Development of coring system with in-situ condition for deep rock by ultrasonic
This paper focuses on the methods for rock coring system with the emphasis on hard rock. It is known that the reliability of in-situ conditions of rock estimations is partially dependent on the recovering of rock core technique and equipment, and partially dependent on the nature of rock structure. Extraction of diamond-drilled core from high stress environments can result in the core breaking into discs. Through decades of research, a variety of hard rock coring tools and experimental approaches have been used to obtain the high quality and decrease the failure processes leading to core-discing-type breakage of diamond-drilled cores. One motivation for this research is to use mechanical analysis to identify the main mechanism of the core failure. Based on the knowledge engineering of machinery, the orthogonal experimental design method is applied to analyse the mechanical strength for the new development of coring system. This paper presented the final design of coring tool by ultrasonic mechanism and allow probing deep rock with in-situ conditions. It has the lower axial force and cased the low disturbance of the stress distribution. With the assistant of the rotatory cutting of outside drilling, the vertical and horizontal stress are keeping by the continuous coring process. The results obtained show that, in order to exclude the geometry effect, an average of an appropriate number of simulations, the shape of cutter must be considered for less effect of core quality by stress-strain effect and deformation under ultrasonic coring. The optimization design of the cutter shape is obtained by the FEM with orthogonal experimental design. In the future, this new coring system would support the future exploration of the deep rock mechanics..