**Experimental Geomechanics**

**Chapter 50**

**Comparison of Hydraulic and Conventional Tensile**

Tensile strength is paramount for reliable simulation of hydraulic fracturing experiments on all scales. Tensile strength values depend strongly on the test method. Three different labora‐ tory tests for tensile strength of rocks are compared. Test methods employed are the Brazilian disc test (BDT), modified tension test (MTT) and hydraulic fracturing experiments with hollow cylinders (MF = Mini Frac). Lithologies tested are a micritic limestone, a coarse-grained marble, a fine-grained Ruhrsandstone, a medium-grained rhyolite, a medium- /coarse-grained andesite and a medium grained sandstone. Test results reveal a relationship between the area under tensile stress at failure and the measured tensile strength. This relationship becomes visible when the area under tensile strength ranges over one order of magnitude from 450 to

. This observation becomes relevant when selecting the tensile strength values of

**Keywords:** hydraulic fracturing, Brazilian Disc test, Modified Tension Test, Acoustic Emission,

Tensile strength tests are widely applied in rock mechanics to obtain input parameters for planning of hydraulic fracturing on all scales. In literature only few experimental data sets are published dealing with samples size effects on tensile strength tests [1,2] or the comparison of different tensile tests in general [1,3]. Usually, results of laboratory tensile

and reproduction in any medium, provided the original work is properly cited.

© 2013 Molenda et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution,

**Strength Tests**

http://dx.doi.org/10.5772/56300

**Abstract**

4624 mm2

lithologies.

numerical simulation

**1. Introduction**

Michael Molenda, Ferdinand Stöckhert, Sebastian Brenne and Michael Alber

Additional information is available at the end of the chapter
