JPH0547720B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the principle of a sampler for soil and rocks.

Recently, there has been a desire to collect undisturbed samples of very loose to well-compacted sand, hard clay soil, soft rock, or crushed rock. In this case, if the inner diameter of the tube that houses the sampler and the cutting edge at its tip are approximately the same, a large frictional resistance will work between the inner surface of the tube and the sample, making it difficult for the sampler to penetrate, or the collected sample may The problem is that it gets disturbed due to compression due to friction. Therefore, attempts have been made to reduce the frictional resistance by reducing the inner diameter of the cutting edge, but the soil that enters the sampler expands and its strength decreases, and the frictional resistance when pulling the sampler is small. This results in problems such as the sample falling off and the gap between the sample and its storage tube making it easy to disturb during transportation.

Among these, various ideas have been made regarding methods for preventing samples from falling off. For example, core catchers have been used for a long time to prevent cores from falling off from bedrock or hard ground. Recently, several methods of preventing sand sampling have been devised. This is because sandy ground does not have adhesive strength, so it easily falls off.
Some typical examples are as follows. Application of core catcher (Jetko 54-24711)
(Japanese Patent Publication No. 57-41687), one in which a screen is attached to the shoe part and a wire is pulled to close the tip of the sampler (Japanese Patent Publication No. 57-41687), and one in which a compressive force in the horizontal direction is applied to the sample through a flexible membrane (Japanese Patent Publication No. 57-41687). 37−
18545), a method of plugging by twisting a flexible tube attached near the tip of the shoe (Special Publication No. 1854-
31536), as well as other well-known facts, according to the soil survey method published by the Society of Soil Engineers of Japan, before the sampler is pressed into the ground and pulled out, chemicals and asphalt are injected near the tip of the sample from near the shoe. Some types use a fixed piston attached to the sampler to utilize the vacuum force generated between the top surface of the sample and the piston when the sample tries to fall off, and some types use a double tube to supply compressed air into the sampler. There are those that supply air (publication number 42960/1986), and those that freeze the sandy ground beforehand and then collect the sample. In order to solve problems such as friction between the side of the sample and the storage tube, the sample will be compressed and disturbed, and the pressure force of the sampler into the ground will increase. Many efforts have been made. For example, there is a method in which the inner diameter of the sample storage tube is made larger than the inner diameter of the sampler's cutting edge, and a method in which a number of thin flexible membranes are protruded from near the cutting edge and attached to the side of the sample entering the sampler to collect the sample. oil sampler,
There are rotary leaf oil samplers that are an improved version of this. However, with this sampling method, samples tend to fall off on sandy ground that does not have adhesive strength.
There are disadvantages such as the need for extensive installation. Further, a method that uses the above-mentioned sample drop prevention method in combination has not yet been developed because the apparatus would be complicated.

When a sampler is forced into the ground to collect a sample, if the inner diameter of the cutting edge and the inner diameter of the sample storage tube are the same, the friction between the sample and the inner surface of the storage tube will increase and the sample will be compressed. Furthermore, when the inner diameter of the cutting edge is made smaller, the sample expands within the storage tube. In this way, with conventional samplers, the sample is either compressed or expanded, and the stress in the ground differs from the natural state, resulting in disturbance of the collected sample. A known method for preventing this is to freeze the ground beforehand before collecting samples, thereby minimizing the effects of compression and expansion during sample collection. However, this method has a problem with the expansion of the ground due to freezing, and can only be applied to specific sandy soils where the proportion of fine particles mixed in is extremely low and where this effect is negligible.

Anti-vibration measures are commonly used to prevent samples from being disturbed by vibrations during transportation, but if there is a gap between the storage tube and the sample, it may cause damage to samples that do not have adhesive strength, such as sandy ground. Disturbances due to vibration will occur. Practical methods to prevent this include pouring melted paraffin into the gap, and applying pressure equivalent to the earth's pressure using springs from both ends of the storage pipe. However, these methods are only incomplete post-treatments because they are carried out after the sample has already been expanded or compressed within the storage tube.

