趙萌燁 黃慶享 黃克軍
摘 要:為了掌握無(wú)煤柱切頂留巷的礦壓顯現(xiàn)規(guī)律并檢驗(yàn)巷道支護(hù)效果,以澄合礦區(qū)董東煤礦50107工作面為研究對(duì)象,采用現(xiàn)場(chǎng)監(jiān)測(cè)的手段對(duì)無(wú)煤柱切頂沿空留巷受采動(dòng)影響條件下的頂板下沉規(guī)律、幫部變形規(guī)律及單體支柱受力變化規(guī)律進(jìn)行了實(shí)測(cè),并同時(shí)對(duì)切頂效果、擋矸效果及巷道穩(wěn)定性進(jìn)行了分析與評(píng)價(jià)。結(jié)果表明,巷道礦壓隨工作面的臨近而逐漸增大,采動(dòng)過(guò)程中靠近采空區(qū)側(cè)的巷道礦壓顯現(xiàn)程度更為劇烈,表現(xiàn)出明顯的非對(duì)稱(chēng)性特征,巷道頂板的回轉(zhuǎn)運(yùn)動(dòng)是造成巷道非對(duì)稱(chēng)礦壓顯現(xiàn)的主要原因。此外,無(wú)煤柱切頂沿空留巷階段性變化特征明顯,初始變化階段位于工作面后方0~35 m;快速變形階段位于工作面后方35~75 m;緩慢變形階段位于工作面后75 m以外,巷道變形及支柱受力均達(dá)到穩(wěn)定狀態(tài)。巷道礦壓顯現(xiàn)的主要過(guò)程集中在快速變形階段,需加強(qiáng)對(duì)巷道圍巖的控制。實(shí)踐表明,無(wú)煤柱切頂沿空留巷采用錨網(wǎng)配合單體支柱的支護(hù)方式可行。
關(guān)鍵詞:無(wú)煤柱開(kāi)采;切頂沿空留巷;礦壓顯現(xiàn)規(guī)律;巷道變形;巷道支護(hù)
中圖分類(lèi)號(hào):TD 823 ? 文獻(xiàn)標(biāo)志碼:A
DOI:10.13800/j.cnki.xakjdxxb.2019.0406 ? 文章編號(hào):1672-9315(2019)04-0597-06
Abstract:To explore the pressure behavior and to test the supporting effect of gob-side entry retaining with roof cutting and non-pillar mining, a variety of on-site monitoring techniques are used to test the law of roof subsidence, rib deformation and stress of the single prop with the working face 50107 from Dongdong coal mine in Chenghe mining area as the subject, a variety of analysis and an evaluation have been made of the effects of roof cutting and tamping as well as roadway stability in this paper. The research results show that the pressure of roadway gradually increases with the approaching of the working face. Meanwhile, the pressure in the roadway near the side of the goaf is more intense during the mining process with significant asymmetry demonstrated. The rotation of the roof is the main reason for the apparent mine pressure of the roadway. In addition, the changes are obvious in different stages of the pressure of the coal roadway. The initial change stage is located at 0~35 m behind the working face.Rapid deformation mainly occurs 35~75 m behind the working face; Slow deformation stage is located at 75 m behind the working surface, the roadway is rapidly reduced and tends to be stable. The main process of roadway pressure is concentrated at the stage of rapid deformation, and it is necessary to strengthen the control of surrounding rock of roadway. Practice has proved the feasibility of the anchor net and the support of the single props in the roof.
