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.

Many interface and sand-to-sand direct shear tests have been performed with a constant normal stiffness to investigate the effects of interface roughness, normal stiffness, soil relative density, initial normal stress, and cyclic displacement amplitude on the soilinterface response. It is demonstrated that the patterns of behavior in these tests are similar to those observed in model pile tests and that the constant normal stiffness (CNS) condition is required to account for the effects of the volume changes that occur as soil adjacent to a pile is sheared. In dense sands that tend to expand in volume when sheared, the shear and normal stresses developed are significantly higher than for constant normal load (CNL) conditions and increase with higher values of normal stiffness. For loose sands that compress when sheared, the stresses are lower than in CNL tests and decrease for higher values of normal stiffness. The CNS tests replicate the reduction in shear stress during displacement-controlled cycling and the subsequent loss of capacity reported for model and full-scale piles. The reduction of skin friction during cycling and the subsequent loss of pile frictional capacity is found to be greatest for loose sands, high normal stiffness, large displacement amplitudes, and rough interfaces.

Although the CPTu offers many advantages over the SPT, it may be desirable in some instances to use SPT-based experience of soil behavior. An algorithm is presented here for estimation of equivalent N60 values directly from the CPTu without resort to soil sampling. The proposed algorithm is based on data and trends reported in the literature; the algorithm is tested against new data obtained for cross-calibration of the CPTu/SPT in a wide variety of soil types, penetration resistances, and depths. As part of the evaluation of the algorithm, replicate trials of both SPT and CPTu were carried out. The data show the CPTu is five times more precise than the SPT. Further, the equivalent N60 derived from the CPTu using the proposed algorithm is shown to be at least as reliable as values directly determined by the SPT; the much improved precision of the CPTu outweighs the uncertainty in the CPTu/SPT calibration, and the calibration in itself averages the testing error of the SPT. The proposed algorithm is tested for bias against depth, soil type, penetration resistance, and friction ratio; the algorithm is unbiased. Cumulative probability density functions are given for repeatability of the SPT, the CPTu, and an estimation of equivalent SPT values from the CPTu.

The main factor affecting the drained residual strength measured in the Bromhead ring shear apparatus is the magnitude of wall friction developed along the inner and outer circumferences of the confined specimen. The magnitude of wall friction increases with the depth of the remolded specimen, and thus the plane of least wall friction occurs at or near the soil/top porous stone interface. As the top porous stone settles into the specimen container, the wall friction influencing the shear plane increases, causing an increase in the measured residual strength. A new specimen container is proposed for the Bromhead ring shear apparatus that allows a remolded specimen to be overconsolidated and precut prior to drained shearing. This minimizes settlement of the top platen and the horizontal displacement required to reach a residual strength condition. As a result, a multistage test can be conducted without excessive settlement and thus wall friction occurring in the new specimen container. The use of a multistage test significantly reduces the time required to establish a drained residual failure envelope. The use of an overconsolidated and precut specimen also provides a better simulation of the field conditions that lead to a large post-peak decrease in drained strength in clayshales, claystones, and mudstones, and residual strengths that are in excellent agreement with field case histories.

Stationary pluviators generally use one or more sieves to spread the sand flow exiting from the hopper through one or more holes over the desired area. On the other hand, traveling pluviators do not need a sieve or mesh because in this case it is possible to move an opening or a nozzle over the area of interest. Traveling pluviators are preferable to stationary pluviators, especially in the case of well-graded cohesionless soils, because they provide more uniform specimens. However, traveling pluviators have drawbacks, specimen layering being the most relevant. This technical note illustrates an experimental procedure to reconstitute large specimens of well-graded sands using a traveling pluviator. The effects of specimen layering on mechanical soil properties became negligible with this technique as it was possible to assess performing a series of CPT tests with both a standard cone and a 20-mm cone.