Experimental Study on Mesodamage of Migmatite Under Cyclic Loading and Unloading
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ORIGINAL PAPER
Experimental Study on Mesodamage of Migmatite Under Cyclic Loading and Unloading Laishan Chang . Yuan Chang . Yalin Wu . Xiaoxiao Sang
Received: 27 April 2020 / Accepted: 28 May 2020 Ó Springer Nature Switzerland AG 2020
Abstract To study the mesodamage of migmatite under cyclic loading, single cycle loading and unloading tests of migmatite were carried out under different confining pressures (r3) and stress ratios (p), and acoustic emission (AE) technology was used to monitor the evolution of microcracks. Additionally, the mesodamage of migmatite was analyzed from the porosity and T2 spectrum distribution measured by nuclear magnetic resonance (NMR) spectroscopy. The results show that the peak stress ratios (pmax) of migmatite under different r3 are different, and as the value of r3 increases, the migmatite gradually undergoes a change from tension to shear failure. Moreover, with the increase in r3, high-frequency signals gradually appeared, indicating that the increase of r3 to a certain extent limited the generation of large size microcracks. The variations in damage variables defined by the number of AE hits and porosity are the same, ‘‘steep increment type,’’ and increase suddenly when approaching pmax. Furthermore, r3 slightly affects the pore throat distribution of migmatite. In addition, r3 has a certain inhibitory effect on the porosity of migmatite and accumulation of L. Chang School of Mining Engineering, University of Science and Technology LiaoNing, Anshan 114051, China Y. Chang (&) Y. Wu X. Sang School of Civil Engineering, University of Science and Technology LiaoNing, Anshan 114051, China e-mail: [email protected]
mesodamage. However, when r3 exceeds a critical value, the inhibitory effect becomes a promoting effect. Keywords Mesodamage Cyclic loading and unloading AE monitoring NMR Migmatite
1 Introduction Migmatite is the main surrounding rock of Dagushan Iron Mine, under the rainfall, groundwater, weathering, and artificial disturbance, the mechanical property of rock gradually decrease (Qin et al. 2019; Feng et al. 2020; Wang et al. 2020a). The mesodamage evolution trend of under cyclic loading is important for the early warning of rock mass instability, and a series of studies have been carried out on the rock characteristics under cyclic loading (Li et al. 2019). Zheng et al. (2020) analyzed the fatigue and damage of jointed mudstone and proposed a new damage variable. Wu et al. (2019) studied the damage evolution of sandstone under loading and unloading conditions. Peng et al. (2019) evaluated the effect of confining pressure (r3) on the deformation of sandstone under cyclic loading. Acoustic emission (AE), a nondestructive monitoring method, has been widely used in rock mechanics such as AE characteristics at different stress levels and loading rates by uniaxial cyclic loading and unloading tests (Meng et al. 2019), quantitative energy evolution
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Geotech Geol Eng
during fracturing tests (Zhou et al.
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