Key words:non pillar mining;roof cutting at gob side entry retaining;mine pressure behavior;roadway deformation;roadway support
0 引 言
無(wú)煤柱切頂沿空留巷是一項(xiàng)高效的采煤新技術(shù)[1-2],能夠緩解開(kāi)采效率低、生產(chǎn)成本高的問(wèn)題。該技術(shù)一方面省去一條回采巷道,減少了巷道開(kāi)拓量;另一方面,開(kāi)采過(guò)程中取消了區(qū)段煤柱,采空區(qū)直接與巷道相連,減少了資源的浪費(fèi),提高了回采率;此外,無(wú)煤柱開(kāi)采方式對(duì)解除了煤柱集中應(yīng)力,有利于減小下部煤層開(kāi)采過(guò)程中的應(yīng)力集中程度。
無(wú)煤柱切頂沿空留巷礦壓顯現(xiàn)規(guī)律受切頂工藝影響[3],巷道變形及受力表現(xiàn)出明顯的非對(duì)稱(chēng)性、階段性及持續(xù)性。無(wú)煤柱切頂沿空留巷技術(shù)在傳統(tǒng)沿空留巷基礎(chǔ)上發(fā)展而來(lái),劉聽(tīng)成等最早研究了沿空留巷技術(shù)[4-5],提出沿空留巷先后受上下2個(gè)工作面的采動(dòng)影響,服務(wù)時(shí)間長(zhǎng),總變形量大。華心祝等[6-8]建立了沿空留巷力學(xué)模型和巷旁充填支護(hù)技術(shù)。柏建彪、侯朝炯等給出了沿空留巷充填體參數(shù)選擇依據(jù),同時(shí)提出了沿空留巷圍巖控制方法[9-11]。何滿潮院士提出了“切頂短壁梁”理論[12]和切頂卸壓自動(dòng)成巷技術(shù)[13-14]。目前,國(guó)內(nèi)對(duì)切頂留巷的礦壓實(shí)測(cè)研究不多,掌握無(wú)煤柱切頂留巷的礦壓規(guī)律,對(duì)巷道支護(hù)研究具有重要的意義。
通過(guò)對(duì)巷道頂板下沉量、巷幫水平變形量及單體支柱受力進(jìn)行實(shí)測(cè),掌握澄合礦區(qū)董東煤礦50107工作面無(wú)煤柱切頂留巷礦壓規(guī)律,為無(wú)煤柱切頂沿空留巷支護(hù)設(shè)計(jì)提供了科學(xué)依據(jù)。
1 巷道基本條件
1.1 工作面條件
董東礦50107工作面煤層傾角3°~6°,工作面寬度117 m,走向長(zhǎng)度為224 m.工作面開(kāi)采5#煤層,采高3.4 m,直接頂厚度2 m左右,巖性為砂質(zhì)泥巖和炭質(zhì)泥巖?;卷敽穸燃s8 m,巖性為粉砂巖。
1.2 巷道支護(hù)方式
50107工作面回采巷道寬度4.6 m,高度3.4 m。巷道頂部采用長(zhǎng)度2.8 m的無(wú)縱助左螺紋鋼錨桿,直徑為20 mm,間排距為700 mm×600 mm;錨索長(zhǎng)度8.3 m,直徑為21.8 mm,間距600 mm.采煤側(cè)幫部采用直徑20 mm,長(zhǎng)度2.4 m的左螺紋鋼錨桿,間排距為700 mm×600 mm.非采空側(cè)幫部,采用直徑22 mm,長(zhǎng)度300 mm的右旋等強(qiáng)螺紋鋼,間排距700 mm×600 mm,錨桿托盤(pán)采用螺形托盤(pán),尺寸為150 mm×150 mm.巷旁支護(hù)采用擋矸柱和單體柱聯(lián)合支護(hù)的方式,擋矸柱通過(guò)錨網(wǎng)相互連接,每隔600 mm設(shè)置一根,單體柱的間排距為300 mm×300 mm,如圖1所示。
1.3 切頂留巷參數(shù)
超前切頂?shù)墓に嚰靶Ч菬o(wú)煤柱切頂沿空留巷成功與否的關(guān)鍵,董東煤礦50107工作面采用打孔定向爆破的方式進(jìn)行超前切頂作業(yè),垂直孔深7 400 mm,傾角20°,具體參數(shù)見(jiàn)表1.
