Improvement And Study Of Stress-strain Test Instruments In Soil Mechanics And Geotechnical Engineering

Measuring the stress and strain during the entire test plays a significant role in the study of soil constitutive models in soil mechanics. It needs to broaden the stress scope and to improve the strain accuracy of the existing geotechnical testing apparatuses, in order to build the soil constitutive model based on the more accurate test data.In this paper, the mechanical structure of sensors in series is introduced. The structure is made of the small-scale and the large-scale sensors in series, and the small-scale sensor is placed inside the triaxial pressure chamber, in order to eliminating the interference of the frictional force between the loading lever and the pressure chamber, which keeps a high precision on the whole range. The structure can achieve the overload protection for the small-scale sensors.In this paper, the traditional plane strain pressure chamber has been improved, which used a new panel with water film, in order to reduce the σ2 direction friction. The applications of the new and the old plane strain apparatuses for testing on standard sand are introduced. Typical results are presented that the peak of the stress-strain curves obtained by the new developed plane strain apparatus can be reduced by 60%, which reduce the σ2 direction friction significantly.In order to improve the accuracy of small stress, the calibration with non-weights of the under-water pressure sensor is presented, which studies the effects of confining pressure. In order to meet the requirements of the precision strain measurement, the Stress-strain test geotechnical facilities use the non-contact digital image measurement system, and add the high precision digital image control platform, that enables to improve the accuracy of the strain test. Digital image measurement system can detect the volume change of the sample, and observe the location, formation and development process of the soil shear band, which makes a big significance on the study of soil constitutive models. Test results made by the stress-strain test geotechnical facility are presented in this paper, and the results are analyzed.