Lateral load tests of drilled shafts behind an MSE wall – research with KDOT and KU


DBA is part of a research project involving laterally loaded drilled shafts and MSE walls with the Kansas Department of Transportation (KDOT) and the University of Kansas. The ultimate goal of the study is to develop rational design procedures for situations where drilled shafts are constructed near or adjacent to MSE walls. From the study proposal:

Drilled shafts used to support sound walls and other structures are often constructed near the facing of mechanically stabilized earth walls (MSE walls) due to right-of-way constraints or other limitations. Suppliers and designers have expressed concern that lateral loads from the shafts may be transferred to the wall facing, causing excessive deformation. Procedures currently available to design MSE walls to resist internal lateral loads are very conservative isolating the shafts from the backfill or the using extremely large shafts to minimize deflection have been adopted. These designs are very expensive and in some cases lead to other problems. Results from this research project are expected to lead to much more cost effective designs on subsequent KDOT projects. We expect that the results will lead to improved national design standards for this type of construction as well.

Seven test shafts and 6 reaction shafts were constructed at the tests site, with some of the shafts socketed into the underlying limestone and shale bedrock. All of the test shafts were located within the reinforced backfill zone of the wall, varying the distance between the shaft and the wall face. Single shafts and shaft groups were loaded laterally. The wall face, reinforcing geogrid materials, and backfill were instrumented to measure loads, strains, and movements. The shafts were built with inclinometer casings to allow measurement of shaft deflections using an inclinometer during the tests. Many of the materials and construction work for the wall and shafts were made as in-kind donations by various companies, including Tensar who supplied the geogrid. KDOT Maintenance personnel perfomed most of the construction work and provided support for the load tests.

The tests took place between November 5th and 16th. I was on site the 12th through 16th to observe the tests, provide oversight, and assist Chris Kohlhof of AFT with running the tests. You can see a photo album or slideshow of some photos from my time at the site by clicking below.



Dr. Bob Parsons, P.E. of the University of Kansas Department of Civil, Environmental and Architectual Engineering will concentrate on analyzing the data concenring the wall and the backfill. DBA will analyze the lateral load tests data to derive p-y relationships for shaft design and will prepare a report on the load tests that includes design recommendations.


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