Original soft clay hollow cylinder sample inner core cutting device

Abstract

The invention discloses an inner core cutter of a hollow cylindrical sample of soft clay. It has a casing, the upper end of the casing is provided with a cutting edge, the lower end of the casing is connected with the detachable casing bottom bracket through the casing bottom bracket-casing positioning screw, and the detachable soil holding bracket is arranged above the detachable casing bottom bracket. There is a pressure relief hole on the detachable soil holder, and a main drill bit is arranged in the middle of the casing. The main drill bit is composed of a spiral drill bit and an inner edge blade, and is connected with a drill pipe. The drill pipe passes through the detachable soil holder and the bottom of the detachable casing. The brackets are respectively fixed by the soil support-drill pipe set screw and the casing bottom support-drill pipe set screw. The detachable blade is composed of an outer edge blade and a horizontal blade, and is rigidly connected to the main drill bit through the blade set screw. The casing is cylindrical. The cutter can successfully prepare the hollow cylindrical sample of undisturbed soft clay, and the disturbance and extrusion effect on the sample during the cutting process are small, which provides equipment guarantee for the experimental research of undisturbed soft clay under complex stress conditions.

Description

technical field [0001] The invention relates to an inner core cutter of a hollow cylindrical sample of soft clay. 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" technology suitable for various soil properties for cutting the inner core of clay samples. In principle, there are two main coring 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 uses 7 drills with different diameters to cor...

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Problems solved by technology

[0003] 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.

[0004] 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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