Field Compaction Verification Using a New Surface Penetrometer (SP-CIGMAT) during Construction

The need for better characterizing the properties of field compacted soils during construction is important in ensuring the quality of construction. Standard laboratory compaction tests for soil, a three-phase material, are often viewed as the compaction standard for earthen fills. However, these laboratory tests were developed to simulate the compaction energy of a particular compactor-soil-lift combination. For this study, a field compacted CL soil (liquid limit of 42) with several properties (dry unit weight-moisture relationship, maximum dry unit weight, optimum moisture content, void ratio and air void content) was compared to the Standard Proctor (SP) and Modified Proctor (MP) tests. In the field, the CL soil was compacted at 200 mm (8-in) lift thickness using a popular compactor. Nuclear density gauges was used to measure the lift densities and moisture contents. The maximum dry unit weight of field compacted CL soil was 8 to 9 pcf higher than the SP compacted soils. All the other properties studied showed notable differences between the field compaction and laboratory compaction. The void ratio and air void contents had the highest differences in the SP and field compacted CL soil. A new surface penetrometer (SP-CIGMAT) was developed and used to evaluate compacted soil undrained shear strength (s_u) during the construction. This device can be easily attached to any construction vehicle to perform tests on compacted soils during construction. Based on the limited field data, non-linear relationship between the SP-CIGMAT deflection and compacted soil strength has been developed.