本文選題：復(fù)合加卸載 + 有效應(yīng)力��； 參考：《中國(guó)礦業(yè)大學(xué)(北京)》2015年博士論文

【摘要】：瓦斯抽采作為礦井瓦斯治理的基本技術(shù)手段之一,在突出礦井、高瓦斯礦井以及瓦斯礦井的深部采區(qū)發(fā)揮著至關(guān)重要的作用。煤層受采動(dòng)影響后,煤層應(yīng)力重新分布,煤體局部發(fā)生損傷甚至破壞變形,煤體孔隙一裂隙結(jié)構(gòu)和滲透能力發(fā)生改變,孔隙率和滲透性的改變不僅會(huì)導(dǎo)致瓦斯?jié)B流速度和孔隙壓力分布的變化,而且會(huì)引起煤層應(yīng)力和位移的改變。對(duì)于水力擴(kuò)孔后的抽采鉆孔而言,其周圍煤體中同樣存在著采動(dòng)應(yīng)力場(chǎng)和瓦斯?jié)B流場(chǎng)的耦和效應(yīng),水力擴(kuò)孔形成的鉆孔開挖效應(yīng)對(duì)煤體滲透性的影響比較明顯。為了深入探討水力擴(kuò)孔開挖效應(yīng)對(duì)鉆孔周圍煤體滲透率的影響,本文以本煤層水力擴(kuò)孔工藝技術(shù)為工程背景,開展復(fù)合加卸載條件下含瓦斯煤樣滲流特性試驗(yàn),建立抽采鉆孔周圍煤體流固耦合模型,進(jìn)行普通抽采鉆孔和水力擴(kuò)孔鉆孔周圍煤體應(yīng)力場(chǎng)分析及瓦斯?jié)B流規(guī)律數(shù)值模擬,最后運(yùn)用體現(xiàn)工作面瓦斯抽采效果的煤層殘余瓦斯含量和鉆孔瓦斯流量等數(shù)據(jù),與數(shù)值模擬結(jié)果進(jìn)行對(duì)比驗(yàn)證。首先,基于鉆孔周圍煤體切向應(yīng)力由原巖應(yīng)力先升高至峰值強(qiáng)度而后減小至殘余強(qiáng)度、徑向應(yīng)力由原巖應(yīng)力逐步遞減直至破壞卸荷的演變特征,以受載含瓦斯煤體滲流特性試驗(yàn)裝置為實(shí)驗(yàn)平臺(tái),開展了常規(guī)三軸加載和復(fù)合加卸載應(yīng)力路徑下含瓦斯煤樣滲流特性試驗(yàn),研究了圍壓、軸壓、應(yīng)力路徑、孔隙壓力與煤樣滲透率之間的定性定量關(guān)系。常規(guī)三軸加載應(yīng)力路徑為固定圍壓的同時(shí),持續(xù)增加軸壓直至煤樣進(jìn)入殘余強(qiáng)度階段；復(fù)合加卸載應(yīng)力路徑為持續(xù)增加軸壓的同時(shí),減小圍壓直至煤樣進(jìn)入殘余強(qiáng)度階段,尤其是復(fù)合加卸載應(yīng)力路徑與鉆孔周圍煤體應(yīng)力變化過(guò)程極為相似。常規(guī)三軸加載含瓦斯煤樣和復(fù)合加卸載含瓦斯煤樣的全應(yīng)力-應(yīng)變曲線均可以分為煤樣壓密階段、線彈性階段、屈服階段、峰后軟化階段和殘余強(qiáng)度階段等五個(gè)階段；在固定軸壓和圍壓的條件下,常規(guī)三軸加載煤樣滲透率隨著孔隙壓力的升高呈現(xiàn)先減小而后增大的“V”字形變化規(guī)律；在固定軸壓和孔隙壓力的條件下,常規(guī)三軸加載煤樣滲透率隨著圍壓的增大而呈現(xiàn)指數(shù)函數(shù)規(guī)律性下降；在屈服強(qiáng)度前后,常規(guī)三軸加載煤樣體積應(yīng)變與滲透率均呈指數(shù)函數(shù)關(guān)系變化。復(fù)合加卸載含瓦斯煤樣的峰值強(qiáng)度較常規(guī)三軸加載含瓦斯煤樣的峰值強(qiáng)度更低；復(fù)合加卸載煤樣峰值強(qiáng)度時(shí)的軸向變形均小于常規(guī)三軸加載煤樣峰值強(qiáng)度時(shí)的軸向變形,復(fù)合加卸載煤樣峰值強(qiáng)度時(shí)的徑向變形均大于常規(guī)三軸加載煤樣峰值強(qiáng)度時(shí)的徑向變形；隨著軸向應(yīng)變的持續(xù)增大,復(fù)合加卸載煤樣滲透率呈現(xiàn)先減小后增大的變化規(guī)律；復(fù)合加卸載條件下卸載圍壓引起煤樣屈服后滲透率的增加量較常規(guī)三軸加載煤樣屈服后滲透率的增加量更大；卸載起始軸壓的改變可引起加卸載階段煤樣滲透率差異性演變；卸載起始時(shí)刻煤樣滲透率隨著卸載起始圍壓的增大呈現(xiàn)指數(shù)函數(shù)規(guī)律性下降；相同的卸載起始軸壓和卸載起始圍壓時(shí),隨著孔隙壓力的升高,復(fù)合加卸載煤樣峰值強(qiáng)度呈線性降低,從而導(dǎo)致煤樣失穩(wěn)破壞的加速出現(xiàn),進(jìn)而縮短了煤樣滲透率發(fā)生劇烈改變的時(shí)間。接著,開展了復(fù)合加卸載應(yīng)力路徑下煤樣孔隙率測(cè)定實(shí)驗(yàn),在分析復(fù)合加卸載煤樣有效應(yīng)力作用機(jī)制的基礎(chǔ)上,從孔隙率的基本定義出發(fā),同時(shí)考慮煤樣吸附膨脹變形、孔隙氣體壓縮變形和熱膨脹變形等影響因素,建立復(fù)合加卸載條件下煤樣孔隙率演化模型；對(duì)比國(guó)內(nèi)外各類滲透率演化模型,以立方定律和受載煤體應(yīng)力-應(yīng)變本構(gòu)方程為橋梁,建立復(fù)合加卸載條件下煤樣滲透率演化模型；考慮瓦斯流動(dòng)克林伯格效應(yīng)、瓦斯吸附-解吸-擴(kuò)散過(guò)程的傳質(zhì)特征、煤體的吸附膨脹效應(yīng)等影響因素,建立復(fù)合加卸載含瓦斯煤體非線性滲流場(chǎng)方程；通過(guò)對(duì)鉆孔周圍煤體彈塑性分析,求解得到鉆孔周圍煤體應(yīng)力場(chǎng)、位移場(chǎng)的解析表達(dá)式；通過(guò)耦合變量,實(shí)現(xiàn)應(yīng)力場(chǎng)、變形場(chǎng)、滲流場(chǎng)等多物理場(chǎng)耦合,并最終實(shí)現(xiàn)鉆孔周圍含瓦斯煤體流固耦合模型的建立。