JPH03286093A - Screw pipe type sample taking-out method in frozen ground - Google Patents

Abstract

PURPOSE:To take out a high quality sample without disturbing the granular ground by carrying out drilling to a position for taking out the frozen soil sample, press-fitting a freezing pipe through revolution from the hole bottom, and taking out the frozen soil, together with the freezing pipe. CONSTITUTION:After drilling is carried out to a prescribed depth by revolving an excavating pit 11, a freezing pipe 16, freezing and connecting pipe 6, guide plate 13, ground temperature meter 12, etc., are assembled and inserted into the hole. Then, the freezing pipe 16 is press-fitted through revolution until the guide plate 13 reaches a hole bottom 14, and a low temperature fluid pouring pipe 20 is inserted into the freezing pipe 16, and the upper part is covered by a heat shielding agent 21 for low temperature fluid, and the upper edge part is connected with a low temperature fluid pouring adjusting valve 19. Then, an excavating pipe 10 is pulled up, and the temperature of each part and the freezing thermal source 18 quantity are measured by using a measurement controller 23, and freezing is started. When a sample taking-out temperature is realized, the excavating pipe 10 is revolved to excavate the frozen soil 24 to a cylindrical form, and a frozen soil pile is pulled up to the ground surface, and the taken-out frozen soil is pulled out.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a method for obtaining high-quality samples without disturbing granular ground such as sandy ground in order to obtain ground information such as mechanical properties of the ground through laboratory tests. It concerns the method and equipment for collecting the sample.

[Conventional technology]

Conventionally, the following methods have been used to collect samples by freezing the ground in deep layers so as not to disturb it.

First, methods for collecting undisturbed samples from granular ground such as sand can be roughly divided into two methods: one is to collect samples after the ground has been frozen, and the other is to collect samples from natural ground.Currently, the former method is preferred. It is a well-known fact that high-quality samples can be obtained using this method.

In order to freeze the ground, a freezing pipe is installed at a predetermined depth, a cryogenic fluid injection pipe is inserted into the pipe, and the cryogenic fluid that is the freezing heat source is circulated to freeze the ground to a predetermined size and shape. is taken.

In addition, the method of installing a freezing tube at a predetermined depth is to drill a hole to a specified depth while circulating muddy water to prevent the hole wall from collapsing, and then insert a freezing tube with a bottom cover into the hole. In addition, there is a method of inserting a cryogenic fluid injection pipe into this hole to near the bottom of the frozen pipe, and a method of inserting a frozen outer pipe such as a steel pipe into the ground to a predetermined depth while digging inside to prevent the collapse of the hole wall. There is a method of inserting a freezing tube and a cryogenic fluid injection tube.

In addition, soil temperature measurement is used to control the creation and management of frozen soil under predetermined conditions.The method for this is to drill a soil temperature measurement hole at one or several locations away from the frozen pipe, and insert a geothermometer into the hole at a depth. The method of installing the frozen pipe is to drill a hole deeper than the specified depth, install several geothermometers below the frozen pipe, and drill the hole from the bottom of the frozen pipe to the same depth as the radius of the frozen soil. There is a method that assumes that it is frozen in a hemispherical shape.

Furthermore, methods for collecting frozen soil samples include the method of pulling out the cylindrical frozen soil created using a single frozen pipe, and the method of using a digging pipe with a cutting bit attached to the tip to concentrically surround the cylindrical frozen soil. The overcoring method involves cutting the frozen soil to reduce the pulling resistance, and then collecting frozen soil samples together with the frozen tube, or using a sampling device with a radius sufficiently smaller than the radius of the frozen soil to collect one or several frozen soil samples around the frozen tube. There is a coring method in which frozen soil samples are collected while drilling holes at certain locations. Other methods include coring, which involves installing multiple frozen pipes in the ground to create a large frozen soil core, and then collecting frozen soil samples by drilling holes between each frozen pipe.

As described above, the frozen soil samples collected from the original site are shaped into the sample end face, set in various testing devices, thawed, and then subjected to prescribed tests to obtain information on the strength and deformation of the original ground in an undisturbed state. ing.

