Liquefaction resulting from earthquakes causes significant damage to roadways, bridges, lifelines, and port facilities. Typically, liquefaction hazards have been mitigated by densifying the soil in-situ, but these methods are expensive and time-consuming. This study involves a field investigation of vertical composite drains (Earthquake Drains) for rapidly dissipating pore water pressures so that liquefaction and its resultant consequences are prevented. The drains are rapidly installed with a vibrating mandrel as shown in Figure 1. When liquefaction occurs around a pile or drilled shaft foundation, the upward skin friction may decrease to zero, thereby reducing the load-carrying capacity. Then, as the liquefied sand layer settles around the pile following the earthquake, downward (negative) skin friction could develop which would further decrease the load capacity. Previous field investigations (NCHRP IDEA
Project 94) suggest that Earthquake Drains could prevent these problems, but no direct evidence is presently available and this inhibits the implementation of this mitigation strategy. If drains could be proven effective, significant cost savings could be realized for deep foundation applications.
