Wetting weakening of tertiary sandstones—microscopic mechanism

The micromechanism accounting for wetting weakening of tertiary sandstones was studied. It was found that intragranular fracture prevails for all dry sandstones. However, when the sandstone is wet, intergranular fracture occurs for Type B sandstones. Therefore, one sandstone from Type A sandstones, MS1, and another from Type B, TK, were selected to further investigate the nature of the matrix. It was found that (1) for both sandstones, the major mineral components of the matrix are illite and kaolinite except that the MS1 sandstone has more chlorite; (2) leaching of matrix induced an increase of porosity and consequently results in leaching softening; and (3) among the mineral composition, chlorite is easiest to be dissolved and leached out and induces a more significant increase of porosity, which, in turn, results in a more significant leaching softening.

[1]  Fu-Shu Jeng,et al.  Influence of petrographic parameters on geotechnical properties of tertiary sandstones from Taiwan , 2004 .

[2]  L. Dobereiner,et al.  Evaluating the strength and deformability of sandstones , 1991, Quarterly Journal of Engineering Geology.

[3]  F. G. Bell,et al.  Petrographic and engineering properties of sandstones from the Sneinton Formation, Nottinghamshire, England , 1998, Quarterly Journal of Engineering Geology.

[4]  J. Handin,et al.  Experimental Deformation of Sedimentary Rocks Under Confining Pressure: Tests at Room Temperature on Dry Samples , 1957 .

[5]  C. Oatley,et al.  The scanning electron microscope. , 1966, Science progress.

[6]  Y. Bernabé,et al.  The mechanical behaviour of synthetic sandstone with varying brittle cement content , 1998 .

[7]  Y. Bernabé,et al.  Experimental Observations of the Elastic and Inelastic Behaviour of Porous Sandstones , 1994 .

[8]  N. S. Rad,et al.  CEMENTED SANDS UNDER STATIC LOADING , 1981 .

[9]  M. Fahy,et al.  Estimating Strength of Sandstone Using Petrographic Thin-Section Data , 1979 .

[10]  T. Wong,et al.  Micromechanics of pressure-induced grain crushing in porous rocks , 1990 .

[11]  R. Ulusay,et al.  Prediction of engineering properties of a selected litharenite sandstone from its petrographic characteristics using correlation and multivariate statistical techniques , 1994 .

[12]  F. G. Bell,et al.  The petrographic and geomechanical properties of some sandstones from the Newspaper Member of the Natal Group near Durban, South Africa , 1999 .

[13]  W. R. Dearman,et al.  Influence of water on engineering properties of weathered rocks , 1986, Geological Society, London, Engineering Geology Special Publication.

[14]  Beatriz Menéndez,et al.  Micromechanics of brittle faulting and cataclastic flow in Berea sandstone , 1996 .

[15]  C. M. Sangha,et al.  Microfracturing of a sandstone in uniaxial compression : 7F, 2T, 15R. INT. J. ROCK MECH. MIN. SCI. V11, N3, MAR. 1974, P107–113 , 1974 .

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

[17]  A. Shakoor,et al.  Relationship Between Petrographic Characteristics, Engineering Index Properties, and Mechanical Properties of Selected Sandstones , 1991 .

[18]  Assessment of texture coefficient for different rock types and correlation with uniaxial compressive strength and rock weathering , 1996 .

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

[20]  A. Ersoy,et al.  Textural characterisation of rocks , 1995 .

[21]  Raymond Siever,et al.  Sand and sandstone , 1972 .

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

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

[24]  F. Kulhawy,et al.  A comparative evaluation of rock strength measures , 1984 .

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

[26]  E. T. Brown,et al.  Rock characterization testing and monitoring , 1981 .

[27]  Fu-Shu Jeng,et al.  Deformational characteristics of weak sandstone and impact to tunnel deformation , 2002 .

[28]  Abdul Shakoor,et al.  A geological approach toward developing a mudrock-durability classification system , 1994 .

[29]  M. Chigira,et al.  Chemical weathering mechanisms and their effects on engineering properties of soft sandstone and conglomerate cemented by zeolite in a mountainous area , 1991 .