其中,不同卸載起始軸壓條件下,復(fù)合加卸載煤樣的孔隙率演變規(guī)律表現(xiàn)為沿著加卸載應(yīng)力路徑的逐步推進(jìn),煤樣內(nèi)孔隙率均呈現(xiàn)先減小而后增大的變化規(guī)律,但平均有效應(yīng)力與煤體孔隙率的關(guān)系曲線卻存在較大差異；復(fù)合加卸載煤樣在外界應(yīng)力和孔隙壓力的共同作用下,煤樣在不同的受載階段均受到有效應(yīng)力的約束,區(qū)別之處在于不同受載階段時(shí)三類有效應(yīng)力各自所占的比重存在著差異；對(duì)于復(fù)合加卸載煤樣而言,在壓密階段和線彈性階段有α→φ,在屈服階段和峰后軟化階段有φ≤α≤φd,在殘余強(qiáng)度階段有φd≤α≤φc；復(fù)合加卸載煤樣孔隙率演化方程及滲透率演化方程可以分別表述為然后,以復(fù)合加卸載應(yīng)力路徑下含瓦斯煤樣的軸向應(yīng)力-軸向應(yīng)變-滲透率演變規(guī)律為理論基礎(chǔ),結(jié)合鉆孔開挖后周圍煤體應(yīng)力重分布規(guī)律,分析了抽采鉆孔周圍煤體的滲透率演變特征,將抽采鉆孔周圍煤體視為黏彈塑性介質(zhì),從而將抽采鉆孔周圍煤體從鉆孔孔壁到煤體深處依次劃分為殘余強(qiáng)度區(qū)、塑性軟化區(qū)、黏彈性區(qū)和原始應(yīng)力區(qū),其中殘余強(qiáng)度區(qū)和塑性軟化區(qū)內(nèi)的煤體經(jīng)歷過(guò)峰值應(yīng)力的作用,共同組成了極限應(yīng)力區(qū),該區(qū)域的范圍大小決定了鉆孔抽采效果的好壞；建立了考慮煤體流變、剪切擴(kuò)容和塑性軟化特性的鉆孔周圍煤體黏彈塑性模型,并推導(dǎo)了抽采鉆孔周圍不同區(qū)域內(nèi)煤體應(yīng)力-應(yīng)變解；在考慮克林伯格效應(yīng)、瓦斯吸附-解吸-擴(kuò)散過(guò)程的傳質(zhì)特征、煤體吸附膨脹效應(yīng)和孔隙率、滲透率動(dòng)態(tài)演變規(guī)律等影響因素的基礎(chǔ)之上,建立了包括鉆孔周圍煤體內(nèi)瓦斯流動(dòng)非線性滲流方程,滲透率演變方程和鉆孔周圍不同區(qū)域煤體的切向應(yīng)力-徑向應(yīng)力-體積應(yīng)變方程等方程的抽采鉆孔周圍含瓦斯煤體流固耦合模型；運(yùn)用數(shù)值模擬軟件COMSOL,引入鉆孔周圍含瓦斯煤體流固耦合模型,以工作面瓦斯抽采為背景,分析了普通抽采鉆孔周圍煤體應(yīng)力、應(yīng)變變化規(guī)律和抽采后煤層瓦斯含量、煤層滲透率變化規(guī)律及影響因素。其中,沿著遠(yuǎn)離鉆孔方向,鉆孔周圍煤體切向應(yīng)力整體上表現(xiàn)為先增高至峰值、而后下降至原巖應(yīng)力的演變特征,鉆孔周圍煤體徑向應(yīng)力則表現(xiàn)為逐漸升高至原巖應(yīng)力的演變規(guī)律；相同應(yīng)力環(huán)境和煤層賦存條件下,隨著鉆孔孔洞半徑的增加,鉆孔卸壓范圍不斷增大；不同抽采時(shí)刻條件下,鉆孔周圍煤體滲透率沿著遠(yuǎn)離鉆孔方向大致呈現(xiàn)先減小而后又有所恢復(fù)的規(guī)律；隨著抽采時(shí)間的延長(zhǎng),鉆孔周圍一定范圍內(nèi)煤體殘余瓦斯含量均呈現(xiàn)逐漸下降的趨勢(shì)；此外,模擬得到鉆孔抽采30天時(shí)的有效影響半徑為2.77m,與現(xiàn)場(chǎng)實(shí)測(cè)值差別較小最后,針對(duì)水力擴(kuò)孔工藝技術(shù)的特點(diǎn),選取試驗(yàn)礦井典型工作面,對(duì)水力擴(kuò)孔技術(shù)應(yīng)用效果進(jìn)行現(xiàn)場(chǎng)考察,重點(diǎn)考察工作面水力擴(kuò)孔后鉆孔瓦斯抽采效果,建立順層擴(kuò)孔鉆孔開挖模型,借助鉆孔周圍含瓦斯煤體流固耦合模型,分析了順層擴(kuò)孔鉆孔周圍煤體應(yīng)力分布規(guī)律和瓦斯?jié)B透率變化規(guī)律,并和普通抽采鉆孔周圍煤體應(yīng)力分布規(guī)律和瓦斯?jié)B透率變化規(guī)律進(jìn)行了對(duì)比,同時(shí)利用現(xiàn)場(chǎng)考察結(jié)果驗(yàn)證數(shù)值模擬所得到的擴(kuò)孔鉆孔周圍煤體滲透率演變規(guī)律的正確性。其中,鉆孔擴(kuò)孔完成之后,擴(kuò)孔鉆孔周圍煤體的徑向應(yīng)力峰值有所降低,鉆孔周圍煤體所受切向峰值應(yīng)力向遠(yuǎn)離鉆孔的方向轉(zhuǎn)移；水力擴(kuò)孔技術(shù)的實(shí)施擴(kuò)大了抽采鉆孔的有效卸壓范圍,普通抽采孔和擴(kuò)孔鉆孔在抽采一段時(shí)間后,其周圍煤層殘余瓦斯含量均發(fā)生不同程度的下降,但擴(kuò)孔鉆孔較普通抽采孔的下降程度更大、下降范圍更廣；擴(kuò)孔鉆孔瓦斯抽采量相對(duì)于普通抽采鉆孔無(wú)明顯提高,但抽采鉆孔經(jīng)水力擴(kuò)孔之后,鉆孔瓦斯流量衰減系數(shù)減小,鉆孔瓦斯有效抽采時(shí)間增長(zhǎng)；水力擴(kuò)孔影響范圍內(nèi)鉆孔月瓦斯抽采量相比未經(jīng)擴(kuò)孔影響的普通抽采鉆孔有顯著提高。