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.

A laboratory apparatus for measuring the chemicoosmotic efficiency coefficient, , for clay soils in the presence of electrolyte solutions is described. A chemico-osmotic experiment is conducted by establishing and maintaining a constant difference in electrolyte concentration across a soil specimen while preventing the flow of solution through the specimen. The chemico-osmotic efficiency coefficient is derived from a measured pressure difference induced across the specimen in response to the applied concentration difference. The effective diffusion coefficient (D*) and retardation factor ( R d ) of the electrolytes (solutes) also can be determined simultaneously by measuring the diffusive solute mass flux through the specimen until steady-state diffusion is achieved. Experimental results using specimens of a geosynthetic clay liner subjected to potassium chloride solutions indicate that the measurement of may be affected by soil-solution interactions, as well as by changes in the induced chemico-osmotic pressure difference due to solute diffusion. As a result, should be evaluated using the induced pressure difference at steady state. The time required to achieve a steady-state response in induced pressure difference is related to the time required to achieve steady-state diffusion of all solutes, and may be affected by the circulation rate at the specimen boundaries. The circulation rate should be sufficiently rapid to minimize changes in the boundary concentrations due to diffusion, but sufficiently slow to allow measurement of solute mass flux at the lower concentration boundary for evaluating D* and R d . FIG. 1-Measured head differences (⌬H) across a kaolinite specimen as a function of externally imposed flow rates (Q/t) and the ratio of NaCl concentrations at the specimen boundaries (C B /C T ) (replotted after Olsen 1969).

A study is presented of potential errors in, and methods of interpreting, the results of cantilever-type, piezoceramic bender element tests for measuring the shear wave velocity of laboratory soil specimens. Interpretations based on the first direct arrival in the output signal are often masked by near-field effects and may be difficult to define reliably. Interpretations based on characteristic points or cross-correlation between the input and output signals are shown to be theoretically incorrect in most cases because of: (1) the effects of wave interference at the boundaries; (2) the phase lag between the physical wave forms and the measured electrical signals; and (3) non-one-dimensional wave travel and near-field effects. Interpretations based on the second arrival in the output signal are theoretically subject to errors from non-one-dimensional wave travel and near-field effects. Differences in Vs values obtained by the different interpretation methods are illustrated analytically and experimentally.

Great efforts have been made to understand and determine the stress parameters of unsaturated soils. However, this requires elaborate laboratory tests, which are both difficult and time consuming to perform. A hypothesis for determination of the shear strength of unsaturated soils is suggested. The hypothesis suggests a simple way of determining the shear strength based on the water retention curve and the angle of internal friction. Values of shear strengths have been taken from the literature and compared with shear strengths calculated according to this hypothesis. The shear strengths obtained from the hypothesis are in surprisingly good agreement with those found in the literature. The suggested hypothesis is critically examined and its limitations discussed. Finally, a reasonable way of applying the hypothesis in engineering practice is proposed.

Shearing rate is among the most important factors affecting the undrained shear strength of clays. In particular, for seismic or storm-wave loading conditions, the shearing rate is much higher than that used in many common laboratory or field tests. The testing program described here evaluates the effect of peripheral velocity on the undrained strength inferred from the shear vane test. The study was conducted on a lightly cemented bentonite-kaolinite mixture manufactured in the laboratory, which possesses many characteristics similar to those of natural materials. Results show that the shear strength increases with increasing peripheral velocity, while the residual shear strength seems to be nearly independent of rotation rate.

An experimental study aimed at a direct comparison of the undrained behavior of sand using specimens reconstituted by different techniques is presented. It is shown that at identical initial void ratio and effective stress state, the moist-tamped sand is potentially liquefiable, but in the water-deposited state may even be dilative. Water-deposited specimens are shown to be very uniform in contrast to the large nonuniformities that usually occur on moist tamping, rendering their results questionable from the standpoint of laboratory element tests. A direct comparison of the behavior of truly undisturbed sand specimens retrieved by in-situ ground freezing and their corresponding reconstituted counterparts after consolidating to identical initial states is also presented in support of the contention that the fabric that ensues on water pluviation closely simulates that of the natural alluvial and hydraulic fill sands, enabling the use of reconstituted specimens as substitutes for the expensive undisturbed frozen specimens for material characterization.

The critical state is arguably the most robust criterion for strength design, including post liquefaction strength. The conventional triaxial test is used for the determination of critical state parameters; however, it is time-consuming and the required set of tests is relatively expensive for common geotechnical tasks. A simplified test procedure is developed to determine the critical state line in sandy soils. The procedure is reliable, economical, and fast. In order to verify the simplified test procedure, results are compared against critical state parameters determined in conventional triaxial tests. The comparison shows very good agreement between critical state parameters obtained with the suggested procedure and those gathered with triaxial testing. Limitations are identified.

The mechanisms controlling the liquid limit of montmorillonitic and kaolinitic soils are different. The observation that the liquid limits obtained by both the conventional percussion method and the cone penetration method differ quite appreciably from each other at low and high plasticity ranges indicates that the mechanisms dominating the two testing procedures are different. The analysis of the results obtained from the present experimental investigation, and the results available in the literature prove that the viscous shear resistance primarily controls the percussion method of testing, and that the frictional shear resistance dominates the cone method of testing. Since the viscous shear resistance is primarily due to the double-layer held water, which is characteristic of montmorillonitic soils, and the liquid limit of montmorillonitic soil is primarily governed by the diffuse double layer thickness, the percussion method is well suited to montmorillonitic soils. Likewise, as the interparticle frictional resistance is due to the mode of particle arrangement in addition to mineral frictional characteristics, and the same primarily controls the liquid limit of kaolinitic soils, the cone method suits kaolinitic soils better.