2 巷道礦壓顯現(xiàn)規(guī)律
2.1 監(jiān)測(cè)方案
巷道測(cè)站布置如圖2所示,測(cè)站斷面布置方式如圖3所示,AB為兩幫移近測(cè)線,CD和EF為頂?shù)滓平鼫y(cè)線,①②③為巷旁單體支柱受力測(cè)點(diǎn)。
2.2 巷道變形規(guī)律
2.2.1 頂板下沉規(guī)律
實(shí)測(cè)切頂沿空留巷測(cè)站頂板下沉曲線,如圖4所示。有如下規(guī)律。
1)巷道頂板的非對(duì)稱(chēng)下沉說(shuō)明了巷道頂板的回轉(zhuǎn)現(xiàn)象[13-14]。采空區(qū)側(cè)巷道頂板下沉量平均在330 mm左右,巷道中部頂板下沉量平均為250 mm.采空區(qū)側(cè)巷道頂板下沉量比巷道中部位置大將近32%.董東煤礦未采用切頂巷道的頂板平均下沉量達(dá)400 mm;
2)工作面后方0~35 m,巷道頂板未發(fā)生明顯下沉;35~50 m巷道頂板下沉量最大,是下沉的主要區(qū)域;50~75 m頂板下沉量減小,工作面后方75 m,頂板趨于穩(wěn)定。前期變形主要受老頂回轉(zhuǎn)運(yùn)動(dòng)的影響,大約為2~3個(gè)周期來(lái)壓步距(17 m);后期變形主要是采空區(qū)破碎巖體壓實(shí)引起的頂板緩慢沉降[15];
3)無(wú)煤柱切頂巷道受采動(dòng)影響存在“影響范圍大、穩(wěn)定時(shí)間長(zhǎng)”的變形特點(diǎn)。較傳統(tǒng)沿空留巷而言,切頂卸壓作用降低了頂板應(yīng)力的傳遞,巷道變形存在一定的滯后。
2.2.2 巷幫變形規(guī)律
實(shí)測(cè)無(wú)煤柱切頂沿空留巷煤壁側(cè)幫如圖7(a)所示,采空區(qū)側(cè)人工幫變形曲線如圖5(b)所示。
煤壁側(cè)巷幫變形集中于巷幫中部,水平變形量平均350 mm.采空區(qū)側(cè)巷幫水平變形量(指支護(hù)網(wǎng)向巷道內(nèi)的擠進(jìn)量)平均672 mm.采空區(qū)側(cè)的幫部擠進(jìn)量為煤壁側(cè)的水平變形量的1.9倍。幫部水平變形分為3個(gè)階段。
1)初始變形階段:位于工作面后方0~35 m,約2倍周期來(lái)壓步距內(nèi),處于工作面端頭弧三角板保護(hù)區(qū),巷幫水平變形量較小;
2)快速變形階段:位于工作面后方35~50 m,約2~3倍周期來(lái)壓步距(平均17 m),處于頂板結(jié)構(gòu)回轉(zhuǎn)運(yùn)動(dòng)區(qū)。本階段巷幫水平變形量占總變形量的70%以上。采空區(qū)頂板回轉(zhuǎn)運(yùn)動(dòng),導(dǎo)致巷幫變形具有非對(duì)稱(chēng)性;
3)緩慢變形階段:位于工作面后方50~75 m以外,大于3倍周期來(lái)壓步距,進(jìn)入采空區(qū)頂板壓實(shí)區(qū),巷幫水平變形緩慢變化,達(dá)到穩(wěn)定狀態(tài)。
2.3 巷道支柱受力
單體支柱受力曲線如圖6所示,其中1號(hào)支柱緊靠近采空區(qū)一側(cè),2號(hào)支柱居中,距離采空區(qū)1 m,3號(hào)支柱距離采空區(qū)1.8 m.
1)靠近采空區(qū)一側(cè)的1號(hào)支柱平均載荷24.3 MPa,比靠巷幫3號(hào)支柱載荷大20%.支柱的平均初始載荷7.1 MPa,穩(wěn)定載荷22.1 MPa,平均變化量達(dá)到15 MPa;
2)單體支柱所受載荷經(jīng)歷“增大-減小-穩(wěn)定”的動(dòng)態(tài)變化過(guò)程[16-17],支柱受力增大的區(qū)域主要集中在工作面后方20 m范圍內(nèi);工作面后方20~30 m經(jīng)歷明顯的卸壓過(guò)程,隨后受力繼續(xù)增大;工作面后方75 m單體支柱受力達(dá)到穩(wěn)定,采空區(qū)一側(cè)單體穩(wěn)定受力在25 MPa左右,巷道中部穩(wěn)定受力在20 MPa.
