JPH0913865A - Freezing and sampling method for in situ ground and guide tube - Google Patents

Abstract

PURPOSE: To fulfill a function as a function as a guide tube, and prevent the separation of the guide tube from ground by circulating a coolant through a freezing tube for freezing the ground, and inserting a core tube for collecting the soil sample of an non-turbulent zone. CONSTITUTION: A guide tube 1 is formed out of a combination of a single freezing tube insertion tube 2 at a center, and a total of four core tube insertion tubes 3 arranged thereon at positions presumably corresponding to a non-turbulent zone. In this case, each of the tubes 1 and 4 is combined in an upright state, and integrated with one another by welding or the like, thereby fixing a piping relationship. Thereafter, cooling tubes 7 are installed on the lower side of a positioning plate 4 at a lower position, so as to enclose the external surface of the core tube insertion tubes 3, and the inlet and outlet 7a and 7b of the tubes 7 are raised. then, subsoil at a home position planned for taking a ground sample is excavated and the guide tube 1 is inserted therein for vertical installation. Thereafter, a refrigerant is circulated through a freezing tube to freeze subsoil immediately below the guide tube 1 as well as along a lower peripheral section. The guide tube 1 is thereby fixed and the core tubes are inserted therein for collecting soil samples.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-situ ground freezing sampling method for collecting undisturbed soil samples from in-situ grounds of sand layers and gravel layers, and a guide pipe used for carrying out the method. .

[0002]

2. Description of the Related Art Conventional in-situ ground freezing sampling methods developed for collecting undisturbed soil samples from in-situ grounds of sand layers and gravel layers are disclosed in, for example, Japanese Patent No. 1650193 (Japanese Patent Publication No. 3-17036) and Japanese Patent No. 3-17036. Japanese Patent No. 1768549 (Japanese Patent Publication No. 4-52803), Japanese Patent No. 1709029 (Japanese Patent Publication No. 3-80237), Japanese Patent No. 1768550 (Japanese Patent Publication No. 4-52804), Japanese Patent No. 1839511 (Japanese Patent Publication No. 5-54534). It is disclosed and publicly known in each of the above publications, and a considerable amount of construction results have already been accumulated.

Further, when the above-mentioned in-situ ground freezing sampling method is carried out, the guide tube is used for protecting the mouth of the drilled hole and contributing to the limited freezing of the ground and used as a guide when inserting the freezing tube or core tube. Also, for example, Patent No. 1
No. 839511 (Japanese Patent Publication No. 5-54534), Japanese Patent Laid-Open No. Hei 3
It is disclosed and publicly known in, for example, Japanese Patent Publication No. 5512, and is also put to practical use.

[0004]

In the implementation of the in-situ ground freezing sampling method, the guide tube has a certain function and effect, but the following problems have become apparent. First, when a refrigerant such as liquid nitrogen is circulated in the freezing pipe to advance the freezing of the ground, the freezing area of the ground is formed so that the ripples spread as if exaggerated by the dotted line A in FIG. It That is, the ground region B immediately below the guide pipe and around the lower portion of the guide pipe does not freeze easily. If it is attempted to completely freeze the ground area B, it takes several times as long as the usual time, the construction period is prolonged, and a large amount of refrigerant is consumed, which is uneconomical. Moreover, a means for confirming whether or not the ground area B is frozen has not been developed yet. Furthermore, once frozen, once the soil sample collection work is completed and the frozen pipes and guide pipes are pulled out and collected, means for artificially and rapidly thawing the necessary parts of the frozen ground have also been developed. Not not.

Secondly, when starting the work of collecting a soil sample without freezing the ground area B, first, the installation state of the guide tube itself to the bottom of the excavation hole is not completely fixed, but it slides. It cannot fully serve as a guide for a freezing tube or a core tube that is vertically inserted using a guide tube. In addition, since peeling occurs between the bottom bottom surface of the guide pipe and the bottom of the drill hole (ground), the boring water (cooling water) ejected from the tip of the core tube during the coring (drilling) with the core tube is the outer circumference of the tube. Even if the temperature rises, the peeled portion dissipates into the ground and does not return to the cooling water circulation device, so that a shortage of cooling water occurs immediately. By the way,
The cooling water is circulated at about 70 to 120 liters per minute. Since coring is usually continued for about 20 to 30 minutes per one, a large amount of cooling water is used. If the cooling water is insufficient, coring (drilling) becomes impossible immediately.

