Entropy Consistency-Based Adaptive Sampling Method for Determining the Scale Effect in the Joint Roughness Coefficient

The joint roughness coefficient (JRC) is one of the key parameters for evaluating the shear strength of rock joints. Because of the scale effect in the JRC, reliable JRC values are of great importance for most rock engineering projects. During the collection process of JRC samples, the redundancy or insufficiency of representative rock joint surface topography (RJST) information in serial length JRC samples is the essential reason that affects the reliability of the scale effect results. Therefore, this paper proposes an adaptive sampling method, in which we use the entropy consistency measure Q(a) to evaluate the consistency of the joint morphology information contained in adjacent JRC samples. Then the sampling interval is automatically adjusted according to the threshold Q(at) of the entropy consistency measure to ensure that the degree of change of RJST information between JRC samples is the same, and ultimately makes the representative RJST information in the collected JRC samples more balanced. The application results of actual cases show that the proposed method can obtain the scale effect in the JRC efficiently and reliably.