Nilex Construction is a completely operational contracting group, capable of managing any earthquake drain project, regardless of size or location. Our crews have installed earthquake drains throughout North America and internationally.

Developing the Design: Investigation

The effective design of an earthquake drain project involves the compilation of soils and geotechnical earthquake data, which is used to determine the depth and spacing of the drains, as well as the level of densification required to obtain the appropriate safety factor. Earthquake drain systems can be easily designed using the program FEQDrain: A finite element computer program for the analysis of the earthquake generation and dissipation of pore water pressure in layered sand deposits with vertical drains.

FEQDrain will accommodate soil layering with differing parameters. For each soil the information required consists of: layer thickness, permeability in the horizontal direction, permeability in the vertical direction, coefficient of volume compressibility, gamma total, number of cycles to cause liquefaction (Nl), relative density, coefficient of pore pressure generation (usually taken as 0.7), and initial excess pore pressure at top and bottom of the layer.

The design earthquake is defined by the equivalent number of cycles due to earthquake loading and duration of strong shaking.

• Soil Borings
• Cone Penetrometer Test’s (CPT’s) and Standard Penetration Test’s (SPT’s): Either CPT or SPT data can be used to determine soil parameters required for Earthquake Drain design. CPT data has the advantage of being easily presented in electronic form, which can be electronically manipulated for direct use in the FEQDrain program. Normally, sufficiently accurate parameters can be derived from this data so that further testing is not required.
• Sampling: If SPT data is used, it is generally necessary to obtain soil samples for grain size analyses. Permeability is then estimated based on the grain size distribution. It should be noted that Nilex has patented methods of obtaining permeability from in situ tests on actual production Earthquake Drains when the ultimate in precision is required.
• Testing: Although testing procedures are available for determining the coefficient of volume compressibility, these are expensive and seldom performed. Instead published values are often used, or values can be back-calculated to match the results of the Tokamatsu Seed (or other) method.
• Site History
• Utility Locations

Developing the Design: Design Parameters

Here are some questions you'll want to answer to obtain design parameters for your earthquake drain system: 

• What is the magnitude of the design event and the peak ground acceleration (PGA)?
• How much residual settlement can you tolerate?
• Cost of repair vs cost of treatment – insurance issues.
• Complicating issues
• Multiple soil conditions.
• Unusual loading conditions.
• Very deep drains.
• Pore water discharge/storage issues

Implementing the Design: Specifications

• Materials
• Earthquake Drain
• Pore water discharge/storage
• Structural reservoirs
• Gravel/Sand Blanket
• Depth to water table (has direct bearing on required depth of reservoir)
• Installation
• Equipment Requirements
• Data Logging
• Payment
• Monitoring
• Settlement
• Drain depth