Frost-Heaving Cracking Sensitivity of Single-Flaw Rock Mass Based on a Numerical Experimental Method

A novel numerical experimental method is developed herein to study frost-heaving cracking in fractured rock masses by reproducing the physical experimental frost-heaving process. The failure mode of a preexisting closed and water-saturated single-flaw in a rock mass during the frost-heaving process is affected by the inclination angle, flaw width, crack length, and cooling rate. Additionally, a regression model for predicting secondary crack formation and propagation is established by combining multiple stepwise regressions. Overall, the results indicate that preexisting flaw with various inclination angles, flaw lengths, and cooling rates mainly propagates along the flaw-coplanar direction. The secondary crack failure mode is most affected by the flaw width, and the length of the secondary crack increases with increasing inclination angle, flaw width, and flaw length, but decreases with increasing cooling rate. The contributions of the investigated factors to the secondary crack length follow the order: flaw width > inclination angle > cooling rate > flaw length. The results presented herein provide crucial theoretical guidance for engineering and construction projects in cold regions.

Generic Proximity Rules for Multiple Radially Oriented Planar Flaws: Technical Basis of Code Case N-877 Revision 1

In the case of planar flaws detected in pressure components, flaw characterization plays a major role in the flaw acceptability assessment. When the detected flaws are in close proximity, proximity rules given in the Fitness-for-Service (FFS) Codes require to combine the interacting flaws into a single flaw. However, the specific combination criteria of planar flaws vary across the FFS Codes. These criteria are often based on flaw depth and distance between flaws only. However, the level of interaction depends on more parameters such as the relative position of flaws, the flaw sizes and their aspect ratio. In this context, revised and improved proximity criteria have been developed to more precisely reflect the actual interaction between planar flaws. Thanks to numerous three-dimensional XFEM analyses, a wide range of configurations has been covered, including interaction between two surface flaws, interaction between two subsurface flaws and interaction between a surface flaw and a subsurface flaw. This paper explains in detail the steps followed to derive such generic proximity rules for radially oriented planar flaws.