Transportation Research Record 1008 89

REFERENCES partment of Civil Engineering, Northwestern Uni­versity, Evanston, Ill., 1979.

1. B. Skipp and L. Renner. The Improvement of the Mechanical Properties of Sand. Proc., Symposium on Grouts and Drilling Muds in Engineering Prac­tice, British National Society, International So­ciety of Soil Mechanics and Foundation Engineer­ing, Institute of Civil Engineers, London, 1963.

2. M.M. Al-Hussaini and F.C. Townsend. Tensile Test­ing of Soils: A Literature Review. Miscellaneous Paper S-73-24. U.S. Army Corps of Engineers Waterways Experiment Station, Vicksburg, Miss., 1963.

3. G.P. Anderson, S.J. Bennett, and K.L. DeVries. Analysis and Testing of Adhesive Bonds. Academic Press, New York, 1977.

4. R. Christopher. Evaluation of Specimen Prepara­tion and Testing Procedures for Chemically Stabilized Granular Materials. M.S. thesis. De-

5. C. Vipulanandan. Interactive Roles of Constitu­ents on the Mechan ical Behavior of Chemically Grouted Sand . Ph.D . dissertation . Depar tment of Civil Engineering , Northwester n Un i versity, Evanston, Ill ., 1984 .

6. R.P. Khera and R.J. Krizek. Measurement and Con­trol of Radial Deformation in the Tr iaxial Test of Soils. Materials Research and Standards, Vol. 7, No. 9, 1967, pp. 392-396.

7. W.D. Smith, P.O. Foote, and P.F. Busang. Packing of Homogeneous Spheres. Physical Review, Vol. 24, 1929, pp. 1271-1274.

Publication of this paper sponsored by Committee on Subsurface Soil-Structure Interaction.

California Department of Transportation Structural Steel Plate Pipe Culvert Research: Design Summary and Implementation

A. E. BACHER and D. E. KIRKLAND

ABSTRACT

Three structural steel plate pipes (SSPP) have been instrumented and tested as part of an extensive culvert research program by the California Department of Transportation. Two were functional roadway cross drains, at Chadd Creek and Apple Canyon, and one was a grossly underdesigned culvert, the DB culvert. The Chadd Creek culvert was a 114-in. SSPP 0.280 in. thick with 89 ft of overfill and Method B backfill (baled straw surmounting the pipe). The diagram of Method B fill height versus soil stress was nonlinear; strains and strain gradients were large; deflection was l percent. The Apple Canyon culvert was a twin 108-in. SSPP 0.375 in. thick with 160 ft of overfill and Method A backfill (struc­ture backfill surrounding the culvert periphery). The diagram of Method A fill height versus soil stress was linear; relatively uniform peripheral pressures were observed; there was an effective density increase of 50 percent subsequent to fill completion and 2 percent deflection. The DB culvert was a 120-in. SSPP 0.109 in. thick with a maximum of 190 ft of overfill and six zones of Method A backfill and two zones of Method B backfill. The six Method A zones suffered excessive deflections or seam failure before fill completion. The two Method B zones (with slotted bolt holes or sprayed polystyrene backpacking) reduced ef­fective densities significantly. Conclusions for Method A are that the design loading should be 140V:l40H and that the effective density increase should be 1.5. The Marston and Spangler design methods are not recommended; ring-compres­sion and neutral-point analysis are acceptable designs. The Method B conclu­sions are that baled straw is not recommended and that slotted bolt holes and sprayed polystyrene show promise.

90

In 1963 the California Department of Transportation (Caltrans) in cooperation with the FHWA, initiated a $3.5 million culvert research program to assess structural behavior of culverts embedded in deep em­bankments. Included in this extensive culvert re­search program were three structural steel plate pipe (SSPP) projects.