Therefore, an object of the present invention is to enable artificial, active, and rapid freezing treatment of the ground immediately below the guide pipe and the lower peripheral ground of the guide pipe, and confirm whether or not the guide pipe can be frozen. Establishing a fixed state of installation, preventing the guide pipe and ground from peeling off, preventing the escape of cooling water especially during coring, and making its circulation smooth,
And after the completion of the soil sample collection work,
And to provide a guide tube that contributes to the implementation of the in-situ ground freezing sampling method, which enables quick defrosting of the required part of the ground, and enables the extraction and recovery of the freeze tube and the guide tube. .

[0007]

As a means for solving the above problems, the invention of claim 1 freezes the in-situ ground and collects the frozen soil in the undisturbed area as a soil sample by the coring method. In the in-situ sampling method, a guide pipe that reaches a position just above the limited freezing of the in-situ ground is installed, a freezing pipe is inserted and installed through the guide pipe, and a refrigerant is circulated to the freezing pipe to advance the freezing of the ground. , A step of freezing the ground immediately below the guide tube and a lower peripheral ground of the guide tube, a step of inserting a core tube through the guide tube and collecting a frozen soil sample in an undisturbed area, After completing the sampling work, thawing fluid is circulated to the freezing pipe to thaw the frozen ground, and further to the ground immediately below the guide pipe and the lower peripheral ground of the guide pipe, and after that. Recovering the serial cryotubes and guide tube is withdrawn from the ground, respectively, characterized.

That is, according to the above-mentioned invention, the freezing of the substratum of the guide tube and the lower peripheral ground of the guide tube is performed by, for example, pouring dry ice from the ground, spraying liquid nitrogen, or pouring brine. It is characterized by advancing the freezing process and, after the completion of the soil sample collection work, introducing hot water or the like from the ground to proceed with the thawing of the direct ground plate of the guide pipe and the lower peripheral ground.

Next, the invention according to claim 2 is, in the in-situ sampling method in which the in-situ ground is frozen and the frozen soil in the undisturbed region is sampled by the coring method as a soil sample, the in-situ ground is limited. A guide tube that reaches a position directly above freezing is installed, a freezing tube is inserted through the guide tube, a refrigerant is circulated through the freezing tube to promote freezing of the ground, and cooling that is previously installed in the lower part of the guide tube is installed. Circulating a refrigerant in the pipe to freeze the substratum of the guide pipe and the lower peripheral ground of the guide pipe; and inserting a core tube through the guide pipe to collect frozen soil in the undisturbed region as a soil sample, After the soil sample collection work is completed, the freezing ground is thawed by circulating the thaw fluid to the freezing pipe and the cooling pipe, and then the freezing pipe and the guide pipe are pulled out from the ground. To yield, respectively, characterized.

The invention is characterized in that a cooling pipe previously attached to the guide pipe is used to advance the freezing process or the thawing process of the direct ground plate and the lower peripheral ground of the guide pipe. Further, in the freezing of the ground in each of the above inventions, first, the direct ground plate of the guide pipe and the lower part outer peripheral ground are frozen, and then the freezing pipe is inserted and installed through the guide pipe and the surrounding ground is also frozen. Characterize.

Next, the guide tube according to the invention of claim 4 is
It is composed of at least one freezing tube insertion tube and a plurality of core tube insertion tubes, each of which has a length to reach a position just above the limited freezing of the in-situ ground, and the freezing tube insertion tube is located at the central portion. , A plurality of core tube insertion pipes are arranged in the undisturbed region of the outer periphery of the freezing pipe insertion pipe, each pipe is arranged in parallel, the upper and lower parts are fixed by positioning plates, and the cooling pipes are arranged in the lower part. The inlet and outlet of the cooling pipe is characterized by being raised upward.

A plurality of temperature sensors are installed in the radial direction of the bottom surface of the guide tube according to the fourth aspect, and it is possible to monitor the freezing condition of the ground.

[0013]

In the invention of claim 1 or 2, as a result of artificially and positively freezing the ground immediately below the guide pipe and on the outer periphery of the lower part, the effect of superimposition with the limited freezing of the ground through the freezing pipe,
Due to the combined effect, the freezing process proceeds rapidly and the guide pipe is fixed to the ground at the bottom of the drill hole.

