| It is widely known that dynamic mechanical behaviors of materials under impact load are different from that under static load and the dynamic mechanical characteristics of rock under impact load is the basic part of rock dynamics. Due to the complexity of rock materials and the specialty of impact load, the laboratory test is one of the basic measures to characterize the dynamic properties of rock. In this paper, according to the basis of one-dimensional wave theory, resistance strain measurement method is used to measure the stress waves in steel bars under pendulum impact, based on which, test apparatus of rock dynamic behaviors under pendulum impact is formed. At last dynamic compression tests of rock samples are conducted to gain their constitutive curves.(1) Pre-amplifiers and voltage-stabilized sources are produced and their performance is tested to be stable and reliable. Afterwards the stress wave test apparatus is formed and the stress wave propagation in steel bar, triggered by pendulum impact, is measured. The measurement reflects correctly the dynamic mechanical response in the steel bar, by which, the reliability of stress wave test apparatus is confirmed.(2) Test apparatus of rock dynamic behaviors under pendulum impact load is constructed and dynamic compression tests of granite, slate and sand stone samples are conducted. The constitutive curves of these rock samples are obtained. It is shown that the uniaxial compression strength increases when the strain rate of rock sample is enlarged and there is strain rate dependency of uniaxial compression strength.When the test apparatus is utilized to conduct tests of dynamic stress-strain curves of rock, the rise time of incident stress wave lasts long and the waveform is quasi-triangle. The stress equilibrium in the rock sample can be achieved before and after the stress reaches the peak. It is capable of obtaining the constitutive curves of rock samples under strain rates from10Os-1to102s-1. |
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