活动门试验中土压力盒标定方法

Calibration Method of Earth Pressure Cell in Trapdoor Test

为确保活动门试验结果的准确性,根据试验填土深度的不同,对一批相同型号的电阻式土压力盒进行了垂直方向上的分级加载和卸载标定,并考虑标定装置内壁摩擦力影响,修正了作用在土压力盒上的有效加载和卸载应力。通过对加卸载过程进行离散元模拟,证明有效加载和卸应力修正方法较为合理。标定试验结果表明,加载过程中微应变量-有效应力曲线呈线性变化,可使用线性函数拟合;卸载过程中微应变量-有效应力曲线存在明显的滞后现象,且滞后程度随有效加载应力的增大而增大,可使用单指数曲线拟合。标定土压力盒后,开展了填土试验,结果表明土压力盒不宜在压力过小或填土深度过小时使用。

To ensure the soil pressure accuracy of trapdoor tests,according to different depths of the soil,a series of calibration experiments with different levels was conducted by using resistance strain-type soil pressure cells.The calibration included loading calibration and unloading calibration.Additionally,a modification was derived to the applied stress(i.e.,effective stress)by considering the influence of boundary friction force.Through discrete element simulation(DEM),it is proved that the modification of applied loading stress is appropriate.The calibration test results reveal that the macrostrain-effective stress curve of loading progress exhibits linear variation and can be well-fitted by a linear function.The macrostrain-effective stress curve of unloading progress exhibits an evident hysteresis phenomenon.With increasing loading pressure,the hysteresis phenomenon becomes more significant.And it can be fitted by using a single exponential curve.After calibration,the filling validation were conducted.Results indicate that the soil pressure cell should not be used under low stress or shallow fill depths.