Digital image measuring method and equipment of triaxle testing sample soil deformation

Abstract

The present invention relates to a digital image measurement method for triaxial test soil sample deformation and its equipment, and relates to the application of computer digital image identification technique in conventional triaxial test sample deformation measurement, consisting of triaxial compression apparatus, digital image collecting equipment and microcomputer, and its program possesses two portions: calibration of pixel equivalent and triaxial test sample deformation measurement, every portion is comprised of two large modules of image collecting and processing and edge identification and recording. It adopts non-contact direct measurement, and can raise measurement accuracy, can synchronously measure radical deformation and axial deformation of sample, so that it possesses extensive application.

Description

1. Technical field: [0001] The invention relates to the application of computer digital image recognition technology in the deformation measurement of conventional geotechnical triaxial test specimens. 2. Background technology: [0002] At present, the main steps of the conventional triaxial test method are as follows: (1) Cut the soil into cylinders and put them in a rubber membrane or directly put soil in the rubber membrane to form a sample, and put it in a sealed pressure chamber. The lower end of the rubber membrane is bound on the base, and the upper end is bound on the test cap, so that the pore water in the sample is completely separated from the water in the pressure chamber. Pore ​​water is communicated with the pore water pressure measurement system through the permeable stone at the lower end of the sample, or communicated with the drainage pipe through the permeable stone at the upper end. (2) Apply pressure to the pressure chamber so that the specimen is subje...

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Problems solved by technology

However, due to the influence of the rigid sample cap, the radial deformation of the soil sample is extremely uneven during the test, so the average radial deformation cannot accurately reflect the radial strain state of the soil sample.

In addition, conventional geotechnical triaxial instruments also have the following defects in deformation measurement: (1) they cannot take into account the process of soil sample formation and saturation on the triaxial instrument (installing pressure chambers, increasing confining pressure to release suction, and passing carbon dioxide Volume Deformation of Soil Samples in Gas and Water Injection Saturation)

(2) The volume measurement error caused by the displacement change caused by the rubber film embedded in the surface pores of the soil sample cannot be eliminated in the measurement

(3) The influence of soil sample end constraints on soil sample deformation cannot be considered

(4) In order to measure the radial deformation, the soil sample must be completely saturated, which is not only time-consuming, but also often difficult to achieve

(5) For unsaturated soil, because the volume deformation of the soil sample cannot be determined by measuring the displacement, it cannot be directly used in the test of unsaturated soil

For example, the local displacement sensor LDT and the radial strain gauge have high precision, but it is difficult to adapt to large deformation, and it is difficult to operate when measuring in water in a sealed chamber; the problem with the Kaman Multi-Vriel sensor is that there is static drift, and it is difficult to control the measurement Accuracy; use a microscopic microscope to record the distance between the tape-shaped aluminum foil marks wrapped around the sample, the test process is very complicated

Using a double-layer pressure chamber, the stress-strain characteristics of unsaturated soil can be tested on a conventional triaxial instrument, but the test is still the average volume change of the soil sample, and the modification of the test instrument, test control and operation are relatively complicated

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