Plasticity Modeling of the Effect of Sample Preparation Method on Sand Response

Abstract

Experimental evidence shows that different preparation methods produce sand samples with distinctly different stress-strain response. This paper explores and draws conclusions from the measured differences on the monotonic undrained triaxial response of Toyoura sand, prepared by different methods at the same values of void ratio and initial effective stresses. This is achieved by comparing data and simulations performed with a recently developed plasticity constitutive model, which accounts for the effect of inherent fabric anisotropy on the mechanical response. The inherent fabric anisotropy is represented by a second order symmetric fabric tensor, and its effect on the response at different loading directions is expressed by an appropriate dependence of certain constitutive ingredients on a joint isotropic invariant of the loading direction and the fabric tensor. Use of this constitutive scheme to simulate the aforementioned data on Toyoura sand exploits the fact that the preparation method affects both the dilatancy and the hardening response in a systematic manner. Under the premise that these effects are due to the differentinherent fabric created by the preparation method, it follows that the foregoing simulations do not require changes in constitutive equations or entirely different sets of model constants. On the contrary, only model constants related to this inherent fabric anisotropy scheme need readjustment, providing insight to how the sample preparation method affects the response and what can be done to model it.

Modeling of Geomaterials Behavior

“…The subloading surface concept (Hashiguchi and Ueno, 1977) and the bounding surface concept (Dafalias and Popov, 1975) are the two popular methods that do this. Although use of bounding surface plasticity is widely documented in the broader geomechanics literature, there have been few papers in Soils and Foundations that have used this concept (e.g., Papadimitriou et al, 2005). On the other hand, many papers have documented the use of the subloading surface concept.…”

Effect of Specimen Preparation Method on the Stress-Strain Behavior of Sand in Plane-Strain Compression Tests

“…Therefore, Yoshimine and Koike (2005) emphasized that establishing a link between different fabrics and structures obtained from various preparation methods in the laboratory and the in situ sedimentation and stress histories is very important from a practical point of view. Papadimitriou et al (2005) reported that such a link could be established by using a plasticity model with the inherent fabric anisotropy scheme, proposed by Dafalias et al (2004). However, more experimental data on the effects of specimen preparation method on the stress-strain behavior of sand under various stress and drainage conditions are needed to improve further modeling.…”

A non‐coaxial constitutive model for sand deformation under rotation of principal stress axes

“…M c and M e are the slopes of CSLs under compression and extension modes of triaxial. a can be obtained from the image analysis [34]. Alternatively, a can be calculated having CSLs under compression and Figure 11.…”

“…Prediction is obtained from a similar model which was disabled by setting f 1 = 0 (data from Miura et al [6]). extension modes of triaxial by using Equation (55) [34]. e A , and can be determined directly by fitting the test data for the CSLs under the compression and extension modes of triaxial in the e-p plane.…”

“…It is noted that the preparation methods standardized for sample preparation in laboratory produce their own characteristic fabrics. As a result, each preparation method has its own amount of a [34,35].…”