Application of Film-Like Sensors for KO and Pore Water Pressure Measurement in Clay During 1D Consolidation

In this study, the economical FlexiForce sensor, which is thin and flexible, was used to measure K-O and the excess pore water pressure during a 1D consolidation test on kaolinite clay samples. Before the sensor could be used in the measurement, a special waterproof coating was applied, after which sensor calibration was carried out. The coated FlexiForce sensor was incorporated into two types of tailor-made needle probes for the pore water pressure measurement. The experimental results demonstrate that the two types of needle probes can well capture the evolution of the induced excess pore water pressure during consolidation. Upon a loading increment, the measured excess pore water pressure at the middle of the sample continues to increase and reaches a maximum value at t=similar to 4 min and subsequently start to decrease. There is a distinct change in the decreasing trend of the measured excess pore water pressure; the trend becomes mild after t=similar to 480 min, indicating the end of primary consolidation. During secondary compression, the excess pore water pressure continues to decrease due to the continuous settlement. A constant K-O value, which is comparable to the prediction by Jaky's equation, is measured by the sensors in the loading path; during secondary compression, K-O increases with time.