A CPT-Based Index for Evaluating Ground Improvement

The degree of ground improvement is evaluated to determine if the final results in the field meet project design criteria. This evaluation is typically based on values of cone penetrometer tip resistance correlated to an equivalent relative density. It is difficult to consistently apply empirical correlations to soil modified by densification. Therefore, a method to determine the expected degree of improvement, free of correlations, would provide improved design and quality control information for contractors and consultants. The Improvement Index for Densification (I_d) is presented that quantifies the degree of ground improvement by densification methods. I_d is related to the specific energy of penetration and is computed from cone penetrometer tip resistances measured before and after improvement. Results presented for eleven case histories show that I_d is sensitive to variations in soil texture and initial density.