Real-time permeability evolution of thermally cracked granite at triaxial stresses. (25th March 2018)

• Record Type: Journal Article
• Authors: Feng, Zijun; Zhao, Yangsheng; Zhang, Yuan; Wan, Zhijun
• Is Part Of: Applied thermal engineering. Volume 133(2018)
• Page Start: 194
• Page End: 200
• Publication Date: 2018-03-25
• Subjects: Thermal cracking -- Granite -- Meso-characteristic -- Permeability -- Threshold temperature; Heat engineering -- Periodicals; Heating -- Equipment and supplies -- Periodicals; Periodicals; 621.40205
• DOI: 10.1016/j.applthermaleng.2018.01.037
• Languages: English
• ISSNs: 1359-4311

Abstract

Highlights: Permeability of thermally cracked granite at triaxial stresses was studied. Micro-crack quantity was measured at different temperature by MPV micro-photometer. Threshold temperature existence of thermal cracking in granite was discussed. Seepage threshold temperature in thermally cracked and stressed granite was found. Abstract: Permeability of Luhui granite with 200 mm in diameter and 400 mm long was measured at triaxial stresses and elevated temperature using 600 °C 20 MN servo-controlled triaxial rock mechanics testing machine. It is found that 300 °C is the threshold temperature ( T c) of permeability change with temperature in thermally cracked granite. The magnitude of permeability is 10 −7 D with a low increase below T c and the permeability whose magnitude is 10 −6 D increases drastically with high amplitude at 300–400 °C while the magnitude is 10 −5 D at 400 °C. Simultaneously, the change of micro-crack quantity in thermally cracked Luhui granite at temperature up to 400 °C was quantificationally investigated by MPV micro-photometer. Two peaks of micro-crack quantity that the length is more than 5 μm and 10 μm respectively exist at temperature up to 400 °C. The temperature scope where micro-crack quantity peak appears in length >5 μm is less than that in length >10 μm. The quantity of micro-crack whose length is >10 μm increases sharply at the rate of one per ten centigrade at temperature above 300 °C. The drastic increase of micro crack above 300 °C is the main reason that permeability increases sharply at temperature above 300 °C in thermally cracked granite. Compared with preheated results, thermal and mechanical coupled effect can more heavily affect granite permeability than only thermal effect.