Abstract
Most of the rock masses in the outer crust of the Earth are discontinuous. They are divided by joints, faults, fractures, etc. And those discontinuities, generally referred to as joints, greatly affect the property of the rock masses. The paper experimentally investigates the stress wave propagation crossing the jointed specimens. The tests were conducted on the split Hopkinson pressure bar (SHPB). The test specimens consist of two parts cast by cement mortar. Both parts have an irregular surface, and they were designed to match each other completely. The surfaces where two parts meet make an artificial joint. The surfaces of the joints were scanned by a three-dimensional scanner to obtain its actual topography and then to calculate the roughness of the surface, i.e., the joint roughness coefficient (JRC). A set of jointed specimens with JRC ranging from 0 to 20 were made and used in dynamic compression experiments. During the tests, signals were captured by strain gauges stuck on the incident and transmitted bars of the SHPB apparatus. The incident, reflected, and transmitted waves across the jointed specimens were obtained from the test records. We found out that more stress wave would transmit through the jointed specimen with larger JRC. Besides, collected data were processed to get the dynamic stress-strain relation of jointed specimens and the stress-closure curves of the joints. The results show that the joint increases the deformation of the specimen, and the stiffness of the jointed specimen would increase slightly when the joint is rougher.
Highlights
Geological resources serve as the basis for modern life society. ey are so crucial that many researchers work on relevant projects, such as mining, geological exploration, and geomechanics [1, 2]
We found that the acoustic wave velocity of the mortar specimen with flat joint surface is about 2630 m/s, smaller than that of the mortar specimen with rough joint surface (JRC 8.36) that is about 2800 m/s
The acoustic wave velocity of the granite specimen with a flat joint surface is about 3410 m/s, smaller than that of the granite specimen with the rough joint surface (JRC 8.36) that is about 3560 m/s. ese two sets of jointed specimens were made in different ways. e mortar specimens were cast by printed mold
Summary
Geological resources serve as the basis for modern life society. ey are so crucial that many researchers work on relevant projects, such as mining, geological exploration, and geomechanics [1, 2]. Ey are so crucial that many researchers work on relevant projects, such as mining, geological exploration, and geomechanics [1, 2]. Among those projects, geomechanics is the foundation of them, which involves the study of the mechanics of soil and rock. One of the joint models is called the Bandis-Barton model (B-B model) that was put forward by [6] based on quantities of static experiments It is a hyperbolic function describing the stress-closure curves of joints in normal static loading, which is commonly accepted and used to describe the deformation of the joint
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