Evaluation of stress-controlled coal swelling processes
Evaluation of stress-controlled coal swelling processes
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DOI：
10.1016/j.coal.2010.06.005
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发表时间：
2010-09-01
影响因子：
5.6
通讯作者：
Mao, Xianbiao
中科院分区：
文献类型：
--
作者：
Liu, Jishan;Chen, Zhongwei;Mao, Xianbiao
应力控制膨胀试验通常在实验室进行，以表征煤在气体吸附作用下渗透率的演变。通常，即使在有效应力保持不变的情况下，渗透率也会因气体吸附引起的膨胀而降低。由于多孔煤的渗透性仅由有效应力决定，因此这种行为仍然是一个谜。当这些观测结果被解释时，假设是火柴棍或立方煤模型。在此假设下，由于贯通裂缝导致基质块体完全分离，基质膨胀不会影响煤的渗透性。这就是为什么目前的煤渗透率模型在解释这种不一致性方面收效甚微的原因。一般认为破坏的原因是实验条件与模型假设不一致。但本文认为其原因可能是未考虑裂隙与基质之间的内部作用。在这项研究中，开发了一个能够复制这种明显异常行为的模型。我们考虑裂隙煤块之间的相互作用，其中裂隙不会在相邻的基质块之间产生完全的分离，但存在坚固的岩石桥。我们适应膨胀应变的作用，既在接触桥上保持清晰的面分开，也在这些桥之间的非接触跨度上。膨胀对这两种成分的影响是相互竞争的：由于桥接接触的膨胀而增加孔隙度和渗透率，但由于中间自由面膨胀而降低孔隙度和渗透率。在此条件下，建立了新的渗透率模型。该模型是耦合煤-气相互作用多物理场的关键交联。本文提出了该渗透率模型的建立方法，并将其应用于煤-气相互作用的多物理场模拟。(C) 2010 Elsevier B.V.版权所有
Stress-controlled swelling tests are normally conducted in the laboratory to characterize the evolution of coal permeability under the influence of gas sorption. Typically reductions in permeability are observed from gas-sorption-induced swelling even where effective stresses remain constant. This behavior remains enigmatic as the permeability of the porous coal is determined by the effective stress only. When these observations were interpreted, a matchstick or cubic coal model was assumed. Under this assumption, matrix swelling would not affect coal permeability because of the complete separation between matrix blocks caused by through-going fractures. This is why current coal permeability models have little success in explaining this inconsistency. It is generally believed that the reason for the failure is the inconsistency between the experimental conditions and the model assumptions. However, in this paper, it is considered that the reason may be the internal actions between coal fractures and matrixes have not been taken into consideration. In this study, a model capable of replicating this apparently anomalous behavior is developed. We consider the interactions of the fractured coal mass where cleats do not create a full separation between adjacent matrix blocks but where solid rock bridges are present. We accommodate the role of swelling strains both over contact bridges that hold cleat faces apart but also over the non-contacting span between these bridges. The effects of swelling act competitively over these two components: increasing porosity and permeability due to swelling of the bridging contacts but reducing porosity and permeability due to the swelling of the intervening free-faces. Under these conditions, a new permeability model is formulated. The new model is the key cross link that couples the multiphysics of coal-gas interactions. The formulation and incorporation of this permeability model into the multiphysics simulation of coal-gas interactions are presented in this paper. (C) 2010 Elsevier B.V. All rights reserved.