Thomas C. Sandford

Bio: Thomas C. Sandford is an academic researcher from University of Maine. The author has contributed to research in topics: Pile & Abutment. The author has an hindex of 10, co-authored 14 publications receiving 377 citations.

Shear strength and compressibility of tire chips for use as retaining wall backfill

Abstract: Scrap tires that have been cut into chips are coarse grained, free draining, and have a low compacted density, thus offering significant advantages for use as lightweight fill and retaining wall backfill. The engineering properties needed to put tire chips into use are presented. The properties determined for tire chips, from three suppliers, are gradation, specific gravity, compacted density, shear strength, compressibility, and coefficient of lateral earth pressure at rest. The 76-mm (3-in.) maximum size and high compressibility of the tire chips necessitated design and fabrication of custom-made testing equipment. The tests showed that the tire chips are composed of uniformly graded, gravel-sized particles that absorb only a small amount of water. Their compacted density is 0.618 to 0.642 Mg/cu m (38.6 to 40.1 pcf), which is about one-third that of compacted soils. The shear strength was measured in a large-scale direct shear apparatus. The friction angle and cohesion intercept ranged from 19 to 25 degrees and 8 to 11 kPa (160 to 240 psf), respectively. The compressibility tests showed that tire chips are highly compressible on initial loading, but that the compressibility on subsequent unloading and reloading cycles is less. The horizontal stress was measured during these tests and showed that the coefficient of lateral earth pressure at rest varied from 0.26 for tire chips with a large amount of steel belt exposed at the cut edges to 0.47 for tire chips composed entirely of glass-belted tires.

Full-Scale Field Trials of Tire Shreds as Lightweight Retaining Wall Backfill Under At-Rest Conditions

Abstract: A 4.88-m (16-ft), full-scale retaining wall test facility was constructed to investigate the use of tire shreds as backfill for conventional retaining walls. The facility can test backfill at at-rest and active conditions and is instrumental for measuring horizontal stress and interface shear. Tire shreds from three suppliers were tested. The results for at-rest conditions are presented. The average at-rest horizontal stress for tire shreds was about 45 percent less than expected for conventional granular backfill. Moreover, the at-rest horizontal stress was about the same for tire shreds from the three suppliers. Design parameters were developed by using two procedures. The first used the coefficient of lateral earth pressure and the other was based on equivalent fluid pressure. The horizontal and shear forces acting on the concrete face of the wall were used to determine the angle of wall friction, which ranged from 30° to 32° for tire shreds from the three suppliers.

Skew effects on backfill pressures at frame bridge abutments

Abstract: The abutments of frame bridges are integrally connected to the deck without expansion joints. Active soil pressures are normally considered in design despite the movement of the abutments into the soil from thermal expansion of the deck. Many abutments are located on a skew, but possible effects of this skew on the backfill soil pressures are not considered in design. To improve the knowledge of soil pressures behind a skewed integral abutment for use in designing this type of bridge, soil pressures were measured on an installed project for 33 months. The soil pressure measurements were taken using total pressure cells in the backfill on each side of the centerline for both abutments of a 20-degree skewed bridge in Maine. A total of 16 pressure cells plus temperature indicators have been monitored four times a day using a data acquisition system since October 1989. Expansion of the deck causes the pressure to increase well above the active conditions on the upper part of the abutment wall. Skew effects on the pressures that develop near the deck level behind the abutment wall of an integral abutment are substantial. When the greatest deck expansion occurs, the pressures at 3 m (10 ft) from centerline on the obtuse side reach almost three times the value at the corresponding distance on the acute side. The horizontal variation of pressure is greater than the vertical variation. A design envelope is proposed.

