Relations between Penetration Resistance and Cyclic Strength to Liquefaction as Affected by K_C-Conditions

The effectiveness of ground improvement by the sand compaction pile (SCP) method is generally evaluated through penetration resistances, such as cone resistance (q_c) and N-values of the standard penetration test (SPT), measured at the center point in-between piles before and after the pile installation. However, it is known that the penetration resistance of the ground adjacent to piles does not only increase, but the lateral stress increases as well, resulting in increase in the resistance to liquefaction. Therefore, in order to evaluate the effectiveness of the ground improvement on compacted soils, it is necessary to quantify the effect of K_c-values on the penetration resistance and the resistance to liquefaction. In this paper, based on the results of SPT and CPT performed in chamber box in the laboratory, the relationships between penetration resistance, resistance to liquefaction and relative density were re-examined, and the influence of K_c was investigated. Although the results indicated that generally the resistance to liquefaction increases with increasing K_c-value, little difference was noted when the density of the deposit was high. Based on the results, recommended charts incorporating the effect of K_c were proposed.