Vincent P. Drnevich

Modulus and damping of soils by the resonant-column method

The resonant-column method, a relatively nondestructive test employing wave propagation in cylindrical specimens, is used to obtain modulus and damping of soils as functions of vibratory strain amplitude and other factorssuch as ambient confining stress and void ratio. Descriptions of the apparatus, calibration procedures, testing procedures, and aids for data reduction are given for apparatus which propagate either rod compression waves or shear waves or both. Data reduction aids include graphs for a wide range of apparatus conditions and include a computer program that covers all admissable boundary conditions.

Resonant-column testing: Problems and solutions

The resonant-column test is a relatively nondestructive test employing wave propagation in cylindrical specimens of soil and rock. Test results are usually quite accurate, but in some cases insufficient coupling exists between specimen and apparatus or specimens are too stiff for a given apparatus, or both. A criterion is given to evaluate whether a coupling problem exists and solutions are suggested. Procedures for evaluating limiting specimen stiffness and maximum strain amplitude capabilities are given. Solutions for reducing air migration problems during long-term tests are presented. Finally, a simple method for estimating strain amplitudes during a test is demonstrated for both shear and axial compression.

Improved Techniques for the Constant-Rate-of-Strain Consolidation Test

This paper presents several improvements on the constant-rate-of-strain consolidation (CRS) test. The improvements include a rational approach for selecting strain rate and a change in testing procedures to aid in: (I) the selection of strain rate and (2) obtaining more reasonable values of the coefficient of consolidation in initial phases of testing. Based on theoretical work by Wissa, a strain-rate equation is developed that is a function of permeability, liquidity index, and desired maximum pore pressure ratio. The change in procedure involves a method of conducting a permeability test in a back-pressure consolidation apparatus and then initiating consolidation loading without removing the gradient associated with the permeability test. Results of multiple-loading-cycle CRS tests on three clay soils with widely differing characteristics are used to establish the coefficient for the equation. The equation is an improvement over the procedure in ASTM Test for One-Dimensional Consolidation Properties of Soils Using Controlled-Strain Loading (D 4186) which bases the selection only on liquid limit. The proposed equation accounts for specimen permeability and stiffness.

Numerical and optimization techniques applied to surface waves for backcalculation of layer moduli

This paper contains two methods of determining the pavement moduli and thicknesses using a computer program written in FORTRAN 77. The first method, a simple finite difference technique, is developed for the analysis of generalized Rayleigh waves in multilayered elastic media. The method, which leads to an eigenvalue problem, is very effective in determining theoretical dispersion curves for pavement systems modeled as layered composite plates with free surfaces at both top and bottom or free surface of the top and rigid base at the bottom. Backcalculation of moduli and thicknesses is done by an optimization routine developed by Powell [1] based on least squares criterion. The second method determines a theoretical dispersion curve based on Knopoffs technique [2]. Since phase velocities of the waves observed experimentally on pavement structures are complex, suitable modification of Knopoffs algorithm for the geologic model has been made by the authors to account for this effect. For optimization, the same technique is used as mentioned above. Numerical results obtained in the two cases show excellent agreement with previously published solutions obtained by other theories.

Acoustic emissions in geotechnical engineering practice

This volume contains 7 papers on monitoring method in rock engineering presented at a symposium on the application of acoustic emission techniques in soil mechanics. One paper is abstracted separately.

SASWOPR: A PROGRAM TO OPERATE ON SPECTRAL ANALYSIS OF SURFACE WAVE DATA

The spectral-analysis-of-surface-waves (SASW) method is a nondestructive method for determining elastic properties and thicknesses of pavement systems as well as natural soil deposits. This method consists of three phases: (1) collecting data from field testing; (2) converting these data to a dispersion curve; and (3) determining the shear wave velocity profile by inverting the dispersion curve. The computer program SASWOPR, developed at the university of Kentucky, performs the second of these three phases. SASWOPR is an easy-to-use interactive program that provides great flexibility to operate on field data in the process of generating a single dispersion curve (surface wave phase velocity versus frequency or wavelength). This graphic-oriented program is written in compiled BASIC and runs on a personal computer.

Seismic Analysis and Retrofitting Priorities for Highway Bridges on Earthquake Priority Route System in Western Kentucky

The contents of this report reflect the views of the authors who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the University of Kentucky, the Kentucky Transportation Cabinet, nor the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. The inclusion of manufacturer names and trade names are for Identification purposes and are not to be considered as endorsements.

Normalized Stress-Strain for Undrained Shear Tests

Normalized stress-strain curves are obtained by use of maximum shearing stress to normalize shear stress and reference strain to normalize shear strain. Reference strain is defined by initial tangent shear modulus and maximum shearing stress. This paper defines initial tangent shear modulus and maximum shearing stress to be functions of effective stress state. Consequently, the normalizing parameters vary with stress points along the stress path. An incremental procedure is established whereby normalized stress-strain curves can be obtained. These curves are relatively independent of effective stress path and are nearly identical to those obtained from drained tests. This method shows promise for correlating results from drained and undrained triaxial tests with results from other types of shear tests.