Merit Engineering has extensive experience in geotechnical investigations for new road and road improvement projects having designed more than 35,000 feet of road. In particular, we have designed more than 17,000 feet for City of Blaine. The City of Blaine is located in the northern most part of the Whatcom County, by the U.S. and Canada
border. The soils in the Blaine area are unique in western Washington in that blue clay and silty sand are dominant. The soils originated from glacial drift with the groundwater table being high and near the surface in most places, so that the soils are mostly soft. Design of cost effective road sections for this type of soft soil is, therefore, a challenging task.
We conducted geotechnical engineering investigation for about 3,000 feet of new highway. The road was to be built for Canadian Trucks which are about 35% heavier than the U.S. trucks. The project site is very unique; the soils have a thin layer of crust about 1′ to 2′ thick, under which is very soft muddy clay. These soil conditions imposed very difficult construction conditions. We provided rigorous technical support to the design engineer for both the construction documentation and the construction phase support. Because of this the project went smoothly and completed on time within its budget.
In road improvement projects, we provide both subsurface soil and groundwater investigations and evaluations on existing road conditions with Benkelman Beam test, Road Rater test, and FWD (Falling Weight Deflection) test. We also conducted analysis for road pavement section design including overlay, new road, and road reconstruction and widening.
175 Road Rater deflectometer measurements were performed in Blaine. The Road Rater test is basically evolved from the Benkelman Beam test which measures road deflection induced by a loaded truck. Deflections of the roads were analyzed. 70 test borings were conducted to investigate existing road pavement and subsurface soil conditions of the project road sections. Merit then preformed laboratory soil index tests for soil classifications and preformed engineering analysis. With the site soil conditions, Merit Engineering successfully developed recommendations for either widening, overlay or reconstruction of the road sections.
A typical problem of concern about a road built in this area is associated with the silty fine soil undergoing frost-thaw action. When temperatures fall below freezing, the pore water inside the soil becomes ice and consequently increases the volume of the soil. When the temperature increases, the ice melts and greatly increases the water content while at the same time decreases the strength of the soil. Road pavements especially suffer serious structural damage as a result of the frost-thaw action when heavy vehicles drive on the pavement during the frost-thaw. Merit was able to defeat this problem by recommending the pavement thickness be at least as thick as the frozen ground depth and by recommending an adequate drainage system be installed to prevent water from flowing into the road bed.