Sampling method for undisturbed soil sample on large-sized non-saturated structured plateau drift bed

Abstract

The invention discloses a sampling method for an undisturbed soil sample on a large-sized non-saturated structured plateau drift bed. The sampling method comprises the following steps: selection and treatment of a sampling center hole; selection and treatment of sampling peripheral holes: performing drilling and treatment around the sampling center hole, and obtaining multiple sampling peripheral holes surrounding the sampling center hole; formation of sample columns and in-situ pretreatment: digging positions outside the sampling peripheral holes to form annular pits, forming initial sample columns at positions encircled by the annular pits, and performing wrapping and wax injection on the initial sample columns, thus obtaining the sample columns; removal of the sample columns; post-treatment of the sample columns and formation of samples: performing wax injection and overall wrapping on the sample columns, thus obtaining the samples, and transporting the samples to a laboratory to complete sampling. The sampling method disclosed by the invention is convenient to operate, small in interference, high in impact resistance, low in cost and easy to transport and particularly suitable for sampling of the undisturbed soil sample on the large-sized non-saturated structured plateau drift bed, and the obtained sample can meet the requirement of a large-scale soil test.

Description

technical field [0001] The invention relates to a sampling method for undisturbed soil samples of plateau moraine layers, in particular to a sampling method for undisturbed soil samples of large-scale unsaturated structural plateau moraine layers. Background technique [0002] Moraine soil is the soil accumulated by glaciers, generally composed of blocks, gravel, breccia, sand and a small amount of silt and clay accumulated by glaciers. The elevation of the moraine layer distribution area is generally above 3500m, with few engineering constructions, low level of research on the moraine layer, and lack of engineering experience. In recent years, some major engineering projects have been built or are under construction in the moraine layer distribution area in China, such as Kangding Airport, Daocheng Airport, Sichuan-Tibet Expressway, Sichuan-Tibet Railway, etc., and preliminary results have been obtained in the research on the engineering characteristics of the moraine layer...

AI Technical Summary

Problems solved by technology

[0005] (3) After the structure of the fine-grained moraine layer is destroyed, the bearing capacity and shear resistance will rapidly decay or even be lost under the action of water immersion.

[0012] 5. The collected samples are generally sealed with tape or thin layer of paraffin, which is easy to lose water and has a short storage time.

[0014] 1. Large-sized samples cannot be taken when sampling by traditional mechanical or manual methods; because the sample is too small, the sample is greatly disturbed, especially when the sample contains gravel, breccia and coarse sand, the sample is often broken, Does not maintain moraine layer structure well

[0015] 2. The sample volume is small, because the sample cannot contain gravel and breccia, so it cannot truly reflect the structural characteristics and engineering properties of the moraine layer

[0016] 3. The moraine layer sample taken by the traditional method is easy to lose water in the plateau area. Even if the seal is good, a layer of water droplets or water mist is often formed on the wall of the sample cylinder, the water content decreases, and the physical and mechanical properties of the moraine layer change greatly. , short storage time

[0017] 4. The size of the moraine layer sample obtained by the 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 meet the requirements of large-scale sample testing;

[0018] 5. When sampling with the static pressure method of the drilling rig, because the moraine layer contains gravel and breccia, it is difficult to press the static pressure into the formation, or the sample structure is destroyed during the pressing process; when sampling with the hammering method of the drilling rig, due to the hammering Affected by vibration, the structure of the moraine layer is disturbed, and the samples are often destroyed; when the semi-box tube sampling method is soaked in water during the drilling process, not only the water content changes greatly, but more importantly, its structure is affected by water. Influenced by wetting, disintegration and softening; when artificially exploring pits (wells) for sampling, in plateau areas, human dexterity is greatly reduced, and it is easy to loosen materials near the edge of the sample and cause sample damage. During the sampling process, precipitation, humidification, freezing and thawing and other damages occurred

[0019] 6. Traditional methods can meet the requirements of general building tests, but cannot meet the requirements of sample size, disturbance degree, physical and mechanical properties and storage time for large-scale tests using undisturbed soil samples