3 無(wú)煤柱切頂沿空留效果
3.1 切頂效果
現(xiàn)場(chǎng)使用鉆孔窺視儀觀察切頂效果,如圖7所示,在孔口處可看出切頂孔之間的裂隙明顯發(fā)育。巷外切頂效果是留巷的關(guān)鍵,50107工作面巷切頂有效切斷了頂板的應(yīng)力聯(lián)系,減小了沿空留巷的礦壓顯現(xiàn)程度。
3.2 巷道穩(wěn)定性
根據(jù)現(xiàn)場(chǎng)觀測(cè),已切頂?shù)词懿蓜?dòng)影響的超前巷道表現(xiàn)出較好的穩(wěn)定性。巷道未進(jìn)行超前支護(hù),也未發(fā)生明顯變形,如圖8所示。
當(dāng)巷道處于工作面后方時(shí),由于巷道一側(cè)已采空,頂板發(fā)生向相鄰采空區(qū)一側(cè)的下沉,靠近采空區(qū)一側(cè)下沉量較大,但巷道整體變形量允許范圍之內(nèi),巷道穩(wěn)定且可足以滿足生產(chǎn)要求,支護(hù)效果如圖8所示。
3.3 巷旁擋矸效果
切頂留巷下巷旁擋矸支護(hù)效果的關(guān)鍵是沿空一側(cè)巷旁支護(hù)體的材料和性能的選擇[18-20]。巷旁擋矸支護(hù)體設(shè)置后應(yīng)能夠快速增阻,支護(hù)頂板保持頂板自承能力,在工作面后方周期來(lái)壓前達(dá)到切頂阻力切落采空區(qū)一定高度的頂板[21-22];上覆巖層劇烈活動(dòng)穩(wěn)定前有較大的變形能力,支護(hù)提還要具有足夠的可縮性,適應(yīng)頂板回轉(zhuǎn)下沉;具有較高的后期強(qiáng)度,保持頂板結(jié)構(gòu)的平衡[23-24]。實(shí)踐表明,無(wú)煤柱切頂留巷采用錨網(wǎng)配合單體支柱與曲線擋矸柱的支護(hù)方式可行,支護(hù)效果如圖9所示。
4 結(jié) 論
1)董東50107工作面切頂留巷,切頂作用有效切斷了巷道頂板應(yīng)力傳遞,降低了巷道整體的礦壓顯現(xiàn)程度。實(shí)踐表明,切頂后頂板垮落效果良好,無(wú)煤柱切頂留巷采用錨網(wǎng)配合單體支柱的支護(hù)方式可行。
2)巷道礦壓顯現(xiàn)表現(xiàn)出一定的非對(duì)稱(chēng)性。采空區(qū)一側(cè)頂板下沉量及單體支柱受力均大于巷道中部,頂板下沉量大出32%,單體支柱受力大近24%,體現(xiàn)了巷道頂板的回轉(zhuǎn)運(yùn)動(dòng)特征。受頂板壓力的作用,采空區(qū)一側(cè)錨網(wǎng)幫的變形量為煤壁側(cè)幫部1.9倍。
3)巷道變形及受力經(jīng)歷初始變化、快速變化及持續(xù)變化階段。初始變化階段位于工作面至后方35 m內(nèi),巷道受弧三角懸頂保護(hù),變形程度低,支柱受力小??焖僮冃坞A段位于工作面后方35~75 m,受頂板回轉(zhuǎn)運(yùn)動(dòng)影響,巷道變形及單體支柱受力均達(dá)到整體值的70%以上。緩慢變形階段位于工作面采動(dòng)75 m后,處于垮落頂板壓實(shí)區(qū),巷道變形緩慢并趨于穩(wěn)定。
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