DOI: 10.18419/darus-3106
title: In situ performed fracturing experiment of a limestone sample using an X-ray transparent triaxial cell: micro-XRCT data sets and measurement data

description: This dataset contains in situ recorded micro X-ray Computed Tomography (micro-XRCT) scan data sets (reconstructed and projection images) of a marine limestone sample under different triaxial loading conditions. The loading conditions were applied to establish the initial conditions to run the so-called Natural Hydraulic Fracture (NHF) protocol proposed by French et al. (2012). Since the fracturing attempt was not successful, in a subsequent step, a Confined Compressive Strength (CCS) test was carried out successfully under a confining pressure of 2 MPa. The experiment was performed in an in-house developed and self-built low X-ray absorbing triaxial cell for 1/4 inch diameter core samples with external axial load application. The cell is designed for confining pressures up to 42.5 MPa. The experiment was conducted in the context of an application example to demonstrate the possibilities of the setup presented in Ruf & Steeb (2023). For the test, a prepared cylindrical marine limestone sample with a length of 15 mm and a diameter of 6.37 mm was used, having a mass of 1.0 g in dry state and a sufficiently low permeability (k = 1.9073x10&lt;sup&gt;-18&lt;/sup&gt; m&lt;sup&gt;2&lt;/sup&gt;) for the procedure. As pore fluid, 73% glycerin solution (density 1.19 g/ml, viscosity of 0.03 Pa s) was employed.&lt;br&gt;
&lt;br&gt;
Before running the NHF protocol, the initial boundary conditions, an axial load &#963&lt;sub&gt;a&lt;/sub&gt; = 36 MPa, a confining pressure &#963&lt;sub&gt;r&lt;/sub&gt; = 38 MPa, and a fully saturated state with a uniform pore pressure distribution p = 35 MPa have to be applied. From the different sample states before and after running the NHF protocol and CCS test, the following scans were performed:
&lt;br&gt;
 &lt;ol&gt;
 &lt;li&gt;scan "1o" & "1d" of unloaded, dry state&lt;/li&gt;
 &lt;li&gt;scan "2d" of loaded (&#963&lt;sub&gt;a&lt;/sub&gt; = 36 MPa, &#963&lt;sub&gt;r&lt;/sub&gt; = 38 MPa), dry state&lt;/li&gt;
 &lt;li&gt;scan "3d" of loaded (&#963&lt;sub&gt;a&lt;/sub&gt; = 36 MPa, &#963&lt;sub&gt;r&lt;/sub&gt; = 38 MPa), saturated (p = 35 MPa) state&lt;/li&gt;
 &lt;li&gt;scan "4d" & "4o" of loaded (&#963&lt;sub&gt;a&lt;/sub&gt; = 2 MPa, &#963&lt;sub&gt;r&lt;/sub&gt; = 38 MPa), saturated (p = 0 MPa) state after NHF protocol&lt;/li&gt;
 &lt;li&gt;scan "5d" & "5o" of unloaded state after NHF protocol&lt;/li&gt;
 &lt;li&gt;scan "6d" & "6o" of confined shear failure in the post-failure regime (&#963&lt;sub&gt;r&lt;/sub&gt; = 2 MPa), partially saturated from NHF test (drained conditions)&lt;/li&gt;
&lt;/ol&gt;
It is distinguished between overview scans "*o" showing the entire specimen and detail scans "*d" showing the center region of the sample.

The files "*._projections.tar.gz" obtain the projection image data sets, and the files "*._reconstructed.tar.gz" are the corresponding reconstructed ones. The files "*._reconstructed_cropped.tar.gz" are cropped to the rock sample area to reduce the data size. The files "utm_data.csv," "pumpA_data.csv," and "pumpB_data.csv" include the corresponding measurement data over time of the Universal Testing Machine UTM (axial load control), pump A (pore fluid pressure control), and pump B (confining fluid pressure control).