Embankment Replacement on SH 575 (BF 76482)
Client: Alberta Transportation c/o Stantec Consulting Ltd. |
Location: 16 km East of Carbon, AB (NW 20 & SW 29-29-21 W4M) |
Type: Geotechnical, Quality Assurance Testing |
Project Budget $3.5 Million |
Consulting: $60,000 |
|
Slope stability and erosion problems were identified at the 20 to 26 m heigh roadway embankment site in the 1990's. The existing embankment was found to be in a state of eminent failure (FS # 1) due to the steep slopes (2H:1V) and low strength of the clay fills. Saturated zones were encountered throughout the fill suggesting that water was entering the embankment from upland areas increasing pore pressure within the embankment and reducing the shear strength of the embankment fill.
The result was a combination of creep and sliding in the outside face of the embankment and subsidence along the crest which caused cracking in the asphalt surface. Long term prospects were that the complex slope failure would continue due to the further saturation of the fill with the possibility of a large mass creep failure that could take out the road.
Initial efforts to stabilize the embankment slopes were compounded by the discovery of dispersive clay soil within the embankment fill. The design recommendation was adopted to remove the entire existing embankment and culvert within the coulee, prepare the exposed valley walls to allow placement of the embankment and culvert with an engineered fill.
The final design included a resized culvert embedded in a granular drainage blanket that extended up the coulee walls to protect against excessive seepage and soil piping into the embankment and control measures for surface drainage to reduce erosion and piping caused by high ditch flows over the weak clay and dispersive clay soils common to the area.
ParklandGEO undertook the geotechnical investigation of the site, provided geotechnical recommendations for the embankment reconstruction, assisted with the embankment design, developed the safe work procedure to deal with the local slope and performed Quality Assurance testing for the 2006 embankment and road reconstruction
