The Pre-calculation of Ground Subsidence
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At the beginning of this century, the mine surveyor was faced with the task of estimating, in increasingly thickly populated mining districts, the mining damage likely to be done to buildings, transportation installations, and agricultural land lying over new mines. He had little more to go on than the mine plans, and had to institute procedures for observing ground movement processes and to develop prediction methods suited to particular mines. In doing so he could confine himself, as was shown in the previous section, to the vertical component of movement — subsidence vz — and the horizontal component of changes in position — displacement vx and vy. As is known, from these components as worked out for two or three points near the surface object under consideration, it is possible to derive all the other factors of movement, such as tilt and curvature on the one hand and extension and compression on the other. The difficulty in covering the movement process in the whole rock body, from mine to surface, in a closed calculation persists even today. Consequently it was necessary to do without a mechanical model and find instead abstract or analytical calculation procedures which were simple to apply to deformation at the surface. The only mechanical characteristics of the rock body available for the calculation were details of the mine geometry such as area, thickness of seam, and depth, which served as quantitative parameters for strata movement, and the results of observations such as limit angle and angle of break. At first only the static end-state of movement could be considered. Later, attempts were made to derive intermediate trough outlines from final shapes by means of time factors.
KeywordsSurface Point Influence Function Ground Subsidence Maximum Subsidence Limit Angle
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