I 15 Utah Road Plan and Profile Drawings

Use of Geofoam for I-15 Reconstruction in Common salt Lake City, UT

Steven Bartlett, Utah Department of Transportation, Common salt Lake City, UT
Dawit Negussey, Geofoam Enquiry Center, Syracuse University, Syracuse, NY
Marking Kimble, Wasatch Constructors, Salt Lake Metropolis, UT Michael Sheeley, Geofoam Enquiry Center

The geofoam fill up monitoring for this project is a joint project of the Utah DOT and the Geofoam Enquiry Center.

Project Clarification

The Utah Department of Transportation (UDOT) in conjunction with Wasatch Constructors is in the process of reconstructing Interstate I-fifteen in Common salt Lake Metropolis, Utah. The $1.5 billion pattern-build contract consists of modernizing I-fifteen from 600 North to 10600 South, approximately 27 kilometers of urban interstate (Figure 1). Construction began in May 1997 and will exist completed by July, 2001 in time for the 2002 Winter Olympic Games.

Figure i: I-xv Alignment and Geofoam Placement Areas in Common salt Lake City.

The projection essentially widens the existing I-15 corridor with an additional full general-purpose lane, a high occupancy vehicle (HOV) lane, and an auxiliary lane between ramps on both north and southbound sides of the interstate. The project will replace all existing bridges with 144 new structures. Interchanges volition be constructed at 400 South and 600 North for improved downtown admission, and single point urban interchanges (SPUI) will reconfigure near remaining freeway/arterial intersections (Effigy one).

To accomplish the widening of the roadway within the limits of correct of way, the reconstruction of the I-fifteen corridor will brand use of approximately 160 mechanically stabilized globe (MSE) walls to construct "vertical fills." As part of this time critical projection, several innovative foundation treatments and embankment construction methods accept been used. These methods are being employed in areas where conventional solutions are costly or time consuming. The most innovative of which is the use of EPS blocks for calorie-free-weight fill.

Geofoam Applications

One main awarding of geofoam is to minimize settlement of cloak-and-dagger utilities. Many existing utility lines traverse areas of raised mainline or ramp embankments. These utilities consist of high pressure gas lines, water mains, and advice cables, which must remain in-service during construction. MSE embankments were predicted to induce main settlements of up to 1 meter, exceeding strain tolerances for these cached utilities. However, when the soil mass of the MSE walls was replaced past low density geofoam the predicted settlements became minimal. This application of geofoam enabled buried utilities to remain in-place, eliminating possible expensive interruption, replacement, or relocation. Figure 2 shows a photograph of a completed geofoam embankment, earlier installation of the tilt-upward fascia console wall at the 100 Southward utility corridor.

Figure 2: A Geofoam Embankment at 100 Due south Utility Corridor Crossing of I-15.

Another important apply of geofoam on the I-xv project was to amend the stability of embankments. At some bridge locations high embankments were required and the associated safety factors against base failure were low. Such embankments are ordinarily constructed with geotextile reinforcement and stage loading that crave several months of delay to allow excess pore pressure dissipation and shear strength gain. Construction of embankments with geofoam provided higher safety factors confronting instability and allowed the construction to proceed within the disquisitional path for the bridges. Figure 3 shows a typical bridge abutment with geofoam placed behind the abutment wall.

Figure 3: Typical Bridge Abutment with Geofoam Backfill.

This application of geofoam eliminated stability concerns at the span abutments and reduced the construction time by upwards to 75%. In add-on, geofoam approach fills induce essentially no lateral pressure on retaining structures provided the soil to geofoam fill transition is maintained at close to a self supporting tranquility angle, equally shown in Figure four.

Figure 4: Details of a Typical I-15 Project Geofoam Fill up.

Subsurface Conditions

Extensive geotechnical investigations were conducted along the I-15 corridor by UDOT and the design-build team. Much of the Salt Lake Valley is underlain by alluvium/colluvium from the nearby Wasatch Mountains that have interfingered with relatively thick deposits (five to x g layers) of lacustrine silt and clay. The lacustrine deposits originate from the Great Salt Lake and its fresh water lake predecessors that were mutual in the Dandy Bowl during Tertiary fourth dimension. Cone penetrometer (CPT) logs and sampling from borings reveal interbeded sand layers within the lacustrine deposits, which mark numerous transgressions/regressions of ancestral lake shores, probably due to climatic changes. The lacustrine soils are generally depression plasticity clays (CL) with some layers of depression plasticity silts (ML) and loftier plasticity clays (CH).

