| Triaxial test is a relatively precise test method in laboratory to study mechanics properties of soil at present. Most of the domestic triaxial test apparatus are strain-controlled, which has been well developed and has a measuring accuracy of0.01mm. However, for a triaxial test that requires a high precision, large measurement error may come up when using the strain-controlled triaxial apparatus. With the development of the study on soil mechanics, exigent requirement on higher measuring accuracy in the triaxial test has become more and more important.Measuring principle of the triaxial test and the causes of the measurement error were studied in this thesis and local deformation transducer (LDT) was developed which was sticked on the specimen directly to measure the axial strain in the triaxial test. In this method the measurement error were expected to be eliminated. Then verification were made to find the improvement of the measuring accuracy. The main work of this thesis are as follows:1. The causes of the measurement error of the traditional triaxial apparatus were studied, and the making method of LDT was worked out according to some particular causes.2. A set of LDT was made out by sticking four strain gauge onto a high elasticity phosphor bronze strip, and a Wheatstone bridge was made with the wires of gauges to give and get the signal.3. Tests for the reliability demonstration were made by using an equipment similar to an propeller micrometer. In the tests, the curve of the length of LDT and the deformation data was made out to get the relationship of the axial strain of the specimen and the deformation data.4. The loading cell of triaxial apparatus was remade by drilling suitable size of holes on it to lead the LDT wire out so the signal of LDT can be get.5. Triaxial tests were made while the axial strain of the specimen was measured by both the traditional method and LDT. And a comparison study of the measurement result was made to see the differences. |
