土压平衡盾构渣土改良泡沫半衰期细观测定方法

为克服泡沫半衰期测定过程中无法施加压力及读数误差等问题,自主研发了泡沫性能测试系统,该系统由泡沫生成模块、压力条件下泡沫衰变细观图像采集模块及泡沫半衰期测定模块等组成,可同时测定压力条件下泡沫衰变过程中的平均半径及溶液析出量半衰期.使用该系统测定了不同试验压力(0、50、100、150、200 kPa)及不同泡沫剂体积...

Mesoscopic Measurement Method of Foam Half-life for Soil Conditioning of Earth Pressure Balance Shield

There are many drawbacks to using the measurement method for foam half-life. For example, only the foam half-life at atmospheric pressure can be measured, and the measurement error of the foam half-life is determined through foam solution precipitation. A foam performance-testing apparatus was developed to solve these problems. The apparatus consisted of a foam generation module, mesoscopic image-capture module of foam decay under pressure (gauge pressure), and measurement module of foam half-life. The apparatus can simultaneously measure the foam half-life of solution precipitation and mean bubble radius during the foam decay process. The evolution of the mean bubble radius and half-life of the foam were measured using the apparatus under different pressures (0, 50, 100, 150, 200 kPa) and foam agent concentrations (2.0%, 2.5%, 3.0%, 3.5%, and 4.0%), and their relationship was established. Subsequently, a mesoscopic measurement method of the foam half-life for the soil conditioning of the earth pressure balance shield was developed. First, images of the foam decay at different times were captured using an observation window and microscope. Second, the equivalent radii of bubbles in the foam decay images were determined using Image J, and the variation in the mean bubble radius ratio was determined. Third, the mean radius ratio at the half-life time under specific pressure and foam agent concentration was calculated using the proposed formula proposed in this study. Fourth, the foam half-life was calculated using the mean radius ratio at the time of half-life obtained in the previous step. In this method, the variation in the equivalent bubble radius during the foam decay process is obtained using microscope-captured images and counting radius software, and the foam half-life is determined. This method prevents errors caused by artificial factors. However, the environmental pressure of the foam decay process can be adjusted using this measurement method to precisely restore the pressure environment of the foam under soil conditions. Finally, the accuracy of the method was verified using experimental data. The results show that the maximum relative error of the foam half-life determined using the proposed method is lower than 5%, and the maximum absolute error is less than 38 s. The accuracy of this method is high.