Unsaturated soil evaporating-dehumidifying direct shear apparatus and using method thereof

Abstract

The invention provides an unsaturated soil evaporating-dehumidifying direct shear apparatus and a using method thereof. The unsaturated soil evaporating-dehumidifying direct shear apparatus comprisesa base, as well as a shearing box, a horizontal loading device, a vertical loading device, a matric suction measuring device and an evaporation and dehumidification promoting device arranged on the base, wherein a sample to be tested is placed in the shearing box; the matrix suction measuring device is arranged in the sample to be tested; the vertical loading device is arranged above the shearingbox, and is used for vertically loading the shearing box; the horizontal loading device is connected with the shearing box, and is used for horizontally loading the shearing box; the evaporation and dehumidification promoting device is placed in the shearing box. By adopting the unsaturated soil evaporating-dehumidifying direct shear apparatus, the problem of incapability of simulating the dehumidifying state of a natural soil body in the existing unsaturated soil direct shear apparatus is solved, and the strength parameters of the soil body in an unsaturated soil dehumidifying process can bemeasured accurately.

Description

Technical field [0001] The invention belongs to the technical field of civil engineering instrument testing, and relates to a direct shear instrument for evaporation and dehumidification of unsaturated soil and a use method. Background technique [0002] Unsaturated soil mechanics involves a series of projects, such as the construction and operation of earth dams, natural soil slopes under environmental changes, slope stability of excavated earth, ground uplift caused by expansive soil, and many practical aspects of collapsible soil Problems can be solved only by understanding the seepage, volume deformation and shear strength characteristics of the soil. For saturated soil and dry soil, the shear strength is proportional to the effective stress in the saturated soil. When the soil is in an unsaturated state, the three phases of water, air and soil particles coexist, and its shear strength law will be completely different from saturated or dry conditions. Therefore, studying th...

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Problems solved by technology

[0006] 2. The airtightness of the pressure chamber of the axial translation technology is difficult to guarantee:

[0007] At present, the commonly used direct shear instrument for unsaturated soil seals the shearing system of the entire direct shear instrument with a sealed pressure chamber in order to add air pressure to the soil sample, which not only makes the structure of the direct shear instrument complicated, but also increases the pressure chamber. The problem of air tightness, it is difficult to truly reflect the suction state of natural unsaturated soil

[0008] 3. It is difficult to ensure that the sample is in the natural state of evaporation and dehumidification during the shearing process:

[0010] 4. Long test period and high cost:

However, using a double pressure chamber unsaturated soil triaxial tester to measure the shear strength of unsaturated soil requires a lot of cost to purchase special instruments, and the test period is very long. For actual engineering projects with tight time or limited economic resources, It is very difficult to determine the shear strength parameters of unsaturated soil

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