Quality Control of Pavement Subgrade and Base Materials Using Advanced Field-testing Techniques

·        Modulus-based quality control provides a more realistic representation of pavement structural behaviour than density alone because it directly reflects stiffness and deformation response. ·        The LWD proved to be a rapid, portable and economical method for evaluating deformation modulus of subgrade and base materials and showed good agreement with PLT trends. ·        Relative compaction increased deformation modulus, while increased moisture content reduced dynamic resistance, cone index and LWD modulus in the investigated soils. ·        For triaxial geogrid-reinforced Soil-1, the optimum embedment was 50 mm (u/a = 0.17). At 97% relative compaction and 0.15 MPa contact pressure, E_LWD was 29.45 MPa compared with 18.50 MPa for unreinforced Soil-1. ·        The LWD-based MIF at the optimum geogrid position was 1.42, while the corresponding PLT-based MIF was 1.37. The LWD and PLT MIF relationship achieved R² = 0.962. ·        In reinforced aggregate layers, triaxial geogrid also performed best at 50 mm embedment, but the stiffness gain was more moderate because the aggregate layer already had relatively high stiffness. ·        Geocell reinforcement increased the deformation modulus of Soil-1 by approximately 45.7% at the reported optimum configuration, demonstrating the benefit of three-dimensional confinement. ·        Geocell reinforcement did not provide a significant stiffness improvement in the investigated aggregate layers, showing that geocell effectiveness depends strongly on infill material and particle interaction. ·        Chemical stabilization with lime and cement substantially improved weak-soil strength. The reported optimum stabilizer contents were 6% lime and 8% cement, with strength increasing with curing period. ·        The reported regression relationships between rapid field parameters and conventional strength measures produced R² values from 0.78 to 0.99, supporting the use of calibrated correlations for rapid quality control. ·        An integrated QC approach combining density, LWD, DCP/DSCP, PLT and laboratory strength tests can improve test coverage, identify weak zones and support mechanistic–empirical pavement evaluation.

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