The Loading Rate Effect on the Fracture Toughness of Marble Using Semicircular Bend Specimens

Fengqiang Gong,Shanyong Wang,Yunliang Wang,Zhijie Wen

doi:10.1155/2020/8876099

Abstract

A series of dynamic fracture experiments on semicircular bend (SCB) marble specimens were conducted to characterize the loading rate effect using the INSTRON testing machine and the modified SHPB testing system. The fracture toughness of the marble specimens was measured from a low loading rate to a high loading rate (10-3~106 MPa·m1/2s-1). The results show that the fracture toughness will increase with the loading rate. Since the fracture toughness at a magnitude of 10-3 MPa·m1/2s-1 is regarded as the static fracture toughness, the specific value of DI F f (the dynamic increase factor of fracture toughness) can be obtained at the other loading magnitudes from dynamic fracture tests. To describe the variation in DI F f from low to high loading rates, a new continuous model of DI F f was put forward to express the quantitative relation between the loading rate and rock dynamic fracture toughness. It is shown that the new DI F f model can accurately describe the loading rate effect on the dynamic fracture testing data for rock materials.

Highlights

The failure of rock or rock mass, such as rock cutting, hydraulic fracturing, rock burst, and spalling, is closely related to the initiation and propagation of internal cracks under complex stress [1,2,3,4,5,6]
It appears that the load-displacement curve of the specimen during the dynamic fracture process has a similar change rule to that in the static state; the fracture process can clearly be divided into a steady increase phase and a sharp increase phase
The fracture toughness of semicircular bend (SCB) specimens was measured at different loading rates with an INSTRON testing system and a modified split Hopkinson pressure bar (SHPB) system, and the mechanical properties of the marble obtained from the quasistatic and dynamic fracture tests were qualitatively and quantitatively analysed

Summary

Introduction

The failure of rock or rock mass, such as rock cutting, hydraulic fracturing, rock burst, and spalling, is closely related to the initiation and propagation of internal cracks under complex stress [1,2,3,4,5,6]. This phenomenon has been observed in many laboratory tests or engineering sites [7,8,9,10]. This method is used for static and Geofluids (a)

Methods

Results

Discussion

Conclusion