1、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 ,
2、 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
3、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 o
4、f 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 eng
5、ineering 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. Subcom
6、paction 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 threa
7、t 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 characte
8、ristic 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
9、 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 cavin
10、g 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
11、 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
12、 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 positio
13、ns 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.
14、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
15、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 externa
16、l 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 efflo
