A series of uniaxial-compression tests were conducted on some granite speci- mens.A multi-channel,high-speed AE signal acquiring and analyzing system was em- ployed to acquire and record the characteristics of AE even...A series of uniaxial-compression tests were conducted on some granite speci- mens.A multi-channel,high-speed AE signal acquiring and analyzing system was em- ployed to acquire and record the characteristics of AE events and demonstrate the tem- poral and spatial distribution of these events during the failure process.The test results show that in the primary stage,many low amplitude AE events are developed rapidly and distributed randomly throughout the entire specimens.In the second stage,the number of AE increases much slower than that in the first stage,while the amplitude of most AE events became greater.Contrarily to the primary stage,AE events clusteres in the middle area of the specimen and distributes vertically conformed to the orientation of compres- sion.The most distinct characteristic of this stage is a vacant gap formed approximately in the central part of the specimen.In the last stage,the number of AE events increases sharply and their magnitude increases accordingly.The final failure location coincidently inhabited the aforementioned gap.The main conclusion is that most macrocracks are de- veloped from the surrounding microcracks existed earlier and their positions occupy the earlier formed gaps,and the AE activity usually becomes quite acute before the main rup- ture occurs.展开更多
In the simulation of rupture processes of seismic sources by using either numerical method or rock mechanics experiments, improper setting of the specimen size will influence the stress field near the faults. In this ...In the simulation of rupture processes of seismic sources by using either numerical method or rock mechanics experiments, improper setting of the specimen size will influence the stress field near the faults. In this study, 2D finite element method (FEM) was used to calculate the stress field of rock specimens in different sizes with fixed-size elliptic holes. The calculated stress field was compared with analytic solution for elliptic-hole problem in an infinite medium. Numerical results showed that boundary effect of a rock specimen with an elliptic hole on stress field under uniaxial compression cannot be neglected. Critical aspect ratio of the specimen is about 3:2, and critical ratio of distance between the tip of the hole and the border of specimen (d) to the major axis of the elliptic hole (l) is about 7.3. Numerical analysis on rock specimen size can provide theoretical reference for rock specimen experiments, and it is also helpful for setting of model sizes in numerical simulations of fault movement.展开更多
Although hydraulic fracturing is the most commonly used method for fracturing of shale-gas-bearing rock,there are some problems with this method.As plasma blasting can fracture rock without these problems,laboratory-s...Although hydraulic fracturing is the most commonly used method for fracturing of shale-gas-bearing rock,there are some problems with this method.As plasma blasting can fracture rock without these problems,laboratory-scale fracturing of cement and rock specimens by plasma blasting was performed to investigate the possibility of using this method in shale gas development.展开更多
Anti symmetric four point bending specimens with different thickness, without and with guiding grooves, were used to conduct Mode Ⅱ fracture test and study the effect of specimen thickness on Mode Ⅱ fracture toughne...Anti symmetric four point bending specimens with different thickness, without and with guiding grooves, were used to conduct Mode Ⅱ fracture test and study the effect of specimen thickness on Mode Ⅱ fracture toughness of rock. Numerical calculations show that the occurrence of Mode Ⅱ fracture in the specimens without guiding grooves (when the inner and outer loading points are moved close to the notch plane) and with guiding grooves is attributed to a favorable stress condition created for Mode Ⅱ fracture, i.e. tensile stress at the notch tip is depressed to be lower than the tensile strength or to be compressive stress, and the ratio of shear stress to tensile stress at notch tip is very high. The measured value of Mode Ⅱ fracture toughness K ⅡC decreases with the increase of the specimen thickness or the net thickness of specimen. This is because a thick specimen promotes a plane strain state and thus results in a relatively small fracture toughness.展开更多
The naming of rock hand specimens is usually conducted by geological workers based on observed mineral composition,texture characteristics,etc.,combined with their own knowledge reserves.The accuracy of identification...The naming of rock hand specimens is usually conducted by geological workers based on observed mineral composition,texture characteristics,etc.,combined with their own knowledge reserves.The accuracy of identification results is limited by the experience,research interests,and identification level of the identifier,as well as the complexity of the rock composition.To improve the efficiency of rock hand specimen identification,this paper proposes a method for rock image recognition and classification based on deep learning and the Inception-v3 model.It encompasses the preprocessing of collected photographs of typical intrusive rock hand specimens,along with augmenting the sample size through data augmentation methods,culminating in a comprehensive dataset comprising 12501 samples.Experimental results show that the model has good learning ability when there is sufficient data.Through iterative training of the Inception-v3 model on the rock dataset,the accuracy of rock image recognition reaches 92.83%,with a loss of only 0.2156.Currently,several common types of intrusive rocks can be identified:gabbro,granite,diorite,peridotite,granodiorite,diabase,and granite porphyry.Software is developed for open use by geological workers to improve work efficiency.展开更多
As Daqing Oilfield is developing oil layer with a big potential, the requirement for the quality of well cementation is higher than ever before. Cement rock is a brittle material containing a great number of microcrac...As Daqing Oilfield is developing oil layer with a big potential, the requirement for the quality of well cementation is higher than ever before. Cement rock is a brittle material containing a great number of microcracks and defects. In order to reduce the damage to cement ring and improve sealed cementing property at the interface, it is necessary to conduct research on the modification of the cement rock available. According to the principle of super mixed composite materials, various fillers are added to the ingredients of cement rock. Dynamic fracture toughness of cement rock will be changed under the influence of filler. In this paper, short rod specimens of cement rock are employed in the experiments to investigate the dynamic fracture toughness of cement rocks with different ingredients using split Hopkinson Pressure Bar, and partial experimental results are given. The results indicate that fiber reinforcement is an effective way to improve the impact resistance of cement rock.展开更多
This investigation aims to explore the effects of stress conditions and rock cutting rates on hard rock fragmentation through indentation tests on a newly designed triaxial testing apparatus.This apparatus was designe...This investigation aims to explore the effects of stress conditions and rock cutting rates on hard rock fragmentation through indentation tests on a newly designed triaxial testing apparatus.This apparatus was designed to realize a triaxial loading and indentation test of cylindrical specimens using inserted tooth cutter.The boreability and crushing efficiency of granite rock was investigated by analyzing the change rules of the thrusting force,penetration depth,characteristics of chippings and failure patterns.Several quantitative indexes were used to evaluate rock boreability in this investigation.The granite rock samples all had a chiselled pit and a crushed rock core.Under initial stress conditions,only flat-shape chippings were stripped from the rock surface when the thrusting force reached 20 kN.The rock cutting special energy had a close correlation with the initial stress conditions and inserted tooth shape.Moreover,a thrusting force prediction model was proposed in this paper.The contribution of this study is that for the first time the influence mechanism of the initial triaxial stress conditions on rock fragmentation is investigated using an inserted tooth and the newly designed testing apparatus.This study has a crucial importance for practical underground hard rock crushing in geoengineering.展开更多
Subcritical crack growth of double torsion specimens made of ore, lherzolite, marble and granite was studied using Instron1342 type electro hydraulic servo test machine. The relations of the mode-I stress intensity fa...Subcritical crack growth of double torsion specimens made of ore, lherzolite, marble and granite was studied using Instron1342 type electro hydraulic servo test machine. The relations of the mode-I stress intensity factor KI versus the subcritical crack growth velocity v and the fracture toughness KIC were obtained by the double torsion constant displacement load relaxation method. The behavior of subcritical crack growth was analyzed for different rocks. The results show that lgKI—lgv relations of four kinds of rocks measured by this method accord with linear rule, i.e. the relations between subcritical crack growth velocity and stress intensity factor have a power law, which is in good agreement with CHARLES theory. lgKI—lgv curves move to top left corner with the decrease of the elastic modulus, which implies that the subcritical crack growth velocity speeds up. The maximum subcritical crack growth velocity exhibits negative exponential increase, and mode-I fracture toughness KIC decreases with the decrease of elastic modulus. The testing results provide a basis for time-dependence of rock engineering stability.展开更多
试件尺度的岩石受载破裂过程中,其本身结构发生变形、破坏的同时,包含了地球物理属性参数信息的变化,如应变量、电阻率、波速等。通过对受载中的岩石试件进行地球物理参数测试,可定性或定量地感知其内部结构、强度等特征变化,有助于了...试件尺度的岩石受载破裂过程中,其本身结构发生变形、破坏的同时,包含了地球物理属性参数信息的变化,如应变量、电阻率、波速等。通过对受载中的岩石试件进行地球物理参数测试,可定性或定量地感知其内部结构、强度等特征变化,有助于了解岩石试件破裂机理,进而解决一系列岩体工程测试问题。基于Web of Science论文检索系统搜索出岩石试件加载测试的文献资料,利用CiteSpace软件对岩石试件加载测试现状进行分析,并详细阐述了几种常用测试方法的原理及研究进展。结合煤系地层深部采场领域研究现状,分析、总结岩石试件受载测试研究过程中存在的不足,并对地球物理参数采集、装置研发与微-宏观测试融合等方面提出展望。展开更多
基金the Special Subject of 863 Programm(2007AA06Z107)the Younth Foundation of HPU(Q2008-51)
文摘A series of uniaxial-compression tests were conducted on some granite speci- mens.A multi-channel,high-speed AE signal acquiring and analyzing system was em- ployed to acquire and record the characteristics of AE events and demonstrate the tem- poral and spatial distribution of these events during the failure process.The test results show that in the primary stage,many low amplitude AE events are developed rapidly and distributed randomly throughout the entire specimens.In the second stage,the number of AE increases much slower than that in the first stage,while the amplitude of most AE events became greater.Contrarily to the primary stage,AE events clusteres in the middle area of the specimen and distributes vertically conformed to the orientation of compres- sion.The most distinct characteristic of this stage is a vacant gap formed approximately in the central part of the specimen.In the last stage,the number of AE events increases sharply and their magnitude increases accordingly.The final failure location coincidently inhabited the aforementioned gap.The main conclusion is that most macrocracks are de- veloped from the surrounding microcracks existed earlier and their positions occupy the earlier formed gaps,and the AE activity usually becomes quite acute before the main rup- ture occurs.
基金National Natural Science Foundation of China (40234042).
文摘In the simulation of rupture processes of seismic sources by using either numerical method or rock mechanics experiments, improper setting of the specimen size will influence the stress field near the faults. In this study, 2D finite element method (FEM) was used to calculate the stress field of rock specimens in different sizes with fixed-size elliptic holes. The calculated stress field was compared with analytic solution for elliptic-hole problem in an infinite medium. Numerical results showed that boundary effect of a rock specimen with an elliptic hole on stress field under uniaxial compression cannot be neglected. Critical aspect ratio of the specimen is about 3:2, and critical ratio of distance between the tip of the hole and the border of specimen (d) to the major axis of the elliptic hole (l) is about 7.3. Numerical analysis on rock specimen size can provide theoretical reference for rock specimen experiments, and it is also helpful for setting of model sizes in numerical simulations of fault movement.
基金supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(2019R1A6A1A03033167).
文摘Although hydraulic fracturing is the most commonly used method for fracturing of shale-gas-bearing rock,there are some problems with this method.As plasma blasting can fracture rock without these problems,laboratory-scale fracturing of cement and rock specimens by plasma blasting was performed to investigate the possibility of using this method in shale gas development.
基金TheNationalNaturalScienceFoundationofChina (No :496 72 16 4)
文摘Anti symmetric four point bending specimens with different thickness, without and with guiding grooves, were used to conduct Mode Ⅱ fracture test and study the effect of specimen thickness on Mode Ⅱ fracture toughness of rock. Numerical calculations show that the occurrence of Mode Ⅱ fracture in the specimens without guiding grooves (when the inner and outer loading points are moved close to the notch plane) and with guiding grooves is attributed to a favorable stress condition created for Mode Ⅱ fracture, i.e. tensile stress at the notch tip is depressed to be lower than the tensile strength or to be compressive stress, and the ratio of shear stress to tensile stress at notch tip is very high. The measured value of Mode Ⅱ fracture toughness K ⅡC decreases with the increase of the specimen thickness or the net thickness of specimen. This is because a thick specimen promotes a plane strain state and thus results in a relatively small fracture toughness.
基金Supported by the Qinghai Province Geological Exploration Fund Project(2023085029ky004)Natural Science Foundation of Jilin Provinc(20220101161JC)Open Project Plan of Shandong Province Deep Gold Exploration in Big Data Application and Development Engineering Laboratory(SDK202203).
文摘The naming of rock hand specimens is usually conducted by geological workers based on observed mineral composition,texture characteristics,etc.,combined with their own knowledge reserves.The accuracy of identification results is limited by the experience,research interests,and identification level of the identifier,as well as the complexity of the rock composition.To improve the efficiency of rock hand specimen identification,this paper proposes a method for rock image recognition and classification based on deep learning and the Inception-v3 model.It encompasses the preprocessing of collected photographs of typical intrusive rock hand specimens,along with augmenting the sample size through data augmentation methods,culminating in a comprehensive dataset comprising 12501 samples.Experimental results show that the model has good learning ability when there is sufficient data.Through iterative training of the Inception-v3 model on the rock dataset,the accuracy of rock image recognition reaches 92.83%,with a loss of only 0.2156.Currently,several common types of intrusive rocks can be identified:gabbro,granite,diorite,peridotite,granodiorite,diabase,and granite porphyry.Software is developed for open use by geological workers to improve work efficiency.
文摘As Daqing Oilfield is developing oil layer with a big potential, the requirement for the quality of well cementation is higher than ever before. Cement rock is a brittle material containing a great number of microcracks and defects. In order to reduce the damage to cement ring and improve sealed cementing property at the interface, it is necessary to conduct research on the modification of the cement rock available. According to the principle of super mixed composite materials, various fillers are added to the ingredients of cement rock. Dynamic fracture toughness of cement rock will be changed under the influence of filler. In this paper, short rod specimens of cement rock are employed in the experiments to investigate the dynamic fracture toughness of cement rocks with different ingredients using split Hopkinson Pressure Bar, and partial experimental results are given. The results indicate that fiber reinforcement is an effective way to improve the impact resistance of cement rock.
基金The authors gratefully acknowledge the financial support from Natural Science Research Project of Universities in Anhui Province(No.KJ2021A0463)Scientific Research Startup Fund for introduced talents of Anhui University of Science and Technology,and Natural Science Foundation of Anhui Province(No.2108085QE208).
文摘This investigation aims to explore the effects of stress conditions and rock cutting rates on hard rock fragmentation through indentation tests on a newly designed triaxial testing apparatus.This apparatus was designed to realize a triaxial loading and indentation test of cylindrical specimens using inserted tooth cutter.The boreability and crushing efficiency of granite rock was investigated by analyzing the change rules of the thrusting force,penetration depth,characteristics of chippings and failure patterns.Several quantitative indexes were used to evaluate rock boreability in this investigation.The granite rock samples all had a chiselled pit and a crushed rock core.Under initial stress conditions,only flat-shape chippings were stripped from the rock surface when the thrusting force reached 20 kN.The rock cutting special energy had a close correlation with the initial stress conditions and inserted tooth shape.Moreover,a thrusting force prediction model was proposed in this paper.The contribution of this study is that for the first time the influence mechanism of the initial triaxial stress conditions on rock fragmentation is investigated using an inserted tooth and the newly designed testing apparatus.This study has a crucial importance for practical underground hard rock crushing in geoengineering.
基金Project(50274074) supported by the National Nature Science Foundation of China Key Project(50490274) supported by the National Nature Science Foundation of China
文摘Subcritical crack growth of double torsion specimens made of ore, lherzolite, marble and granite was studied using Instron1342 type electro hydraulic servo test machine. The relations of the mode-I stress intensity factor KI versus the subcritical crack growth velocity v and the fracture toughness KIC were obtained by the double torsion constant displacement load relaxation method. The behavior of subcritical crack growth was analyzed for different rocks. The results show that lgKI—lgv relations of four kinds of rocks measured by this method accord with linear rule, i.e. the relations between subcritical crack growth velocity and stress intensity factor have a power law, which is in good agreement with CHARLES theory. lgKI—lgv curves move to top left corner with the decrease of the elastic modulus, which implies that the subcritical crack growth velocity speeds up. The maximum subcritical crack growth velocity exhibits negative exponential increase, and mode-I fracture toughness KIC decreases with the decrease of elastic modulus. The testing results provide a basis for time-dependence of rock engineering stability.
文摘试件尺度的岩石受载破裂过程中,其本身结构发生变形、破坏的同时,包含了地球物理属性参数信息的变化,如应变量、电阻率、波速等。通过对受载中的岩石试件进行地球物理参数测试,可定性或定量地感知其内部结构、强度等特征变化,有助于了解岩石试件破裂机理,进而解决一系列岩体工程测试问题。基于Web of Science论文检索系统搜索出岩石试件加载测试的文献资料,利用CiteSpace软件对岩石试件加载测试现状进行分析,并详细阐述了几种常用测试方法的原理及研究进展。结合煤系地层深部采场领域研究现状,分析、总结岩石试件受载测试研究过程中存在的不足,并对地球物理参数采集、装置研发与微-宏观测试融合等方面提出展望。
