SEDL / STP / STP477-EB / STP29143S

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

Deklotz, EJ
Director and research engineer (1st Lt., U. S. Army CE), U. S. Army Corps of Engineers, Omaha, Neb.

Boisen, BP
Director and research engineer (1st Lt., U. S. Army CE), U. S. Army Corps of Engineers, Omaha, Neb.

Pages: 9    Published: Jan 1970

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Abstract

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.