The reduced number of contacts also led to greater variability of the toe load because shear failure at a handful of contacts can rapidly cause chains of contacts distributing loads through the particle assemblages to fail. As a result, both the inner frictional and end bearing areas are directly proportional to the platen spacing. As described in Chapter 2, the proportion of the potential energy that is converted to stress wave energy is characterized by the rod energy ratio ERr. The question of whether short rod corrections should be applied is really a question of whether the blow count is controlled by the initial impact energy, or the total transferred energy i. Examples of grain size effects defined in this manner are presented in chronological order of publication below. Energy correction procedures represented in the data set range from the use of typical rod energy ratios to direct energy measurement. It should be noted that the uncertainties calculated using these equations does not account for the effects of the inherent spatial variabilty of soils.
Students who complete dissertations involving basic or applied research in psychology and law are encouraged to apply for these awards. The data from all of the samples follow a single trend with the onset of plugging occurring when the internal platen spacing decreases below roughly 5 to 8 times the mean particle size. Output from the simulations included parameters such as the end bearing and friction forces acting on the sampler, the soil plug height and the patterns of particle displacement around the platen s. As described in Chapter 2, the proportion of the potential energy that is converted to stress wave energy is characterized by the rod energy ratio ERr. Very little is known about the magnitude, rate of dissipation or effect of excess pore pressures generated during SPT.
Energy, kJ ft-lb SPT The three stages of shear zone development observed in the 4. The potential energy that disxertation transformed due to permanent set of the rods will only be detected if the force and velocity measurements are made at the bottom of the rods and the weight of the rods is included in each force measurement i.
The trend of penetration energy increasing with platen spacing that was observed in Figure 7. He observed that sample disturbance was often directly due to partial or full plugging of the sampler. Based on experience it is suggested that stress wave energies recorded under those conditions using modern FV instrumentation would produce a standard deviation in the order of 0.
Nancy stolle dissertation
Of these, seven were man-made fills, four were mine tailings and five were volcanic deposits. Because stress wave energies are typically recorded at the top of the rod string and force baselines are typically determined prior to each hammer blow, while the hammer is suspended from the mast, most FV stress wave energies will include the potential energy transformed due to the set of the hammer but disesrtation of the rods.
The range of correlation factors recorded for a given D50 in Figure D50 mm 0.
Equivalent impact formulae for donut and safety hammers derived in Appendix A are: In general, plugging is considered to be more likely to occur during quasi-static sampling than dynamic sampling. Many students moved on to professorships, postdocs, graduate school, professional training or exciting jobs.
Gravels Some of the very high and low values of CD measured in gravels can be attributed to Dr values falling outside of the range of 0.
A dissedtation of hammer kinetic energy and stress wave energy measurements is compiled in Chapter 4, and used to investigate the relationship between these two quantities. The maximum calculated value of ERr is the correct value to use to calculate ERr avg.
Paikowsky suggested that the development of a soil cone ahead of the sampler, as noted by Hvorslevwas a natural extension of the development of passive arches in the lower portion of the soil plug. A Monte Carlo simulation is useful for demonstrating the manner in which these uncertainties will combine, and for predicting the resulting distribution of rod energy ratios. For this reason, and due to the fewer number of tests for which soil gradation is available, it is believed to be reasonable to neglect the effect dissertaiton soil gradation at this time.
Solid lines show equivalent Normal distributions. In contrast, diesertation studies are well suited for parametric studies and provide complete knowledge of the factors affecting the results at all times. Prior to release of the hammer, the energy in the system consists of the potential energy of the hammer, which is commonly calculated disserttion to the plane of impact.
The data from study C were originally described by Morgano and Liang and were made available for review by Morganopersonal communication. It seems likely that this relationship is related to shear zone thickness. Prior to hammer release. Simulations were performed using single platens to represent one half of a sampler or a pair of stollle to represent the full cross-section of a sampler.
Nancy stolle dissertation
During DEM simulations, each element is independent and unattached to adjacent elements Figure 7. Was named Karl W. This method was discounted by authors of early energy studies, who found that the ETR was too variable to be of use. It is suggested that a more balanced approach is to use the measured values with the caveat that the G75 data are more susceptible to error.
The direct measurement and ETR approaches were both shown to be clearly superior to the typical value approach, but roughly equivalent to each other in terms of result uncertainty. Assuming the estimate provided is appropriate for a velocity energy ratio of 0.
Because Log 1 is equal to zero, the y-intercept is equal to the value of CD corresponding dissertatiom a mean grain size of 1. This corresponds to 6. The experimental data exhibit a slope break well before the 7 mm mean grain size indicated in the numerical results. There are standard procedures for determining emax and emin for a given soil.
Repeat measurements and those representing volcanic soils, cemented soils and mine tailings were excluded.