Abstract
The results obtained from the mechanical test of rock samples inevitably suffer dispersion owing to discrepancies between test specimens. In view of these deficiencies, the present study proposes a method based on the empirical equation of shear strength developed by Barton to determine the shear strength parameters of joint surfaces using a single test specimen. This approach is then applied to optimize the analysis of multiple specimens. An analysis of experimental results verifies that the shear strength parameters of joint surfaces obtained by the proposed method can more accurately reflect the shear mechanics of multiple specimens than conventional multiple sample analyses; meanwhile, the results are reasonable and reliable. More importantly, the optimized method ensures the shear strength parameters are no longer affected by the sequence of specimens employed during shear test. The optimized analysis method eliminates the effect of differences between specimens and the influence of subjective factors on test results and therefore provides more realistic evaluations of shear strength parameters.
Highlights
Introduction e overall and local deformations and stability of an engineering rock mass are often controlled by discontinuous joint surface. erefore, the reliability of rock mass deformation and stability analyses in engineering projects are directly affected by the accurate determination of the shear strength parameters of the joint surface. ese parameters are commonly obtained by shear test, which is a type of destructive test employed to evaluate the shear strength of individual rock joint specimens
Conventional Multiple-Specimen Method for Determining the Shear Strength Parameters. e shear strength parameters of joint surfaces are usually analyzed either by fitting the average values obtained under the various normal stresses or by fitting the individual values obtained under the normal stresses. e fitting results for methods 1 and 2 are given in Figures 4 and 5, respectively. e cohesion c1 and internal friction angle φ1 values for method 1 and those for method 2 (i.e., c2 and φ2) are obtained by fitting to the respective curves from methods 1 and 2, respectively
The results obtained from the shear test of multiple rock specimens inevitably su er discrete phenomenon owing to discrepancies between test specimens. e single-specimen method proposed in this paper based on the empirical equation for the shear strength of the joint surface which is proposed by Barton can determine the JRC of the joint surface, determine the shear strength of a joint surface under di erent normal stresses through a single shear test, and determine the shear strength parameters of the individual joint surface by conducting linear tting of the single experimental data point along with the calculated data points. is approach is applied to optimize the analysis of multiple specimens
Summary
Erefore, the reliability of rock mass deformation and stability analyses in engineering projects are directly affected by the accurate determination of the shear strength parameters of the joint surface. To obtain more generally applicable test results, multiple joint specimens are usually prepared to perform shear test under different normal stresses. To reduce the impact of specimen discrepancies on the results of shear test, repeated tests are usually performed using multiple specimens at each level of applied stress in studies. Erefore, the influence of specimen discrepancies on the shear strength parameters of the joint surface is an unavoidable problem when employing multiple joint specimens during mechanical test. Is approach is applied to optimize the analysis of multiple specimens. e proposed method seeks to eliminate the effect of specimen discrepancies and the effect of the test sequence on the results of shear test
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