Experimental investigation on the effect of open fire on the tensile properties and damage evolution behavior of granite

Abstract

The stability of rock mass after fire is a concern of many engineering projects. In this paper, the effects of open fire and different cooling methods on granites were investigated. The static Brazilian test, dynamic Brazilian test, and P-wave velocity test were carried out to evaluate the mechanical properties and damage evolution behavior. A high-speed camera is employed to monitor the failure process of rock. The microstructures of the treated granites were observed by scanning electron microscope (SEM). The results showed that the fire duration and cooling treatment have a significant effect on the P-wave velocity, static nominal tensile strength, and dynamic nominal tensile strength of granite. These characteristics decrease rapidly during 0 to 10 min, and slowly decrease after 20 min. Compared to the air-cooling treatment, the water-cooling treatment has greater damage to the heated granite. To better understand the results, the rapid heating process of open fire heating was simulated using Abaqus software. The results reveal that there is a thinner compressive stress zone at the bottom of the specimen, and there is a large zone in the middle of the sample with higher tensile stress. The crack extension would be expanded due to high tensile stress, leading to the reduction of the tensile strength of the rock. This paper aims to better predict the degree of damage of rock materials after actual fire, as well as preliminarily explore the effect of the fire exposure duration and fire extinguishing method on the tensile properties of rock.

A new statistical damage model for true triaxial pre-and post-peak behaviors of rock considering intermediate principal stress and initial compaction effects

“…In terms of strength, the confining pressure effect of rock peak strength is studied, and there are various research results on the effect of σ 3 on residual strength (Hudson et al., 1972). In terms of deformation, the influence of confining pressure on the pre-peak nonlinear elastic-plastic and elastic modulus (Blake et al., 2019; Yang, 2016; Yin et al., 2022; Zheng et al., 2022c), and the confining pressure dependence of rock post-peak deformation are studied (Peng et al., 2017; Zheng et al., 2022a, 2022b). However, the rock in the deep buried project is under the condition of true triaxial stress (i.e., σ 1 > σ 2 > σ 3 ) (Chen et al., 2017; Gao and Wang, 2021; Haimson, 1978; Kang et al., 2010; Zheng et al., 2020 b), so it is necessary to carry out the true triaxial compression test (TTC).…”

Mixed‐mode I/II fracture properties and failure characteristics of microwave‐irradiated basalt: An experimental study

“…The temperature gradient inside the rock 15,16 is caused by the different degrees of absorption of microwave energy by different minerals, 12,17 which leads to the generation of thermal stress inside the rock 18,19 . When the thermal stress is large enough and exceeds the tensile strength between the grains, microcracks are generated in the rock 20–25 . Therefore, the high‐temperature effect of minerals caused by microwave is a significant factor in the weakening of rocks 17,26 .…”

“…18,19 When the thermal stress is large enough and exceeds the tensile strength between the grains, microcracks are generated in the rock. [20][21][22][23][24][25] Therefore, the high-temperature effect of minerals caused by microwave is a significant factor in the weakening of rocks. 17,26 The ability of materials to absorb microwaves depends on their dielectric properties.…”

Research of Dynamic Tensile Properties of Five Rocks under Three Loading Modes Based on SHPB Device

“…The test methods for rock tensile strength include direct stretching and indirect stretching, i.e., the Brazilian disc [ 15 , 16 ]. The dynamic Brazilian test based on the split Hopkinson pressure bar (SHPB) is a popular and commonly used method to measure the indirect tensile strength of rock materials [ 17 , 18 ]. Rose et al [ 19 ] were the first to use SHPB system to conduct dynamic Brazilian tests on concrete specimens and obtain the dynamic tensile strength of concrete.…”

“…Wu et al [ 14 ] investigated the accuracy of the unidirectional strain calculation method in the dynamic Brazilian test using two types of disc specimens based on the theory of stress wave propagation at the interface and verified the reasonableness of the results through tests. Moreover, different factors have been considered in the dynamic Brazilian tests to carry out relevant studies, such as temperature [ 18 ], anisotropy [ 25 ], and water saturation [ 26 ].…”