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On the surface of earth crust, movement of rock mass, sediments and soil is known as landslides. In general landslides do occur in rainy season. During this time cloud bursts and landslides occured in different districts of Uttarakhand and in many parts of the state along with new landslides some of the old landslides have also reactivated. Following this about 55 people died in Uttarakhand during 2018 rainy season. During this time some of the hydro-electric power project had destroyed, roads were closed and many villages became disconnected with the main road, and caused the loss of property in lakhs. Present paper embodies detail descriptions of landslides have been given in different districts that occurred during rainy season of 2018 in Uttarakhand.

Landslides are very common geological hazards which occur in Himalayan region mostly during monsoon season. It may be caused either due to natural factors such as rainfall, lithology, geomorphology, seismicity, geological structures and slopes, and anthropogenic factors such as road widening, blasting, deforestation, construction of houses etc. The present studies of landslides have been carried out along the National Highway-7 from Devprayag (N 30 0 08'34.80" E 78 0 35'45.60") to Pali (N 30 0 10'04.80" E 78 0 37'22.80"). The detail geological and structural mapping has been done on 1:10000 scale. Rocks along the road are phyllite and quartzite and at some places river bed materials are also present. Maximum landslides are present in phyllite rocks. During the field work five landslides (L1 to L5) have been observed along the road with locations N 30 0 08' 44.77" & E 78 0 35' 47.60"; N 30 0 09'01.37" & E 78 0 35'51.85"; N 30 0 08'47.95" & E 78 0 35' 56.60"; N 30 0 08' 43.92" & E 78 0 36' 9.36" and N 30 0 09' 51.45" & E 78 0 37' 1.62", respectively. These landslides are debris slide, soil creep and debris fall type. It affects road and at places houses. In the present work detailed analysis of landslides and their causes have been observed. Active landslide, potential landslide and safe zone have been identified. These landslides occurred at moderate to steep slopes in which gravitational action is playing an important role. The main causes of the L1 landslide are the presence of highly fractured and weathered rocks and toe cutting by the river. The causes of L2 to L5 landslides are base cutting of the mountain for widening of the road, and another important factor is the water infiltration into the overburden during rains and consequent increase in pore water pressure within the overburden. For safety measure at L1 cemented wall &wirecated wall are present, and netting, cementing and anchor hold mitigation methods are also used. In the present studies remedial measures have been suggested for each landslide.

<p>Slope stability analysis is essential for sustainable development since rock slope failure can destroy infrastructure and road networks, threaten public safety, cause economic setbacks, etc. Slope failures are mainly confined to hilly terrain across the world. Himalayan mountain belt, the youngest and tectonically active mountain chain, is highly vulnerable to landslides due to complex lithological and structural variability. It requires a detailed field and laboratory investigation to understand the causes, mechanism and behaviour of slope failure. The main objective of this study is the detailed stability analysis of a rock slope located near North Almora Thrust (NAT) in the Pithoragarh district of Kumaun Himalaya along National Highway-09, Uttarakhand, India. The current study uses a multi-parametric approach which includes the kinematic analysis of slope, analysis of rock microstructures and their relation to meso-structures, the effect of microstructures on rock strength and geochemical analysis to understand the influence of mineral properties on rock strength. The stability of the slope was evaluated based on the limit equilibrium method (LEM) and finite equilibrium method (FEM). To imitate the actual field conditions, the slope model was simulated under static and dynamic settings for saturated and unsaturated conditions. The slope consists of intercalations of dolomitic limestone and phyllite with uniaxial compressive strength (UCS) of 55 MPa and 20 MPa, respectively. The Rock Mass Rating (RMR) of the rocks of the slope depicts that the rock mass quality is ‘poor’, and Slope Mass Rating (SMR) analysis illustrates that the slope is partially stable. Rock microstructural study discloses the development of strong foliation in the phyllite, which serves as the seepage for groundwater percolation. Therefore, an increase in pore pressure along these foliations can decrease the overall strength of the rock, inducing slope failure. The effect of the microstructure orientation on the rock strength was also examined for the slope. It was observed that an increase in the intensity of rock microstructures brought on a drop in rock strength. Shear sense indicators observed in the thin sections confirm the existence of the thrust zone. The slope stability analysis based on LEM and FEM revealed that the slope is critically stable in dry condition, but may  become unstable when considering dynamic and saturated conditions.</p><p><strong>Keywords:</strong> Himalayas, Slope stability, RMR, SMR, Geological Structure, Kinematic Analysis, LEM, FEM</p><p> </p>

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