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A thermo-mechanical damage constitutive model for deep rock considering brittleness-ductility transition characteristics

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Journal of Central South University 2024年第7期31卷 2379-2392页

作者： FENG Chen-chen WANG Zhi-liang WANG Jian-guo LU Zhi-tang LI Song-yu School of Civil and Hydraulic Engineering Hefei University of TechnologyHefei 230009China School of Mechanics and Civil Engineering China University of Mining and TechnologyXuzhou 221116China School of Resources and Environmental Engineering Hefei University of TechnologyHefei 230009China

This paper developed a statistical damage constitutive model for deep rock by considering the effects of external load and thermal treatment temperature based on the distortion *** model parameters were determined through the extremum features of stress−strain ***,the model predictions were compared with experimental results of marble *** is found that when the treatment temperature rises,the coupling damage evolution curve shows an S-shape and the slope of ascending branch gradually decreases during the coupling damage evolution *** a constant temperature,confining pressure can suppress the expansion of *** the confining pressure increases the rock exhibits ductility characteristics,and the shape of coupling damage curve changes from an S-shape into a quasi-parabolic *** model can well characterize the influence of high temperature on the mechanical properties of deep rock and its brittleness-ductility transition characteristics under confining ***,it is suitable for sandstone and granite,especially in predicting the pre-peak stage and peak stress of stress−strain curve under the coupling action of confining pressure and high *** relevant results can provide a reference for further research on the constitutive relationship of rock-like materials and their engineering applications.

关键词： deep rock crack initiation threshold thermo-mechanical coupling statistical damage model distortion energy theory

Displacement of surrounding rock in a deep circular hole considering double moduli and strength-stiffness degradation

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Applied Mathematics and Mechanics(English Edition) 2020年第12期41卷 1847-1860页

作者： Zenghui ZHAO WeiSUN Shaojie CHEN Yuanhui FENG Weiming WANG College of Energy and Mining Engineering Shandong University of Science and TechnologyQingdao 266590Shandong ProvinceChina State Key Laboratory of Mining Disaster Prevention and Control Co-founded by Shandong Province and the Ministry of Science and Technology Qingdao 266590Shandong ProvinceChina College of Civil Engineering and Architecture Shandong University of Science and TechnologyQingdao 266590Shandong ProvinceChina

The problem of cavity stability widely exists in deep underground engineering and energy ***,the stress field of the surrounding rock under the uniform stress field is deduced based on a post-peak strength drop model considering the rock’s characteristics of constant modulus and double ***,the orthogonal non-associative flow rule is used to establish the displacement of the surrounding rock under constant modulus and double moduli,respectively,considering the stiffness degradation and dilatancy effects in the plastic region and assuming that the elastic strain in the plastic region satisfies the elastic constitutive ***,the evolution of the displacement in the surrounding rock is analyzed under the effects of the double modulus characteristics,the strength drop,the stiffness degradation,and the *** results show that the displacement solutions of the surrounding rock under constant modulus and double moduli have a unified *** coefficients of the expression are related to the stress field of the original rock,the elastic constant of the surrounding rock,the strength parameters,and the dilatancy *** strength drop,the stiffness degradation,and the dilatancy effects all have effects on the *** effects can be characterized by quantitative relationships.

关键词： deep rock double moduli strength-stiffness degradation circular hole displacement solution

Development and applications of the quasi‐dynamic triaxial apparatus for deep rocks

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deep Underground Science and Engineering 2024年第1期3卷 70-90页

作者： Jinzhi Luo Yanyan Cai Jin Yu Jianzhi Zhang Yaoliang Zhu Yao Wei School of Civil Engineering Huaqiao UniversityXiamenFujianChina Zijin School of Geology and Mining Fuzhou UniversityFuzhouChina

