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Fan‐hinged shear instead of frictional stick–slip as the main and most dangerous mechanism of natural,induced,and volcanic earthquakes in the earth's crust

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Deep Underground Science and Engineering 2023年第4期2卷 305-336页

作者： Boris G.Tarasov laboratory of geomechanics of highly stressed rock and massives Far Eastern Federal UniversityVladivostokRussia

Frictional stick–slip instability along pre‐existing faults has been accepted as the main mechanism of earthquakes for about 60 years,since it is believed that fracture of intact rocks cannot reﬂect such features inherent in earthquakes as low shear stresses activating instability,low stress drop,repetitive dynamic instability,and connection with pre‐existing *** paper demonstrates that all these features can be induced by a recently discovered shear rupture mechanism(fan‐hinged),which creates dynamic ruptures in intact rocks under stress conditions corresponding to seismogenic *** key element of this mechanism is the fan‐shaped structure of the head of extreme ruptures,which is formed as a result of an intense tensile cracking process,with the creation of inter‐crack slabs that act as hinges between the shearing rupture *** preference of the fan mechanism over the stick–slip mechanism is clear due to the extraordinary properties of the fan structure,which include the ability to generate new faults in intact dry rocks even at shear stresses that are an order of magnitude lower than the frictional strength;to provide shear resistance close to zero and abnormally large energy release;to cause a low stress drop;to use a new physics of energy supply to the rupture tip,providing supersonic rupture velocity;and to provide a previously unknown interrelation between earthquakes and *** these properties make the fan mechanism the most dangerous rupture mechanism at the seismogenic depths of the earth's crust,generating the vast majority of *** detailed analysis of the fan mechanism is presented in the companion paper“New physics of supersonic ruptures”published in *** study of this subject is a major challenge for deep underground science,earthquake and fracture mechanics,volcanoes,physics,and tribology.

关键词： earthquake and rockburst mechanisms interrelation of earthquakes and volcanoes physics of supersonic ruptures postpeak rock properties rock rupture mechanism rupture energy budget

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New physics of supersonic ruptures

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Deep Underground Science and Engineering 2023年第3期2卷 207-244页

作者： Boris G.Tarasov laboratory of geomechanics of highly stressed rock and massives Far Eastern Federal UniversityVladivostokRussia

Until recently,it is believed that the rupture speed above the pressure wave is impossible since spontaneously propagating ruptures are driven by the energy released due to the rupture motion,which is transferred through the medium to the rupture tip region at the maximum speed equal to the pressure wave ***,the apparent violation of classic theories has been revealed by new experimental results demonstrating supersonic shear *** paper presents a detailed analysis of the recently discovered shear rupture mechanism(fan hinged),which suggests a new physics of energy supply to the tip of supersonic *** key element of this mechanism is the fan‐shaped structure of the head of extreme ruptures,which is formed as a result of an intense tensile cracking process with the creation of intercrack slabs that act as hinges between the shearing rupture *** fan structure is featured with the following extraordinary properties:extremely low friction approaching zero;amplification of shear stresses above the material strength at low applied shear stresses;creation of a self‐disbalancing stress state causing a spontaneous rupture growth;abnormally high energy release;generation of driving energy directly at the rupture tip which excludes the need to transfer energy through the *** fan mechanism operates in intact rocks at stress conditions corresponding to seismogenic depths and in pre‐existing extremely smooth interfaces due to identical tensile cracking processes at these *** is Paper 1(of two companion papers)which discusses the fan theory and extreme ruptures in experiments on extremely smooth *** 2 entitled“Fan‐hinged shear instead of frictional stick‐slip as the main and most dangerous mechanism of natural,induced and volcanic earthquakes in the earth's crust”considers extreme ruptures in intact *** study of this subject is a major challenge for deep underground science,earthquake and fracture mechanics

关键词： fan‐hinged rupture mechanism laboratory earthquakes on extremely smooth interfaces physics of supershear and supersonic ruptures rupture energy budget

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Temperature influence on macro-mechanics parameter of intact coal sample containing original gas from Baijiao Coal Mine in China

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International Journal of Mining Science and Technology 2013年第4期23卷 584-589页

