Testing Chamber Overview: The DSC and its operations are described in Santamarina and others (2012, 2015). Briefly, once the specimen is isolated in the Direct Shear Chamber (DSC, see Browse Graphic), the sediment is extruded from the plastic core liner using a plunger that will eventually serve as the specimen’s top endcap once the specimen is pushed all the way out of the liner and into the primary testing space. The plunger is then used to apply a vertical effective stress, returning the specimen to its in situ state of effective stress (approximately 2 MPa). Additional vertical effective stress can be applied to test the specimen response to the increasing effective stress that will occur in situ when the formation is depressurized to extract methane from gas hydrate. The consolidation data measured while applying the full range of vertical stresses are provided in a separate data release within this larger work (see "PCCT measurements of the consolidation characteristics, constrained modulus and compressional wave velocity for fine-grained sediment collected from Area C, Krishna-Godavari Basin during India's National Gas Hydrate Program, NGHP-02" in Jang and others, (2018)). For the shear strength testing, a core specimen in the DSC is held in a three-layer specimen chamber. The middle layer can be horizontally moved, shearing the middle third of the approximately 15 cm-tall specimen along the top and bottom of the middle layer. In this data release, the following parameters are reported as functions of the applied effective vertical stress: the horizontal and vertical strain, and the ratio of shear stress to effective vertical stress. The strains (unitless) are measured using Linear Voltage Displacement Transducers, and are reported here with an accuracy of 1e(-8). Stresses are calculated from load cell measurements, and are reported here with an accuracy of 5 kPa (kilopascal).
Jang, J., Dai, S., Yoneda, J., Waite, W.F., Collett T.S., and Kumar, P., 2018, Pressure core characterization tool measurements of compressibility, permeability, and shear strength of fine-grained sediment collected from Area C, Krishna-Godavari Basin, during India's National Gas Hydrate Program Expedition NGHP-02: U.S. Geological Survey data release, https://doi.org/10.5066/P91XJ7DP
Santamarina, J.C., Dai, S., Jang, J., and Terzariol, M., 2012, Pressure core characterization tools for hydrate-bearing sediments. Scientific Drilling, v. 14, p. 44-48.
Santamarina, J.C., Dai, S., Terzariol, M., Jang, J., Waite, W.F., Winters, W.J., Nagao, J., Yoneda, J., Konno, Y., Fujii, T., and Suzuki, K., 2015, Hydro-bio-geomechanical properties of hydrate-bearing sediments from Nankai Trough. Marine and Petroleum Geology, v. 66, p. 434-450.