A Calculation Method of Strain State Based on Total Surface Deformation of Triaxial Soil Samples

Abstract

The invention relates to a strain state calculation method based on the deformation of the whole surface of a triaxial soil sample, which belongs to the field of environmental geotechnical calculation. A binocular recognition camera is used to collect the three-axis coordinates of the surface of the triaxial soil sample, and the three-dimensional deformation values ​​of different points on the surface of the triaxial soil sample are calculated by comparing the changes in coordinates before and after deformation. Four independent points on the surface of the triaxial soil sample are selected and connected to each other. 6 lines can be obtained, and the distances of the 6 lines are calculated through the three-dimensional deformation values ​​of the 4 points, and then the direction cosines of the 6 lines are calculated through the three-axis soil sample coordinate system and a matrix is ​​constructed. method and perform matrix product with the distances of the six lines to obtain the strain state of the whole surface deformation of the triaxial soil sample. The strain state of the triaxial soil sample is obtained by repeating the above process and averaging the obtained strain states of the whole surface deformation of a plurality of triaxial soil samples. The method of the invention is simple, the test foundation is mature, the calculation is convergent, the strain state in the triaxial soil sample can be calculated, and the invention provides convenience for soil deformation and geotechnical triaxial test research.

Description

technical field [0001] The invention belongs to the field of environmental geotechnical calculations, and relates to a strain state calculation method based on the deformation of the whole surface of a triaxial soil sample, which can be used to evaluate the strain state of a unit soil sample. Background technique [0002] The stress-strain characteristics of the soil are important criteria to measure the strength and deformation characteristics of the soil. Under the conventional triaxial environment, only the deformation in two directions under the action of confining pressure and axial pressure can be obtained, that is, the axial deformation and radial deformation of the triaxial soil sample. To deformation. True triaxial can realize the deformation in three directions under the joint loading of axial pressure, lateral pressure and confining pressure, that is, one axial deformation and two lateral deformations. Patent CN1145897C provides a method for measuring the surface...

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Problems solved by technology

Patent CN1145897C provides a method for measuring the surface deformation of triaxial soil samples. This device can only realize the deformation measurement of soil samples in two directions, which is also the axial deformation and radial deformation of soil samples.

There is no device capable of calculating the full strain state (3 normal strains, 3 shear strains) in the field of triaxial testing

[0003] Conventional triaxial equipment can measure certain deformations of soil samples by providing a loading force in a certain direction. The function of the loading system is complete, that is, it can imitate the loading form of the on-site geotechnical structure, but the function of the deformation test is incomplete, that is, Full strain state (3 normal strains, 3 shear strains) cannot be obtained

Patent ZL201410740140.2 provides a three-dimensional strain testing device, which needs to arrange strain rosettes on the bar to realize the measurement and calculation of three-dimensional strain. This method is suitable for model tests of a certain volume; The rigidity requirements of the parts, and the diameter of the triaxial sample of fine-grained soil is generally less than 100mm, this device is not suitable for the geotechnical triaxial test environment

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