_r

a

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CHAPTER 2 SUMMARY OF CURRENT EXPERIENCE: FABRICATION TO FIELD PERFORMANCE

To date, truck-tire pipes have been used at about 30 locations in Oklahoma, Texas, and Arkansas. One of the project objectives was to determine how the truck-tire pipe has performed in the field. To determine what problems and benefits have been encountered during installation and use, the project team made field inspections of existing installations, and queried the personnel who had installed and used the pipe. In most cases installations were made by county road departments, though individual landowners have installed pipes and extensive applications have occurred at three tire shredding facilities. Each site inspection is reported in detail in Appendix A. Of the 26 pipe installations inspected, one was observed to be in fair condition while all others were evaluateddas good. Most installations inspected consist of one or two pipe runs of 3 or 4 pipes each. In a few cases much longer runs have been installed . During the process of inquiring about performance, field personnel made remarks about aspects other than performance, and these remarks are reported in this section, where appropriate . OTHER PIPE ALTERNATIVES

Inherent in the evaluation of a product is a comparison with alternatives to the product. Discussions with county commissioners and with natural resource companies in Oklahoma and Arkansas indicated that the two predominate types of drainage pipe currently being installed are

galvanized corrugated steel and fiberglass. When bought in large quantities, some agencies obtain either type for between $5.25 and $6.00 per linear foot; the cost may double when bought in small quantities. Other county road districts reported higherunit prices for these pipes. One natural resource company representative stated that a galvanized corrugated pipe may last 20 years, but they expect the newer fiberglass pipes to last 50 years . One county employee said galvanized pipe lasts about 25 years . In some areas, used oil well pipe suitable for culverts is available for about $7.00 per linear foot. Polyethylene piping can be used, but is more expensive and was not mentioned a being used by any of the road crews. TIRE PIPE MANUFACTURING

Decisions made concerning the truck tire pipe manufacturing process affect the product's performance in thefield. The current process produces a product with anundulating or uneven end (when viewed perpendicular to the length or "long" dimension of the pipe), because the rebars "pinch" the bead-sidewallsasshown in Figure 7(a) and8(a). A method that would produce a flat end would be preferable . A future modification that would produce an improved product involves

punching four holes through each bead-sidewalls, "threading" rebars through these holes, and fixing them to metal, rubber, or fiberglass ends of similar shape and size to the bead-sidewall .

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This would result in flat uniform ends, and thus would allow for better joint connections, but at increased cost.

One issue raised by users was whether there would be any benefits from using a thicker reinforcing bar (rebar) to bind the separate sidewalls into a pipe unit. The manufacturer has stated that the 3/8 inch (0.95 cm) size is preferred, because it is easier to bend than the larger sizes . The only benefit that might be incurred by increasing the rebarsize would be anincrease in the time required to rust through the rebars. Rusting through one or two rebars is the most likely failure mode for the tire-pipes. Currently, the rebars are coated with a rust inhibiting paint. An alternative would be to use fiberglass rebars, which are more expensive. Rebar corrosion is discussed in greater detail in Chapter 3. SHIPPING AND HANDLING

Before the pipe is installed in the ground, it must be transported to and unloaded at the site. Product durability and ease of handling during transport are concerns. The pipe is rather heavy ; the manufacturer reports that a section weighs about 150 pounds per linear foot, with the standard 8 foot section weighing 1200 pounds. This makes shipping and handling more difficult for the tire pipe than for a comparably-sized galvanized or fiberglass pipe.

There were reported experiences with difficulty and damage during transport and delivery . Some of the problems may have occurred when the manufacturer made 10 foot sections, before going exclusively to the 8 foot section. A picture of a 10 ft section which failed during installation is shown in Figure 9. The manufacturer states that the tire-pipe can be damaged by dragging one section across another, or by dropping the tire pipe on its end --it may buckle.

Because the pipe may be damaged if it is flexed laterally, care must be exercised when taking the pipe from a truck and placing it in a ditch. Some use a back hoe to hoist a chain slipped through the inside of the pipe. Even with care, a few rebarwelds have been broken during installation. Sometimes the bar was rewelded and the pipe used, a couple of discarded tire-pipes with broken bars were seen in county road yards . One county slipped a stout rigid bar through the entire length of the pipe, and attached a chain to each end of the bar, this seems to be the better method.

One county commissioner's office reported that "the pipe is too heavy, awkward to handle . While unloading pipe during delivery, one rebar on one pipe broke, the pipe came apart slowly, with no danger of hurting anyone." Despite some problems, most pipes remained in good shape when care was used while handling the pipe before installation.

Figure 9: Ten Foot Truck-Tire Which Failed During Installation

INSTALLATION

Because the tire-pipe is a relatively new product, installation procedures are still evolving

and are not standardized. The major issues related to installation were

¹ 1 . what special site preparation procedures are needed;

1. what type of bedding, if any, is desirable ;

2. what type of jointing procedures should be followed ;

3. how much cover is needed over the top of the pipe; and

5. what are the installation cost and time requirements .
Site Preparation Procedures

As to special site preparation, one county field supervisor commented "to install [the] tire-

pipe, the pipe bed needs to dug with the proper slope, because irregularities in pipe surface make it

more difficult to tell what the pipe slope is . You need a little smoother ditch to install tire pipe than

you do for a galvanized pipe; [the] tire-pipe is more difficult to install if the ditch bottom is

muddy."

Due to the thicker walls, tire-pipes require a slightlydeeper trench than thin-walled culvert

pipe of similar inside diameter. Therefore, an equivalent inside diameter tire-pipe requires a greater

dimension from ditch bottom to top-of-pipe. Where ditches must be shallow, a tire pipe may not

work well. In a few cases, road personnel reported that they had to "build the road surface up" to

clear the top of the pipe. As an alternative to building up the road surface, the inverts of some

truck-tire pipes were installed below the stream flow line and there was subsequent siltation in the

pipe bottom.

Bedding Procedures

The bedding procedures used on the pipes observed ranged from none to elaborate. Some

installed the pipe directly on the dirt surface of a dug trench, others used crushed stone bedding.

One county encased the pipe in concrete at a low water crossing where galvanized pipe had washed

out. None of the bedding methods used resulted in any problems that the project personnel

observed. It appears that truck-tire pipes can be bedded similarly to other types of culvert.

Joining Procedures,

Because the truck-tire pipes are only 8 feet (2.4 m) in length, at least 3 or 4 sections are

used to span the typical driveway or roadway. This results in two or three joints, i.e.,places where two sections ends meet. These joints need to be tight enough to prevent water and/or surrounding soil from flowing into the pipe or to prevent outflowing water from eroding soil surrounding the pipe . A variety of jointing procedures have been used. Some of the pipe end connections had been wrapped with strips of conveyor belt or geotextile cloth. In some cases the wrap was held in place with plastic ties. At one location, the crew spot-welded rebar across the joint end. At other sites, pipe were simply butted together,with no wrap or physical connection^.

