Lane widening solutions are commonly used both to meet increasing traffic demand (Ludlow et al., 1993; Serridge and Synac, 2007; Kim et al., 2013) and to construct safer approach and exit lanes (Deschamps et al., 1999). Constructing an embankment to add an additional lane along an existing highway alignment creates an engineering problem that requires consideration of total settlements both in the existing highway embankment and in the newly constructed widening embankment, as well as differential settlements along the widening fill itself (Han et al., 2007; Kim et al., 2013). To address this problem, lightweight fill materials, geosynthetics, piles, replacement of unsuitable soils with engineered fill, preloading, stone columns, prefabricated vertical drains, and similar techniques are used to prevent total and differential settlements (Han et al., 2006; Serridge and Synac, 2007). By constructing lane widening embankments using geofoam blocks, which are a lightweight fill material, total settlements in both the existing alignment and the newly added embankment, as well as differential settlements along the added embankment, can be prevented. Compared with conventional ground improvement techniques, this method is more economical and can be completed in a shorter construction period. In Japan, 47.5% of the total 5.3 million m³ of geofoam block embankments constructed between 1985 and 2010 were used in lane widening projects (Kubota, 2011). Geofoam block lane widening embankments can be constructed either with a trapezoidal cross-section (Figure 1 and Figure 2) or with vertical faces at a ninety-degree inclination to the horizontal (Figure 3), similar to conventional geofoam block embankments.
The construction stages for geofoam block lane widening embankments are the same as those for conventional geofoam block roadway embankments. For the construction of a lane widening embankment composed of geofoam blocks, the existing embankment slope must be stable; if the slope is not stable, the necessary stabilization measures must be implemented before block placement begins (Figure 3).
REFERENCES
- Ludlow SJ, Chen WF, Bourdeau PL, Lovell CW (1993) Phase II – Embankment widening and grade raising on soft foundation soils. FHWA and INDOT Report No. FHWA/IN/JHRP-92/1 9. Indiana Department of Transportation, Indianapolis, IN, USA
- Serridge CJ, Synac O (2007) Ground improvement solutions for motorway widening schemes and new highway embankment construction over soft ground. Ground Improvement, 11(4): 219–228
- Kim TH, Kim TH, Kang GC (2013) Performance evaluation of road embankment constructed using lightweight soils on an unimproved soft soil layer. Engineering Geology, 160: 34–43
- Deschamps RJ, Hynes CS, Bourdeau P (1999) Embankment widening design guidelines and construction procedures. FHWA and INDOT Report No. FHWA/IN/JTRP-99/4. Indiana Department of Transportation, Indianapolis, IN, USA
- Han J, Oztoprak S, Parso RL, Huang J (2007) Numerical analysis of foundation columns to support widening of embankment. Computer and Geotechnics, 34(6): 435–448
- Kubota T (2011) Case history of EDO-EPS method in Japan. Paper presented at the 4th international conference on geofoam blocks in construction applications, Lillestrøm, Norway, 6–8 June 2011