Abstract
This paper presents an investigation into the inter-particle bonding effects on the mechanical behaviors of structured sands using the distinct element method (DEM) incorporating measured inter-particle mechanical behaviors. The inter-particle mechanical behaviors are first studied by testing on idealized bonded granules under designed loading paths, which demonstrates a linear pre-failure force–displacement relationship and normal force-dependent shear strength of bonded particles. Then a modified contact model is proposed by employing different force–displacement laws for pre-failure and post-failure bonded particles, in which a failure criterion is introduced to describe the inter-particle debonding. The third part deals with the DEM numerical simulation of isotropic and biaxial compression tests to investigate the bonding effects on the mechanical behaviors of bonded sands, where the proposed model has been verified capable of capturing the main mechanical behaviors of bonded sands. In addition, the investigation into the microscopic responses quantitatively figures out the effects of inter-particle cementation on the mechanical behaviors and the loss of soil structure.
Highlights
Soil structure, including structural fabric and inter-particle bonding, is well known as the most important physical property of natural soils, including natural sands (Cuccovillo and Coop, 1997)
The sand fabric, is not considered in the bonded sand in this paper for the following reasons: (i) Numerical specimens consisting of disks are not sufficient to investigate the fabric of sands; (ii) This paper focuses only on the bonding effects on the mechanical behaviors of structured sands
This paper focuses on the effect of inter-particle bonding on the mechanical behaviors of bonded sands instead of the stress history occurred before the bonding, so the numerical specimens are all bonded after being consolidated under the stress of 12.5 kPa which represent a kind of soils formed at a shallow depth
Summary
Soil structure, including structural fabric and inter-particle bonding, is well known as the most important physical property of natural soils, including natural sands (Cuccovillo and Coop, 1997). Delenne et al carried out tests on epoxywelded doublets under the loading path, referred to as tension, compression, shear and moment to obtain the bond strength of bonded particles and numerically simulated the mechanical responses of bonded granular materials (Delenne et al, 2004). This paper aims to investigate the structure effects from the aspect of inter-particle bonding based on two-dimensional DEM simulations For this purpose, we carried out both simple and combined loading tests (i.e. tension or compression tests, shearing or/and rolling tests in which normal force is not zero) to obtain the mechanical properties of bonded particles which influence the strength and deformation of the bonded sands. The contact model was used to simulate the isotropic and biaxial compression tests to investigate the bonding effects on the mechanical behaviors of structured sands. The microscopic responses of structured sands under loading are discussed in this paper
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