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The paper describes a new transparent granular soil that can be used for laboratory geotechnical modeling purposes. The transparent soil consists of fused quartz particles in combination with a mixture of two mineral oils as pore fluid. The solid particles and the matching liquid have the same refractive index. The soil has important advantages with respect to transparency, stability, health safety, and utility over glass and silica gel materials. The transparent soil is also inexpensive compared to silica gel-fluid materials that have been used in the past. Conventional laboratory shear box, triaxial compression, and permeability tests were carried out to demonstrate that the mechanical properties and hydraulic permeability of the transparent soil are typical of granular soils with angular particles.

This article describes a rate-dependent hyperbolic model that was developed to predict the tensile load-strain behavior of a polypropylene geogrid reinforcement material under monotonic and stepped constant rate-of-strain testing. A more general three-component model previously reported in the literature was also used in the current study but with some modifications to compute model parameters. Details of the trial and error procedure to select three-component model parameters, not previously reported in the literature, are explained. Both models gave similar good agreement between measured and predicted constant rate-of-strain tests. The accuracy of the three-component model to simulate stepped constant rate-of-strain tests was judged to be better, but for practical purposes, the simpler hyperbolic model was judged to be satisfactory. An advantage of the hyperbolic model is that the model parameters are easy to determine, only monotonic constant rate-of-strain tests are required, and numerical implementation is simple. However, the hyperbolic model is restricted to monotonic or stepped constant rate-of-strain load paths. An advantage of the more complicated three-component model is that it has been demonstrated in previous studies to be more general and thus can be used for other load paths and other polymeric reinforcement material types that do not have characteristic hyperbolic load-strain behavior. POLYM. ENG. SCI., 55:1617-1627 12. Influence of a, m, and _ e ir r values on predicted load-strain curves using three-component model.

The paper describes the results of a series of geogrid pullout tests that were carried out in a novel large pullout box with a transparent granular soil. The test apparatus and methodology allows the entire geogrid specimen to be visible through the bottom of the box. Specimen displacements are computed from image analysis of pictures taken through the transparent bottom of the pullout box during each test. The geogrid material was an integral punched and drawn biaxial polypropylene geogrid. A series of reference tests were carried out on geogrid specimens 2000 mm long and loaded at a front clamp displacement of 1 mm/min. The results of these tests have been reported in previous publication by the writers. In the current study, this earlier database of test results and interpretation of results is extended to include tests with specimens of different (shorter) length and loaded at other displacement rates. The tensile loads in the specimens are estimated using two different nonlinear rate-dependent load–strain models with parameters determined independently from in-air tests. The predicted loads are compared to measured loads recorded at the front and end of specimens trimmed to short lengths. In addition, the paper compares the load–displacement response of an unmodified geogrid specimen to that of a nominal identical specimen with the transverse members removed. The load–strain models are used to deduce the component of total tensile load in the geogrid carried by the transverse geogrid members. Finally, test results for nominal identical specimens tested in air and in soil show that there is no detectable influence of soil confinement on longitudinal tensile stiffness of the geogrid product used in this study.

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