Elevated Soil Temperatures

[MSEMan]

I am working on a soil retention project in the Middle East, where we are using PET geogrids with concrete facing panels. The embankment is 7.5m high. Summer mean ambient temperatures will be on the order of 35 C, average soil temperatures will be roughly 23-26 C. Does anyone have any information on models for predicting peak soil temperatures perhaps through an energy exchange model? I am mostly concerned about temperatures at the connection to the facing panels.

 

[PEinc]

I would check with the geogrid manufacturer(s).

According to Designing With Geosynthetics, 4th edition, by Robert M. Koerner, Section 3.1.4, "Given the temperature ranges of typical environments, temperature extremes (hot or cold) should have no serious effects on geogrids. The one caution is that high temperatures can exacerbate strains arising from creep and/or stress relaxation. This requires actual testing at the anticipated temperatures, time-temperature superposition assumptions, or the use of higher-than-typical reduction factors on conventional creep information."

 

[Focht3]

I think the operative part of Bob Koerner's statement needs to be considered: Given the temperature ranges of typical environments... (emphasis added.)

I spent 59 days, 12 hours and 36 minutes in Saudi Arabia in the summer of 1976. (Do you think I wanted to go home?!) It typically reached 125 degrees F (about 52 degrees C) in the shade on sunny days. That's not the "typical" environment in the U.S., Canada or Europe.

Follow PEinc's advice - check with the manufacturers. You may also need to have special testing done that mimics the likely site conditions.

Let us know what you find out!

 

[PEinc]

Bob or George Koerner at Drexel University's Geosynthetic Institute may already have the information needed.

Phone: 610-522-8440
Fax: 610-522-8441

robert.koerner@coe.drexel.edu

 

[Godla]

MSEm

One of the important determinant of creep is the temperature effects. Creep of the geogrid shall be affected by elevated temperatures. creep tests are typically done bewteen 25 deg c.

The facing connection temps and soil ambient temps near connection can go beyond 25 degc in the gulf area. This is applicable for many parts in India too. Hence the geosynthetic creep FOS must be adjusted accordingly based on temp superimposition graphs available from the manufacturer.

However, for PET geogrids the glass transition temp is high, and therefore may not be affected at elevated temps.

Somnath Biswas
Reinforced Earth - India