However, in order to complete the guide function of the guide tube, first, as in claim 3, when the ground directly under the guide tube and the lower part outer peripheral ground are frozen, the frozen pipe is inserted due to the fixing effect due to freezing. The extremely stable guide function makes it easy to perform with high precision. Also, when the direct ground plate and the lower part outer ground of the guide pipe are frozen, the guide pipe is watertightly fixed to the frozen ground, so that when the core tube inserted through the core tube insertion pipe advances while excavating. , The cooling water returns to the ground through the core tube insertion pipe without escaping into the ground, and the circulation by the cooling water circulation device is smoothly performed.

After the soil sample is collected, a thawing fluid such as warm water is circulated through the freezing pipe, and the thawing fluid is dropped from the ground directly under the guide pipe and on the lower peripheral ground.
Alternatively, the thawing fluid such as warm water is circulated through the cooling pipe to positively and rapidly proceed the thawing process, so that the withdrawal and recovery of the guide pipe and the freezing pipe can be advanced at an early stage. In particular, as in the inventions of claims 2 and 4, when the cooling pipe is integrally attached to the guide pipe in advance, the refrigerant is circulated through the cooling pipe or the defrosting fluid such as hot water is circulated, The process of freezing or thawing the ground can be artificially and positively and rapidly advanced.

Further, when the temperature sensor is installed as in claim 5, at least the frozen state or the defrosted state of the direct substrate of the guide tube can be monitored from the ground and accurately confirmed, and the accuracy of the construction can be improved. Can be expected.

[0017]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention. The guide tube 1 shown in FIG. 1 and FIG. 2 comprises one freezing tube insertion tube 2 located at the center and an undisturbed region C on the outer periphery thereof.
(Refer to FIG. 3 and FIG. 4. Incidentally, the outer peripheral portion D of the hole excavated for inserting the freezing pipe is presumed to be the disturbing area.) A total of four holes arranged in four directions at right angles to the presumed range. The core tube insertion tube 3 and the core tube insertion tube 3 are combined in a vertically parallel arrangement. When the outer diameter of the freezing tube is 73 mm, the inner diameter of the freezing tube insertion tube 2 is about 110 mm. When a soil sample with an outer diameter of φ300 mm is collected with a double core tube, the inner diameter of the core tube insertion tube 3 is φ4.
The size is about 00 mm. Steel tubes are usually used for the freezing tube insertion tube 2 and the core tube insertion tube 3. However, in order to achieve the purpose of preventing the limited freezing of the ground and unnecessary freezing of groundwater around the guide pipe, each of the above pipes is preferably made of a heat insulating material having low conductivity of cold heat, for example, a vinyl chloride pipe, The use of concrete pipes, porcelain pipes, etc. is also preferable. The height H of the guide tube 1, that is, the lengths of the freezing tube insertion tube 2 and the core tube insertion tube 3 achieves the purpose of limiting and freezing the sampling range (for example, about 5 m to 15 m underground) of the soil sample. According to the above example, it is about 4 m. As a natural condition for performing frozen sampling of the ground, the height H of the guide pipe 1 is also set to a size that reaches the groundwater level in the ground. In the extreme, even when collecting soil data 60m deep underground, it is used in such a size by the extension method.

The above-mentioned combination of the freezing tube insertion tube 2 and the core tube insertion tube 3 fixes the above-mentioned arrangement relationship,
The upper and lower ends are integrated with the disc-shaped positioning plates 4 and 4 having a diameter of about 2 m by means such as welding. Then, five temperature sensors (thermocouples) are arranged at intervals of about 20 cm in the radial direction of the lower bottom surface of the lower positioning plate 4.
5 are installed in series, and each temperature sensor 5 is covered and protected by a protection tube 6. Further, in the case of the illustrated example, four core tube insertion tubes 3 are provided on the lower surface side of the lower positioning plate 4.
A cooling pipe 7 is installed so as to surround the outer periphery of the cooling pipe, and the inlets / outlets 7a and 7b of the cooling pipe are erected vertically up to a height reaching the ground while penetrating the upper and lower positioning plates 4 and 4. (Figure 1). The inlet / outlet ports 7a and 7b are connected to supply / exhaust pipes in a refrigerant circulating device.

