On the Measurement of the Tensile Strength of Soft Rocks

Coviello, Anthony; Lagioia, Rocco; Nova, Roberto

doi:10.1007/s00603-005-0054-7

Cited by 164 publications

(85 citation statements)

References 17 publications

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“…The tensile strength and tensile properties will vary with changes in the external conditions such as temperature, confining pressure, humidity, and structural plane (Cai & Kaiser, 2004;Coviello et al, 2005). The Brazilian split test is a conventional method for determining tensile strength.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study On The Effect Of Micro-Cracks On Brazilian Tensile Strength

Wang¹

2015

Archives of Mining Sciences

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For coal mine ground control issues, it is necessary to propose a failure criteria accounting for the transversely isotropic behaviors of rocks. Hence, it is very helpful to provide experimental data for the validation of the failure criteria. In this paper, the method for preparing transversely isotropic specimens and the scheme of the Brazilian tensile strength test are presented. Results obtained from Brazilian split tests under dry and water-saturated conditions reflect the effect of the development direction β of the structural plane, such as the bedding fissure, on the tensile strength, ultimate displacement, failure mode, and the whole splitting process. The results show that the tensile strength decreases linearly with increasing β. The softening coefficient of the tensile strength shows a sinusoidal function. The values of the slope and inflection point for the curve vary at the different stages of the Brazilian test. The failure mode of the rock specimen presented in this paper generally coincides with the standard Brazilian splitting failure mode. Based on the test results, the major influencing factors for the Brazilian splitting strength are analyzed and a mathematical model for solving the Brazilian splitting strength is proposed. The findings in this paper would greatly benefit the coal mine ground control studies when the surrounding rocks of interest show severe transversely isotropic behaviors.Keywords: Brazilian split test; Dry and water saturation; Bedding fissure; Strength coefficient; Coal mine ground control W związku z zagadnieniami ochrony powierzchni w kopalniach węgla, konieczne jest opracowanie odpowiednich kryteriów klasyfikacji uszkodzeń skał uwzględniających ich poprzeczną izotropowość. Pomocnym jest także dostarczenie danych eksperymentalnych niezbędnych do walidacji kryteriów uszkodzeń. W pracy tej zaproponowano metodę przygotowywania próbek wykazujących izotropowość poprzeczną, omówiono także sposób przeprowadzania testu na rozciąganie metodą brazylijską. Wyniki testu uzyskane na sucho oraz w warunkach nasycenia próbki wodą wskazują wpływ kierunku rozwoju β płaszczyzny strukturalnej (np. płaszczyzn spękań) na wytrzymałość próbki na rozciąganie, maksymalne przemieszczenia, rodzaj uszkodzenia oraz przebieg procesu pękania. Wyniki testu wskazują, że wytrzymałość na rozciąganie maleje liniowo wraz ze wzrostem wartości β. Współczynnik mięknienia próbki w trakcie próby wytrzymałościowej na rozciąganie ma przebieg krzywej sinusoidalnej. Wartości kąta nachylenia oraz punkt przegięcia krzywej różnią się dla poszczególnych etapów próby wytrzymałościowej. Tryb uszkodzeń próbek skalnych przedstawiony w artykule zasadniczo pozostaje w zgodzie z typowymi odkształceniami rejestrowanymi w trakcie testu metodą brazylijską. W oparciu o wyniki eksperymentu, przeanalizowano główne czynniki wpływające na wytrzymałość próbek na rozciąganie i zaproponowano odpowiedni model matematyczny do obliczania wytrzymałości. Wyniki przedstawione w artykule stanowią poważny przyczynek do badań stabilności gruntu...

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Section: Introductionmentioning

confidence: 99%

Experimental Study On The Effect Of Micro-Cracks On Brazilian Tensile Strength

Wang¹

2015

Archives of Mining Sciences

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“…Given the conjectures from theˆrst set of simulations and the observations made above-speciˆcally observation (2) which can be attributed to the trend among the test data points that at higher P2S values, there is a wider divergence between the positive half cycle data points and negative half cycle data points, as shown in Fig. 36, the SS curves referred to as Model 3 were introduced 4,5,6 .…”

Section: Simulations Considering the P2s Effectmentioning

confidence: 89%

“…The block samples were then packaged and shipped to the Geo- 1 The tensile strength was not measured. However, since the ratio between the tensile strength and compressive strength of soft rocks can be as high as 0.20 (Coviello et al, 2005), cyclic loading behaviour considering the tensile strength of soft rocks may have to be explored in future studies. 3 ; moisture content was around 31z; and the mean diameter D50 was from 0.20 mm to 0.25 mm (after thorough crushing).…”

Section: Triaxial Cyclic Loading Testsmentioning

confidence: 99%

The P2S Effect on the Accumulation of Residual Strains in Soft Rocks due to Irregular Cyclic Loading

Peckley

Uchimura

2009

Soils and Foundations

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“…Therefore, the use of jaws with quite small contacts like those of the line loading condition are not suggested to prevent reaching excessive compressive stress concentrations that can make invalid failures. In the use of 15° jaw, compressive stresses were not found to be enough high for causing the invalid compressive failure as the ratio of the maximum compressive stress was 4 times of the maximum tensile stress [25][26][27].…”

Section: Discussionmentioning

confidence: 99%

Determination of Cohesion values of Rock Materials using Double Shear Jaws

Komurlu¹,

Demir²

2018

Period. Polytech. Civil Eng.

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IntroductionAlthough shear strength of rock materials is an important parameter for many different rock engineering applications, there is still a necessity for development of a standard method and details for determination of shear strength of rock materials. The conventional direct shear strength (DSS) test method suggested by International Society for Rock Mechanics and Rock Engineering (ISRM) and standards like ASTM D5607 are not a proper way to test high strength rock materials because of possible failure of cement mortar instead of rock core specimens [1][2][3]. The cement moulding method to hold specimens is more suitable for testing rock joints rather than intact rock materials. As another topic, the conventional DSS test has additional problems of impracticality in specimen preparation process including two steps cement mortar casting as seen in Fig 1. In this study, a practical test method for determination of cohesion values of rock materials is investigated to assess whether accurate strength values can be measured using double shear jaw (DSJ) which is a basic apparatus to test numerous specimens instead of only one specimen as in cement moulding method of holding. Within this purpose, new steel jaws for testing cohesion of rock materials were designed and manufactured in this study.Need for waiting the curing time of several days for holding specimens in the casted mortar method should be stated as another disadvantage of the conventional DSS test. As an important issue which prevents to measure the strength value under pure shearing, significant bending/tension effect is induced as the rock specimen loaded in the soft cement mortar. Having the bending effect in the specimen causes to measure smaller strength values than that determined under pure shearing condition [4][5][6][7]. In this study, a new method of using DSJ was investigated for the aim of having ideal loading condition. For the conventional DSS equipment in rock mechanics laboratories, manual load application by using the hydraulic jack is an additional lacking to cause a personal effect on the strength results. On the other hand, double shear jaws (DSJs) let specimens to be loaded vertically with a constant rate which can be supplied by the load controlled compressive equipment.

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On the Measurement of the Tensile Strength of Soft Rocks

Cited by 164 publications

References 17 publications

Experimental Study On The Effect Of Micro-Cracks On Brazilian Tensile Strength

Experimental Study On The Effect Of Micro-Cracks On Brazilian Tensile Strength

The P2S Effect on the Accumulation of Residual Strains in Soft Rocks due to Irregular Cyclic Loading

Determination of Cohesion values of Rock Materials using Double Shear Jaws

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