Measurements of Solid Spheres Bouncing Off Flat Plates

Recent years have seen a substantial increase of interest in the flows of granular materials whose rheology is dominated by the physical contact between particles and between particles and the containing walls. Considerable advances in the theoretical understanding of rapid granular material flows have been made by the application of the statistical methods of molecular gas dynamics (e.g., Jenkins and Savage (1983), Lun et al. (1984)) and by the use of computers simulations of these flows (e.g., Campbell and Brennen (1985), Walton (1984)). Experimental studies aimed at measurements of the fundamental rheology properties are much less numerous and are understandably limited by the great difficulties involved in trying to measure velocity profiles, solid fraction profiles, and fluctuating velocities within a flowing granular material. Nevertheless, it has become clear that one of the most severe problems encountered when trying to compare experimental data with the theoretical models is the uncertainty in the material properties governing particle/particle or particle/wall collisions. Many of the theoretical models and computer simulations assume a constant coefficient of restitution (and, in some cases, a coefficient of friction). The purpose of the present project was to provide some documentation for particle/wall collisions by means of a set of relatively simple experiments in which solid spheres of various diameters and materials were bounced off plates of various thickness and material. The objective was to provide the kind of information on individual particle/wall collisions needed for the theoretical rheological models and computer simulations of granular material flows: in particular, to help resolve some of the issues associated with the boundary condition at a solid wall. For discussion of the complex issues associated with dynamic elastic or inelastic impact, reference is made to Goldsmith (1960) and the recent text by Johnson (1985)

Random Displacement Modulus and Damping Determination

Modulus and damping values were determined for both undisturbed and remolded silty sand specimens by cyclic triaxial methods utilizing both sinusoidal and random displacement stroke control. Remolded specimens were prepared at 3 different dry unit weights using a preparation technique that gave the same formation factor as the undisturbed specimen. Results indicated that the random displacement method tends to produce results which are similar to those obtained by the sinusoidal procedure at shearing strain levels less than 10-1 %. At shearing strain levels greater than 10-1 % the random displacement method gives lower modulus and higher damping ratio values when compared to the sinusoidal procedure. In addition, stress history effects as demonstrated by the location of the cycle in the record being analyzed were observed not to be important over the sample unit weights investigated

Coastal Bluff Retreat at Big Lagoon, California

Big Lagoon, located 30 miles north of Eureka, California is formed behind a bay barrier built across the mouth of a drowned river valley. To the south of the bay the beach follows rising wave cut slightly cemented sand and gravel sea cliffs and terminates at the south end of Agate Beach. The retreat of these sea cliffs and its effect on property development along the top of the cliff is the focus of the paper. Measurements of bluff retreat in this area have been documented extensively from November 1941 to March 1986 through ground surveys and air photos. Review of the data indicates that the retreat rate is not constant along the cliff but has either been decreasing or remaining the same over the last 45 years. Using information on the rate of retreat, a method is developed to predict the cliff erosion in the future

Response of Non-Saturated Soil to Cyclic Loading

The response of partially saturated and dry sand materials under cyclic loading is controlled by the compressibility of the pore fluid. For dry sand the limiting axial and volumetric strain occurs within 5 to 15 cycles of load application and is a function of the number of cycles of cyclic stress, relative density, and effective consolidation pressure. In addition the axial strain is shown to be independent of the consolidation stress ratio for loose sand and decreases with increasing consolidation stress ratio for dense sand under a constant cyclic stress

Site Specific Seismic/Geologic Hazards Risk Zoning

A site specific risk zoning study was conducted on a Junior College Campus near Eureka, California, USA to evaluate the potential seismic/geologic hazards due to the presence of a 1 km wide low angle thrust fault system. Issues addressed to determine the level of risk at any location on the campus include: land sliding, earthquake ground shaking, ground surface rupture and deformation, lateral spreading, liquefaction, differential settlement, and tsunamis. Based on these potential hazards, a micro-zonation model was developed based on 13 different zones and 5 levels of risk. Information for use in this model was collected using a combination of paleo seismic trenches, geophysical surveys and soil borings. This information was then combined to develop a map of risk zones within the campus. This map provides site specific land use recommendations to assist the college in locating appropriate sites for future campus expansion

Dynamic Shear Modulus of Soft Silt

This paper presents the geotechnical properties of soft silt obtained from the Greater Shanghai Region of the People\u27s Republic of China. Fundamental correlations of shear modulus, damping ratio, shear stress, shear strain with varying consolidation pressures are determined in the laboratory by cyclic simple shear tests. A comparison is made between laboratory test results, in situ cross-hole test results and the building code data proposed by the Shanghai Municipal Bureau. Finally, a comparison of the laboratory data on Shanghai silt with other published data on sands and clays is presented and discussed

