UBC Theses and Dissertations
Interpretation of selfboring pressuremeter tests in sand Cunha, Renato Pinto da
This thesis addresses the analytical interpretation of selfboring pressuremeter testing curves in sands. Emphasis is placed on the development of a new approach to analyze the data and hence to derive reliable predictions of the basic soil parameters, namely the friction angle, the lateral stress and the shear modulus. The new methodology of interpretation relies on a “curve fitting” technique to match the experimental and idealized (model) curves, from which a set of fundamental soil parameters are derived. These parameters are linked to each other in the framework of the cavity expansion model adopted. Some of the elasto-plastic models currently available are adopted for use under the new methodology of interpretation. A new model that extends the rheological equations of Hughes et al, 1977 is also developed. Pressuremeter tests under controlled conditions are analyzed in order to verify the basic assumptions of the chosen models. Some of the best calibration chamber data from the University of Cambridge (Fahey, 1986) and from the Italian ENEL-CRIS laboratory (Bellotti et a!, 1987) are used for this purpose. Once the reliability of the chosen models is established, the new methodology of interpretation is applied to field pressuremeter data. Several high quality tests carried out by the writer in a granular site in Vancouver, Canada are analyzed. The results of both field and chamber tests confirm the reliability of the new interpretation approach proposed here. The new interpretation approach also provides the engineer with a technique to numerically quantify the disturbance of the testing curve. Using the new disturbance criterion ranges for “undisturbed”, “disturbed” and “highly disturbed” testing curves are proposed. This criterion aided in the establishment of the insertion procedure of the UBC selfboring pressuremeter, allowing optimization of the insertion technique and minimization of soil disturbance during selfboring. It is believed that the contribution given in this thesis aids pressuremeter practitioners to design more economical engineering works based on reliable soil parameters derived from the selfboring pressuremeter test. Simplicity and reliability are the essential features of the proposed methodologies of insertion, testing and interpretation described herein.
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