The SSPP culvert research program was mandated by

1. Distress observed in flexible culverts under earth embankments ranging up to 150 ft in depth,

2. A proposal by District 1 to use Method B (baled straw) backfill surmounting an SSPP, and

3. Collapse of a contractor's 27-ft-diameter SSPP truck loading chute at Los Banos Reservoir in 1963.

The three SSPP culvert research projects are de­scribed as follows:

Plate Culvert Thickness Size Overfill

Location (in.) (in.) (ft) Chadd Creek 0.280 114 89 Apple Canyon 0.280, 108 160

0.375 DB Culvert 0.109 120 190

CHADD CREEK

The initial one of the three Caltrans flexible pipe culvert research projects was a 114-in. functional SSPP surmounted by layers of baled straw (Method Bl at Chadd Creek. Instrumentation consisted of Carlson soil stress meters and SR-4 strain gauges.

'l'he ef fective density profiles based on unad­justed soil pressure i::eadings for the Chadd Creek culvert are shown in Figures l and 2. Effective den­sity is defined as the equivalent density of soil that results in the recorded pressure at each meter. It is calculated by multiplying the recorded meter pressure in pounds per square inch by 144 and divid­ing that value by the fill height in feet. Each point on the plot periphery where an effective dens­ity value is shown represents a meter location. The scale of the culvert she and magnitude of the ef­fective densities is common to all effe~tive dangity plots. 'l'he design parameters for each zone (size of culve.rt, thickness of culvert material, and bedding and backf ill parameters) are shown on the left of each figure . The effective densities at the time of

Baekllll · At Fiii Completion Et! 5' 11©63 cl 08

'-6' I' 63 57

Sit of Struolurol 140 I 80 Plott Pipe I0.280inJ

173

Stg!lgn 0-96 - 81' Om!!!! 318

165~100 65 92 86

Sh oped Bedding 49 41 81

63 83

Stmlutt 9aeUll/ S allon 0•11-89' Omflll

FIGURE 1 Chadd Creek: effective densities, Stations 0-96 and 0+44.

Transportation Research Record 1008

28 Monlhl Al Fiii Completion After Fiii Completion

9'-6' -2' 62 128 I

5' 11¥-65pof 92 144~

88

136

Slut St1uc/vral 72 63 ~08 86

155

Pia 11 Pipe 0.280in,) Shopod B1dd1n9 I 6

Struclvro Backl1ll Station I •00-75' Ortr fill 254

FIGURE 2 Chadd Creek: effective densities, Station 1 +-00.

fill completion are shown in the center plots, and those recorded 28 months subsequent to fill comple­tion are on the right.

The method B type installations of SSPP at Chadd Creek had baled straw as the soft inclusion in the backfill (Stations 0-96, 0+44, and 1+100).

Although the Chadd Creek pipe did not exhibit any noticeable distress and pipe displacements remained relatively small (e.g., 1 percent), it is apparent from viewing the effective density profiles that there is an adverse effect on the pipe from the straw backfill. As one can see from Figures 1 and 2, the peripheral effective densities are not uniform, and a relatively uniform loading condition about the periphery is considered essential to the performance of a flexible culvert. Care also has to be taken to control deflections for a flexible culvert.

The plot of soil pressure versus fill height for the Chadd Creek culvert indicates a distinct nonlin­earity in loading (Figure 3). There was also an in­crease in effective densities subsequent to fill completion.

180 Stotion 0-96

0 ./ !:

150

-: 120 ·~ ... - 90

~ t;; 60

J ·;;

"' 30

15 30 45 60

Fiii Height (Fl.)

l/ ,,.... .

-' :

' ~ · e: ...,, :cl o ;

~:

:i: _ ,

"" 75 6 12 18 24 30 Time ofter 1111 comploted (Month•)

FIGURE 3 Chadd Creek: soil pressures.

Marston's theory predicted higher crown pressures than observed and failed to predict the pressure in­creases after fill completion. Spangler' s Iowa de­flection formula <1• £) resulted in calculated de­flections that ranged from 10 to 16 times larger than the measured vertical displacements. Ring-com­pression theory predicted thrusts that correlated well with observed thrusts. Neutral-point analysi s (Figure 4) al.so resulted in excellent correlation between the theoretical and experimental bending moments. The moment gradient, however, w-as too large.

