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International Conference on Case Histories in Geotechnical Engineering

(2004) - Fifth International Conference on Case Histories in Geotechnical Engineering

15 Apr 2004, 1:00pm - 2:45pm

Performance of a Highway Embankment Constructed over Performance of a Highway Embankment Constructed over

Landfill Material Landfill Material

Paul J. Lewis Gannett Fleming, Inc., Camp Hill, Pennsylvania

Jack Mansfield New Jersey Department of Transportation, Trenton, New Jersey

Syed Ashraf Gannett Fleming, Inc., South Plainfield, New Jersey

Kessi Zicko Gannett Fleming, Inc., Camp Hill, Pennsylvania

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Recommended Citation Recommended Citation Lewis, Paul J.; Mansfield, Jack; Ashraf, Syed; and Zicko, Kessi, "Performance of a Highway Embankment Constructed over Landfill Material" (2004). International Conference on Case Histories in Geotechnical Engineering. 30. https://scholarsmine.mst.edu/icchge/5icchge/session02/30

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Paper No. 2.51 1

PERFORMANCE OF A HIGHWAY EMBANKMENT CONSTRUCTED OVER LANDFILL MATERIAL

Paul J. Lewis, P.E. Gannett Fleming, Inc. Camp Hill, Pennsylvania -USA-17011

Jack Mansfield, P.E. New Jersey Dept. of Transportation Trenton, New Jersey - USA-08625

Syed Ashraf, P.E. Gannett Fleming, Inc. South Plainfield, New Jersey -USA-07080

Kessi Zicko, E.I.T. Gannett Fleming, Inc. Camp Hill, Pennsylvania - USA-17011

ABSTRACT This paper presents settlement data over a period of 12 years for two portions of a highway embankment constructed over landfill material. Construction was completed in 1989 and included dynamic compaction to limit post construction settlement. A preload / surcharge was used over a separate portion of one of the highway embankments as an alternative foundation improvement technique for the purpose of comparison and evaluation of the effectiveness of the two methods. Elevation measurements taken over a period of 12 years are presented for comparison of post construction settlement of both dynamically compacted and surcharged sections of the highway embankments. INTRODUCTION The interchange of New Jersey Route 18 with the Garden State Parkway was constructed in 1988. The alignments of the mainline roadways and connector ramps associated with this interchange traverse the former Tinton Falls Landfill. This municipal landfill ceased operation in the early 1970’s. Dynamic compaction was used to densify the landfill prior to constructing the highway embankments in order to limit post-construction settlement. For comparison to dynamic compaction, a preload / surcharge embankment was used over a portion of one embankment as an alternative soil improvement technique. Elevation measurements taken over a period of twelve years following completion of construction provide a comparison of the effectiveness of the two ground improvement techniques. The purpose of this paper is to present the elevation data collected over the twelve years following completion of construction and provide an evaluation of the effectiveness of dynamic compaction versus surcharging / preloading in limiting long term settlement of a highway embankment constructed over a municipal landfill. An evaluation and comparison of the monitored secondary compression settlements are presented. A brief description of the project site conditions, dynamic compaction process and surcharge / preload construction are presented herein. A more detailed description of the project can be found in Lewis and Langer [1994]. A plan view of the project site showing the monitoring sections and the approximate limits of the landfill is presented in Fig. 1.

SITE CONDITIONS The project grades and alignment required construction of highway embankments ranging from 3 to 9 meters in height over the landfill. The landfill material generally consists of domestic sanitary refuse with occasional deposits of organic refuse (yard waste) and construction debris. In general, the landfill material was estimated to consist of approximately 45 percent organic material. The typical depth of the landfill material varied from about 1.8 to 7.4 meters. The landfill is underlain by coastal plain deposits consisting primarily of medium dense to dense silty sand. Groundwater is located at the bottom of the landfill. DYNAMIC COMPACTION Dynamic compaction completed on this site consisted of high-energy drops with an 18,160-kilogram weight dropped from a height of 24.4 meters. Two solid steel weights with different cross sections were used for high-energy drops. One consisted of a 1.8-meter square weight while the other consisted of a 2.1-meter diameter circular weight. The weight was dropped five to ten times at each location until maximum compaction was achieved as evidenced by no increase in crater depth. Dynamic compaction was completed on a square grid pattern with a final grid spacing of 3.8 meters center to center. Craters produced from high-energy impacts were backfilled with granular material which was subsequently compacted with a low-energy ironing pass performed with an 18,160-kilogram weight dropped from a height of 12.2 meters.

