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Effects of pressure relief holes on coal burst:Insights from true-triaxial unloading tests

Journal of Rock Mechanics and Geotechnical Engineering 2024年第9期16卷 3378-3394页

作者： Fuqiang Ren murat karakus Giang Nguyen Thomas Bruning School of Civil Engineering University of Science and Technology LiaoningAnshan114051China Mining and Petroleum Engineering The University of AdelaideAdelaideSouth Australia5005Australia State Key Laboratory for Geomechanics&Deep Underground Engineering China University of Mining and TechnologyBeijing100083China School of Architecture and Civil Engineering The University of AdelaideSouth Australia5005Australia

Drilling pressure relief is one of the methods to reduce the risk of coal bursts in deep ***,the effect of the drill hole orientations has not been studied well enough to understand their impact on the burst failure *** this study,we investigated two designs of drill hole *** first design includes drill holes located on the upper free face of the rectangular samples and labelled as upper hole(UH)and centre hole(CH)e the long axes of the drill holes are aligned with minor principal stress,s3,*** second design includes drill holes at the top(TH)and the side(SH)of the rectangular samples in which the long axes of the drill holes are aligned with the maximum,s1,and intermediate principal stress,s2,directions,*** coal samples with the proposed drill hole orientations were subjected to the true-triaxial unloading coal burst *** results show that the drill holes reduce the risk of coal ***,we found that the intensity of coal burst was significantly reduced with the SH-type,followed by the *** also observed that the coal burst intensity is reduced better for the CH,UH,TH,and SH-type drilling ***,it was found that the orientations of drill holes have little influence on the failure mode(splitting).The acoustic emission(AE)activities for coal with drill holes noticeably decreased,especially for the UH and CH *** drill holes reduced the upper limit of the AE entropy(chaos of microcracks generation).However,regarding reducing the coal burst risk,the TH and SH are less effective than UH and CH.

关键词： Coal burst Triaxial unloading Drilling orientation Ejection characteristic Acoustic emission(AE)

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Effects of water content, water type and temperature on the rheological behaviour of slag-cement and fly ash-cement paste backfill

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International Journal of Mining Science and Technology 2020年第3期30卷 271-278页

作者： Yue Zhao Abbas Taheri murat karakus Zhongwei Chen An Deng School of Civil Environmental and Mining EngineeringThe University of AdelaideAdelaide 5005Australia School of Mechanical and Mining Engineering The University of QueenslandBrisbane 4072Australia

The pumping ability and placement performance of fresh cemented paste backfill(CPB) in underground mined cavities depend on its rheological properties. Hence, it is crucial to understand the rheology of fresh CPB slurry, which is related to CPB mixture design and the temperature underground. This paper presented an experimental study investigating the effects of binder type, content, water chemical properties and content, and temperature, on the rheological properties of CPB material prepared using the tailings of a copper mine in South Australia. Portland cement(PC), a newly released commercially manufactured cement called Minecem(MC) and fly ash(FA) were used as the binders added to the mine tailing materials. Various amounts of two different water types were added to the mixtures in the preparation of backfill material slurry. Six different temperatures ranging from 5 to 60 °C were to investigate the effect of temperature on CPB rheology. Overall, the increasing water content and decreasing temperature lead to lower yield stress. Based on the results obtained from the rheological properties of CPB slurry, it was found that at room temperature(25 °C), with regards to the unconfined compressive strength(UCS) performance, the replacement of 4% PC mixed CPB(28 days UCS 425 k Pa) to 3% MC mixed CPB(28 days UCS 519 k Pa), reduced the slurry yield stress from 210.7 to 178.5 Pa. The results also showed that the chemical composition of water affects the yield stress of CPB slurry and that MC mitigates the negative effect of mine-processed water(MW) and thus lead to improve the rheological properties of the slurry. However, the results suggested that the rheological properties of a mixture using MC is very sensitive to the water volume and temperature change. Therefore, using MC in backfill requires better quality control in slump mixing.

