Design and application of an in-situ test device for the static earth pressure coefficient

In order to conveniently measure the value of the static earth pressure coefficient, a static earth pressure coefficient in-situ test device is designed and fabricated, and the structure and working principle of the device are introduced. The in-situ test is carried out on the site of the Dongqian Lake Depot of Ningbo Rail Transit Line No. 4, and the static earth pressure coefficient K₀ of soil layers of six different depths and the time-history curve of K₀ value at different depths are obtained. The test results are compared with those obtained with the commonly used test methods such as the empirical formula method, flat shovel lateral expansion test method and triaxial test method. The reliability of the in-situ test device for the static earth pressure coefficient and the rationality of the test results are verified. Based on the data obtained from the experiment, the advantages and disadvantages of several test methods are analyzed. The results indicate that the conventional test method will be affected by the difference of soil properties at different depths and the degree of soil disturbance during the sampling process. Finally, by modifying the correlation coefficient of the soft soil layer experience formula in the flat shovel side expansion test in the Shanghai area, the K₀ value calculation formula applicable to the soft soil layer in the Ningbo area is obtained, which is consistent with the experimental data. It is suggested that in other areas localized under the stratum condition, the K₀ value calculation method which is consistent with the data measured by the in-situ test in this area is obtained by modifying the coefficients in the original empirical formulas of each region.