Original soft clay hollow cylinder sample manufacture method

Abstract

The invention discloses a sampling method of status quo soft clay hollowness column sample. It includes the steps as follow: (1) fixing the core status quo soft clay hollowness column ample on the positioning board of cut core machine; (2) fixing the undisturbed sample between the drive dial and driven dial, cutting the outwall by drawknife. After the outwall forming, placing the fittings of block retaining ring,both steel model to fix sample;(3) Driving cut core machine drill pipe, cutting and fetching the core of sample by spiral bit and dismantle tool point slice; (4) every time when fetch the depth to 2cm, back out drill pipe, draw out overburden layer, and reset drill bit, fetching core repeat;(5) stop fetching core when the accumulation depth exceed standard depth 2cm;(6) unbolting the sample, shaving off the fluctuation end, finish preparation of sample. The invention can set the status quo soft clay hollowness column sample, the effect of perturbation and pile soil is small, providing the equipment bond guarantee for developing the experimental investigation of status quo soft clay under the complex stress condition.

Description

technical field [0001] The invention relates to a sample preparation method of an original soft clay hollow cylinder sample. Background technique [0002] Molding the soil into a hollow cylindrical sample provides the possibility to simulate the stress state of the soil under complex stress path conditions in the laboratory and carry out related property research. However, there are few experimental studies on undisturbed clay hollow cylinder samples at home and abroad. One of the important reasons is that there is no "universal" hollow sample preparation technology suitable for various soil properties. In principle, there are two main sample preparation methods for undisturbed clay samples: mechanical and electroosmotic. The mechanical coring method is represented by the research results of the Imperial College of Technology in the United Kingdom. The application object is London super-consolidated clay with high strength. The method is to fix the cylindrical sample horizo...

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Problems solved by technology

[0004] However, neither of the above two methods can be directly applied to the preparation of large-scale soft clay samples in the southeastern coastal areas of my country to overcome the size effect and end effect (usually the sample height is above 20cm)

Practical operation found that for large-size soft clay samples, the mechanical step-by-step drill-pipe coring method has the following disadvantages: 1) The step-by-step drill-pipe coring method makes the sample lose its viability after the first small hole coring. The alignment of the hole center means that the drill pipe lacks a supporting point in the subsequent drilling process. For soft clay, it is easy to cause the vertical advancement of the coring surface to be unable to be maintained, resulting in partial hole; 2) Step by step The multiple hole forming method increases the probability of disturbing the sample; 3) The more critical issue is to use a single drill to take the soil. Due to the high viscosity of the soft clay, the cut hole core soil chips will not fall under the action of gravity. It falls off, but adheres to the inner wall for the second time, and adheres to the hole wall soil to hinder drilling.

Once the drilling tool works on the hole wall with residual soil debris, the soil debris and the hole wall soil will be mixed together, and the sample will be greatly disturbed or even destroyed.

[0005] The main disadvantages of the electroosmotic sample preparation method are: 1) For the soft clay samples in the southeastern coastal areas of my country, the water content of many soils is far from the level that can be used for this method, that is, it is difficult to Produce ideal lubricating effect; 2) The electroosmotic method requires that the wire used to cut the inner core during the core removal process must be kept in a suspended tension throughout the entire height of the hole core

However, it is found through actual operation that the wire can only be fully tensioned when the sample size is small (usually less than 15cm in height) and the resistance between the inner core and the hole wall is small. Generally speaking, during the tensioning process, the wire is actually in a varicose state in the middle section of the sample, so even if the sample is cut, it is difficult to ensure the standard shape of the inner wall of the sample

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