综放开采顶煤体离层与破坏规律研究

文章编号:1003-5923(2002)02-0006-02

综放开采顶煤体离层与破坏规律研究

贾光胜1,2,毛德兵1

(1.天地科技股份有限公司开采所事业部,北京100013;　2.中国矿业大学北京校区,北京100083)

摘　要:本文分析了节理裂隙对综放开采顶煤破坏破碎的影响,通过现场观测,研究了综放工作面支架上方顶煤体的离层及破坏情况,得到综放开采顶煤体在离煤壁不同的距离、不同高度上离层及破坏分布规律。

关键词:综放开采;离层;破坏规律中图分类号:TD 823.9 文献标识码:A

综放开采顶煤体在放出前发生离层和强度破坏是进行综放开采的必要条件,而综放面顶煤体在支架上方离层和裂隙发育程度决定着顶煤放出时的流畅性和顶煤的回采率。因此,研究综放开采支架上方顶煤体离层及破坏规律和影响因素,对研究综放开采顶煤冒放性和提高顶煤回采率十分必要。1　节理裂隙对顶煤体破坏破碎的影响

综放面顶煤是在支承压力作用下,使原有节理裂隙扩展并发生新的裂隙,而使煤层发生强度破坏,直至最后破碎的。节理裂隙对顶煤体的破坏破碎影响主要表现在两个方面:一是节理裂隙面的存在降低了顶煤体的强度;二是裂隙影响着顶煤体的完整性。节理裂隙对顶煤体强度的影响与节理裂隙的走向、倾角(即裂隙面相对于作用载荷方向的倾角)、密度、裂缝充填程度和充填材料等有关,就单个裂隙来讲其影响如图1所示。节理裂隙密度的影响如图2所示。

2　综放面支架上方顶煤体离层和破坏情况观测2.1　观测工作面条件

兖州兴隆庄矿2304工作面长136m ,走向长1023m ,煤厚平均8.7m ;煤层倾角2～10°,平均为7.5°;煤层老顶为20.2m 的中砂岩,直接顶为6.6m 的粉砂岩。煤的硬度系数f =2.0～2.3.2.2　观测方法

在工作面中部布置测点,把D G 80-1

型窥视

图1

　单个裂隙对材料强度影响

图2　裂隙密度对材料强度影响

1-与加压方向垂直的切面;2-同加压方向

仪的探头伸入钻孔内,钻孔周围煤体的裂隙分布和张开情况通过探头的摄像镜头显示于窥视仪的显示器上,按顺序上下移动和转动探头,就可以观测到不同位置顶煤的破坏情况。钻孔布置如图3所示,对观测结果的记录方法为:(1)照相;(2)特征人工描述。2.3　观测结果

根据对2304面的顶煤裂隙发育情况的现场素

基金项目:国家自然科学基金重点资助项目(59734090)收稿日期:2001-05-10

作者简介:贾光胜(1962-),男,江苏省沛县人,天地科技股份有限公司开采所事业部高级工程师,1984年毕业于中国矿业大学采矿工

程系,在职博士生,主要从事放顶煤开采回采工艺和矿山压力方面的研究工作。

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图3　观测钻孔布置图

描与拍摄的照片,得到不同高度顶煤体裂隙个数、宽度及方向。

3　顶煤体离层及破坏规律

为研究顶煤体离煤壁不同距离、不同高度的破

坏与离层情况,引入顶煤离层指数和破坏指数两个概念。其中顶煤的离层指数反映顶煤某一高度h i 处顶煤的离层情况,考虑到测量距离时的误差及离层的区域性,以区间(h i -0.1,h i +0.1)m 范围内顶煤近水平裂隙及其裂隙宽度来计算该指数值,其公式为:

exp.P =2N k ×B k 式中　exp .P ——h i 处顶煤的离层指数;

N k ——顶煤在区间内不同位置近水平裂隙

个数;

B k ——顶煤在区间内不同位置近水平裂隙

的宽度。

顶煤破坏指数用以反映顶煤一定高度h i 处顶煤的破坏情况。取顶煤破坏指数计算区间为[h i -0.3,h i +0.3]m ,主要参数为顶煤体的裂隙数(包括水平、倾斜和垂直裂隙),顶煤破坏指数的计算公式为:

exp.F =N

h

×0.3+N i ×0.3+C

式中　exp .F ——顶煤破坏指数;