The present invention aims to overcome these conventional drawbacks and relates to a method for collecting samples without substantially changing the natural state of the ground from which the sample is to be collected. Hereinafter, the method of the present invention will be explained with reference to the drawings.

FIG. 1 shows the assembled sampler.
First, determine the vertical ground pressure and horizontal ground pressure of the ground where the sample is to be taken, and then decide the length of the spacer 11 to generate lateral pressure equivalent to the horizontal ground pressure.
This is set in the inner tube 15. Next, the sample storage tube 18, the lateral pressure spring 16, the annular piston 1
Insert 7 in sequence. As shown in the figure, after aligning the sampler head 5 with the upper end of the screw screw 10, use the pressure adjustment screw 27 to adjust the distance between the vertical pressure spacers 26 so that the piston pressure is equivalent to vertical earth pressure. and guide pipe 1
Put it in 9. Next, the piston 32 and the guide pipe 19, the shoe 31 and the inner pipe 15, and the bit 30 and the outer pipe 14 are connected, respectively. The piston 32 is prevented from coming out of the shoe 31 by a stopper 34.

Estimate the time required for sampling and collect fluid 20
After adjusting the solidification time of
is compressed and balanced at a predetermined pressure. After the pipe 36 and the tips of the air vent pipe 33 are stopped, the lid 35 is put on. This means that pressure equivalent to vertical and horizontal ground pressure is maintained within the sampler.

Add a boring rod to swivel 1 and lower the bottom of the borehole. When the rod is rotated with its vertical movement fixed, the screw screw 10 rotates. This screw 10 has a vertical groove, and the rotary head 12 rotates using this groove as a guide. The rotational force rotates the outer tube 14 via the vibration isolating rubber 13 and several shearing pins 6, and the bit 30 excavates the ground. Boring water passes through the rod, passes between the double-pipe flexible pipe 2, the sampler head 5 and the inner pipe 15, is emitted from the shoe 31 and the water hole, and is collected together with the excavated waste into the outer pipe. It is transported to the ground through the outside of the

The thrust force for pushing the sampler into the ground is such that the rotation of the screw screw 10 causes the non-rotating thrust head 8 to move downward. The rotary head 12 of this head 8 is also lowered at the same time via the bearing 7. The movement of the head 12 is controlled by the inner pipe 15 via a spring 9 which adjusts the protrusion of the shoe 31 from the bit 30 depending on the hardness or softness of the ground.
transmitted to.

As described above, by fixing the vertical movement of the boring rod and rotating it, the outer pipe 14 excavates while rotating, while the inner pipe 15 does not rotate and digs into the ground while cutting the ground to a predetermined diameter with the shoe 31. It will be press-fitted into the In order to prevent the inner tube 15 from rotating at this time, the shoe 31 is alternately tapered at two different angles.

When the inner tube 15 and the shoe 31 are press-fitted into the ground, the sample cut by the shoe enters the sampler. At this time, a pressure equivalent to vertical earth pressure is automatically applied to the upper surface of the sample by the spring 28 via the piston 32, and a circumferential pressure equivalent to horizontal earth pressure is automatically applied by the fluid 20. The piston 32 is supported by a support pipe 22 that does not move up and down while maintaining vertical pressure. Since the support pipe 22 rotates, a bearing 23 and a spherical seat 24 for point support are provided to prevent rotational force from being transmitted to the piston 32. When the sample enters the sampler, the air within the guide pipe 19 and inner tube 15 will be compressed. This air passes through the ventilation holes 25, 21, and 4, and is allowed to escape from the ventilation hole 3 equipped with a backflow prevention pipe. The protrusion 29 is a centrifuge that prevents the piston 32 from swinging in the horizontal direction.

