Unpredictability of Gradients during Preservation Phase of the Linear Constructions

On the Andimeshk-Khorramabad Road, heavy and repeated rainfalls have caused damages due to instability of the rock and earth slopes, landslide and settlement.This is resulted from the lack of attention to the engineering geology issues in the maintenance phase of the road.Presence of the Seymareh large landslide in the Tang-e-Fani pass and the passage of the road through different geological formations have caused problems in the maintenance phase due to the litho logical changes, tectonic structures, weathering and weather conditions.[5] Slope Failure Mechanism in the Unstable AreasStratigraphic, tectonic and geotechnical characteristics of rocks considering the groundwater conditions intensify the physical and chemical weathering (Ghobadi, 1993), which leads to the formation of areas prone to failure in the aforementioned road.The road has settled and slipped on an active landslip in the marl and gypsum layers of the Gachsaran Formation, between the Zal Bridge and the Poldokhtar in the Pol Tang (Pay Elm) village, under the effect of water, lithology and erosion caused by the Seymareh River that is intensified in the rainy seasons and causes damage.Changes in groundwater level accompanied with swelling of the colored marl and effects of the groundwater leading to dissolution of the gypsum layers along with the erosion of the mentioned landslide heel increases the road settlement every year and increases the movement of the underlying slippery mass.Heavy and repeated rainfalls have increased the pore pressure and decreased the shear strength along the failure surfaces and thus, one of the retaining walls, which has been designed and constructed without drain, has cut and failed along the slippery mass.The other retaining walls and existing drains were not able to stabilize the landslide.The mentioned road crosses several anticlines and synclines and considering the road conditions and the tectonic structure, the rock slopes are unstable.The