README

---- General Information ----

DATA TITLE:  The effect of a liquid phase on force distribution during deformation in a granular system dataset

PROJECT TITLE:  The effect of a liquid phase on force distribution during deformation in a granular system

DATA ABSTRACT:  Two-phase systems, where one phase is solid and the other fluid, are widespread in nature. Examples include reservoir rocks holding vital fluids like water or petroleum, slurries of partially crystallized magmas, the semi-brittle middle crust, and fluids migrating along faults filled with fault gouge. Previous studies of two-phase systems have shown that the weak phase plays an important role on deformation localization and dynamics. Here, we house data from experiments investigating the influence of a weak phase on force distribution in a granular media during simple shear. We use photoelastic polyurethane discs as the granular or strong phase and a linear-viscous silicone as the weak phase. The photoelastic property of the discs allows for direct observation and measurement of force magnitude and distribution. We compare the two-phase experiments to granular experiments without silicone. The addition and percentage of the weak phase has a strong impact on the force distribution and the overall force chain orientations.

AUTHORS:  Christopher R. Ladd, Jacqueline E. Reber


---- File Directory ----

---- File List ----

A. [Granular_Photos] - [Folder contains images from a granular experiment. Pictures are taken from above the apparatus, looking directly down on the materials.]
a. [0.000_N.jpg] - [For this folder the number (here 0.000) corresponds to the strain at which the picture was taken. N represents images that are not cross polarized.]
b. [0.000_X.jpg] - [This file corresponds to a photo taken at a strain of 0.000 and is cross polarized - denoted by X.]
B. [85%_Photos] - [This folder houses images from a two-phase experiment with an 85% packing density of the granular discs. Pictures are taken from above the apparatus, looking directly down on the materials.]
a. [2p19_0.000_N.jpg] - [The 2p means this photo is from a two-phase experiment, 19 is the experiment number. The rest of the numbers and letters match the same notation as the above folder.]
b. [2p19_0.000_X.jpg] - [All notations explained above.]
C. [75%_Photos] - [This folder houses images from a two-phase experiment with a 75% packing density of the granular discs. Pictures are taken from above the apparatus, looking directly down on the materials.]
a. Similar notations as described in previous folders
D. [65%_Photos] - [This folder houses images from a two-phase experiment with a 65% packing density of the granular discs. Pictures are taken from above the apparatus, looking directly down on the materials.]
a. Notations match previous folders
E. [Apparatus_Force_Data] - [Folder contains force data from each experiment in separate comma separated value sheets.]
a. [Granular_Experiment.csv] - [Force data from a granular experiment in a comma separated spreadsheet. The first column corresponds to the time at which the force and displacement were measured. The second column is the measured force in Newtons. The third column is the displacement of the table in centimeters.]
b. [Granular_Experiment.lvm] - [Force data from a granular experiment, in logical value format. The data is the same as that in the corresponding .csv file.]
c. [85_TP.csv] - [Force data in a comma separated spreadsheet from a two-phase experiment with 85% packing density. Column notation and order is the same as described for the granular experiment.]
d. [85_TP.lvm] - [Force data in a logical value format from a two-phase experiment with 85% packing density. The data is the same as that in the corresponding .csv file.]
e. [75_TP.csv] - [Force data in a comma separated spreadsheet from a two-phase experiment with 75% packing density. Column notation and order is the same as described for the granular experiment.]
f. [75_TP.lvm] - [Force data in a logical value format from a two-phase experiment with 75% packing density. The data is the same as that in the corresponding .csv file.]
g. [65_TP.csv] - [Force data in a comma separated spreadsheet from a two-phase experiment with 65% packing density. Column notation and order is the same as described for the granular experiment.]
h. [65_TP.lvm] - [Force data in a logical value format from a two-phase experiment with 65% packing density. The data is the same as that in the corresponding .csv file.]


---- Methods and Materials ----

---- Data Collection Methods ----

Experiments are performed using a linear simple shear table consisting of two plates (Figure 2). One plate is held fixed while the other plate moves at a constant velocity (0.337 mm/s), creating a discrete shear plane where the two plates meet. The experimental material is confined by an aluminum frame to ensure the conservation of volume. During deformation we record the overall force with a Chatillon DFS II piezoelectric force gauge and measure the displacement by using a Celesco cable transducer. Both are measured at a rate of 10 Hz (Daniels and Hayman, 2008; Hayman et al., 2011; Reber et al., 2014). The maximum strain we impose is 0.25 and the maximum force recorded is 180 Newtons.

For model materials we use 6.25-mm-thick circular polyurethane discs of two diameters (9 and 11 millimeters) as well as silicone (Dow Corning PDMS-DC SGM36) with a viscosity of 8 x 104 Pa s that behaves as a linear-viscous fluid at the imposed strain rate (3.74 x 10-4 s-1 ) (Weijermars, 1986).

---- Data Processing Methods ----

All data here is raw data.

---- Software ----

* Force calculations were performed using the PEGS program published and outlined in Daniels et al. 2017

Daniels, K., Kollmer, J., and Puckett, J., 2017, Photoelastic force measurements in granular materials: Review of Scientific Instruments, v. 88, no. 5; https://doi.org/10.1063/1.4983049


* Angle calculations of force chains were made by employing FracPaQ, a code developed by Healy et al. (2017)

Healy, D., Rizzo, R., Cornwell, D., Farrell, N., Watkins, H., Timms, N., Gomez-Rivas, E., and Smith, M., 2017, FracPaQ: A MATLAB (TM) toolbox for the quantification of fracture patterns: Journal of Structural Geology, v. 95, p. 1-16; http://dx.doi.org/10.1016/j.jsg.2016.12.003

---- Licensing ----

      This work is licensed under a Creative Commons Attribution 4.0 International License.
See https://creativecommons.org/licenses/by/4.0/ for details