关键词： Cemented paste backfill Minecem Rheology Yield stress Fly ash Portland cement

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Effect of loading rate and time delay on the tangent modulus method(TMM)in coal and coal measured rocks

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International Journal of Coal Science & Technology 2022年第6期9卷 51-63页

作者： Zulfiqar Ali murat karakus Giang D.Nguyen Khalid Amrouch School of Civil Environmental and Mining EngineeringUniversity of AdelaideAdelaideSA 5000Australia Australian School of Petroleum and Energy University of AdelaideAdelaideSA 5000Australia Geology&Sustainable Mining Mohammed VI Polytechnic University43150 BenguerirMorocco

Non-destructive techniques of in-situ stress measurement from oriented cored rocks have great potential to be developed as a cost cost-effective and reliable alternative to the conventional overcoring and hydraulic fracturing *** tangent modulus method(TMM)is one such technique that can be applied to oriented cored rocks to measure in-situ *** the deformation rate analysis(DRA),the rock specimen is subjected to two cycles of uniaxial compression and the stress-tangent modulus curve for the two cycles is obtained from the stress-strain curve.A bending point in the tangent modulus curve of the first cycle is observed,separating it from the tangent modulus curve of the second *** point of separation between the two curves is assumed to be the previously applied maximum stress.A number of experiments were conducted on coal and coal measured rocks(sandstone and limestone)to understand the effect of loading conditions and the time *** specimens were preloaded,and cyclic compressions were applied under three different modes of loading,four different strain rates,and time delays of up to one *** bending point in the stress-tangent modulus curves occurred approximately at the applied pre-stress levels under all three loading modes,and no effect of loading rate was observed on the bending points in ***,a clear effect of time delay was observed on the TMM,contradicting the DRA *** could be due to the sensitivity of TMM and the range of its applicability,all of which need further investigation for the in-situ stress measurement.

关键词： Tangent modulus method TMM Deformation rate analysis DRA Time delay Strain rate

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Influence of deviatoric stress on rockburst occurrence:An experimental study

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International Journal of Mining Science and Technology 2018年第5期28卷 763-766页

作者： Thomas Bruning murat karakus Selahattin Akdag Giang D.Nguyen David Goodchild School of Civil Environmental and Mining EngineeringThe University of AdelaideAdelaide 5005Australia OZ Minerals 2 Hamra DriveAdelaide AirportSA5950Australia

As mining delves deeper into the crust, it is necessary to investigate the complex rock responses associated with higher stress gradients. Therefore, it is essential to better understand the mechanisms associated with the rockburst phenomenon. However, due to the large-scale and difficult monitoring of real mining excavations, laboratory scale tests must be utilised to determine the conditions conducive to burst. To this end, this research focuses on the implementation of a new rockburst testing apparatus to replicate the stress conditions of a rock mass excavation at the time of bursting. This apparatus allows the determination of rockburst stresses and a relationship between deviatoric stress and in-situ pressure/depth. Using this relationship it is then possible to estimate the standardised stress levels for a certain rock type which might lead to rockburst occurrence. Furthermore, it is demonstrated that with increasing in-situ pressure, the likelihood(measured as a lower differential stress) and the extent(indicated by the increasing range of deviatoric stress) of rockburst increases. These findings provide valuable information about the conditions necessary for bursting in deep mining.

关键词： Rockburst test Hollow cylinder Hard rock In-situ stress

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The collision experiment between rolling stones of different shapes and protective cushion in open-pit mines

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Journal of Mountain Science 2021年第5期18卷 1391-1403页

作者： ZHU Chun HE Man-chao karakus murat ZHANG Xiao-hu GUO Zhen School of Earth Sciences and Engineering Hohai UniversityNanjing 210098China Engineering Research Center of Development and Management for Low to Ultra-Low Permeability Oil&Gas Reservoirs in West China Ministry of EducationXi'an Shiyou UniversityXi'an 710021China State Key Laboratory for Geomechanics&Deep Underground Engineering Beijing 100083China School of Civil Environmental and Mining EngineeringThe University of AdelaideAdelaide SA 5005Australia College of Civil Engineering Tongji UniversityShanghai 200092China

Though gravel cushions are used worldwide in open-pit mines and railway slopes to control the impact of rolling stones,no universal technical standards have been put in place to guide engineers in their correct design,and few laboratory test results are available with which to characterize collisions between rolling stones and a gravel *** carried out a large number of experiments in which rolling stones made of the same material but differently shaped were dropped from various heights onto cushions with various particle sizes and *** investigated the characteristics of the resulting collisions,and the relationships between coefficients of restitution(CORs)of blocks with different shape and release height H,cushion thickness h and particle diameter d are obtained through linear fitting *** testing reveals the relative influence of block shape,release height,and the particle size and thickness of the cushion on the collision characteristics,which can assist engineers in designing a gravel cushion suitable to the distribution and weathering characteristics of rolling stones in a specific area.