Repair of Wood Piles Using Prefabricated Fiber-Reinforced Polymer Composite Shells

Abstract: An effective method for combined environmental protection and structural restoration of wood piles in waterfront facilities is not available. The objective of the study presented in this paper is to survey the available methods for wood pile protection and structural restoration with the intent of developing an effective method. In addition to reviewing the available repair methods, a field inspection of a harbor in Maine was conducted to assess existing technologies. A wood pile repair method that utilizes bonded fiber-reinforced polymer (FRP) composite shells and a grouting material is proposed. Fiber, resin, adhesive, coating, and grouting materials are systematically analyzed to deliver the required system performance. Two fabrication methods for the FRP composite shells are discussed based on the experience gained in the fabrication of laboratory prototypes. Then a step-by-step procedure amenable for field installation is proposed, and a preliminary cost analysis is conducted to assess the feasibility of the proposed system.

Engineering properties of tire chips and soil mixtures

Abstract: The primary objective of the research described herein is to assess the pertinent engineering properties for reusing shredded scrap tires as a construction material for light-weight fill material in highway construction, for drainage material in highway and landfill construction, and for other similar applications. Reuse of scrap tires would not only provide a means of disposing of them but would also help solve difficult economical and technical problems. This paper presents the characteristics of shredded scrap tires and their engineering properties and behavior alone or when mixed with soils. The properties considered include compaction, compressibility, strength and deformability, and hydraulic conductivity. Described are new test procedures or modification of existing methods developed to characterize this unusual material.

Behaviour of tire shred - sand mixtures

Abstract: Tire shreds and tire shred – soil mixtures can be used as alternative backfill material in many geotechnical applications. The reuse of tire shreds may not only address growing environmental and ec...

Sand Reinforced with Shredded Waste Tires

Abstract: The objective of this study was to investigate the feasibility of using shredded waste tires to reinforce sand. Direct shear tests were conducted on mixtures of dry sand and shredded waste tires. The following factors were studied to evaluate their influence on shear strength: normal stress, sand matrix unit weight, shred content, shred length, and shred orientation. From results of the tests, three significant factors affecting shear strength were identified: normal stress, shred content, and sand matrix unit weight. A model for estimating the strength of reinforced soils was also evaluated to determine its applicability to mixtures of sand and tire shreds. When the model is calibrated using results from one shred content, it may be useful for estimating the friction angle for other shred contents. In all cases, adding shredded tires increased the shear strength of sand, with an apparent friction angle (ϕ′) as large as 67° being obtained. Shred content and sand matrix unit weight were the most significan...

Marine Application of Fiber Reinforced Composites: A Review

Abstract: Components and structures working in the marine environment are exposed to high stresses attributable to the action of wind, waves, and tides. Moreover, they have to face hostile and severe environmental conditions during their lifetime, being placed in the splash zone if not even submerged in saltwater. The application of polymer composites in marine systems has been the focus of intensive studies in the last decades, highlighting potential benefits given by the replacement of several components, such as ship hulls, propeller blades, wind, and tidal turbine blades, to cite but a few. The present paper reports the latest advances in this area, addressing the applications of advanced composites in ships and ship components, offshore oil and gas composites, marine renewable energy and underwater repairing.

Dynamic Properties of Granulated Rubber/Sand Mixtures

Abstract: Processed waste tires mixed with soils are applicable in lightweight fills for slopes, retaining walls, and embankments that may be subjected to seismic loads. Rubber's high damping capacity permits consideration of granulated rubber/soil mixtures as part of a damping system to reduce vibration. The dynamic properties of granulated rubber/soil mixtures are essential for the design of such systems. This research investigates the shear modulus and damping ratio of granulated rubber/sand mixtures using a torsional resonant column. Specimens were constructed using different percentages of granulated tire rubber and Ottawa sand at several different percentages. The maximum shear modulus and minimum damping ratio are presented with the percentage of granulated rubber. It is shown that reference strain can be used to normalize the shear modulus into a less scattered band for granulated rubber/sand mixtures. The normalized shear modulus reduction for 50% granulated rubber (by volumme) is close to a typical saturated cohesive soil. Empirical estimation of maximum shear modulus of soil/rubber mixtures can be achieved by treating the volume of rubber as voids.