Three-dimensional numerical simulation has been used to examine the stability of a road cut slope in the Himalayan region of India. The site investigation has been carried out to collect data and rock samples. The geometry of the slope has been prepared in the numerical software to represent the actual slope and the major joints sets were mapped in the numerical model as per their dip/dip-direction observed at the site. The behaviour of the discontinuity sets was modelled using a Mohr-Coulomb slip with residual strength. The normal stiffness of the joints was calculated from rock mass deformation modulus, intact rock young's modulus and joint spacing. Similarly, the shear stiffness has been calculated. The results show the total displacement of 10.6 cm with a total velocity of 0.43 m/s for the same block in the numerical analysis.
The instability in the hilly region is a severe problem around the world. Natural factors such as rainfall, earthquakes, freeze-thaw cycles and human intervention for an instance unplanned roadway construction, rail-networks and infrastructures are responsible for instability. The Himalayan region in India is young and seismically active with complex geology. The stability of the slope depends on the occurrence and type of discontinuity exist in the rock mass. The set of discontinuities can be responsible for the instability whereas a single joint rarely directs the stability in the slope. The discontinuities are responsible for heterogeneity in the rock slope. The instability in the slopes along the major highways can cause abruption of traffic, injuries or fatal accidents. So, the stability assessment of these slopes is necessary for safety.
The stability assessment can be carried out in many ways using various rock mass characterization techniques, limit equilibrium techniques, and numerical modelling. The distinct element method (DEM) is one of the many numerical modelling methods which is used to assess the stability of the rock slope. It was developed by Cundall (1988). In this study, the stability of the road-cut slope has been examined by the three-dimensional distinct element code (3DEC). It has the capability to include a large number of rock joints explicitly. In the DEM, the rock mass is considered as an assembly of different intact rock blocks. The joints between intact blocks are treated as boundary conditions. The displacement and contact force at the boundaries of stressed intact blocks are evaluated from the movements of intact block assembly in previous steps. This translational and rotational movement of block assembly is caused by the application of body and boundary forces. This method works on Euler's equation of motion for rigid bodies. The blocks in the model are either deformable or rigid, and the deformation of the block is modelled by internal discretization of finite difference elements (Lanaro et al. 1997). A number of numerical simulations have been carried out by the researchers around the globe for different problems such as rockslide (Jaboyedoff et al. 2012), excavation of walls (Son & Park 2013), pit slope stability (Sainsbury & Sainsbury 2015), and road-cut slope stability (Verma et al. 2018).
