关键词: 采矿工程, 深部灰岩, 蠕应变特性, 单轴蠕变试验, 分级加载, 长期强度

Abstract: In the aim of exploring the creep characteristics of deep limestone, uniaxial creep tests were conducted with GDS-VIS triaxial rheometer by step loading on specimens from different depths. According to the test results, the mean value (0.758) of the ratio of long-term strength to instantaneous strength decreases as depth increases. Furthermore, the variation law of axial creep strain increment of limestone in different depths under different stress levels was investigated, and then axial creep strains were obtained by accumulating creep strain increment. Results revealed that creep strain increment decreased first and then increased dramatically with the increasing of stress level. As depth increased, the percentage of stress corresponding to the minimum creep strain increment obviously increased. Moreover, with the increase of loading level, the axial creep strain experienced three development stages from decelerated growth, constant growth and accelerated growth. When the stress percentage ratio of constant load was within the range from 60% to 70%, creep strain tended to be stable; whereas beyond the range, the creep strain acceleratedly increased until creep failure. Therefore, the range of stress percentage could be taken as reference for identifying whether creep failure will happen or not for deep limestone.

Key words: mining engineering, deep limestone, creep strain characteristics, uniaxial creep test, step loading, long-term strength