Study on unloading energy characteristics of limestone in different crossing sections

¹ State Key Lab of Hydraulics and Mountain River Eng, Editorial Department, 610065 Chengdu, China
² China Railway First Survey and Design Institute Group Co., Ltd, 710043 Xian, China

^* Corresponding author: liujf@scu.edu.cn

Abstract

In order to study the energy characteristics of limestone under different initial confining pressures and different unloading rates, based on MTS815 flex test GT rock mechanics test system and acoustic emission (AE) 3D positioning real-time monitoring system, the unloading test and acoustic emission synchronous monitoring of limestone are carried out. The results show that: (1) the pre peak energy process is dominated by energy accumulation, but mainly occurs in the loading stage. The proportion of energy in the unloading stage is basically unchanged, and the proportion of elastic energy is more than 0.9, which fluctuates only before the failure. During the failure, the proportion of energy in the stress drop changes dramatically, and the proportion of elastic energy decreases rapidly to 0. (2) In the coal measure strata, the energy dissipation is the main factor, the dissipation energy and its proportion increase rapidly, while in the front of coal measure strata, the energy release is the main factor, the elastic energy decreases rapidly and the dissipation energy does not increase. (3) The proportion of coal bearing strata in front of coal bearing strata is 0.68 and 0.57 respectively. Unloading elastic energy ratios before coal-bearing strata and coal-bearing strata are 0.824 and 0.876, respectively.