The Exploitation And Design Of New Plane Strain Apparatus

Most geotechnical engineering accidents belong to the plane strain problem, such as the collapse of the soil, foundation instability. The plane strain apparatus is a test equipment, which can simulate the stress state of the soil in the practical engineering problems and the destruction of the soil under different stress, and provide the mechanical parameters closer to the actual situation for the engineering design, analysis and numerical calculation. The research and development of the plane strain apparatus started earlier, but it is still not very perfect.The main feature of new type of plane strain apparatus which developed by the paper is the integration control, the researchers just input test parameters and prepare the sample, and the size of the principal stress is controlled by the program, then the test is completed, the new one use flexible square membrane to load the minor principal stress S3, which can restore the change of the sample, and the loading process is more stable, but the consequence is more accurate; the new instrument used the digital image measurement system, which can test and record the changes process every time, and get the stress-strain relationship of the sample. The plane strain test and the triaxial test can share the common load instrument.This issue based on the digital image measurement system uses non-contact measurement, which can record the changes in position e of the sample calibration points on the surface, and calculate the volumetric strain of the sample by back-office software. During the test, the camera will shoot change process of the sample uninterruptedly, we can observe where the shear band of the sample happens, and the formation and development of the shear band, which is great significance to the further study of soil constitutive relation.Combined with the principle of plane strain tests and the functional requirements of the instrument, the author completed the design of loading host, the water pressure controller and pressure chamber in the mechanical design part; then completed the system design of the loading host, and embed the digital image measurement system to the program in the controlling part; and last completed the installation and testing of the instrument and the data analysis in the installation part.