The mechanical behaviors of deep rocks have always posed a challenge for the implementation and safe operation of major underground engineering *** this end,this study modified the existing mainstream rock mechanics instruments equipped with a dynamic disturbance loading system and developed a second‐generation TFD‐2000/D triaxial *** first‐generation device is equipped with an independent disturbance system and an advanced EDC‐580 all‐digital servo controller,which can apply disturbing load independently,implement the function of cyclic disturbance,and combine dynamic and static *** instrument was found to be reliable for use in analyzing the damage process of rocks in the disturbance test of *** second‐generation instrument tackles three limitations of the first‐generation instrument:(i)it upgrades the strain measurement system and uses extensometers with linear variable differential transformers to accurately measure deformation;(ii)it uses the self‐balanced chamber to replace the Hoek–Franklin triaxial cell and auto‐balancing triaxial pressure chamber;and(iii)the loading rod is independently equipped with an EDC‐580 all‐digital servo controller,which measures precise *** experimental findings confirmed that the second‐generation instrument can be used for rock mechanics testing under cyclic disturbance loading,the disturbance–stress relaxation cycle,and the creep–fatigue *** this sense,the second‐generation instrument can be a useful addition to deep rock mechanical instruments and provide a valuable reference.

关键词： complex stress conditions deep rock disturbance loading modification of instrument rock mechanics

rockburst proneness criteria for rock materials:Review and new insights

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Journal of Central South University 2020年第10期27卷 2793-2821页

作者： GONG Feng-qiang WANG Yun-liang LUO Song School of Resources and Safety Engineering Central South UniversityChangsha 410083China School of Civil Engineering Southeast UniversityNanjing 211189China

To review the rockburst proneness(or tendency)criteria of rock materials and compare the judgment accuracy of them,twenty criteria were summarized,and their judgment accuracy was evaluated and compared based on the laboratory tests on fourteen types of *** study begins firstly by introducing the twenty rockburst proneness criteria,and their origins,definitions,calculation methods and grading standards were summarized in ***,to evaluate and compare the judgment accuracy of the twenty criteria,a series of laboratory tests were carried out on fourteen types of rocks,and the rockburst proneness judgment results of the twenty criteria for the fourteen types of rocks were obtained ***,to provide a unified basis for the judgment accuracy evaluation of above criteria,a classification standard(obtained according to the actual failure results and phenomena of rock specimen)of rockburst proneness in laboratory tests was *** judgment results of the twenty criteria were compared with the judgment results of this classification *** results show that the judgment results of the criterion based on residual elastic energy(REE)index are completely consistent with the actual rockburst proneness,and the other criteria have some inconsistent situations more or ***,the REE index is based on the linear energy storage law and defined in form of a difference value and considered the whole failure process,and these superior characteristics ensure its *** is believed that the criterion based on REE index is comparatively more accurate and scientific than other criteria,and it can be recommended to be applied to judge the rockburst proneness of rock materials.

关键词： deep rock rockburst rockburst proneness rockburst proneness criterion rock mechanics

Changes in the thermodynamic properties of alkaline granite after cyclic quenching following high temperature action

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International Journal of Mining Science and Technology 2021年第5期31卷 843-852页

作者： Jianjun Hu Heping Xie Qiang Sun Cunbao Li Guikang Liu College of Water Resource and Hydropower Sichuan UniversityChengdu 610065China Guangdong Provincial Key Laboratory of deep Earth Sciences and Geothermal Energy Exploitation and Utilization Institute of Deep Earth Sciences and Green EnergyCollege of Civil and Transportation EngineeringShenzhen UniversityShenzhen 518060China Shenzhen Key Laboratory of deep Underground Engineering Sciences and Green Energy Shenzhen UniversityShenzhen 518060China Geological Research Institute for Coal Green Mining Xi'an University of Science and TechnologyXi’an 710054China

During the development of hot dry rock,the research on thermal fatigue damage caused by thermal shock of cold and heat cycles is the basis that ensures the long-term utilization of geothermal resources,but there are not enough relevant studies at *** on this,the thermal damage tests of granite at different temperatures(250,350,450°C)and quenching cycles(1,5,10,15 cycles)were carried *** reveals the damage mechanism and heat transfer law of the quenching cycle effect on hot dry *** results show that with the increase of temperature and cycles,the uneven thermal expansion of minerals and the thermal shock caused by quenching promote the crack development of granite,resulting in the decrease of P-wave velocity,thermal conductivity and uniaxial compressive strength of ***,the COMSOL was used to simulate the heat transfer of hot dry rock under different heat treatment *** concluded that the increase in the number of quenching cycles reduced the heat transfer capacity of the granite,especially more than 10 quenching cycles,which also reflects that the thermal fatigue damage leads to a longer time for the temperature recovery of the hot dry rock *** addition,the three-dimensional nonlinear fitting relationship among thermal conductivity,temperature and cycle number was established for the first time,which can better reveal the change rule of thermal conductivity after quenching thermal fatigue effect of hot dry *** research results provide theoretical support for hot dry rock reservoir reconstruction and production efficiency evaluation.

