Date of Award
Doctor of Philosophy
Civil, Construction, and Environmental Engineering
Richard L. Handy
Lateral soil pressure is recognized to be an important parameter in soil mechanics theory and in engineering practice, but is equally difficult to measure because it is sensitive to disturbance created by the insertion of a measuring device into the soil. A step-tapered blade has been developed to overcome this hurdle, by measuring horizontal soil pressures using pneumatically operated cell sensors on four thicknesses of blades, and extrapolating the results to zero thickness to obtain the in situ stress in soil;The pneumatic stepped blade was successfully designed and field tested, and is commercially available. A modified version was made to operate electronically. The electric blade used in this dissertation consists of two steps corresponding to the thinnest steps of pneumatic stepped blade. Each step is equipped with two electronic transducers, one to measure the lateral total soil pressure and the other for soil pore water pressure. By connecting the two-stepped blade to a portable data processor, these two pressures can be measured simultaneously and their decays over time can be monitored;The trends in soil pressure with time from the stepped blade data indicate the pressure measurement and de-airing system are properly designed, but not perfected. The main problem that remains to be solved is to effectively and permanently waterproof the stress transducers. Results from comparison between lateral stresses and K[subscript] o values from both pneumatic and electric blade show that data obtained from both stepped blades are equivalent and reproducible, and the data reflect the variations in the known soil profile at the testing site;Based on the pressure dissipation relationships, a tentative method for estimating the rate of soil consolidation is proposed. The method includes a consideration of the aspects of stress-strain relations of soils, the theory related to the design of the stepped blade, the soil response due to the blade insertion, and soil consolidation theory. The theoretical analysis involved in the method is not rigorous, but the distribution of the estimated coefficients of consolidation with soil depth follows the variations of the soil profile. Furthermore, the predicted coefficients of consolidation are shown to be comparable with the results determined from laboratory oedometer tests.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Eric Wai Keung Tse
Tse, Eric Wai Keung, "Application of critical state soil mechanics to Electric K0 Stepped Blade " (1988). Retrospective Theses and Dissertations. 8897.