黃慶享 李鋒 賀雁鵬 高彬 李軍
摘 要:采場(chǎng)支承壓力分布規(guī)律與峰值位置,對(duì)采場(chǎng)巷道超前支護(hù)和來(lái)壓監(jiān)測(cè)預(yù)報(bào)等都具有重要價(jià)值。以張家峁煤礦淺埋薄基巖大采高22201工作面為背景,基于現(xiàn)場(chǎng)實(shí)測(cè),采用UDEC數(shù)值計(jì)算、物理相似模擬、理論分析相結(jié)合的方法,對(duì)淺埋大采高工作面超前支承壓力峰值演化規(guī)律進(jìn)行了研究。結(jié)果表明:在埋深95 m,采高3~7 m條件下,工作面超前支承壓力峰值隨采高的增大而減小,峰值位置向煤壁深處轉(zhuǎn)移。初采階段,隨著采高增大支承壓力峰值下降了5%,峰值距煤壁距離增大了92%,但與采高之比下降18%。充分采動(dòng)后,隨采高增大支承壓力峰值下降了14%,峰值位置距煤壁距離上升14%,支承壓力峰值和峰值距煤壁距離都大于初采階段。通過(guò)工作面煤巖體極限平衡理論分析,給出了支承壓力峰值位置計(jì)算公式,超前支承壓力峰值位置與采高呈近似線性關(guān)系,理論計(jì)算與實(shí)驗(yàn)和實(shí)測(cè)吻合。
關(guān)鍵詞:淺埋煤層;大采高;超前支承壓力;壓力峰值
中圖分類號(hào):TD 324
文獻(xiàn)標(biāo)志碼:A
文章編號(hào):1672-9315(2021)01-0001-07
DOI:10.13800/j.cnki.xakjdxxb.2021.0101
Evolution law of the peak of front abutment pressure of large
mining height working face in shallow buried
HUANG Qingxiang1,2,LI Feng1,2,HE Yanpeng1,2,GAO Bin3,LI Jun3
(1.College of Energy Science and Engineering,Xian University of Science and Technology,Xian 710054,China;
2.Key Laboratory of Western Mine Exploitation and Hazard Prevention,Ministry of Education,
Xian University of Science and Technology,Xian 710054,China;
3.Shenmu Zhangjiamao Mining Co.,Ltd., of Shaaxi Coal Group,Yulin 719000,China)
Abstract:The distribution law and peak position of stope abutment pressure have important application value for production practices such as advancing support of stope roadway and weighting forecasts.Taking the 22201 working face with the large mining height in shallow buried thin bedrock of Zhangjiamao Coal Mine as a background,a study has been made of? the evolution law the peak front abutment pressure based on field measurement combined methods including UDEC numerical calculation, physical simulation and theoretical analysis. The results show that the peak of front abutment pressure decreases with increasing of mining height, and peak pressure position shifts to the depth of the working face, under conditions of buried depth 95 m and mining height 3~7 m. At the initial mining stage, as the mining height increases, the peak of abutment is pressured decrease by 5%, the distance between peak position and coal wall are increased by 92%, but the ratio of peak to mining height is decreased by 18%. After critical mining, the peak abutment pressure decreases by 14% as the mining height increases, and the distance from the peak position and the coal wall increases by 14%. The distance between peak pressure and coal wall is greater than that at? the initial mining stage. The peak pressure and the distance between the peak and the coal wall are both greater than that at the initial mining stage as mining height increases. Based on theoretical analysis of limit equilibrium of coal and rock mass in working face, calculation formula for peak of frout abutment pressure was given in an linear relationship with the mining height, and theoretical calculations agree with experimental and measured results.