关键词： Alkaline granite Quenching cycle Thermal conductivity P-wave velocity High-temperature deep rock

rockburst process and strength-weakening effect of the high-stress circular tunnel under internal unloading

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Journal of rock Mechanics and Geotechnical Engineering 2023年第4期15卷 864-885页

作者： Fengqiang Gong Wuxing Wu Li Ren Engineering Research Center of Safety and Protection of Explosion&Impact of Ministry of Education(ERCSPEIME) Southeast UniversityNanjing211189China School of Civil Engineering Southeast UniversityNanjing211189China Key Laboratory of deep Earth Science and Engineering Ministry of EducationSichuan UniversityChengdu610065China

To investigate the influence of unloading effect of a circular tunnel face on rockburst process,by innovatively combining rock drilling unloading devices and triaxial systems,the strain rockburst simulation under the entire stress path of“high initial stressþinternal unloadingþstress adjustment”(HUS test)was realized for the intact cubic red sandstone samples(100 mm×100 mm×100 mm).Comparative tests were conducted on cubic red sandstone samples with prefabricated circular holes(425 mm)under the stress path of“prefabricated circular hole+þhigh initial stress+stress adjustment”(PHS test),thereby highlighting the influence of internal unloading on rockburst *** test results revealed that with an increase in vertical stress,the sidewalls in both the HUS and PHS tests suffered strain rockburst *** with the PHS test,the initial failure stress in the HUS test is lower,and it is easier to induce sidewall *** indicates that the internal unloading influences the sidewall failure,causing an obvious strength-weakening effect,which becomes more significant with an increase in buried *** strain rockburst failure was more severe in the HUS test owing to the influence of internal unloading.V-shaped rockburst pits were formed in the HUS tests,whereas in the PHS test,arcshaped rockburst pits were *** was also found that strain rockburst failure may occur only when the rock has a certain degree of rockburst proneness.

关键词： rockburst Unloading Strength-weakening effect deep rock V-shaped notch Circular tunnel

Dynamic characteristics of high stressed red sandstone subjected to unloading and impact loads

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Journal of Central South University 2022年第2期29卷 596-610页

作者： GONG Feng-qiang ZHONG Wen-hui GAO Ming-zhong SI Xue-feng WU Wu-xing School of Resources and Safety Engineering Central South UniversityChangsha 410083China School of Civil Engineering Southeast UniversityNanjing 211189China Guangdong Provincial Key Laboratory of deep Earth Sciences and Geothermal Energy Exploitation and Utilization Shenzhen UniversityShenzhen 518060China

In the process of deep projects excavation,deep rock often experiences a full stress process from high stress to unloading and then to impact disturbance *** study the dynamic characteristics of three-dimensional high stressed red sandstone subjected to unloading and impact loads,impact compression tests were conducted on red sandstone under confining pressure unloading conditions using a modified split Hopkinson pressure *** disturbance tests of uniaxial pre-stressed rock were also conducted(without considering confining pressure unloading effect).The results demonstrate that the impact compression strength of red sandstone shows an obvious strain rate *** an approximately equal strain rate,the dynamic strength of red sandstone under confining unloading conditions is less than that in the uniaxial pre-stressed impact compression *** pressure unloading produces a strength-weakening effect,and the dynamic strength weakening factor(DSWF)is also *** results also indicate that the strain rate of the rock and the incident energy change in a logarithmic *** similar incident energies,unloading results in a higher strain rate in pre-stressed *** to the experimental analysis,unloading does not affect the failure mode,but reduces the dynamic strength of pre-stressed *** influence of confining pressure unloading on the shear strength parameters(cohesion and friction angle)is *** the same external energy impact compression,prestressed rock subjected to unloading is more likely to be ***,the effect of unloading on the rock mechanical characteristics should be considered in deep rock project excavation design.

关键词： deep rock excavation unloading unloading confining pressure three-dimensional high stress strengthweakening effect impact disturbance

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