Paper No. 2.51 2

Fig.1 Plan view of the project site showing the station limits of dynamic compaction and preload / surcharge ground improvements. The low-energy weight consisted of a 5.8-meter square weight constructed of solid steel. The ironing pass utilized an overlapping grid pattern. SURCHARGE / PRELOAD A portion of one of the interchange ramps (Ramp E) was selected to receive a preload / surcharge in lieu of dynamic compaction. A 1.5-meters high surcharge was constructed over the final profile grade and the embankment was monitored for a period of 6 months. At the end of the 6-month preload period, the surcharge was removed and final roadway construction was completed. MONITORING Following completion of construction, portions of the roadway embankment were monitored by periodic elevation surveys. Elevation measurements were collected along Route 18 SW at 100-foot intervals from station 1394+00 to station 1399+00 where the underlying landfill material was compacted by the dynamic compaction process. Elevation measurements were also collected along Ramp E at 100-foot intervals from station 13+00 to station 19+00 where the underlying landfill material was treated by preloading / surcharging. Survey elevation data were collected over a period of twelve years. Comparing

the periodic survey elevation data to the as-built roadway elevations allows for the computation of settlement with time. Tables 1 and 2 present the embankment height, landfill thickness, and total settlement observed over the monitoring period at each location monitored for the roadway embankment underlain by landfill treated by dynamic compaction and preload / surcharge, respectively. EVALUATION OF LONG TERM PERFORMANCE Analysis of the data presented in Tables 1and 2 indicates that the total settlement observed over the monitoring period for the embankment underlain by landfill treated by dynamic compaction ranges from approximately 85 to 215 mm. Total settlement observed for the same period for the embankment underlain by landfill treated by preload / surcharge ranges from approximately 282 to 651 mm. Tables 3 and 4 present the ratio of total settlement in mm to landfill thickness in meters in order to compare the total settlement based on an equivalent thickness of landfill material. From Table 3, the observed settlement for the area treated by dynamic compaction ranged from 24.3 to 48.3 and averaged 36.9 mm of settlement per meter of landfill thickness over the 12-year monitoring period. In comparison, from Table 4, the observed settlement for the area treated by preload / surcharge ranged from 47.8 to 89.2 and averaged 72.4 mm of settlement per meter of landfill thickness over the 12-year monitoring period.

Paper No. 2.51 3

Table 1. Dynamic Compaction Summary

Settlement (mm)

Station

Embankment Height

(m)

Landfill Thickness

(m) Sep-91 Jul-93 Apr-95 Sep-97 Feb-00 Mar-03

1394+00 8.3 2.3 46 40 48 66 51 114 1395+00 7.7 1.8 9 24 17 36 25 87 1396+00 5.4 3.5 30 1 23 13 85 1397+00 4.5 4.6 58 79 62 85 77 149 1398+00 3.0 6.7 24 58 75 116 126 215 1399+00 3.3 6.5 33 55 62 93

Note: Construction of embankment completed in 1989. Table 2. Preload / Surcharge Summary

Settlement (mm)

Station

Embankment Height

(m)

Landfill Thickness

(m) Sep-91 Jul-93 Apr-95 Sep-97 Feb-00 Mar-03

13+00 7.5 6.2 55 43 179 228 261 375 14+00 6.7 6.3 186 213 321 378 414 536 15+00 5.2 7.1 167 183 325 397 441 564 16+00 4.0 7.4 217 241 387 464 508 636 17+00 3.2 7.3 147 180 308 426 497 651 18+00 2.7 6.6 25 34 147 214 256 389 19+00 2.3 5.9 18 100 144 168 282

Note: Construction of embankment completed in 1989. Table 3. Ratio of Total Settlement to Landfill Thickness for Dynamic Compaction Area

Station

Landfill Thickness

(m)

Total Settlement

(mm)

Ratio of Total Settlement to

Landfill Thickness (mm/m)

1394+00 2.3 114 49.6 1395+00 1.8 87 48.3 1396+00 3.5 85 24.3 1397+00 4.6 149 32.4 1398+00 6.7 215 32.1 1399+00 6.5 - -

Range = 24.3 to 49.6 mm/m Average = 37.3 mm/m

Table 4. Ratio of Total Settlement to Landfill Thickness for Preload / Surcharge Area

Station

Landfill Thickness

(m)

Total Settlement

(mm)

Ratio of Total Settlement to

Landfill Thickness (mm/m)

13+00 6.2 375 60.5 14+00 6.3 536 85.1 15+00 7.1 564 79.4 16+00 7.4 636 85.9 17+00 7.3 651 89.2 18+00 6.6 389 58.9 19+00 5.9 282 47.8

Range = 47.8 to 89.2 mm/m Average = 72.4 mm/m

Paper No. 2.51 4

Figure 2 presents a settlement profile vs. time for the embankment underlain by landfill treated by dynamic compaction while Fig. 3 presents a settlement profile vs. time for the embankment underlain by landfill and treated by preload / surcharge. Review of Figures 2 and 3 indicate that

the roadway embankment constructed over landfill material treated by dynamic compaction is performing well with respect to observed settlement over the 12-year monitoring period as compared to the roadway embankment constructed over landfill material treated by preload / surcharge.

-800

-600

-400

-200

0

200

400

600

8001393 1394 1395 1396 1397 1398 1399 1400

Station (+00)

Settl

emen

t (m

m)

-16

-12

-8

-4

0

4

8

12

16

Mat

eria

l Thi

ckne

ss (m

) 1989199119931995199720002003

LandfillThickness

EmbankmentHeight

1989

2003

Fig. 2. Settlement profile along portion of mainline embankment subjected to dynamic compaction.

