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Title: Acoustic emissions during deformation of intact and jointed welded tuff

Monitoring of acoustic emissions (AE) has been widely used as a means of detecting failure in intact rock. For intact rock the technique is simple, because an increasing rate of AE is usually a sign of impending failure. However, most large rock masses contain numerous joints and the behavior of the joints controls the properties of the rock mass. In particular, the failure mode often becomes stable or unstable slip (stick-slip) on a joint at stresses well below those required for failure of the intact rock. As an aid to understanding and monitoring the behavior of jointed rock masses, we have done a series of experiments on intact and artificially jointed samples of Grouse Canyon tuff. The tuff was selected because it is under consideration as a disposal medium for nuclear wastes. The samples were instrumented to measure axial and transverse displacements and AE rates. Testing was done in a servo-controlled machine at axial displacement rates of 5 x 10{sup -5} cm/sec, and confining pressures ranging from 10 to 40 MPa. For the jointed samples four modes of slip were identified. First, stable sliding accompanied by a steady rate of AE. Second, stick-slip with a sharp drop in load, largemore » displacements but no premonitory AE or slip. Third, stick-slip, as in mode 2, but with premonitory AE and slip. Fourth, slow stick-slip where the load dropped and the displacements increased but the process was slow and culminated in stable sliding. Mode 4 exhibited premonitory AE and slip and after the event, a steady rate of AE during sliding. There seemed to be no way to predict which mode would occur at a given point in the test. In all cases where stable or unstable slip occurred there was a corresponding occurrence of AE. This indicates that slip is related to damage to the joint surfaces and adjacent material. Monitoring AE would be a useful method of detecting slip.« less
Authors:
;
Publication Date:
OSTI Identifier:
59471
Report Number(s):
SAND-82-1003
ON: DE82018346
DOE Contract Number:
AC04-76DP00789
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: Jul 1982
Research Org:
Sandia National Labs., Albuquerque, NM (United States)
Country of Publication:
United States
Language:
English
Subject:
05 NUCLEAR FUELS; 58 GEOSCIENCES; 36 MATERIALS SCIENCE; RADIOACTIVE WASTE DISPOSAL; GEOLOGIC DEPOSITS; SITE SELECTION; TUFF; FAILURES; ACOUSTIC EMISSION TESTING; YOUNG MODULUS; POISSON RATIO; POROSITY; DEFORMATION; DETECTION; JOINTS; SLIP; MECHANICAL TESTS; EXPERIMENTAL DATA; Yucca Mountain Project