Due to the irregular shape of the pipe ends, and to pipe weight, getting a close joint is ₁difficult. Also, installers have difficulty getting joints to butt together, because to lift the pipe they install a chain through the overt (the inside, under to top) and must leave room to pull the chain out after the pipe has been lowered into the trench . After observing installation in progress, a project team member recommended that the installer rotate each section 1/8 turn from the previous section, to get a better end-to-end fit. This is because with eachpipe bound by four rebars, the "rise and fall" of each end-undulation is on a 1/4 circumference cycle ; the "out" undulations mesh with the "in" undulations by rotating a subsequent section by 1/8 the circumference. Joints will be discussed in more detail in the next chapter. Pipe Cover

The tire pipes appear to perform well with very little cover . Many of the pipes had cover ranging from 1 to 4 inches deep . Because one pipe section end under a road was protruding up into the road, and appeared to have perhaps been "hung up" by the blade of a road grader, it is suggested that all installations have sufficient cover to allow roads to be graded on a regular basis. Cost and Time,

Installers agreed that installation costs are higher for the tire-pipe than for galvanized steel or fiberglass pipe, because of the extra time required . Total installation time for a galvanized steel pipe was said to be roughly 12 day; users at different counties said installation time was greater for the tire-pipe by anywhere from about 30 minutes to 3 hours. One road maintenance supervisor, who was unimpressed by the tire-pipe, claimed that it took about 2-3 times as long to install the tire-pipe culvert compared to other types of culverts.

The major component by mass of truck-tire pipes is waste truck tires. This material can generally be obtained at zero or negative cost to the truck-tire manufacturer. For this reason, the purchase price of truck-tires pipes should be about $3 to $5 per linear foot, less than other types of pipes. FIELD PERFORMANCE

Pipe users may have a number of questions about the performance of the truck-tire pipe, regarding:

1 . water carrying capacity, and debris accumulation potential inside the pipe due to the
rough surface;

1. erosion, especially at joints, and ability to withstand flooding;

2. ability to carry the weight of vehicles passing over the pipe;

3. potential for continuous and excessive flexure, causing deterioration of the road above
   the pipe;
   

5 . failure of rebars from corrosion, resulting in pipe failure; and

6. susceptibility to fire damage.

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The field inspections gave insight into some of these and other issues .

The tire-pipes observed had all been installed in rural or small-town environments, ranging from a drive giving access to a field to a rural subdivision road ; most were on county roads. Traffic volumes at most sites were relatively light. A few of the pipe installation sites had endured some heavy-weight vehicle traffic, associated with nearby construction projects . Most of the pipes were place under dirt or gravel roads; one was under a low-typeasphalt pavement. Water Flow

Even though the surface inside the pipe is irregular, deposits observed inside the pipe were few and generally small. Many of the pipes had rather "clean" insides after a few months to more than 2 years of service. The bottom of some culverts had accumulated sedimentation material, but no more than would be expected with any type of culvert . At the few sites where extensive siltation had occurred, it appeared to be due to the pipe flow-line being too low or to upstream erosion, not due to erosion at the joints . It is important to note that the truck-tire pipe is not corrugated, as are steel and plastic drainage pipe. The truck-tire pipe's 4 inch (10 cm) thick walls make corrugation unnecessary . Thus, the truck-tire pipe inner surface, though rough, provides fewer opportunities for the collection of soil and detritus than typical corrugated culverts. Erosion

In some cases erosion of the road embankment near a pipe-end was observed. This may have been caused by insufficient compaction of the backfill on the embankment slope, and subsequent surface erosion on the side of the embankment. This type of erosion could happen with any type of drainage pipe .

Out of 90 joints observed during site inspections, three cases of erosion were observed in the road surface near a pipe joint. Two examples areshown in Figure 10. This suggests erosion into or out of the pipe, caused by gaps at a joint . Perhaps this problem can be eliminated by better installation of the joint wrap and/or using a wider wrap. Truck-tire pipe connections are discussed in greater detail in the next chapter.

At one county, users indicated that the tire pipe has been more resistant to flood damage. One run of truck-tire pipes stayed in place when comparable metal pipes washed out. One possible explanation is that the truck-tire pipe's extra weight keeps it anchored in place under situations that

can wash-out light culverts. However, Comanche County personnel stated that one tire-pipe culvert washed out the night after installation due to a heavy rain that same night ; it was re-installed and they have not experienced a problem with it since.

= = = - - - = - = = - w - =

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Loads and Deflection

The truck-tire pipes appear to be strong enough for typical culvert duty. Several pipes served roads which had carried earth moving trucks during near-by construction projects. However, the project team observed two instances of pipe deflection, i.e., pipes which noticeably deviated from a round cross-section. Though deflection was noticeable, it was not excessive . In one case the cause was not known. In the other case a county commissioner suspected than an overweight (120,000 lb.) off-road vehicle operating nearby had driven on the county road. Another explanation for truck-tire pipe deformation could be improper back filling procedures, which can lead to deflection in any drainage culvert . One of the dirt roads was observed to have a slight dip in it directly above a truck-tire culvert. This also could be due to insufficient compaction of the soil during installation. Load versus deflectiontests, presented in the next chapter, indicate that the truck-tire pipe is stiff enough for culvert duty . Cover and Flexure,

Rather small "hairline" cracks in the surface over the pipe were noted at a number of sites. It is hypothesized that this might be caused by vibration of the truck-tire pipe whenever traffic crosses it. There were no observable problems resulting from the limited cracking observed, even at sites where pipes had been in place for approximately 2.5 years. There were no cracks observed in the surface of the single low-type asphalt road (which appeared tobe crushed stone covered with chip seal) installation, although a small hairline crack was noted in the dirt cover past the edge of the asphalt. However, the asphalt had been in place less than 9 months. Rebar Durability

At one county, the long-term performance of the tire-pipe in its current form was raised concerning the potential for rebars to give and cause entire pipes to split apart. At one 10 ft.-long section installation, several of the sidewalls near the one end have been displaced out of shape (pushed inward and outward). This happened during installation of the culvert. At one end a rebar had snapped, apparently some time after installation. It may be that the rebar weld was inadequate .

₁ However, the manufacturer of the tire-pipe no longer makes the 10 foot sections, because some sections experienced excessive flexure and deformed when lifted. It appears that the most likely cause of pipe failure will be rebar yield, brought on by rebar corrosion, especially in corrosive soils. One county commissioner stated that overall, he preferred galvanized steel pipe because it is quicker and easiertoinstall, but would use the tire pipe in ^alkali

spots, due to better corrosion resistance . It is certainly true that the four inch thick rubber walls of the truck-tire culvert afford greater protection fromcorrosion. However, the end section, i.e.,the 1 sections that protrude out of the roadway, may fail when one or two rebars fail. Failure of truck-tire pipes by rebar failure is discussed in greater detailin the next chapter.

