---

---

---

---

---

---

---

---

Highway Safety Publications Catalog. Articles on Road Engineering, Road Maintenance & Management, and Injury Litigation. Information and consulting for the Automobile and Road User, as well as for law professionals in accident investigations.
TranSafety's free consumer journal for automobile and road users, three subscription journals on road maintenance, engineering, and injury litigation, and highway safety publications catalog. See our free consumer journal for automobile and road users, three subscription journals on road maintenance, engineering, and injury litigation, and a highway safety publications catalog.

Using truck tires in the manufacture of culvert pipe reduces the need for landfill space, eliminates a fire hazard, and deprives mosquitos of breeding sites. Moreover, recycled-tire culverts offer an initial cost advantage over traditional pipe materials; however, their increased weight, shorter sections, and thicker walls result in higher installation costs. The present study of installed waste-tire culverts determined that the pipe was working with few problems. Tests showed that although the pipe sections themselves did not leak, joints between pipe sections have the potential for leakage that may cause soil erosion. Future research is needed on pipe durability, steel reinforcing bar (rebar) corrosion, and joint connection integrity. Summarized here is a report by researchers J. L. Gattis and Jess W. Everett entitled "Evaluation of Culvert Pipe Made from Waste Truck Tires." The report appeared in the Transportation Research Board's Transportation Research Record 1541, Structures, Culverts, and Tunnels published in 1996. This research was funded by the Oklahoma Alliance, Center for Resource Conservation and Environmental Research, and the Mack-Blackwell National Rural Transportation Study Center at the University of Arkansas, through a grant from the U.S. Department of Transportation. Truck-tire pipe, used in Arkansas, Oklahoma, and Texas for surface drainage in open channel flow conditions, had not been independently tested. Therefore, the objectives of this research were to: determine how truck-tire pipe performed in the field and assess leakage potential. MANUFACTURING TIRE PIPE Heavy truck tires are often shredded before disposal, a process that may hasten the wearing of shredding equipment. One solution to the cost of replacing shredding equipment is the manufacture of drain pipe from waste truck tires. The process also reduces the demand on landfill space. Pipes are made by cutting the bead and sidewall from the tread. Eighty of the resulting discs are stacked and compressed into a tube about eight feet long. Rebar treated with a rust inhibitor is wrapped lengthwise and welded around the pipe.

FIGURE 1: Fabrication of truck-tire pipe: (a) 80 truck-tire beads and sidewalls stacked on from, (b) beads and sidewalls compressed by piston to approximately 2.5 m, (c) beads and sidewalls secured by four welded rebars ste 90 degrees apart The range of tire sizes determines the pipe diameters available. Although cost-effective, using a waste material does not produce the uniform appearance that the pipe might have if made from new materials. PERFORMANCE ISSUES: FABRICATION TO INSTALLATION The researchers compared truck-tire pipe with galvanized corrugated steel and fiberglass pipe. Prices ranged from $5.25 to $6.00 per linear foot for either steel or fiberglass, if purchased in large quantities. Used oil-well pipe, available in some areas, sells for about $7.00 per linear foot. The purchase cost of truck-tire pipe, however, is $3.00 to $5.00 less per linear foot. Because it takes longer to install than galvanized or fiberglass pipe, installation costs for truck-tire pipe are higher. Installation time for truck-tire pipe may be to two to three times longer than for other pipes. Tire Pipe Manufacturing Issues The manufacturing process described above results in a pipe with an uneven end because the rebars pinch the stack of tire disks. A flat end would be preferable for joining the pipe sections. Another issue is the advisability of using thicker rebar. Increased rebar diameter would make the pipe last longer. The manufacturer prefers 9.5 mm rebar, because it bends more easily than larger sizes. Shipping and Handling Issues Truck-tire pipe is heavy; it weighs about 150 pounds per linear foot, and standard eight-foot sections weigh 1200 pounds. Damage during transport may occur if the pipe is dragged across other pipe sections or dropped on the end. Installers can also damage the pipe if it is flexed laterally, so they must be careful when placing it in a ditch. Some rebar welds have broken during installation. A backhoe can hoist the pipe with a chain or rigid bar passed through it. Although one county reported that the pipe was too heavy and awkward to handle, most pipes were not damaged during preinstallation handling.

Installation Issues Since tire pipe is new, its installation procedures are still evolving. These installation issues were discussed: site preparation procedures, the type of bedding, if any, jointing procedures, amount of cover needed over the pipe, and installation cost and time requirements. Site Preparation Procedures At one site crews reported that irregularities in the pipe surface required a smoother ditch than galvanized pipe, because determining the pipe slope by looking at it in the trench was difficult. A muddy ditch also made the pipe harder to install. Due to its greater wall thickness, tire pipe must have a deeper trench than thin-walled pipe with a similar inside diameter. Some road crews reported having to raise the road surface to allow for a deep enough ditch. Bedding Procedures Truck-tire pipes can be bedded similarly to other types of culvert. Types of bedding reported to the researchers included: installing the pipe directly on the dirt surface, using crushed stone, and encasing the pipe in concrete at a low-water crossing.