关键词： Coefficient of restitution(COR) Collision characteristics Gravel cushion Rolling stone shape

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Evaluation of the propensity of strain burst in brittle granite based on post-peak energy analysis

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Underground Space 2021年第1期6卷 1-11页

作者： Selahattin Akdag murat karakus Giang D.Nguyen Abbas Taheri Thomas Bruning School of Civil Environmental and Mining EngineeringThe University of AdelaideAdelaideSAAustralia

The increasing demand for resources and depletion of near ground mineral resources caused deeper mining operations under highstress rock mass *** a result of this,strain burst,which is the sudden release of stored strain energy in the surrounding rock mass,has become more prevalent and created a considerable threat to workers and construction *** is,therefore,imperative to understand how strain burst mechanism and stored excess strain energy are affected due to the high confinement in deep underground *** this purpose,post-peak energy distributions for brittle rocks were investigated using a newly developed energy calculation method associated with acoustic emission(AE).A series of quasi-static uniaxial and triaxial compression tests controlled by the circumferential expansion were ***-back behaviour known as Class-II behaviour associated with energy evolution and the material response under self-sustaining failure were analysed on granites under a wide range of confining pressures(0–60 MPa).The experimental results underline that the energy evolution characteristics are strongly linked to *** elastic strain energy(dUE),energy consumed by dominating cohesion weakening(dUCW)and energy dissipated during mobilisation of frictional failure(dUFM)showed a rising trend as the confining pressure was *** intrinsic ejection velocity was proposed to express the propensity of strain burst that was purely determined by the excess strain energy released from Class II rock.

关键词： Strain burst Energy balance Class II failure mode Self-sustaining failure Triaxial compression test Circumferential strain control

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Thermal damage constitutive model for rock considering damage threshold and residual strength

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Journal of Central South University 2018年第10期25卷 2523-2536页

作者： XU Xiao-li karakus murat GAO Feng ZHANG Zhi-zhen School of Architecture and Civil Engineering Nantong University State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and Technology School of Civil Environmental and Mining Engineering the University of Adelaide

With the gradual depletion of mineral resources in the shallow part of the earth,resource exploitation continues to move deeper into the earth,it becomes a hot topic to simulate the whole process of rock strain softening,deformation and failure in deep environment,especially under high temperature and high *** the basis of Lemaitre’s strain-equivalent principle,combined with statistics and damage theory,a statistical constitutive model of rock thermal damage under triaxial compression condition is *** the same time,taking into account the existing damage model is difficult to reflect residual strength after rock failure,the residual strength is considered in this paper by introducing correction factor of damage variable,the model rationality is also verified by *** of results indicates that the damage evolution curve reflects the whole process of rock micro-cracks enclosure,initiation,expansion,penetration,and the formation of macro-cracks under coupled effect of temperature and confining *** thermal damage shows logistic growth function with the increase of *** the same strain condition,rock total damage decreases with the rise of confining *** studying the electron microscope images(SEM)of rock fracture,it is inferred that 35.40 MPa is the critical confining pressure of brittle to plastic transition for this *** model parameter F reflects the average strength of rock,and M reflects the morphological characteristics of rock stress–strain *** physical meanings of model parameters are clear and the model is suitable for complex stress states,which provides valuable references for the study of rock deformation and stability in deep engineering.

