The Applicability of Correspondence Rule with Inclined Load

Excerpt

Cutting with a blunt cutter involves two processes: cutting of the rock on the cutting face and frictional contact on the wear flat (Detournay and Defourny 1992). Both the cutting and frictional contact are generally understood under ambient pressure, regarding the specific energy on the cutting face and the contact stress on the wear flat. The cutting process generally includes two failure modes: ductile and brittle failure (Liu et al. 2002; Richard et al. 2012; Huang et al. 2013; Zhou and Lin 2014), and the frictional contact process consists of three regimes: elastic, elastoplastic, and rigid plastic (Zhou and Detournay 2014, 2016). For deep drilling applications with both confining pressure and interstitial fluid pressure at the tool/rock interface, most work has been focused on the specific energy on the cutting face (Detournay and Atkinson 2000; Kaitkay and Lei 2005; Ledgerwood 2007), with limited work available on the contact stress at the wear flat–rock interface (Detournay et al. 2008). For the scenario with only confining pressure, a relevant solution is the bearing capacity of a rigid footing with an inclined load (Michalowski 2001), but the solution of limit contact stress is still lacking with both interstitial fluid pressure and confining pressure. Understanding the frictional contact under this condition is essential, as it will contribute to better understanding of several important aspects of drilling response, including the drilling efficiency, stick-slip vibrations (Richard et al. 2007), and borehole spiraling (Marck et al. 2014). …