No instances of damage to the rubber truck-tire culverts caused by fire damage were noted . However, the potential for damage due to fires caused by vandalism or accidents cannot be ignored. It is not known at this time how much effort would be required on the part of vandal to cause a damaging fire. COMMENTS

In the majority of the cases, the installer/owner appeared to be pleased with the truck-tire pipe. The field investigations indicated that the tire-pipe works well in many rural road situations, but does have some limitations . The greater difficulty of installation would hopefully be outweighed by long-term performance and durability, but long term tire-pipe behavior will not be known for many years. Of course, the lack of different sizes available is a limitation, however, multiple parallel runs of the truck-tire pipe can be, and indeed are, used when greater capacity is required. The joining method is very important. If the observed holes in roadways were in fact due to erosion through a joint opening, then the jointing problem will have to be addressed . One simple solution is to use a wider wrap. To data, onlysixinch (15.3 cm) wide wrap has been used. The use of 10 or 12 inch (25.4 or 30.5) wraps would be expected to solve this problem.

CHAPTER 3 TRUCK-TIRE PIPE EVALUATION RELATIVE TO APPROPRIATE PIPE

Some standard specifications and test methods for pipes are listed in Table 1. The most appropriate specification for application to the truck-tire pipe culvert is AASHTO M 294-90, "Standard Specification for Corrugated Polyethylene Pipe, 12-36in. Diameter." ThisASSHTO specification is for pipes from 12 to36inches in diameter, used for " ...surface and subsurface drainage applications where soil provides support to its flexible walls" (AASHTO M 294-90, section 1 .1). The major use of corrugated polyethylene pipe is to ". . .collect or convey drainage water by open gravity flow, as culverts, storm drains, etc." (AASHTO M 294-90, section 1 .1). The size range and use are applicable to the truck-tire pipe. Section 7 of AASHTO M 294-90 states the requirements that corrugated polyethylene pipe must meet concerning workmanship, pipe dimensions, perforations, pipe stiffness, pipe flattening, environmental stress cracking, brittleness, and fitting requirements. Most are important to truck tire drainage pipe quality, and is considered in this Chapter. In addition, rebar corrosion will be discussed at the end of this chapter. WORKMANSHIP

Because the truck-tire pipe is made from a waste material with little pre-processing, it does not present the uniform appearanceofpipesmanufacturedusing virgin materials. However, acceptable workmanship can be delineated . The pipe should not have visible gaps between tire bead-sidewalls, nor should bead-sidewalls be split. Four rebars should be used to hold the bead-sidewall together, each should have an intact weld, and weld lengths should be sufficient to hold 6,000pounds(22,300Newtons)oftensile force. This amount is based on strain analyses performed on truck-tire pipe rebars, discussed later in this chapter. This will provide a factor of safetyofapproximately2,but is based on a limited number of tests .Rebarsshould be positioned at approximately90°intervals about the pipe circumference . PIPE DIMENSIONS

Truck-tire pipe sizes are limited to truck tire sizes, and currently are made using 20 and

22.5inch(50.8 or 55.9cm) inner diameter tires. Because truck tires are made to very strict

requirements, the inner circumference of each bead-sidewall in a given truck-tire pipe is uniform. However, due to the truck-tire pipe structure, i .e., separate discs held together by rebars, truck-tire pipe inner diameters vary for a given pipe, bead-sidewall, or orientation, i.e., the pipe bead-sidewalls are not perfect circles . In Tables 2 and 3 multiple measurements of truck-tire inner diameters and lengths are presented . The average inner diameters for the 20 and 22.5" truck-tire pipes are19.5and22.6inches, respectively(49.5 cmand57.4 cm). The variability shown in Table 2 regarding inner diameter does not present a problem for pipe connections, as it is accommodatedby the flexible joint connection

Table 1: Standard Specifications and Test Methods For Pipes

Test DescriptionIdentification

(1) (2)

AASHTO M 36 Standard Specification for Corrugated Steel Pipe, Metallic-Coated,AASHTO M 36M-90 for Sewers and Drains ASTM A 760 ASTM A 760M-86

AASHTO M 196M Standard Specification for Corrugated Aluminum Pipe for Sewers

AASHTO M 196M-90 and Drains

AASHTO M 294-90 Standard Specification for Corrugated Polyethylene Pipe, 12-36 in. Diameter AASHTO M 304M-89 Standard Specification for Poly (Vinyl Chloride) (PVC) Ribbed Drain Pipe & Fittings Based on Controlled Inside DiameterASTM F 405 Specification for Corrugated Polyethylene (PE) Tubing andFittings

ASTM D 2412 Determination of External Loading Characteristics of Plastic Pipeby Parallel-Plate LoadingASTM D 2444 Test for Impact Resistance of Thermoplastic Pipe and Fittings byMeans of a Tup (Falling Weight)ASTM D 695 Test Methodfor Compressive Strength of Ri ' Plastics ASTM D 2122 Test Method for Determining Dimensions o Thermoplastic Pipeand Fittin s ASTM F 725 Practice or Drafting Impact Test Requirements inThermoplasticpipe and Fitting Standards

ASTM -American Society for Testing and MaterialsAASHTO -American Association of State Highway and Transportation Officials

Table 2: Variation in 20 inch Diameter Truck-Tire Pipe Dimensions

Pipe Sample Number Average of FourMeasurements

Table 3: Variation in 22.5 inch Diameter Truck-Tire Pipe Dimensions

currently in use. It does indicate that 20 and 22.5 inches should be considered nominal dimensions, thus the truck-tires will be referred to as 20 and 22 .5 inch nominal truck-tire pipes.

Pipes used as culverts are typically sold in any length, up to a maximum, dependent on material. The truck-tire pipe only comes in nominal eight foot lengths . Ten foot lengths have been constructed and used, but present handling problems due to lateral instability during installation (i.e.,when not supported by soil). Shorter lengths can be made, however, if desired. The 20" nominal truck tire pipes measured had an average length of 97 .6 inches (247.9 cm), while the 22.5" nominal truck-tire pipes measured had an average length of 98 .5 inches(250.2cm). Thus, truck-tire pipe sections, as currently manufactured, tend to be slightly longer than 8 feet . PERFORATIONS

Truck-tire pipe will not be perforated, and thus cannot be used in situations where perforated pipe is required. PIPE STIFFNESS

AASHTO M 294-90 (section 7.4) specifies that corrugated polyethylene pipe shall have at least the minimum pipe stiffness at five percent deflection listed in Table 4 when tested in accordance with ASTM D 2412. Because the truck-tire pipes are not of standard size, it is necessary to interpolate the required stiffness . The information in Table 4 is plotted in Figure 11, and a straight line fit to the data results in the equation

RPS = 57.0 -0.96 ID (1) where: RPS = required pipe stiffness at 5 % deflection, psi; and ID = inner diameter, in . The line fits the data well, with an R2of 0.99. Using equation (1) the required pipe stiffness at 5 % deflection for 19.5 and 22.6 inches (49.5 and 57.4 cm) inner diameter pipes is 38 and 35 psi,

respectively. Testing conducted at Fears Structural Laboratory on the campus of the University of Oklahoma demonstrated that the truck-tire pipe stiffness exceeds the requirements shown in Table

4. A schematic of the testing apparatus is shown in Figure 12 . A picture of a pipe at near maximum deflection is shown in Figure 13 . During the tests, eight foot truck-tire pipe sections were subjected to uniformly applied lateral forces up to and in some cases exceeding 60,000

pounds. Results for all 12 culverts tested are presented in Appendix B . Figure 14 is a plot of pipe stiffness versus deflection for a 20 inch (50 .8 cm) truck-tire pipe. At 5 % deflection the pipe stiffness is 97 psi, 2.6 times greater than the required amount . During the particular test shown in

Figure 13, the culvert was deflected well past 5 % . At 65 % deflection the culvert's stiffness was over 90 psi.