Key words:shallow buried coal seam;large mining height;front abutment pressure;peak pressure
0 引 言
中國(guó)西部榆神府礦區(qū)主采煤層為2-2、5-2兩層厚煤層,2-2煤層平均厚度6.5 m,該煤層埋藏淺、基巖薄、覆蓋厚松散層,適合大采高一次采全高[1-3]。淺埋大采高開(kāi)采,頂板破斷直接波及地表,來(lái)壓期間有明顯的頂板臺(tái)階下沉和動(dòng)載現(xiàn)象[4-7]。工作面超前支承壓力是頂板破斷運(yùn)動(dòng)后煤壁前方原巖應(yīng)力重新分布的結(jié)果[7]。研究淺埋大采高工作面超前支承壓力規(guī)律,是揭示頂板超前破斷規(guī)律和結(jié)構(gòu)形成過(guò)程、確定超前支護(hù)范圍和回撤通道保護(hù)煤柱尺寸以及開(kāi)展來(lái)壓監(jiān)測(cè)預(yù)報(bào)的基礎(chǔ),對(duì)安全高效開(kāi)采具有重要意義。
國(guó)內(nèi)外對(duì)常規(guī)埋深工作面超前支承壓力規(guī)律開(kāi)展了大量研究[8-10],得出超前支承壓力分布規(guī)律和開(kāi)采深度關(guān)系不大[11-13],主要取決與采高和頂板巖性;采高越大,峰值距離煤壁越遠(yuǎn)(平均為1.27倍采高),峰值系數(shù)基本不變[14-15]。關(guān)于淺埋煤層超前支承壓力研究,任艷芳等認(rèn)為淺埋工作面超前支承壓力分布規(guī)律與常規(guī)埋深類似[16];黃慶享等發(fā)現(xiàn)陜北淺埋大采高工作面超前支承壓力峰值隨采高的增大降低,峰值位置與煤壁距離約為采高的2倍[17];秦忠誠(chéng)等研究得出東勝轉(zhuǎn)龍灣煤礦淺埋工作面末采階段超前支承壓力影響范圍約為20 m,據(jù)此優(yōu)化了回撤通道間保護(hù)煤柱尺寸[18];王創(chuàng)業(yè)等預(yù)測(cè)了淺埋大采高工作面支承壓力峰值點(diǎn)位置[19]。可見(jiàn),超前支承壓力是巖層控制關(guān)注的熱點(diǎn),而關(guān)于淺埋大采高工作面超前支承壓力規(guī)律的研究較少。
以神南礦區(qū)張家峁煤礦22201淺埋薄基巖大采高工作面為對(duì)象,在采場(chǎng)頂板破斷規(guī)律和來(lái)壓規(guī)律實(shí)測(cè)基礎(chǔ)上,利用UDEC數(shù)值計(jì)算和物理模擬,分析3~7 m采高時(shí)的工作面超前支承壓力峰值演化特征與規(guī)律,給出了超前支承壓力峰值位置的計(jì)算公式,得到了現(xiàn)場(chǎng)實(shí)測(cè)結(jié)果的驗(yàn)證。本文研究為確定頂板超前破斷位置與支承壓力峰值的關(guān)系,揭示頂板結(jié)構(gòu)運(yùn)動(dòng)與壓力轉(zhuǎn)移的關(guān)系,提供了重要依據(jù);還可為工作面巷道超前支護(hù)范圍確定、末采回撤通道煤柱初次優(yōu)化、超前來(lái)壓監(jiān)測(cè)預(yù)報(bào)等提供重要的科學(xué)依據(jù)。
1 工程背景
張家峁煤礦22201工作面為2-2煤層首采工作面,地表地形地貌屬風(fēng)沙灘地區(qū),煤層賦存穩(wěn)定,傾角1°~2°,煤層厚度7.3~9.6 m,采高6 m,平均埋深約95 m。頂板中完整基巖厚度約16~20 m,風(fēng)化基巖厚度約16~20 m,松散層厚度約40~50 m,工作面屬于典型的淺埋薄基巖大采高工作面[1]。工作面綜合柱狀圖如圖1所示。
2 變采高超前支承壓力演化機(jī)理
2.1 計(jì)算模型
以張家峁煤礦淺埋薄基巖大采高22201工作面為背景,建立UDEC數(shù)值計(jì)算模型(圖2)。模型長(zhǎng)×高=300 m×95 m,模擬采高3~7 m。模型頂部為自由邊界,底部邊界限制垂直位移,兩側(cè)水平方向施加位移約束。模型材料本構(gòu)關(guān)系選取摩爾—庫(kù)倫,節(jié)理本構(gòu)關(guān)系選取面接觸的庫(kù)倫滑移,煤巖力學(xué)參數(shù)見(jiàn)表1。
