NUMERICAL MODELING OF ROCK-BIT INTERACTION IN LAMINATED FORMATIONS

Numerical modeling of the rock-bit interaction process in laminated fo rmation has been performed using a finite element approach. A finite e lement program was developed with the assumption of plane strain. Anis otropic elements, dynamic, loading, progressive failure, and variable stiffness were used to represent the actual penetration process. The H oek and Brown failure criterion was used in the failure analysis. An i nteration method, using an incremental approach, has been applied for the continuous tooth penetration process where displacements, axial lo ads, strength and stiffness of elements are modified after each iterat ion. The program provides quantitative information on stress, displace ment, and rock failure for each iteration. Furthermore, deviation due to laminated formation can be inferred and the effects of changing bit geometry can be assessed. The model also shows good quantitative agre ement with laboratory wedge indentation tests.