Design and development of a laboratory model for generation of dynamic stress in soil

Various full-scale model testing methods adopted by researchers to study response of track structure and the supporting soil against train-induced vibrations are advance and accurate and, however, are very expensive. Besides, standard approaches to study stresses in the subgrades are based on train dynamic loads derived by multiplying static load by an impact factor. Hence, the objective of this study is to develop an innovative, accurate, safe and economical scaled laboratory setup of a locomotive wheel that will generate the desired dynamic effect in the supporting track foundation. To achieve this, an electric drive system, comprising of a motor, a graduated circular disc and a load device, was designed and developed in the laboratory to the scale of 1:30. A representative soil sample from the site was collected in the tank and compacted to its maximum density. The displacement values obtained by integrating accelerometer values from the experimental work are consistent with the displacement outcomes of the finite element simulation with less than 10% variance, which therefore reinforces the dependability of the results. Further, in order to gauge the rate of settlement of the subsoil over the designed life of the track structure, cumulative plastic deformation based on Li and Selig method was derived for the given soil with high plasticity. The soil below the non-ballasted tracks, over the designed life, exhibited settlement levels 7 times higher than the defined permissible limits as per standard codes. It is therefore that the study recommends the adoption of suitable soil remediation techniques before the superstructure is constructed.