Method B baled straw backfill surmounting SSPP is not recommended <1-2>·

Bacher and Kirkland

- E1perimentol Moment

-Th1ortlicol moment based on &EJ1P1rimenlol mom1nl based obHrnd soil prui ores. on SR-4 strain oauo1.

Station 0-96-81' Overf ill

FIGURE 4 Chadd Creek: theoretical and experimental moments.

APPLE CANYON

The second research project on flexible pipe cul­verts was at Apple Canyon. It was a twin 108-in. functional SSPP under Method A backfill. Instrumen­tation consisted of Carlson soil stress meters and SR-4 strain gauges.

The effective density profiles for the Apple can­yon culvert are shown in Figure 5. These represent two Method A type installations, where structure backfill surrounds the pipe periphery (Stations 7+25 and 10+00). It is apparent from viewing the two ef­fective density profiles for this flexible pipe that a single band of loading should be applied to a flexible culvert. Because a flexible culvert can de­flect, a relatively uniform loading condition is created about the periphery. However, care has to be taken to assure controlled deflections for a flex­ible culvert.

36 Month•

fJ 9~25 (0.375in.I

ped 81ddlno 115 St1ucture Bockrill 126 245 Stotlop IOt00 -160° Omftll

FIGURE 5 Apple Canyon: effective densities, Stations 7+25 and 10+00.

The effective density increase with time was quite significant. At Apple Canyon, the increase on the average was approximately 50 percent; at station 10+00, for example, the effective density at the lowest left meter increased from 115 to 245 pcf in the 24 months subsequent to fill completion. simi­larly, Station 7+25 also exhibited the same dramatic increases in effective density. There is essential linearity in loading for Apple Canyon with Method A backfill, as shown in the diagram of fill height versus soil stress (Figure 6) • Of particular sig­nificance is the increase in soil -stress after fill

180

150

30

! Slation 10 I

0 ' / - i )~- !"-.. .

:i I v ~ ·

~. ___. Ji _.,V

,,..... s: ..., M<

/ .~ "'' ' o ,

~I

30 60 90 . 120 150 0 . 6 12 18 24 30 36 Time ofter fil l completed (Months) Fiii Helohl (Ft.I

FIGURE 6 Apple Canyon: soil pressures.

91

completion. By contrast, there was distinct nonlin­earity in the plot of fill height versus soil pres­sure for Chadd Creek with Method B backfill.

Previously specified yield strains (57,000 psi observed versus 28,000 psi specified) were common at Apple Canyon, but the pipe displacements remained relatively small with less than a 2 percent change from the initial installed peripheral shape.

Marston' s theory failed to predict the pressure increase after fill completion. Spangler's Iowa de­flection formula resulted in theoretical deforma­tions 8 to 11 times larger than those observed. Ring-compression theory had calculated thrusts that were only 50 percent of the measured thrusts. There is an effective density increase subsequent to fill completion; that is, Be = 1.50. Neutral-point analysis (Figure 7) provided fair correlation be­tween the theoretical and experimental bending mo­ments. The moment gradient was far less than that observed at Chadd Creek; in fact, the moment gradi­ent at Chadd Creek was 50 percent higher. Finite­element analysis yielded poor correlations between measured and theoretical displacements and pipe stresses (~,1.J .

-Theoretical momenl bo50d on E.perimenlol momenl baud aburved soll prusures. on SR-4 slroin oouoe.

Stat ion 10•00- 160' Overfill

FIGURE 7 Apple Canyon: theoretical and experimental moments.

