长壁开采采空区上部地表残余变形的机理与控制外文文献翻译

英文原文Mechanism and control of ground residual deformation over longwall goafGUO Guang-li, WEI Kuang-ling, MU Bin-shan, Gao Jing-xiang, H E Guo-qing(1. China University of Mining and Technology , Xuzhou 221008 , China ;2. Chongqing University , Chongqing 400044 , China ;3. Qiwu Coal Mine , Jining 277606 , China)Abstract: The deformation of rupture rock mass in goaf is the main reason for ground terrene residual deformation.Based on field measurement and similar material simulation , the rupture strata structure and its residual deformation characteristics in the longwall goaf and its overburden are pointed out. On the basis of these achievements , the authors propose the mechanism of strengthening rupture rock mass ground and the control measures of deformation resistant structure. Using the case of main coal building in Xinzhuangzi Coal Processing Plant , this paper introduces the influence of strengthening rupture rock mass and deformation resistant structure.Key words: abandoned goaf ; residual deformation ; rupture rockmass ; deformation mechanism; deformation control1. INTROD UCTIONThe movement and dest ruction of overburden layers caused by underground mining changed overburden engineering geology characteristics and formed the engineering geology condition of extracttion subsidence rupture rock mass ground. Even by long time natural pressure after mining , these phenol mena of residual cavity , bed separation ,mining induced fissure can be seen in goaf and overburden. Subcompaction and gap with saturated water can also be seen in caved goaf . Under the influence of inner and external factors (for example ,ground stress , underground water , superimposed load of new building) , the rupture rock mass will produce second movement and deformation , which is a serious threat to ground buildings safety.This is the main potential safety hazard that restrains large scale application of terrene in abandoned goaf .The deformation of rupture rock mass in goaf is the main reason for residual deformation in collapsed area terrene. Clarifying structure and deformation characteristic of rupture rock mass in goaf , predicting terrene residual subsidence and deformation , adopting suitable measures to strengthen rupture ground and designing reasonable building structure are the basic research directions to guarantee the safety of the buildings above abandoned goaf.2 RUPTURE ROCK MASS STRUCTURE AND RESID UAL DEFORMATION CHARACTERIS TIC OVER LONGWALL GOAFAfter extracting underground ore body , the overburden will move and deform t- hat induces thegreat change of the property and forms of rock ,and will form a new goaf rupture rock mass structure system composed of caving zone , fracture zone and inflection subsidence zone (Fig. 1).Fig. 1 Rupt ure rock massst ruct ure over longwall goafAccording to a large amount of field inspectionand simulation research results , abandoned goafsliven up and the mechanism of extraction rupture ground unstability can be analyzed as follows :1) The rupture rock pieces above the edge of longwall goaf articulate with each other and form a construction similar to half arch struct ure with one of its foot t- rending to coal wall. In this structure ,the first and second rupture rocks play key role in the relatively stable structure of rock mass above goaf. If these key rocks lose their stability , they will influence overburden , and produce strata movement and deformation again , then extent toterrene further.2) The block beam above longwall goaf results in the difference of the crack rockps compactivities in various positions of caving zone. There is unstowed cavity around open off cut , terminal line ,up and down crossheading ( around the edge of goaf). From edge to center of goaf , caving zonecan be divided into sub compaction area , cavingrock accumulated area , caving rock compaction area and full compaction area.3) In the super critical extraction area above the middle of goaf , caving rupture rock mainly supports vertical pressure stress. It can be compacted by natural pressure as time passing , but since rupture rocks are beyond retrieve , the fissures among rocks will exist forever. It will be compacted again when being suffered additional burden.4) For the difference of stratum bedded deposit characteristic