Strain state calculation method based on full surface deformation of triaxial soil sample

Abstract

The invention discloses a strain state calculation method based on full surface deformation of a triaxial soil sample, belonging to the field of environmental geotechnical calculation. The method includes the following steps: adopting a binocular recognition camera to collect a three-dimensional coordinate of the surface of the triaxial soil sample, calculating three-dimensional deformation valuesof different points on the surface of the triaxial soil sample by comparing the changes of the coordinate before and after deformation, selecting 4 independent points on the surface of the triaxial soil sample and connecting the points to obtain 6 lines, calculating the distances of the 6 lines according to the three-dimensional deformation values of the 4 points, further calculating the direction cosine of the 6 lines and constructing a matrix through a triaxial soil sample coordinate system, and adopting a matrix inversion method and performing matrix multiplication with the distances of the 6 lines to obtain the strain states of full surface deformation of the triaxial soil sample; and repeating the above process, and averaging the obtained multiple strain states of full surface deformation of the triaxial soil sample to obtain the strain state of the triaxial soil sample. The method provided by the invention is simple in operation, mature in test basis and convergent in calculation, can calculate the strain state in the triaxial soil sample, and provides convenience for researches on soil deformation and geotechnical triaxial tests.

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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