THEORETICAL ANALYSIS AND EXPERIMENTAL STUDY ON PERMEABILITY OF GAS-BEARING COAL
TAO Yunqi1，2，XU Jiang1，CHENG Mingjun1，LI Shuchun1，PENG Shoujian1
(1. Key Laboratory for Exploitation of Southwestern Resources and Environmental Disaster Control Engineering，Ministry of Education，Chongqing University，Chongqing 400044，China；2. Henan Provincial Coal Seam Gas Development and Uitilization Co.，Ltd.，Zhengzhou，Henan 450016，China)
Abstract：From the basic defination of the porosity，the absorption gas expansion，thermoelastic expansion of coal matrix and the influnce caused by gas pressure on coal matrix body dirtortion are considered fully. After showing the function relation between coal porosity and volumetric strain，temperature，and gas pressure，by using Kozeny-Carman equation，the dynamic evolvement model of permeability which is comprehensively influenced by effective stress，temperature，and gas pressure is established before expansion and under the condition of compression. Correlative test data show that this model has good applicability，and can reflect the development of the porosity under certain condition. The study shows that：porosity development degree and permeability of coal have good consistency，and the permeability increases as the porosity development degree increases；when temperature and gas pressure are fixed values，porosity reduces as the effective stress increases，meanwhile the tendency of the reducement is more obvious when the effective stress is smaller；when the effective stess and gas pressure are fixed values，porosity reduces as the temperature increases，however，its decrescent extent is basically not influenced by effective stress；when temperature and effective stress are fixed values，the permeability of coal reduces rapidly firstly and slowly whereafter with gas pressrure increasing. The study of the relationship between gas-bearing coal permeability and effective stress，temperature and gas pressure provides the theoretical foundation for the study of multi-field coupling problem including temperature field. It gives technical support for increasing efficiency of gas drainage in high temperature mine.
