Backfilling and grouting can be used to stabilize abandoned underground workings. This is a preview of subscription content, access via your institution. Rent this article via DeepDyve. Berg, W.
Google Scholar. Brown, A. Bruhn, R. Colaizzi, G. Dunrud, C. Esaki, T. Gormley, J. Gray, R. Hunt, S. Karfakis, M. Matheson, G. Can we mine another planets?
We have almost exhausted our natural resources and there are huge What are the differences between open pit mining, underground mining, and strip mining? See all questions in Mining. Impact of this question views around the world. Provided by the Springer Nature SharedIt content-sharing initiative. Skip to main content. Search SpringerLink Search. Abstract This paper reviews the modes of formation of sinkhole subsidence associated with mining activities, drawing on examples in India.
References Anon. Google Scholar Colaizzi, G. Google Scholar Dunrud, C. Google Scholar Gray, R. Google Scholar Karfakis, M. Google Scholar Matheson, G. Google Scholar Piggott, R. Google Scholar Singh, T. Google Scholar Whittaker, B. Google Scholar Wildanger, E. There are distinct differences between the trough-like subsidence caused by high-extraction methods and that caused by pillar failure. Subsidence caused by high-extraction mining.
High-extraction mining typically results in smooth subsidence profiles with the vertical displacement less than the mining height. In the case of longwall mining in the absence of a strong layer such as dolerite in the overburden, the maximum amount of subsidence, S m , according to van der Merwe , is a function of the depth of mining, panel width, and mining height and is given by.
Subsequent routine observations by the author at several sites have indicated that for pillar extraction, Equation [1] should be modified by the incorporation of a modifying factor, f m:. The full expression for the maximum subsidence is then. In the case of multiple seam mining, the subsidence caused by extraction of the first seam is given by Equation [3] while the additional subsidence caused by extraction of the subsequent seams is approximately equal to the full effective mining height of the additional seams van der Merwe, Shape of subsidence trough.
According to van der Merwe , the shape of the half-profile of the subsidence trough is described by. Inspection of the data on which Equation [4] is based indicated considerable variability see Figure 2. Upper and lower limits were fitted to the family of curves derived by van der Merwe and these are described by Equations [5] and [6] respectively.
It is considered more reasonable to state that subsidence can be expected to be within the limits described by Equations [5] and [6]. These equations can also be used to evaluate the potential for further subsidence in the case where subsidence has already occurred - if the measured profile plots above the upper limit, it should be considered that there is potential for further subsidence in the future.
Another use of the equations is to construct three-dimensional plots of the subsidence, using the following method. It should also be noted that for single seam workings, meaningful subsidence from a structural point of view is contained within the mined panel delineated by inter-panel pillars, but that small amounts of subsidence do in fact occur over the solid areas as well.
Related elements of subsidence. Vertical subsidence per se is of major significance only where ponding may result. For all other purposes, the induced tilt and strain are more important. Figure 3 shows a simplified half-profile of a subsidence trough with exaggerated vertical scale, where the induced strain and tilt are also shown.
The point of inflection is important in subsidence engineering. It marks the position where half of the maximum subsidence occurs, which is also the position of maximum tilt and the position where the strain changes from tensile at the edges of the subsidence profile to compressive in the central region. It has been seen van der Merwe, that the point of inflection typically occurs at a lateral position 0. The maximum tensile strain - which is where surface cracks can be expected - occurs at a position 0.
It has been shown van der Merwe, that the magnitudes of tilt and strain can be determined based on the half-profiles of subsidence. However, due to the variability inherent in subsidence profile shapes, the real magnitudes are more variable than those predicted from the profiles. The maximum values to be expected, empirically based on measurement according to van der Merwe , are: Tilt:.
Note that the magnitude of compressive strain is greater than the tensile strain, which is characteristic of subcritical subsidence profiles. For certain structures the induced radius of curvature, R, is an important parameter.
It can be estimated based on geometrical considerations by fitting a circle segment through the edges and centre of a subsidence profile:. Subsidence caused by pillar failure. There are distinct differences between the processes of subsidence caused by high-extraction mining and that caused by pillar failure van der Merwe and Madden, The resulting subsidence also differs.
There is a scarcity of data describing pillar failure subsidence, implying that the subsidence is predicted with lower confidence than that for high-extraction mining. The scarcity of data is due to the fact that pillar failure is a rare occurrence, with an estimated 0. It is also not possible to know beforehand where and when such failures will occur, and consequently accurate elevations of the pre-failure topography can rarely be obtained.
Previously, indicative data by MacCourt, Madden, and Schumann was used to estimate the magnitude of subsidence that can be expected in the event of pillar failure. Their data has since been supplemented by new cases and the new database was re-examined see Figure 4. The data is presented in Table II. Subsidence due to pillar failure. It was found that the maximum subsidence is related to the equivalent mining height, h e i.
Tilt due to pillar failure. The maximum tilt was also found to relate to h e and H see Figure 5. The relationship was found to be. Effect ofa dolerite sill. Subsidence may be arrested by the presence of a thick, strong layer in the overburden that is capable of bridging across the mined panel. In South Africa, dolerite sills frequently occur in the overburden and have received attention in this regard.
Dolerite is known to be vertically jointed, and based on a modified key-block mechanism, van der Merwe derived the following expression for the minimum span required to result in sill failure:. Equations [13] to [15] can be used to plan panel widths in order to control the state of the sill.
The temptation to design for an intact sill in order to prevent subsidence from occurring over the long term should be avoided, as cases have been known where the sill was initially intact but failed several years after mining. Two sub-classes of subsidence are discussed under this heading.
The first is sinkholes caused by progressive roof collapse from underground, which results in the sudden formation of a sinkhole when the cavity reaches the surface. The second is the occurrence of much smaller sinkholes caused by subsurface erosion, which is a consequence of trough subsidence that only manifests after a period of time ranging from months to decades.
Progressive roofcollapse. This mechanism is described in Canbulat et al. Their equation, however, is only valid for a sinkhole with diameter equal to the width of bord intersections underground and for cavities with vertical sides. Neither condition is necessarily true.
A simplified cross-section of a cavity choked by rubble from the collapse is shown in Figure 6. It shows the cavity as a truncated cone, as opposed to a cylinder. For the cavity to be choked by bulked rubble from the roof collapse, the bulked volume A in Figure 6 must be equal to the sum of volumes A, B, and C.
Where the pillars are small, it is possible for the toes of the collapsed rubble to touch, restricting the volume available for the bulked material in the roadways - see Figure 6a. This can happen where the pillar width, w, is less than hcota. In that case, Equation [20] should be substituted with.
Equation [20a] should be used with caution as it is valid only if adjoining intersections collapse at the same time and extend at the same rate. Experience indicates that adjoining sinkholes very seldom form at the same time.
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