模型左右邊界各留50 m邊界煤柱消除邊界效應(yīng),模擬工作面沿走向開(kāi)采200 m。開(kāi)挖過(guò)程中,在煤層底板布設(shè)應(yīng)力測(cè)線,計(jì)算出工作面開(kāi)挖過(guò)程中超前支承壓力,分析淺埋大采高工作面超前支承壓力峰值演化規(guī)律。
2.2 超前支承壓力演化特征
在開(kāi)采條件一定的情況下,計(jì)算3,4,5,6和7 m采高的工作面超前支承壓力。
初采階段工作面超前支承壓力分布如圖3所示。隨著采高的增大支承壓力峰值減小不大,峰值點(diǎn)距煤壁距離增加,影響范圍約20 m。
充分采動(dòng)后不同采高工作面超前支承壓力分布曲線如圖4所示,充分采動(dòng)后工作面超前支承壓力峰值隨著采高的增大而減小,壓力峰值向煤壁深處轉(zhuǎn)移,支承壓力影響范圍約25 m,比初采階段影響范圍增大25%。
充分采動(dòng)后,隨著采高的增大,支承壓力峰值數(shù)值和位置都大于初采階段。
初采和充分采階段的工作面超前支承壓力峰值和峰值位置隨采高的演化規(guī)律如圖5所示。初采階段,隨采高3 m增大到7 m,峰值系數(shù)(峰值與原巖應(yīng)力比)由1.92下降為1.83,下降5%。峰值位置距煤壁距離從4.9 m增大為9.4 m,絕對(duì)值增加了92%;與采高比從1.63倍降為1.34倍,與采高比降低18%。
充分采動(dòng)后,隨著采高由3 m增大到7 m,支承壓力峰值從原巖應(yīng)力的2.20倍下降為1.94倍,減小14%;峰值位置從4.8 m增大為12.8 m,絕對(duì)值增加了167%;與采高比從1.60倍上升為1.83倍,與采高比增加了14%。
初采階段和充分采動(dòng)階段,壓力峰值與采高成近似線性關(guān)系。峰值位置卻出現(xiàn)分化,初采階段峰值距離煤壁與采高的倍數(shù)呈非線性降低趨勢(shì),充分采動(dòng)后呈非線性增加趨勢(shì)。支承壓力峰值大小及距煤壁的距離與采高關(guān)系如下
(2)
式中 m為采高,m;σymax為支承壓力峰值,MPa;σz為原巖應(yīng)力,MPa;x0為峰值距煤壁距離,m。
3 6 m大采高超前支承壓力分布規(guī)律
以張家峁煤礦22201工作面條件,按照幾何相似比αl=100制作物理相似模型,模型長(zhǎng)×寬×高=3 m×0.2 m×0.95 m,容重相似比αγ=1.5,應(yīng)力相似比ασ=50,模擬采高6 m。在模型底板上布置
CL-YB-114WX1無(wú)線測(cè)力傳感器監(jiān)測(cè)工作面開(kāi)采過(guò)程煤壁超前支承壓力。
模擬工作面推進(jìn)到33 m,頂板初次垮落,高度15 m,工作面初次來(lái)壓,老頂形成“非對(duì)稱三角拱”
結(jié)構(gòu),如圖6所示。
工作面初次來(lái)壓時(shí),超前支承壓力分布如圖7所示,物理模擬壓力峰值2.98 MPa,
超前煤壁8.5 m,為采高的1.42倍。數(shù)值計(jì)算壓力峰值3.05 MPa,超前煤壁8.5 m,為采高的1.42倍。兩者基本一致,后面采用數(shù)值模擬結(jié)果表述。
工作面第1次周期來(lái)壓覆巖垮落形態(tài)如圖8所示。來(lái)壓步距12 m,煤層頂板上方20~35 m層位的老頂關(guān)鍵層破斷,覆巖裂隙帶發(fā)育高度35 m,巖層破斷角約64°。
第1次周期來(lái)壓時(shí)工作面超前支承壓力分布曲線如圖9所示。來(lái)壓時(shí),支承壓力峰值3.1 MPa,峰值超前工作面煤壁前方9 m,為采高的1.50倍,支承壓力影響范圍25 m。
工作面推進(jìn)到75 m時(shí),工作面達(dá)到充分采動(dòng),覆巖垮落形態(tài)如圖10所示。頂板在煤壁前方約7 m位置出現(xiàn)超前破斷,形成臺(tái)階巖梁結(jié)構(gòu)。
充分采動(dòng)后的周期來(lái)壓期間,超前支承壓力規(guī)律變化不大,如圖11所示。壓力峰值3.1 MPa,峰值距煤壁平均9.4 m,為采高的1.57倍。
