Monitoring and Stabilization of Landslide Using Survey and Engineering Geology Data (Case Study: Noghol Landslide PadenasSemirom County)

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