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Dana N Humphrey

Bio: Dana N Humphrey is an academic researcher from University of Maine System. The author has contributed to research in topics: Subgrade & Falling weight deflectometer. The author has an hindex of 10, co-authored 17 publications receiving 459 citations.

Papers
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Journal Article
TL;DR: In this article, the engineering properties needed to put tire chips into use are presented, including gradation, specific gravity, compacted density, shear strength, compressibility, and coefficient of lateral earth pressure at rest.
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.

137 citations

Journal ArticleDOI
TL;DR: In this paper, a 4.88m-high retaining wall test facility was constructed to test tire shreds as retaining wall backfill, and the front wall of the facility could be rotated outward away from the fill and was instrumented to measure the horizontal stress.
Abstract: A 4.88-m-high retaining wall test facility was constructed to test tire shreds as retaining wall backfill. The front wall of the facility could be rotated outward away from the fill and was instrumented to measure the horizontal stress. Measurement of movement within the backfill and settlement of the backfill surface during wall rotation allowed estimation of the pattern of movement within the fill. Tests were conducted with tire shreds from three suppliers. The horizontal stress at a rotation about the base of 0.01H was about the same for tire shreds from the three suppliers. Moreover, horizontal stress at this rotation for tire shreds was approximately 35% less than the active stress expected for conventional granular backfill. Design parameters were developed using two procedures; the first used the coefficient of lateral earth pressure and the other was based on equivalent fluid pressure. The inclination of the sliding plane with respect to horizontal was estimated to range from 61 deg (1.06 rad) to 70 deg (1.22 rad) for the three types of shreds.

115 citations

01 Jan 1998
TL;DR: The use of tire shreds in three highway projects is described in this paper, which demonstrate that tire shred can be used as lightweight fill for retaining walls and embankments, and properly designed tire shred fills do not experience a deleterious self-heating reaction.
Abstract: Use of tire shreds in three highway projects is described. In the first project, tire shreds were used as a compressible inclusion to reduce pressures on a rigid frame bridge. Earth pressures were reduced by more than 50%. In the second project, a 4.3-m thick zone of tire shreds was used as lightweight fill to improve global stability of a bridge approach fill founded on weak clay. In addition, the tire shreds reduced horizontal pressure on the bridge abutment. In the third project, two layers of tire shreds, each up to 3.05 m thick, were used as lightweight fill for a highway embankment founded on weak clay. These were the first projects to incorporate design features to minimize internal self-heating of tire shred fills. Measured temperatures showed that no deleterious self-heating occurred. These projects demonstrate that tire shreds can be used as lightweight fill for retaining walls and embankments. Moreover, properly designed tire shred fills do not experience a deleterious self-heating reaction.

43 citations

Proceedings ArticleDOI
TL;DR: In this paper, the authors present design guidelines to limit internal heating of TDA fills, and nine projects have now been built in accordance with the guidelines, and internal measurements show that TDA temperatures are similar to background soil levels.
Abstract: The low in-place density of tire derived aggregate (TDA) makes them attractive for use as lightweight fill for embankments constructed on weak ground and backfill for retaining walls. TDA, also known as tire shreds or chips, are scrap tires that have been cut into 50 to 300mm (2 to 12 in.) pieces. There are many examples of projects that have successfully used TDA as lightweight fill. However, as illustrated by three projects built in 1995 that experienced internal heating reactions, car is needed to properly design and construct TDA fills. The underlying cause of these problems was a combination of oxidation of exposed steel belts and freshly cut surfaces on rubber pieces. The lessons learned from these projects resulted in design guidelines to limit internal heating of TDA fills. Nine projects have now been built in accordance with the guidelines. Internal measurements show that TDA temperatures are similar to background soil levels, indicating the effectiveness of the guidelines. Moreover, effective construction specifications have been developed that often result in lower construction costs than competing lightweight fill materials.

36 citations

11 Mar 1998
TL;DR: In this paper, the authors determine design criteria for using tire shreds as retaining wall backfill, which is done by testing a granular control fill and tire shredded from three suppliers in a full scale retaining wall test facility.
Abstract: Waste tires cut into 25 to 305-mm (1 to 12-in.) pieces yield a material that is coarse grained, free draining, and has a low unit weight, thus offering significant advantages for use as retaining wall backfill. This project is a continuation of Phase I, in which the engineering properties of tire shreds were determined. The purpose of this project was to determine design criteria for using tire shreds as retaining wall backfill. This was done by testing a granular control fill and tire shreds from three suppliers in a full scale retaining wall test facility. Tests were performed for at-rest and active conditions. For the at-rest condition, the horizontal earth pressure, interface shear, and compressibility were measured, at surcharges up to 35.9 kPa (750 psf). As much as 7% strain occurred during surcharge application with an additional 3% occurring due to time-dependent settlement. The majority of time-dependent settlement was completed in 50 days. For the active condition, the horizontal earth pressure and deformation within the backfill were measured; tests were performed at the 35.9 kPa (750 psf) surcharge. The horizontal earth pressure for tire shreds was 35% to 45% less than expected from conventional granular fill. The coefficients of lateral earth pressure (K sub 0 and K sub a) were found. K sub 0 for tire shreds decreased with depth and fell within a small range. At the maximum surcharge and a depth of 2 m (6.5 ft), K sub 0 ranged from 0.32 to 0.33. K sub a for tire shreds was constant with depth and fell within a small range. At 0.01H of outward wall movement, K sub a ranged from 0.22 to 0.25. The interface shear strength between tire shreds and a concrete faced wall ranged from 30 deg to 32 deg.

32 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the authors present the characteristics of shredded scrap tires and their engineering properties and behavior alone or when mixed with soils, including compaction, compressibility, strength and deformability, and hydraulic conductivity.
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.

371 citations

Journal ArticleDOI
TL;DR: Tire shreds and tire shreds can be used as alternative backfill material in many geotechnical applications, such as soil mixtures as discussed by the authors, which can not only address growing environmental and ec...
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...

366 citations

Journal ArticleDOI
TL;DR: In this paper, the feasibility of using shredded waste tires to reinforce sand was investigated, and three significant factors affecting shear strength were identified: normal stress, shred content, and sand matrix unit weight.
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...

324 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the shear modulus and damping ratio of granulated rubber/sand mixtures using a torsional resonant column and found that 50% granulated tire rubber is close to a typical saturated cohesive soil.
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.

203 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a synthesis of the dynamic strain-dependent properties of the commonly used soil/rubber mixtures, which are necessary in any seismic design, and propose generic normalized shear modulus and damping ratio versus shearing strain amplitude curves for dry mixtures of sand/Rubber (SRM) and gravel/rubbers (GRM) appropriate for the engineering practice.

183 citations