Eduardo Suescun-Florez

Geotechnical Engineering in US Elementary Schools.

This paper reports on the results of several geotechnical engineering-related science activities conducted with elementary-school students. Activities presented include soil permeability, contact stress, soil stratigraphy, shallow and deep foundations, and erosion in rivers. The permeability activity employed the LEGO NXT platform for data acquisition, the soil profile and foundations activity employed natural and transparent soils as well as LEGO-based foundation models, and the erosion activity utilised a 3D printer to assist with construction of building models. The activities seek to enhance students’ academic achievement, excite them about geotechnical engineering, and motivate them to study science and math. Pre- and post-activity evaluations were conducted to assess both the suitability of the activities and the students’ learning. Initial results show that students gain a reasonable understanding of engineering principles. Moreover, the geotechnical engineering activities provided students an opportunity to apply their math skills and science knowledge.

Predicting the Uniaxial Compressive Response of Granular Media over a Wide Range of Strain Rates Using the Strain Energy Density Concept

An empirical non-linear method to predict stress–strain response of sand over a wide range of strain rates is presented. The method is inspired by the equivalence of the strain energy density (SED) of the material, at different strain rates. Silica based and calcium based sands were subjected to one-dimensional compression radially constrained tests to calibrate the methodology. Axial stress, axial strain and stiffness are also presented to assess the sensitivity of mechanical properties to strain rate. The observations show that sand under monotonic loading exhibits moderate strain rate dependency. This extent of rate varies with sand composition. There is good agreement between the strain rate behavior obtained from conventional tests and SED predictions derived from the proposed analysis.

A Nonviscous Water-Based Pore Fluid for Modeling With Transparent Soils

A new low viscosity transparent soil recipe was introduced in this note for the physical modeling of geotechnical problems. Pore fluid is a water-based solution made of sodium-thiosulfate treated sodium-iodide. The soil surrogate is crushed fused quartz. Physical and mechanical properties of the proposed materials were summarized, including refractive index (RI) and viscosity of the pore fluid, as well as hydraulic conductivity and shear strength of the produced transparent soil. The main advantages of the proposed transparent soil over previous recipes include lower viscosity, lower sensitivity to temperature variations, and the ability to recycle the materials for use in multiple tests.

Review of high strain rate testing of granular soils

This review provides an overview of testing techniques related to high strain rate (HSR) loading of granular media, in support of the increasing interest in civilian and military applications related to transient loading on sand. The intrinsic properties of granular soils are shown to be rate dependent. The framework for assessing rate dependent behavior of granular soils is presented. Techniques for applying HSR loading including uniaxial and triaxial compression configurations are discussed. Critical issues related to inertial and wave propagation effects as well as boundary effects are highlighted. In addition, options for test setup and measuring response are described both with respect to capabilities and drawbacks. The most relevant studies are summarized, but gaps and inconsistencies remain in the available literature.

Geotechnical Properties of BP-1 Lunar Regolith Simulant

AbstractUnderstanding the mechanical behavior of lunar regolith is of great importance for future missions to the Moon and other similar extraterrestrial environments. However, due to the scarcity of lunar regolith a number of simulants have been developed to facilitate experimental testing. This paper presents the geotechnical properties of an inexpensive lunar regolith simulant named Black Point 1 (BP-1). An experimental program including particle-size distribution, microscopy observations using scanning electron microscope (SEM) images, density measurements, compressibility, and shear strength was performed. Additionally, BP-1 was compared with regolith recovered from lunar missions and a number of its simulants. The physical properties of BP-1 were found to be similar to other existing simulants and to the natural lunar regolith.

Strain rate dependency of sand response under uniaxial monotonic loading

An experimental program was conducted to quantify the strain rate dependency of silica sand under different low to intermediate strain rates. Measurements of axial stress, axial strain and stiffness were explored to assess the sensitivity of mechanical properties to strain rate. Strain rates were applied on samples subjected to uniaxial compression stresses within a range of 0.01 to 100 %/sec. The tests help facilitate the incorporation of strain rate dependency of soil response in geotechnical modeling of soil-structure interaction problems. Available observations of the response of sand under monotonic loading suggest that sand may exhibit significant strain rate dependency.

Arrested Compression Tests on Two Types of Sand

Silica sand and quartz sand were subjected to uniaxial loading and unloading at rates of 0.1/s and 0.0001/s. The particle size distribution was measured, and found to be significantly altered when peak strains were 10 % or greater. The loading modulus for silica sand was bilinear, and suggestive of elastic-plastic behavior, where the plastic part is due to void closure. On unloading, the modulus is close to the loading “elastic” value. Coral sand is softer than silica sand on loading, and the modulus is almost constant and much less than for silica sand. Both types of sand are recovered with a higher density than can be obtained with the starting particle mix. This suggests particles have crushed and filled some of the voids. Indeed, reduction of mean particle size is verified from post-test analysis. Coral sand, which has the greater reduction in void content, also exhibits increased particle breakup.

Particle size reduction in granular materials during rapid penetration

Rapid penetration experiments using spherical projectiles at speeds up to 100 m/s were conducted in natural silica sand and in artificial sand comprised of crushed fused quartz. Material was recovered from the impact zone and subjected to size analysis and microscopic inspection. The fused quartz was much more susceptible to particle size reduction, particularly at lower velocities than natural sand. However, when the sand fractured, the particles were considerably smaller than those observed in fused quartz.