Field Evaluation of Deformation Modulus of Geogrid and Geocell-Stabilized Subgrade Soil

In-situ testing programs are conducted to evaluate the potential use of the light weight deflectometer (LWD) device for measuring the in-situ deformation modulus of subgrade soil layers stabilized with geosynthetic reinforcement. A series of in-situ field tests are carried out on six test sections that include 1) unstabilized subgrade soil and 2) geogrid- and geocell-reinforced stabilized subgrade soil. Field measurements on the modulus improvement factor (MIF) of stabilized subgrades provide more practical and realistic results. The MIF value depends on the type, geometry, location of geosynthetic reinforcements, and characteristics of subgrade soil. An accurate and quick evaluation of MIF can help in the timely design and execution of new road networks. The novelty of the study comprises of measuring the in-situ MIF of geosynthetic stabilized subgrade soil using a light weight deflectometer (LWD) device and comparing the results with the in-situ plate load test (PLT) and falling weight deflectometer (FWD) devices for the considered test configurations. The deformation modulus from LWD test demonstrated a similar trend to the modulus values obtained from PLT and FWD. The improved in-situ deformation modulus from three different tests (E_PLT, E_LWD, and E_FWD) are found to be 29.5 MPa, 34.5 MPa and 114.8 MPa for geocell; 21.1 MPa, 25.7 MPa and 86.2 MPa for biaxial geogrid; 37.2 MPa, 29.7 MPa and 89.5 MPa for triaxial geogrid, when the geosynthetic reinforcement is embedded at a depth of 100 mm. In addition, the MIF values of geosynthetic stabilized subgrade soil for the considered test sections are found to be in the range of 1.0 to 2.5.