and each rock formation mechanical property , a large amount of bedded separation fissure will be produced in inflection zone of overburden. Under the influence of underground water and external force , especially vertical burden ,these bed separation fissures may be compactedand closed , which will lead to the subsidence of terrene.Based on the analyses above , we can divide t he“liven up ”of rupture rock mass in abandoned goaf into four types :1) Under the effect of overburden , the rupture rock in goaf body has long term slow creeping deformation.2) Under the effect of underground water and air , the rupture rock in goaf will be effloresced , its intensity will be attenuated , and the rupture rock can be compacted again under overburden.3) Since the intensity attenuation of rupture rock and residual coal pillar begin , the overburden above mining dist rict will lose stability again though it is stable before.4) Under the effect of external forces , the rupture rock mass above mining dist rict will lose structure stability again. The external forces mainly include earth quake force , tectonic stress caused by region geological structure , disturbance stress caused by exploding or mining , addition burden on the surface , etc.According to the research results of similar material physical analogy and finite element method , under the condition of deep goaf , the residual deformation of terrene is mainly a slow subsidence course and its uneven subsidence is limited , so reinforcing buildingsp ability to resist deformation is the main technological measure to guarantee its safety. Under the influence of external force , the unstability of the secondary block beam or key strata of overburden mass in goaf is the main cause for serious terrene subsidence in shallow goaf . So strengt hening the block beam structure above goaf and key strata , raising the carrying capacity of rock mass balanced structure and increasing the steady of the balanced structure are the main methods to strengthen the rupture ground above abandoned goaf .3 TREATMENT OF RUPTURE ROCK MASS OF SHALLOW LONGWALL GOAFUnder the influence of external force , the destabilizing of the secondary block rock beam or key strata of overburden is the main cause for serious ground subsidence over shallow goaf . So strengthening t he block beam structure or key strata above goaf and raising its bearing ability and stability are the main ways to control rupture foundation rock mass deformation over abandoned workings. These technological methods mainly include the following six types.1. Back filling and grouting in whole goaf The whole goaf and mining induced fissure of overburden should be backfilled completely by cement , tailings , flyash , sand or clay , etc. This method can get rid of a hidden peril of ground subsidence. 2.Grouting concrete column for partial support Drilling large diameter borehole on the construction field forms the grout cement or reinforced concrete column to provide surface building support . The column must pass through rupture rock body and reach the integrate rock body beeow abandoned mine workings.3.Grouting to strengthen block beam in fracture zone Grouting to stow the bed separation and crack fissure in fracture zone can st- rength the compound block beam structure into a whole continuous half arch rock beam over goaf . This measure is suitable for strengt hening ground around goaf border with large cave and sub stowed area. It can prevent half arch block beam above the edge of goaf from losing stability. 4.Grouting to strengthen basement in sagging zone Grouting to strength basement in sagging zone below the building can integrate rupture rock body into a whole to guarantee the buildings p subsidence uniformity.5.Accumulating pressure processing This measure is to prepress the ground by accumulating debris or sand , etc , on the area above abandoned goaf , which will make the potential differential settlement of ground take place , then the ground will be compacted and the intensity will be improved. Moreover the subsidence will reduce in practical project later. This method requests that effective load shouldnpt lighter than additional load caused by new buildings.6.Using high energy rammer to deal with shallow rupture rock body Using high energy rammer to deal with shallow rupture