-800

-600

-400

-200

0

200

400

600

80012 13 14 15 16 17 18 19 20

Station (+00)

Settl

emen

t (m

m)

-16

-12

-8

-4

0

4

8

12

16

Mat

eria

l Thi

ckne

ss (m

) 1989199119931995199720002003

Landfill Thickness

EmbankmentHeight

1989

2003

Fig. 3. Settlement profile along portion of Ramp E embankment subjected to preload / surcharge.

Paper No. 2.51 5

Secondary settlement in the dynamic compaction area is progressing at a much slower rate and differential settlement is not as extreme as that observed in the preload / surcharge area. Figures 4 and 5 present photographic representation of the roadway performance for each of the sections monitored.

Fig. 4. Minimal deformation of the roadway occurred due to settlement at the Dynamic Compaction location.

Fig. 5. Significant deformation of the roadway was caused by settlement at the Ramp E Preload / Surcharge location. Figure 6 presents total settlement vs. time for all monitored locations for both the dynamic compaction and preload / surcharge treatment areas. As shown in this figure, dynamic compaction was more effective in reducing the rate of secondary settlement as compared to the preload / surcharge treated area. In order to compare and quantify the reduction in the rate of secondary settlement, the coefficient of secondary compression (Cα) was computed from total settlement vs. time

data collected for each monitoring point. The following equation from Bowles [1984] was used to perform the back calculation assuming that primary compression was complete in 1991:

Cα = ∆ε / Log (t2/t1) (1) Tables 5 and 6 present the computed coefficient of secondary compression for each monitoring location. Review of Table 5 indicates that Cα ranges from 0.0153 to 0.0513 with an average value of 0.0313 for the landfill material treated by dynamic compaction. Review of Table 6 indicates that Cα ranges from 0.0529 to 0.0817 with an average value of 0.0657 for the landfill material treated by preload / surcharge. NAVFAC [1982] indicates that the coefficient of secondary compression for landfills which have experienced decomposition for 10 to 15 years prior to new loading ranges from 0.02 to 0.07. For the landfill materials subjected to dynamic compaction, the Cα values are generally in the lower portion of this range. The Cα values for the landfill materials that underwent the preload / surcharge soil improvement are in the upper portion of the range. CONCLUSION Review of settlement data collected over a period of 12 years after construction of a highway embankment built over landfill material treated using two different ground modification techniques indicates that dynamic compaction is more effective in reducing the rate of secondary compression than preload / surcharging. The settlement observed over the 12-year period per meter of landfill thickness is approximately double in the preload / surcharge area as compared to the area treated by dynamic compaction. Furthermore, back calculation of the coefficient of secondary compression indicates that this parameter was effectively reduced by up to 50 percent for landfill material treated by dynamic compaction as compared to landfill material treated by preload / surcharging. REFERENCES Bowles, J.E. [1984]. “Physical and Geotechnical Properties of Soils”, McGraw-Hill Book Company, New York, NY. Lewis, P.J. and J.A. Langer [1994]. “Dynamic Compaction of Landfill Beneath Embankment”, ASCE Geotechnical Special Publication No. 40: Vertical and Horizontal Deformations of Foundations and Embankments, pp. 451-461. U.S. Department of the Navy [1983]. “Soil Dynamics, Deep Stabilization, and Special Geotechnical Construction”, Design Manual 7.3, NAVFAC DM7.3, Naval Facilities Engineering Command, Alexandria, VA.

Paper No. 2.51 6

0

100

200

300

400

500

600

700

8001988 1990 1992 1994 1996 1998 2000 2002 2004

Year

Settl

emen

t (m

m)

13+0014+0015+0016+0017+0018+0019+001394+001395+001396+001397+001398+001399+00

Solid Lines - Preload / SurchargeDashed Lines - Dynamic Compaction

Fig. 6. Comparison of the amount settlement of embankments at the Dynamic Compaction and Preload / Surcharge locations.

Table 5. Coefficient of Secondary Compression (Cα) of Landfill Material at the Dynamic Compaction Area

Settlement (mm) Station

Landfill Thickness (m) Sep-91 Mar-03 Cα

1394+00 2.3 46 114 0.0350 1395+00 1.8 9 87 0.0513 1396+00 3.5 30(a) 85 0.0289 1397+00 4.6 58 149 0.0234 1398+00 6.7 24 215 0.0337 1399+00 6.5 33 93(b) 0.0153

(a) Jul-93 data point Range = 0.0153 to 0.0513 (b) Sep-97 data point Average = 0.0313

Table 6. Coefficient of Secondary Compression (Cα) of Landfill Material at the Preload / Surcharge Area

Settlement (mm) Station

Landfill Thickness (m) Sep-91 Mar-03 Cα

13+00 6.2 55 375 0.0611 14+00 6.3 186 536 0.0657 15+00 7.1 167 564 0.0662 16+00 7.4 217 636 0.0670 17+00 7.3 147 651 0.0817 18+00 6.6 25 389 0.0653 19+00 5.9 18 282 0.0529

Range = 0.0529 to 0.0817 Average = 0.0657