Study of Relationship Between Soil Mechanical Characteristic and Landslide in Forest Road Route (Case Study: Chafroud Watershed Guilan Prov.)

Road construction in forest area is interfering in natural environment of forest and itis caused to derange it. So, studying of soil mechanic and its characteristics is a need. Itis useful to choose the suitable road construction technique. This research was carriedout because of landslide problem in forest road. Investigation of some mechaniccharacteristics of soil and its effect on mass movement was studied. For this researchtwo zones of road side were selected in two parcels (No. 105 and 107) were located onChafroud district in Guilan Province. Then surveying, Length measuring, Min. andMax. Width, height and slope of soil movement in two zones were measured. Fourboreholes were dug (two in moved area and two in stable area) and the soil sampleswere sent to soil mechanic laboratory. Some mechanical testes like soil texture, liquidand plastic limits (Aterberg Limits) were done and so the results show that in movedsoil the texture was SC and for stable area were CL and CH. The process of moisturechanging in soil was investigated. Absorption of moisture with fine soil, undesirabledrainage and stimulation of road construction cause landslide in study area.