Abstract:

Several negative factors like soil arching effects，redistribution of stress，dispersion of stress and so on are easily arise on the force surface during the rigid loading calibrations of earth pressure cells in sand soil due to the larger difference in the physical and mechanical properties between earth pressure cells’ material and sand soil，which result in the poor application of rigid loading method in the calibration tests.To solve above problems，the author designed a new pressure cells calibration method—Stress concentration method based on the consideration of ??reducing the loading area and the space of the sand soil.The author made calibration tests in sand soil for three different sale earth pressure cells by using two different methods：The rigid loading and stress concentration method，and draw calibration curves of methods A，B and gas pressure calibration based on the results of two above methods and the manufacturer’s gas calibration results.In order to judge the advantages and disadvantages of the three calibration methods，the author compared the goodness of fit，calibration parameter and dispersion rate of data of the results of two methods and the gas calibration.The result shows that the linear correlation coefficients of stress concentration method’s calibration curves are all greater than 0.99，which means the calibration curves obtained by the new test method all have a low dispersion rate，so the its calibration results meet the accuracy requirements of the indoor test and have field application value.But the calibration coefficients of two sand pressure calibration method are significantly different from the gas pressure calibration method，which proves the existing of the soil arching during the earth cells working in the sand soil and the necessary to make a sand pressure calibration test.It is found that the calibration parameter of the rigid loading test is smaller than that of the gas standard but the calibration parameter of the stress concentration method is larger，which indicates that people can reduce the effect of soil arching and lateral stress on the sensor by reducing the soil space and the earth cell’s force area，so that make the stress on sensor surface more concentrated to avoid uneven distribution of stress.At last of the thesis，according to conclusions of test and analysis，the authors advice to use the stress concentration method as calibration tests of vibrating wire earth pressure cells in a soft sand environment with a large particle porosity.

Key words: vibrating wire earth pressure cells, soil arching, fluid pressure calibration method, sand pressure calibration method, linear fitting, calibration parameter