The guide tube 1 having the above-mentioned structure is preliminarily provided with a diameter of 2.5 m on the in-situ ground where a soil sample is to be collected,
A hole 9 having a depth of about 4 m is vertically excavated, the guide tube 1 is inserted into the hole 9, and the guide tube 1 is installed in a vertical posture while standing on the flattened bottom of the excavation hole. The excavation of the hole 9 is performed by previously constructing a mountain clasp 11 such as a sheet pile. However, before the work of inserting the guide pipe 1, mortar or the like is filled in the mouth of each core tube insertion pipe 3 and, in some cases, the lower end portion of the freezing pipe insertion pipe 2, and groundwater or the like exuding into the hole 9 is removed. A filling plug 8 is provided so as to prevent the inflow. This is because if the groundwater or the like flowing into the core tube insertion pipe freezes, it will hinder the insertion work of the core tube. In addition, the grout 10 is filled around the guide tube 1 inserted into the hole 9 to stabilize and fix the installation state.

When the guide tube 1 is installed as shown in FIG. 1 in the above-described manner, next, the boring workbench 12 is installed at a position directly above the guide tube 1 in the manner shown in FIG. Further, on this boring workbench 12, a boring machine 13
Installed, and a water spraying type boring rod (not shown) penetrates through the freezing tube insertion tube 2 and is driven by the boring machine 13 to form a hole for inserting the freezing tube at the bottom of the soil sampling area (preceding example). Excavate to about 15m underground). Then, the freezing tube 14 is inserted into the hole through the freezing tube insertion tube 2 of the guide tube 1 and installed as shown in FIG. Thereafter, as shown in FIG. 3, a refrigerant such as liquid nitrogen is circulated through the freezing pipe 14 to proceed with the freezing process of the ground in the soil sampling range. After the freezing process has progressed to a certain extent, the refrigerant is circulated through the cooling pipe 7 described above, and the freezing base plate of the guide pipe 1 and the lower outer ground are also frozen. In this way, the freezing of the ground area B, which is not easily frozen as shown in FIG. 3, rapidly progresses due to the overlapping effect of the cooling heat from above and below, which is efficient. However, in order to make the guide function of the guide tube 1 sufficiently work, when the guide tube 1 is installed in the hole 9, the refrigerant is immediately supplied to the cooling pipe 7 to freeze the direct ground plate of the guide pipe 1 and the lower peripheral ground. In some cases, it may be preferable to proceed with the guide tube 1 being firmly fixed to the ground by the fixing action by freezing and then proceeding with the work of excavating the hole for inserting the freezing tube and inserting and installing the freezing tube. Whichever procedure is adopted, the guide pipe 1 is watertightly fixed (frozen) and integrated with the frozen direct ground plate and the lower peripheral ground. Therefore, the conventional peeling never occurs. Therefore, when the soil sample 16 is collected by the double core tube 15 driven by the boring machine 13 as shown in FIG. 4, the core tube insertion tube 3 and the drilled hole 17 form a continuous water channel, and the cooling water is dissipated. Does not occur. In the freezing process of the surrounding ground through the freezing pipe 14, when the groundwater level is low, water is preliminarily supplied from the ground to ensure at least a saturated state and the work is performed as usual.

After all the work of collecting the soil sample is completed as described above, the work of collecting and removing the equipment is started. As the preparation, first, a defrosting fluid such as hot water is circulated in the freezing pipe 14 and the cooling pipe 7 to fix the frozen pipe 14 and the frozen soil around the freezing pipe 14 and the guide pipe 1 and immediately below the freezing pipe and the outer periphery of the lower part. Melt (thaw) the adhered state with soil. After that, the freezing pipe 14 and the guide pipe 1 are pulled out from the ground and collected.

At this time, if the cooling pipe 7 attached to the guide pipe 1 is utilized as described above, the freezing or thawing treatment of the ground immediately below the guide pipe and the lower part outer peripheral ground can be artificially and swiftly proceeded. This greatly contributes to shortening the required time and shortening the construction period. As a means for further expanding the function of such a cooling pipe 7, although not shown in the drawing, it is not limited to the structure in which only one is provided on the outer periphery of the lower surface of the guide pipe 1 as shown in FIG. Is not limited to the structure in which a plurality of inward spirals are wound in a manner to avoid the position of, or the cooling pipe 7 is arranged only on the lower side of the lower positioning plate 4, and also on the upper side of the positioning plate 4. Depending on the case, it can be installed and used in a configuration in which a plurality of spirals are wound in the lower region as shown in FIG.

