During an earthquake, loose sandy soils have the potential to liquefy, causing great damage to structures supported by the soil. One solution is to densify the loose soils and/or provide a drainage path for the dissipation of pore pressures before they reach dangerous levels. In many cases Earthquake Drains can provide the necessary liquefaction mitigation.
Earthquake drains consist of high flow capacity prefabricated vertical drain wrapped with a geotextile fabric. Typically the diameter is about 75mm (3 inches). The core is tightly wrapped with geotextile filter fabric, selected for its filtration properties, allowing free access of pore water into the drain, while preventing the piping of fines from adjacent soils. The geotextile wrap is also very durable, and able to withstand the handling and abrasion that occurs during installation. Several core designs and fabric types can be utilized to suit a variety of drainage applications and soil classifications.
Earthquake drains are installed by vibrating the insertion mandrel during penetration and withdrawal. Typically, the insertion mandrel consists of a heavy-gauge steel pipe with three equally spaced fins to aid in transmission of vibrations to the adjacent soil. The vibrations result in some densification of the granular soils, assisting in the liquefaction mitigation.
Liquefaction mitigation achieved with Earthquake Drains can be beneficial for support of embankments, reduction of lateral spreading from seismic loading, containment of densified ground, support of floor slabs in certain conditions, liquefaction mitigation of mine tailings, and reducing seismic deformations of pile groups. Combined with other ground improvement techniques, earthquake drains can be applied to big box stores, nominal loading conditions, mid-rise buildings, tanks, ports, and hydraulic fills.