Real-time monitoring and numerical analysis of rainfall-induced slope instability

The study of slope instability includes a detailed study of environmental conditions and soil's geotechnical and hydrological parameters. In the present study, a thorough understanding of rainfall-induced slope instability is achieved by doing real-time monitoring on an unstable slope located in Shillong, Meghalaya, India. The area selected is prone to landslides due to heavy rainfall and because it is located in the wettest place on earth. The real-time monitoring involves observation of groundwater table variation, intensity of rainfall, soil suction, and their effects on the instability of an unsaturated slope. Boring data show that even if the area is in a hilly region, the groundwater table is very high. The effects of antecedent rain on the matric suction, which indirectly affected the stability of the unsaturated soil slope were noticed. The location of the irrometers helped us in assessing that the slope stability is affected by both the matric suction developed in the unsaturated shallow soil during rainfall and that developed due to the presence of high groundwater level. The displacements along the slope are independent of each other. The results of the numerical analysis show that the slope displacement is positively correlated with the principal strain and maximum shear stress, indicating that the infiltration of rainfall has a significant effect on the stress and strain associated with displacement.