1、PDF英文：http:/ 翻译部分 英语原文 ON MINING-INDUCED HORIZONTALSHEARDEFORMATIONS OF THE GROUND SURFACE Gang Li1, Robert Pquet1, Ray Ramage1 and Phil Steuart1 ABSTRACT:Horizontal shear deformations have not been commonly considered in subsidenceengineering and risk management practices. This situatio
2、n is quite different from many otherengineering disciplines. This article presents the authors initial findings of case studies from anumber of collieries across all NSW Coalfields. The objective of this article is to highlight thesignificance of a ground deformation mode, that is, horizontal shear,
3、 and its implications to subsidenceengineering and risk management. A Shear Index is suggested to facilitate studies of mining-inducedshear deformations of the ground surface. INTRODUCTION This article presents an argument that conventional subsidence parameters specifying horizontaldeformations, in
4、 particular, horizontal strains (i.e. change in length), are inadequate for subsidenceengineering and risk management. The above-mentioned inadequacy can become practicallyimportant in areas where only low magnitude of conventionally defined horizontal strains is detectabledue to deep cover depths (
5、or relatively low “extraction width-to-cover depth” ratios). Through the preliminary investigation of a number of coals in NSW, the study foundthere is clear evidence to suggest that the above-mentioned inadequacy is related to a lack ofunderstanding of mining-induced horizontal deformations of the
6、ground surface, in particular,horizontal shear deformations. Despite theoretical definitions found in limited literature on mine subsidence (e.g. 1992),horizontal shear deformations have not been commonly considered in subsidence engineering andrisk management practices. This situation is quite diff
7、erent from many other engineering disciplines. HORIZONTAL SHEAR DEFORMATIONS When two adjacent cross sectionsof a stem has a pair of horizontal force perpendicular to stem axis but works in the opposite direction of breaking, and it produces deformation that two section along the lateral force direc
8、tion of relative rupture occurred. The deformation called shear deformation. Indicators of horizontal shear deformations, as identified by this study, comprise: 1. Observed subsidence effects on civil structures indicating influence of shear deformations andsignificance of this deformation mode in t
9、erms of its impacts and frequency of occurrences.Theshear effects at a particular site are demonstrated in Figure 1； 2. Statistical information suggesting a strong correlation between the shear -affected structures and strip footings, which have less capacity to resist or accommodate horizonta
10、l shear deformations as compared with that for other types of footings considered in this study.The analyses show that the transverse shear deformation effect has a significant influence on the thick reinforced concrete slabs and the concentrated load condition； 3. Observed patterns of mining-induce
11、d surface fractures and deformations (in plan view)suggesting influence of shear, for example, i) en-echelon fractures near chain pillars whereshear deformations were active or ii) occurrences of surface wrinkles where the effects ofhorizontal shear were clearly visible 4. Importantly, horizontal sh
12、ear deformations of ground surface as indicated in 3D survey dataobtained from a number of collieries across all NSW Coalfields (to be furtherdiscussed). However, rigorous definition, in accordance with the principles of continuum mechanics (e.g. Jaeger, 1969), ofhorizontal shear strains is not poss
13、ible using 3D survey data from a straight line of survey points.It follows that if warranted considering the significance of the surface features and their capacity toresist or accommodate shear deformations, the current surveying practices may need to be changedto obtain properly defined horizontal
14、 shear strains (or principal strains). To utilise the large amount of subsidence data in existence in the mining industry, analternative (andapproximate) Shear Index is suggested in order to gain an understanding of the generalcharacteristics of mining-induced horizontal shear deformations. This She
15、ar Index is derived basedon the component of horizontal movements perpendicular to a survey line or a line of interest. Theformula for deriving this index is the same as that for the conventionally defined tilt. Physically, thisindex reflects angular changes in the horizontal plane but it is not pos
16、sible to tell what causes suchchanges, being either shear or rigid body rotation or both. However, the distribution pattern of thisindex can help to understand the development of shear deformations and to find "trouble spots" (referto further discussions presented in the Section below). FU
17、RTHER DISCUSSIONS ON HORIZONTAL SHEAR DEFORMATIONS Figure 2 shows the distribution pattern of horizontal movements perpendicular to a survey line acrossa longwall panel and the corresponding Shear Index as discussed above. Although the site is located in the Hunter Coalfield with shallow cover depth
18、s, this case is selected asit provides a clear demonstration of the following observations common to the studied cases from allNSW Coalfields: A complex history of the horizontal movements perpendicular to the cross line (Figure2a) involving a reversal of movement direction after the extraction face
19、 passed thesurvey site by a certain distance. This distance varied from site to site. Similar findingswere reported by Holla and Thompson (1992) and Mills (2001)； Indications of horizontal shear deformations (near both solid ribs in this case, as shownby the Shear Index plotted in Figure 2b), noting
20、 the reversal in the sense of shearingafter the extraction face has passed the survey site. The reversal in the sense ofshearing has apotential to enhance the effects of shear deformations, and The occurrences of permanent horizontal deformations. IMPLICATIONS From the 3D survey data collected from
21、a number of collieries across all NSW Coalfields, thecharacteristics (i.e. the magnitude, nature, distribution and timing of occurrences) of the conventionallydefined subsidence parameters are compared with those of the following horizontal deformationalparameters: (i) Mining-induced horizontal movements perpendicular to survey grid lines, and (ii) The corresponding Shear Index as discussed above.
