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dynamic tensile strength and failure mechanisms of thermally treated sandstone under dry and water-saturated conditions

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Transactions of Nonferrous Metals Society of China 2020年第8期30卷 2217-2238页

作者： Pin WANG Tu-bing YIN Bi-wei HU School of Resources and Safety Engineering Central South UniversityChangsha 410083China

To study the tensile strength and failure mechanisms of rock with hydro-thermal coupling damage under different loading rates,a series of static and dynamic splitting tests were conducted on thermally treated sandstone under dry and water-saturated *** results showed that high temperatures effectively weakened the tensile strength of sandstone specimens,and the P-wave velocity declined with increasing ***,thermal damage of rock increased gradually with increasing temperature,but obvious negative damage appeared at the temperature of 100℃.The water-saturated sandstone specimens had lower indirect tensile strength than the dry ones,which indicated that water-rock interaction led to secondary damage in heat-treated *** both dry and water-saturated conditions,the dynamic tensile strength of sandstone increased with the increase of strain *** water-saturated rock specimens showed stronger rate dependence than the dry ones,but the loading rate sensitivity of thermally treated rock decreased with increasing treatment *** the help of scanning electron microscopy technology,the thermal fractures of rock,caused by extreme temperature,were ***-physical mechanisms of sandstone under different loading rate conditions after heat treatment were further discussed.

关键词： sandstone dynamic tensile strength hydro-thermal coupling damage loading rate dependence failure mechanism

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dynamic Uniaxial tensile strength Tests on Limestone

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Journal of Geological Resource and Engineering 2020年第5期8卷 172-183页

作者： Ajay Kumar Jha BioID GmbH Nürnberg 90489Germany

dynamic properties of limestone govern the rock fragmentation *** of rock under tension is more likely as compared to failure under compression under static or dynamic loading *** the application of explosives creates dynamic loading and is a dynamic event,the determination of dynamic modulus values is technically more appropriate than the static *** rock fragmentation would significantly improve by investigating the dynamic uniaxial tensile strength as specific fracture energy,stress intensity factor,fracture toughness of any detonating blast hole depend heavily on dynamic rock property and not on static rock *** of the limestone projects globally are still accustomed with using static tensile strength to understand the rock *** present papers deal with determination of dynamic uniaxial tensile property using split Hopkinson pressure bar(SHPB)*** nano second high speed camera with laser captures the crack surface opening velocity during dynamic *** was observed during data analysis that dynamic tensile strength of limestone increases by 1.2-2.3 times of the static *** may be concluded by the study that determination of dynamic tensile strength is paramount for understanding the rock fragmentation.

关键词： Rock fragmentation SHPB dynamic tensile strength

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Correction of dynamic Brazilian disc tensile strength of rocks under preloading conditions considering the overload phenomenon and invoking the Griffith criterion

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第8期15卷 1986-1996页

作者： Kaiwen Xia Yuchao Yu Bangbiao Wu Wei Yao State Key Laboratory of Hydraulic Engineering Simulation and Safety School of Civil EngineeringTianjin UniversityTianjin300072China Department of Civil and Mineral Engineering University of TorontoTorontoM5S 1A4Canada

dynamic tensile failure is a common phenomenon in deep rock practices,and thus accurately evaluating the dynamic tensile responses of rocks under triaxial pressures is of great *** Brazilian disc(BD)test is the suggested method by the International Society for Rock Mechanics and Rock Engineering(ISRM)for measuring both the static and dynamic tensile strengths of rock-like ***,due to the overload phenomenon and the complex preloading conditions,the dynamic tensile strengths of rocks measured by the BD tests tend to be *** address this issue,the dynamic BD tensile strength(BTS)of Fangshan marble(FM)under different preloading conditions were measured through a triaxial split Hopkinson pressure bar(SHPB).The fracture onset in BD specimen was captured through a strain gage around the disc *** discrepancy between the traditional tensile strength(TTS,determined by the peak load P_(f) of the BD specimen)and the nominal tensile strength(NTS,obtained from the load P_(i) when the diametral fracture commences in the tested BD specimen)was applied to quantitatively evaluating the overload *** Griffith criterion was used to rectify the calculation of the tensile stress at the disc center under triaxial stress *** results demonstrate that the overload ratio(s)increases with the loading rate(σ)and decreases with the hydrostatic pressure(σ_(s)).The TTS corrected by the Griffith criterion is independent of theσ_(s)due to the overload phenomenon,while the NTS corrected by the Griffith criterion is sensitive to both the andσ.Therefore,it is essential to modify the tensile stress in dynamic confined BD tests using both the overload correction and the Griffith criterion rectification to obtain the accurate dynamic BTS of rocks.