Extensive deposits of compressible lacustrine clays and clayey silts are located in the northern segment of the I-15 in the downtown area. These deposits have a maximum thickness of approximately 25 meters and are saturated due to the shallow groundwater table (less than ii m). Typically, these lacustrine sediments begin consolidation on the virgin compression curve when approximately 2 to iii meters of embankment is placed. MSE walls of eight to 10 meters in elevation, typically experience about 1 grand of settlement due to primary consolidation of the clayey soils. In society to expedite backlog pore pressure level dissipation and primary consolidation, prefabricated vertical (PV) drains were placed beneath many embankments. Without PV drains, the lacustrine deposits require about 400 to 600 days to consummate about of the principal consolidation. Consolidation times can be accelerated to nigh 100 to 200 days by the installation of PV drains, which have been typically placed on i.5-meter triangular spacing to a depth of about 25 meters. Surcharging was extensively used to minimize the corporeality of expected mail service-structure settlements. Typically, surcharging was 30 to 40 per centum of the design embankment height, which fabricated the height of some of the temporary embankments (borrow + surcharge) up to 10 to 14 meters above original ground. Even so, due to its extreme low-cal weight, geofoam embankments do not trigger primary consolidation nor result in excessive secondary consolidation settlements. Geofoam embankments were designed to produce "nix net load" on the foundation soils. This was achieved by full load compensation or removing a volume equal to the weight added by the new construction.

Standard Drawings and Specifications

Standard Drawings and specifications were adult for geofoam applications on the I-15 corridor by Wasatch Constructor's Design-Build team. Figure four shows details of a typical section through a geofoam fill up. The fascia panel, roadside barrier equally well every bit details for a utility trench and piping are also shown. Tabular array 1 lists all the geofoam standard drawings that are currently available. Copies may be obtained by asking from the Research Sectionalisation, Utah Department of Transportation, 4501 South. 2700 W., Salt Lake City, Utah, 84114-8410.

Table i: Geofoam Standard Drawings

Drawing Number	I-15 Corridor Standard Program Title
CS-42-ane, CS-42-2	Take hold of Bowl Down Bleed in Geofoam
CS-43, CS-78	Superlative - Geofoam Walls
CS-44, CS-79	Geofoam Wall Panel Details
CS-45, CS-fourscore	Geofoam Wall Restraint Details
CS-46, CS-81	Geofoam Wall Course Beam Details
CS-47	Geofoam Wall Connection Details
CS-48-1	MSE Geofoam Conform Detail
CS-48-2	Load Distribution Slab Parapet Wall Detail
CS-49-1, CS-49-2, CS-49-three	Geofoam Coping at Bridges
CS-50	Geofoam Installation at Abutments
CS-51, CS-52, CS-77, CS-91, CS-92	Typical Geofoam Section
CS-53	Load Distribution Slab Bleed

Cloth Backdrop

The I-15 Reconstruction Team specified geofoam with no more than five percent regrind content. Although both Type Viii and Type II geofoam (ASTM C-578) were approved, only Type VIII geofoam was used (Table 2). The blocks installed on I-15 were 0.8 m high by 1.2 g wide past 4.9 m long. The blocks, as manufactured, met the specified ± 0.five percent dimensional and 5% flatness tolerances and trimming was non necessary. The overall pattern considered the nominal compressive resistance at 10 percent strain of xc kPa for the specified Type VIII geofoam under ASTM-C-578. Bodily tests performed at a strain rate of 10 percent per min on a series of standard 50 mm side cube samples, Figure 5, signal the density consistently exceeded the xviii kg/m³ of the specification. The initial lag in the stress strain curves is due to uneven contact and must exist adapted. Corrected initial Young'southward moduli from these tests were in the range of 2.9 to five.1 MPa. The compressive resistances at adjusted v and x percentage strain were on average 97 and 111 kPa, respectively, with both exceeding the specification level for Type VIII geofoam in ASTM-C-578.