[Problem to be solved by the invention]

In the above-mentioned method of freezing the deep ground and collecting samples without disturbing it, an important issue is reducing the amount of heat source consumed for freezing the ground. The most efficient way to deal with this is to create frozen soil with the minimum necessary shape and size and select a sample collection method in order to collect the required number of test samples of a given shape and size from a given depth. That's true.

Next, the problems with the freezing tube itself and the issues involved in installing it are firstly the need for a material that has good heat transfer efficiency in order to freeze the surrounding ground, and for it to have an efficient shape. In addition, it is necessary to collect as many samples as possible for the size of the constructed frozen soil, and for this purpose, the cross-sectional dimension of the frozen pipe must be as small as possible, and the surrounding ground must be minimally disturbed when installed in the ground.

Regarding the installation of frozen pipes, the most commonly used method is to drill a hole and insert the frozen pipe while circulating muddy water, but this method does not allow for damage to the area where the ground is disturbed, which can be fatal due to collapse of the hole wall. This is a problem because there is a concern that it will expand, and that disturbance of the ground will definitely occur due to the opening of underground stress due to drilling. In order to deal with these ground disturbance factors, in collapsible ground, a method is used in which a frozen outer pipe is press-fitted while digging, and a frozen pipe with a bottom cover is inserted into this. Problems include ground disturbance due to frictional resistance between the pipe and the ground, the double-walled method requiring larger hole diameters, and complicated construction methods.

Taking this into account, even if there is no collapse of the pore wall, the test sample cannot be sampled from the outside of the cryotube or cryotube at least within a range equal to or larger than the pipe diameter. Are known. Therefore, a method is desired to minimize the disturbance of the ground caused by the installation of frozen pipes.

Furthermore, as an issue in management of frozen soil creation, it is necessary to make sure that the minimum amount of frozen soil necessary to collect samples of a given size at a given location and depth has been created, and that the ground temperature is suitable for sample collection. In addition, the consumption of freezing heat sources can be minimized and controlled as planned. On the other hand, among the currently used soil temperature measurement methods for managing frozen soil creation, the method of installing a geothermometer vertically downward from the tip of a frozen pipe is simple in terms of the geothermometer installation work, but The problem is that the radius in the cross section and the radius from the bottom of the frozen pipe in the constructed frozen soil are not the same. On the other hand, the method of drilling a measurement hole near the radius of planned frozen soil and installing a geothermometer inside the hole has problems such as errors due to ground disturbance and hole bending during drilling, and poor work efficiency. .

[Means to solve the problem]

In view of this, the present invention has been developed and found that the most economical and efficient frozen soil creation method and sample collection method is the creation of cylindrical frozen soil using a single freezing tube and overcoring that does not require a special poling device. Based on the recognition that it is necessary to adopt a sample collection method according to the law, and as a result of further consideration, the above problems were resolved.

That is, the method of the present invention involves inserting a freezing pipe into the ground, supplying cryogenic fluid into the pipe to freeze the surrounding ground, and then collecting a frozen soil sample. A hole is drilled, and a freezing tube with spiral blades on the outer periphery is rotatably press-fitted from the bottom of the hole.Then, while measuring the surrounding soil temperature, low-temperature fluid is supplied into the freezing tube to create frozen soil, which is then frozen. The frozen soil sample is collected together with the tube by rotational press-fitting, and it is effective to rotatably press-fit the frozen tube while injecting lubricant into the ground from the lower end of the tube.

The device of the present invention also includes an excavation means for drilling a hole up to the upper part of the frozen soil at the depth to be sampled, a freezing tube provided with spiral blades on the outer periphery and rotated and press-fitted into the ground from the bottom of the excavated hole, and an inside of the frozen soil. This method consists of a means for supplying cryogenic fluid to a freezing tube, which is rotated and press-fitted to create frozen soil by supplying the cryogenic fluid into the freezing tube, which is then rotated and press-fitted to collect frozen soil of a predetermined size. It is effective to provide a guide plate having one or more geothermometers at the upper end of the pipe, or to provide a lubricant injection hole for injecting lubricant into the ground at the lower end of the freezing pipe.

