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Protect Your Foundations With Earthquake Drains
Make Earthquake Preparation Part of Your Construction Plan
CNC Foundations always makes safety our first priority. Whether it’s safety on the worksite or making your structures safe for the future, we always have your best interests in mind.
An Effective Method to Reduce Liquefaction of Soil
Earthquake drains are a ground improvement technique used in granular soils in earthquake-prone regions where there is potential for liquefaction. The ground shaking associated with an earthquake will drive up the water pressure in granular soils, causing the earth to temporarily lose strength. This can lead to large ground movements and the collapse of structures on these soils.
Earthquakes can lead to soil liquefaction, in which soil takes on water and turns into a thick liquid—like quicksand. This can lead to landslides, bearing capacity failure, lateral spreading, and settlement that can cause structural damage to buildings, bridges, and dams.
To mitigate liquefaction potential, geotechnical engineers can install earthquake drains to give the water a path to escape during a seismic event, preventing the buildup of water pressure in the soil matrix.
What Is an Earthquake Drain?
Earthquake drains are prefabricated vertical drains made of a perforated pipe wrapped with a geotextile filter fabric. These drains have a high flow capacity that helps water dissipate, reducing build-up of excess pore pressure in soils below the water table.
The earthquake drain’s filter fabric is fine enough to stop loose sand and soil from entering the drain. Groundwater can still enter and exit the drain during and after an earthquake, respectively.
The drains, which range from 3 to 8 inches in diameter, are installed in a grid pattern across the area to be treated. The depth of the drains is dependent upon the depths to which liquefiable soils have been identified, and the allowable seismic induced settlement, with depths typically ranging from 20 to 50 feet. Some earthquake drains projects require thousands of these drains.
Saturated Soil Can Lead to Bearing Capacity Failures
Soil liquefaction from an earthquake can turn granular soil into quicksand if below the water table, which can have devastating effects on the ground above, affecting its load-bearing capacity and the structural stability of nearby structures. Earthquake drains are installed to provide a route for water to escape during an earthquake event, which prevents water pressure from building up and the soil liquifying. This can improve the IBC design site class and eliminate the potential for a failure associated with the liquefaction of the soils.
In addition to mitigating liquefaction hazards, earthquake drains also:
- Decrease seismic settlement
- Stabilize the ground surface and slopes
- Prevent lateral spreading
- Speed up the consolidation of liquefiable soils
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Common Uses for Earthquake Drains
Earthquake drains can be used to prevent damage to many significant structures, including:
- Roads and highways
- Bridges and overpasses
- Railways
- Lake and river dams
- Commercial developments
- Residential buildings
- Airports
- Harbors
Earthquake Drain Installation
To install an earthquake drain, engineers drive a vibro probe, also known as an insertion mandrel, made of steel pipe into the ground. The drain is placed into the mandrel and driven down to the intended depth, vibrating the soil as it is installed.
Once the drain is installed, the steel probe is then pulled back out. The anchor plate stays in the soil so that the earthquake drain has a place to rest. The mandrel needs to vibrate during installation and extraction to aid in soil densification, which leaves less space for groundwater to enter during an earthquake.
Benefits of Earthquake Drains
There are several ground improvement techniques for geotechnical engineering projects, including vibro replacement, vibro compaction, dynamic compaction, wick drains, wet soil mixing, and stone columns. Geotechnical engineers often combine one or more of these techniques with earthquake drains.
Allow us to improve the conditions of your soil and keep your structures safe for the future.
Earthquake drains are particularly useful because:
They are cost-effective. Not only are earthquake drains a cost-effective choice on their own, but they can also replace more expensive ground improvement options like vibro-replacement columns or soil mixing.
They are cleaner. Because earthquake drains are installed with a vibrated mandrel, the installation process is not nearly as invasive as the installations of some other options, and the resulting spoils are minimal.
They are safe. Thanks to the clean installation process, earthquake drains are a safe choice during and after installation.
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