Journal Article

Influence of Block form on the Shear Behaviour of Soft Soil–Rock Mixtures by 3D Block Modelling Approaches

Zhang, Han, Deng, Huafeng, Boldini, Daniela, Wang, Lehua, Liu, Chang

2022

Overview

The influence of block forms on the shear behaviour of soil–rock mixtures with soft blocks (soft S–RMs) can be efficiently investigated by the discrete element method (DEM) on the basis of accurate 3D models accounting for the block breakage. This paper proposes a novel modelling approach, based on the spherical harmonics series, for the generation of 3D block geometries with different forms but same convexity and angularity. An already existing non-overlapping modelling approach was improved, characterized by a reduced computational cost, for the set-up of 3D block DEM models accounting for the block breakage. A number of soft S–RM DEM samples, subjected to numerical direct shear tests, were generated to analyze the influence of block forms and volumetric block proportion VBP on the mesoscopic and macroscopic behaviours. The results showed that the breakage degree is maximum for the spheroidal blocks, followed by the oblate, prolate and blade ones, due to the combined influence of the block frictional sliding and rotation. The shear strength of soft S–RMs is mainly controlled by the block interlocking and breakage, being maximum in the case of spheroidal block samples when the applied normal stress is low and in the case of prolate and blade ones for a high normal stress. It was found that a nonlinear Mohr–Coulomb criterion can provide a good description of the shear strength envelope of soft S–RMs. Soft S–RMs are characterized by a higher friction angle if composed by spheroidal and prolate blocks when the VBP is 40%, due to their elevated block interlocking, and in the case of prolate and blade blocks when the VBP is 60% at the higher normal stress, due to their lower block breakage degree.HighlightsA spherical harmonics based approach was proposed for generating 3D block geometries with different forms but same convexity and angularity.A non-overlapping approach was improved for set up of 3D block DEM models considering the possible block breakage with a reduced computational cost.The influence of block form on the meso- and macro- shear behaviours of soft S-RM were analyzed.Block form has great influence of the shear behaviour of soft S-RMs, especially when the value of VBP is high.

• Publisher: Springer Nature B.V
• Subject: Behavior / Computational efficiency / Computer applications / Computing costs / Convexity / Discrete element method / Locking / Mixtures / Modelling / Mohr-Coulomb theory / Rocks / Shear strength / Shear tests / Soil / Soil mixtures / Soils / Spherical harmonics / Three dimensional models