Collection of data from the PhD Thesis "Thermo-mechanical loading of intact rock and discontinuities" by J Woodman. This collection of data includes raw logged .csv datafiles of uniaxial compression testing and triaxial compression testing on intact synthetic compositions, as well as intact and discontinuous specimens of Thornhill Rock and Midgley Grit at both ambient temperatures, and temperatures up to 100°C.

These data contain time series of stress, strain, confining pressure, pore pressure, pore volume, permeability and elastic wave velocities of samples of Purbeck Limestone deformed under hydrostatic and triaxial conditions at room temperature. All samples were saturated with decane as pore fluid.This dataset is used and fully described/interpreted in the paper: Brantut, N., M. Baker, L. N. Hansen and P. Baud, Microstructural control of physical properties during deformation of porous limestone, submitted to J. Geophys. Res.

This collection comprises two time-series of 3D in-situ synchrotron x-ray microtomography (μCT) volumes showing two Ailsa Craig micro-granite samples (ACfresh02 and ACHT01) undergoing triaxial deformation. These data were collected in-situ at the PSICHE beamline at the SOLEIL synchrotron, Gif-sur-Yvette, France in December 2016 (standard proposal 20160434) and are fully explained in Cartwright-Taylor A., Main, I.G., Butler, I.B., Fusseis, F., Flynn M. and King, A. (in press), Catastrophic failure: how and when? Insights from 4D in-situ x-ray micro-tomography, J. Geophys. Res. Solid Earth. Together, these two time-series show the influence of heterogeneity on the micro-crack network evolution. Ailsa Craig micro-granite is known for being virtually crack-free. One sample (ACfresh02) remained as-received from the quarry until it was deformed, while the second (ACHT01) was slowly heated to 600 degC and then slowly cooled prior to deformation in order to introduce material disorder in the form of a network of nano-scale thermal cracks. Thus these two samples represent two extreme end-members: (i) ACfresh02 with the lowest possible (to our knowledge) natural pre-existing crack density, and so is a relatively homogeneous sample and (ii) ACHT01 with a thermally-induced nano-crack network imprinted over the nominally crack-free microstructure, and therefore has increased heterogeneity relative to ACfresh02. Each 3D μCT volume shows the sub-region of each sample in which the majority of damage was located and has three parts. Part one is reconstructed 16-bit greyscale data. Part two is 8-bit binary data showing individual voids (pores and micro-cracks) in the dataset after segmentation. Part three is 32-bit data showing the local thickness of each void, as in Cartwright-Taylor et al. (in press) Figures 4 and 5. Each part is a zip file containing a sequence of 2D image files (.tif), sequentially numbered according to the depth (in pixels, parallel to the loading axis) at which it lies within the sample volume. File dimensions are in pixels (2D), with an edge length of 2.7 microns. Each zip file is labelled with the sample name, the relevant letter for each 3D volume as given in Cartwright-Taylor et al. (in press) Tables 3 and 4, part 1, 2 or 3 (depending whether the data are greyscale, binary or local thickness respectively), the differential stress (MPa) on the sample, and the associated ram pressure (bar) to link with individual file names. The following convention is used: sample_letter_part_differentialstress_rampressure_datatype. Also included are (i) two spreadsheets (.xlsx), one for each sample, containing processing parameters and the mechanical stress and strain at which each volume was scanned, and (ii) zip files containing .csv files containing measurement data for the labelled voids in each volume. N.B. void label numbers are not consistent between volumes so they can only be used to obtain global statistics, not to track individual voids.

Geomechanical strength data of mudstone samples collected from the Gunthorpe Member, of the Sidmouth Mudstone Formation of the Mercia Mudstone Group. The testing was completed at the British Geological Survey (BGS). All sample preparation, preservation and testing were completed to the specification outlined by the ISRM (ISRM, 1978b; ISRM, 1978a; Bieniawski and Bernede, 1979; ISRM, 1985 for determining the indirect tensile strength, triaxial strength, UCS and point load strength respectively) unless otherwise stated. Each test was comprised of three main stages: 1) A heating stage where the sample is heated to a set temperature loading scheme under pressure conditions of 1-1.4 MPa axial stress and 0.5 MPa confining pressure throughout the heating stage 2) A preloading stage, where the confining pressure is increased to 5 MPa which was held throughout the triaxial compression test. 3) Triaxial compression test, during the active deformation phase, the samples were axially loaded using a constant displacement rate of 0.0012 mm s-1. The data are separated into individual Microsoft Excel files, with each file representing a single test. Each file contains time, force, stress, displacement, and strain data. The data are separated into individual Excel files (.xlsx), with each file representing a single test. Each file contains time, force, stress, displacement, and strain data.