However, the means for preventing the guide tube 1 from peeling off from the ground and fixing the guide tube to the ground by a freezing process, or conversely, the means for releasing the fixed state by thawing, are attached to the above-mentioned guide tube. The method is not limited to the method of using the cooling pipe 7. After inserting the guide tube 1 into the hole 9,
Perform a freezing process by inserting a cooling pipe into the inside and freezing, or by spraying liquid nitrogen from the ground, or by putting dry ice, brine, etc. at the bottom of the hole to freeze, and then add hot water. The same effect can be obtained by the method of performing the thawing process.

[0024]

According to the in-situ ground freezing sampling method and the guide pipe of the present invention, the installed and fixed state of the guide pipe is established by the freezing treatment of the ground just below the guide pipe and the lower part outer circumference, and is used as a guide. The above function can be fully worked and the guide pipe and the ground can be prevented from being separated from each other. In particular, the cooling water can be prevented from escaping at the time of coring, and the circulation can be smoothly performed. Also, after the soil sample collection work is completed, the necessary part of the ground can be thawed easily, and the freezing pipes and guide pipes can be pulled out and recovered easily, so economical in-situ ground freezing is possible. Sampling can be done in a short period of time.

[Brief description of the drawings]

FIG. 1 is an elevational view showing a usage state of a guide tube.

FIG. 2 is a bottom view of the guide tube.

FIG. 3 is a cross-sectional view showing a state in which ground is frozen by a freezing pipe.

FIG. 4 is a cross-sectional view showing a situation of soil sampling with a core tube.

[Explanation of symbols]

 c Undisturbed area 16 Soil sample 1 Guide tube 14 Freezing tube 15 Double core tube 7 Cooling tube 2 Freezing tube insertion tube 3 Core tube insertion tube 4 Positioning plate 7a Inlet 7b Outlet 5 Temperature sensor

Claims (5)

[Claims] 1. In an in-situ sampling method in which the in-situ ground is frozen and frozen soil in an undisturbed area is sampled as a soil sample by a coring method, a guide pipe that reaches a position just above the limited freezing of the in-situ ground is installed. Then, the freezing tube is inserted and installed through the guide tube, and the refrigerant is circulated through the freezing tube to advance the freezing of the ground,
In addition, freezing the ground immediately below the guide pipe and the lower peripheral ground of the guide pipe, inserting a core tube through the guide pipe to collect a frozen soil sample in the undisturbed region, and collecting a soil sample After finishing the work, thawing fluid is circulated to the freezing pipe to thaw the frozen ground, and further to the ground immediately below the guide pipe and the lower peripheral ground of the guide pipe,
Thereafter, the freezing pipe and the guide pipe are extracted from the ground and collected, respectively, and an in-situ ground freezing sampling method is characterized. 2. In the in-situ sampling method in which the in-situ ground is frozen and the frozen soil in the undisturbed area is sampled as a soil sample by the coring method, a guide pipe that reaches a position directly above the limited freezing of the in-situ ground is installed. Then, the freezing tube is inserted and installed through the guide tube, and the refrigerant is circulated through the freezing tube to advance the freezing of the ground,
In addition, freezing the ground immediately below the guide pipe and the lower peripheral ground of the guide pipe by circulating a refrigerant in a cooling pipe previously installed in the lower part of the guide pipe, and inserting a core tube through the guide pipe to undisturb The step of collecting the frozen soil in the area as a soil sample, and after completing the operation of collecting the soil sample, thaw the frozen ground by circulating the thaw fluid to the freezing pipe and the cooling pipe, and then the freezing pipe and the guide pipe. In-situ ground freezing sampling method, each of which is characterized by pulling out and collecting the soil from the ground. 3. The freezing of the ground according to claim 1 or 2, first of all, freezing the substratum of the guide pipe and the lower peripheral ground, and then inserting and installing the freezing pipe through the guide pipe. An in-situ ground freezing sampling method characterized by promoting freezing of the surrounding ground. 4. A freezing tube insertion tube comprising at least one freezing tube insertion tube and a plurality of core tube insertion tubes, each having a length to reach a position just above the limited freezing of the in-situ ground. Located in the central portion, a plurality of core tube insertion tubes are arranged in the undisturbed region on the outer periphery of the freezing tube insertion tube, each tube is arranged in parallel, and the upper and lower parts are fixed by positioning plates. A guide pipe for in-situ ground freezing sampling, characterized in that a cooling pipe is arranged at the inlet and outlet of the cooling pipe is raised upward. 5. A guide pipe for in-situ ground freezing sampling, characterized in that a plurality of temperature sensors are installed in a radial direction of a bottom surface portion of the guide pipe according to claim 4.