A new practical method for prediction of geomechanical failure-time

Abstract

Predicting the failure-time of geo-hazards is an important rock mechanics problem. We first evaluated the validity of the INVerse-velocity (INV) method to predict failure-time of rock mass and landslides. This method utilizes rates of displacement or strain to predict the actual failure-time ( T f ), so the value of total displacement or strain before “failure” is not crucial. Second, we developed a new method for computing failure-time predictions based on the SLOpe (gradient) to predict T f , termed the SLO method. Finally, a simple conceptualised model representing “safe” and “unsafe” predictions was proposed. To validate these hypotheses, prediction of rock mass failure in the Asamushi and Vaiont landslides ( in situ studies) was conducted. Furthermore, laboratory conditions were incorporated into the research, which include predictions using circumferential strain and axial strain from uniaxial compression creep test on Shikotsu welded tuff (SWT), and predictions of failure-time for Inada granite under Brazilian creep tests. It was found that the SLO method is better than the INV method; SLO gave safe predictions in all the cases. In contrast, INV tends to give unsafe predictions (predicted failure-time T fp > T f ). Our findings reveal that predictions using circumferential strain are better than those made using axial strain for SWT, and notably, given failure with very short tertiary creep, the methods tend to show limited reliability. However, the SLO method could find extensive application in predicting failure-time of geo-hazards, for instance, roof wall failure in mines, etc.