Figure 11: Required Pipe Stiffness Versus Inner Diameter .

m _ - = _ mm-m__

1 2 3 4 5 6 7 8 9 10 11 12 13 14 Deflection (Inches)

Figure 14: Load Deflection Diagram for 20 inch Inner Diameter Truck-Tire Pipe (Culvert #8)

Pipe stiffnesses at 5 percent deflection for the 20 inch and 22.5 inch nominal truck-tire

pipes tested are shown in Table 5. The average values are 86 psi and 47 psi respectively, which

exceed the AASHTO requirements. The 22.5 inch nominal culvert, as expected, exhibited lower

stiffness at 5 % deflection than the 20 inch nominal culvert. However, culvert 10 had a stiffness at

5 % deflection of only 36 psi, just 1 psi greater than the required value. Inspection of the stiffness

versus deflection relationship recorded for culvert 10 (see Appendix B) shows that the culvert

maintained stiffness at 36 psi or greater at all deflectionsunder 45 %. The low stiffness value for

culvert 10 indicates a need for further tests with the 22.5 inch inner diameter pipes to ensure that

(1) the required stiffness is always met, (2) to determine if manufacturing variability or testing error caused the low value, and (3) to suggest means to improve the 22.5 inch pipes if necessary.

Two conventional eight foot culvert sections were also tested, made of corrugated

galvanized steel and corrugated polyethylene, and theresults presented in Table 5. In Figure 15

pipe stiffness versus deflection curves for typical 20 and 22.5 inch nominal truck-tire, 21 inch

steel, and 18 inch plastic pipe are shown . It is clear from the Figure that the Truck-Tire Pipes

behave differently from the other pipes. The truck-tire pipes tend to reach maximum stiffness later,

generally after 10 to 15 % deflection, while the steel and plastic pipes reached maximum stiffness

at about 5 % deflection . Furthermore, the truck-tire pipes remain stiffer for much higher

deflections, general to deflections of 40 % or higher, while the steel and plastic culverts lose

stiffness rapidly after 5 % deflection. The steel pipe did not retain its original shape after the load

in test, as shown in Figure 16. All of the truck-tire pipes tested regained their original shape after

testing, as did the polyethylene pipe. The ability to rebound indicates that truck-tire and

polyethylene pipe-ends, i.e.,the portion protruding from either side of the road, will be able to

regain their original shape if run over by errant vehicles.

AASHTO M294-90 (section 7.5) specifies that it shall be possibleto flatten corrugated

polyethylene pipe until the vertical inner diameter is reduced by 20 percent without the occurrence

of cracking, splitting, delamination, or wall buckling . Delamination refers to the separation into

constituent layers, for example, a piece of plywood separating into each wood layer. Testing

conducted at Fears Structural Laboratory on the campus of the University of Oklahoma

demonstrated that the truck-tire pipe does not crack, split, delaminate, or exhibit wall buckling

behavior even at deflections nearing 50 % . A truck-tire pipe, flattened to near 50 percent of its initial diameter but still able to withstand more load, is shown in Figure 13. These observations were made during the load deflection tests described above.

Table 5: Measured Pipe Stiffness

(a) 20 inch diameter Truck-Tire Pipe (5 %deflection = 0.05 x 19.5 = 0^{.98 in (2.5 cm))} _{1 74} 0.00014 0.00015

2 83 0.00004 0.00006

3 90 NM NM 4 101 0.00071 0.00073 6 73 0.00027 0.00031 8 97 NM ^NM

Average = 86

(b) 22.5 inch diameter Truck-Tire Pipe(5 % deflection = 0.05 x 22.6 =1.13 in (2.9 cm)) 7 0.00037 0.00040 9 NM NM

10 NM^NM

(c) 18 inch diameter corrugated polyethylene pipe (5 % deflection = 0.05 x 18 = 0.9 in (2.3 cm))

11 I46NA^NA

(d) 21 inch diameter corrugated steel pipe (5 % deflection = 0 .05 x 21 = 1.05 in (2.7 cm)) NA

12 I 106 I NA

• Steel, 21' 100 o Culvert 1, 20'

0 1111III11

0 123 4 56789

Figure 15: Stiffness Versus Deflection for 20 and 22.5 inch Truck-Tire, 21 inch Steel, and 18 inch Plastic pipes

Figure 16: Permanently deflected steel pipe

ENVIRONMENTAL STRESS CRACKING The environmental stress cracking requirement is specific to ethylene plastics and therefore

is not applicable to truck-tire pipes. BRITTLENESS AASHTO M 294-90 (section 7.7) specifies that corrugated polyethylene pipe shall not crack or split when tested, according to ASTM D 2444, by dropping a 5.5 pound (2.5 Kg) tup a vertical distance of at least 10 feet onto a pipe specimen . A tup is a weight of specified shape, in this case a blunt rod with a two inch diameter (Tup B, describedin ASTM D 2444). This test was not attempted because it is obvious that the truck-tire pipe, with 4 inch thick rubber walls, can withstand a far greater impact without cracking or splitting. FITTING REQUIREMENTS AASHTO M294-90 (section 7.8) specifies that fittings for corrugated polyethylene pipe shall not reduce or impair the overall integrity or function of the pipeline. Two truck-tire pipes can be joined with a flexible belt wrapped around the two abutting pipe ends and cinched in place with straps, as shown in Figure 3 and 4 . Many pipes installed to date have been joined with 6 inch

wide used conveyor belt material. However, any rubber or plastic flexible material at least 6 inches

(15.2 cm) wide and with length greater than 120 inches (3 m) can be used. It is recommended, however, that wraps of greater width, perhaps 10 inches (25.4 cm) or more, be used. In a few cases, poured concrete joints were used.

