Failure strength and elastic modulus are correlated with P-wave velocity.Finally,semi-empirical models are developed to predict strength parameters based on P-wave velocity and extended to establish longitudinal profiles for strength parameters of hydrate reservoirs in the Nankai Trough.This study offers insights into the acoustic properties of HBS under stress states for the prediction of mechanical parameters during natural gas hydrate development.
文摘The non-linear inversion of rock mechanics parameters based on genetic algorithm is presented. The principIe and step of genetic algorithm is also given. A brief discussion of this method and an application example is presented at the end of this paper. From the satisfied result, quick, convenient and practical new approach is developed to solve this kind of problems.
基金supported by the National Natural Science Foundation of China(Grant Nos.42472195 and 42272153)the Research Fund of PetroChina Tarim Oilfield Company(Grant No.671023060003)Technology Projects of China National Petroleum Corporation(Grant No.2023ZZ16YJ02).
文摘The seepage characteristics of shale reservoirs are influenced not only by multi-field coupling effects such as stress field,temperature field,and seepage field but also exhibit evident creep characteristics during oil and gas exploitation.The complex fluid flow in such reservoirs is analyzed using a combination of theoretical modeling and numerical simulation.This study develops a comprehensive mathematical model that integrates the impact of creep on the seepage process,with consideration of factors including stress,strain,and time-dependent deformation.The model is validated through a series of numerical experiments,which demonstrate the significant influence of creep on the seepage behavior.The results indicate that the rock mechanical parameters and creep constitutive model were determined through triaxial compression tests and uniaxial creep tests.A creep-seepage coupling control equation for shale was established based on the Burgers creep model.The absolute value of the volumetric strain of shale increases rapidly in the initial creep stage,and the increase in vertical stress accelerates the rock’s creep deformation.During the deceleration creep stage,the volumetric strain of the reservoir increases rapidly,leading to a significant decrease in permeability.In the stable creep stage,the pores and fractures in the rock are further compressed,causing a gradual reduction in permeability,which eventually stabilizes.
基金funded by National Natural Science Foundation of China(42272150,42090025)the State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Efficient Development。
文摘With the advancement of unconventional oil and gas exploration and development,tight gravelly sandstone reservoirs have garnered increasing attention.In this study,triaxial compression experiments are conducted on gravelly sandstone cores,and correlation analysis is employed to establish the relationships between fractal dimensions of the fractures and rock mechanics parameters.For cores of gravelly sandstone,a positive correlation exists between the fractal dimension and the brittleness index.The prediction model reveals that the error between the predicted and actual values for well 3 is relatively large,which can be attributed to the presence of pure sandstone cores in well 3.Under high confining pressure in the deep strata,rocks exhibit a decreasing trend in fractal dimensions,a phenomenon due to the stress-memory effect.In addition,numerical simulation is further employed to study the effect of the factors that could affect the complexity of the fractures,and the results show that the fractal dimension of gravelly sandstone declines with increasing confining pressure,peak compressive strength,and rock elastic modulus as the loading process intensifies.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.11972205,11921002,11972210,and 12302096)the National Key Research Development Program of China(Grant No.2020-JCJQ-ZD-254).
文摘Focused ultrasound(FUS)therapy generates sufficient heat for medical interventions like tumor ablation by concentrating energy at the focal point.The complex viscoelastic properties of biological tissues pose challenges in balancing focusing precision and penetration depth,impacting the safety of surrounding tissues and treatment efficacy.This study develops an acoustic-solid-thermal coupling computational model to elucidate the dynamic mechanical response and energy dissipation mechanisms of soft tissue during FUS thermal therapy using a hyper-viscoelastic constitutive model.Results indicate that the high compressibility and low shear resistance of biological tissues result in a unique shear dissipation mechanism.Energy dissipation efficiency per area is indirectly influenced by load frequency via its effect on the dynamic shear modulus and is directly proportional to load amplitude.Focusing precision,represented by the focal zone width,is inversely controlled by frequency via wavelength.A mathematical model for evaluating temperature rise efficiency is proposed,and an optimal frequency for efficient FUS thermal therapy in brain-like soft materials is identified.This research elucidates the link between viscoelastic tissue behavior and FUS treatment outcomes,offering insights for optimizing FUS applications in various medical fields.
