The Purpose of Earthquake Drains

Ground Improvement

• Depending on the location, ground layers may consist of different types of soil, such as clay, sand or silt. The type of rock a particular soil originated from determines the type of soil found in an area. As different types of rocks can exist in different ground layers, soil composition can vary from layer to layer. Land areas with high sand concentrations or underground sand layers, can undergo significant shifts when earthquake activity occurs. In effect, ground shifts can cause sand particles to liquefy or pour into nearby underground areas. When this happens, ground surface structures can shift along with the surface terrain. Earthquake drains help to maintain ground surface support for buildings, roads and embankments by redirecting soil movements when seismic activity occurs.

Identification

• Earthquake drains appear as perforated, plastic tubes that range anywhere from 1 1/2 to 10 inches in diameter. These tubes are inserted through targeted soil layers. A tube’s exterior surface consists of a geotextile lining that allows soil and water materials to filter or drain through. Geotextiles are made up of synthetic fabrics of varying weaves and textures. Different types of geotextiles create different effects in terms of how soil and water materials move through them. As different conditions exist for different areas of land, uses for earthquake drains can vary. Drain or tube sizes coupled with geotextile options enable earthquake drains to solidify, drain or support existing soil layers depending on area needs.

Soil Movement

• Soil environments consist of soil particles, water and air. In effect, soil layers may have a porous structure, with the size of the pores varying according to the type of soil particles present. Sandy soils contain large soil particles, which allows for a more porous structure than clay or silt-based soils. Seismic activity creates pressure within porous soil layers, and disrupts water and air materials. This process can cause soil layers to collapse or shift. Earthquake drains open up drainage paths within soil layers and strengthen potentially weak or unstable areas within the soil.

Soil Compression

• Underground layers made up of different types of soil, such as sand versus clay, may require a compressing or compacting effect in order to create a stable ground surface. Specialized earthquake drains, known as prefabricated vertical drains, or PVDs, are designed to compress soil layers in addition to redirecting shifting soil particles when seismic activity occurs. By compressing targeted soil layers, PVDs enable layers to settle or stabilize quicker than what occurs through natural processes. Soil compression effects help to reduce porous regions within soil layers, which work to further stabilize ground surface terrains.