One concern related to the truck-tire pipe fittings is the ability of the flexible belt connection to impede the flow of water into or out of the pipe at joints . Thus, one study objective was to assess leakage potential (both infiltration and exfiltration) of the tire-pipe. Infiltration can cause soil at the outside surface of the pipe to seep into the pipe, while exfiltration can lead to erosion of soil away from the outside pipe surface . Either can eventually result in sufficient loss of soil around the outside of the pipe so that holes or cavities in the soil around the pipe occur. If enough erosion occurs, cave-ins can result . Leakage tests were conducted at the Mack-Blackwell Transportation Center at the University of Arkansas .

Existing specifications that are to some degree related to the situation of a tire-pipe culvert include ASTM C 443-85a(concrete culverts) andASTM C969-82 (longer sections of pipe).

ASTMC443-85a reads in part : "10.1 .1 Pipes in Straight Alignment-Hydrostatic pressure tests on joints shall be made on an assembly of two sections of pipe... Suitable bulkheads may be provided within the pipe

adjacent to and on either side of the joint, or the outer ends of the two joined pipe sections may be bulkheaded...Moisture or beads of waterappearing on the surface of the joint will not beconsidered leakage.. ."

Two types of test were scheduled for the tire-pipe . First, a single section was tested to check for leakage from between the sidewalls . Then, a test of joint leakage was conducted. Test methods for the tire-pipe were improvised, but were based on established tests.

Single-Section Leakage Test

Single-section pipe leakage tests were conducted outdoors in May, 1994 . The weather was dry, with daytime highs around 800 and the nighttime lows in the 50s°. The ends of a nominally 8 foot long (actually 100 inches) single tire pipe section were sealed with 3/4 inch plywood plugs at each end (Figure 17). Both plugs were recessed approximately 3.5 to 6 inches from the end. They were nailed into the pipe wall and sealed with silicon caulk . An initial attempt had been made to seal the pipe with plywood plugs over the ends, but a satisfactory seal could not be made due to the size of the undulations in the plane of the pipe-end. The inside diameter of the pipe varied from 23to24 inches. The variation was duetoundulations of the tire ridges. The inside distance

between the end plugs was about 90 inches.

An improvised manometer made from flexible tubing was inserted into one end plug, a ruler had been affixed to the plug surface, next to the tubing. At the opposite end plug, a hole had been cut near the top to allow a garden hose end to be inserted for filling. Because of the filling hole, it was impossible to fill the pipe to the top .

The pipe section was laid horizontally on level ground . The filling began, and leakage at both end plugs was observed. Leaking was noted at both the seams between the plug and the pipe wall, and in imperfections in the plywood itself. However, the leakage rate was insignificant when

compared to the filling rate, so the filling proceeded. The system was tight enough that the flow from the garden hose caused about 1 .5 inches of air-pressure head inside the pipe (as read from the manometer), so the rate of filling was decreased to minimize air pressure inside the tire-pipe section. The pipe was filled to the point that the manometer read 21-7/16 . At this point, the amount leaking at each end was collected over a known time period. The pipe walls were inspected for signs of leaking; an almost imperceptible and immeasurable amount of moisture was observed at one tire-wall joint. Because no sign of flow was observable, it could not be determined if the wall was seeping or if the moisture came from another source . The pipe was left to sit overnight.

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~~ ~i~~-_-:~e17

_~~ _~_~wr~'Sec~on Leakage Test

-~~~

The pipe was inspected the next morning. The manometer level was holding constant at 17

7/8 inches. No leaking was observable at either end, or in the side walls . It was hypothesized that over time, the water confined inside the pipe had caused the plywood plugs to swell, and self-sealed leaks. The hose was again inserted to fill the pipe backto the 21-7/16 level. As the pipe was filling, no leaking occurred at the "hole" end-plug, but the manometer end-plug resumed leaking. This time, the leaking seemed to come from one plywood split near the top, where a nail had been driven through the plywood into the tire wall . Leakage at this end was measured. No leaking was observed in the side wall. The pipe was again lefttosit overnight. Additional inspections were made on following days. No leaking or seeping from the tire-pipe walls was observed. Data recorded during the test are presented in Table 6 . The results of the single-section leakage test indicate that leakage through the sides of truck-tire pipes does not occur at measurable rates under open channel flow conditions, even when the pipe is not surrounded by soil. Two-Section Joint-Leakage Test

In June, 1994, two tire-pipes were placed end-to-end, while resting on wooden pallets, to prepare for the joint leakage test (Figure 18) . The test site was outdoors . The weather was dry, with daytime highs around 90°.

The dimensions of the tire-pipes were as described in the single-section test. The endjoint was wrapped with a 36 inch wide piece of conveyor belting. The belting was cinched-down with four separate lengths of aircraft-cable, two on each side of the joint . This cinching was done in an attempt to simulate the effect of banding placed around joints in the field. The far (or opposite) ends of the two tire-pipe sections were plugged with caulked plywood disks, as in the single-section test.

Even with the four separate cinches or bands around the joint wrap, water escaped from the joint as fast as it came in through the hose, so no rate of escape could be established . A close inspection of the tire-pipes' surface reveals considerable surface irregularity, with successive sidewall sections having somewhat different outer diameter, and the irregularity causing the rebar to span or bridge some of the individual sidewall edge-surfaces . This surface irregularity and rebar bridging makes it nearly impossible to make a tight connection with a conveyor belt strip.

The results of the two-section joint-leakage test indicate that significant leakage will occur when the pipes are not surrounded by soil, even when a 36 inch belt is used, cinched in four places. It should be noted that there was no soil surrounding the pipe or the joint. At actual tire-pipe installations, the ability of surrounding soil to act as a mud-seal around the joint could vary from site to site.

Table 6: Leakage Data from Test of Bead-sidewall Test

Date Time Activity Water Level Leak rate leak rate ₁ (inches) through plug, through plug, fill end manometer end

(1) (2) (3) (4) (5) (6)

5/16/94 3:30 PM initial fill 21-7/16 28 ml / 20 70 ml / 10 sec. sec.

5/17/94 9:30 AM inspect 17-7/8 no no measurable measurable

5/17/94 9:45 AM refill pipe 21-7/16 no 70 ml / 10 measurable sec.

5/17/94 3:00 PM inspect 19-1/2 no small trickle measurable

5/18/94 11:00 AM inspect 17-5/8 no no measurable measurable

5/19/94 12:00 noon inspect 17-5/8 no no measurable measurable

5/20/94 11:30 AM inspect 17-5/8 no no measurable measurable

1

REBAR CORROSION

This concern is unique to truck-tire pipes, because the bead-sidewalls which make up the pipe are held together by steel rebars . It is hypothesized that an important method of failure will be 1, 2, or 3 rebars yielding on exterior pipe sections, i.e., sections which protrude from either side of a driveway or roadway. The yielding of rebars on interior sections is not important because those pipes will be held in place by the pipe sections on either side. The surrounding soil will also provide some lengthwise support. Only exterior pipe sections are not supported on one end. Also, the section of pipe that protrudes from the roadway receives less soil support.

