Evaluation of Subgrade Bearing Capacity (CBR) And Subsurface Layer On Treated Subgrade Using Grouting Water Cement In The Tuban-Babat-Lamongan-Gresik National Road

Abstract

One of the causes of the damage that occurred on the Tuban–Babat–Lamongan–Gresik national road is the subgrade condition which has a low CBR value. From the results of the soil investigation, the CBR value is less than 3.0%. To evaluate soil bearing capacity (CBR) and the condition of the subsurface layer after grouting, laboratory and field scale tests were carried out. Laboratory testing by modeling CBR test objects according to field density with injection variations in the quantity of grouting material and water-to-cement ratio (w/c). Variations in the quantity of grouting material injected were 3%, 5%, and 7% of the dry unit weight of the soil samples tested with variations in the ratio of water-to-cement w/c=1, w/c=1.5, and w/c=2. While field testing is carried out by acquiring Ground Penetrating Radar (GPR). The greatest increase in the CBR value occurred in variations in the injection quantity of grouting material at 7% and w/c=1. In the soil sample Sta 37+850 the initial CBR value of 1.41% increased to 2.47%, but the soil bearing capacity of the resulting subgrade was still weak because the CBR value is less than 6%. From the analysis of the GPR data at Sta 37+850, can be seen on the radargram that the grouting material has increased due to back pressure because it cannot penetrate the subgrade layer so the grouting material spreads on the aggregate layer, and exits through the grouting holes at other points on the asphalt surface.