Studies in Rock Fracture

In July, 1970, a major effort was directed toward the measurement of the in situ state of strain stress at an outcrop of Mesa Verde sandstone Cretaceous, Site No. 1, on the N 45 degrees W plunging nose of the Rangely Anticline, western Colorado. With exception of a few of the photoelastic determinations, all measurements were made within a circle with a radius of about 2 m and within the same joint-bounded block. In addition, a specimen of the sandstone was studied in the laboratory by materials testing, optical, and X-ray diffraction techniques. Results for the strain-relief measurements are expressed as stresses by using a value of 50,000 bars 800,000 psi for Youngs Modulus. Compressive stresses are counted positive.