FIG. 2 shows a state in which the sample has entered the sampler by a predetermined length. If you wait in this state until the time set at the time of assembling the sampler has elapsed, the fluid 102 around the sample will solidify while maintaining its pressure. Also, the vertical pressure acting on the piston is due to the frictional force with the piston circumferential surface and the recess 10 of the piston.
1 will be transmitted to the sample storage tube 18 via the solidifying material 102. After a predetermined period of time, the sampler is raised to the ground, the bit 30 and the shoe 31 are removed, and the collected sample integrated with the sample storage tube 18 and piston 32 is pulled out from the sampler. The piston 32 and the guide pipe 19 are separated, a cap is placed over the lower end of the sample, and the cap is fixed to the sample storage tube. A fluid is injected between the cap and the end face of the sample at a pressure equivalent to the vertical pressure, and the sample is waited until solidified. Through the above operations, it is possible to collect and store undisturbed samples while maintaining the stress in the natural ground.

Figure 3 shows a sampler used for soft ground. In very soft ground, there is no need to press fit the sampler while excavating with the outer tube, so remove the outer tube 14 and bit 30 shown in Figure 1, remove the shear pin 6, and remove the sampler head 5, spring 9, etc. . Next, as shown in FIG.
The sampler head 301 is fixed to. The method of applying vertical and horizontal ground pressure equivalent pressure and the sampling method are the same as above.

FIG. 4 is designed to be applicable to cases where the void is large and the pressurized fluid easily penetrates into the sample.
A thin-walled flexible tube 404 is fixed to the piston 406, and the tube 404 is inserted between the inner tube 402 and the sample storage tube 401. When the inner tube 402 is pressed into the ground during sampling, the tube 404 is inserted from the lower end of the sample storage tube 401. The tube 404 is pulled out and the tube 404 is pulled out.
The sample is successively covered while contacting the inside of 05 and the piston 406. Therefore, the pressurized fluid 403
Since the sample is pressurized through the tube 404, the pressurized fluid 403 does not penetrate into the sample.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the assembled state of the sampler. FIG. 2 is an explanatory diagram showing a state in which a predetermined length of the sample has entered the sampler. FIG. 3 is an explanatory diagram of the sampler when used for soft ground. FIG. 4 is an explanatory diagram showing the main parts of a sampler that can be applied when the void is large and pressurized fluid easily penetrates into the sample. 1... Swivel, 2... Flexible pipe, 3, 4... Vent hole, 5... Sampler head, 6... Severing pin, 7... Bearing, 8...
... Thrust head, 9... Spring, 10... Screw screw, 11... Side pressure spacer, 12...
... Rotating head, 13 ... Vibration isolating rubber, 14 ... Outer pipe, 15 ... Inner pipe, 16 ... Side pressure spring,
17... Annular piston, 18... Sample storage tube, 1
9...Guide pipe, 20...Fluid, 21...Vent hole, 22...Support pipe, 23...Bearing, 24...Ball seat, 25...Vent hole, 26...Spacer for vertical pressure, 27... Pressure adjustment screw, 2
8...Vertical pressure spring, 29...Protrusion, 30...Bit, 31...Show, 32...Piston, 33
...Air vent pipe, 34...Stopper, 35
...Piston lid, 36...Injection pipe, 101...
... Piston recess, 102 ... Pressurized liquid (solidifying material),
301... Sampler head, 302... Inner tube,
401...Sample storage tube, 402...Inner tube, 403
... Pressurized fluid, 404 ... Flexible tube, 40
5...Show, 406...Piston.

Claims (1)

[Scope of Claims] 1. A method of lowering a sample storage pipe in the axial direction to the bottom of a borehole drilled in the ground and collecting a ground sample into the storage pipe, in which the ground sample in the sample storage pipe is subjected to pressure equivalent to the ground pressure. While applying pressure from the axial direction,
A method for collecting a ground sample, characterized in that the sample is uniformly pressurized by fluid pressure from the circumferential direction, thereby preventing changes in the size and volume of the sample. 2 Pressurize a fluid that is formulated to solidify after a set time at a pressure equivalent to earth pressure and seal it in a sample storage tube.
The pressurized fluid is injected into the gap between the inner surface of the sample storage tube and the collected sample, which is created by making the inner diameter of the tip of the cutting edge for cutting the sample from the ground smaller than the inner diameter of the sample storage tube, and pressurization is applied after the set time. The ground sample collection method according to claim 1, which comprises solidifying a liquid.