Original scientific paper
https://doi.org/10.17794/rgn.2021.2.5
DEVELOPMENT OF A MODEL FOR THE ESTIMATION OF SHEAR STRENGTH OF DISCONTINUITY IN MASSIVE AND KARSTIFIED LIMESTONE
Ivana Dobrilović
orcid.org/0000-0001-8271-205X
; Našička 1, 10000 Zagreb
Petar Hrženjak
orcid.org/0000-0002-2664-0984
; University of Zagreb, Faculty of Mining, Geology and Petroleum Engineering, Pierottijeva 6, 10000 Zagreb
Dražen Navratil
; Croatian Geological Survey, Sachsova 2, 10000 Zagreb
Abstract
In this paper, the problem of estimating the shear strength of discontinuity is presented, which especially occurs in massive and karstified limestones, where discontinuity walls can be extremely rough and irregular, with or without filling material, and for which the current models have proven to be unsatisfactory. A characteristic example of such limestones is the deposit of dimension stone “Kanfanar”, located on the Istrian peninsula in Croatia. For the purpose of developing a model for estimating the shear strength of discontinuity, field research was conducted in which large samples of blocks with natural discontinuities were prepared, as well as samples of filling material in limited conditions, on which detailed laboratory tests of shear strength were performed. Special attention was paid to determining the joint roughness coefficient JRC, the actual contact area between the discontinuity walls, the basic or residual friction angle and the friction angle of the built-in filling material between the discontinuity surfaces. The development of the model for estimating the shear strength of discontinuity was based on Barton’s JRC-JCS empirical model, given the fact that it is one of the most commonly applied models in engineering practice. Based on the results of the tests, a modification of Barton’s JRC-JCS model was made, in such a way that the friction angle of the built-in filling material in the case of discontinuity with a filling was applied instead of the basic or residual friction angle. In addition, for the correct evaluation of the roughness of the discontinuity walls in massive and karstified limestones, it was found that it is necessary to increase the roughness coefficient to values larger than 20, which has been proposed as the maximum so far. Evaluation of the proposed model showed that it is satisfactorily accurate in estimating the shear strength of discontinuity with clay filling material of different states of consistency.
Keywords
Karst; discontinuity; shear strength; joint roughness coefficient; clay filling
Hrčak ID:
254159
URI
Publication date:
21.3.2021.
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