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Waste tires have been a disposal problem in the past and are continuing to accumulate throughout the U.S. today. Using shredded waste tires as a lightweight fill material for road construction has proven to be a beneficial use of this waste product. Shredded tires have been used as a lightweight fill material in Minnesota, Colorado, Oregon, Washington, North Carolina, Virginia, and Wisconsin. Minnesota began using shredded tires as a lightweight fill material in 1985 on logging roads through areas with weak soils. This report documents seven sites in Minnesota that used shredded waste tires as lightweight fill. Shredded tires were proven to be a viable form of lightweight fill because they are relatively lightweight, inexpensive and non-biodegradable. In general, the material is very elastic, very porous, contains good vibration damping properties, and is easily compacted. On the downside, shredded tires lack set design standards and specifications. The report also documents some of the environmental testing completed on shredded tires to date.

The Minnesota Department of Transportation (Mn/DOT) currently uses the Engineering News Record (ENR) formula to monitor pile driving. This formula, first developed in 1893, uses an oversimplified model of the pile driving system to predict the pile capacity in the field. Since the beginning of this century, however, engineers have known that this formula neglects many complexities involved in the pile driving system including wave action, hammer energy loss, pile flexibility, and different soil resistance factors. This report is a record of the initial use of the Pile Driving Analyzer (PDA) by Mn/DOT. A sophisticated analog/digital device with high computational speed, the PDA uses one-dimensional wave propagation theory to calculate the forces acting on the pile that resist penetration. The PDA gives the test engineer immediate soil resistance, pile or shaft stress, and hammer efficiency results during pile driving, restriking, or impact testing. More than two-thirds of state transportation departments use the PDA, currently in worldwide use on more than 2,500 projects each year. For this project, we planned to receive training on the PDA and use it to monitor pile driving on selected projects in hopes of incorporating this more modem method of measuring pile capacity into Mn/DOT's pile driving program.