טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentHorany Hanna
SubjectAn Experimental Study to Predict Static Contact Pressure on
a Buried Structure under Static Loads at the
Ground Surface
DepartmentDepartment of Civil and Environmental Engineering
Supervisors Professor Mark Lloyd Talesnick
Professor Avraham Dancygier


Abstract

The present study is the initial stage of a research project aimed to broaden the knowledge concerning soil-structure interaction, and examines the influence of various parameters central to the development of stress on a buried structure. In this stage, the experiments focused on the effects of a uniform static load distributed at the ground surface, on stresses which develop on a model cylindrical steel structure buried in sand.

Most of the effort, resources and time were invested in designing, building and computerizing of the experimental system. The system enabled measurement of soil contact pressure on a buried structure at mid-roof and mid-floor positions, as well as at the pressure vessel base and side boundaries. The system was instrumented with devices to monitor the roof deflection, model tilt, and rigid body displacement. Soil contact pressure was measured using a “Null Soil Pressure Gage”, a new “stress” measurement system that was designed and developed at the Technion, based on the principle of a non-deflecting membrane (Talesnick (2005)).

Upon the completion of the experimental system, two experimental series were performed. The first series examined the functionality of the experimental facility and calibrated its response, by measuring the soil pressures acting on the side and base boundaries. Furthermore, this series examined the influence of a model buried structure on the distribution and magnitude of those pressures. The results illustrated that the stress condition within the central portion of the pressure vessel were uniform in nature, ranging from 95%-90% of the stress applied at the sand surface. 

The second series, which formed the bulk of this study, examined the affect of two parameters on the response of a buried structure, roof thickness and depth.

The results of tests on model structures with a flexible roof illustrated the non-linear development of mid-roof pressure as a function of the pressure applied at the surface and the hysteretic behavior in the unload process.  At applied pressures greater than 40 kPa the stress measured at the roof center becomes smaller than that applied at the ground surface.  In sharp contrast, the model buried structure with the thick (stiff) roof showed linearity in the development of mid roof stress.  The stresses measured were uniformly greater than those applied at the ground surface by a factor of 22%.  Almost no hysteretic behavior was noted upon unloading of the thick roofed structure.