Full-automatic direct shear apparatus for densely-compacted bentonite unsaturated shear property study

Abstract

The invention belongs to the technical field of the civil engineering (rock-soil) and geological engineering, and discloses a full-automatic direct shear apparatus for densely compacted bentonite unsaturated shear property study. The apparatus mainly comprises a shear system, a normal pressure loading system, a measurement system, an automatic control and data collection system, a gas-phase methodsuction control system; the shear system realizes a shear rate or continuous loading and unloading of shear force by adopting a servo motor; the normal pressure loading system adopts realize the continuous loading and unloading of normal stress by adopting an air compressor and a rolling diaphragm cylinder; the measurement system measures normal displacement, shear displacement and the shear force by adopting a high-precision sensor; the automatic control and data collection system automatically controls test process, data collection and display through computer software; and the gas phase method suction control system controls environment humidity in a shear box seal housing through a saturated salt solution and a combined seal housing. The automatic test on the densely compacted bentonite unsaturated shear property is realized.

Description

technical field [0001] The invention relates to a full-automatic direct shear instrument for researching the unsaturated shear properties of high-compaction bentonite, belonging to the technical fields of civil engineering (rock and soil) and geological engineering. Background technique [0002] High-level radioactive waste (referred to as "high-level radioactive waste") has the characteristics of strong radioactivity, long half-life, and high toxicity. At present, it is internationally recognized that the deep geological disposal method is used to seal it in the formation of 500-1000m underground. In the concept of deep geological repositories, buffer backfill materials should have key functions such as maintaining the stability of engineering structures, preventing groundwater seepage, and retarding nuclide migration. After comparison and selection of various clay minerals, bentonite-based materials are preferred by various countries as buffer and backfill materials for d...

AI Technical Summary

Problems solved by technology

However, the cohesion of high-compacted bentonite can be as high as about 2 MPa in the unsaturated state, and its shear strength parameters cannot be measured under low normal pressure conditions

In addition, high-compacted bentonite samples are very sensitive to ambient humidity, and existing direct shear instruments cannot meet the requirements of unsaturated shear tests

For the shear properties of compacted bentonite, the existing research work mainly uses strain-controlled direct shear instrument to conduct experimental research on the saturated shear strength of compacted bentonite with low dry density; while for high dry density, unsaturated shear strength , unsaturated shear creep properties are rarely reported

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