Symmetrical layered sample pressing device and sample preparation method for triaxial test sample preparation

Abstract

A symmetrical layered sample pressing device and sample preparation method for triaxial test sample preparation. The main components of the device are: the outer walls at both ends of the soil sample cylinder are fitted with the slots on the inner wall of the extension tube, and the non-slot parts of the extension tube are The diameter of the inner wall is equal to the diameter of the inner wall of the soil sample cylinder; the extension cylinder and the soil sample cylinder are covered with a pad set, and the pad set is composed of: the outer circumference of the back end of the outer pad protrudes outward to form a cover edge, and the front center of the outer pad There are threaded protrusions; there is a threaded hole in the center of the back of the middle block, there are threaded protrusions in the center of the front, and there are two middle blocks; there are threaded holes on the back of the inner block, and the front is flat; the outer block, the middle The pads and inner pads are screwed to the corresponding threaded holes through protrusions; the height of the inner pads and middle pads is 1 / 5 of the height of the soil sample cylinder; the sum of the heights of the inner pads and the outer pads minus the cover The thickness along the extension tube is equal to the height of the non-card slot part of the extension cylinder. The sample prepared by the device has good uniformity, and can make the test result of the triaxial test more accurate and reliable.

Description

technical field [0001] The invention relates to a symmetrical layered sample pressing device and a sample preparation method for preparing a triaxial test sample. Background technique [0002] The samples used in the triaxial test in geotechnical (civil engineering) tests are divided into two types: undisturbed soil samples and disturbed soil samples. The preparation of disturbed soil samples mainly includes the procedures of selecting soil samples, air-drying (or oven-drying), crushing, sieving, soil blending, and sample preparation. Among them, sample preparation is a very critical step. At this stage, there are mainly double-sided sample pressing method and layered compaction method. [0003] Double-sided sample pressing method: pour all the soil samples required for sample preparation into the sample preparation cylinder, measure the height of the sample when the indenter contacts the soil sample, calculate the difference with the final required sample height, and contr...

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Problems solved by technology

As a result, the density of the sample gradually decreases from bottom to top, and the difference between the upper and lower ends is the largest, resulting in uneven density of the sample. Since the two ends of the sample are the direct force-bearing surfaces during the triaxial test, this unevenness Sexuality will seriously interfere with the stress state of the sample, resulting in a large deviation of the test data

[0006] 2. During the sample preparation process, it is necessary to judge whether the compaction of each layer of soil samples has reached the required height by observing the scale of the ruler. The thickness of each layer of soil samples after compaction will be affected by large human factors and errors will also occur

[0007] 3. During the sample preparation process, the compaction of each layer of soil samples is manually operated, it is difficult to ensure that the hammer guide rod remains vertical during the compaction process, and it is easy to cause the surface of each layer of soil samples to be uneven

At the same time, according to the requirements of the specification, when the surface of the last layer of soil sample (sample end face) is not level, the end face of the sample needs to be leveled, but the leveling process is difficult and time-consuming, which will greatly reduce the efficiency

And the leveling operation will also cause a large disturbance to the sample, reducing the uniformity of the end surface of the sample

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