关键词： rock damage model temperature effect confining pressure damage threshold residual strength

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Note on Lower Triassic Gondolelloid Conodont Rediversifications with Emphasis on the Spathian Recovery

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Journal of Earth Science 2024年第4期35卷 1236-1242页

作者： Ali murat Kilic Department of Geological Engineering Faculty of EngineeringBalikesir UniversityBalikesir99100Turkey

Conodonts,as a biotic group,next to ammonoids,pollen and spores,crustaceans and vertebrates,provide proxy clues for environment and age assessments of the rocks in which they *** are widely used for Triassic marine ***,there are various discussions about their multielement taxonomy and evolutionary lineages(e.g.,generation,speciation).Although first studies reported that most Triassic conodont species were unimembrate,studies carried out in the following years maintained that all Triassic conodonts were *** statistical reconstructions of a number of Triassic apparatuses were attempted,the discovery of fused clusters and natural assemblages has subsequently demonstrated that Triassic conodonts are indeed multimembrate,and all of the elements exist together in the same *** present paper aims to clarify the evolutionary relationship and array of some Lower Triassic *** dagisi *** described.

关键词： Triassic Spathian conodont Columbitella Siberia environmental geology

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Effect of a cervical collar on optic nerve sheath diameter in trauma patients

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World Journal of Emergency Medicine 2024年第2期15卷 126-130页

作者： Mümin murat Yazici Ozcan Yavasi Department of Emergency Medicine Recep Tayyip Erdogan University Training and Research HospitalRize 53020Türkiye

BACKGROUND:As advocated in advanced trauma life support and prehospital trauma life support protocols,cervical immobilization is applied until cervical spine injury is *** study aimed to show the difference in optic nerve sheath diameter(ONSD)between patients with and without a cervical collar using computed tomography(CT).METHODS:This was a single-center,retrospective study examining trauma patients who presented to the emergency department between January 1,2021,and December 31,*** ONSD on brain CT of the trauma patients was measured and analyzed to determine whether there was a difference between the ONSD with and without the cervical ***:The study population consisted of 169 *** CT imaging of patients with(n=66)and without(n=103)cervical collars,the mean ONSD in the axial plane were 5.43±0.50 mm and 5.04±0.46 mm respectively for the right eye and 5.50±0.52 mm and 5.11±0.46 mm respectively for the left *** results revealed an association between the presence of a cervical collar and the mean ONSD,which was statistically significant(P<0.001)for both the right and left ***:A cervical collar may be associated with increased *** effect of this increase in the ONSD on clinical outcomes needs to be investigated,and the actual need for cervical collar in the emergency department should be evaluated on a case-by-case basis.

关键词： Optic nerve sheath diameter Computed tomography Trauma Emergency medicine

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Immunotherapy in gastric cancer with liver metastasis:Challenges and opportunities

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World Journal of Gastrointestinal Surgery 2024年第6期16卷 1513-1516页

作者： murat Bardakçi Yakup Ergun Department of Medical Oncology Diyarbakır Gazi Yasargil Training and Research HospitalDiyarbakir 021000KayapinarTürkiye Department of Medical Oncology Antalya City HospitalAntalya 07080Türkiye

In this editorial,we review the article by Liu et al published in the World Journal of Gastrointestinal Surgery investigating the efficacy and safety of immunotherapy in patients with gastric cancer(GC)and liver ***,the fifth most com-monly diagnosed malignancy worldwide,presents a significant challenge due to its multifactorial etiology and a grim prognosis for unresectable or recurrent *** advent of immune checkpoint inhibitors(ICIs)has revolutionized oncology;yet liver metastasis has been associated with reduced response rates,progression-free survival,and overall survival in various *** Che-ckMate-649 and KEYNOTE-859 trials demonstrated promising results with ICIs in advanced GC,particularly in patients with liver ***,a meta-analysis of liver metastatic solid tumors revealed worse outcomes with ICIs,high-lighting the need for further *** combined therapies,including ICIs with local treatments,show promise in improving outcomes,the nuanced landscape of ICIs in liver metastatic GC necessitates continued research for robust *** current contradictions in the literature underscore the impor-tance of cautious interpretation and the exploration of tailored approaches to enhance clinical efficacy in this challenging patient population.

关键词： Gastric cancer Liver metastasis Immunotherapy Immune checkpoint in-hibitors Transarterial chemoembolization Tumor microenvironment

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