زمین لغزش

objective:

 The increase in natural hazards and the damage caused by them, especially with the expansion of human dispersion in all parts of the world, has made attention to this issue an international necessity. Landslides are one of these hazards, which usually affect settlements in mountainous areas, especially villages. The identification of vulnerable areas and their prediction in programmes, as well as the attempt to identify, introduce and take into account areas at risk, is a requirement for land planning and management and can reduce a large part of the threat of this hazard. Therefore, the aim of this study is to evaluate the landslide situation in the Bazoft basin using the AHP model and the application of Geographic Information System (GIS).

The type of research is applied and the approach that governs it is analytical and quantitative. In order to assess the risk, slope, slope direction, geology, fault, land use, temperature and precipitation indices, distance from road, waterway and also distance from settlements were used. In order to assess the landslide risk, a hierarchical structure of criteria and sub-criteria was first drawn up. After preparing the desired maps, the weight of each criterion was calculated based on the AHP process. The factor layers were prepared using different sources such as 1:50,000 topographic map, 1:100,000 geological map and Landsat satellite images in the ArcGIS environment.

The zonation of the basin in terms of landslide sensitivity was examined in five classes from "very low" to "very high" sensitivity in the final map. The highest sensitivities are found in the southern, central and northeastern parts of the basin.

In terms of area, 10.15% of the basin is "very high risk", 22.24% is "high risk", 27% is "moderate risk", 27.61% is "low risk" and only 13% is "very low risk". The results also showed that out of the 219 settlements in the basin, about 23% are in the "very high risk" range and only 19% are in the "very low risk" range; this is considered a serious threat to the inhabitants and it is necessary to take measures related to the conditions of each of them.

Landslides are one of the most important geological hazards that cause significant damage to rural and urban settlements around the world every year. One of the factors influencing the occurrence of landslides is tectonic activities, including faulting, which, by creating weak surfaces in mountainous areas and on the slopes of highlands, reduces the resistance of the rock and soil mass and leads to slope movements.Shear zone of the Kushak fault and on the material of an ancient landslide. The bedrock of the village consists of conglomerate and marl with Gypsum lenses. Approximately one year after the Rudbar- Manjil earthquake in 1369, gradual slope movements began to occur in the Aliabad village area. These movements were triggered by the depletion of water in the village's springs and old aqueduct. During rainy periods, the intensity of slope movement increased, leading to accompanying damage. The aim of this study is to investigate the correlation between the landslide in the village and the activity of the Kushak fault.

Through examination of geological maps, satellite imagery, field observations, and geophysical studies, the location of the Kushak fault in Aliabad village was identified and confirmed. Along the Kushak fault, there are two springs and the main well of an old aqueduct, which experienced reduced flow or drying up following the 1369 Rudbar-Manjil earthquake.

Further studies revealed the presence of another fault located 600 meters south of the Kushak fault, on the downstream slopes of the village, with a tensile mechanism. This fault is associated with numerous springs that also experienced decreased water supply following the 1369 earthquake.

Geoelectrical studies indicated soil saturation up to a depth of 25 meters, indicating that the alignment of the Kushak fault and the F2 fault (identified in the southern slopes of the village) coincided with the occurrence of the Rudbar-Manjil earthquake, leading to reduced spring outflow and subsequent slope saturation.

This paper investigates the activity of Kushk fault through field observations of landslides related to the activity of the Kushk fault and other evidence of its activity, and the location of rural settlements in the study area of the Kushk fault has been analyzed. The study area is located in Qazvin province and the Alborz structural zone along the Kushk fault between the coordinates of longitude 50.25 to 50.50. In the selected sections to study the fault activity, evidence of crushing rocks, numerous springs and many old and new landslides were observed, which describe the fault activity. According to field studies and observations, the fault zone of Kushk in the studied sections was measured at 260 m on both sides of the fault. There are a number of villages in the area of the Kushk fault, among which the whole physical fabric of Aliabad village is located on the fault zone and part of Kushk, Zarabad, Garmarud Bala, Simiardasht and Hassanabad villages are located on the fault rupture zone. To save human lives and prevent death due to surface rupture during an earthquake or landslide as a result of fault activity, it is necessary to move the villages to another point or modify the future development of the villages outside the rupture of the Kushk fault. For this purpose, in preparing or reviewing the guide plans of these villages, the shear zone designated for the Kushk fault can be considered as a criterion for the future development of villages and in determining their future development. New construction should be prohibited in the Kushk fault shear zone and it must be included in the rural guide plan.

