David Tressel Griggs (1911-1974)
Professor D.T. Griggs designed and built the solid medium deformation machine that was named after him. (Picture was copied from the Foreword by I.A. Getting and W.W. Rubey in: Flow and Fracture of Rocks, edited by H.C.Heard et al., Geophysical Monograph 16, Americal geophysical Union, Washington D.C., 1972.)

Biography: https://nap.nationalacademies.org/read/4547/chapter/6#112

Fig. A.1 Schematic drawing of the Tullis-modified Griggs machine. (Drawing slightly
modified after Tullis, T.E. & Tullis, J., Experimental rock deformation techniques. In:
Mineral and Rock Deformation: Laboratory Studies, edited by B.E. Hobbs and H.C. Heard,
Geophysical Monograph Series, Volume 36, 297-324, AGU, Washington, 1986).

Fig. A.2 Photograph of the Tullis-modified Griggs machine in the HPT-lab at Utrecht
University. Note that it is built into an isolation box (coated with aluminium foil) in
which the temperature is controlled to ~32 degC. This serves to eliminate daily variations
in temperature which strongly affect the stress measurement.

Fig. A3 Schematic drawing of part of the Griggs apparatus showing the hydraullic
ram, pressure vessel and sample loading system. For scale, pressure vessel diameter is ~20 cm.

Fig. A4 Schematic diagram of sample assembly. Upper and lower thermocouples
denoted UTC and LTC. Assembly is 1 inch in diameter.

Fig. A5 Photographs of (a) loose components of the sample assembly, and (b) all
components assembled before mounting the assembly into the vessel. Note that except for
the inner and outer upper WC-pistons, and the lower WC-piston, all pieces are non re-
usable and must be machined for each experiment.