Experimental investigation on the dynamic tensile characteristics of conglomerate based on 3D SHPB system

The mechanical properties and failure characteristics of conglomerate, main components of gravel layer, are of great significance to the study of efficient drilling methods in gravel layer. However, there are few works published previously, especially rare in terms of dynamics. While drilling in gravel layer, the bottom hole rock is subjected to complex loads, including impact loading and in-situ stress. The static and dynamic tension behaviours of conglomerate are tested by outcrop in this paper. Based on GCTS and 3D SHPB systems respectively, the static and dynamic tensile properties are analyzed, and the energy consumption while failure and the influence of axial static load on dynamic tensile characteristics are discussed. Results show that the tensile characteristics of conglomerate have a significant strain rate correlation, and the dynamic tensile strength is significantly higher than that of static; The strength in both impact direction and axial direction increase linearly with the loading strain rate, while the failure strain decreases linearly; As there is no axial load and the strain rate is 140.31-248.95 s(-1), the dynamic tensile strength is 75.86-109.91 MPa, and the strength growth factor is 10.55-15.29 between the dynamic and static tensile strength. Due to the energy absorbed by the specimen increases exponentially in the dynamic test, there are a great number of cracks produced accompanied by the collapse of large debris, manifested as the volume crushing failure mainly, while in the static test, there is mainly brittle splitting failure. The dynamic tensile strength can be reduced linearly by increasing the axial static load or reducing the dynamic load. The research has an important theoretical reference for the study of drilling technology and theory in the gravel-rich stratum.