Geotechnical Properties of Fibrous and Amorphous Peats for the Construction of Road Embankments

Abstract

Peat deposits cover large areas in Northern Canada. Peat in the study area in Northern Manitoba has an average thickness of 4 m, with the upper half classified as fibrous and the lower half as amorphous with strong to complete decomposition. Design, construction, and maintenance procedures for new road embankments on seasonally frozen peat deposits require mechanical, hydraulic, and thermal properties of the foundation. Laboratory tests were conducted on samples obtained from a test section along a newly constructed road. Hydraulic conductivity tests were conducted at different vertical stresses to determine permeability. Thermal conductivities were determined at frozen and unfrozen states. Conventional incremental-loading (IL) odometer tests were performed to determine the compressibility and secondary compression indices of the peat layers. Constant-rate-of-strain (CRS) tests were also done to supplement the results obtained from the conventional method. Isotropically consolidated undrained (CIU) triaxial tests were carried out, and a new method of evaluating the shear strength of peat was implemented. Numerical modeling that used the measured mechanical, hydraulic, and thermal properties simulated reasonably well the performance of road embankments constructed on seasonally frozen peat. With these properties, construction and long-term performance of highway embankments and future infrastructure development on peat foundations can be reasonably predicted, leading to effective construction and maintenance procedures.