温度与应力对破碎煤岩体压实变形特征的影响
Influence of temperature and stress on compaction deformation characteristics of broken coal and rock mass
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摘要: 为了得到应力和温度对采空区破碎煤岩体渗透特性及压实特性的影响，通过自主设计的渗透系统以分级加载的方式对破碎煤样进行渗流试验，得到考虑温度的压实破碎煤体的本构模型。结果表明：渗透率随温度变化总体呈上升趋势，在采空区遗煤自燃的过程中，随着温度的升高，煤体内部细观结构发生变化，颗粒的堆积变得更为松散，从而导致破碎煤体的渗透率增大；破碎煤体孔隙度随着轴向应力的升高呈负指数下降趋势，孔隙度和碎涨系数都随着温度的升高而升高，125 ℃对应的碎涨系数比25 ℃对应的碎涨系数大0.03；压实变形过程中破碎煤体的割线模量Es和切向模量Et均随应变的增加而升高，且在相同应变条件下，温度越高破碎煤体的Es和Et越低。通过对在应力σi作用下破碎样的割线模量与温度的关系进行拟合，建立了考虑温度的压实破碎煤体的本构关系。Abstract: In order to obtain the influence of stress and temperature on the permeability and compaction characteristics of crushed residual coal, this paper conducts seepage tests on crushed coal samples by means of graded loading through an independently designed permeability system, and obtains the constitutive model of compacted crushed coal considering temperature. The results show that: the permeability increases with the change of temperature. In the process of spontaneous combustion of residual coal in goaf, with the increase of temperature, the internal microstructure of coal changes and the accumulation of particles becomes more loose, which leads to the increase of permeability of broken coal. The porosity of broken coal body shows a negative exponential decreasing trend with the increase of axial stress. The porosity and coefficient of broken expansion both increase with the increase of temperature. The coefficient of broken expansion corresponding to 125 ℃ is 0.03 larger than that corresponding to 25 ℃. Secant modulus Es and tangential modulus Et of broken coal increase with the increase of strain during compaction deformation, and under the same strain condition, Es and Et of broken coal decrease with the increase of temperature. By fitting the relationship between secant modulus and temperature of fractured samples under the action of stress σi, the constitutive relation of compacted fractured coal considering temperature is established.
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