Time-Varying Characteristics of Granite Microstructures after Cyclic Dynamic Disturbance Using Nuclear Magnetic Resonance

Chuanju Liu,Hongwei Deng,Yun Lin,Huatao Zhao,Yuan Wang

doi:10.3390/cryst7100306

Abstract

To investigate the variation in the characteristics of rock microstructure after cyclic dynamic disturbances, a split Hopkinson pressure bar (SHPB) was used to carry out cyclic dynamic impact tests on granite, and the P-wave velocity was used as the characteristic parameter representing the microstructural change. Using the nuclear magnetic resonance (NMR) technique, the porosity and the T2 distribution of rock samples were obtained. The results show that, after the cyclic dynamic disturbance, the P-wave velocity within the rock specimen decreases but rebounds with time. At the elastic phase, when the axial loading increases, the P-wave velocity declines. The T2 limit is shortened, and the cyclic dynamic disturbance process promotes the formation of small pores and decreases the size and quantity of large pores. After the cyclic dynamic disturbance, the porosity of the rock samples was reduced.

Highlights

Rock, a natural heterogeneous material, contains a large number of holes and micro-cracks, and these microstructures have a great influence on the macro-mechanical properties of rock and the potential damage from geotechnical engineering
Johansson et al [2] noted that these features and the level of surface development are the most important factors affecting the mechanical properties of rock
For (c) shown above: the results indicate that, as time elapses, some of the small pores slowly shrink and close, while some of the large pores rebound

Summary

Introduction

A natural heterogeneous material, contains a large number of holes and micro-cracks, and these microstructures have a great influence on the macro-mechanical properties of rock and the potential damage from geotechnical engineering. Lindqvist et al [1] studied the effects of mineral particle size, shape, and distribution, porosity, and micro-cracks on the physical and mechanical properties of rock. Hatzor et al [3] conducted a study on the relationship between the microstructure of dolomite and initial stress of crack initiation and found that the microstructure had a great influence on the ultimate rock strength. Prikry et al [9] found that the effect of particle size on the compressive strength of rock is the most important factor. Nafi Toksoz [12] proposed that the change

Methods

Results

Conclusion