JPH076181B2 - Ground frozen sampling method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a ground frozen sampling method and a ground freezing sampling method which can be used for investigating physical properties and mechanical properties of ground required in various designs in the fields of civil engineering and construction. It relates to the device.

[Conventional technology]

2. Description of the Related Art Conventionally, a frozen sampling method has been used for collecting a sample for a geological survey of the ground or the like so that the sample can be collected without being disturbed as it is. In this freezing sampling, it is extremely important from the viewpoint of economical efficiency, etc. to effectively collect a sample of a required size in an undisturbed region.

FIG. 7 is a diagram showing an example of such a conventional frozen sampling method, in which 1 is a hole, 3 is a borehole wall,
4a is a frozen outer tube, 4b is a frozen inner tube, 5 is a heat insulating material, 7 is a double core tube, 7a is an outer tube, 7b is an inner tube, 8 is a hollow shaft, 15 is muddy water, 16 is a steel tube, 17 is a positioning bottom plate, 18 is a through hole.

In the figure, the hole 1 for installing the freezing tube has a large diameter corresponding to the diameter of the sample to be sampled, and is dug to reach the upper limit position of the sample collection depth. A steel pipe 16 is installed. Further, a positioning bottom plate 17 having a through hole at the installation position of the freezing tube and at the insertion position of the double core tube 7 is installed at the bottom bottom of this hole, and the freezing tube is inserted through the through hole at the center of the positioning bottom plate 17. The hole to be inserted is dug to the sampling depth, and the frozen outer tube 4a,
A frozen inner tube 4b is installed. This freezing tube 4 is provided with a heat insulating material up to the bottom of the hole.

In this way, the ground below the bottom plate is frozen to the required thickness through the freezing pipe, and then a double core tube is inserted through the through hole 18 to core-cut the frozen soil to the non-frozen part, perform core sampling and raise the core tube to the ground. ing.

By providing the positioning bottom plate 17 at the bottom of the hole 1 as described above, the excavation accuracy of the core cutting at the time of core sampling is ensured, and a high quality sample that is not disturbed even in the deep stratum is collected as needed. Is possible.

[Problems to be solved by the invention]

However, in the freezing sampling method shown in FIG. 7, the method of freezing up to just below the positioning bottom plate of the hole 1 for installing the freezing tube is adopted, and therefore the load that suppresses the upward pressure due to the expansion of the ground during freezing is applied. Therefore, the ground expands upward during freezing, and as a result, the freezing area is disturbed and high quality sampling cannot be performed. Further, in order to discharge the cutting soil, the muddy water 15 must be filled in the hole 1 having a large diameter, which causes a drawback that a large amount of drilling muddy water is required.

The present invention is for solving the above-mentioned problems, and it is possible to easily perform high quality sampling without disturbing the freezing area, and a method and apparatus for ground freezing sampling that requires a small amount of drilling mud. The purpose is to provide.

[Means for solving problems]

Therefore, the present invention, a step of excavating a large diameter hole, a step of installing a guide means in the excavated large diameter hole, a heat insulating material is attached to a predetermined depth from the bottom of the large diameter hole, deeper than the predetermined depth. A step of installing a freezing tube for freezing, a step of installing a coring guide tube through a guide means,
A method for ground freezing sampling, including a step of performing core sampling through a coring guide tube in a state where a tip portion of the coring guide tube is included in a freezing area, and a boring hole excavated through the first guide tube in the method. A method of ground freezing sampling, which comprises the step of placing a water blocking material on the ground, and the step of placing a second guide tube for coring through the first guide tube after the water blocking material is placed, or a method further comprising the method. Ground freezing sampling method including a step of installing a second guide tube for coring through the first guide tube and a step of injecting a water blocking material between the first and second guide tubes, and a large diameter hole The guide means installed in the, the coring guide tube installed through the guide means, and the heat insulating material is attached to the bottom of the large-diameter hole to a predetermined depth, and the deeper part than the predetermined depth is frozen. And a ground freezing sampling device having a core tube to be inserted through a coring guide pipe, and at least one upward air blowing hole further fixed to the device by a fixing means. And a ground freezing sampling device having a first guide tube and an air lift tube to which compressed air is pumped and whose tip opening is connected to the air blowing hole, or to extend to the ground surface through a guide means in the device. Frozen sampling with a coring guide tube that is installed in the air conditioner and is provided with at least one upward air blowing hole, and an air lift pipe that is fed with compressed air and has a tip opening connected to the air blowing hole. Characterized by the device.

