Field-Scale Column-Supported Embankment Test Facility

Column-supported embankments (CSEs) have seen increasing use in recent years where new embankments or widening of existing embankments is required over soft ground. The primary advantages of CSEs are more rapid single-phase construction and protection of adjacent facilities and embankments, but their use is limited because of lack of consensus on CSE design procedures. Investigations into CSE performance in the literature include bench-scale testing, centrifuge testing, case histories with instrumented test sections, numerical modeling, and a few examples of field-scale research test sections. This paper describes a field-scale CSE test facility that employs a unique approach where expanded polystyrene geofoam and its subsequent dissolution are used to model the soft soil beneath the CSE. The properties of the geofoam are similar to those of soft clay, although the geofoam layer is thin. The geofoam is dissolved after embankment construction using an environmentally friendly solvent to represent a worst-case scenario where there is zero soft soil support. Some field applications can approximate this condition. Based on an extensive literature review, the authors believe that this is the first published use of geofoam for temporary support of a column-supported test embankment, where the geofoam is later dissolved to remove support between columns. In addition to investigation of CSE behavior, the facility, instrumentation, and test concept have broader applications for investigation of other arching phenomenon including: localized loss of support beneath portions of other geotechnical structures such as mechanically stabilized earth walls, sinkhole mitigation, tunneling, and mining engineering. This paper focuses on description of the CSE test facility, materials, test procedures, and instrumentation. The results from one of the CSE tests are presented to illustrate the capabilities of the facility and data that can be collected. Future publications will present results from the entire CSE test program and make recommendations for CSE design.