Quantification of Arching in Cohesionless Soils due to Diaphragm-Type Pressure Cells: A Numerical Investigation

Diaphragm-based earth pressure cells (EPCs) are commonly used to measure earth pressure within the soil or on a structural boundary. The EPCs measure the pressure indirectly by determining the change in the magnitude of diaphragm deflection. However, the diaphragm deflection alters the stress state in the soil due to arching, causing discrepancies between the measured and the actual pressures. Pressure measurements using EPCs are influenced by multiple factors, making it challenging to quantify the effects of arching separately through laboratory tests. Hence, the present study utilizes numerical modeling to investigate and quantify arching for boundary-type diaphragm EPCs with different cohesionless materials. The diaphragm is modeled as a thin plate element. A nondestructive methodology is proposed to determine the diaphragm thickness indirectly by performing simple laboratory tests and using the thin plate theory. Arching is quantified by calculating the change in vertical pressure with and without using EPCs. The results indicate that the arching magnitude increases with an increase in sand stiffness, while the EPC–sand interface effect is insignificant for a given EPC. The trapdoor experiment is commonly used to quantify arching; therefore, the numerical results are validated against existing literature on trapdoor experiments. For the EPCs and sands considered in the present study, the EPC can record pressure 10%–25% less than the actual pressure due to arching. Design charts are given to determine the arching magnitude from EPC and sand properties.