[Action]

The ground freezing sampling method and device of the present invention is to dig a large-diameter hole and freeze it by using a freezing pipe provided with a heat insulating material from the bottom of the large-diameter hole to a predetermined depth, thereby freezing the area and the large-diameter hole. A predetermined space is provided between the bottom and the bottom of the water, and as a result, a predetermined load is applied to the freezing area to prevent the frozen part from expanding and it is possible to collect a sample without any disturbance. The combination of casting and expansion of the freezing area prevents groundwater from entering the freezing area from the upper and lower ends of the coring guide tube, and pumps the drilling mud through the guide tube to reduce the amount of drilling mud. You can

〔Example〕

 Hereinafter, embodiments will be described with reference to the drawings.

FIG. 1 is a diagram for explaining one embodiment of the ground freezing sampling method according to the present invention, FIG. 2 is a plan view of FIG. 1 seen from above, and FIG. 3 is a diagram for explaining water stoppage. , The same numbers as in FIG. 4 indicate the same contents. In the figure,
6a is the first guide tube, 6b is the second guide tube, 9 is the connection,
10 is a backfilling part, and 11a and 11b are water blocking materials.

In the figure, first, the large-diameter hole 1 is excavated, and the first
Install the guide tube 6a. Any number of guide tubes may be installed, and in some cases, one may be installed. The first guide tube 6a is used for positioning when core sampling is performed and for preventing the object installed through it from moving. After the installation of the first guide tube, the hole 1 can be prevented from collapsing by backfilling the hole 1 as shown in the figure and fixing the guide tube by the backfilling portion 10. . Note that this backfilling does not necessarily have to reach the ground surface. Further, instead of such backfilling, a steady rest (not shown) may be provided on the head portion of the guide tube. In that case, a steel tube may be installed to prevent collapse of the hole 1 or the like. .

After installing the first guide tube 6a, the freezing tube part is bored to install the freezing tube guide tube 2 and the freezing outer tube 4a and the freezing inner tube 4b therein. This frozen outer tube 4a
A heat insulating material 5 is attached to the inner surface of the. The heat insulating material 6 is provided from the bottom of the hole 1 to a predetermined depth, for example, to a depth of 3 m or more from the bottom of the hole 1, so that a portion deeper than the predetermined depth from the bottom of the hole 1 is frozen. Note that the freeze tube does not have to be one.
In this way, the freezing is started by supplying the refrigerant through the freezing outer pipe 4a and the freezing inner pipe 4b. In this freezing process,
The frozen portion A tries to expand, but not to mention the sides,
The upward expansion pressure is also suppressed by the load of the ground C portion (non-frozen portion) in the figure, and eventually the expansion of the frozen portion is suppressed, so that there is no disturbance in the frozen region. In this case, the backfill portion 10 also acts as a load that suppresses expansion of the frozen portion. When the frozen part has reached the area A in the figure,
Boring for installing the second guide pipe 6b is performed through the guide pipe 6a up to the area A, and the boring hole is placed until the surface of the water blocking material reaches the inside of the first guide pipe 6a. After the water blocking material has been cast, the second guide tube 6b is installed, and then the water blocking material 11a in the tube is removed. By this process
As shown in FIG. 3, the water blocking material 11b stays between the guide tube 6a and the second guide tube 6b, thereby stopping water. The water blocking material may be directly injected between the first guide pipe 6a and the second guide pipe 6b. When the freezing progresses further to the area B in the figure, the second guide tube 6b
The tip portion of will also be included in the frozen region. Therefore, even if the core sampling is performed by the double core tube 7 in this state, the groundwater does not enter from the tip portion of the second guide tube, and in the core sampling,
If the tip of the core tube is kept out of the freezing area, there is no risk of groundwater entering the freezing area.

In the above step, the freezing tube is installed after the first guide tube is installed, but it goes without saying that this step may be reversed or may be carried out in parallel. Absent.

In core sampling, the excavated mud is pumped up between the inner pipe 7b and the outer pipe 7a of the double core tube and the first and second guide pipes in order to discharge cutting soil. The pipe diameter of 6a is, for example, 30-40 cm
Since it is not so large, it is possible to use a small amount of drilling mud.

As shown in FIG. 4, a second guide tube 6b having a length reaching the ground surface may be used, and as shown in FIG. 5, a positioning bottom plate 15 is used instead of the first guide tube. The length of the second guide pipe 6b reaching the ground surface may be used. In both cases of FIG. 4 and FIG. 5, there is no risk that groundwater will enter the freezing area through the guide pipe, so there is no need to cast or inject a waterproof material.

FIG. 6 is a diagram showing a guide pipe structure for facilitating pumping of the drilling mud, FIG. 6 (a) shows a case where there is one blowing hole, and FIG. 6 (b) shows a case where there are plural blowing holes. Is. In the figure, 12 is an air lift pipe, 13 is a blowing hole, and 14 is a bubble.

In the figure, an air lift pipe 12 is mounted along the outer wall of the guide pipe 6a (or 6b), and its tip is open to a blowout hole 13 provided in a lower portion of the guide pipe. Blowout hole
Reference numeral 13 is open upward, and by sending compressed air from the air lift pipe 12, air can be blown upward into the guide pipe to facilitate pumping of muddy water.

It should be noted that one blowout hole is effective as shown in FIG. 6 (a), but a plurality of blowout holes may be provided as shown in FIG. 6 (b) and a plurality of air lift pipes may be provided. The air lift pipe is not necessarily outside the guide pipe and may be provided inside the guide pipe as long as it does not interfere with the core tube insertion or removal, or the air lift pipe is inserted into the guide pipe during core sampling after inserting the core tube. The air lift pipe may be pulled up at the time of pulling up. Needless to say, it is not always necessary to use the air lift pipe if it can be sufficiently pumped up without using it.

〔The invention's effect〕

As described above, according to the present invention, since a region deeper than the bottom of the large-diameter hole is at least deeper than the predetermined depth is a frozen region, a load due to earth pressure is applied to the frozen region, and as a result, the frozen region is frozen. Can be prevented from expanding upward.

Fig. 8 shows the relationship between the restraint pressure and the frost heave rate (= volume increase after freezing / volume before freezing) when the content of fine particles in the ground is used as a parameter. It can also be seen that the larger the amount of fine particles, the greater the frost heave.

Figure 9 shows the liquefaction strength after freezing and melting of a sample with a fine particle content of 10% under a certain constraint pressure. Shear stress (vertical axis) = applied force / Restraint pressure, number of repetitions (horizontal axis) = number of continuous vibrations, ○ means restraint pressure 1kg / cm ²
Shows the sample freeze-thawed, and ● shows the sample freeze-thawed at a restraining pressure of 0.2 kg / cm ² , and the liquefaction strength of the sample not frozen / thawed is shown by the solid line in the figure.

Thus, at a constraining pressure of 1 kg / cm ² , it shows the same liquefaction strength as the sample that was not frozen and thawed, and it can be seen that the disorder due to freeze expansion did not occur.

Therefore, according to the present invention capable of obtaining a sufficiently large restraint pressure, it is possible to reduce the frost heave rate and sample a sample in the same ideal state as a sample that is not frozen / thawed.

