The method of the test of pile-soil stress ratio of the composite ground under Geotechnical Grille in field

The parameter of diaphragm type earth pressure cells (EPC) is usually determined from calibration test by applying a known fluid pressure to the EPC and recoding the output, it cannot be used when the normal stress in soil was measured by EPC. According to the stress distribution on the pile top and the earth face between piles within the composite ground under Geotechnical Grille, calibration tests of EPC were conducted under the condition which can reflect stress distribution features on piles top and earth face between piles, and the simulation calibration factors were obtained which can be used to calculate the stress of piles top and earth face between piles directly. The simulation calibration test indicated that the factor from the simulation calibration test of the piles was less than the factor from the fluid calibration test, and the curve from the simulation calibration test of the pile was a parabola, and the amount of measurement result from the fluid calibration factor was 1.36~2.4 times to the simulation calibration factor. It also indicated that the factor from simulation calibration test of the earth face between piles closed to the fluid calibration factor, and the simulation calibration curve close to line. The example of engineering showed that the pile-soil stress ratio is relatively small if all use the uniform calibration factors, Calculation results of the pile-soil stress ratio of composite ground under flexible foundation was 1.7~2.9 if used the simulation calibration factors of pile and the earth face between the piles respectively.