In 1990, Oregon trucked 580,000 tyres up to 200 miles to shore up slide-prone US 42; net cost $10 a ton, and federal engineers called it the largest tyre fill for a landslide correction project

Discarded car tyres usually create a waste management problem, but Oregon engineers found an unusual use for thousands of them during a highway repair project in 1990. A slope along a road embankment was unstable and adding more regular soil would have put more weight on ground that was already moving. Instead, the Oregon Department of Transportation (ODOT) replaced part of the heavy soil embankment with shredded scrap tyres, a lighter material that cut the load on the unstable slope. The work took place in 1990 on US 42, the Coos Bay-Roseburg Highway, about 25 miles west of Roseburg in southwestern Oregon. ODOT’s report lists the route as Oregon state route 35. The Federal Highway Administration (FHWA) later cited it as the largest known use of shredded tyres in a landslide correction project.Highway construction reactivated an existing landslideThe project was carried out in 1990 on US Highway 42, also known as ODOT Highway 35 along the Coos Bay-Roseburg route about 25 miles west of Roseburg in southwestern Oregon, which is referred to as Oregon State Road 35 in the ODOT engineering report. Modification of the embankment through Highway upgrading led to the reactivation of an old landslide underneath the road due to the increased load. The need for a repair measure that could stabilise the slope without increasing its load required a design whereby part of the soil embankment was replaced by shredded chips. The soil from excavation was used to create a counterweight at the bottom of the slope. ODOT documented the work in its February 1991 report, Experimental Project: Use of Shredded Tires for Lightweight Fill. Four suppliers delivered 580,000 shredded tyresThe job needed about 5,800 tons of shredded tyres, roughly 580,000 tyres. Four suppliers trucked them to the site from 150 to 275 miles away, according to the 1993 paper by Richard J. Upton and George Machan in Transportation Research Record 1422. The chips arrived in 100-cubic-yard trucks, each carrying 28 tons. Workers placed them in three-foot lifts and compacted each lift with a D-8 dozer. Handling the material caused some trouble. Exposed steel wire in the shreds punctured some of the dump-truck tyres used on the job. The 1993 paper by Upton and Machan covers the supply and construction in more detail.Oregon recycling program reduced the material cost to $10 perOregon’s Department of Environmental Quality (DEQ) backed the project through a program that reimbursed the productive use of scrap tyres. The shredded material cost $30 per ton and DEQ refunded $20, bringing the material cost down to $10 per ton. Placing and compacting it added $8.33 per ton, for an installed cost of $18.33 per ton. The reimbursement made shredded tyres a practical option for the repair.After construction, the tyre fill got a three-foot compacted soil cap on the top and side slopes. The road surface went on top: 23 inches of aggregate base under 8 inches of asphalt pavement. The thickest part of the tyre embankment was about 12.5 feet. Under the weight of the cover, it settled about 20 inches, roughly 13 percent of its original thickness.ODOT monitored the structure with slope inclinometers, piezometers, settlement plates and survey hubs. The 1993 study found that the pavement’s initial deflection was about double the deflection over an earth embankment.FHWA identified it as the largest known landslide-correction projectThe project appeared in the FHWA’s User Guidelines for Waste and Byproduct Materials in Pavement Construction. The guidelines called Oregon’s use of about 580,000 scrap tyres the largest known use of shredded tyres in a landslide correction project. That record covers landslide repairs only, not every highway embankment that used recycled tyres. The FHWA also set up another project in Colorado where about 400,000 to 450,000 tyres were used in an interstate Highway embankment. The repair conducted in Oregon showed that old tyres could be used as a lightweight material for construction purposes, especially when normal soil puts pressure on the unstable land.You use AI every day. Now get your AI Quotient. Take the AIQ test.