Numerical Analysis of the Anisotropy and Scale Effects on the Strength Characteristics of Defected Rockmass

Abstract

Discontinuous defect in the rockmass is a key influential factor in controlling the strength behavior, and how to estimate the anisotropic strength and scale effect on the defected rockmass is the remaining challenging focus in engineering application. In the present study, intact tuff samples cored from the Xiabeishan tunnel engineering in situ are conducted by experiment tests (i.e., uniaxial compression test, triaxial compression test, and Brazilian tensile test) to obtain the corresponding mechanical parameters. Results from the numerical simulations using the particle flow code (PFC) by the flat-jointed model (FJM) are performed to match the macroparameters from experimental results. It is observed that numerical results have good agreement with the macroscopic mechanical parameters of intact samples including UCS, BTS, triaxial compression strength, and corresponding deformation parameters. Finally, a series of uniaxial and confining compression tests are conducted by using a synthetic rockmass (SRM) method which is coupled with the discrete element method (DEM) and discrete fracture network (DFN). Then, the anisotropy and scale effects on the strength characteristics of the defected rockmass are investigated. The results show that defects have a vital effect on the failure mode and strength behavior of the rockmass in the research region. The strength parameters are changed with the specimen size. The REV size of the considered defected rockmass is regarded as 5 × 10 m, and this size is also influenced by the confinement level. The anisotropy of macroscopic strength parameters is found in the considered defected rockmass, whose stress-strain curves and failure modes are also discussed.

Determination of representative elementary volume (REV) for jointed rock masses exhibiting scale-dependent behavior: A numerical investigation

“…It was found that the joint spacing predominantly controlled the extent of deformation above the excavation. Liu et al (2020) investigated the anisotropy and scale effects on the strength characteristics of the defected rock mass using a synthetic rock mass (SRM) method, which was coupled with the discrete element method (DEM) and discrete fracture network (DFN). The test results showed that defects in the rock mass played a vital role in failure mode and strength behavior.…”

Determination of representative elementary volume (REV) for jointed rock masses exhibiting scale-dependent behavior: a numerical investigation

“…It was found that the joint spacing predominantly controlled the extent of deformation above the excavation. Liu et al [28] investigated the anisotropy and scale effects on the strength characteristics of the defected rock mass using a synthetic rock mass (SRM) method, which was coupled with the discrete element method (DEM) and discrete fracture network (DFN). The test results showed that defects in the rock mass played a vital role in failure mode and strength behavior.…”

Influence of Parallel Joint Spacing and Rock Size on Rock Bulk Modulus

“…Ying et al [16] established a method based on volume rupture strength (P32) and a statistical test method to estimate rock mass REV. Wu et al [17] studied the effect of size on bulk modulus, while taking into account the effect of the model location, and reported that the REV size was 18 m. Liu et al [18] elucidated the size effect of the defective rock mass strength through uniaxial and confining pressure tests and obtained a REV size of 5 m × 10 m. Hu et al [19] obtained the relationship between the characteristic size of the rock elastic modulus and the PJS. Overall, although the bulk modulus has been extensively studied, only a few researchers investigated the relationship between the characteristic size of the bulk modulus (CSBM) and PJS and established a model of the CSBM and PJS.…”