N h ——近水平裂隙个数;

N i ——倾斜裂隙个数;

C ——常数,当区间内存在近水平及倾斜裂

隙时,这里取C =0.8,否则C =0。

根据以上的计算公式,可以得到离层指数与顶煤高度关系曲线,即exp .P —H 曲线及exp .F —H (顶煤破坏指数与顶煤高度关系)曲线,见图4、图5。

图5中,离煤壁0.5m 处的顶煤在整个高度方向上,离煤层顶板距离愈大,其破坏程度愈大,

顶煤

图4

　顶煤破坏指数与顶煤高度关系

图5　顶煤离层指数与顶煤高度关系曲线

(a )钻孔距煤壁0.5m ; (b )钻孔距煤壁3.05m ; (c )钻孔距煤壁3.85m

上部几乎没有受到破坏;顶煤此时所发生的离层主要集中于支架上方1～2m 范围内,随离煤层顶板距离减小顶煤离层现象不仅减少,而且程度也越来越小。离煤壁3.05m 处的顶煤,在支架的前后柱之间,整个高度方向上,顶煤都受到破坏,但在H 为1.5m 及3～4m 范围内,由于远离支架和顶板作

用,顶煤破坏程度相对较小,

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7?矿山压力与顶板管理　2002.№2　

3.2.2　顶板基点位移速度

顶板基点在煤壁后方的变形速度平均为34 mm m,在煤壁前方的变形速度平均为6.6mm m,前者是后者的5倍,说明顶板在煤壁后方产生加速运动,这一方面使顶板在煤壁前方保持较完整,产生强大的支承压力破煤,在后方加速沉降,有利于顶煤的进一步破碎;另一方面也为顶板的及时冒落、充填采空区空间提供了条件,是理想的放顶煤开采条件。

3.2.3　顶板基点位移量

实测顶板深基点总位移量平均为306mm,其中始动点至煤壁上方平均位移量为104mm,占总位移量的65.57%,煤壁上方至冒落前夕平均位移量为201mm,煤壁前方顶板位移量是煤壁后方位移量的2倍左右。可见,顶板运动主要以煤壁后方断裂沉降产生离层为主,而煤壁前方受支承压力作用引起的水平移动只占总位移量的三分之一,这与顶煤的位移特征相反。

3.2.4　顶板断裂冒落位置

由表2可知, 测站2#孔两个基点分别距煤层底板16.17m、19.76m高度的直接顶内,其冒落时分别位于煤壁后方7.05m、5.85m,在支架切顶线后方1.9～0.7m内垮落; 测站1#孔的三个孔分别距煤层底板17.42m、15.08m的顶板内,另一孔位于煤层顶板上0.3m处的下位直接顶中,三个基点冒落时的位置分别位于煤壁后方9.26m、5.4m、4.41m处,其中靠下方的两个同时冒落,靠上方的滞后垮落。与顶煤冒落位置平均距离相比,顶板滞后顶煤垮落距离平均1.42m。依据顶板深基点冒落位置计算,顶煤上部的2.26m 内的下位直接顶与上部顶煤基本同时冒落,其6～8m的顶板在切顶线后方0.3～4.11m内冒落。可见在煤层顶板上方观测基点控制的12m内的顶板岩层分三次垮落,属分层多次冒落顶板。

4　结　论

(1)受工作面超前支承压力影响,顶煤始动点位置位于煤壁前方平均22.72m,顶板始动点位置位于煤壁前方平均17.83m。顶板运移较顶煤晚,层位高的顶板(煤)始动点距煤壁较近,即层位高的顶板始动较晚。

(2)煤壁前方顶煤顶板运移主要表现为超前支承压力作用下的水平挤压变形,以水平位移为主;控顶距上方顶煤顶板运移主要表现为顶板断裂沉降引起的垂直运动,以垂直位移为主。以煤壁为界,顶煤的运移量煤壁前方明显高于煤壁后方,顶板的运移量煤壁前方明显低于煤壁后方,两者运移特征相反。煤壁前方以顶煤位移为主,煤壁后方以顶板断裂沉降离层为主。

