The platens possess no curvature in the third dimension. Dual platen penetration energy was also observed to increase with mean particle size for a given platen spacing. The T-gravel data points with CD values of and correspond to Dr values of 0. This is a conservative assumption, as ERr avg almost certainly has a higher probability of assuming a value of 0. 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.
In general, however, piezocone data recorded in clean sands typically show little or no deviation from the original pore water pressure profiles, while those recorded in finer sands or silts do. The final plug lengths provide an indication of the severity of the plugging that occurred during sampler penetration, but it is more instructive to compare Fi gu re 7. He notes, however, that the upper limit for use of the SPT is likely about 5 mm. Numerical simulations of particulate behavior were conducted in order to gain insight into the processes contributing to the observed variation. The ETR values for these data points are plotted as a function of rod length in Figure 4. The three intermediate samples not shown demonstrated behaviour between these end-members.
Taylor series expansion of Equation 8. In gravelly sands or fine gravels, the practitioner may use short-interval equivalent SPT blow counts or switch to an LPT. The recommended procedure is detailed in Figure 5.
The efficiency with which the hammer kinetic energy is transferred to the drill rods can thus be quantified by the energy transfer ratio ETRdefined as: The use of typical rod energy ratios for energy correction has the potential to produce highly unreliable N60 values. Many of the factors that control the magnitude of energy corrected blow counts e. The sampler is then retrieved and the sample used for soil classification and laboratory testing purposes.
The 7propagation of uncertainty from energy measurements to the final energy corrected blow count is investigated in Chapter 5 and the proposed energy correction procedure is shown to be superior to traditional procedures. These issues range from repetition of data between sets, and use of averaged data versus individual measurements to differing energy correction procedures between studies.
Nancy stolle dissertation
The average velocity energy ratio ERv avg is equal to 0. New best-fit relationships forced through this point were determined for each type of LPT.
They prepared dense sand samples 20 Figure 2. Dissertatiob the change of slope is related to plugging effects, the PFC2D study results support the use of a critical sampler-grain size ratio for differentiating between plugged and partially plugged penetration modes. The Nnacy of the portion of the soil that is finer than 0. Cohesionless soils containing no clay are then classified based on GSD parameters including the effective grain size D10mean grain size D50coefficient of uniformity CU and coefficient of curvature CZ.
A similar phenomenon may affect SPT results, as discussed earlier with respect to fundamental grain size effects. The plots illustrate the expected decrease in the number of particle-particle and particle-platen contacts with increasing particle size, and an associated increase in contact force magnitude.
Plugging was triggered when the ratio of sampler to particle size decreased below a certain value, and was due to efficient mechanisms that tended to decrease the required penetration energy. Example of research paper related to accounting. Soils are assemblages of grains, and are largely classified on the basis of grain size distribution GSD. The Niigata dissertatioon data have been incorrectly plotted as having an age of 30 to 40 years rather nancj the correct value of roughlyyears 1.
The same curve can be used to assess the relative merits of the three approaches dissertatikn energy correction. Chapter 3 describes a proposed alternate approach to energy correction of SPT blow counts based on the hammer kinetic energy. For a b Figure 7.
Close review of Figure 4. In both plots, the penetration resistance or energy of the penetrometer that is not subject to plugging effects i.
Contributing measurement uncertainties were estimated for each of the three methods, and a method based on Taylor series expansion was used to estimate uncertainties of energy corrected blow counts. In North America, hammers are commonly operated using the rope and cathead technique shown nqncy Figure 2.
Circled data points were not used to determine sand trend. Further, the use of LPT blow counts is generally limited to calculation of equivalent SPT blow counts using correlation factors measured in sands. Syolle of business continuity plan. The different hammer types provide different energy, and hence different blow counts.
Nancy stolle dissertation
The potential for systematic variations underlying nacny contributing to the observed variability is discussed for sands and gravels below. The Emax terms cancel in Equation 7. To apply for the Dissertation Awards, please attach the following items in an email to by Dec.