A rebar will fail when its cross-sectional area is reduced beyond the minimum necessary to withstand the load placed on the rebar by the bead-sidewalls and roadway traffic . Thus, in order to estimate the time torebar failure, it is necessary to estimate the force exerted on the rebar, the minimum area necessary to withstand the force, and the time required to corrode the rebar cross-sectional area to the minimum allowable area through the natural action of steel corrosion.

The force exerted on a typical rebar was determined experimentallyby attaching strain gauges to one rebar on each of five truck-tire pipes. Strain, i.e.,the change in length resulting from a given load divided by the length in the unloaded state, was measured at zero pipe deflection

and 5 % deflection, as shown in Table 5. Strains measured at zero deflection are caused only by the bead-sidewalls pressing against the rebars, and occur when no load is exerted on the pipe. It is important to note that the pipes are constructed by welding the rebars in place while the bead-sidewall are compressed by a hydraulic piston. When the compression force is removed, the bead-sidewalls press against the rebars, which keep them from expanding further. The strain measured at 5 % deflection is higher than the zero deflection strain because pipe deflection causes the pipes to elongate, thus further stretching the rebars.

The strain values reported in Table 5 vary substantially from rebar to rebar. For example, the zero deflection strain ranges from 0.00004 to 0.00071 m/m. This variability is another artifact of the method used to construct the truck-tire pipes . Once the 80 bead-sidewalls used to make a

single pipe section are compressed toapproximately 8 feet, four rebars are bent around the ends of

the pipe walls and welded in place . This leads to variability in the effective length of the rebar "bands". Thus, rebars "bands" that are short relative to the other rebars on a given pipe take more of the force from bead-sidewall expansion . Longer rebar "bands" take less force . Hence the variability found in Table 5. For each rebar the additional strain caused by a 5 % deflection of the pipe is minor, averaging only 0.000024 m/m. This indicates that little of the weight of roadway

vehicles will be translated to the rebars .

Strain can be used to estimate the tensile force exerted on a rebar using the equation

P=Ee A (1)

where: P = tensile force, pounds (Newtons) ; E = the average modulus of elasticity, psi (MPa), e

= strain, in/in (m/m); and A = the cross-sectional area, in2(m2). A typical value of E for rebars is

The rebar will yield when it is subjected to a stress greater than the maximum allowable stress, ate,assumed to be 60,000 psi (410 MPa). The area of a 3/8 inch rebar is 0.11 in2(7.13 x 10-5m2). Therefore, for a 3/8 in diameter rebar, the minimum allowable area can be estimated using the equation

P E F, A,-

Amax Amax where: Am= the minimum allowable cross-sectional area, in2(m2); amax= the maximum allowable stress, psi (MPa); and B = a constant which depends on units, 53.17 for English units, 0.0344 for metric units.

The time required to corrode a steel rebar to the minimum allowable cross-sectional area will depend on the steel corrosion rate, which depends more on soil conditions than steel composition. Uhlig and Revie (1985) report a corrosion rates of Bessemer steel in a soil that is relatively non corrosive (0.10 g/m2d), a soil that is highly corrosive (1 .95 g/m2d), and an average of several soils (0.45 g/m2d). Because steel composition is relatively unimportant to corrosion in soil, these rates can be applied to steel rebars. If the corrosion rate is constant then

_ -MA (3)

where: m = mass, grams; t = time, days; Rc = the corrosion rate, g/m2d; and SA = the surface area exposed to corrosion, m2. Based on this, a formula which can be used to estimate the time required to corrode rebars assumed to be smooth rods with a circular cross-section is

t = ^p(D02&^-Df) (4)

where: p = the density of steel, 7.87 x 106g/m3; Do = the initial diameter of the rebar, m; and Df = the final diameter of the rebar, m. The diameter is used instead of the cross-sectional area, because a circular cross section and uniform corrosion have been assumed . The initial diameter of the rebars is 3/8 inch (9.525 x 10-3m). The final diameter, i.e.,the diameter at which the rebar will fail, can be estimated based on the minimum allowable cross-sectional area, which in turn can

be estimated using equation (2) and the strain at 5 % deflection . Values of e and t for various corrosion rates and rebars are presented in Table 7 .

₁ FINAL REPORT ₁ Table 7: Estimation of Time to Rebar Failure for Various Soil Cor osivities

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1

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Corrosion Rate in g/m2/d^{Corrosion Rate in m/yr}

[Uhlig and Revie (1985)] [Wrangl6n (1985)]

High Average Low ^HighlyCorrosive ^Slightly

(1.95) (0.45) (0.10) (0.0001) (0.00003) (5x10'6)

(3) (4) (5) (6) (7) (8 167 751 70 232 1394 190 853 79 264 1582 93 419 39 129 777 140 631 59 195 1170 128 577 54 178 1070

Wrangl6n (1985) reports corrosion rates in terms of pro per 10 years . Converting these rates to pm per year, one gets 100, 30 and 5 mm/year for highly corrosive, corrosive, and slightly corrosive soils, respectively. In this case the time to failure is

where k = the rate of corrosion expressed as length per time, pin/year or gm/year. Times to failure calculated using equation (5) are also reported in Table 7 .

The times to failure reported in Table 7 are only very rough estimates, and should not be treated as highly accurate prediction. First, they are based on uniform corrosivity rates. Corrosion rates along the rebar with vary above and below the values reported in the literature . Because failure will occur if the cross-sectional area falls below the minimum acceptable at just one place in the rebar, failure will probably occur faster than reported in Table 7, for a given corrosion rate . Second, the corrosion rate in Table 7 may not apply to the soil within which a particular pipe is buried. Third, the rebars have been coated with a rust inhibiting paint, which, if effective, may extend rebar life beyond that reported in Table 7 . However, in spite of these uncertainties, the Table can be used to estimate whether rebar failure should be expected in days, years, decades or centuries. The estimates in Table 7 indicate that rebar failure can be expected within 20 to 70 years in highly corrosive soils, 90 to 200 years in average soils, and longer still in slightly corrosive soils. However, this does not mean that truck-tire culverts will last 200 years or more. This claim cannot be made because the long-term behavior of the rubber bead-sidewalls in soil is unknown .

Four actions can be taken to further prolong the life of truck-tire culverts in corrosive soils . First, larger diameter rebars can be used. For example, if 1/2 inch (1.27 cm) rebars are used, the expected lifetime of culvert 4 could be increase from 21 years to 39 years, based on a corrosion rate of 1.95 g/m2/d. Second, The rebars can be protected from corrosion with coating or by running the rebars through holes in the bead-sidewalls. Only two pipe sections with larger rebars or protected rebars are require per pipe run, as they are only required on the exterior pipe sections . Third, a corrosion resistant culvert made from some other material, perhaps plastic, could be used for the exterior pipe section, thus supporting the interior truck tire pipes in case of rebar failure . Similarly the exterior truck-tire pipe sections could be supported with concrete or other materials . ¹ Finally, it may be possible to reduce the tension in the pipes (through the manufacturing process) without significantly reducing the pipe stiffness . However, it appears that even without any of the measures listed above, the truck-tire pipe should perform well in corrosive soils .

