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

Abstract

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:
Research Org.:
Sandia National Labs., Albuquerque, NM (United States)
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
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

Citation Formats

Holcomb, D.J., and Teufel, L.W. Acoustic emissions during deformation of intact and jointed welded tuff. United States: N. p., 1982. Web.
Holcomb, D.J., & Teufel, L.W. Acoustic emissions during deformation of intact and jointed welded tuff. United States.
Holcomb, D.J., and Teufel, L.W. 1982. "Acoustic emissions during deformation of intact and jointed welded tuff". United States. doi:.
@article{osti_59471,
title = {Acoustic emissions during deformation of intact and jointed welded tuff},
author = {Holcomb, D.J. and Teufel, L.W.},
abstractNote = {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, large 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.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1982,
month = 7
}

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  • The results of the experiments on simulated joints in welded tuff from the Grouse Canyon Member of the Belted Range Tuff warrant the following conclusions: (1) The coefficient of friction of the joints is independent of normal stress at a given sliding velocity. (2) The coefficient of friction increases with both increasing time of stationary contact and decreasing sliding velocity. (3) Time and velocity dependence of friction is due to an increase in the real area of contact on the sliding surface, caused by asperity creep. (4) Joints in water-saturated tuff show a greater time and velocity dependence of frictionmore » than those in dehydrated tuff. (5) The enhanced time and velocity dependence of friction with water saturation is a result of increased creep at asperity contacts, which is in turn due to a reduction in the surface indentation hardness by hydrolytic weakening and/or stress corrosion cracking.« less
  • As an aid to understanding and monitoring the behavior of jointed rock masses, we have done a series of experiments on samples of Grouse Canyon tuff containing sawcut joints. 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 servocontrolled machine at displacement rates of 2 x 10{sup -5} in/sec, and confining pressures ranging from 1500 to 6000 psi. Four modes of slip on joints were identified. First, stable sliding accompanied by a steady rate ofmore » AE. Second, stick-slip with a sharp drop in load, large displacements but no premonitory AE or slip. Third, stick-slip, as in mode 2, but with premonitory AE and slip. Fourth, stable 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. In all cases where premonitory slip or stable sliding occurred there was a corresponding occurrence of AE, indicating slip is related to damage to the joint surfaces and adjacent material. Monitoring AE would be a useful method of detecting slip and the extent of slip in modes 1, 3, and 4. Increasing slip rate leads to increasing AE rate. However, mode 2 stick-slip appears to be undetectable by this method.« less
  • We model a hydrothermal system as a discrete fracture/matrix system, using the integral finite difference code TOUGH and the best available data on the fracture and matrix properties of Topopah Spring densely welded tuff. These calculations will also be useful for the design of the underground facilities in the vicinity of the EBDT; e.g., in determining the volume of undisturbed rock required for each EBDT heater. After conceptualizing our model to be an infinitely long heater (either horizontal or vertical) which is orthogonally intersected by an infinite set of uniformly spaced fractures, we justify its applicability to both horizontal andmore » vertical heater emplacement. The calculations show that by the end of the full-power heating stage (t = 6 months), boiling in the rock results in complete desaturation out to a radius of r = 0.8 m from the heater axis, with partial desaturation occurring out to r = 1.8 m. Water vapor which does not leave the system via the borehole (to the drift) moves radially outward to the condensation zone lying 1.8--4.0 m from the heater axis. Gas pressures build up considerably within the matrix due to the low matrix permeability, but remain close to ambient within the fracture due to the high fracture permeability. At the end of the cooling stage (t = 24 months), the saturation in the matrix is below ambient for r < 3.0 m. Maximum temperature changes (above ambient) are 252.6{degree}C at the borehole wall, and 10.2{degree}C at a radial distance of 10.0 m from the heater axis. 32 refs., 17 figs., 2 tabs._« less
  • In order to assess in situ joint permeability near waste repositories, it has been proposed that instrumentation holes with axes parallel to the joint plane be drilled. However, the drill holes after the normal stress across the joint. The resultant stress concentration decreases the joint aperture and can significantly affect the joint permeability. Different intersections of the hold axis relative to the joint plane were examined utilizing a plane-strain, elastic analysis. It was found that a tangential joint intersection minimized the normal stress change. Stress along the joint increased by 10 to 15 percent and the permeability-aperture product decreased tomore » 65 to 70 percent of its original flow.« less
  • Acoustic emission was monitored during plastic deformation under dead-weight tensile loading of polycrystalline aluminum, brass, copper, and steel. The acoustic emission data, both threshold-type and frequency-analysis type, were correlated with yield strength, stored elastic energy, strain hardening parameters, loading histories, diffusion processes, slip band motion and mosaic cell size. Major results are presented under the headings discontinuous yielding (Portevin--Le Chatelier Effect), parabolic strain hardening, and frequency analysis. The principal experimental techniques are also summarized. (auth)