本文關(guān)鍵詞：含瓦斯煤流固耦合數(shù)學(xué)模型及其應(yīng)用，由筆耕文化傳播整理發(fā)布。

含瓦斯煤流固耦合數(shù)學(xué)模型及其應(yīng)用

重慶大學(xué)碩士學(xué)位論文

（學(xué)術(shù)學(xué)位）

學(xué)生姓名：莫道平

指導(dǎo)教師：萬 玲 教 授

專 業(yè)：力 學(xué)

學(xué)科門類：工 學(xué)

重慶大學(xué)航空航天學(xué)院

二O一四年五月

Coal Containing Methane Fluid-solid

Coupling Mathematical Model and Its

Application

A Thesis Submitted Chongqing University

in Partial Fulfillment of the Requirement for the

Master’s Degree of Engineering

By

Mo Daoping

Supervised by Prof. Wan Ling

Specialty: Mechanics

College of Aeronautics and Astronautics of Chongqing University,

Chongqing, China

May 2014

摘 要

為了研究含瓦斯煤巖中瓦斯運(yùn)移規(guī)律，以多孔介質(zhì)有效應(yīng)力原理為基礎(chǔ)，考慮含瓦斯煤巖的孔隙率、滲透率動態(tài)變化規(guī)律以及煤巖的彈塑性本構(gòu)關(guān)系，建立起了含瓦斯煤彈塑性流固耦合數(shù)學(xué)模型。借助于COMSOL Multiphysics 多場耦合數(shù)值分析軟件對模型的正確性予以驗(yàn)證，同時分析了煤巖中瓦斯鉆孔抽放影響因素。本文取得了以下研究成果：

(1) 建立起了含瓦斯煤彈塑性流固耦合數(shù)學(xué)模型。該模型能夠充分反映煤巖變形條件下的煤巖孔隙率和滲透率的動態(tài)變化規(guī)律、彈塑性本構(gòu)關(guān)系；氣體的可壓縮性以及氣體滲流的滑脫效應(yīng)；瓦斯?jié)B流與煤巖變形之間的耦合關(guān)系。并通過實(shí)驗(yàn)室含瓦斯煤巖常規(guī)三軸試驗(yàn)結(jié)果與模擬結(jié)果進(jìn)行對比，結(jié)果表明：本文所建立的模型能夠較好的反映含瓦斯煤在三軸應(yīng)力作用下瓦斯的滲流規(guī)律和煤巖的變形特性。

(2) 對含瓦斯煤瓦斯鉆孔抽放的影響因素進(jìn)行了模擬分析，得出了以下結(jié)論：

①煤層內(nèi)瓦斯壓力會隨著鉆孔抽放時間的增加而降低，而且在鉆孔抽放初始階段瓦斯壓力下降明顯，隨著抽放時間的增加煤層內(nèi)瓦斯壓力下降速度降低。

②瓦斯鉆孔抽放的過程會煤巖骨架受到的有效應(yīng)力增加，從而導(dǎo)致煤巖的孔隙率和滲透率下降，正是由于這個原因才使煤層瓦斯鉆孔抽放后期瓦斯壓力下降速度明顯減緩。

③圍壓對煤巖內(nèi)瓦斯壓力的分布有影響，當(dāng)增加圍壓時，煤巖內(nèi)瓦斯壓力分布會高于低圍壓條件下的瓦斯壓力，同時，煤巖內(nèi)的孔隙率和滲透率都會下降，而且在靠近鉆孔的地方下降得更為明顯。煤巖卸壓狀態(tài)下有利于瓦斯的抽放。

④負(fù)壓抽放對于煤層內(nèi)瓦斯壓力的改變是非常有限的，負(fù)壓抽采只是使鉆孔周圍局部區(qū)域的瓦斯壓力略低于常用抽采，對于遠(yuǎn)離鉆孔的大部分區(qū)域來說，負(fù)壓抽放對煤層內(nèi)瓦斯壓力分布的影響幾乎可以忽略不計。

⑤增大鉆孔半徑有利于煤層內(nèi)部瓦斯下降、擴(kuò)大有效抽放半徑，在同一時刻，瓦斯的有效抽放半徑會隨著鉆孔半徑的增加而增大，但是隨著鉆孔半徑的增加，這種增加的趨勢會不斷的放緩。

⑥多孔抽放過程中，在靠近鉆孔的地方單一鉆孔對煤層內(nèi)瓦斯壓力影響較大，越靠近鉆孔瓦斯壓力越低；在遠(yuǎn)離鉆孔的地方，單一鉆孔對瓦斯壓力的影響作用降低，，沿多個鉆孔的周圍形成了一個集中的瓦斯降壓區(qū)。

關(guān)鍵詞：含瓦斯煤，流固耦合，數(shù)值分析，滲透率

ABSTRACT

In order to study the migration law of gas in the coal containing methane. Based on the principle of effective stress in porous media, considering the porosity, the dynamic variation of the permeability and the elastic-plastic constitutive relationship of coal containing gas, establish a elastic-plastic fluid solid coupling mathematical model of coal containing gas. Use COMSOL Multiphysics to verify the correctness of the model. At the same time, we analysis the factors affecting of gas boreholes in coal containing gas. This paper has made the following findings:

(1) The elastic-plastic fluid solid coupling mathematical model of coal containing gas is established. Compared to the laboratory results and simulation results，The results show that: the model established in this paper can reflect the seepage law of gas and deformation characteristics of coal.

(2) By analysis the factors affecting of gas boreholes in coal containing gas, draws the following conclusion:

① Coal seam gas pressure will decrease with the increase of time, and at the initial stage of drilling pump gas pressure decreased significantly, with the drainage time increase of coal seam gas pressure is reduced fall velocity.

② Gas drilling drainage process will make the coal and rock skeleton effective stress should be increased, resulting in the coal and rock porosity and permeability decreasing, it is for this reason that coal seam gas drainage gas pressure, the rate of decline slowed down significantly in late.

③ Confining pressure will affect the distribution of gas pressure, with the increase of confining pressure, the gas pressure will increase, and porosity and permeability will decrease, but near the drainage hole pressure drop obviously. Coal unloading conditions will conducive to gas drainage.

④ The effect of negative pressure pumping is very limited to coal seam inner gas pressure change. Negative pressure drainage is just slightly reducing gas pressure around the borehole. For away from the drilling drainage region, the negative pressure pumping effect on coal seam gas pressure distribution is almost negligible.

⑤ Increase the borehole radius is helpful to reduce the coal inner gas pressure and expand the effective drainage radius; at one time, effective drainage radius increases with the hole radius, but with the increase of hole radius, this increased trend will

continue to slow down.

⑥ In the process of multi boreholes, near the borehole, a single borehole has greater influence on the gas pressure of coal seam. The more close to the borehole gas pressure is low. Away from the borehole, a single borehole has less influence on the gas pressure of coal seam，around the drilling area forms a centralized gas depressor area.

Keywords: Coal containing methane, Fluid solid coupling, Numerical analysis,

Permeability

  本文關(guān)鍵詞：含瓦斯煤流固耦合數(shù)學(xué)模型及其應(yīng)用，由筆耕文化傳播整理發(fā)布。