In this section truck-tire pipe quality has been discussed in terms of workmanship, pipe dimensions, perforations, pipe stiffness, pipe flattening, environmental stress cracking, brittleness, fitting requirements, and rebar corrosion . In the next section, based on the truck-tire pipe inspections and testing, conclusions and recommendations concerning the truck-tire pipe are presented.

CONCLUSIONS AND RECOMMENDATIONS

The manufacture of each eight foot truck-tire pipe reuses the bead and a large portion of the sidewall of approximately 40 waste truck tires. Thus, the use of truck-tire pipes will reduce the amount of truck tire material deposited in landfills or illegal dumps . However, the remaining portion of the truck tire must still be reused, recycled, or safely deposited in a landfill . Shredding makes it easier to recycle or safely dispose of tires. Fortunately, removing the bead removes the part of the tire that is most difficult to shred.

Waste truck tires can usually be obtained at zero or negative cost. Thus, truck-tire pipes are expected to sell for less than corrugated steel, fiberglass, and plastic pipes. If truck-tire pipes perform well in actual use, the manufacture of truck-tire pipes will be an environmentally and economically sound activity. However, the weight, short section length, and thickness of the pipe walls will increase transportation and installations costs, and must also be considered.

The major goal of the research presented here is to evaluate the truck-tire pipe and delineate its appropriate use. Information obtained through conversations with pipe installers, site inspections of installed pipes, experimental tests of pipes, and theoretical analyses conducted as part of this research makes it possible to present a number of conclusions and recommendations concerning installation, expected performance, appropriate use, and advantages and limitations of the truck-tire pipes . INSTALLATION

Truck-tire pipes have been installed at about 30 sites in Oklahoma, Arkansas, and Texas, used almost exclusively for surface drainage under open channel flow condition . Visits to 26 of these sites gathered valuable information concerning the truck-tire pipes . Pipe users reported a number of issues concerning truck-tire installation .

The weight of each pipe section makes the truck-tire pipe more difficult to install than conventional thin-walled pipes. Truck-tire pipe sections are only 8 feet (2 .4 m) in length. Therefore, at least 3 or 4 are used to span the typical driveway or roadway . This:entails more joint connections than with conventional pipes, which come in longer lengths . The slope of the trench bottom must be uniform and sufficient to avoid localized flat spots inside the pipe, caused by pipe irregularity, i.e.,variation in outer diameter. Due to the thicker walls, tire-pipes require a slightly deeper trench than thin-walled culvert pipe of similar inside diameter.

The bedding procedures used on the pipes observed ranged from none to elaborate . It appears that procedures used for conventional pipes will work for truck-tire pipes. The tire pipes appear to perform well with very little cover. In fact cover was observed to be an inch or less at some locations.

1
1

1

Due to the irregular shape of the pipe ends and to pipe weight, getting a close connection is

difficult. So long as the pipe is produced with an undulating end, it is recommended that the

installer rotate each section 1/8 turn from the previous section, so that the "out" undulations mesh

with the "in" undulations by rotating a subsequent section by 1/8 the circumference.

Installation costs will probably be higher for the tire-pipe than for galvanized steel or

1 fiberglass pipe, because of the extra time required hoist the heavy sections (approximately 1200 pounds each), lay the sections closely, and wrap the connection. Thus, savings must be realized in purchase price, product life, and/or avoided disposal fees if truck-tire pipes are to offer a cost advantage over conventional pipes. FIELD PERFORMANCE Field performance was evaluated by interviewing pipe users and by inspecting pipe installations in the field. Most tire-pipes observed had all been installed in rural or small-town environments, ranging from a drive giving access toa field to a rural subdivision mad; most were on county roads. Traffic volumes at most sites were relatively light. A few of the pipe installation sites had endured some heavy-weight vehicle traffic, associated with nearby construction projects. Most of the pipes were place under dirt or gravel roads; one was under a low-type asphalt pavement.

Even though the surface inside the pipe is irregular, deposits observed inside the pipe were few and generally small. Many of the pipes had rather "clean" insides after a few months to more ₁ than 2 years of service.

In some cases erosion of the embankment near the pipe was observed. This may have been

caused by insufficient compaction of the backfill on the embankment slope, and subsequent surface

erosion of the side of the embankment. This type of erosion could happen with any type of

The numerous joints required by the shortness of the pipe sections need to be tight enough to prevent water and/or surrounding soil from flowing into the pipe or to prevent outflowing water from eroding soil surrounding the pipe. At most installations, a six inch wide used conveyor belt was wrapped around joints to form connections. Of approximately 90 joints observed in the filed, erosion of the road surface near a joint was observed at only 3 places, and the erosion observed was minor. However, none of the inspected pipes had been in use for more than approximately

2.5 years. That any erosion was observed at all indicates that care should be taken in installing the joint wrap; wider belts may solve this potential problem. Field inspection indicates that the truck-tire pipes are strong enough for typical culvert duty .

Several pipes served roads which had carried earth moving trucks during nearby construction projects. However, small "hairline" cracks in the surface over truck-tire pipes were noted at a number of sites. It is possible that these cracks result from slight vibration of the truck-tire pipes

whenever vehicles pass over them . There were no observable problems resulting from the limited cracking, even at sites where pipes had been in place for approximately 2.5 years.

No instances of damage to the rubber truck-tire culverts caused by fire were reported by users. However, the potential for damage due to fires caused by vandalism or accidents cannot be ignored. It is not known at this time how much effort would be required on the part of vandal to cause a damaging fire. APPROPRIATE SPECIFICATIONS

The specification that come closest to being applicable for the truck-tire pipe culvert is AASHTO M 294-90, "Standard Specification for Corrugated Polyethylene Pipe, 12-36 in . Diameter." The size range and use are applicable to the truck-tire pipe. Specifications that are applicable to-truck-tire pipes are workmanship, pipe dimensions, pipe stiffness, pipe flattening, and fitting requirements. Each is important to truck-tire drainage pipe quality.

Because the truck-tire pipe is made from a waste material with little pre-processing, it does not present the uniform appearance of pipes manufactured using virgin materials . The pipe should not have visible gaps between tire bead-sidewalls, nor should bead-sidewalls be split . Four rebars should be used to hold the bead-sidewall together, positioned at approximately 90 0 intervals about the pipe circumference.

Truck-tire pipe sizes are limited to truck tire sizes, i.e.,20 and 22.5 inch (50.8 or 55.9 cm) inner diameters. The average inner diameters for the nominal 20 and 22.5 inch truck-tire pipes are

19.5 and 22.6 inches, respectively (49.5 cm and 57.4 cm). The variability regarding the inner diameter does not present a problem for pipe connections, as it is accommodated by the flexible joint connection currently in use. The truck-tire pipes currently only come in nominal eight foot lengths. 20" nominal truck tire pipes measured had an average length of 97.6 inches (247.9 cm), while the 22.5" nominal truck-tire pipes measured had an average length of 98 .5 inches (250.2 cm).