據(jù)物理模擬和數(shù)值計(jì)算,張家峁煤礦22201工作面在6.0 m采高條件下,工作面超前支承壓力峰值為原巖應(yīng)力的1.84倍(初采)~1.87倍(充分采動(dòng)),峰值位置距工作面煤壁的距離為采高的1.42倍(初采)~1.57倍(充分采動(dòng))。
4 超前支承壓力峰值位置理論分析
4.1 超前峰值位置的確定
根據(jù)工作面超前煤體受力特征,可分為3個(gè)區(qū)(圖12),松弛區(qū)內(nèi)煤體出現(xiàn)松動(dòng),承載能力下降,應(yīng)力低于原巖應(yīng)力;塑性承載區(qū)的煤體具有一定承載能力,應(yīng)力高于原巖應(yīng)力;彈性區(qū)包括應(yīng)力增高區(qū)和原巖應(yīng)力區(qū)。
假設(shè)煤層是均質(zhì)連續(xù)的各向同性體,在埋深H處,任意取一單元體煤,單元體煤上所受的垂直應(yīng)力σz為原巖應(yīng)力[7],即
(3)
式中 γ為覆巖體積力,kN/m3;H為埋深,m。
22201工作面埋深95 m,原巖應(yīng)力1.65 MPa。
煤體的承載能力隨著遠(yuǎn)離煤壁邊緣而增大,在距離煤壁邊緣一定距離內(nèi),存在煤體承載能力與支承壓力的極限平衡狀態(tài),采用煤巖體極限平衡理論,得出極限平衡區(qū)內(nèi)的支承壓力σy[20-21]
(4)
令工作面超前支承壓力峰值σymax=KγH,K為峰值(應(yīng)力集中)系數(shù),壓力峰值距工作面煤壁水平距離x0為[21]
(5)
式中 m為采高,m;f為煤層與頂板接觸面的摩擦因數(shù);α為煤體內(nèi)摩擦角,(°);τcotα為煤體自撐力,MPa。
據(jù)式(5),在內(nèi)摩擦角α和摩擦因數(shù)f為定值情況下,x0隨著采高m的增大而增大,峰值位置x0與采高m近似成線性關(guān)系。
4.2 現(xiàn)場(chǎng)驗(yàn)證
以22201工作面為例,按照表2計(jì)算參數(shù),計(jì)算得出工作面超前支承壓力峰值距煤壁距離9.5 m,為采高1.6倍,理論計(jì)算與數(shù)值分析和物理模擬結(jié)果吻合。
根據(jù)張家峁煤礦22201工作面回風(fēng)順槽和運(yùn)輸順槽超前支架壓力變化規(guī)律,工作面兩順槽超前支承壓力峰值距工作面煤壁8~10 m,為采高的1.5~1.7倍,影響范圍20 m左右。
實(shí)測(cè)結(jié)果與數(shù)值分析、物理模擬、理論計(jì)算結(jié)果一致,表明上述研究結(jié)果可靠。
5 結(jié) 論
1)工作面超前支承壓力峰值隨采高增大而減小,峰值向煤壁深處轉(zhuǎn)移。采高由3 m增大到7 m時(shí),初采階段支承壓力峰值由原巖應(yīng)力的1.92倍下降為1.83倍,下降了5%;峰值距煤壁距離增大了92%,但與采高之比由1.63下降為1.34,下降了18%。
2)充分采動(dòng)后,支承壓力峰值由原巖應(yīng)力的2.20倍下降為1.94倍,下降了14%;峰值距煤壁距離由采高的1.60倍上升為1.83倍,上升了14%。充分采動(dòng)后,隨采高的增大,支承壓力峰值和峰值距煤壁距離都大于初采階段。
3)通過(guò)工作面煤巖體極限平衡理論分析,給出了支承壓力峰值位置計(jì)算公式,超前支承壓力峰值位置與采高呈近似線性關(guān)系,理論計(jì)算與實(shí)驗(yàn)和實(shí)測(cè)吻合。
參考文獻(xiàn)(References):
[1] 黃慶享.淺埋煤層的礦壓特征與淺埋煤層定義[J].巖石力學(xué)與工程學(xué)報(bào),2002,21(8):1174-1177.HUANG Qingxiang.Ground pressure behavior and definition of shallow seams[J].Chinese Journal of Rock Mechanics and Engineering,2002,21(8):1174-1177.