Geomechanical strength data of mudstone samples collected from the Grey Shale Member of the Whitby Mudstone Formation of the Lias Group. Testing includes cyclic thermo-mechanical loading completed at the British Geological Survey (BGS). All sample preparation, preservation and testing were completed to the specification outlined by the ISRM (ISRM, 1978b; ISRM, 1978a; Bieniawski and Bernede, 1979; ISRM, 1985 for determining the indirect tensile strength, triaxial strength, UCS and point load strength respectively) unless otherwise stated. Each test was comprised of three main stages: 1) A heating stage where the sample is heated to a set temperature loading scheme under pressure conditions of 1-1.4 MPa axial stress and 0.5 MPa confining pressure throughout the heating stage 2) A preloading stage, where the confining pressure is increased to 5 MPa which was held throughout the triaxial compression test. 3) Triaxial compression test, during the active deformation phase, the samples were axially loaded using a constant displacement rate of 0.0012 mm s-1. The data are separated into individual Microsoft Excel files, with each file representing a single test. Each file contains time, force, stress, displacement, and strain data.

This dataset contains raw (clean but not interpreted) triaxial compressive strength data of tests conductive at elevated pressure and temperature as outlined in "Vannucchi, P., Clarke, A., de Montserrat, A., Ougier-Simonin, A., Aldega, L., & Morgan, J. P. (2022). A strength inversion origin for non-volcanic tremor. Nature Communications, 13(1), 2311. https://doi.org/10.1038/s41467-022-29944-8". The data is provided in a .zip folder containing the files of 5 experiments that are accompanied by a README file for introduction. Files format is Microsoft Excel Worksheet (.xlsx) and data are tabulated. Each file contains the corresponding relevant sample’s details, and each column of data is clearly labelled, units included. For each experiment, time, axial force, axial displacement, axial stress, confining displacement, confining pressure, axial strain A and B, axial average strain, circumferential extensometer, circumferential strain, volumetric strain, internal temperature, and axial delta P were recorded. Triaxial testing was undertaken using the MTS 815 servo-controlled stiff frame inside a vessel capable of a confining pressure up to 140 MPa at the Rock Mechanics and Physics Laboratory, British Geological Survey, UK. The confining cell is fitted with external heater bands and utilizing utilizes cascade control from internal and external thermocouples (accurate to ± 0.5°C). An initial axial pre-load of 2.3 kN was applied, to ensure a stable contact and alignment of the platens. The confining pressure vessel was then closed and filled with mineral oil confining fluid. The axial pre-load was maintained whilst the confining pressure was applied at 2 MPa/min to 60 or 120 MPa; these values were chosen to approximately bracket the pressures at the up-dip limit of seismic nucleation, corresponding to 2 – 4 km depth (Arroyo et al., 2014). At this point, whilst held in axial force and confining pressure control, the rig was heated at 2°C/min to 60°C to approximate the average temperature conditions at the depth of the up-dip limit of seismic nucleation (Harris and Spinelli, 2010). The samples were then left for approximately 1 hour allowing thermal equilibrium to be reached throughout the confining fluid and the samples. Once stable, axial loading was initiated in constant axial strain rate control at a rate of 5.0 x 10-6 s-1 until macroscopic failure occurred or a significant amount of post peak-stress axial strain was recorded (between 2% and 5%). We note that one test was conducted at the higher temperature of T=120°C with a result within 2.5% of the strength at T=60°C (Table 1). As this is below the expected sample-to-sample variability, no further temperature studies were conducted. The axial load, axial load actuator displacement, axial stress (s1), differential stress (Q=s1 - s3), confining pressure Pc (= s2= s3), confining pressure actuator displacement, axial strain (eax), circumferential strain (ecirc) and temperature were monitored throughout at sampling frequencies of 1s and 0.5kN. File names are: YYYY-MM-DD_LabProjectNumber_SiteName-SampleNumber

The dataset contains triaxial compressive strength data of salt samples collected from the Northwich Halite Member at the Winsford Mine in Cheshire, UK. Each sample was subjected to varying strain or displacement-equivalent rates under conventional triaxial stress conditions to evaluate its mechanical response to different loading conditions. The experiments were conducted over two testing campaigns between July 2022 and August 2023, using a servo-controlled stiff load frame in the Rock Mechanics and Physics Laboratory at the British Geological Survey, Keyworth, UK. The dataset is organized into individual Microsoft Excel files, each corresponding to a single test and containing parameters such as time, force, stress, displacement, and strain. A summary file detailing sample characteristics and test conditions is also included.

