Geofoam Block in Soft Soil Embankment Applications: A Review

The major issues of building a road over soft soils are low bearing capacity and large settlements. The challenges of road construction on soft soils are enormous, so innovative and environmentally friendly methods are required. Geofoam is a type of lightweight infill material and was already used in Norway in road construction applications in 1972. Using Geofoam reduces compacted fill by 40%, less excavation required and less pulverization of native soil making this a time-saving and economically and environmentally viable solution. The purpose of Geofoam backfill is for lightweight backfilling, reducing soil pressure. Geofoam blocks can be used as a substitute for soft soil fill or as fill on top of soft soil as subgrade for pavement. This paper discusses the latest developments on the various applications of Geofoam blocks as backfill in soft soils presented based on information provided by the author.


Introduction
Pathways used for ground transport are frequently in soft soils, so there are issues with infrastructure development [1].The soft subgrade caused a problem in the construction of the road.The problems that often occur in embankments on soft soils are embankment stability problems and a big consolidation settlement problem in a relatively long time [2].Indonesia has an area with soft soil of about 20 million hectares (the percentage of Indonesia's land area is about 10%) [3].Various subgrade improvement methods such as vertical drain improvement, reinforcement with geosynthetics, dynamic methods, and chemical stabilization.Other methods to consider include lightweight embankments using Geofoam [4].
EPS Geofoam blocks are produced from polystyrene particles through an expansion and melting in an automatic molding machine by adding steam [5].Geofoam is a geosynthetic material made from foam.Geofoam is particularly suitable for use in geotechnical engineering due to its low density (11.2 -45.7 Kg/m³) compared to soil density, simple and quick implementation, thermal insulation, and resistance to water absorption [6].Geofoam EPS has been used in various Geotechnical projects since 1960, both as lightweight embankments.The first use of geofoam on a highway was in Norway in 1972 [7].The dimensions of geofoam used in civil engineering applications are 0.5, 1.0, 2.5, and -3.0 m.The strength properties of the material vary relatively linear, with the material densities of 20 kg/m³ having a compression 100 kPa strength at 10% strain [3].When geofoam was first implemented as a lightweight infill material ini Norway in 1972, It, was shown in a research project that road embankment with EPS can sustain repeated loads on the pavement, and the properties material do not deteriorate over time.Soil settlement, overcome by replacement of embankment with geofoam.The use of geofoam blocks in civil engineering applications has been widely adopted in various countries [8].
A geofoam application that has been investigated is for floating road construction embankments [3], reducing embankment settlement on roads , for soil retaining walls, to reduce earthquake load on retaining walls, reducing the stress on the soil retaining structure due to dynamic loads [9], slope stability, and latest applications of lightweight culvert structures [10].
EPS geofoam in civil engineering has improved quite dramatically in the last four decade.The advantages including reduced embankment settlement and reduced lateral earth pressure on retaining walls [11].The paper discusses about of geofoam in geotechnical engineering, particularly embankments on soft ground, based on case studies in several countries, and the potential use of EPS geofoam for road embankments on soft ground.