Table 2: Material Specification for the I-15 Projection.

Physical Property (ASTM Test Procedure)	Type VIII Value	Type II Value	Tolerances
Density (D1622)	18 kg/m³	22 kg/m³	Minimum
Compressive Resistance (D1621)	90 kN/one thousand^two	104 kN/m²	Minimum @ yield or 10 percentage axial deformation
Flexural Force (C203)	208 kN/m^two	276 kN/m²	Minimum
Water Absorption (C272)	3	3	Less than % by volume

The range of densities and compression resistances at 5 percent strain represented in Figure 5 are shown in Figure 6.

Figure 5: Stress-Strain Curves for Blazon VIII Geofoam, fifty-mm Samples at 10% Strain Rate.

Figure vi: Compressive Resistance versus Geofoam Density.

The best fit line, equation (1), predicts compressive resistance for other densities of geofoam. A similar expression is given, equation (ii), in the new European Standard (1998) for compression resistance at x percent strain.

Sigma_d = vii.3*D - 47 (1)
Sigma_d = 9.four*D - 76 (2)

Where Sigma_d is compressive resistance in kPa and D is density in kg/m³. The 5 percentage criteria by and large results in a compressive resistance that is most 10 percent lower than that for the ten pct strain level. To limit long term pitter-patter deformation of the geofoam blocks, working stress levels due to expressionless load were express to 30 percent of the compressive resistance for Type Eight geofoam with an additional of up to 10 percent allowed for live load due to traffic. Such criteria have been used widely earlier and are believed to event in no more ii percentage creep strain in fifty years (European Standard, 1998). An alternative approach used in Japan is to limit working stress levels to compressive resistance at one percent strain (Miki, 1996). The ii methods can exist shown to exist equivalent.

Corrected initial modulus values that are derived from standard tests equally in Effigy 5, are generally also depression and over predict settlements when used in analyses (Frydenlund et al, 1996). Contempo results on big cake samples tested at Syracuse University now show that stop effects unduly influence data from small specimens. Provided the imposed stresses are confined to induce predominantly elastic strains, the deformation that occurs in the geofoam volition mostly take identify during construction and mail-construction deformation will be small. Thus the more meaningful modulus for practical purposes is the dynamic or resilient modulus. Because of the depth of pavement and load distribution of the concrete slab, stress increments that develop in the geofoam due to live loading are relatively small. Dynamic moduli from large cake samples are of the guild of more than double to triple the initial value obtained from conventional monotonic tests. Comparable initial moduli are also beginning to be observed in monotonic tests on full peak samples obtained from laboratory testing and with local measurement of deformations.

The beliefs of EPS geofoam is strain charge per unit dependent, peculiarly at college strain levels. A lower value of compressive resistance develops with decreasing strain rate. Thus the value of specifying compressive resistance at set strain level of 5 or ten percent and based on standard specimen sizes serves mainly as reference. In that location have been other projects that accept been designed on the aforementioned footing and performed well. Perhaps more than than confirming the validity of the methodology, the evidence that there have so far been no reported or documented cases of failed geofoam embankments suggests a reasonable degree of conservatism in current methods.

Interface shear strengths between geofoam blocks and betwixt geofoam and bedding sand are shown in Effigy vii. The examination results are for a range of normal stresses due to the pavement load on the geofoam. Likewise shown as a lower bound envelope is the interface friction coefficient of 0.six used in the I-fifteen design. The lower coefficients for the sand to foam interface imply failure at the interface would be localized to occur within the sand. Coefficients for both the cream to cream and cream to sand interfaces slightly subtract with increasing normal stress.

Effigy 7: Interface Coefficients for Blazon 8 Geofoam.

