Mark R. Muszynski

Determination of Maximum and Minimum Densities of Poorly Graded Sands Using a Simplified Method

Evaluation of maximum and minimum (limit) density values of sands is important in geotechnical engineering. Limit density values are important physical properties needed to provide a more complete description of sands, and they are required when evaluating relative density of soils. The conventional methods for determination of limit densities are generally costly, require relatively large sample volumes, and are time consuming. A simplified method for determining limit densities of clean poorly graded fine to medium sands was developed. The simplified method is easy to perform, requires less sample volume, and is faster than the conventional methods for determining these properties. Results of this study indicate that the simplified method gives limit density values comparable to those obtained using conventional methods for clean poorly graded fine to medium sands. Limitations of the simplified method are discussed.

Earth Pressure Measurements Using Tactile Pressure Sensors in a Saturated Sand During Static and Dynamic Centrifuge Testing

The performance of tactile pressure sensors used in centrifuge testing involving pressure measurements of laterally-spreading soils against a large, rigid, foundation element is evaluated. The tactile pressure sensor measurements were consistent with hydrostatic pressures measured by pressure transducers under most testing conditions, and agreed with at-rest geostatic pressures provided that the measurements were made against a rigid surface (i.e., no relative soil-structure movement). However, measured pressures decreased substantially under some conditions when shearing forces were transmitted to the pressure sensors. Dynamic pressures (minima and maxima pressure spikes) measured by the tactile pressure sensors differed from pressures measured by pore pressure transducers and, when uncorrected, they were considered unreliable. A dynamic pressure correction was developed to address this issue. Lastly, a comprehensive verification testing program was recommended for each unique centrifuge test configuration to improve interpretation of pressure sensor output.

Repeatability of Centrifuge Tests Containing a Large, Rigid Foundation Subjected to Lateral Spreading

Four centrifuge tests involving liquefaction-induced lateral spreading of loose sand against a large, rigid foundation are summarized with regard to the repeatability of ground motions, porewater pressures, and lateral displacement magnitudes. The base input motions delivered to the models exhibited a large coefficient of variation (COV) of 0.27, chiefly as a result of variations in the shaker hydraulic system, rather than differences in model construction (which exhibited a COV of 0.07 for the relative density of the loose sands). Variations in ground acceleration response, porewater pressure response, and lateral displacement magnitudes were dominated by variations in base motions, with COV values ranging from about 0.01 to 0.47. Nevertheless, more than 90 % of the COV values were less than 0.30, consistent with or less than the COV of the base motions. In addition, the measured COV values are consistent with COV values of other geotechnical measurements reported in the literature. This is especially encouraging because centrifuge tests are relatively complex boundary tests, and many COV values reported in the literature involve element tests. Based on these findings, one must carefully monitor and control base motions (input to the soil container) in order to obtain repeatable results in a centrifuge testing program.

Effects of Particle Shape and Gradation on the Results of Miniature DCP Tests in Sand

Miniature dynamic cone penetrometer (mDCP) tests were completed to investigate the general effect that particle shape and size gradation may have on penetration resistance. This testing provides preliminary results for planning purposes for a future testing program that will include full-scale dynamic cone penetrometer (DCP) testing on sands having varying physical properties and characteristics. Generally, the blow counts per increment became greater with increasing relative density for dry and moist sands, as expected. Angular sands increased the blow counts, whereas rounded sands yielded lower blow counts for the same relative density and grain size distribution. At high relative densities, the effect of particle shape was generally more pronounced than at lower relative densities for a specimen of given particle shape. Gradation appeared to have an effect for the moist specimens, although a defined trend was not observed. The moist specimens exhibited greater resistance penetration than did the oven dry specimens. Scale effects are discussed and considerations for future full-scale testing are identified.

Passive wedge formation and limiting lateral pressures on large foundations during lateral spreading

AbstractFour centrifuge tests supplemented by calibrated numerical simulations were performed to evaluate passive wedge formation and limiting lateral pressures imposed on a large, stiff foundation...

A Critical Review of Permeable Asphalt Behavior and Performance to Guide Application to Arterial Streets in Cold Climates

The purpose of this review paper is to summarize the literature on the behavior and performance of permeable asphalt (PA), examine the feasibility of applying PA to arterial streets in cold climates, and present recommendations to improve the success of PA in wider applications. The review presented here required examining existing data sources and scientific journal papers, along with interviewing professionals who have conducted studies or dealt with PA in a variety of locations. The conclusions and recommendations drawn from this evaluation are intended to be guidelines for agencies looking to potentially apply PA to arterial streets in cold climate regions. Literature selected for review included PA sites that had several of the following characteristics: high volume traffic, cold climate region, abundant annual snowfall and extreme average temperatures, used sand, salt, plows, and deicers in winter maintenance activities, and experienced studded snow tires. In addition, sites reviewed also had subgrade soils with adequate infiltration rates, deep groundwater, relatively little annual precipitation, and area frost depths of 24 in. below finished grade. It was not possible to have each case study reviewed address all criteria, but all of these factors were considered important to the review to provide accurate literature comparison, and they allowed us to ascertain and present general behavior and patterns regarding PA. In addition, a summary of recommendations on the application of PA to arterial streets in cold climates with respect to water quality treatment performance, hydrologic performance, materials and durability, and maintenance practices are also presented.

Downslope ground movements during liquefaction-induced lateral spreading in centrifuge testing

Downslope displacements resulting from lateral spreading during fourteen centrifuge tests performed at the NEES facility at Rensselaer Polytechnic Institute (RPI) are summarized. The centrifuge tests were conducted to model lateral spreading of a gently sloping soil profile, triggered by an earthquake, with several configurations and features (such as the presence of a large, rigid foundation element and/or a deflection wall) in the path of downslope soil movement. The lateral displacements in the free-field area of each test (measured on the container laminar rings) are presented for all test configurations and compared with several existing empirical and semi-empirical approaches to estimate lateral spreading displacements. In general, the Newmark (1965) sliding-block approach with liquefied shear strength ratios yielded the most reasonable estimates of measured displacements.