Influence of Heating on Tensile Physical-Mechanical Properties of Granite

Xinyu Fang,Shi Liu,Jinyu Xu,Haoyu Wang

doi:10.1515/htmp-2017-0093

Abstract

Abstract Heating procedures dramatically influence the physical-mechanical properties of rock. In this paper, via both numerical simulation and laboratory experiments, we examine the influence of constant temperature period (CTP, from 0.5 to 5 h) and predetermined temperature (PDT, from room temperature to 1,000℃) on the tensile mechanical properties of the Qinling granite, China. Results indicate that: CTP has a significant impact on the tensile mechanical properties of granite. For different PDTs, the density, longitudinal wave velocity (LWV) and tensile strength (TS) of granite decrease with increasing CTP. When CTP reaches the constant temperature turning-point (CTT), heating has fully affected the granite samples. The variation in LWV and TS versus temperature can be divided into four stages: 25–200℃, 200–600℃, 600–800℃ and 800–1,000℃. LWV and TS are negatively related to temperature and are more sensitive to temperature at higher PDTs. In addition, TS is more sensitive to temperature than LWV when PDT increases. The effects of CTP and PDT on LWV are similar to that of TS. Since the measurement of LWV is lossless, researchers can safely determine the appropriate CTP or CTT for any PDT and predict the tensile mechanical properties of rock by LWV analysis.

Highlights

Rock tensile strength (TS) is an important factor for design and stability analysis of underground rock structures, as it Almost all the previous researchers adopted an identical method to heat rock samples
Via both numerical simulation and laboratory experiments, we examine the influence of constant temperature period (CTP, from 0.5 to 5 h) and predetermined temperature (PDT, from room temperature to 1,000°C) on the tensile mechanical properties of the Qinling granite, China
Results indicate that: CTP has a significant impact on the tensile mechanical properties of granite

Summary

Introduction

Rock tensile strength (TS) is an important factor for design and stability analysis of underground rock structures, as it. The most important factors influencing the mechanical properties of rock are the heating rate (HR), constant temperature period (CTP) and PDT. The finite element method (FEM) software Ansys was utilized to simulate the temperature field distribution of cylindrical samples under different HRs and different CTPs, which validated that under other constant conditions, the slower the HR is and longer the CTP is, the better the uniformity of samples’ temperature field distribution is. X. Fang et al.: Tensile Physical-Mechanical Properties of Granite different CTPs (0.5–5 h) and different PDTs (25–1,000°C) on density, longitudinal wave velocity (LWV) and TS of granite Brazilian disc samples was studied. The heating procedure involves heating the air inside the furnace to PDT via the heating silicon carbide rods and holding a constant temperature. The hexahedral element Solid 70, which is commonly used in 3-D thermal transient analysis, is adopted for the simulation. In order to quantitatively analyze the gap between the present temperature and target temperature as well as the homogeneity of the distribution of sample’s temperature field, we define the rate of deviation and the dispersion of node temperatures as follows:

Findings

Discussion

Conclusion