基金partially supported by the National Natural Science Foundation of China(No.52104112)the Science and Technology Innovation Program of Hunan Province,China(Nos.2021RC3007,2020RC3090)by the Fundamental Research Funds for the Central Universities of Central South University,China(No.2024ZZTS0060)。
文摘A series of acoustic emission(AE)-integrated conventional triaxial compression tests(CTTs)were conducted to evaluate the mechanical properties of hard red sandstone.Under conventional triaxial stress states,the crack closure stress,crack initiation stress,and damage stress ranged in 13.75%-22.34%,31.84%-42.19%,and 63.85%-75.93%of the peak strength of sandstone,respectively.The AE parameters reflected the confining pressure(σ3)effect on microcrack propagation,withσ3=5 MPa identified as the threshold affecting both the timing of numerous AE hits and the distribution range of peak frequencies of AE signals before the final failure of each specimen.The AE property analysis showed that shear cracks played a dominant role in rock failure in CCTs,which ranged in 60%-85%of the total number of cracks.A smallerσ3 value promoted shear failure,whereas a largerσ3 value inhibited it.Furthermore,the appropriate dataset selection range to accurately calculate the cohesion force and internal friction angle in CTTs and variable-angle shear tests was determined.
基金Projects (50934006, 51074178) supported by the National Natural Science Foundation of ChinaProject (2010QZZD001) supported by the Fundamental Research Funds for the Central Universities of China
文摘Taking the test stopes during continuous mining induced roof caving of Tongkeng ore-body No.92 as example, the calculation flow of unloading analysis was established. According to the unloading region division method of the affected zone theory, and the deterioration laws of mechanics parameters of unloading rock mass, the continuous mining process in underground mine was analyzed by the software MIDAS/GTS, the mechanical response of roof rock mass unloading was studied, and the differences were analyzed with the conventional simulation. The result shows that the maximum tensile stress, subsidence displacement and equivalent plastic strain of roof rock mass are 1.5 MPa, 20 cm and 1.5% in the unloading analysis, while 1.0 MPa, 13 cm and 0.9% in the conventional analysis. The values of unloading analysis, which are also closer to the actual situation, are greater than those of conventional analysis; the maximum step in continuous mining is 48 m, which shows that the induced treatment of the roof should be carried out after 2 mining steps
基金supported by the National Science Foundation for Young Scientists of China(grant numbers ZR2024QE402).
文摘To enable real-time prediction of rock mechanical parameters during drilling,this study proposes a method based on vibration-while-drilling(VWD)spectral features.Three-component vibration signals were collected experimentally,and their dominant frequency,low-frequency energy,and spectral centroid were extracted as predictors.A ridge regression model was developed to map these spectral features to rock mechanical parameters.Compared with conventional drilling parameters,the spectral descriptors capture lithology-dependent stiffness more effectively,with the low-frequency(0-20 Hz)energy showing a strong correlation with rock strength.Validation on tuspecimens achieved high accuracy(mean R^(2)>0.80)and stable calibration between predicted and measured values.Bootstrap and permutation analyses conrmed the consistency and interpretability of feature contributions,while ridge-penalty scanning demonstrated strong resistance to overtting.The proposed approach provides an efcient and interpretable framework for realtime eld prediction of rock mechanical parameters and oers a foundation for multi-lithology and physicsinformed model extensions.
文摘Based on the classical static theory and static numerical simulation,the static method could not accurately reflect the stability of goaf where the rocks on the pillar and roof are influenced by Theological and blasting disturbance for a long time.According to the test from the site,an experimental study was made in Theological and dynamic disturbance.After that,on the basis of variable rock mechanics parameters from the experimental data,numerical simulation was used to analyze the vertical stress distribution of goaf,vertical displacement and plastic area of roof in the "deterioration" caused by Theological and blasting,which shows that the mechanics properties of the rock were greatly influenced by Theological,and dynamic disturbance.The results of the experimental study and numerical simulation show that the mechanics properties of rock are greatly influenced by Theological and dynamic disturbance.As a result,the stability of goaf is greatly reduced.Finally,by comparing golf monitoring results with the analysis of theoretical calculation,it was found that the results were approximately the same,which testifies the reliability of the method.This method provides a new way of studying the stability of goaf as well as laying a basic foundation for future safety management.