rock body will compact the fissure and bed separation in shallow ground , and increase the load carrying capacity of shallow ground. This method is mainly suitable for the foundation soilt reatment of general civil buildings constructed on the middle area of goaf .4 DESIGNING MEASURES OF ANTI2DEFORM ATION STRUCTUREUnder the condition of certain mining deep and even load , longwall goaf seldom produces violent subsidence , and the distribution of residual subsidence is continuous and gradually changed.Buildings above abandoned goaf undoubtedly will be influenced by ground residual deformation. The ground deformation , transiting to the upper structure of building through foundation , will make the structure have additional stress and deformation. Adopting the designing measures to improve the coordination relation among the base , foundation and upper structure is the basic method to protect buildings on goaf. By analyzing the coordinate relation between the ground subsidence and buildingps deformation , we conclude t he following three principles during designing buildings with deformation resistant structure .1.Structure yielding measuresThe technological measures are adopted to absorb part of terrene deformation or to let building have enough flexibility to adapt buildingps unbalanced subsidence and deformation , and to reduce the additional stress caused by terrene deformation. These measures include setting deformation gap , reducing unit length of building or designing flexible building with hinge joint steel frames , which can change the positions related to each other.2.Structure rigidity strengthening measuresThese measures are to raise stiffness and in tegrity of building units to increase their resisting ability of terrene deformation , which include strengt hening stiff ness and intensity of each unitps ground , adding structure components , strengthening component , etc. We can design adjustable base , for example , ground composed of thicker plate or concrete base row. We can also use ram to make the upper structure back to its original position if uneven subsidence happens.3.Joint structure rigidity strengthening and structure yielding measuresFor large scale indust rial buildings , the needs of equip mentinstallation and its technological process must be considered , in order that structure rigidity strength- ening and structure yielding measures can be applied entirely. Under this circumstance , we should use some synthesize methods to meet the needs of p- roduction safety.5 PROJECT INSTANCE1.Project general conditionsA main building of a coal dressing plant with crib and bar foundation is 73.5 m long , 35 m wide and about 40 m high. It is a multilayer and multispan reinforced concrete frame structure. This building , with complicated inner structure , has lots of dressing equipment and is sensitive to terreneps unbalanced subsidence and horizontal deformation. In the west and north below the main building is A1 and A3 coal seam goaf (the relative position of goaf and main building can be seen in Fig.2 ,and this coal mine had been extracted from 1951 to 1962. The extraction depth of seam A3 is 48.8 m ,minable height is 3. 65 m , and the extraction depth of seam A1 is 62 m , minable height is 2.2 m ,stratatilt angle is 2225. Coal mining method is long wall mining on the strike , using breakage method to deal with roof . Reconnoiter research indicated that the rupture rock mass caused by mining develop ment area has reached to the southwest corner of the main building. Its development range is also shown in Fig. 2. The up face of gap development area is only 15 m deep to surface. Around the edge of goaf , there are residual cavities that caused overburden to be seriously damaged and some ground stability to be relatively poor.Fig. 2 Surface under ground contrast plan near main dressing building2.Using consolidation grouting to deal with mining rupture rock ground According to the characteristic of mining rupture foundation , the half arch block rock beam structure in cracked zone above goaf can best rengt hened by using consolidation grouting method , which makes the foundation form a integrated , stable half arch rock structure. Designed grouting area is 637 m in this project and the average stage height of grouting is 8 m. In practice ,seven