(3)顶煤的位移速度,煤壁前方与煤壁后方大致相同;顶板的位移速度,煤壁后方明显高于前方。顶煤顶板的这种运移规律对顶煤的破碎放出是十分有利的。

(4)顶煤冒落位置平均为4.96m,平均超前支架切顶线0.18m;顶板冒落位置平均为-6.39m,平均滞后支架切顶线1.24m。顶煤呈倒台阶冒落,冒落角为64～73°;顶板冒落具有层位性,属分层多次冒落顶板。

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上位顶煤在顶板作用下发生弯曲旋转并产生张性垂直裂隙而破坏,破坏程度加大。同时,顶煤的弯曲旋转也使顶煤与顶板发生大的离层,顶煤在H为5.7m和4.5m处有较大的exp.P值,同时在整个高度方向中,煤层在不同层位之间有相对滑移,发生离层。

在离煤壁距离3.85m处,顶煤的弯曲程度变大,顶煤上部的张性裂隙进一步发展,其破坏程度也随之变大;在靠近支架上方的顶煤体,由于支架的反复支撑而不断被破坏;然而中部顶煤体由于受支架作用及顶煤弯曲影响小,相对来说其破坏程度亦小。顶煤在整个高度方向上,层位间的离层进一步发展,离层区域变大,在顶煤2m高度附近,离层量最大。

4　结　语

综放开采顶煤体是在上位岩层和支架共同作用下由原生节理裂隙的扩展并产生新裂隙直至发生强度破坏的,节理裂隙的发育程度对顶煤体的破坏破碎影响较大,运用顶煤体离层和破坏指数可准确描述顶煤体的破坏破碎情况。现场观测结果表明,在控顶区范围内,顶煤体离层和破坏是一个逐步发展的过程,在横向上是由煤壁向采空区逐渐增加的过程,在纵向上是由上下向中间逐渐发展的过程,支架上方2～3m范围内顶煤破坏程度相对较小,这也进一步说明了支架对顶煤的作用范围在其上方2m以内。

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?　2002.№2　矿山压力与顶板管理

矿山压力

与顶板管理ENG L ISH ABSTRACTS Research on curves of deter m i n i ng the i n st ability type of broken rock blocks of ma i n roof——HOU Zhong2jie etc.

A cco rding the calculati on m ethod of contact size of broken rock block s of m ain roof in ro tating,it is figured out curves of deter m ining the instability type.R eason of p rocreating erro rs of the tw o curves draw from sliding instability and ro tating instability is demonstrated.It is given the co rrect deter m ining curve of instability type fo r broken rock block s of m ain roof,and the erro rs on the deter m ining curves in fo reti m e literature is rectified.

The drawi ng character istics of the m echan ized sublevel-cav i ng under the little extraction-cav i ng ratio——FAN Ke2gong etc.

A cco rding to the results of the deep2ho le basic po int movem ent and observati on in2sitll,the top coal caving effects and the caving characteristics of i m m ediate roof in m echanized sublevel caving under the little extracti on2 caving rati o are analysed by the paper.T he relati ons of the recovery rate and roof caving characteristics and fragm ent degree of caving coal and rock are recognized.

Study on the separation and the broken law of top-coal i n longwall top-coal cav i ng m i n i ng——J I A Guang2sheng etc.

T he paper analyses the influence of crack s on the break ing of top2coal in longw all top2coal caving m ining.By the observati on in situ,the paper studies the separati on and broken law of top2coal in different distances to the w all and different heigh ts on suppo rt.

M easure m en t study of m ove m en t law of roof(top-coal)i n fully m echan ized top-coal cav i ng face——X I N G Sh i2jun etc.

T h rough m easurem ent m ethod of arranging deep base po int in gatew ay advanced coal face rib,the movem ent param eters of roof(top2coal)in fully m echanized top2coal caving face and the movem ent law of roof(top2coal)w ere analyzed in th is paper.

Analyz i ng the causes of ma i n roof m ov i ng pressure coeff ic ien t reduced i n top-coal cav i ng face——YAN G Yong2chen

T h is paper analyzed m ain facto r influenced to top coal moved by m ain roof broken,moving law and top coal caving p rocess acco rding to rock structure around the face. So that exp lained causes of m ain roof moving p ressure coefficient reduced.

