Gopika Rajagopal

Ongoing Research Work : Development of Grouted Helical Soil Nail System

A state-of-the-art literature survey on helical soil nails revealed that even though the helical system aid in quick and easy installation, soil disturbance due to rotary motion and associated reduction in interface shear resistance is still a concern. A potential scope is present for improving the disturbed soil surrounding the helical nail due to installation. Furthermore, numerical modelling of helical soil nails considering the installation effect and a detailed study on the development of an analytical model for predicting the helical nail pullout capacity from installation torque is yet to explore.

It is expected that grouting can improve the surrounding disturbed soil around the helical nail and can enhance the pullout capacity. This research thus attempts to develop a new grouted-helical soil nail system to overcome the inherent issues associated with the helical and conventional soil nails and increase the pullout capacity. The constructability and pullout capacity of the grouted-helical soil nail will be analyzed through experimental and numerical studies. Further, a suitable analytical model will be developed for the prediction of pullout capacity from installation torque.

Previous Work : Hybrid Back-to-Back MSE wall upon Rainwater Infiltration

Back-to-Back Mechanically Stabilized Earth (MSE) walls have become an integral part of the transportation infrastructures, especially as ramps, bridge approaches, etc. The permeability, strength and constructability attributes of well-graded granular soils have rendered them as the most suitable fill material for MSE walls. However, the scarcity of such good materials compels the usage of locally available soil with high fine content (marginal fill) having low permeability and high plasticity characteristics, which can cause excessive wall deformation or even failure, if not adequately designed and constructed. This study focused on the assessment of overall performance of back-to-back MSE walls with a trapezoidal marginal fill zone surrounded by a near optimal amount of select fill (i.e., hybrid-fill) as an alternative to the wall with select fill only. The behaviour of hybrid-fill wall at the end of construction and during heavy rainfall infiltration were investigated through finite element modelling and compared with fully select fill and fully marginal fill walls. The study revealed that the overall performance (i.e., horizontal and vertical deformations, reinforcement tension, and factor of safety) of the hybrid-fill wall with 31–47% select fill is much better than that of fully marginal fill wall, especially during the extreme rainfall infiltration scenario. The response of this hybrid configuration is even comparable with that of fully select fill wall, suggesting the proposed hybrid-fill wall as a stable as well as cost-efficient alternative system in locations where sufficient quantity of well-graded soil is not readily available.