DB CULVERT

The DB culvert was a 320-ft-long, grossly underde­signed dummy SSPP divided into eight zones, each having different bedding and backfill parameters. Various levels of backfill compaction, the effects of shaped versus flat bedding, and trench installa­tions were among the parameters considered. In addi­tion, two recent Method B innovations--circumferen­tially slotted bolt holes and sprayed polystyrene

92

backpacking--were incorporated into the project. Instrumentation consisted of Kyowa and Ormand soil stress meters and SR-4 strain gauges that measured the pipe wall strains.

At the DB culvert the instrumentation was sup­plemented by Cambridge meters that measured soil shear stresses at the culvert-soil interface in ad­dition to normal soil stresses. Further, there were three planes of meters spaced approximately 2 ft apart at each instrumented section, which provided added reliability for the test results.

The effective density profiles for Zones l through B (Figures 8-11) have been plotted based on the unadjusted soil-pressure readings=

Roadway E111ban\men1 7!1 'llO C111poctlon

Slul Struclllfal Plott Pipe, (t•0.1091n.)

Roadway Embankment

""~a Flot Bedding

At 40' Overfill 108pcl

At Fiii Compl11fo1

FIGURE 8 DB culvert: effective densit.ies, Zones 1 and 2.

Roodwoy Embankment 90 % Compaction At 120' Omflll At Fill Completion

100 pc! 6"'1', Deflection 98

Flol Beddin 122 3 4 O 113 9 Zone 3-164' Overfill: Average- Planes A,8,C

UAI 140

1 gvulill At Fill §•lnpilllon

Se.om 2B2 Failure 95 118 25 33

4 ~ 3 62 20 11 14 60 6 3 ~ 6 hoped Bidding , .

9!>'1• Compaction Zone 4-167 Overflfl: Average- Planes A,8,C

FIGURE 9 DB culvert: effective densities, Zones 3 and 4.

24 Month• At Fiii Completion After Fill Completion

24 25

20 23pcl la· 22 24 23 26 24

19 19 19 20 25 12 II 1 27 2113 19 6 23

Shoped Bedding Zone 6· 174 ' Onrllll • Mtrooe-Plonu A,B,C 95 % Compoctlon 84 98

Slotted Hol.. •

0.

All Seomt ~3 66

67 81 70 54 B

48 244 49 Stul Structural

83

PIQll Pl~o It •0.109inl Zone 6-180' Overfill: Average-Planes A,8,C

FIGURE 10 DB culvert: effective densities, Zones 5 and 6.

Transportation Research Record 1008

At 140' Over Ii 11 Al Fiii Completlan

5lpcl Seam e7 f2 Fo lure

96 6 18 55 45 52 /

41 20 21 9 51 3 2 4

Zone 7-190' Overfill Awtrooe-Plonu A.B.C 6 Months

Al 170' Overfill Aller Fiii Completion 53 39

Seom 24 foi luro 82 20

11--" __ ,_,

21 .

41 a2 33 66 I 5

AYlfOJt-Plonn A,8,C

FIGURE 11 DB culvert: effective densities, Zones 7 and 8.

The Method A zones (Zones 1-4, 7, and 8) all ex­hibited distress at some fill less than the maximum overfill. The effective density plots have therefore been drawn based on the overfill at the time that this distress occurred, whether the distress was manifested by excessive deformation or seam failure. Deflections were significant: 18 percent at Zone 1 with 75 percent relative compaction, 9 percent at Zone 2 with 83 percent compaction, and 8 percent at Zone 3 with 90 percent compaction. A deflection in excess of 5 percent is considered structurally un­acceptable based on Spangler' s Iowa deflection for­mula (Zones 1, 2, and 3). Deflections at 75, 83, and 90 percent relative compaction were also compared with observed deflections in Watkins test cell at Utah State University. Horizontal diameter changes in the test cell were valid for high standard densi­ties, but the limiting boundary conditions of the test cell resulted in poor correlation at lower den­sities, of 75 and 83 percent relative compaction. Zones 4, 7, and B exhibited seam failure. Where slotted holes were provided (Zone 6) and poly­styrene was sprayed on the upper 240 degrees of the culvert periphery (Zone 5), the results were promis­ing. The slotted holes closed prematurely when less than 20 ft of overfill had been placed. The rela­tively uniform effective density of approximately 25 pcf at zone 5 with 6-in. polystycene backing pro­vided an excellent means of control.led reduction of peripheral pressures.