Pipe stiffness at 5 % deflection for 19 .5 and 22.6 inches (49.5 and 57.4 cm) inner diameter pipes should be at least 38 and 35 psi, respectively . Testing conducted at Fears Structural Laboratory orrthe campus of the University of Oklahoma demonstrated that the truck-tire pipe stiffness exceeds these requirements. However, one 22.5 inch culvert had a stiffness at 5 % deflection of only 36 psi, just 1 psi greater than the required value . The low stiffness value measured for that culvert indicates a need for further tests with the 22.5 inch inner diameter pipes to (1) ensure that the required stiffness is always met, (2) determine if manufacturing variability or testing error caused the low value, and (3) suggest means to improve the 22 .5 inch pipes if necessary. However, all of the truck-tire culverts exhibited higher stiffness values over a wider range of deflection.

AASHTO M 294-90 specifies that it shall be possible to flatten corrugated polyethylene

pipe until the vertical inner diameter is reduced by 20 percent without the occurrence of cracking,

splitting, delamination, or wall buckling . Testing conducted at Fears Structural Laboratory on the

campus of the University of Oklahoma demonstrated that the truck-tire pipe does not crack, split,

delaminate, or exhibit wall buckling behavior even at deflections nearing 50 % .

AASHTO M 294-90 specifies that fittings for corrugated polyethylene pipe shall not reduce

or impair the overall integrity or function of the pipeline. Leakage tests were conducted at the

Mack-Blackwell Transportation Center at the University of Arkansas. In the single-section pipe

leakage test, the one section tested did not leak between the sidewalls. Significant leakage was

observed when a joint between two tire-pipe sections was tested. Both the irregularity of the tire-

pipe surface and the bridging effect of the rebars appeared to make it practically impossible to seal

the joint with conveyor belt wrapping. The potential for the leakage to cause a significant amount

of erosion of soil around the pipe over time cannot beignored. However, it is important to note

that this test was conducted without any soil surrounding the joint. The apparent success of most

truck-tire pipe joints observed in the field suggests that in many situations soil surrounding the pipe

It is hypothesized that an important method of failure will be 1, 2, or 3 rebars yielding on exterior pipe sections, i.e., sections which protrude from either side of a driveway or roadway. A rebar will fail when its cross-sectional area is reduced beyond the minimum necessary to withstand the load placed on the rebar by the bead-sidewalls and roadway traffic. Rough estimates based on assumed corrosion models and values indicate that rebar failure can be expected within 20 to 70 years in highly corrosive soils, 90 to 200 years in average soils, and longer still in slightly

corrosive soils. However, this does not mean that truck-tire culverts will last 200 years or more. This claim cannot be made because the long-term behavior of the rubber bead-sidewalls in soil is unknown. It appears that the truck-tire pipe should perform well in corrosive soils. ADVANTAGES AND LIMITATIONS In the majority of the cases, the installer/owner appeared to be pleased with the truck-tire pipe. The field investigations indicated that the tire-pipe works well in many rural road situations,

w

but does have some limitations. The main limitations are the higher cost of installation and the

potential for erosion through joints . The greater difficulty of installation would hopefully be outweighed by long-term performance and durability, but long term tire-pipe behavior will not be known for many years. Perhaps the erosion problem can be addressed by carefully installing the joint wrap and, if necessary, using a wider wrap . The lack of different sizes available is a limitation; however, multiple parallel runs of the truck-tire pipe can be, and indeed are used when greater capacity is required. The main advantages include low cost and diversion of waste from

disposal. An expected advantage will be long life, though this can only be proved through

demonstration. Experience and laboratory tests suggest that the exposed ends of truck-tire pipes will be able to sustain heavy loads and rebound without permanent deformation. Field inspection also indicates that the truck-tire pipes performwell with little ground cover. Overall, the inspected truck-tire pipe culverts appeared to be performing adequately.

FUTURE RESEARCH

Future research should address truck-tire pipe durability and joint connections, and the stiffness of the 22.5 inch nominal pipe. Durability tests should focus on corrosion of the rebars and degradation of the bead/sidewalls. Observation of installed truck-tire pipes should be made regularly over a number of years. Joint connections should be observed and tested under field conditions, for a variety of soils or flow rate, and for different wrap widths. If problems caused by joint leakage arise, then an improved joint connection should be developed . Finally, the stiffness of a number of 22.5 inch nominal pipes should be tested to determine whether it regularly exceeds stiffness requirements.

American Association of State Highway and Transportation Officials (1990) "CorrugatedPolyethylene Pipe, 12 to 36 in. Diameter", in Standard Specifications for TransportationMaterials and Methods for Sampling and Testing 15th Edition . American Association of State Highway and Transportation Officials: Washington, DC.

American Society for Testing and Materials (1993) "Circular Concrete Sewer and Culvert Pipe,Using Rubber Gaskets," ASTM C 443-85a, in 1993 Annual Book of ASTM Standards. American Society for Testing and Materials, Philadelphia, PA.

American Society for Testing and Materials (1993) "Standard Practice for Infiltration and Exfiltration Acceptance Testing in Installed Precast Concrete Pipe Sewer Lines", ASTM C 96982, in 1993 Annual Book of ASTM Standards, American Society for Testing and Materials: Philadelphia, PA.

American Society for Testing and Materials (1993) "Standard Test Method for Determination of External Loading Characteristics of Plastic Pipe by Parallel-Plate Loading", ASTM C 969-82,in 1993 Annual Book of ASTM Standards, American Society for Testing and Materials : Philadelphia, PA.

American Society for Testing and Materials (1993) "Standard Test Method for Determination of the Impact Resistance of Thermoplastic Pipe and Fittings by Means of a Tup (Falling Weight)", ASTM C 969-82, in 1993 Annual Book of ASTM Standards, American Society for Testingand Materials: Philadelphia, PA.

Wrangl6n, G. (1985) An Introduction to Corrosion and Protection of Metals, Chapman and Hall: NY.

Uhlig, H, and R. Revie (1985) Corrosion and Corrosion Control, Third Edition, John Wiley & Sons: NY

APPENDIX A: TRUCK-TIRE PIPE SITE INSPECTIONS

1. Site Location:

Site Description:
Date Installed:
Pipe Description:
Type of Connection:
Type of Road Over Pipe:
Road-Traffic Usage:

Pipe-Cover Thickness:
Condition:

Comments:

Photographs Taken:
Contact Person:

2. Site Location:

Site Description:
Date Installed:
Pipe Description:
Type of Connection:
Type of Road Over Pipe:
Road-Traffic Usage:
Pipe-Cover Thickness:
Condition :
Comments:

Photographs Taken:
Contact Person: