A true triaxial instrument and test method for unsaturated soil collapsibility that can measure matrix suction

Abstract

The invention discloses a true triaxial instrument for unsaturated soil collapsibility capable of measuring the suction force of a matrix and a test method, comprising a mainframe support fixed on a mainframe base, an axial adjustment piston installed on the mainframe base, and an upper surface of the axial adjustment piston. An axial hydraulic cylinder is installed, an axial pressure piston is arranged in the axial hydraulic cylinder, a pressure chamber is fixed on the upper surface of the axial pressure piston, a sample cavity is opened inside the pressure chamber, and a sample cavity is arranged inside the pressure chamber base, which is respectively connected to the sample. The lower water inlet pipe and the lower drain pipe are connected to the cavity, the upper immersion pipe and the upper air inlet pipe are arranged on the sample cap, the upper immersion pipe is connected with the GDS pressure / volume controller, and four cavities are arranged in the side wall of the pressure chamber, each of which is A flexible hydraulic bag is arranged in the cavity, and each flexible hydraulic bag is connected with a stepper motor drive controller through a lateral pressure switch valve. The invention has a thinner structure, is easy to operate, and can realize the true triaxial collapse test of unsaturated soil under the conditions of controlling and measuring the suction.

Description

technical field [0001] The invention belongs to the technical field of geotechnical engineering testing equipment, and in particular relates to a true triaxial instrument for unsaturated soil collapsibility capable of measuring matrix suction and a test method. Background technique [0002] Loess is a typical unsaturated soil, and its microstructural characteristics determine that it has different degrees of collapsibility. When the collapsible loess is soaked in water under a certain pressure, the suction force is lost and the strength is reduced, which will cause significant additional subsidence, or after the collapsible loess is soaked in water, the suction force is lost, and the loading will be much larger than that under low humidity conditions. high compressibility. The collapsible deformation of loess has abruptness, discontinuity and irreversibility, which is extremely harmful to engineering. In the past laboratory tests, instruments such as consolidation instrume...

AI Technical Summary

Problems solved by technology

[0003] The invention patent CN 03226081 A published by Xi'an University of Technology in 2013 uses a true triaxial instrument to install four lateral displacement sensors on the side wall of the pressure chamber to measure the deformation in the direction of the medium principal stress and the direction of the small principal stress, but the side wall of the pressure chamber The space occupied by the four lateral displacement sensors installed is too large, which not only affects the test sample loading and test operation, but also is inconvenient when installing the side wall of the pressure chamber, which is easy to cause disturbance to the lateral displacement sensors. The middle part of the bladder is in contact. The measured data may only be the deformation of the middle part of the hydraulic bladder. The error of the test data is relatively large, and the true triaxial instrument cannot be used for immersion operation, and it cannot simulate the real force immersion conditions of the undisturbed loess, nor can it meet the needs of use.

Images