Effect of stress history on CPT and DMT results in sand

In order to investigate the effect of stress history on in-situ test results in granular sediments, a series of CPTs and DMTs are performed on Busan sand prepared in the calibration chamber. K_D is found to be the most sensitive to the stress history among CPT and DMT measurements. E_D and q_c are observed to be similarly affected by the stress history and, therefore, the E_D-q_c relation appears to be almost independent of the stress history. The K_D-D_R relation established without considering the stress history is likely to overestimate the relative density of OC sand. It is shown that the existence of the pre-stress of the granular sediment can be indirectly recognized by an estimation of the relative density larger than 100% when using the K_D-σ_vσ-D_R relation suggested for NC sand. Although q_c/σ_vσ-K_D/K₀ and E_D/σ_vσ-K_D/K₀ relations are heavily influenced by the stress history, q_c/σ_mσ-K_D/K₀ and E_D/σ_mσ-K_D/K₀ relations are observed to be independent of the stress history. Based on these relations, charts to evaluate the K₀ value from q_c and/or DMT indices are developed for both NC and OC sands. The design chart based on E_D/σ_mσ-K_D/K₀ and E_D/σ_vσ-K_D/K₀ relations is expected to be practically useful as the usage of this chart requires only DMT indices. The developed design charts are applicable to Busan sand but different sets of equations and charts may be developed for other sands.