Application of Instrumentation Monitoring and Observational Methods in Construction of a Large Embankment on Soft Ground

Adverse soft ground conditions are encountered in a recent project in South America, in which a large embankment up to 25 m high is being constructed over very soft forest floor consisting of peaty soil and soft clay extending as much as 10m below the ground surface. To tackle the immense challenges, a battery of geotechnical monitoring instruments was deployed during the ground treatment and the staged embankment construction to provide continuous monitoring of the response of the foundation soils under the fill load increments as well as the deformations of the embankment. This paper presents some selected findings and lessons learned from the analysis of the instrumentation monitoring data leading up to a slide incident in which part of the embankment under construction was massively cracked. This case demonstrates that, with a well-planned instrumentation scheme, dedicated construction observation effort, and careful assessment of the monitoring data, the observational method can be successfully applied to assess the deformation and stability of embankment on soft ground, help identifying potential construction risks, and guide the construction activities accordingly.