Study of roof strat a m ove m en t i n coal m i n i ng face under steep angle——HUAN G J ian2gong etc.

O n the basic of the research fo r the roof movem ent of the steep angle m ining face,the paper analyzes different moving fo r m s and m echanical structures of the roof strata on the different po siti on along the slop ing length of m ining face,as w ell as the effect on the behavi o r of ground p ressure of coal face under steep angle.

Research of con trolli ng roof pressure i n the deep extraction of coal——PAN L i2you etc.

A system atic analysis of som e key p roblem s of contro lling roof p ressure in the deep extracti on of coal w as m ade.T he research developm ent of rock p ressure characteristics and p reventi on m easures are described.

F inally,the challenge m echanical p roblem s in th is field are discussed.

St ability prediction of surroundi ng rocks and opti m u m design of roof-bolt param eters i n deep roadway——KON G D e2sen etc.

T he stability of surrounding rock s is analyzed by the m ethod of classificati on p redicti on,loo sening ring p redicti on and num erical si m ulati on acco rding to the comp lex stress environm ent and the variable characteristics of surrounding rock s of deep roadw ay,w h ich can be the theo ry basis fo r bo lting of the deep roadw ay.T he suppo rt param eters of bo lting are also designed op ti m ally in th is paper.A ll these ensure the op ti m izati on of the bo lting and the stability of deep roadw ay in the long run.

Analysis of the relation sh ip between abut m en t pressure distr ibution and f loor heave of gateway——WAN G W ei2 jun etc.

T he relati onsh i p betw een abutm ent p ressure distributi on and floo r heave of gatew ay is analyzed in th is paper.It is considered that the conditi on of gatew ay heave is that floo r strata is effected by the tensile strain com e from the effect of abutm ent p ressure.M eanw h ile,the fracture rock is extruded by the ho rizontal stress.

M easur i ng research of reasonable param eters of coal p illars i n i ncli ne coal seam with roadway dr ived along seam f loor——ZHAN G Kai2zh i etc.

R easonable w idth of coal p illars is deter m ined by a serial of m easuring w ays,such as bo reho le coal dust, loo sen zone of surrounding rock,surface disp lacem ent of roadw ay and dynam ic defo r m ati on of coal roof in N o.13 coal m ine,P ingdingshan m ining group co rpo rati on.T he results indicate that reasonable w idth of coal p illars m ay reduce from15m to8m in ter m s of the conditi on of coal seam,N o.13coal m ine.

Study on parti al extraction of coal p illar under buildi ngs——LUAN Yuan2zhong etc.

In th is paper,the autho r discusses the partial lane extracti on p lan app lied to exp lo itati on of coal p illar under industrial square and living district of Q uanshang coal m ine.Fo r one year,exp lo ited coal has been up to174.8 thousands of tons,the recovery up to38%,the subsidence of surface up to16mm.In the sam e peri od,buildings on the ground have no defo r m ati on and beneficial econom ic and social results have been ach ieved.

Study on per m eation laws of grout i n bed-separation i n reduc i ng subsidence by grouti ng——ZHAN G Q ing2song etc.

L aw s of per m eati on and distributi on of grout w ater are i m po rtant parts of reducing subsidence theo ry,it is related to safety of grouting w o rk s and long2ter m stability of subsidence contro l.Based on the p rinci p le of underground w ater2dynam ics,per m eati on of grout w ater is divided into no p ressure per m eati on and p ressure per m eati on stage, per m eati on models are established,the p rocess of w ater’s sh ift in rock is described in detail.

The application of che m ical mater i al i n m i n i ng safety and it’s f it equip m en t——Z OU D e2yun etc.

T h is paper expounds the physical chem istry and m echanical p roperty of tw o k inds of chem ical m aterial used in m ining safety and p roducti on at p resent,and discusses the research of their fit equi pm ent com bining ejecti on w ith paint into an o rganic w ho le.In additi on,the m echanis m used in m ining engineering technique such as reinfo rcem ent of w all rock,contro lling of ventilati on,leak p roof of air and so on is given.

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?　2002.№2　矿山压力与顶板管理