Structural properties of epitaxial {\alpha}-U thin films on Ti, Zr, W and Nb

Thin layers of orthorhombic uranium ({\alpha}-U) have been grown onto buffered sapphire substrates by d.c. magnetron sputtering, resulting in the discovery of new epitaxial matches to Ti(00.1) and Zr(00.1) surfaces. These systems have been characterised by X-ray diffraction and reflectivity and the optimal deposition temperatures have been determined. More advanced structural characterisation of the known Nb(110) and W(110) buffered {\alpha}-U systems has also been carried out, showing that past reports of the domain structures of the U layers are incomplete. The ability of this low symmetry structure to form crystalline matches across a range of crystallographic templates highlights the complexity of U metal epitaxy and points naturally toward studies of the low temperature electronic properties of {\alpha}-U as a function of epitaxial strain

Probabilistic Estimation of Site Specific Fault Displacements

The College of the Redwoods (CR) located near Eureka, California would like to upgrade a series of existing buildings that are unfortunately located on secondary faults associated with the active Little Salmon Fault (LSF) zone. In the early 1990’s a deterministic value of the maximum dip-slip displacement that had occurred on one of these secondary faults located beneath the southeast building corner of the former library was measured to be 1.7 feet. This displacement was resolved into approximately 1.5 feet horizontal offset and 0.8 feet of vertical offset, based on the secondary fault plane dip. Geologically, it has not been possible to establish the actual dates of the occurrence of the displacements on the observed faults, therefore it was assumed that they all had occurred within the last 11,000 years. The structural engineer for the project has indicated that it was not possible to design for the observed ground displacement of 1.7 feet. This limited study was undertaken to assess the variation of ground displacements that were observed over the area of ground occupied by CR’s Administration, Science, and former Library buildings. The purpose of this study was to evaluate the reasonableness of using a deterministically determined maximum value of displacement in estimating, and designing mitigations for, the structural response, or whether a probabilistic approach could be utilized. The only data available within the limited time frame allowed for the study was from a series of trench logs made as part of a project for locating building sites on the campus in the early 1990’s. As a first step the frequency distributions of both horizontal and vertical displacements located in a volume of soil comprising the area occupied by the above buildings to a depth of 14 feet were examined. The 14 feet was the maximum depth of the trenches used to provide data for the study. Probability density functions (PDF) versus displacements were developed based on the frequency distributions. The area under the PDF curves between given displacement intervals represents the probability of occurrence (POC) of that displacement. A cumulative probability of occurrence for a displacement interval can be determined by adding the individual POC’s. Based on this it was estimated that a horizontal displacement of ≤ 1.0 foot has a probability of 89% of occurring in the next 11,000 years at the site. In contrast, a vertical displacement of ≤ 1.0 foot has a probability of 88% probability of occurrence

Use of Microzonation to Site Facility on Low Angle Thrust and Associated Fault Bend Folding

The campus of the College of the Redwoods is located completely within the Little Salmon Fault Zone, designated by the State of California as an active fault. The College has been extensively investigated for fault rupture and other seismic hazards in 1989, 1993, 1997, 1998, and 1999. The Little Salmon Fault Zone bounds the College and consists of two main northwest-striking, northeastdipping, low-angle thrusts. The west splay daylights along the southwest edge of the campus and projects beneath it. A recurrence interval of 268 years and slip rate of 5+/-3 mm/yr is estimated by CDMG. Individual dip-slip displacements along the west trace are reported to be 12 to 15 feet (3.6 to 4.5 m). Movement on the Little Salmon fault (LSF) is accompanied by growth of broad asymmetric folds in the upper thrust sheet resulting in surface rupture, localized uplift and discreet fault-bend fold axial surfaces. College of the Redwoods is located approximately 8 miles (13 km) south of Eureka and 25 miles (40 km) north-northeast of Cape Mendocino and the Mendocino Triple Junction (MTJ) in northern California. The \u27MTJ is the point of transition fi-om strike-slip faulting of the San Andreas transform system to low-angle thrust faulting and folding associated with the convergent margin of the Cascadia Subduction Zone. Campus infrastructure is located along the base of the Humboldt Hill Anticline (HHA), a major faultbend fold of the Cascadia fold and thrust belt. A new learning resource center (LRC) is proposed for a location 400 feet (120 m) northeast of where the west trace of the LSF daylights and 200 feet (60 m) above the low-angle fault plane. Building setback and design recommendations to mitigate for both fault rupture hazards and fault-generated folding hazards are presented