R Ramazani Omali; N Hafezi Moghaddas; K Heidari
Abstract
Rock falls are the usual forms of slope instability in hill slopes. The high velocity and rapid occurrence are the main differences of rock fall and other rock instability. Therefore, the rock falls are among the most destructive mass movements and results in high loss of lives and heavy damage to the ...
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Rock falls are the usual forms of slope instability in hill slopes. The high velocity and rapid occurrence are the main differences of rock fall and other rock instability. Therefore, the rock falls are among the most destructive mass movements and results in high loss of lives and heavy damage to the structures, roads, residential area, farms and etc. In this research, rock fall in rocky slopes of the TepalMountain in northwest of Shahrood city was investigated. For this, the large scale geological map of area (scale of 1:10000) was produced and joint studies in 12 sections performed. Then, the slope instability was analyzed by two methods of stereographic (using Dips 5.103 software) and analytical method (by Swedge 4.078 and rock fall 4.039 softwares). The results show that all of the slopes are stable in static conditions and become instable in dynamic state. In critical states of huge raining and earthquake intense instability will be occurred and the big problems could be created for the down area of slopes. Based on the results of analytical and using the Arc GIS 9.3 rock fall hazard zonation map was produced. In addition, by overlaying of landslide hazard map and land use map, the area affected by rock falls was distinguished. The results of this study show that Salamaty road, Mazar Shohaday Gomnam and its access road, some part of AzadiPark, the tourism hotel, some of the residential area down of the Salamaty road and some parts of the AbsharPark are located in the hazard zones.
M Mirzaei Souzani; A Shahidi; R Ramezani; F Alizadeh Sevari
Abstract
In order to survey the extensional forces dominated in central Alborz since Late Triassic (Norian) to Middle Jurassic (Early-Bajocian), synsedimentary normal and strike-slip fault systems in Balladeh valley which contains significant distribution of Shemshak Group have been studied. Analysis of σ3 ...
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In order to survey the extensional forces dominated in central Alborz since Late Triassic (Norian) to Middle Jurassic (Early-Bajocian), synsedimentary normal and strike-slip fault systems in Balladeh valley which contains significant distribution of Shemshak Group have been studied. Analysis of σ3 orientation for 404 fault planes in 35 normal fault systems, show two major extension directions at NNE (020°) and NE (070°) trends during sedimentation of Shemshak Group. Also, the presence of a minor extension direction trending WNW (300°) which is coincident with extension direction of synsedimentary strike-slip fault systems implies the existence of transtentional basins in the Shemshak basin at that time. The southward movement of southern edge of Eurasia (from latitude of 30° to 15°) and its clockwise rotation for some 40°-50° during Triassic-Jurassic periods led to domination of N-S extension in early times of Shemshak Group sedimentation, and as soon as the Eurasian plate rotated, the extension direction was changed into a NE-SW trend. These separated records of paleostress axis trends are also due to the high sedimentation rates and subsidence in Norian-Rhaetian and Toarcian-Aalenian during Shemshak Group sedimentation. The minor extension trending WNW-ESE (278°-307°) is due to σ2/σ3 permutation between N-S σ3 direction of stress tensor and its σ2 axis. Low values of Φ (less than 0.4) generally correspond to situation characterized by σ2/σ3 permutation; therefor it causes multidirectional extension in extensional stress regimes. About 80 percent of sites which show WNW-ESE paleostress extension trend have low Φ values. This issue explains σ2/σ3 permutation of N-S major extension trend. The areas of mentioned stations and also those ones with strike-slip fault systems σ3 directions of which are directed WNW-ESE had high basin crustal anisotropy.
