REP33070 - Laserfiche WebLink

Home Browse Search

- 13 - 1 1 1 1 1 1 1 1 1 would occur. A tension crack would typically develop at some distance behind the crest of the bench. A hypothetical case of such landslide development is shown on Plate 3, Bench Degradation Process. The development of tension cracks is the first indi- cation of future stability problems. The slope stability would further decrease as surface water would seep through the open tension cracks and into the bedrock. After a certain period of time, a landslide would develop. The failure (slip) plane of the landslide would typically follow the layer of underclay below the coal, and it would cut at a steep angle through the overburden formation. Slides of this type are very common in the Mesaverde Formation. A landslide of such a type would create a steep scarp in the upper part of the slope. This scarp itself would not be permanently stable and minor slumps on it would cause further flattening of the slope. It can also be expected that the lower slide portion, which would spill over the lower part of the slope, would not be permanently stable, and it would be further flattened by erosional .processes and by minor slumps which would develop during the period of high precipitation and exceptionally unfavorable climatic conditions. We believe that the landslide area between the upper and the lower benches, as defined by the previous studies, is the result of landslides of such character. The area does not carry traces of important deformations of a large extent; parts of the slope have, however, factors of safety still very close to unity and any inappropriate construction within the area could cause further sliding as it became evident during some excavations in the spring of 1950. cEO++wno coµw~nrw. iNC.