The load distribution concrete slab over the geofoam fill up was cast in identify. A relatively stiff adhesion bond and a rough texture develops between poured in identify concrete and geofoam surfaces resulting in a much higher interface strength than between cream to cream. In some cases, the scheduling of the load distribution slab structure vicious behind the geofoam fill completion. The geofoam surface was exposed to prolonged duration of sunlight. Discoloration and dusting of the surface occurred due to UV degradation. The effect of surface degradation on interface force between geofoam and cast in identify concrete was investigated. Samples were subjected to accelerated UV exposure in a weatherometer and field samples exposed to the 90 days specification limit were recovered. Interface strengths adamant for fresh foam, UV lab exposed surfaces and field degraded samples are shown in Figure eight.

Figure viii: Interface Coefficients for Geofoam - Cast in Identify Concrete with UV Exposure Duration.

Also shown are results for field degraded but power washed geofoam to bandage in identify concrete interfaces. On the fourth dimension calibration, the ninety days of field exposure is approximated every bit being equivalent to 50 hours of UV exposure in the weatherometer. The design interface coefficient of 0.6 that was assumed for all interfaces involving cream is too shown as a lower jump for all of the test data. Interface strengths between geofoam and cast in-place concrete subtract with the level of UV exposure and surface degradation. Power washing before concrete pouring was effective in removing the degraded surface and enabled full regain of interface strength to a value comparable for a fresh geofoam interface. Analyses indicate the interface force demand due to braking or acceleration of trucks tin be met past a friction coefficient of less than fifty percent of the design level of 0.vi. The specification requirement for covering geofoam with plastic sheeting for exposure elapsing across xc days can be relaxed. The sheeting was an additional expense and securing for protection confronting air current was necessary. If desired, reconditioning of UV degraded load bearing surfaces past power washing was a amend culling.

Barbed metallic plates or binder plates were used with the intention of developing more than interface shear resistance between geofoam blocks. However, test results performed for the I-15 Reconstruction Project indicate the plates did non provide more than resistance in one fashion loading and were even less effective on reverse loading. While the folder plates may accept helped in maintaining the blocks in position during placement, the suppliers claimed value for enhancing shear resistance was found to take been exaggerated. This determination supports the previously expressed opinion of Sanders et al. (1996).

Solvent, Fire and Insect Protection

Geofoam should be protected from potential spills of petroleum based fuels and solvents (eastward.g., gasoline and diesel fuel) and from burn. The load distribution slab, pavement department, and fascia panel wall are the primary protection against spills. However, in applications where the geofoam was placed on a side slope, a geomembrane liner (28 mil minimum) was provided. The geomembrane was specified as a tri-polymer consisting of polyvinyl chloride, ethylene interpolymer alloy, and polyurethane or a comparable polymer combination. A modified flame retardant resin was used for burn down protection. Also, borate was added to prevent insect attack and ho-hum intrusion. There has so far been no record of detrimental solvent or insect attack of geofoam fills for highway embankments anywhere. The extent and effectiveness of such pre-cautionary measures may need to be reviewed in future applications.

Textile Quality and Acceptance

The frequency of quality assurance testing was left to the discretion of the field engineer, who had the right to random sample the delivered blocks. Blocks that did not meet the project specifications upon inspection were to be rejected. The original geofoam specification stated: "any damage to the EPS resulting from the contractor'southward vehicles, equipment, or operations, shall be replaced by the Contractor." Nonetheless, as the project progressed, minor damage to many geofoam blocks was noted and the specification was revised to define acceptable harm. Much of the damage was due to forklifts making impressions in the sides of the block, or damaging or breaking off corners of the block, as the block was moved from the commitment truck or within the stockpile. One arroyo for setting a realistic acceptance criteria for geofoam blocks was to limit impairment to 1 percent by book, 5 percent in load begetting area and 20 pct of the longest side for a maximum linear dimension. If but one limit was to exist checked, the load begetting expanse restriction would be easier and more meaningful. For the standard I-fifteen blocks the surface area criteria would mean total damage of no more than than 0.3 g² (about three.2 ft^two). The harm limit would apply to one location or the sum of all damaged areas over a load-bearing surface. Damaged areas between blocks would satisfy the conditions for individual blocks but over an equivalent surface area. Such criteria would mean credence or rejection with no intermediate choice for moderate damage and repair option. Thus a damaged block either had to be cut, and then as to remove the damaged portion, or replaced with a new block.

