Forensics and Failures

An important if unfortunate aspect of all engineering is the study of what went wrong, failures and forensic engineering. For geotechnical engineering this often involves landslides, damage to structures from settlement or other foundation problems such as collapsible soils or swelling clays.

On June 2, 2014, the Delaware Department of Transportation closed a bridge on I–495 that was leaning and out of plumb.
Articles

How Could a Pile of Dirt Cause a Major Interstate Bridge To Tilt?

October 20, 2015 Dennis M. O'Shea Comments Off on How Could a Pile of Dirt Cause a Major Interstate Bridge To Tilt?

On June 2, 2014, the Delaware Department of Transportation closed a bridge on I–495 that was leaning and out of plumb.[Editor] The Delaware Department of Transportation (DelDOT) had a major problem on their hands after a bridge on I-495 was leaning…one side of the bridge was 18 inches higher than the other.  The culprit?  A pile of fill adjacent to the bridge was loading soft soils beneath.  So what do you do about it?  In this contributed article by Dennis M. O’Shea, bridge engineer in the FHWA Delaware Division Office, he describes the problems faced by DelDOT, the causes, and how they fixed it.  The article originally appeared in Public Roads Magazine, and is republished here with permission. [/Editor]

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ASTM No. 57 Stone
Articles

The Curious Case of No. 57 Stone

May 12, 2014 Katherine Witt Comments Off on The Curious Case of No. 57 Stone

ASTM No. 57 StoneThe American Society for Testing and Materials, or ASTM, No. 57 stone is often used as sub base fill material below road surfaces and buildings. It is a fragmented stone with angular edges and is regularly utilized as a drainage layer when used with geotextile fabric. Although the material is touted by many as "self-compacting," excess voids left from zero compactive effort in locations with little confinement may not eliminate the possibility of future settlement. What happens when the environment above the No. 57 stone causes it to settle?

[Editor] Read on for the answer to this interesting question in the case of settlement of a structure at the University of North Carolina at Chapel Hill. The contributed article by Katherine Witt describes how URETEK Mid-Atlantic used their high-density polyurethane resin to stabilize the No. 57 stone beneath a settled foundation as well as lift the surrounding slab back into place. [/Editor]

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