Friction coefficient and frictional stability (rate & state parameter) data for triaxially compressed direct shear experiments on kaolinite-rich china clay and Mg-montmorillonite fault gouges (<2micron grain size). A total of 19 raw experimental datasets are presented as detailed in the index files: 13 on kaolinite-rich china clay, and 6 on cation-exchanged Mg-Montmorillonite. The raw data files, logged at either 1 or 2Hz, comprise confining pressures, upstream and downstream fluid pressures, force experienced by the direct shear assembly during triaxial compression, and absolute volumes of the confining pressure and fluid pressure reservoirs. Data is provided as measured by gauges in the pressure vessel in Volts, and also as calculated in MPa, kN and mm3. Also presented are the outputs of MATLAB models run to simulate the rate and state parameters k, a, b, dc and f0 for each experiment, with error data presented as 2sigma and standard error values. Parameters were determined using a non-linear least-squares fitting routine with the machine stiffness treated as a fitting parameter (c.f. Noda and Shimamoto, 2009). Data were fit by a single set of state variables (a, b, dc) with a linear detrend. Also presented are the outputs of Specific Thermogravimetric Analyses on kaolinite-rich china clay and Mg-montmorillonite.

This dataset contains experimental hydrostatic testing data with ultrasonic surveys and acoustic emission data as outlined in "Panza, E., Agosta, F., Rustichelli, A., Vinciguerra, S. C., Ougier-Simonin, A., Dobbs, M., & Prosser, G. (2019). Meso-to-microscale fracture porosity in tight limestones, results of an integrated field and laboratory study. Marine and Petroleum Geology, 103, 581-595, https://doi.org/10.1016/j.marpetgeo.2019.01.043". The data is provided in a .zip folder containing 11 files, with 10 files for each mechanical tests and 1 containing all the geophysical data recorded and calculated; accompanied by a README file for introduction. Files format is Microsoft Excel Worksheet (.xlsx) and data are tabulated. Each file contains the corresponding relevant sample’s details, and each column of data is clearly labelled, units included. For each experiment, mechanical dataset recorded time, axial force, axial displacement, axial stress, confining displacement, confining pressure, axial strains A and B, circumferential extensometer, and internal temperature. Physical dataset recorded sample’s dimensions, density, compressional (P) wave arrival time and shear (S1, S2) wave arrival times; details of calculated velocities and elastic parameters are also given. Ten right cylindrical samples of limestone from the Altamura Formation sampled at Pontrelli Quarry were tested in hydrostatic compression at a range of confining pressures (Pc = σ1=σ2=σ3) from 0 to 50, or 80 MPa, at 2 MPa/min. Samples were cored either horizontal (H) or vertical (V) that is respectively sub-parallel and sub-orthogonal to bedding; the orientation is indicated in the sample’s ID. Ultrasonic velocity measurements were performed at Pc = 0, 1, 2.5, 5, 10 MPa, and then at steps of 10 MPa up to the maximum Pc value. Each sample was tested oven dried (ca. 12 hours at 40 °C followed by cooling in a desiccator for 1 hour; all prior to the hydrostatic compression). All tests were conducted at room temperature. The experiments were conducted by Dr E. Panza, M. Dobbs and Dr A. Ougier-Simonin using the MTS815 Rock Testing System in triaxial configuration in the Rock Mechanics and Physics Laboratory of the British Geological Survey. All responsible for the collection and initial interpretation of the data.

Geomechanical strength data of mudstone samples collected from the Grey Shale Member, of the Whitby Mudstone Formation of the Lias Group. Testing includes Uniaxial Compressive Strength (UCS), Indirect Tensile Strength (ITS) and Triaxial strength testing completed at the University of Leeds (UoL) and Point Load testing completed at the British Geological Survey (BGS). All sample preparation, preservation and testing were completed to the specification outlined by the ISRM (2007) unless otherwise stated. For all Triaxial testing, each sample was deformed under standard triaxial stress conditions, where the primary principal stress corresponds to the axial stress and the intermediate and minimum principal stresses are equal to that of the confining pressure. The data are separated into individual Excel files (.xlsx), with each file representing a single test. Each file contains time, force, stress, displacement, and strain data.