本論文的創(chuàng)新點(diǎn)主要體現(xiàn)在：(1)依據(jù)鉆孔開挖效應(yīng)對(duì)鉆孔周圍煤體應(yīng)力變化的影響,設(shè)計(jì)了復(fù)合加卸載條件下含瓦斯煤滲流特性實(shí)驗(yàn),實(shí)驗(yàn)得到了卸載起始軸壓、卸載起始圍壓、孔隙壓力和應(yīng)力路徑對(duì)煤體滲透率演變的影響規(guī)律；(2)設(shè)計(jì)了復(fù)合加卸載應(yīng)力路徑下煤樣孔隙率測(cè)定實(shí)驗(yàn),并建立了考慮煤樣有效應(yīng)力作用機(jī)制、煤樣吸附膨脹變形、孔隙氣體壓縮變形和熱膨脹變形等因素的復(fù)合加卸載下煤樣孔隙率及滲透率演化模型：(3)在考慮克林伯格效應(yīng)和瓦斯吸附-解吸-擴(kuò)散過(guò)程的傳質(zhì)特征、煤體吸附膨脹效應(yīng)、熱膨脹效應(yīng)、孔隙氣體壓縮效應(yīng)等影響因素的基礎(chǔ)上,建立了抽采鉆孔周圍含瓦斯煤體非線性瓦斯?jié)B流控制方程,通過(guò)抽采鉆孔周圍煤體瓦斯流動(dòng)規(guī)律數(shù)值模擬結(jié)果和現(xiàn)場(chǎng)實(shí)測(cè)抽采鉆孔周圍煤層殘余瓦斯含量的對(duì)比分析,對(duì)非線性瓦斯?jié)B流控制方程的正確性進(jìn)行了驗(yàn)證。
[Abstract]:In order to study the influence of coal seam stress redistribution on the permeability of coal body around the borehole , the influence of gas seepage velocity and gas seepage field on the permeability of coal body is studied .
The stress path of composite loading and unloading is to increase the axial pressure continuously , the confining pressure is reduced until the coal sample enters the residual strength stage , especially the stress change process of composite loading and unloading stress path is similar to that of the coal body stress change process around the borehole .
Under the condition of fixed axial pressure and confining pressure , the normal triaxial loading coal sample permeability decreases with the increase of pore pressure and then increases the variation rule of " V " shape .
Under the condition of fixed axial pressure and pore pressure , the normal three - axis loading coal - like permeability decreases with the increase of confining pressure and the regularity of exponential function decreases ;
Before and after the yield strength , the volumetric strain and permeability of the conventional triaxial loading coal sample varied with exponential function . The peak intensity of the composite loading and unloading gas - containing coal sample was lower than that of the conventional triaxial loading gas - containing coal sample .
the axial deformation of the composite loading and unloading coal sample peak intensity is less than that of the conventional triaxial loading coal sample peak strength , and the radial deformation when the peak intensity of the composite loading and unloading coal sample is greater than that of the conventional triaxial loading coal sample peak strength ;
With the sustained increase of axial strain , the permeability of composite loading and unloading coal sample decreased first and then increased .
