Effects of u-shaped subgrade concrete panel on subgrade deformation

Abstract

California Bearing Ratio of subgrade lesser than 5% requires a treatment work either by stabilisation or strengthening method. In this study, the latter concept was chosen for the application of U-shaped Subgrade Concrete Panel as it is a method that has less disturbance to the native soil. As the name suggested, this U-shaped Subgrade Concrete Panel is a precast U-shaped concrete panel to be installed into the subgrade soil in an inverted direction. It is divided into two sections; the horizontal panel and vertical webs beneath the panel. Hence, the objective of this paper is to present the effect of applying the U-shaped Subgrade Concrete Panel into subgrade soil with a CBR value of less than 3%. There are 3 sizes of control panel used; square panel with dimension of 150 mm x 150 mm x 50 mm, 300 mm x 300 mm x 50 mm, and 600 mm x 600 mm x 70 mm, and 6 types of U-shaped Subgrade Concrete Panel; square area of 150 mm x 150 mm, 300 mm x 300 mm, and 600 mm x 600 mm. While the depth of the U-shaped Subgrade Concrete Panel varies from 100 mm, 125 mm, 150 mm, 200 mm, 270 mm, and 370 mm. The static load test was applied to centre, edge, and corner point of the panel, as to study the interlocking effect when it is subjected to a localised load. As the study was conducted in the laboratory, the condition of the subgrade soil fully controlled by monitoring the moisture content and the density of the soil in the test box. Settlement of the subgrade soil after compactions was observed and recorded as part of the initial conditions before the static load test was applied to the panel. After the compaction of the subgrade, it shows that a longer web section had caused lesser settlement compared to the control panel, indicating better resistance towards lateral movement under the U-shaped Subgrade Concrete Panel.