In the plot of soil pressures from the three planes of stress meters at Zone 3 (Figures 12 and 13), a wide disparity was exhibited between the Cam­bridge stress meters and the Kyowa and Ormond stress meters. The peripheral pressures at Zone 3 also were reduced because of overstress when the overfill ex­ceeded 120 ft. Cambridge meter shear readings are shown in Figure 14. Note that some tangential shears were clockwise; others were counterclockwise. The tangential shear readings did not materially alter the recommended design effective densities.

Because of the excessive deflection or seam fail­ure occurring at overfills less than the maximum overfill for Zones 1, 2, 3, 4, 7, and 8 during con­struction, no attempt was made to apply Marston's theory, Spangler's Iowa deflection formula, ring­compression theory, or neutral-point analysis. Fi­nite-element analyses were made for Zones 2, 5, and 8. The finite element was not applicable when the overfill exceeded 120 ft, that is, after there was a seam failure. Further, the reality of probable vari­able soil parameters at a given culvert site empha­sizes that finite-element applicability is contin-

Bacher and Kirkland

" ...

0 40 80

Fill Hli9hl (Fl. I

160 12 24 Time afllf lill Completed (llonlhsJ

FIGURE 12 DB culvert: soil pressures.

Plane A {°'-d 511111 Miter

,fP-0,,--- · · -::::::.~,~=--::::.,)iO .. ~ ~ t[ ( / 116p.s i

~ I

/ .......... ___ ... ___ _ ... ..... ____ _.,,,.

At 120' Overfill Al Fill Complelion Zcm l ·164' 01111111

FIGURE 13 DB culvert: soil stress meters, normal pressures.

Plane C · ·-Cambridge

/ (

,,.....----..... /

Zone l · !64' Omfill

\ 80psi

j

/

FIGURE 14 DB culvert: soil stress meters, tangential shears.

gent on the availability of adequate and complete soil data at each site.

Large deflections and buckling observed in the grossly underdesigned DB culvert indicate that cur­rent :;;afety factors are not overly conservative. On Method A sections, the observed effective densities were approximately half those observed at Apple Can­yon. Because DB is a nonfunctional culvert, there was no continuously saturated condition at the pe­r !meter of the culvert caused by stream flow, which effectively reduced the external pressures. At the

93

DB culvert distress occurred at approximately 120 ft of overfill. With an allowable design overfill of 33 ft, there was therefore a safety factor of only 2 because the observed effective densities at the DB culvert were only half those observed at Apple Can­yon (~).

IMPLEMENTATION

The following Caltrans criteria were developed from the three research projects (2_) •

Method A

A uniform effective density of 140V:l40H should be applied. An effective density increase of 1.5 (Be) should also be applied. Ring-compr ession theory is considered to be an acceptable approximate design method for SSPP. Marston's theory and Spangler's Iowa deflection formula are not recommended. Neu­tral-point analysis is an acceptable alternative design method. Application of the ring-compression method by using load factor design is shown in Fig­ure 15. AASHTO requirements are far less stringent, as shown in Figure 16. This criterion should specify a higher factor of safety.

Groop X·Colnrt•!(,800+,BEEt,Bl (L•ll)

W•trt i•l.3, .So•l.0,,BE'l.~,Jlt:!.67,Q•0.9

LOAD FACTOR DESIGN·SSPP

FIGURE 15 Caltrans criteria: unit load on culverts.

Method B

Groop X·Culmt•![,800•,BEE•,BL (L•IIJ Wh111 & • 1.3, ,s 0.1.o.,BE•l.5,,BL•l.&7,Q•0.67

LOAD FACTOR OESIGN·SSPP

FIGURE 16 AASHTO l .2.2(A): unit load on culverts.