Joint Connection Procedures The short length of truck-tire pipe means it takes several sections to cross an average roadway. Joints must be tight enough to keep surrounding water and soil out and to keep pipe contents in. Most tire-pipe joints were wrapped with conveyor belt or geotextile cloth strips. Some were fastened with plastic ties. One crew welded rebar across the joints. Some crews butted the pipes together with no other connection. Because of the irregular pipe ends, it was difficult for installers to create snug joints. Also, the use of chains to lower the pipe required crews to leave room between pipe sections so they could remove the chains. One researcher suggested that installers rotate each pipe section one-eighth turn to avoid matching up the indentations caused by the rebar bands. Pipe Cover In only one situation was shallow installation a problem. The researchers suggested that the pipe be installed with enough cover to allow for road maintenance, such as grading. PERFORMANCE EVALUATION: FIELD EXPERIENCE The researchers visited 26 installation sites, mostly on country roads in rural areas or small towns. Usually, traffic volumes were light. Most pipe installations consisted of one or two pipe runs of three or four pipes under dirt or gravel roads. Pipe performance criteria studied included:

Water Flow The irregular surface did not seem to create debris deposits, even after more than two years. Sediment observed in the bottom of some culverts appeared to be caused by the pipe flow-line being too low or by erosion upstream. In some places, vegetation had been caught between the rebar and the pipe wall. Erosion In the few cases where researchers observed road embankment erosion near a pipe end, it appeared that the cause was "insufficient compaction of the backfill on the embankment slope, and subsequent surface erosion on the side of the embankment." Of the approximately 90 joints observed, researchers found three cases of road-surface erosion, possibly caused by gaps at the pipe joints. It was suggested that a wider wrap might solve this problem. At one site, the truck-tire pipe remained when other types of pipe washed out, perhaps due to the tire pipe's extra weight. At another site, however, the tire pipe washed out immediately during heavy rain, but did not create any problems after reinstallation. Loads and Deflection The researchers observed two instances of pipe deflection (deformation, or deviation from roundness). In one case, an overweight vehicle had driven over the culvert. Improper backfilling or insufficient soil compaction might also cause these deflections. Cover and Flexure The pipe installations had cover depths ranging from one to two inches to more than eight inches. Some roads showed hairline cracks at the installations, possibly caused by crossing traffic vibrating the pipe. No problems were observed as a result of the cracks.

Rebar Durability At one site the rebar had given way after a culvert installation, perhaps due to an inadequate weld. Researchers suggested that pipe failures may also result from rebar corrosion. Fire Damage Although no tire pipe damage was found due to fire, the research team recognized the potential for fire damage caused by vandals or accidents. LEAKAGE TESTS Leakage, either from outside or inside a pipe, can cause erosion that could result in cave-ins. The researchers conducted tests on single sections and joints. The single-section wall leakage test took place outside in dry weather at 80 degrees F. with a pipe section sealed with plywood plugs nailed and caulked six inches from the pipe ends. No leaks were observed from the pipe walls. The researchers concluded that "leakage through the truck-tire pipe walls should not occur at measurable rates under open channel flow conditions." The joint-leakage test was outside in dry weather at 90 degrees F. Researchers joined two sections of pipe with 36-inch-wide conveyor belting and cinched it with aircraft cable to simulate a field installation. The open pipe ends were plugged with caulked plywood as above. Water leaked from the joint as fast as it entered the pipe, so researchers were unable to set a rate of escape. They did, however, observe that because of the tire pipes' irregular surfaces and slightly different outside diameters, they were unable to make a tight connection with the conveyor belt material. They surmised that "significant leakage will occur when the pipes are not surrounded by soil," but that "[a]t actual tire-pipe installations, the ability of surrounding soil to act as a mud-seal around the joint could vary from site to site." FUTURE RESEARCH Galvanized pipes may last from 20 to 25 years, and fiberglass pipes may last 50 years. To learn the lifespan of truck-tire pipe, more research should be conducted. Rebar corrosion and degradation of the rubber should be studied at regular intervals over time. Joint connections should be tested under field conditions and in a variety of soils and flow rates. While acknowledging that resulting changes would add to manufacturing costs, the project team suggested future research into ways to make pipe ends flat so they can be joined more tightly. One suggestion was to make the pipe from reconstituted rubber and construct it with formed ends. This would eliminate the need for rebar and allow ends to be butted more closely for a more watertight seal. Also, constructing the pipe with holes at the mid-point for attaching hoisting chains would allow lifting from the middle rather than wrapping chain around the ends. Again, the ends could then be laid together more tightly. Copyright © 1997 by TranSafety, Inc. Back to the Road Management Journal Index