作者： Wang Chunguang He Manchao Zhang Xiaohu Liu Zhaoxia Zhao Tongbin State Key laboratory of Mining Disaster Prevention and Control Shandong University of Science & Technology Institute of rock and Soil Mechanics Chinese Academy of Sciences State Key laboratory of geomechanics and Deep Underground Engineering China University of Mining & Technology

Investigation of temperature effect on mechanical parameters of coal is very important for understanding the mechanical response of coal bed at high *** is especially benefcial for mitigating the thermal-induced disasters occurred in those coal mines suffering from heat *** this work,coal samples,obtained from the No.2442 working face of Baijiao Coal Mine,were subjected to uniaxial compression ranging from 20 to 40℃ with an interval of 5℃.The apparatus used was designed to obtain deformation of a stressed sample,as well as the emission of gases desorbing from coal *** adsorbed gas desorption caused by heating is measured during the entire *** is evident that the concentrations of releasing gas(containing methane,carbon dioxide and ethane)slightly rise with increasing *** movement observed is closely related to the deformation of coal *** uniaxial compressive strength and elastic modulus of coal samples tend to reduce with *** reveals that increasing temperature can not only result in thermal expansion of coal,but also lead to desorption of preexisting gas in coal which can in turns harden coal due to shrinks of the coal *** though desorption of adsorbed gas can contribute to the hardening effect for the heated coal,by comparison to the results,it could be inferred that the softening of coal resulted from thermal expansion still predominates changes in mechanical characters of coal sample with temperature at the range from20 to 40℃.

关键词： Gas flow Coupling of temperature and pressure Adsorption Desorption

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Experimental investigation on rockburst characteristics of highly stressed D-shape tunnel subjected to impact load

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Underground Space 2024年第6期19卷 153-168页

作者： Wuxing Wu Fengqiang Gong Zongxian Zhang School of Civil Engineering Southeast UniversityNanjing 211189China State Key laboratory of geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan 430071China Oulu Mining School University of OuluOulu 90570Finland

rockburst has always been a challenge for the safe construction of deep underground *** study investigated the rockburst characteristics in highly-stressed D-shape tunnels under impact loads from rock blasting and other mining-related dynamics *** biaxial Hopkinson pressure bar was utilized to apply varying biaxial prestress and the same impact loads to cube specimens with D-shape ***-speed camera and digital image correlation(DIC)were used to capture the failure process and strain field of *** test results demonstrate that the D-shape hole specimen experience rockburst under coupled static stress and impact *** this circumstance,the rockburst mechanism of the D-shaped hole specimens involves spalling in sidewall induced by impact load,indicating dynamic tensile *** high static prestress provides the initial stress field,while the impact load disrupts the stress equilibrium,result in the stress or strain concentration in the sidewall of the D-shape hole,inducing ***,the rockburst process can be divided into(1)calm stage,(2)crack initiation,propagation,and coalesce stage,(3)spalling stage and(4)rock fragments ejection *** load triggers rockburst occurrence,while vertical stress further determines the rockburst *** influence range and magnitude of strain concentration zone and displacement deformation of the tunnel surrounding rock increases with increasing vertical stress,thus inducing more severe rockburst.

关键词： rockburst Spalling D-shape tunnel Impact load Biaxial prestresses Biaxial Hopkinson pressure bar

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rock damage and fracturing induced by high static stress and slightly dynamic disturbance with acoustic emission and digital image correlation techniques

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Journal of rock Mechanics and Geotechnical Engineering 2021年第5期13卷 1002-1019页

作者： Shuting Miao Peng-Zhi Pan Petr Konicek Peiyang Yu Kunlun Liu State Key laboratory of geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China University of Chinese Academy of Sciences Beijing100049China Department of geomechanics and Mining Research Institute of Geonics of the Czech Academy of SciencesOstrava70800Czech Republic Shenhua Xinjiang Energy Company Limited Urumqi830027China

A series of coupled static-dynamic loading tests is carried out in this study to understand the effect of slightly dynamic disturbance on the rocks under high static *** acoustic emission(AE)and digital image correlation(DIC)techniques are combined to quantitatively characterize the damage and fracturing behaviors of *** effects of three influencing factors,*** static stress,disturbance amplitude,and disturbance frequency,on the damage and fracturing evolution are *** experimental results reveal the great differences in AE characteristics and fracturing behaviors of rocks under static loads and coupled static-dynamic *** the Kaiser effect and Felicity effect are observed during the disturbance loading *** crack initiation,stable and unstable propagation in the highly-stressed rocks can be triggered by cyclic disturbance loads,and more local tensile splitting cracks are found in the rocks subjected to coupled static-dynamic *** damage and fracturing evolution of rocks during cyclic disturbances can be divided into two stages,*** and accelerated stages,and the increase rate and proportion of each stage are greatly affected by these influencing *** initial static stress,low disturbance frequency,and high disturbance amplitude are considered to be adverse factors to the stability of the rocks,which would induce a high increase rate of the steady stage and a high proportion of the accelerated stage within the whole disturbance *** on the two-stage damage evolution trend,a linear-exponential damage model is employed to predict the instability of the rocks under coupled static-dynamic loads.

关键词： Damage evolution Fracture behaviors High static stress Dynamic disturbance Damage model

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3D finite element modelling of multilateral junction wellbore stability

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Petroleum Science 2018年第4期15卷 801-814页

作者： Assef Mohamad-Hussein Juliane Heiland Schlumberger Geomechanics Center of ExcellenceBuckingham Gate

Wellbore failure can occur at different stages of operations. For example, wellbore collapse might happen during drilling and/or during production. The drilling process results in the removal of an already stressed rock material. If the induced stresses near the wellbore exceed the strength of rock, wellbore failure occurs. The production process also changes the effective stresses around the wellbore. Such changes in stresses can be significant for high drawdown pressures and can trigger wellbore failure. In this paper, the Mohr–Coulomb failure criterion with a hyperbolic hardening is used. The model parameters are identified from triaxial compression tests. The numerical simulations of laboratory tests showed that the model can reproduce the mechanical behaviour of sandstone. In addition, the simulations of multilateral junction stability experiments showed that the model was able to reproduce yielding and failure at the multilateral junction for different levels of applied stresses. Finally, a numerical example examining multilateral junction stability in an open borehole during drilling and production is presented. The results illustrate the development of a localized failure zone proximate to the area where two wellbore tracks join, particularly on the side with a sharp approaching angle, which would significantly increase the risk of wellbore collapse at the junction.

关键词： Multilateral junction Numerical modelling Stability

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Principle of in-situ 3D rock stress measurement with borehole wall stress relief method and its preliminary applications to determination of in-situ rock stress orientation and magnitude in Jinping hydropower station

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Science China(Technological Sciences) 2012年第4期55卷 939-949页

作者： GE XiuRun HOU MingXun Institute of Geotechnical Engineering Shanghai Jiaotong UniversityShanghai 200240China Institute of rock and Soil Mechanics Chinese Academy of SciencesWuhan 430071China State Key laboratory of geomechanics and Geotechnical Engineering Wuhan 430071China

As a main constituent of geological body, the rock masses have distinct differences from other materials, one of which is that rock masses are initially stressed in their natural states. Hence, it is an extremely challenging and significant research project to know the present residual stress of the rock masses in the earth's crust. Although some regularities of distribution of in-situ rock stresses can be deduced, the basic means to study the state of rock stress is in-situ stress measurement. After a brief review of several measuring methods of in-situ 3D rock stress, a new one, borehole wall stress relief method (BWSRM) to determine the in-situ 3D rock stress tensor in a single drilled borehole was proposed. Based on the principle of in-situ rock stress measurement with BWSRM, an original geostress measuring instrument was designed and manufactured. Preliminary experiments for determination of in-situ stress orientation and magnitude were carried out at an experimental tunnel in Jinping Ⅱ hydropower station in China, where the buried depth of overburden was about 2430 m. The results showed that it was feasible to measure the in-situ 3D rock stresses with BWSRM presented in this paper. The BWSRM has a broad prospect for in-situ 3D rock stress measurements in practical rock engineering.

关键词： rock mechanics and engineering in-situ rock stress measurement stress relief method Jinping hydropower engineering

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Analysis of rockburst in tunnels subjected to static and dynamic loads

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Journal of rock Mechanics and Geotechnical Engineering 2017年第6期9卷 1031-1040页

作者： Amin Manouchehrian Ming Cai Bharti School of Engineering Laurentian University Sudbury P3E 2C6 Canada MIRARCO Laurentian University 935 Ramsey Lake Road Sudbury P3E 2C6 Canada State Key laboratory of geomechanics and Geotechnical Engineering Institute of Rock and Soil Mechanics Chinese Academy of Sciences Wuhan 430071Hubei China

The presence of geological structures such as faults, joints, and dykes has been observed near excavation boundaries in many rockburst case histories. In this paper, the role of discontinuities around tunnels in rockburst occurrence was studied. For this purpose, the Abaqus explicit code was used to simulate dynamic rock failure in deep tunnels. Material heterogeneity was considered using Python scripting in Abaqus. rockbursts near fault regions in deep tunnels under static and dynamic loads were *** tunnel models with and without faults were built and static and dynamic loads were used to simulate rock failure. The velocity and the released kinetic energy of failed rocks, the failure zone around the tunnel, and the deformed mesh were studied to identify stable and unstable rock failures. Compared with models without discontinuities, the results showed that the velocity and the released kinetic energy of failed rocks were higher, the failure zone around the tunnel was larger, and the mesh was more deformed in the models with discontinuities, indicating that rock failure in the models with discontinuities was more violent. The modeling results confirm that the presence of geological structures in the vicinity of deep excavations could be one of the major influence factors for the occurrence of rockburst. It can explain localized rockburst occurrence in civil tunnels and mining drifts. The presented methodology in this paper for rockburst analysis can be useful for rockburst anticipation and control during mining and tunneling in highly stressed ground.

关键词： rockburst Numerical modeling Geological structure Static load increase Dynamic disturbance Tunnel

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A study of support strategies in deep soft rock:The horsehead crossing roadway in Daqiang Coal Mine

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International Journal of Mining Science and Technology 2012年第5期22卷 665-667页

作者： Guo Zhibiao Yang Xiaojie Bai Yunpeng Zhou Feng Li Erqiang State Key laboratory of geomechanics and Deep Underground Engineering China University of Mining & Technology. Beijing 100083 China School of Mechanics and Civil Engineering China University of Mining and Technology. Beijing 100083 China

geomechanics in deep mines becomes more complex and structural support in soft rock can be very *** stressed soft rock subject to expansion deformation is particularly difficult to *** Tiefa Coal Industry Group Daqiang Coal Mine is used as an example.A ventilation shaft,à550 horsehead,is located in tertiary soft *** of the reasons for deformation shows an intumescent rock,which is easily *** observations and theoretical analysis led to a design capable of stabilizing the rock.A combination of spray,anchors,anchor bolts,and soft corner coupled truss supports allowed the deformation to be *** provides a model for similar designs when support of a horsehead roadway is required.

关键词： Deep well Soft rock Horsehead Deformation mechanical mechanism Coupling support

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Strength weakening effect of high static pre-stressed granite subjected to low-frequency dynamic disturbance under uniaxial compression

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Transactions of Nonferrous Metals Society of China 2022年第7期32卷 2353-2369页

作者： Wu-xing WU Feng-qiang GONG Quan JIANG Engineering Research Center of Safety and Protection of Explosion&Impact of Ministry of Education(ERCSPEIME) Southeast UniversityNanjing 211189China School of Civil Engineering Southeast UniversityNanjing 211189China State Key laboratory of geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan 430071China

This study aimed to elucidate the strength weakening effect of high static pre-stressed rocks subjected to low-frequency disturbances under uniaxial *** on the uniaxial compressive strength(UCS)of granite under static loading,70%,80%,and 90%of UCS were selected as the initial high static pre-stress(σ_(p)),and then the pre-stressed rock specimens were disturbed by sinusoidal stress with amplitudes of 30%,20%,and 10%of UCS under low-frequency frequencies(f)of 1,2,5,and 10 Hz,*** results show that the rockburst failure of pre-stressed granite is caused by low-frequency disturbance,and the failure strength is much lower than *** theσp or f is constant,the specimen strength gradually decreases as the f or σ_(p) *** experimental study illustrates the influence mechanism of the strength weakening effect of high static pre-stress rocks under low-frequency dynamic disturbance,that is,high static pre-stress is the premise and leading factor of rock strength weakening,while low-frequency dynamic disturbance induces rock failure and affects the strength weakening degree.

关键词： deep rock high static pre-stress low-frequency dynamic disturbance strength weakening effect uniaxial compression rockburst

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