Geofoam Properties and Geofoam Properties
Geofoam is a material that has a closed-cell structure made in a factory with an internally expanding material that produces a closed-cell and contains gas [12].Geofoam has the appearance of Styrofoam, a type of man-made polystyrene material, in the form of white round granules with a diameter of 1-2 mm [13].Polystyrene granules expand using expanding material, with expanding polystyrene only forms 2% of the volume form, the other 98% is just air, so this is what makes geofoam a very light material [12].Polystyrene granules and geofoam blocks are shown in figure 1. Geofoam plan life is between 70 -100 years.The term for synthetic geotechnical materials produced in a gas expansion process, which results in a closed-cell texture, has been attached to geofoam since the early 1990s [12].Geofoam is suitable for construction use as it is more rigid than Styrofoam [12].According to the ASTM [6], Geofoam density ranges from 11.2 -45.7 kg/m³.Material properties required for each type of Geofoam (Table 1).Geofoam blocks conceptually share the same principles as geosynthetics in groundwork design that require internal and external stability considerations.Stability includes displacements/deformations, service failures, Serviceability Limit State (SLS), and Ultimate Limit State (ULT) collapse failures [12].The durability of geofoam is that it is non-biodegradable and chemically.Polystyrene is hydrophobic, EPS closed cell structure prevents water absorption into each expanded polyhedron [13].
Geofoam dimensions of 2m x 1m x 0.5m and 8m x 1 m x 1m, lightweight and easy to transport and install, saving construction time and costs [6].The advantages of geofoam also have disadvantages, Geofoam has a light density so that it can float when submerged in water.The resulting lift can be counteracted by ensuring the geofoam is below the water level, or by anchoring the geofoam to neutralize the buoyant force [6].Another drawback is that if geofoam is exposed to petroleum, its strength will be lost because it will turn into liquid.This can be overcome with petroleum-resistant geomembrane [7].
In zone 1, can be concluded that the behavior are linear and elastic up to 1% strain, called elastic limit stress.Zone 2 in the stress-strain graph is calling yielding.The yielding zone occurs at 3% -5% strain.After the yielding zones, linear winding occurs again.Creep testing of Geofoam based on literature [12], If the working stress produces a strain ≤ 0.5%, then creep can be ignoring.If it produces a strain of 0.5%-1%, then creep is still within normal limits for light embankment applications.If it results a strain ≥ 1%, then creep can increase and become excessive for light backfill applications.
The bulge that occurs at the bridge with caused differential drop in the bridge approach plate [11].Alternatives include replacement of embankment and excavation materials, deep soil blending, mechanically stabilized retaining walls, geosynthetic reinforcement, and using lightweight backfill by replacing it with Geofoam [12].
The primary use of geofoam blocks is as a lightweight backfill material, especially for road construction purposes [6], and for railways.Geofoam is used to minimize construction loads on soft soils and solve settlement [6].A cross-section of the road using geofoam with slope is presented in figure 3 [12].
UDOT and UTA (department of transportatioan and transit authority) used Geofoam backfill for several roadways in the Salt Lake Valley [11].Figure 4 shows the proposed design for a 2.5 m wide construction section.The geofoam layer is 1200 mm thick on top of the subgrade, followed by 50 cm (sand layer), 15 cm granular subbase, 15 cm dry unreinforced concrete, and 31 cm pavement [12].
Geofoam for rehabilitation of 12,2m high bridge abutments on US highway 67 at SH174 in Cleburne, Texas [4].Figure 5 Cross-section detail of Geofoam Embankment on Bridge Abutment.Some literature and research has been beeing done in wich the Geofoam blocks are used to obtain consistent subgrade conditions [7].NHCRP provides studies to develop design guidelines for geofoam application in slope improvement and soil reinforcement projects [12].Literature [7] explains that the use of geocells over Geofoam has a good effect when the pressure undergone by Geofoam is excessive.Geocells are installed on top of geofoam based on soil thickness.As soil thickness decreases, geocell effectiveness increases [7].
Gravity loading on the topmost layer of Geofoam blocks has the highest vertical stress due to vehicle live load and pavement system dead load shown in figure 6 [12].The raft file foundation with geofoam backfill reduces ground settlement.
The performance of the thick embankment soil using geofoam due to cyclic loading.
A geofoam layer thickness of less than 20 cm can reduce the ability of the pavement to resist rutting due to loading.

[4]
Field test Dynamic loads Geofoam qualifies as a material that induces small deformations under load.

Figure 3 .
Figure 3.A cross-section of the road using geofoam with slope.

Figure 4 .
Figure 4. Cross section detail of traffic lane and geofoam block layer on subgrade.

Figure 6 .
Figure 6.Relative normalized stresses in geofoam due to gravity load .

Potential Use of Geofoam for Road Embankment on Soft SoilTable 2 and
Table3list the research conducted using geofoam blocks as reinforcement for road pavement and bridge approach slabs to overcome settlement.The research includes laboratory experimental testing, field testing, and numerical simulation of soil samples reinforced with geofoam blocks.

Table 2 .
Overview of Geofoam Applications on Soft Soils Previous Studies.

Table 3 .
Overview of Geofoam Application on Soft Soil Numerical Study.