[2]王雙明,黃慶享,范立民,等.生態(tài)脆弱礦區(qū)含(隔)水層特征及保水開(kāi)采分區(qū)研究[J].煤炭學(xué)報(bào),2010,35(1):7-14.WANG Shuangming,HUANG Qingxiang,F(xiàn)AN Limin,et al.Study on overburden aquclude and water protection mining regionalization in the ecological fragile mining area[J].Journal of China Coal Society,2010,35(1):7-14.
[3]孟憲瑞,王鴻鵬,劉朝暉,等.我國(guó)厚煤層開(kāi)采方法的選擇原則與發(fā)展現(xiàn)狀[J].煤炭科學(xué)技術(shù),2009,37(1):39-44.MENG Xianrui,WANG Hongpeng,LIU Chaohui,et al.Selection principle and development status of thick seam mining methods in China[J].Coal Science and Technoloy,2009,37(1):39-44.
[4]黃慶享.淺埋煤層長(zhǎng)壁開(kāi)采頂結(jié)構(gòu)及巖層控制研究[M].徐州:中國(guó)礦業(yè)大學(xué)出版社,2000.
[5]黃慶享,賀雁鵬,李鋒,等.淺埋薄基巖大采高工作面頂板破斷特征和來(lái)壓規(guī)律[J].西安科技大學(xué)學(xué)報(bào),2019,39(5):737-744.HUANG Qingxiang,HE Yanpeng,LI Feng, et al. Site measurement on roof fracture and weighting feature in large mining height face in shallowly-buried thin bedrock coal mining[J].Journal of Xian University of Science and Technology,2019,39(5):737-744.
[6]HUANG Q X, HE Y P. Research on overburden movement characteristics of large mining height working face in shallow buried thin bedrock[J].Energies,2019,4208:1-16.
[7]錢(qián)鳴高,石平五,許家林.礦山壓力與巖層控制[M].徐州:中國(guó)礦業(yè)大學(xué)出版社,2010.
[8]姜福興,馬其華.深部長(zhǎng)壁工作面動(dòng)態(tài)支承壓力極值點(diǎn)的求解[J].煤炭學(xué)報(bào),2002,27(3):273-275.JIANG Fuxing,MA Qihua.Mechanical solution of the maximum point of dynamic abutment pressure under deep long-wall working face[J].Journal of China Coal Society,2002,27(3):273-275.
[9]金珠鵬,秦濤,張俊文.深部大采高工作面支承壓力分布特征及影響因素分析[J].煤炭科學(xué)技術(shù),2018,46(S1):97-99,134.JIN Zhupeng,QIN Tao,ZHANG Junwen.Analysis of abutment pressure distribution characteristics and influencing factors of deep mining height face[J].Coal Science and Technology,2018,46(S1):97-99,134.
[10]王鈺博.特厚煤層綜放工作面端部結(jié)構(gòu)及側(cè)向支承壓力演化機(jī)理[J].煤炭學(xué)報(bào),2017,42(S1):30-35.WANG Yubo.Evolution mechanism of end structure and abutment pressure on fully-mechanized top coal caving face in extra thick coal seam[J].Journal of China Coal Society,2017,42(S1):30-35.
[11]謝廣祥,楊科,常聚才.不同采厚圍巖力學(xué)特征的相似模擬實(shí)驗(yàn)研究[J].煤炭學(xué)報(bào),2009,34(11): 1146-1450.XIE Guangxiang,YANG Ke,CHANG Jucai. Experimental investigation into mechanical chavacteristics of surrounding rock with different mining thicknesses[J].Journal of China Coal Society,2009,34(11): 1146-1450.
[12]夏永學(xué),藍(lán)航,毛德兵,等.基于微震監(jiān)測(cè)的超前支承壓力分布特征研究[J].中國(guó)礦業(yè)大學(xué)學(xué)報(bào),2011,40(6):868-873.XIA Yongxue,LAN Hang,MAO Debing,et al.Study of the lead abutment pressure distribution base on microseismic monitoring[J].Journal of China University of Mining and Technology,2011,40(6):868-873.