[For production]

The reason why spiral blades are provided on the outer periphery of the cryotube is as follows.
In order to improve the heat transfer efficiency of the low-temperature fluid from the freezing tube to the ground, it is not a simple tube with a bottom cover, but has feather-like protrusions on its outer periphery to act as a heat sink.

Furthermore, in order to ensure that the freezing tube is installed at a predetermined location and depth and to minimize disturbance of the surrounding ground, the freezing tube is equipped with screw-shaped vanes that also serve as a heat sink. In other words, the freezing efficiency of the ground can be improved by using a freezing tube with screw-like blades, and by controlling the rotation speed and penetration amount when press-fitting into the ground, the freezing tube with screw blades can be Since it can be installed while draining the ground, there is no disturbance due to the release of underground stress unlike in conventional drilling methods, and the cause of fatal defects caused by collapse of the hole wall can be eliminated. In addition, by using the lubricant injection method, the frictional resistance with the ground is reduced when the frozen pipe is rotated and press-fitted, so the ground equivalent to the volume of the frozen pipe press-in can be easily discharged above the frozen pipe by the rotation of the screw. can be inserted, making it even more possible to eliminate collapse of the ground around the frozen pipe and reduce the disturbed area. Therefore, according to the present invention, the influence of turbulence caused by friction with the ground, as in the above-mentioned method of press-fitting frozen outer pipes using the hollow method, can be greatly reduced.

The geothermometer attached to the top of the frozen tube makes it possible to check the progress of frozen soil formation. Furthermore, by measuring and controlling the consumption of these geothermometers, the thermometers inside the freezing tubes, and the freezing heat source, it will become easier to improve the efficiency of frozen soil creation and to manage the temperature of circulating mud water, etc. based on the frozen soil temperature at the time of sample collection. .

That is, for example, measurements can be taken using several geothermometers attached to guide plates attached to the top of the freezing tube at different distances from the center of the freezing tube, thermometers attached at several locations inside the freezing tube, and load meters for measuring the consumption of the freezing heat source. By doing this, it becomes possible to check the frozen area and soil temperature distribution while freezing, and to control the efficient consumption of freezing heat sources.

Finally, by cutting the outer periphery of the created columnar frozen soil into a ring shape with a digging pipe and then pulling up the frozen pipe and frozen soil column together, it becomes possible to use most of the frozen sample as a test sample. .

〔Example〕

Next, one embodiment of the present invention will be described.

An example of the configuration of the present invention is shown in FIG. 1, which is a diagram related to a freezing pipe and its installation, and FIG. 2, which is a diagram related to frozen soil creation and sample collection. In Fig. 1, a screw-like blade (15) is attached to the outer periphery of the cryotube (16), and a filter is attached to the tip to prevent clogging when the cryotube (16) is press-fitted into the ground. There is a lubricant injection hole (1) connected to this, and a lubricant injection pipe (7) is led to the ground and connected to the lubricant pressure tank (4). One (7) is shown in the cone at the tip of the freezing tube (16), but it is also possible to install more than one including the tube body, and the lubricant injection tube (7) can also be installed inside the freezing tube (freezing tube). It is also possible to install it in a spiral along the connecting part between the freezing pipe part) and the screw blade (@).

In addition, the upper end of the freezing pipe (+6) is connected to the freezing connecting pipe (6), and a wooden guide plate 03) painted to prevent water absorption is attached to this connecting part, and a geothermometer is attached to the bottom of the guide plate 03). (
As 12), three thermocouples are installed, and a ground temperature measurement cable (8) connected to the thermocouples is led to the ground. This guide plate (+3) may be made of a material other than wood as long as it has a lower thermal conductivity than the ground, and the geothermometer (12) is not limited to a thermocouple, and the geothermometer (12) may be one or more. However, it can be installed if necessary.

Furthermore, the outside of the freezing connecting pipe (6) is covered with a heat insulating material (5) to prevent muddy water (not shown) between it and the hole wall (9) from freezing and to reduce heat loss. A pressure gauge (1), a pressure regulating valve (2), and a pressure source (3) such as compressed gas are connected to the lubricant pressure tank (4). Note that this equipment includes a digging pipe α for drilling, a drilling bit αυ, and a drilling device (not shown).

