Soiled Plans: (spring / summer 2014 newsletter)
Case Synopsis: The subject retaining wall was a 2-tiered wall that ranged from 8 to 10 feet for the lower tier and 6 to 8 feet for the upper tier. The wall, which was mechanically stabilized, was constructed out of block material and had georgic to retain the soil behind the wall. Within 1 to 2 years of being constructed, the retaining wall failed.
Expert Analysis: A geotechnical analysis on the soil material and condition, and wall construction was done to assist in determining why the wall failed. A geotechnical analysis was prepared to determine whether the wall was designed correctly, whether there was proper oversight, and if it was constructed in accordance with the approved drawings. During the investigation, it was found that insufficient soil data was collected and analyzed – as a result, the wall was designed from soil parameters that were not consistent to the actual soil conditions.
Furthermore, the soils retained an excessive amount of water, which caused the soils to move and fail the wall. The design did not account for the free draining of the water. It was further determined that the wall failure was not a result of one specific thing, but t a number of issues including not properly analyzing the existing soils conditions, not allowing for water that penetrated the soils to freely drain, and to designing and constructing the retaining wall from incorrect soils information and data.
Result: The case settled.