<p><p><figure id='attachment_3505' style='max-width:745px' class='caption aligncenter'><img class="wp-image-3505 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Cross section schematic showing a typical section of a mass stabilization of a peat foundation under an embankment in Finland." width="745" height="530" /><figcaption class='caption-text'> Typical section of trial embankment in Veittostensuo, Finland showing mass stabilized peat with column stabilized clay layer (after Jelisic and Leppanen 1999).</figcaption></figure></p><p><h2>Project Summary/Scope:</h2>The project is a trial peat stabilization project under an embankment along Highway 12. The trial was part of a Finnish Road Administration project to create a peat stabilization method. The field trial began following promising laboratory results of increased strength and improved deformation properties of peat and clay. The upper peat layer was treated by mass stabilization and column stabilization through the clay layer provided additional support.</p><p>Subsurface conditions consisted of a 3 to 5 meter-thick peat layer underlain by a soft clay layer (down to a depth of 18 m).</p><p>The most suitable stabilizing agents and mix quantities were determined in the laboratory at the beginning of the project. The binder used for mass stabilization was a 50-50 mix of ground granulated blast furnace slag and rapid-setting cement at a binder dosage of 250 kg/m³. The binder used for the deep-mixed columns was a 50-50 mix of ground granulated blast furnace slag and lime at a dosage of 100 kg/m³.</p><p>A total of 500 m3 of peat was stabilized in blocks to a depth of 3 meters. Deep-mixed columns 15 meters deep (700-mm diameter) were installed in the clay layer at a 750-mm center-to-center spacing to create 2000 linear m of deep-mixed columns. The stabilized area was covered with a 0.5 m precompaction embankment and then raised to 1.5 m and 2.5 m, representing final highway embankment heights. After some time, the embankment height was reduced to 1.5 m to simulate the removal of a preloading embankment.<br><h2>Performance Monitoring:</h2>After construction, the strength development and deformation characteristics of the soil were monitored. Shear strength values varied between 40 and 150 kPa 30 days after stabilization (design strength was 50 kPa). Total settlement was measured between 300 and 400 mm after 6 years, in agreement with compression predicted in the laboratory. Settlements essentially stopped following the lowering of the embankment height from 2.5 m to 1.5 m.<br><h2>Project Technical Paper:</h2>Andersson, R., Carlsson, T., and Leppanen, M. (2001). “Hydraulic Cement Based Binder for Mass Stabilization of Organic Soils.” Proc., United Engineering Foundation / ASCE Geo-Institute Soft Ground Technology Conference, ASCE, Netherlands, pp. 158-169.</p><p>Jelisic, N. and Leppanen, M. (1999). “Mass stabilization of peat in roadway and railway construction.” Proc., International conference on dry mix methods for deep soil stabilization, Stockholm, pp. 59-64. Lahtinen, P. and Niutanen, V. (undated). “Development of In-Situ Mass Stabilization Technique in Finland.” 6p.<br><h2>Date Case History Prepared:</h2>December 2014</p></p>