SYMPOSIA PAPER Published: 01 January 1970

Development of Equipment for Determining Deformation Modulus and Stress by Means of Large Flatjacks


Development of equipment and proposed procedure for determining deformation modulus and in situ stress in rock masses is discussed. The procedure, which involves the use of large flatjacks, when perfected, will be considerably more economical than conventional, more elaborate methods such as the pressure chamber method, radial jacking, and the like. The flatjack procedure involves the cutting of a slot in the rock mass by means of a hydraulically powered 3-ft-diameter diamond saw, insertion of the large 3 by 6-ft flatjacks, and pressurizing of the jacks until cancellation is reached. The system has an advantage over conventional flatjack usage in that it permits pressurizing (testing) larger areas of rock, eliminates the need for grouting the flatjacks, and permits the determination of deformation modulus in addition to in situ stress.

Author Information

Deklotz, EJ
U. S. Army Corps of Engineers, Omaha, Neb.
Boisen, BP
U. S. Army Corps of Engineers, Omaha, Neb.
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Developed by Committee: D18
Pages: 117–125
DOI: 10.1520/STP29143S
ISBN-EB: 978-0-8031-4590-0
ISBN-13: 978-0-8031-0047-3