In addition, since a guide tube is installed in the large diameter hole and core sampling is performed through the guide tube, the discharge of cutting soil can be done with a small amount of drilling mud, and an air lift tube can be attached to the guide tube to remove it. If compressed air is blown out from the blowout hole provided in the lower portion, it is possible to easily pump up the muddy water.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of a ground freezing sampling method according to the present invention, FIG. 2 is a plan view of FIG. 1 seen from above, and FIG. 3 is a diagram for explaining the installation of a waterproofing material. 4 and 5 are views showing another embodiment in which a long tube is used as the second guide tube 6b, FIG. 6 is a view showing a guide tube structure equipped with an air lift tube, and FIG. 7 is a conventional example. Fig. 8 shows an example of the freezing sampling method of Fig. 8, Fig. 8 shows the relationship between confining pressure and freezing rate when the fine grain content of the ground is used as a parameter, and Fig. 9 shows the fine grain content of 10%. It is a figure which shows the liquefaction strength of the sample of FIG. 1 ... hole, 2 ... freezing tube guide tube, 3 ... boring hole, 4a ... freezing outer tube, 4b ... freezing inner tube, 5 ... heat insulating material,
6a …… first guide tube, 6b …… second guide tube, 7 ……
Double core tube, 7a …… Outer tube, 7b …… Inner tube, 8 ……
Hollow shaft, 9 ... Connection, 10 ... Backfill part, 11a, 1
1b …… Water stop material, 12 …… Air lift pipe, 13 …… Blowout hole, 14 …… Bubbles, 15 …… Drilling mud, 16 …… Steel pipe, 17 ……
Positioning bottom plate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Shinomoto 2-16-1, Kyobashi, Chuo-ku, Tokyo Within Shimizu Corporation (72) Inventor Satoshi Akagawa 2-16-1, Kyobashi, Chuo-ku, Tokyo Shimizu Construction Co., Ltd. (56) Reference JP-A-61-251744 (JP, A)

Claims (8)

[Claims] 1. A step of excavating a large-diameter hole, a step of installing guide means in the excavated large-diameter hole, a heat insulating material is attached to a predetermined depth from the bottom of the large-diameter hole, and a deep portion is frozen from the predetermined depth. The step of installing the freezing tube to be used, the step of installing the coring guide tube through the guide means, and the step of performing core sampling through the coring guide tube with the tip of the coring guide tube included in the freezing region. Ground frozen sampling method including and. 2. The ground frozen sampling method according to claim 1, wherein the guide means is a guide tube fixed by a fixing means. 3. The ground frozen sampling method according to claim 1, wherein the guide means is a positioning bottom plate, and the coring guide tube is a guide tube extending to the ground surface. 4. A step of excavating a large-diameter hole, a step of installing a first guide pipe in the large-diameter hole, a heat insulating material is attached to a predetermined depth from the bottom surface of the large-diameter hole, and a portion deeper than the predetermined depth is attached. A step of installing a freezing pipe for freezing, a step of placing a water blocking material in a boring hole excavated through the first guide tube, and a second step for coring after passing the water blocking material through the first guide tube Frozen ground sampling method including a step of installing a guide tube, and a step of performing core sampling through the second guide tube for coring in a state where the tip end of the second guide tube for coring is included in the freezing region. . 5. A step of excavating a large-diameter hole, a step of installing a first guide pipe in the large-diameter hole, a heat insulating material being attached to a predetermined depth from a bottom surface of the large-diameter hole, and a portion deeper than the predetermined depth. A step of installing a freezing tube for freezing, a step of installing a second guide tube for coring through the first guide tube,
Injecting a water blocking material between the first and second guide tubes,
The second guide tube tip is included in the freezing area
Ground freezing sampling method including the step of performing core sampling through the guide tube of the above. 6. A guide means installed in a large-diameter hole, a coring guide tube installed through the guide means, a heat insulator up to a predetermined depth from the bottom surface of the large-diameter hole, and a deeper portion than the predetermined depth. A ground freezing sampling device comprising a freezing tube for freezing and a core tube inserted through a coring guide tube. 7. A first guide tube installed in a large-diameter hole, fixed by a fixing means and provided with at least one upward air blowing hole, and a first coring ring installed through the guide means. No. 2 guide tube, a heat insulating material is attached to the bottom of the large-diameter hole to a predetermined depth, and a freezing tube for freezing a deeper portion than the predetermined depth, and a core tube inserted through a second guide tube for coring. A ground freezing sampling device comprising: a compressed air; and an air lift pipe having a tip opening connected to the air blowing hole. 8. A guide means installed in a large diameter hole, a coring guide tube installed so as to extend to the ground surface through the guide means, and provided with at least one upward air blowing hole, and a large diameter guide tube. A heat insulating material is attached to a predetermined depth from the bottom surface of the hole, a freezing tube for freezing a deeper portion than the predetermined depth, a core tube inserted through a coring guide tube, and compressed air are pressure-fed, and the tip opening is A ground freezing sampling device having an air lift pipe connected to an air blowing hole.