[13]劉長(zhǎng)友,黃炳香,孟祥軍,等.超長(zhǎng)孤島綜放工作面支承壓力分布規(guī)律研究[J].巖石力學(xué)與工程學(xué)報(bào),2007,26(S1):2761-2766.LIU Changyou,HUANG Bingxiang,MENG Xiangjun,et al.Research on abutment pressure distribution law of overlength isolated fully-mechanized top coal caving face[J].Chinese Journal of Rock Mechanics and Engineering,2007,26(S1):2761-2766.
[14]謝廣祥,王磊.工作面支承壓力采厚效應(yīng)解析[J].煤炭學(xué)報(bào),2008,33(4): 361-363.XIE Guangxiang,WANG Lei.Effect of mining thickness on abutment pressure of working face[J].Journal of China Coal Society,2008,33(4): 361-363.
[15]司榮軍,王春秋,譚云亮.采場(chǎng)支承壓力分布規(guī)律的數(shù)值模擬研究[J].巖土力學(xué),2007,28(2) :351-354.SI Rongjun,WANG Chunqiu,TAN Yunliang.Numerical simulation of abutment pressure distribution law of working faces[J].Rock andSoil Mechanics,2007,28(2) :351-354.
[16]任艷芳,寧宇.淺埋煤層長(zhǎng)壁開(kāi)采超前支承壓力變化特征[J].煤炭學(xué)報(bào),2014,39(S1):38-42.
REN Yanfang,NING Yu.Changing features of advancing abutment pressure in shallow long wall working face[J].Journal of China Coal Society,2014,39(S1):38-42.
[17]黃慶享,周金龍.淺埋煤層大采高工作面礦壓規(guī)律及頂板結(jié)構(gòu)研究[J].煤炭學(xué)報(bào),2016,41(S2):279-286.HUANG Qingxiang,ZHOU Jinlong.Roof weighting behavior and roof structure of large mining height longwall face in shallow coal seam[J].Journal of China Coal Society,2016,41(S2):279-286.
[18]秦忠誠(chéng),張望寶,王九利.淺埋煤層綜采面超前支承壓力影響范圍與末采讓壓技術(shù)研究[J].煤炭工程,2016,48(12):53-55.QIN Zhongcheng,ZHANG Wangbao,WANG Jiuli.Study on influence scope of advance abutment pressure and technology of yield end-mining for fully-mechanized working face in shallow seam[J].Coal Engineering,2016,48(12):53-55.
[19]王創(chuàng)業(yè),司建鋒,梁博帥,等.大采高工作面超前支承壓力分布規(guī)律研究[J].煤炭技術(shù),2016,35(11):19-21.WANG Chuangye,SI Jianfeng,LIANG Boshuai,et al.Study on distribution law of advanced abutment pressure of large mining height workface[J].Coal Technology,2016,35(11):19-21.
[20]熊仁欽.關(guān)于煤壁內(nèi)塑性區(qū)寬度的討論[J].煤炭學(xué)報(bào),1989,3(1):16-22.XIONG Renqin.Discussion on width of plastic zone in coal rib[J].Journal of China Coal Society,1989,3(1):16-22.
[21]靳鐘銘,魏錦平,靳文學(xué).放頂煤采場(chǎng)前支承應(yīng)力分布特征[J].太原理工大學(xué)學(xué)報(bào),2001,32(3):216-218.JIN Zhongming,WEI Jinping,JIN Wenxue. Distributive characteristic of front abutment pressure in top-coal caving face[J].Journal of Taiyuan University of Technology,2001,32(3):216-218.
收稿日期:2020-08-06?? 責(zé)任編輯:劉 潔
基金項(xiàng)目:
國(guó)家自然科學(xué)基金項(xiàng)目(51674190,52074211);陜西省自然科學(xué)基礎(chǔ)研究計(jì)劃-陜煤聯(lián)合基金(2019JLP-08);西安科技大學(xué)優(yōu)秀博士論文培育計(jì)劃項(xiàng)目(PY19001)
通信作者:黃慶享,男,新疆沙灣人,博士,教授,博士生導(dǎo)師,E-mail:361923187@qq.com