INTERNATIONAL SYMPOSIUM ON Bali, Indonesia, June 1 ST – 6 TH , 2014 Laboratory and Numerical Study on Design Parameters jdjjsgshjhfsdkjhskslsl;s;s;;s;;s;;sjsjkjffffrtttttttfggjfgjgkfkjkjf fffffjfjjfkkfjjj of Earth Pressure Cell A. Noorzad Faculty of Water and Environmental Engineering, Shahid Beheshti University & Chairman, Iranian Committee on Large Dams (IRCOLD), Tehran, Iran ircold@neda.net , a_nourzad@sbu.ac.ir K. Ahangari Department of Mining Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran Head of Committee on dam surveillance, Iranian Committee on Large Dams (IRCOLD), Tehran, Iran ` M. Golestanifar Department of Mining Engineering, Science and Research branch, Islamic Azad University, Tehran, Iran. ABSTRACT Measuring total stress changes in soil mass is of great importance in large geotechnical projects such as dams. The measured pressure might contain serious errors coming from the differences between the stiffness of the pressure cell and its surrounding media. In the present research, design parameters of pressure cells such as dimension and shape have been studied by using laboratory tests and finite element modeling. The results indicate that with increasing the diameter and decreasing the thickness of pressure cell, the difference between measured and applied pressures will be fade out. The obtained results confirm that the influence of thickness on the cell is greater than diameter. Finally, simultaneous effects of these factors on the cell error were investigated by using of response surface modeling. An equation is developed in order to correct the results of pressure cells. Based on the proposed model a practical simple graph is presented to compute the optimum correction factor leading to actual applied pressure. Keywords: Soil; Finite element modeling; Design parameters; Response surface methodology 1. INTRODUCTION Stress is one of the most important factors of soil mass in geotechnical engineering. Pressure cells can be used in order to determine the distribution, intensity and direction of stress within soil mass, foundation and retaining walls. Since the results of pressure cell play an effective role in evaluation of structures, precision in performance of this instrument is very important. Thus, several investigations were carried out to modify its performance. Differences between actual levels of stress and pressure cell results have been reported during these studies. Searching the causes of these errors and methods of correcting them have always been an interest topic for researchers. The studies of Selig (1964), Hvorsiew (1976), Kullhawy and Weiler (1978, 1982) about effective factors on measuring soil mass pressure by using pressure cell could be mentioned (Selig 1964, Hvorslev 1976, Weiler and Kulhawy 1978, 1982). Furthermore, Dunicliff and Green II - 174