Local and Global Volumetric Strain Comparison in Sand Specimens Subjected to Drained Cyclic and Monotonic Triaxial Compression Loading

Abstract

This article investigates the development of volumetric strain nonuniformities in sand specimens subjected to drained cyclic triaxial compression loading. The assessment is performed by comparing volumetric strain determinations using an external volume gauge and local axial and radial strain measurements mounted on the center of the specimen. The experimental investigation has been performed for both frictional and enlarged lubricated ends on sand specimens of different densities and fabricated using both moist tamping and dry deposition techniques. It will be shown that considerable discrepancies between the global and local volumetric determination arise even in specimens tested with enlarged lubricated ends, as a result of different volumetric tendencies (contraction or dilation) of the center and the boundaries of the specimens. These discrepancies are more pronounced for dense specimens cycled at high average stress ratios and amplitudes. The influence of three different assumptions employed to account for the specimen's deformed profile (namely the right cylinder, parabolic, and sinusoidal profile) on the local volumetric determinations will be also assessed. Some recommendations for the need for local volumetric measurements will be attempted.

Enhanced plasticity modelling of high-cyclic ratcheting and pore pressure accumulation in sands

“…Comparison between experimental results and model simulations are presented in Figure 5. The experimental results show that increasing cyclic stress amplitude leads to larger accumulated strain, corroborating findings of other experimental works (Escribano et al 2018). This is successfully predicted by the model, see Figure 5.…”

Modelling the cyclic ratcheting of sands through memory-enhanced bounding surface plasticity

“…Specifically, the simulation with η ave = 1.125 overestimates ε acc significantly when N > 1000: high-cyclic loading at large η ave jeopardises the effectiveness of the memory surface concept, as the model tends again towards the SANISAND04 limit. While nearfailure high-cyclic loading seems not too relevant to operational conditions in the field, some concerns could also be raised about the reliability of test measurements performed under such conditions, may be due to strain localisation phenomena (Escribano et al, 2018).…”

“…), to be calibrated based on rare high-cyclic laboratory tests -see e.g. Lekarp et al (2000); Suiker et al (2005); Wichtmann (2005); Wichtmann et al (2005); ; ; Escribano et al (2018). Most often, explicit highcyclic methods are used in combination with implicit calculation stages: the latter provide the space distribution of cyclic stress/strain increments via the time-domain simulation of one/two loading cycles; the former feed such information to empirical strain accumulation models and derive global high-cyclic deformations at increasing N (Niemunis et al, 2005;Andresen et al, 2010;Pasten et al, 2013).…”

3D FE-Informed Laboratory Soil Testing for the Design of Offshore Wind Turbine Monopiles

“…The experimental testing was conducted at the University of Bristol on Hostun RF (S28) sand, widely characterised in previous studies (i.e., Escribano et al [31]; Mandolini et al [11]). This sand is a standard European material for laboratory testing with a high siliceous content (SiO 2 ) of 98%, angular to subangular grains [32], mean grain size, D 50 = 0.38 mm, coefficient of uniformity, Cu = D 60 /D 10 = 1.9 and coefficient of gradation Cg = (D 30 ) 2 /(D 10 D 60 ) = 0.97.…”