Timely covering of geofoam later placement became an issue on the I-15 project. The specification required geofoam fill exposed for more 90 days to be covered past an opaque sheeting to forbid ultraviolet (UV) light degradation. However, some locations were not covered and surficial degradation (i.e., dusting and discoloration) of the geofoam occurred. For these areas, UDOT and the design-build team adapted a solution utilizing high-force per unit area washing of the geofoam surface. Prior to placing the load slab physical, the superlative surface of the geofoam beach was pressure washed to remove the degraded surface. No pressure washing was done on the side of the geofoam beach, where the fascia panel covers the geofoam.

Connections

For the I-15 Reconstruction Projection, the tilt-upward-console-facia wall is mechanically tied to the load distribution slab by threaded reinforcing bar placed in both elements and held together by threaded couplers. For 1 geofoam make full, which was 8 to 10 blocks high, this connexion proved to exist too rigid to accommodate some of the seating settlement inside the geofoam mass and the connection was severed at a few locales. Seating settlement of approximately 3 to 4 cm, as measured past vertical extensometers, occurred during the placement of the untreated base coarse (UTBC) and Portland Cement Concrete Pavement (PCCP) above the geofoam block and load distribution slab. Seating settlement is partly caused by pinch of a slight curvation of individual geofoam blocks. This arch, or crown, in the geofoam blocks is visible prior to geofoam placement and is produced during ejection of the cake from the mold, and later on while cake cooling. Standard process by Wasatch Constructors' cake installers is to identify each block with the crown upwards at all times. This do allows for a relatively shut fit of the block, but did not eliminate the presence of the crown, until the load of the overlying UTBC and PCCP was added. Unfortunately, the connection between the tilt-upward-console-facia wall and the load distribution slab had been made prior to the occurrence of the seating settlement. The connexion detail has at present been revised to let differential movement.

Price

Because of the nature of the design-build contract, some of the itemized material and construction costs are not readily available. Further, making a blanket cost comparison between geofoam and earthen fills can be misleading. Each state of affairs requires a complete review of the atmospheric condition and geometry earlier costs are compared. Direct costs of the foam, bedding, load slab, and facia wall must be compared to the excavation, PV drains, geotextile, fill up, surcharge and construction necessary for a particular state of affairs. Beyond the easily determined directly costs, less tangible costs must also be considered to make the comparing more than meaningful. Potential improved life bike costs to pavement, reduced construction time, elimination of utility relocation costs must be included in the evaluation. Tabular array 3 presents an approximation of costs for the installation of geofoam on the I-fifteen project. The cost summary includes all labor and materials and is averaged over all applications of geofoam on the project.

Table 3: Approximate Costs for Geofoam Installation at the I-15 Reconstruction Project.

Handling and Placement

Geofoam was manufactured and stored temporarily in the manufacturer's lots. When needed, blocks were shipped in truckloads to the chore site, unloaded, stored and installed within days of receipt. During storage, the cream was protected from wind with tie-downs or surcharge. Signs were posted to prevent exposure to open flames and petroleum fluids. Installation procedures did not allow for operation of equipment directly on the surface of the geofoam fills. Care in the treatment and installation minimized the necessity to replace damaged blocks and was monitored by Wasatch Constructors Quality Assurance/Quality Control personnel.

The bottom layer of geofoam cake was placed on a 0.2 one thousand of sand bedding. Leveling tolerances for the sand bedding and subsequent layers of geofoam were maintained at 0.01m over 3m. Blocks were placed to exist tightly fitting to reduce gaps, which were usually less than 0.02m.

Blocks were handled and placed in a diversity of methods. Some of the placement was accomplished by hand carrying or sliding the block into place. Where steep beach were involved, blocks were lifted down to the installation crews using a crane and cable suspension by auger type anchors secured in the block. Placement rates by a crew of 4 workers and a foreman slightly exceed 200 blocks per day, under optimal weather. At times, the construction schedule required both day and night shifts, which were able to place approximately 350 blocks per day (in ii shifts), nether optimal conditions, where foundation grooming was minimal.

