基于缩尺级配的土压力盒标定

Calibration Test of Earth Pressure Cell Based on Grade Scale of Field Soil

土压力盒生产厂家给出的土压力盒的工作参数不适用于土压力盒的实际工作情况,故在土压力盒使用前要进行标定,得到与实际工作环境相似情况下的土压力盒的工作参数。为了模拟实际工作环境,采用混合法对现场土料进行级配缩尺得到试验土样;改变土样回填密度,测定土压力盒在加卸载循环下的输出,绘制土压力盒的标定曲线。结果表明:土标曲线存在明显的滞回圈,与液标曲线基本稳定不同,但加载部分接近直线;随着回填土样密实度的增加,土压力盒的测量精度有所提高;为尽可能消除土压力盒的测量误差,需通过干密度试验确定合理的回填密度。

The sensitivity of Earth Pressure Cell （EPC） provided by cell＇s manufacturer does not apply to the actual working condition of EPC, so the EPC should be calibrated before utilization to conclude the working parameters under the circumstance similar to actual working environment. In order to simulate actual working environment, the test samples are obtained by equal replacement scale of field soil. The calibration curves of EPC are drawn based on the output of EPC in the loading and unloading cycle by changing the soil backfill density. The results show that, （a） there is an obvious hysteresis loop in sand calibration curve, with loading part closing to a straight line and nevertheless the liquid calibration curve remaining basically stable; （b） the measuring accuracy of EPC will be improved with the increase of density of backfill soil; and （e） to eliminate measurement error of EPC as far as possible, the dry density test is necessary to determine the reasonable density of backfill soil and the exponential function is recommended to describe the relationship between EPC output and pressure.