1. A high temperature resistance backfilling material for underground coal gasification: Microstructure, physical and mechanical characteristics.
- Author
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Li, Jian, Bai, Jinwen, Feng, Guorui, Han, Yanna, Wu, Guowei, Ma, Junbiao, Shi, Xudong, and Mi, Jiachen
- Subjects
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POROSITY , *COAL gasification , *THERMAL properties , *FLY ash , *CALCIUM aluminate - Abstract
In underground coal gasification (UCG), the backfilling body is utilized to reinforce the isolated coal pillars and provide support for the combustion cavity, but elevated temperatures can lead to a degradation in the carrying capacity. This paper presents an innovative high temperature resistance backfilling material for UCG. The evolution law and high temperature resistance mechanisms of its bearing capacity under high temperatures were mainly investigated, including its thermal expansion, compressive strength, acoustic emission characteristics, thermal stability, phase composition, micromorphology, and pore structure. The result indicates that the calcium aluminate cement (CAC) - fly ash (FA) backfilling body exhibited a non-linear variation in compressive strength with increasing temperature. The compressive strength still maintains 5 MPa at 1000 ℃, meeting the requirements for coal mine backfill. The FA induces secondary hydration in the backfilling body at elevated temperatures, resulting in the formation of a more compact C-A-S-H gel phase. Furthermore, the formation of AlO(OH), C 12 A 7 , and C 6 S 6 H is another reason for the enhancement of the high-temperature resistance of specimens. After 600 ℃ treatment, the porosity of specimens exhibited a significant increase, reaching 30.57 % at 1000 ℃. The thermos-mechanically coupled constitutive equation of the backfilling body was constructed, showing that as temperature rises, the brittleness diminishes and the damage factor experiences a substantial increase after 500 ℃. Experimental results provided strong technical support for strata control of UCG. • A high temperature resistance backfilling material for UCG was proposed for the first time. • The relationship between mechanical properties and thermal physical properties of CAC-FA backfilling body was studied. • The high temperature resistance mechanism of backfilling body was described. • The constitutive model of CAC-FA backfilling body for UCG was established. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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