水囊土压力计研制与试验验证研究

Development and Experimental Validation of Water Bladder Earth Pressure Gauge

针对土压力盒易发生应力集中的问题,研制了水囊土压力计,即通过透明的PU空压软管将感压水囊与电子压力表进行连接,其中感压水囊的厚度可控制在5~10 mm,在使用时电子压力表的高度位置进行固定。将水囊土压力计与振弦式土压力盒埋设在不同压缩模量的土体中进行了对比试验,结果分析表明,由于感压水囊比土压力盒薄,虽然实测土压力偏大问题不可避免,但相对土压力盒测试结果而言,采用水囊土压力计测试地层中的土压力时应力集中问题显著改善;从测试结果可知,由测试元件厚度所导致的土压力偏大幅值为非线性,这与测试元件周围的土体颗粒变形调整有关。将水囊土压力计用于盾构隧道响应模型试验研究中,从测试结果可知,水囊土压力计与土压力盒的测试结果具有明显的不同;从测试结果的变化趋势分析来看,水囊土压力计的测试结果可信,且有必要采用水囊土压力计直接贴在模型盾构隧道外壁测试其周围土压力。水囊土压力计的测试原理简单,且成本低、精度高,因其为柔性构造,可根据测试需求选用感压水囊用于结构物表面为非平面的土压力测试。

Based on the problem of earth pressure concentration in earth pressure cells,a water bladder earth pressure gauge was invented.The thickness of pressure sensing water bladder can be controlled within 5~10 mm.The pressure sensing water bladder is connected with the electronic pressure gauge through the transparent PU air pressure hose.The height position of the electronic pressure gauge needs to be fixed when the water bladder earth pressure gauge is used.A comparison test was conducted between the water bladder earth pressure gauge and the vibrating string earth pressure cell buried in soils with different compression modulus.The analysis of the results shows that,although the problem of high measured earth pressure is unavoidable,the stress concentration problem is significantly improved when the earth pressure in the stratum is tested with the water bladder earth pressure gauge compared with the earth pressure cell as the pressure sensing water bladder being thinner than the earth pressure cell.From the test results,it can be seen that the amplitude of soil pressure caused by the thickness of the test element is non-linear,which is related to the adjustment of soil particle deformation around the test element.The water bladder earth pressure gauge is used in the model test of shield tunnel response.The test results show that the water bladder earth pressure gauge is obviously different from the earth pressure cell.From the analysis of the changing trend of the test results,the test results of the water bladder earth pressure gauge are reliable and it is necessary to use a water bladder earth pressure gauge directly attached to the outer wall of the model shield tunnel to test its surrounding soil pressure.The test principle of the water bladder earth pressure gauge is simple with low cost,and the precision is high.Because of its flexible construction,the pressure sensing water bladder can be used to test the earth pressure of non-plane structure surface according to the test demand.