1、PDF英文：http:/ Finite element analysis of three-way roadway junctions inlongwall mining R.N. Singh, I. Porter, J. Hematian Faculty of Engineering, Uniersity of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia Abstract: This paper presents a three-dimensional finite element analysi
2、s ofthree-way roadway intersections in longwall mining,and assesses the stable/unstable behaviour of three-way intersections under a range of loading conditions. Loads wereapplied to the model by means of uniform stresses on the internal free faces. This method of loading the model from theinside he
3、lped to reduce its size and to eliminate the boundary effects. Stress concentrations and displacement results on themid-height of the pillars, roof and floor strata adjacent to the three-way intersections and cut-throughs were calculated.Based on this study, guidelines for designing the support syst
4、em for three-way intersections are suggested. The results werevalidated by a case study of a three-way intersection in an underground coal mine in the southern coal fields of the SydneyBasin. Keywords:underground coal mining； gate roadway； intersections； stability； finite element method 1. Int
5、roduction A trend exists in Australia for installing highproductivity longwall faces producing 3.04.0 milliontonne raw coal per annum per face. The mainconcern for the success of the high-production longwallfaces is to achieve high rates of developmentand to maintain stability of access roadways and
6、their intersections during the life span of the face.Intersections are formed when the pillars betweenthe two roadways are intersected by driving a crosscut. Roadway intersections in underground mines areparticularly susceptible to ground control problemsdue to inherently wide roof spans used and th
7、e difficulty in installing roof supports promptly inhighly mechanised headings. Stresses induced duringintersection formation may result in high incidenceof roof and rib failures. Despite many investigationsinto the stability of gate roadways intersectionsadverse conditionssuch as high horizontal st
8、ress and unsteady state ofabutment pressure from moving longwall faces maycause instability of gate roadway intersections.Forexample in 1985； major strata control problems inthe main gate of no. 6 longwall panel at WestcliffColliery resulted in roof fall, which stopped coalproduction for a period of
9、 6 weeks. Similarly, a rooffailure incident at Pacific Colliery caused the longwallequipment to be buried resulting in stoppage ofthe longwall operations for a period of 3 months.Thus, unprecedented stratacontrol problems may have significant effects onoverall production from high-productivity longw
10、allsystems even over a short duration.This paper containsan investigation of the application of a three-dimensionalfinite element method to calculate stressesand displacement around three-way roadway intersections.The effects of individual parameters such asdepth of cover, the ratio of horizontal to
11、 verticalstress (K)and the width of opening on the stability of the three-way intersections are examined. Theresults are compared with the field observations at anunderground coal mine in the southern coal field ofthe Sydney Basin. 2. Stability analysis of three-way intersections usingthree-dimensio
12、nal finite element models The procedure used in the stability analysis of thethree-way intersections comprised of defining themechanical properties of the rocks surrounding theintersection, the geometry of the intersection and thevirgin state of stress. The stresses and displacementsinduced around t
13、he intersections were computed usinga three-dimensional finite element method. Ifunstable conditions existed, either the design of supportsystem was changed or the geometry of thestructure was modified.Important input data forthese models were vertical stress and the ratio ofhorizontal to vertical s
14、tress K for a given lithologyand dimensions of the roadway intersection (see Fig.1). Assuming symmetrical conditions around a threewayintersection, only half of the structure wasmodelled using eight-node solid elements comprisinga total of 7190 elements and the 11 597 grid points.The computer runnin
15、g time was 17 h using around 1Gb of memory. The rock mass properties assigned tothe intersection model are presented in Table 1.The loads were applied to the Fig. 1. Plan and section of the finite element three-dimensional intersection model Table 1 Rock properties assigned to three-way inter
16、section models Rock type Thickness /m E /GPa Medium grain sandstone 4.0 10.0 0.20 Fine sandstone and mudstone 3.0 6.0 0.25 Coarse sandstone and shale 2.0 3.0 0.20 Top coal 1.0 3.5 0.3 Coal 3.0 3.5 0.3 Mudstone 1.0 8.0 0.25 Coarse sandstone 4.0 12.5 0.2 Medium grain sandstone 5.0 10.0 0.2 model
17、 by means ofuniform pressures on the internal free faces. Thistechnique of applying load from the inside helped toreduce the size of the model and to eliminate boundaryeffects. For all the loading configurations depictedin Table 2, a linear solution method was used. Table 2Loading conditions applied to the three-dimensional model Loading configurations z / MPa y/ MPa x / MPa 1 10.0 0.0 0.0