The News about Landslide in various regions of Iran, Concerns people and the government about this disastrous phenomena. Prediction and prevention of landslides could rescue life and reduce the consumption of natural resources. Stabilization and monitoring of landslides in the rivers and dams basins can be reducing sediments amount and increase the dam life time. Noghol landslide is located in Padena's Semirom County and near the Lay Sorkh Stream (a branch of great Karoon River). Sediments carried by the river may decrease the life time of Karoon dams. Therefore Noghol landslide is very active and important in studied area. In order to investigate of Noghol landslide, Satellite surveying techniques has been used. (GPS Set with Double Frequency equipment). The monitoring network had 28 marked points (MPn) which had been constructed from concrete and armature. The displacements of control points have been calculated in a determined time from satellite surveying techniques. Calculation of displacements for Noghol landslide show that the value of vectors are very remarkable. The vectors of displacement almost distributed in surface. The largest value of displacements is 1-2 m to the down slope (to the west). The vectors of displacements was drawn in charts versus northing and easting axes. The dimensions of landslides have been recognized by engineering geological and geotechnical data. Base on geotechnical investigation lithology and structures of landslide have been determined. Also a good geological correlation between boreholes have been created and geological cross sections provided for various alignments on the site. After these explorations, limited equilibrium analysis have conducted for different condition in soil mass. Lithological investigation on the Noghol landslide show that layers have including marlly limestone and clay with highly weathering decomposition. In the superficial layers conglomerate and alluvial deposition observed from zero to 7 meter in depth. After 7 meter alluvium, marlly layers occurred from 7 m to 14 m with highly weathering and mechanical destruction. The Fault system which has been sheared conglomerates in top of Noghol landslide. In fact the shearing of sediments cause to increase weathering through deep layers. Weak layers in the geological profile have important role in mass movements. Saturation of soil mass after seasonal precipitation is a main reason decreasing the soil strength parameters (c and Φ). Soil classification was done by laboratory equipment. Also the soils class was determined by the unified system. There are two type of soil in Noghol landslide including: GC, and SC-SM. The sliding surface on the SC-SM is in 14 m from surface. The stability analyses for landslide have been performed using limit equilibrium method. During Noghol landslide evaluation, stability analyses have been performed for different water table cases and seismological conditions was considered. Finally suitable methods for landslide stabilization have been presented. Saturated soils and marls in slope can reduce the mechanical strength of soils then to make instability in the Noghol landslide. In order to drain water table one series of boreholes has been designed. The direction of boreholes are revers from natural ground slope and the length of them have exceeded through the slide surface. Also stream rehabilitation was anticipated with accordance by details the end of paper

This study investigates landslides occurred in Chahar Mahal – Bakhtiari Province in Iran, using a probability analysis for describing landslide mechanism. Two case studies of landslide in this province (Naghan – karoon 4 Road) are analyzed using software analysis and empirical methods.The mountainous topography, various geological structures, crust mobile zones and humid climate can trigger geological hazards including landslides in Chahar Mahal – Bakhtiari Province. Identification of the landslide area is important for site selection and development planning of human settlements and infrastructure within the landslide prone regions. Landslide prone areas can be identified through landslide susceptibility zonation maps. This paper describes a method to identify those slopes that are vulnerable to landslides through the statistical analysis of geological data.
The landslides statistical data was collected in the Landslide Department of Forests Range and Watershed Management Organization of Chahar Mahal- Bakhtiari Province. This statistical data was recorded in the period of 1987 to 2014. During this period 319 landslides were detected and recorded. In this study the landslides of Chahar mahal and Bakhtiari province have been analyzed base on the watershed and sub watersheds, and their impact levels. The probability analysis of this data is used for describing landslide mechanism.
A high frequency of landslide events can be linked to the geographical and climatological condition in Chahar Mahal and Bakhtiari province, which is a mountainous and rainy region. Aside from these factors, the lithology, stratigraphy and geometrical design of roads also affect on landslide events. A number of landslides in the study area (Naghan – Karoon 4 road) and stabilization methods that are used for slopes are described. Considering the location of some of the landslides in the vicinity of Deh Kohneh and Gandom Kar villages and the possibility of life-threating landslides, a comprehensive study is conducted for investigating these landslides and suggesting stabilization methods for slopes. Important causes of landslides in Naghan- karoon 4 slopes are water runoff and marl and clay layers in slopes.
Almost all landslides of the Naghan – karoon 4 Road affect surrounding villages and human settlements. This study suggests a number of stabilization methods for soil and rock mass slopes based on the software analysis (Geoslope software and stereographic analysis) and field observations. Stabilization methods for Naghan – karoon 4 slopes include retaining structures, surface and subsurface drains.
In geographic areas with limited data availability, where there was a fundamental need for land-slide hazard information, a combination of landslide inventory and topographic data can provide an effective estimate for landslide susceptibility. Some of the methods of slope stabilization such as slope weight reduction for decreasing trigger forces are not useful for all cases of landslides. Based on result of analyses the water pore pressure in soil mass and impermeability of marl layers are main causes of soil movement. Utilizing drainage systems for draining water pore pressures can reduce displacements in landslides. In order to drain water table of slope, we need to install screen and perforated polyethylene pipes to the horizontal boreholes. Usually a layer of nonwoven geotextile wrapped around pipes can prevent filling the pores in polyethylene pipes. This function of geotextiles filtration can increase the life time and quality of drainage boreholes. Another type of drainage systems is superficial channels. The construction of channels to direct run off water from slops has also been prevalent.The depth and width of these channels is 1.5 m and 2.5 m respectively for a trapezium form in channel section. Superficial channels should have been waterproofed by concrete or bentonite in order to prevent water infiltration in slops.