关键词： dynamic brazilian disc test Overload phenomenon dynamic tensile strength Hydrostatic pressure Griffith criterion

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dynamic rock tensile strengths of Laurentian granite: Experimental observation and micromechanical model

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第1期9卷 116-124页

作者： Kaiwen Xia Wei Yao Bangbiao Wu Department of Civil Engineering University of Toronto State Key Laboratory of Hydraulic Engineering Simulation and Safety School of Civil Engineering Tianjin University

tensile strength is an important material property for rocks. In applications where rocks are subjected to dynamic loads, the dynamic tensile strength is the controlling parameter. Similar to the study of static tensile strength, there are various methods proposed to measure the dynamic tensile strength of *** we examine dynamic tensile strength values of Laurentian granite(LG) measured from three methods: dynamic direct tension, dynamic Brazilian disc(BD) test, and dynamic semi-circular bending(SCB). We found that the dynamic tensile strength from direct tension has the lowest value, and the dynamic SCB gives the highest strength at a given loading rate. Because the dynamic direct tension measures the intrinsic rock tensile strength, it is thus necessary to reconcile the differences in strength values between the direct tension and the other two methods. We attribute the difference between the dynamic BD results and the direct tension results to the overload and internal friction in BD tests. The difference between the dynamic SCB results and the direct tension results can be understood by invoking the non-local failure theory. It is shown that, after appropriate corrections, the dynamic tensile strengths from the two other tests can be reduced to those from direct tension.

关键词： dynamic tensile strength Brazilian disc(BD) test Semi-circular bending(SCB) Direct tension Split Hopkinson bar

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Quantification of dynamic tensile parameters of rocks using a modified Kolsky tension bar apparatus

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Journal of Rock Mechanics and Geotechnical Engineering 2010年第2期2卷 162-168页

作者： S. Huang Rong Chen K. W. Xia University of Toronto Toronto M5S IA4 Canada National University of Defense Technology Changsha 410073 China

For brittle materials, the tensile strength plays an important role in mechanical analyses and engineering applications. Although quasi-static direct and dynamic indirect tensile strength testing methods have already been developed for rocks, the dynamic direct pull test is still necessary to accurately determine the tensile strength of rocks. In this paper, a Kolsky tension bar system is developed for measuring the dynamic direct tensile strength of rocks. A dumbbell-shaped sample is adopted and attached to the bars using epoxy glue. The pulse shaping technique is utilized to eliminate the inertial effect of samples during test. The single pulse loading technique is developed for the effective microstructure analyses of tested samples. Two absorption devices are successfully utilized to reduce the reflection of waves in the incident bar and transmitted bar, respectively. Laurentian granite （LG） is tested to demonstrate the feasibility of the proposed method. The tensile strength of LG increases with the loading rate. Furthermore, the nominal surface energy of LG is measured, which also increases with the loading rate.

关键词： Kolsky tension bar system dynamic tensile strength single pulse loading

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A Model of Physico-Mechanical Characterization of Sangaredi Bauxites and Related Rocks Taking into Account Their Litho-Genetic Type

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Journal of Minerals and Materials Characterization and Engineering 2024年第6期12卷 281-298页

作者： Oumar Keita Mory Diane Department of Hydrology University of Nzrkor Nzrkor Guinea Guinea Bauxite Company Kamsar Guinea

The Sangarédi bauxite deposit in the Republic of Guinea contains several bauxite types depending on their litho-genetics. For rational and sustainable exploitation, determining the physical and mechanical properties of these different bauxite types is essential for mining companies. This paper presents a model for the physico-mechanical characterization of Sangarédi bauxites according to their litho-genetic type. Eight pits were drilled, and samples were collected from different layers at different depth intervals for each bauxite type. Physical and mechanical characterization tests were then carried out on 27 samples to determine the following parameters: water of absorption (%), compressive strength (kgf/cm2) and dynamic tensile strength (kgf/cm2). The effect of depth of sampling on these physico-mechanical parameters was evaluated. An average value of the parameters was made for each bauxite type. The results showed that the physico-mechanical characteristics of bauxites depend on the depth of sample collection, and the average value of the parameters constitutes the representative values of the bauxite type. Finally, a comparative study of the average value of the physico-mechanical parameters of the different bauxite types was carried out.

关键词： Bauxites Litho-Genetics Physico-Mechanical Compressive strength dynamic tensile strength

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