Under the condition of compound loading and unloading , the increase of permeability after loading coal sample under the condition of unloading confining pressure is much larger than that of the conventional triaxial loading coal sample yield .
The variation of coal sample permeability in the loading and unloading stage can be caused by the change of unloading initial axial pressure .
The coal sample permeability decreases with the increase of unloading initial confining pressure and the regularity of exponential function decreases .
On the basis of analyzing the effective stress action mechanism of the composite loading and unloading coal sample , the coal sample porosity evolution model is established based on the analysis of the effective stress action mechanism of the composite loading and unloading coal sample , the influence factors of the coal sample adsorption expansion deformation , the pore gas compression deformation and the thermal expansion deformation are taken into consideration , and the coal sample porosity evolution model is established under the condition of composite loading and unloading .
The permeability evolution model of coal sample under the condition of complex loading and unloading is established by using cubic law and the stress - strain constitutive equation of the coal - loaded coal body as the bridge in comparison with the various models of permeability evolution at home and abroad .
Considering the influence factors such as the mass transfer characteristics of the gas flow Klingberg effect , the gas adsorption - desorption - diffusion process , the adsorption expansion effect of the coal body and the like , a nonlinear seepage field equation of the gas - containing coal body is established and unloaded ;
Through the elastic - plastic analysis of the coal body around the borehole , the analytical expression of the stress field and displacement field of the coal body around the borehole is obtained .
The coupling variables are coupled to realize the coupling of multiple physical fields such as stress field , deformation field , seepage field and so on .
Under the combined action of external stress and pore pressure , the coal samples are subject to effective stress at different loading stages . The difference lies in the difference of the specific gravity of three types of effective stress at different loading stages .
For composite loading and unloading coal samples , there is 偽 鈫，

本文編號(hào)：2103750