Energy storage and CO2 disposal in salt-based underground facilities appear to be promising and popular in China. To characterize time-dependent deformation of bedded salt rock is of great significance for long-term operation of salt-based underground facilities. In the paper, acoustic emission (AE) sensor is employed to measure micro fracture in a sample of bedded salt rock, taking from the PT Well No.1 at depth of 1719 m from ground surface, Henan Province, Central China, during whole creep test of 359 days. A variable-viscosity Abel dashpot is proposed to get a better understanding of damage evolution in bedded salt rock. Furthermore, an AE-based fractional derivative model is suggested to characterize the whole regions of creep strain especially the region of unsteady creep.

1 Introduction

To analyze the time dependent behavior of rock salt is significant for underground storage of energy and radioactive waste. The main reason for carven failure is generation and development of cracks in excavated disturbed zones (EDZs) of host rocks. At laboratory study, Acoustic Emissions (AE) corresponds to generation and development of micro cracks. As AE signals take the information about the source, locations of micro cracks, it has advantages in characterizing damage in salt rock during creep.

To get a better known of mechanic properties of salt rock, many researchers devoted their efforts to establish the mathematical model of salt and salt-like material. By replacing a Newtonian dashpot in the classical Nishihara model with the fractional derivative Abel dashpot, Zhou et al. (2012) proposed a creep constitutive model with time-based fractional derivative, and the results estimated by the new model are in better agreement with the experimental data.

In this paper, a new fractional derivative constitutive model of salt rock based on acoustic emission is proposed to study the time-dependent behavior of salt rock subjected to uniaxial compressive load.

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