Preparation device and method for cohesionless soil sample for geotechnical test

Abstract

The invention discloses a preparation device and method for a cohesionless soil sample for a geotechnical test. The device comprises a sample loading part, a sample compacting part, a sample pre-saturation part and a vacuumizing part, wherein the sample loading part comprises a first split mold, a second split mold, a bottom lantern ring, a top lantern ring, two annular hoops, two rubber rings anda rubber film. The rubber film is flatly attached to inner walls of the first split mold and the second split mold with a vacuumizing method, defects on side surfaces of the sample are reduced, and uniformity and flatness of the side surfaces of the sample are guaranteed; bottom stability of the sample loading part is improved by the bottom lantern ring, and the top lantern ring helps to reduce soil mass loss and pollution to geotechnical test equipment in the preparation process of the top sample; the pre-saturation part and the vacuumizing part are universal, and the preparation device andmethod can be applied to cohesionless soil sample preparation of different precision geotechnical tests after sizes of the sample loading part and the sample compacting part are adjusted according tothe size of the geotechnical test equipment and the size of the sample.

Description

technical field [0001] The invention relates to the technical field of indoor geotechnical tests of geotechnical engineering, in particular to a device for preparing cohesive-free soil samples for geotechnical tests and a preparation method thereof. Background technique [0002] Indoor geotechnical testing is one of the main ways to reveal various physical and mechanical properties of soil, and it can provide a scientific basis for the determination of soil parameters in the process of engineering design, theory or numerical calculation. [0003] Indoor geotechnical tests are carried out based on suitable soil unit samples. The undisturbed soil can be directly obtained by cutting the samples after in-situ sampling. However, in-situ samples are often encountered in actual engineering practice and research projects. In the case of large sampling disturbance, difficult sampling, or limited number of original samples, difficult to transport and store, etc., remolded soil is usua...

AI Technical Summary

Problems solved by technology

However, cohesionless soil (such as sand) has almost no cohesive force, and the soil has the characteristics of loose grains. If scientific sample preparation molds and effective sample preparation measures are not taken, it is difficult to obtain the cohesion required for indoor geotechnical tests. Cohesive soil sample

In addition, if the cohesionless soil sample is separated from the geotechnical sample device, it is very easy to cause different degrees of damage to the cohesionless soil sample, which will affect the quality of the sample preparation and the accuracy of the subsequent test. Therefore, it is recommended that the cohesionless soil The sample is directly prepared on the sample installation base of the geotechnical sample device

[0005] At present, there is no universally recognized and unified cohesion-free soil sample preparation device. The cohesion-free soil sample preparation device in the existing literature and patents still has the following three shortcomings: (1) The double-lobe mold used is directly placed on the geotechnical test sample. On the sample installation base of the sampling device, no protection measures are taken for the connection between the double-lobe mold and the sample installation base, and it cannot be guaranteed that the impact of the double-lobe mold on the double-lobe mold and the compacted sample during the sample preparation process of non-cohesive soil will be guaranteed. The impact of the connection with the sample mounting base may affect the uniformity of the bottom of the prepared sample and the coincidence and connection of the central axis of the sample and the sample mounting base; (2) During the sample preparation process of non-cohesive soil, no auxiliary impact In other words, it cannot guarantee the consistent falling height of the compaction, nor can it locate the compaction area of ​​the compaction hammer during each compaction (there may be eccentric compaction), which will have an adverse effect on the uniformity of sample preparation; (3) double The top of the flap mold is flush with the top of the sample, and no measures are taken to assist the top soil sample preparation. The height of the top soil filling exceeds the height of the double flap mold. On the one hand, the quality of the poured soil sample may be lost during the compaction process And pollute the geotechnical test device. On the other hand, in order to reduce the loss of sample quality, the soil on the top surface of the general sample will be poured in the top center area of ​​the sample as much as possible, resulting in uneven soil density in the top layer of the sample.

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