LABORATORY EVALUATION OF AN IN SITU TORSIONAL SHEAR DEVICE
RESULTS OF A LABORATORY EVALUATION OF A COMMERCIALLY AVAILABLE IN SITU TORSIONAL SHEAR TESTING DEVICE ARE PRESENTED. APPARATUS WAS CONSTRUCTED TO ACCOMMODATE THE TORSIONAL SHEAR DEVICE IN THE LABORATORY, AND SEVEN TESTS WERE MADE ON A REMOLDED CLAY SHALE MATERIAL. THE IMMEDIATE PURPOSE OF THE LABORATORY EVALUATION WAS TO DETERMINE IF THE TORSIONAL SHEAR DEVICE COULD BE USED TO DEFINE THE RESIDUAL STRENGTH PARAMETERS OF CLAY SEAMS OR ZONES OF WEAKNESS IN ROCK ON THE BASIS OF SHORT DURATION (ONE DAY) TESTS. IT IS THOUGHT THAT THE REMOLDED CLAY SHALE MATERIAL SIMULATES THE TYPE OF MATERIAL FOUND IN SITU IN SEAMS AND GOUGE ZONES. MOHR ENVELOPES DEFINED BY PLOTTING CALCULATED SHEAR STRENGTHS VERSUS TOTAL NORMAL STRESSES ARE LINEAR BUT EXHIBIT COHESION INTERCEPTS. COMPANION LABORATORY DIRECT SHEAR TESTS ON THE SAME MATERIAL EXHIBIT RESIDUAL FRICTION ANGLES COMPARABLE TO THOSE DEFINED WITH THE TORSIONAL SHEAR TESTS BUT DO NOT EXHIBIT COHESION INTERCEPTS. DUE TO THE DISPARITIES BETWEEN THE TWO TESTING METHODS -- RATE OF SHEAR, DRAINAGE CONDITIONS, UNCERTAINTY THAT RESIDUAL HAD ACTUALLY BEEN REACHED UNDER EACH NORMAL STRESS IN THE TORSIONAL SHEAR TESTS, TORSIONAL SHEAR SPECIMENS NOT ALLOWED TO FULLY CONSOLIDATE UNDER EACH NORMAL STRESS -- IT IS REASONABLE TO ASSUME THAT THE AGREEMENT IN FRICTION ANGLES BETWEEN THE TWO TEST METHODS MAY BE LARGELY FORTUITOUS. THE TORSIONAL SHEAR TESTS ON THIN SPECIMENS OF COMPARABLE THICKNESS (0.25-INCH) GIVE SHEAR STRENGTHS AND DEFINE MOHR ENVELOPES WHICH ARE CONSISTENT AND REPRODUCIBLE. THUS, THERE IS NO REASON TO BELIEVE THAT IF CONVENTIONAL SOIL MECHANICS PRACTICES WERE FOLLOWED MORE CLOSELY IN THE TORSIONAL SHEAR TESTS THAT ACTUAL RESIDUAL SHEAR STRENGTH PARAMETERS COULD NOT BE DETERMINED. THE CONVENTIONAL FORMULAE FOR CONVERTING APPLIED TORQUE TO SHEAR STRESS IN AN ANNULAR SPECIMEN OF AN IDEALIZED ELASTIC-PERFECTLY PLASTIC MATERIAL ARE DISCUSSED. APPLICABILITY OF THESE FORMULAE TO THE RESULTS OF TORSIONAL SHEAR TESTS ON CLAY-LIKE MATERIALS IS ASSESSED. SEVERAL EQUIPMENT CHANGES AND MODIFICATIONS AND IMPROVEMENTS IN THE FIELD TESTING PROCEDURES ARE RECOMMENDED WHICH SOULD IMPROVE THE VALIDITY OF THE FIELD TEST DATA. /AUTHOR/
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Supplemental Notes:
- 4 APP
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Corporate Authors:
Missouri River Division
Omaha, NE United States -
Authors:
- Butler, D K
- Bruhn, R W
- Publication Date: 1973-7
Media Info
- Features: Figures; References; Tables;
- Pagination: 90 p.
Subject/Index Terms
- TRT Terms: Equipment; Field tests; Formulas; Laboratory tests; Measuring instruments; Residual shear strength; Shear strength; Shear tests; Torsion tests
- Old TRIS Terms: Clay pockets
- Subject Areas: Geotechnology; Highways;
Filing Info
- Accession Number: 00230322
- Record Type: Publication
- Files: TRIS
- Created Date: Jun 26 1974 12:00AM