Compaction, dilatancy, and failure in porous carbonate rocks

Abstract

[1] The analysis of dilatant and compactant failure in many sedimentary and geotechnical settings hinges upon a fundamental understanding of inelastic behavior and failure mode of porous carbonate rocks. In this study we acquire new mechanical data on the Indiana and Tavel limestones, which show that the phenomenology of dilatant and compactant failure in these carbonate rocks is similar to that of the more compact Solnhofen limestone as well as sandstones. Compressibility and porosity are positively correlated. Brittle strength decreases with increasing porosity and the critical stresses for the onset of pore collapse under hydrostatic and nonhydrostatic loadings also decrease with increasing porosity. Previously, two micromechanical models were used to interpret mechanical behavior of Solnhofen limestone: viewing cataclasis and crystal plasticity as two end-members of inelastic deformation mechanisms, the wing crack and plastic pore collapse models were applied to brittle and ductile failure, respectively. Synthesizing published data for carbonate rocks with porosities between 3% and 45%, we investigate to what extent the same micromechanisms may be active at higher porosity. Application of the plastic pore collapse model indicated that crystal plasticity cannot be the only deformation mechanism. To arrive at a more realistic interpretation of shear-enhanced compaction in porous carbonate rocks cataclastic processes must be taken into account. We infer that mechanical twinning dominates in the more porous limestones and chalk, while dislocation slip is activated in the more compact limestones.

Mechanical Behavior of Cement Paste and Alterations of Hydrates under High-Pressure Triaxial Testing

“…At P c = 30 and 100 MPa, peak stress was shortly followed by an abrupt stress drop of a few tens of MPa that occurred at ε a = 1.8 to 2.5%, marking the end of ductile deformation, while a similar stress drop occurred significantly later at ε a = 3.5% under P c = 400 MPa, meaning greater ductility. The general increasing trend of ductility (in terms of SS curves) with P c is well known for rocks (Heard 1960;Edmond and Paterson 1972;Vajdova et al 2004;Paterson and Wong 2005) and HCs (Sfer et al 2002), however, correspondence to the fracture pattern differs as we discuss in detail below. We begin by comparison with the brittle-ductile transition of rocks, where certain systematic trends have been established after many years of research (Paterson and Wong, 2005).…”

“…These differences are likely to be attributable to material properties such as chemical composition, porosity (Vajdova et al 2004), or grain size, but possible effects from sample preparation and test method, such as aspect ratio and friction at the ends of the samples (Paterson 2005), cannot be ruled out at this point. In the future, with HCP, the effects of the aspect ratio and friction at the sample ends need to be examined.…”

Sequential growth of deformation bands in carbonate grainstones in the hangingwall of an active growth fault: Implications for deformation mechanisms in different tectonic regimes

“…Deformation bands in porous carbonate rocks, on the other hand, were first reported from laboratory experiments (Baud et al, 2000;Vajdova et al, 2004). Natural examples of these bands have been reported since the mid-2000s Micarelli et al, 2006;Tondi et al, 2006).…”

“…Tondi et al, 2006), (ii) strain hardening behaviour (Baud et al, 2009;Cilona et al, 2012;Ji et al, 2015), (iii) scaling properties , (iv) magnitude of displacement (e.g. Tondi et al, 2006;Antonellini et al, 2008), (v) failure modes (Vajdova et al, 2004;Baxevanis et al, 2006;Cilona et al, 2014), (vi) sensitivity to changes in porosity and the shape and size of grains Cilona et al, 2014), and (vii) porosity-permeability reduction (Rath et al, 2011;Antonellini et al, 2014a;Tondi et al, 2016). However, there are other aspects of carbonate deformation bands that make them different from deformation bands in porous sandstones.…”

“…Aydin, 1978;Aydin andJohnson, 1978, 1983;Fossen and Hesthammer, 1997), and has later been supplemented by studies focusing on emulating deformation band growth through laboratory experiments (e.g. Mair et al, 2000;Mair et al, 2002;Vajdova et al, 2004) as well as in numerical models (e.g. Antonellini and Pollard, 1995;Klimczak et al, 2011;Chemenda et al, 2012).…”