Bidirectional press-in type triaxial sample preparation device and method based on soil stress history

Abstract

The invention discloses a bidirectional press-in type triaxial sample preparation device and method based on soil stress history. The counter-force top plate is located over the base, fixedly connected with the base through a plurality of fixing rods and connected with the base through a plurality of fixing rods, the base and the counter-force top plate are provided with matched base plates, a lower base plate is arranged in the center of the top face of the base, and the top face of the lower base plate is in rigid connection with the bottom face of the lower lifting head. An upper base plate is arranged in the center of the bottom surface of the counter-force top plate, the lower surface of the upper base plate is rigidly connected with the upper lifting head, and a hydraulic system and a sample preparation mold are mounted between the lower base plate and the upper base plate. Uniformity of the soil sample and flatness of the upper surface and the lower surface are guaranteed, compactness of the soil sample is controlled, vertical stress and stress history borne by the soil sample in a foundation are simulated, the problem that three-axis soil sample demolding is prone to failure is solved, and the device is simple in structure, convenient to operate and high in accuracy and success rate.

Description

technical field [0001] The invention belongs to a soil sample preparation device and method in the technical field of civil engineering tests, and in particular relates to a bidirectional press-in type triaxial soil sample preparation device and method based on soil stress history. Background technique [0002] As a very important test method in the field of geotechnical engineering, conventional triaxial test can effectively measure the mechanical properties of soil. For triaxial tests on disturbed soils, the quality of soil sample preparation plays a decisive role in the test accuracy and data reliability. The soil sample for the triaxial compression test needs to be made into a cylinder standard soil sample with a diameter of 3.91 cm and a height of about 8.0 cm. The soil samples obtained by different preparation methods have different problems. Referring to the requirements of the test regulations for the sample preparation of disturbed soil, the methods mainly include ...

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Problems solved by technology

Although the traditional method is simple in equipment and easy to use, there are many problems in sample preparation: 1) It is difficult to accurately control the density of the soil sample, the uniformity is not high, and the phenomenon of "close at the top and loose at the bottom" appears; The effect affects the structure of the soil sample, and it is difficult to ensure the absolute verticality of the hammer, resulting in an artificially manufactured inclined layer, and the relative displacement of the membrane plate; 3) It is impossible to control the impact on the upper and lower ends of the soil sample during sample preparation Back pressure and confining pressure make it difficult to simulate the real stress path of the soil sample; 4) For non-cohesive soils such as sandy soil and silt soil, the soil sample “falls off the bottom” after the preparation is completed or is easy to scatter after forming; 5) Due to Unsaturated cohesive soil has matrix suction and cohesion, especially after adding tung oil, glutinous rice pulp and other soil sample improvement materials, the moisture content, void ratio, etc. of the remodeled soil have been changed. It is easy to cause the demoulding failure of the soil sample; considering the direct extrusion method will cause a large stress difference at both ends and destroy the uniformity of the soil sample, and the friction formed by the side wall will drag and damage the side of the sample

Due to the many problems mentioned above in the traditional triaxial soil sample preparation method, the success rate of sample preparation is low, which seriously affects the smooth progress of the triaxial test and is not conducive to the study of the mechanical properties of remolded soil.

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