This paper presents the prospect of 3D printing technology to generate artificial soil analogs with the goal of modeling the mechanical behavior of coarse-grained soils. 3D X-ray CT scans of natural angular and rounded sand particles have been used to generate angular and rounded particle analogs using the polyjet 3D printing technology. A comparison of the scanned natural sand particles and the 3D printed particles demonstrates the ability of 3D printing technology to reproduce the shape and size of the sand particles. The results of oedometer compression tests on the angular and rounded natural and 3D printed particles are used to demonstrate the effect of constituent material (i.e. quartz versus polymer) stiffness on the measured soil compressibility and investigate the normalization of the response using the Hertz contact theory. The results provided in this paper also include comparison of the small-strain moduli–mean effective stress relationship obtained for the natural and 3D printed soils. This paper illustrates the potential use of 3D printed analogs to model the mechanical behavior of coarse-grained soils and identifies future research needs for implementation of the proposed normalization scheme within the critical state soil mechanics framework.
more »
« less
Framework for Modeling Coarse-Grained Soil Behavior Using 3D Printed Soil Analogs
This paper presents the initial developments of a framework for modeling the compression behavior of coarse-grained soil using 3D printed particle analogs. This framework consists of a newly developed normalization scheme for 1-D compression response based on Hertz contact theory. The scheme normalizes the differences in stiffness of the natural and 3D printed particles’ constituent materials. To explore the capabilities of the proposed framework, this paper presents results of 1D compression tests on assemblies composed of spherical particles of constituent materials with Young’s moduli that span over two orders of magnitude (steel, glass and 3D printed resin). These initial results indicate that the stress-strain behavior of the assemblies can be normalized to be independent of constituent material stiffness. The presented framework can be useful for modeling the behavior of natural soil by testing representative 3D printed analogs, provided that the different aspects of the soils, such as particle shape, size, surface roughness and gradation are properly reproduced.
more »
« less
- Award ID(s):
- 1735732
- NSF-PAR ID:
- 10111474
- Date Published:
- Journal Name:
- IS Atlante from Micro to Macro
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
more » « less
Abstract Different particle properties, such as shape, size, surface roughness, and constituent material stiffness, affect the mechanical behavior of coarse-grained soils. Systematic investigation of the individual effects of these properties requires careful control over other properties, which is a pervasive challenge in investigations with natural soils. The rapid advance of 3D printing technology provides the ability to produce analog particles with independent control over particle size and shape. This study examines the triaxial compression behavior of specimens of 3D printed sand particles and compares it to that of natural sand specimens. Drained and undrained isotropically-consolidated triaxial compression tests were performed on specimens composed of angular and rounded 3D printed and natural sands. The test results indicate that the 3D printed sands exhibit stress-dilatancy behavior that follows well-established flow rules, the angular 3D printed sand mobilizes greater critical state friction angle than that of rounded 3D printed sand, and analogous drained and undrained stress paths can be followed by 3D printed and natural sands with similar initial void ratios if the cell pressure is scaled. The results suggest that some of the fundamental behaviors of soils can be captured with 3D printed soils, and that the interpretation of their mechanical response can be captured with the critical state soil mechanics framework. However, important differences in response arise from the 3D printing process and the smaller stiffness of the printed polymeric material.
Graphic abstract Artificial sand analogs were 3D printed from X-ray CT scans of sub-rounded and sub-angular natural sands. Triaxial compression tests were performed to characterize the strength and dilatancy behavior as well as critical staste parameters of the 3D printed sands and to compare it to that exhibited by the natural sands.
-
Inherent particle properties such as size, shape, gradation, surface roughness and mineralogy govern the mechanical behavior of coarse-grained soils. Obtaining a detailed understanding of soil behavior requires parametrization of the individual effects of these properties; however, isolating these effects is a challenge in experimental studies. The advances in 3D printing technology provide the ability to generate artificial sand- and gravel-sized particles with independent control over their size, shape, and gradation. This paper summarizes the strength and stiffness behavior of specimens composed of 3D printed (3DP) particles. Specifically, results of triaxial compression and bender element tests on 3DP sands are provided and compared to corresponding results on the natural sands. The 3DP sands show characteristic behaviors of natural sands, such as dependence on effective stress and stress-dilatancy. However, the 3DP soils are more compressible due to the smaller stiffness of the constituent polymeric material. The results show a decrease in critical state friction angle (φ′cs) and an increase in shear wave velocity (Vs) as the particle roundness and sphericity are increased, in agreement with published trends for natural soils. The agreement in trends highlights the potential for investigations using 3DP soils to extend the understanding of soil behavior.more » « less
-
This paper presents a novel laboratory experiment that can be incorporated into introductory soil mechanics courses to introduce students to the field of biogeotechnical engineering and the use of biostimulated microbially induced calcite precipitation (MICP). Applying MICP to granular soils results in an increase in peak strength and shear stiffness of the soil as a result of the precipitation of calcium carbonate on soil particle surfaces and at soil particle contacts. The authors developed protocols to treat small volumes of soil and to test the effectiveness of the treatment using a simple strength test based on ASTM D3967-16. In fall 2020, the experiment was piloted as a four-week, course-based research experience that can be conducted by students remotely or in a traditional laboratory environment. This paper provides an introduction to MICP and describes the protocols for conducting the experiment. The paper also suggests approaches for how the experiment can be incorporated into a traditional introductory soil mechanics course.more » « less
-
Amziane, S. ; Merta, I. ; Page, J. (Ed.)Natural earth-fiber building assemblies such as light straw clay, hempcrete, and clay-plastered straw bales incorporate vegetable by-products that are mixed with geological binders, traditionally used as an insulative infill in building construction. As a geo- and bio-based insulative infill method composed mostly of fiber, heat transfer coefficients are lower than mass materials, making it a compatible assembly that meets energy code requirements. Furthermore, due to their permeability, these materials exhibit high hygric capacity, providing regulated indoor temperatures and relative humidity levels, thus showing a promising future for socially just and healthier built environments. Despite these advantages, the use of earth-fiber building materials in digital construction is still underdeveloped. In the past few years, 3D-printed earth has gained an increasing interest, however, high contents of fibers in earth mixtures have yet to be fully tested and characterized. This paper presents an experimental workflow to characterize fiber-earth composites for 3D printed assemblies, using natural soils infused with natural fibers. The paper begins with a literature review of a range of fibers: straw, hemp, kenaf, sisal, and banana leaves, as well as naturally occurring biopolymer additives. The experimental setup includes manual extrudability and buildability tests, to identify optimal mix designs that are then tested for their printability and buckling using clay 3D printers. As a final deliverable, first pass geometric studies showcase the lightweight and structural possibilities of each material. The significance of this research lies in the development of a methodology for identifying novel mix design for digital fabrication, by increasing carbon storing vegetable fiber content within digital earth, and by creating a range of natural 3D printed assembly types: from mass-insulation walls to paper-thin lightweight partition assemblage.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Conference Paper:
- The DOI is not currently available.
