No abstract

Hydrogeological and geochemical investigations were conducted on four fractured Champlain Sea clay deposits in Eastern Ontario. The results from water level monitoring, maximum seasonal variations, and hydraulic head profiles revealed a hydraulically active fractured zone existing at all four sites. The depth of this fractured zone varies from site to site, ranging from 3.2 to 6.0 m. Slug test analysis indicated that bulk hydraulic conductivity values in the upper fractured zone range from 1.8 × 10−8 to 2.0 × 10−5 m/s. In contrast, the measured hydraulic conductivity values from the deepest piezometers range from 8.2 × 10−10 to 1.4 × 10−9 m/s. The geochemical analysis indicated the presence of three hydrochemical facies: a shallow "active" facies, a deep "inactive" facies, and an intermediate "transition" facies. The presence of tritiated groundwater well below the groundwater table indicates that the upper fractured zone at all four sites is hydraulically active. Key words : fractures, Champlain Sea clay, in situ testing, hydrogeology, geochemistry, hydraulic conductivity.

The disposal of scrap tires has become a major environmental concern. The reuse of scrap tires in the reinforcement of earth structures can provide an attractive solution in reducing the number of used tires disposed in overcrowded landfills. This paper, the second in a series of three papers, discusses the behaviour of slopes reinforced with scrap tires and proposes design recommendations. A mat-reinforced slope can either fail by pull-out of the reinforcement or due to rupture of the attachment tying the tires. A large number of pull-out tests were performed on whole tires and tires with one sidewall removed embedded in sand and cohesive backfill. The pull-out resistance of tire mat reinforcement was primarily governed by the effective shear strength of the soil, and therefore it can provide an efficient means of reinforcement. However, large displacements were required to fully mobilize the ultimate pull-out capacity which must be considered in design.Key words: pull-out tests, scrap tires, reinforced slope, performance, design guidelines.

A reinforced earthfill was constructed using approximately 10 000 scrap tires. Water samples were collected from a drainage system installed below the tire-reinforced earthfill and analyzed for chemical quality. Additional tests on water quality were performed in laboratory test columns in which tire chips were embedded in sand or clay to provide a conservative estimate of the potential release of toxic compounds. Field monitoring of the effluent indicated that no significant adverse effects on groundwater quality had occurred over a period of 2 years. Laboratory batch tests performed on tire chips embedded in sand provided evidence of an increase in solution of certain metal elements which in some cases exceeds their respective drinking-water standards. This increase was attributed to the exposed steel reinforcement found in the tire chips. The amount of organic compounds leached from the tire chips decreased with the number of exposure periods or pore volumes flushed through the soil.Key words: whole scrap tires, water quality, tire chips, field investigation, laboratory lysimeter tests.

The satisfactory disposal of scrap tires is a major environmental problem worldwide. This waste occupies valuable space in landfill sites, and tire stockpiles pose serious health and fire hazards. The use of scrap tires as reinforcement for construction of retaining walls and slopes is a viable method towards reduction of this waste. This paper describes the construction of a 57 m high × 17 m wide instrumented test fill, comprising both retaining wall and reinforced slope sections. Approximately 10 000 whole tires and tires with one sidewall removed, tied together with polypropylene rope, were used in both cohesionless and cohesive backfills. The testing program also included plate loading tests, field pull-out tests on tire mats, water-quality assessment in the field and laboratory, and other complementary laboratory testing. This first paper, in a series of three, demonstrates the practical feasibility of constructing reinforced earth fills using scrap tires. Results of large plate load tests and the field behaviour with particular reference to the design of the retaining wall sections are presented. The paper emphasizes the role of negative wall friction in increasing the active thrust when the retaining wall becomes more compressible than the backfill. Recommendations for the design of retaining walls using scrap tires are presented.Key words: scrap tires, earth reinforcement, retaining walls, reinforced slopes, plate load test, construction, performance.