Water-induced variations in mechanical properties of clay-bearing rocks

This study presents the results obtained from laboratory tests carried out on different types of clay-bearing rock collected from various parts of Turkey, to quantify the effects of water content on mechanical properties of the rocks, and to develop a method for estimating the rock strength and deformability at any water content based on physical properties. For this purpose, in addition to physical properties of the rock types collected, needle penetration resistance, uniaxial compressive strength, tensile strength and modulus of elasticity were determined on a number of specimens with different water contents. The results suggest that with increasing the water content the reductions in the uniaxial compressive strength, modulus of elasticity and tensile strength are up to 90%, 93% and 90%, respectively, from oven-dried to saturated conditions. Based on a series of empirical models developed and the comparisons between the experimentally determined mechanical properties and those predicted from the models, it is concluded that the suggested models seem to be very practical tools to estimate the mechanical properties of the clay-bearing rocks at any water content using the coefficients related to some physical properties of the rock material such as dry unit weight, water absorption by weight and porosity. In addition, needle penetration test is particularly suitable for such rocks to indirectly estimate their uniaxial compressive strength.

[1]  Candan Gokceoglu,et al.  Draft ISRM suggested method for determining block punch strength index (BPI) , 2001 .

[2]  A. Karayiğit,et al.  Mineral Matter and Trace Elements in Miocene Coals of the Tuncbilek-Domanic Basin, Kutahya, Turkey , 2003 .

[3]  E. T. Brown.  Rock characterization, testing & monitoring: ISRM suggested methods , 1981 .

[4]  A statistical investigation on mudrocks characteristics , 2001 .

[5]  Martin G. Culshaw,et al.  A geotechnical survey of some British Coal Measures mudstones, with particular emphasis on durability , 1997 .

[6]  Jean-Luc Froger,et al.  Neogene ignimbrites of the Nevsehir plateau (Central Turkey): stratigraphy, distribution and source constraints , 1994 .

[7]  Sung-Chi Hsu,et al.  Characterization of Eagle Ford Shale , 2002 .

[8]  E. V. Eeckhout,et al.  The mechanisms of strength reduction due to moisture in coal mine shales , 1976 .

[9]  Jan Środoń,et al.  Quantitative X-ray diffraction analysis of clay-bearing rocks from random preparations , 2001 .

[10]  D. Deere,et al.  Engineering classification and index properties for intact rock , 1966 .

[11]  A. K. Dube,et al.  Effect of humidity on Tensile Strength of Sandstone , 1972 .

[12]  Balázs Vásárhelyi,et al.  Influence of water content on the strength of rock , 2006 .

[13]  A. B. Hawkins,et al.  Sensitivity of sandstone strength and deformability to changes in moisture content , 1992, Quarterly Journal of Engineering Geology.

[14]  B. Vásárhelyi,et al.  Statistical Analysis of the Influence of Water Content on the Strength of the Miocene Limestone , 2005 .

[15]  A. B. Hawkins,et al.  Aspects of rock strength , 1998 .

[16]  M. S. Bruno,et al.  Empirical relations between compressive strength and porosity of siliciclastic rocks , 1993 .

[17]  B. Vásárhelyi,et al.  Some observations regarding the strength and deformability of sandstones in dry and saturated conditions , 2003 .

[18]  Paul M. Santi,et al.  Predicting the unconfined compressive strength of the Breathitt shale using slake durability, Shore hardness and rock structural properties , 1999 .

[19]  Gholam Reza Lashkaripour,et al.  Predicting mechanical properties of mudrock from index parameters , 2002 .

[21]  P. Grathwohl,et al.  Tracer diffusion coefficients in sedimentary rocks: correlation to porosity and hydraulic conductivity. , 2001, Journal of contaminant hydrology.

[22]  F. Bell.  The physical and mechanical properties of the fell sandstones, Northumberland, England , 1978 .

[23]  P. E. Potter,et al.  Sedimentology of Shale , 1980 .

[24]  D. Howarth,et al.  DEVELOPMENT OF AN INDEX TO QUANTIFY ROCK TEXTURE FOR QUALITATIVE ASSESSMENT OF INTACT ROCK PROPERTIES , 1986 .

[25]  L. Dobereiner,et al.  GEOTECHNICAL PROPERTIES OF WEAK SANDSTONES , 1986 .

[26]  Ali Ihsan Karayigit,et al.  Chemical Properties and Petrographic Composition of the Lacustrine Seyitomer Lignites (Miocene), Kutahya, Turkey , 2004 .