Long Term Monitoring

Much of Wasatch Constructor's design of geofoam fills focused on reducing the impact of main consolidation settlement in the foundation soils on underground utilities. Long-term creep settlement volition also occur within the foundation soil and the geofoam fill up due to the sustained load of the pavement structure. Differential pitter-patter settlements are expected to occur between deep foundation supported bridge decks, geofoam fill areas and conventional embankments. Depending on the transition course, footstep settlements and gradual changes in pavement profile are expected. There is considerable uncertainty with available parameters for assay and design of geofoam fills. These uncertainties are best bridged through comparison and design refinement based on reliable field data. To this end, the Utah Department of Transportation and the Geofoam Research Eye at Syracuse University have installed instrument arrays to gather long-term performance data of the geofoam fills. The post-obit briefly describes some of the data gathering activities. The gathered information will be presented in subsequent reports

Magnet extensometers have been installed at a geofoam wall almost 3500 South in the foundation soil and at intervals within the geofoam make full along common vertical axes. This monitoring plan is intended to observe geofoam pitter-patter deformations over a menstruum of at least x years. At this aforementioned locale, a series of total stress cells have been installed at locations higher up, below and within geofoam fill up to detect stress distribution patterns and intensities in the geofoam beach. So far, the stress cells have recorded successive changes in stress that have taken identify with the progress of construction. Survey monuments accept also been placed in the pavement overlying the geofoam to measure the total creep deformation of the geofoam embankment and to monitor for differential settlement between the geofoam and the adjacent MSE wall beach.

A nest of thermisters volition be installed at depth intervals within the pavement department at locations that accept and do not have underlying geofoam make full. These sensors are intended to monitor and compare the relative insulation influence of the geofoam in conditioning pavement temperatures.

Also, in areas where geofoam is placed confronting bridge abutments, horizontal and vertical stress cells will be installed to measure the stress country (lateral and vertical) at the abutment-geofoam interface.

The above sensor arrays and other field performance data gathered past Wasatch Constructors will provide an excellent opportunity to verify key design assumptions and methodologies, every bit well as assess the effectiveness of structure practices on the I-15 project. It is hoped that these evaluations will in turn yield futurity design and construction guidance for geofoam construction.

Conclusion

Geofoam was successfully used as an alternative construction material for the I-15 reconstruction. Pattern and construction utilizing the very lightweight advantage of geofoam enabled settlement sensitive buried utilities to remain in service without demand for relocation or disruption. Utilise of geofoam improved the base stability of high embankments. Primary consolidation settlements were not triggered and long term settlements are expected to exist minimal for geofoam fill areas that were designed nether no net load condition. Using geofoam at disquisitional segments of the project has saved considerable time. Standard drawings have been developed and field monitoring is in progress. Experience gained at I-15 volition benefit other like projects in the futurity.

Acknowledgements

The authors are grateful for the support of Syracuse University and the Geofoam Research Center where the tests were performed and to Utah DOT and Wasatch Constructors. Mr. Ahmed Elragi performed several of the tests. The authors are grateful for his valuable assistance.

References

Typhoon European Standard, (1998). European Commission for Standardization, Brussels.

Duskov, M. (1997). EPS as a light-weight sub-base cloth in pavement structures. Ph.D. Thesis, Delft University of Engineering science, Holland.

Frydenlund, T. E. and Aaboe, R. (1996). Expanded Polystyrene -The Low-cal Solution. Proceedings of the International Symposium on EPS Construction Method, Tokyo.

Miki, G. (1996). EPS Construction Method in Japan. Proceedings of the International Symposium on EPS Construction Method, Tokyo.

Negussey, D. (1997). Backdrop and applications of geofoam. Guild of the Plastics Manufacture, Washington, D.C.

Norwegian Road Inquiry Laboratory (1992). Expanded polystyrene used in route embankments: Design, Construction and Quality Assurance. Class 482E. Oslo.

Sanders, R. L. and Seedhouse, R. L., (1994). The employ of polystyrene for beach constructions. Contract Report 356. Transportation Research Laboratory, Crowthorne, United kingdom of great britain and northern ireland

Additional Photos of the I-xv Reconstruction Project