grouting holes have been drilled. The mate rial used in grouting is 425# Portland cement .3.Measures of designing deformation resistant structureIn order to guarantee dependability of designing , a space finite element model is adopted to analyze the structures with 6 floors and 8 floors of main building. The model analyzed different basis forms , considering inner force and section adjust ment under 10 kinds of combination circumstance ,such as static burden , dynamic burden, earthquake force , the influence of ground deformation and wind burden. The purpose of the analyses is to select the suitable structure stiffness. After many times of analyses and adjust ment , the dist ribution of reinforcement bar was designed. The flexible measurements were used in both units with 8 and 6 floors. Between the two indispensable units , 100 mm deformation fissure has been left .4.Implementing effectTo verify designing reliability and to ensure safety , the ground subsidence and structure stress were monitored. According to the analyzing of the main building ground subsidence and internal force , we can draw the conclusion that the ground subsidence is even. Basis reactive dist ribution is even and the change of basis reinforces inner force is accorded with normal law. These inform that strengt hening region rupture ground and deformation resistant structure are successful , and these methods guaranteed the main buildingps safety.6 CONCL USIONS1) The deformation of rupture rock mass in goaf is the main reason leading to collapse area terrene residual deformation. Under the condition of deep goaf , the major terrene residual deformation is a slow subsidence process , and reinforcing buildingp deformation resistant ability is the main way of potecting its safety. 2) Under the influence of external force , the rupture rock mass losing its st- ructure steadiney is the main reason leading terrene to seriously subsidence deformation in shallow goaf. Strengt hening half arch block beam above the shallow goaf ,increasing the steady and carrying capacity of rupture rock mass ground are the main methods to deal with unstable ground above abandoned goaf .3) Adopting struct ure rigidity strengt hening and yielding measures to resist deformation ,improving the coordinate deformation relation among buildingps basis , ground and super structure are the basic methods to protect building in goaf safety.(4) Practical example indicates that the safety of large sized indust rial buildings above shallow goaf can be protected after grouting and using deformation resistant structure.中文译文长壁开采采空区上部地表残余变形的机理与控制摘要：采空区岩层破裂变形是导致地表残余变形的主要原因。基于现场测量和相似材料模拟，采空区及其上覆岩层岩石断裂构造及残余变形特性已被揭示。以此为基础，作者提出了岩层破碎的加强机制和抵抗变形的控制方法。本文将以新庄子煤炭加工厂的主要建筑物为例介绍岩石破碎的影响和抵抗变形的结构。1.导言地下开采导致的上覆岩层移动和破坏改变了上覆岩层的工程地质特性并形成了开采下沉破裂岩石面的工程学地质情况。即使开采后在长时间自然压力作用下，采空区及其上覆岩层中仍能看到残留空间、地层分离、开采裂缝等现象。跨落的老空区内则会出现分段压实和饱水裂隙。在内外因素（如地面应力、地下水、新建筑的阶层载荷等）的影响下，破碎岩体将产生二次移动和变形，这会对地面建筑的安全形成严重威胁。这是抑制废弃采空区上土地应用的主要安全隐患。塌落区域地表残余变形的主要原因是采空区岩石破碎变形。弄清采空区岩石破碎结构和变形特性，预测地表下沉与变形，采取适当措施加固破碎岩层，设计合理的建筑物结构，是保证采空区上地面建筑安全的基本研究方向。1.长壁采空区上岩石破碎结构与残余变形特性地下矿体被开采之后，上覆岩层会移动变形导致岩石性质和形态的强烈变化，并会形成由跨落带、裂隙带、弯曲下沉带组成的新的采空区岩石破碎结构体系。（图1）根据大量的现场测试和模拟测试结果，废弃采空区的“活跃”和开采破碎区地面不稳定性机制可被分析如下：1）长壁工作面采空区边界上破碎石块接合在一起形成一种一端伸向煤壁的半拱结构。在这种结构中，首先破裂和二次破裂的岩石对于采空区上岩体形成相对稳定的结构起到了关键作用。如果这些关键岩层失去了稳定性，那么将会影响到上覆岩层，导致岩层移动与变形的再次产生，接着进一步影响到表土层。图1 长壁开采老空区上破裂岩石结构2）采空区上的石块条带造成跨落带不同位置破裂岩石紧密性的不同。开切眼、停采线和联络巷（采空区边缘）上下都有卸荷空间。从采空区端部到中部，跨落带可以分为初级压紧区，跨落岩石堆积区，跨落岩石压实区和跨落岩石完全压实区。3）在采空区中部之上的超临界开采区域，跨落岩石主要起支持垂直应力的作用。随着时间的推移，这些破碎岩石可以被自然压力压实，但是由于破碎岩石的不可恢复性，岩石中的裂纹将永久存在。当施加额外载荷后，这些岩石将进一步被压实。4）由于岩层存积性质的不同和每一岩层的力学特性，在上覆岩层的弯曲下沉带产生大量的层状分离裂缝。在地下水和外力尤其是垂直负荷的作用下，这些岩层分离裂缝将会被压实闭合，这将导致表土下沉。综上所述，我们可将废弃采空区上破碎岩体的“活跃”分为四种类型：1）受上覆岩层影响，采空区内破碎岩体进行长期缓慢的变形。2）受地下水与空气的影响，采空区内破碎岩石将被风化，其强度减弱，在上覆载荷下岩石会被进一步压实。3）由于破碎岩石强度的衰减和残留煤柱开始受压，采区上覆岩层开始由稳定状态进入失稳状态。4）受外力影响，采空区上破碎岩石将再次失去结构的稳定性。外力主要包括由区域地质结构引起的地震力和构造力，爆破或采矿引起的干扰应力，附加表土负荷等。根据相似材料模拟和有限元方法的研究结果，在深部采空条件下，表土层的残余变形主要是缓慢下沉过程，不均匀下沉受到了限制，因此加强建筑物抵抗变形的能力是保证其安全的主要技术方法。在外力作用下，二次碎石带或采空区上关键层岩石失稳是浅部采空表土层剧烈下沉的主要原因。因此加固采空区上碎石带结构和关键层，提高岩体平衡结构的承载能力和增加平衡结构的稳定性是加强废弃采空区上地面破裂的主要方法。3浅部采空破碎岩体的处理在外力作用下，二次块状岩石带或关键层的不稳定是浅部采空上地表剧烈下沉的主要原因。因次加固碎石带结构或采空区上关键层，提高其承载能力和稳定性是控制废弃巷道上基岩变形的主要途径。这些技术方法主要包括下列六种类型。1.在整个采空区充填灌浆整个采空区和采矿引起的裂缝应该用水泥、矿渣、粉煤灰、沙子或粘土等完全填充。这种方法可以摆脱地表下沉的潜在危险。2.喷浆凝注局部支护在建筑地打大钻孔喷水泥浆或加强混凝土圆柱为表面建筑提供支护。圆柱必须通过破碎岩体到达废弃矿井巷道下面的完整岩体中。3.裂隙区喷浆加固碎石带喷浆