The role of particle breakage in the mechanics of a non-plastic silty sand (original) (raw)

Particle breakage and the critical state of sand

Soils and Foundations, 2014

Soil particles break during shear, with the intensity of the breakage depending on the stress level amongst other factors. Particle breakage has important implications for the soil's critical state, which is an input to the majority of advanced constitutive models. This work examines a micromechanical framework where particle breakage shifts down the critical state locus in void ratio versus mean effective stress space without changing its slope. The framework assumes that detectable particle breakage in sand does not occur unless the contraction potential of the material, solely by the sliding and the rolling of the particles, is exhausted and a soil specific stress level threshold is surpassed. A series of triaxial compression tests conducted to investigate the validity of the framework is presented. It is shown that particle breakage is a factor, working alongside dilatancy, imposing additional compressibility on the soil.

Laboratory Investigation on Particle Breakage Characteristics of Calcareous Sands

Advances in Civil Engineering, 2021

Many studies have demonstrated the fragility of calcareous sands even under small stresses. This bears an adverse influence on their engineering properties. A series of laboratory tests were carried out on poor-graded calcareous sands to investigate the crushability mechanism. Einav’s relative breakage and fractal dimension were used as the particle breakage indices. The results show that the particles broke into smaller fragments at the low-stress level by attrition which was caused by friction and slip between particles. In contrast, particles broke in the form of crushing at the relatively higher stresses. The evolution of the particle size was reflected by the variation in Einav’s relative breakage and fractal dimension. As testing commenced, the breakage index rapidly increased. When the stress was increased to 400 kPa, the rate of increase in the breakage index was retarded. As the stress was further increased beyond 800 kPa, the rate of increase in the fractal index became mu...

Roles of Particle Breakage and Drainage in the Isotropic Compression of Sand to High Pressures

Journal of Geotechnical and Geoenvironmental Engineering, 2017

The roles of particle breakage and drainage conditions on the quasi-static compression response of sand were evaluated by comparing the results from drained and undrained isotropic compression tests on dry and saturated specimens up to a mean total stress of 160 MPa. For dry sand specimens, the compression curves from drained and undrained tests were similar due to the high compressibility of air. The isotropic compression curves of the dry sand specimens at mean stresses greater than 30 MPa reflect a transition toward void closure, reaching a minimum void ratio of 0.04 at 160 MPa. Dry sand specimens with different initial relative densities showed similar behavior during isotropic compression in drained conditions for mean stresses greater than approximately 30 MPa. As expected, saturated specimens tested under undrained conditions showed a much stiffer response than in drained conditions, with a bulk modulus greater than that of water. Increasing trends in particle breakage quantified using the breakage factors of Marsal and Hardin with increasing mean stress were observed for the dry sand specimens, but negligible particle breakage was noted for the saturated specimens tested in undrained conditions. To highlight the linkage between particle breakage and the transition to void closure at high mean effective stress, an empirical relationship was developed using Hardin's relative breakage index to match the experimentally-derived compression curves of dry sands under drained conditions.

The influence of particle breakage on stress-dilatancy relationship for granular soils

The influence of particle breakage on soil behaviour is important from theoretical and practical perspectives. Particle breakage changes the internal energy in two ways. First, internal energy is consumed for particle crushing and second, the internal energy changes because of additional volumetric strain caused by particle crushing. These two effects may be quantified by use of Frictional State Theory. The analysed drained triaxial compression tests of Toyoura sand, gravel and Dog's Bay sand at different stress level and stress path revealed that the effect of particle breakage is a function of soil gradation, strength of soil grains, stress level and stress path.

Particle breakage and its influence on soil behavior under undrained condition

Japanese Geotechnical Society Special Publication

This paper presents particle breakage and its influence on soil behavior under undrained shear condition. First the pre-crushed sand was produced by triaxial tests under 3MPa confining pressure on dense samples. It was revealed that particle breakage increased with increasing axial strain and particle breakage in shear band was found to be much more substantial than outside shear band. Thereafter the pre-crushed sand and original sand were used separately in new traixial tests under 0.2MPa and 3MPa confining pressures to investigate the influence of particle breakage on soil behavior under undrained condition. It was found that particle breakage deteriorated the stress-strain curves in reduction of peak strength of soil and resulted in more substantial development of excess Pore Water Pressure (PWP) with a higher residual excess PWP. Particle breakage resulted in more contractive behavior of soil in depression of dilatancy. The effective friction angle at peak strength and the deformation modulus at 0.002 axial strain were analyzed with respect to particle breakage. It was concluded that the particle breakage resulted in reduction of friction angle and deformation modulus.

Particle breakage during shearing of a carbonate sand

Géotechnique, 2004

A series of ring shear tests was conducted to investigate the development of particle breakage with shear strain for a carbonate sand. It was found that at very large displacements the soil reached a stable grading, but that the final grading was dependent on both the applied normal stress and the initial grading. The particle breakage caused a volumetric compression, which again ceased only when the stable grading had been attained, emphasising that critical states as observed at much smaller strains in triaxial tests are not rigorously defined. Despite the severe degradation of the soil particles the mobilised angle of shearing resistance was found not to change significantly.

Particle breakage in transitional soils

Oedometer tests were conducted to investigate whether particle breakage plays a significant role in the compression of transitional soils. Artificial mixtures of a carbonate sand and kaolin or a crushed quartz silt were both found to give measurable breakage within the sand fraction even at modest stresses, which is in contrast to the findings from tests by Nocilla et al. (2006) on clayey silts. It was found, therefore, that particle breakage may occur in transitional soils, although it is not a necessary aspect of their behaviour, as would be the case for clean sands. The amount of breakage was fairly similar for the two soils, so that it could also be concluded that the breakage was insensitive to the mineralogy or grading of the matrix material.

Creep of calcareous sand in Tunisia: effect of particle breakage at low stress level

2020

Aims/hypothesis One of the critical mechanisms determining creep in granular materials is the breakage of soil particles. This study aims at evaluating the time-dependent creep deformation of calcareous sand at low effective stress conditions. Methods K 0 creep tests were performed for both calcareous and silica sands at low stresses of 65 and 120 kPa, and the results of creep tests were compared with the results of constant rate of strain (CRS) tests at high stress levels up to 12 MPa. For a quantitative evaluation of the effect of the particle breakage on the creep deformation of calcareous sand, the relative breakage ( B_{r}Br)wasdeterminedbasedontheresultsofsieveanalyses.ResultsTheresultsdemonstratethatTunisiacalcareoussandexperiencessignificantparticlebreakageduringcreepandtheconsequentcreepdeformationatlowstresslevel.ThedeterminedB r ) was determined based on the results of sieve analyses. Results The results demonstrate that Tunisia calcareous sand experiences significant particle breakage during creep and the consequent creep deformation at low stress level. The determinedBr)wasdeterminedbasedontheresultsofsieveanalyses.ResultsTheresultsdemonstratethatTunisiacalcareoussandexperiencessignificantparticlebreakageduringcreepandtheconsequentcreepdeformationatlowstresslevel.ThedeterminedB_{r}$$ B r after creep at low stress level is comparable with that after the CRS test at high stress lev...