Sampling method of large-size completely and heavily weathered red bed sandstone undisturbed sample

Abstract

The invention discloses a sampling method for the original sample of large-scale fully weathered red bed sandstone, which comprises the following steps: manually excavating to the designed sampling depth at the selected intended sampling position; determining the set lithology and weathering type; expand the working face around the proposed sampling location; scrape the sandstone sample into a rock pillar with the inner diameter of the hard circular pipe used for sampling; put the half-separated hard circular pipe on the rock pillar, and use fine particles to fill the gap Fill it up, then fix it; cut off the bottom of the rock pillar, scrape the top and bottom of the rock pillar, and then fix the steel plate on the top and bottom of the rock pillar; wrap the hard circular tube and steel plate with dense gauze, Then fix it, apply liquid paraffin on the emery cloth; wrap it with plastic film, fix it and put it into the box, fill the space around it tightly with broken foam blocks to the top of the box, cover the top plate of the box; transport it to the laboratory. The sampling method of the invention has the advantages of simple operation, little disturbance, good impact resistance, low cost and easy transportation.

Description

technical field [0001] The invention relates to a sampling method of undisturbed sandstone samples, in particular to a sampling method of undisturbed samples of large-scale fully weathered red bed sandstone. Background technique [0002] Red bed sandstone mainly has two typical structural forms: granular clastic structure and muddy cemented structure, and its strength varies greatly due to differences in cementing materials and weathering degrees. After excavation or blasting, most red bed sandstones can be disintegrated and broken by the atmospheric environment, or even muddy, so the size and particle gradation of the rock blocks will change with the time course of the dry-wet cycle, and their physical and mechanical properties will also change [0003] The existing methods for taking fully weathered and strongly weathered red sandstone samples are: [0004] 1. In terms of the designed depth, first cut out fully weathered and strongly weathered red sandstone cylinders, an...

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Problems solved by technology

[0008] The disadvantage of the above-mentioned first method is that the sample is too small during manual sampling, the sample is greatly disturbed, and the structure of fully weathered and strongly weathered red sandstone cannot be well maintained, and the sample is easy to lose water and the storage time is short

[0009] The second to fourth methods mentioned above adopt the static pressure sampling method of drilling rigs, and their disadvantages are: due to the high strength of the fully weathered and strongly weathered red bed sandstone, it is difficult to press into the rock formation by static pressure, or the sample structure is destroyed during the pressing process ;During drilling rig hammering sampling, due to the impact of hammering vibration, the structural properties of fully weathered and strongly weathered red sandstones were disturbed, and the samples were often destroyed; when half-box tube sampling was soaked in water during drilling, The water content of the rock mass changes greatly, and its structure is also disturbed

[0010] In addition, in the above-mentioned various methods, the collected samples are generally sealed with adhesive tape, which is easy to lose water and has a short storage time.

[0011] Due to the defects of the above-mentioned traditional sampling method, the size of the fully weathered and strongly weathered red sandstone samples obtained by the above-mentioned traditional sampling method is small, generally not larger than 89mm, and the maximum is 108mm. The soil sample obtained by the half-box tube method is only 75mm, which cannot satisfy the large Therefore, the traditional sampling method of fully weathered and strongly weathered red sandstone samples can meet the requirements of general building tests, but cannot meet the requirements of large-scale tests using undisturbed soil samples on sample size, disturbance degree, physical and mechanical properties and storage time. on request