Study On Testing Technology Of Three-dimensional Stress In Soil

So far there is no perfect three directional soil pressure sensor to obtain the stress state, which has important theoretical significance and practical value. Therefore, a new design principle of soil stress state sensor was proposed in the dissertation, and the sensor was successfully trial-produced. Feasibility and reliability of sensor has been tested and verified by physical simulation test and numerical calculation. The study is significant to development and application of soil stress state sensor.i. In order to test the three direction stress of soil mass, a new design principle of soil stress state sensor was put forwarded and the formal parameters of the sensor were designed preliminary based on the theory of stress-strain state. Through the analysis of coefficient matrix, we found that it is reasonable to arrange 7 strain sensitive elements in sensor substrate whose elastic modulus should be 63 times of measurement range.ii. According to the needs of design as well as a series of survey and test work, we finally chose the Fiber Bragg Grating(FBG) and the epoxy resin(YH-9002) as the sensitivity component and the substrate material.iii. The validity of the design theory and the material parameters was verified by numerical simulation analysis, whose three dimensional model was established by ANSYS software. The parameters of numerical simulation was on the basis of properties of the chosen materials.iv. One dimensional sensor and soil stress state sensor was trial-produced and was tested in hydrostatic pressure and sand media respectively. The linear degree of sensor response is over 98% and the repeatability error is below 9%. In sand experiment, the test results of trial-produced sensor is 1.84 times(mean value) of that of earth pressure cell, the deviation is caused by the interference of the sensor protection. It shown that the soil stress state sensor is of feasibility.The research shown that the soil stress state sensor can obtain the stress state of soil to calculate the three directional stress of soil. It need to be constantly improved and has good use prospect.