Dry Soil Mix Column Shear Panels Constructed beneath Lost Lake Dredge Disposal Island Levee

Abstract

The United States Army Corps of Engineers (USACE) manages the Houston Ship Channel dredging operations, required to maintain the flow of barges within the ship channel. Disposing of the dredge materials requires the creation of disposal islands throughout the channel. A levee surrounds each island to contain the dredge material during a storm event, preventing spillage into the ship channel, which would inhibit movement of barges through the channel and shutting down all commerce. In 2009, the USACE led a project to increase the existing levee heights at a number of the islands to increase dredge storage capacity, including the Lost Lake Dredge Material Placement Area (DMPA). Lost Lake's current levee elevation of EL. +8.2 m (27.0 ft) required a change in grade to EL. +10.9 m (36.0 ft) an increase of 2.7 m (9 ft). During construction, the levee failed several times over a 640.0 m (2,100 ft) stretch. This portion of the levee had a history of failure. The poor soils beneath the levee footprint in this area required stabilization prior to increasing the elevation. The design-build team designed a deep soil mix (DSM) ground improvement program, which included shear panels with overlapping dry soil mix columns, to improve soil beneath the levee with a combined shear strength of 1,000 psf. The panels were constructed at varying depths and lengths depending on the strength of the in situ soil, and were perpendicular to the levee. Dry soil mixing proved to be challenging and required very precise planning and execution because it was located on an island, but also proved to be the most cost effective method due to the remote nature of the work. The levee now performs as designed since raising its elevation to EL. +10.9 m (36.0 ft) after ground improvement.