Baled straw is not recommended for use on flexible steel pipe. Slotted bolt holes with proper keyhole designs may be used to reduce the loading. It is possible that sprayed polystyrene could be used to advantage because the DB culvert research showed that this technique resulted in an 80 percent reduc­tion in current design effective densities. An as-

94

sessment of its cost-effectiveness would have to be made.

COST SAVINGS

Based on Caltrans SSPP culvert research, the allow­able overfill for a 60-in. (0.109-in.-thick) SSPP has been increased from 42 to 57 ft; for a 240-in. (0,280-in.-thick) SSPP it has been increased from 36 to 44 ft, The estimated savings over the full range of pipe sizes used in California is $150, 000 per year.

ACKNOWLEDGMENT

Al Banke and Craig Chatelain of Caltrans also con­tributed to the development of the rational design method for SSPP now used in California.

REFERENCES

1. M.G, Spangler. Field Measurements of the Settle­ment Ratios of Various Highway Culverts. Bull. 170. Engineering Experiment Station, Iowa State University, Ames, 1950.

2. M.G, Spangler. The Structural Design of Flexible Pipe Culverts. Bull. 153. Engineering Experiment Station, Iowa State University, Ames, 1941.

3. R.E. Davis and A,E. Bacher. California's Culvert Research Program--Description, Current Status, and Observed Peripheral Pressures. In Highway Re-

Transportation Research Record 1008

search Record 249, HRB, National Research Coun­cil, Washington, D.C., 1968, pp. 14-23.

4. K.M. Fenwick. Allowable Cover on Corrugated Steel Pipe. Highway Research Report, California Division of Highways, Sacramento, Feb. 1969.

5. R.E. Davis. Structural Behavior of a Flexible Metal Culvert Under a Deep Earth Embankment Using Method B (Baled Straw) Backfill. Report R&D 4-69. Bridge Department, California Division of High­ways, Sacramento, 1969.

6. D.W. Spannagel, R.E. Davis, and A.E. Bacher. Structural Behavior o~ a Flexible Metal Culvert Under a Deep Earth Embankment Using Method A Backfill. Report CA-HY-BD-624111-73-6. Bridge Department, California Division of Highways, Sac­ramento, June 1973.

i. D.W. Spannagel, R.E. Davis, and A.E. Bacher. Ef­fects of Method A and B Backfill on Flexible Cul­verts Under High Fills. In Transportation Re­search Record 510, TRB, National Research Council, Washington, D.C., 1974, pp. 41-55.

8. R.E. Davis and A.E. Bacher. Prooftesting of a Structural Plate Pipe with Varying Bedding and Backfill Parameters. Reports FHWA/CA/SD-79/20-SD-82/10 (Vols. 1-8) • Office of Structures Design, California Department of Transportation, Sacra­mento, 1979-1983.

9. Interim Specifications for Highway Bridges, Sec­tion l. 9: Soil-Corrugated Metal Structure Inter­action Systems. AASHTO, Washington, D,C,, 1981,

Publication of this paper sponsored by Conunittee on Culverts and Hydraulic Structures.

Construction and Field Evaluation of Precast Concrete Arch Structures

JAMES J. HILL

ABSTRACT

A construction and field evaluation is presented of the precast concrete arch structures (BEBO of America) that have been constructed in Minnesota since 1980. Fabrication, construction, and follow-up inspections of the arch struc­tures have revealed certain construction techniques and structural deficiencies that require correction. Settlement and movement of selected arch structures have been monitored to determine deformation and related results. A construc­tion time frame and an estimated cost comparison of alternative structures are also included.

The details and design of the precast concrete arch structures built in Minnesota are pr~sented, The lo­cations of these structures and their individual data are given in Figure 1 and Table l. The plant

fabrication and material specifications are related in general terms.

Field installation and follow-up inspections are presented that disclose structural inadequacies