Next, we will explain the procedure for installing a frozen tube in the sampling ground using this device.

First, the drilling bit aυ and the digging pipe (10) are rotated using a drilling device (not shown) to the upper part of the depth of the frozen ground to be sampled, and muddy water is circulated to prevent the collapse of the hole wall (9). Drill the hole while

Freeze tube (16) after drilling to specified depth, freeze connection tube (6)
, guide plate 03), geothermometer (12), etc. are assembled and inserted into the hole. At this time, the guide plate (+3) automatically positions the tip of the freezing tube 06) at the center of the hole bottom (I4). is positioned. That is, the freezing tube (16) is attached to the center of the guide plate (13), and the guide plate O
) has a shape that allows it to fit loosely into the hole, so when the guide plate (13) is inserted into the hole, the freezing tube (16) will be located at the center of the bottom of the hole.

Next, using a drilling device (not shown), the freezing pipe (16) is rotationally press-fitted through the freezing connecting pipe (6) until the guide plate 63) reaches near the hole bottom 64). During this rotational press-fitting, lubricant is injected into the ground from the tip of the freezing tube (16) to reduce friction, but the pressure regulating valve (2
). By controlling the number of rotations and the amount of penetration, the ground outside the screw (1 shaft) is not disturbed.

Next, the lubricant supply system device is removed, and the configuration shown in FIG. 2 is created. That is, the cryogenic fluid heat insulating agent is inserted into the freezing tube (+6), and the freezing tube (+6) above the cryogenic fluid injection tube (4) is inserted.
The exposed part from 16) is covered with a low temperature fluid heat insulating agent (21), and this coated injection pipe passes through the freezing connection pipe (6) and the upper end is connected to the low temperature fluid injection adjustment valve (19). And this is a freezing heat source! Low temperature fluid is supplied from 18). On the other hand, the soil temperature measurement cable (
8) and the load cell (22) that measures the amount used of the freezing heat source 08) and the cryogenic fluid injection adjustment valve (19) are the measurement and control device (
23). Although liquid nitrogen is generally used as the freezing heat source, a low-temperature fluid produced by a freezing device may also be used. In addition to the ground temperature, the temperature to be measured and controlled can also include the temperature inside the freezing pipe section (not shown) and the freezing connecting pipe (6).

Next, we will explain the procedure for creating frozen soil and collecting samples using this device.

Start the work from the state shown in Fig. 1, connect and install the equipment as shown in Fig. 2, and pull the pipe (1) from the hole bottom 64 to a depth that does not prevent freezing. Next, use the measurement and control device (23) to measure the temperature of each part and the initial value of the amount of freezing heat source (18), and then measure the change over time of the amount of cryogenic fluid injected per unit time and the measurement interval according to the work process. etc., activate the control device and start freezing.

Then, while monitoring the measured soil temperature, frozen soil is created to a predetermined size, and when the frozen soil temperature reaches a temperature suitable for sample collection, the cryogenic fluid injection pipe is pulled up, the soil temperature measurement cable (8), etc. is removed, and the frozen soil is connected. After putting a lid on the top end of the tube (6),
The frozen soil cutting groove (2
5) Make. Next, a hanging device (not shown) is attached to the upper end of the frozen connecting pipe (6), the frozen soil column with its circumference cut off is lifted above the ground, steam is passed into the frozen pipe (16) to reduce the strength of freezing, and then the frozen soil column is reversed. Rotate and remove this. Finally, the collected frozen soil is cut to the size of the test specimen.

Next, an example of sample collection using the above-mentioned apparatus of the present invention will be explained using numerical values in comparison with a conventional example.

According to the present invention, when collecting nine specimens each with a diameter of 5 cm and a height of 10 marks, which are normally used in laboratory tests, from two locations at a depth of 6 m and 12 m from the ground surface of saturated sand ground, according to the present invention,
(2) was made to have a diameter of 23 cm, and a hole was drilled to the top of the sample collection depth to create a freezing tube (16) with a length of 50 ann, an outer diameter of 3.4 cm, a screw outer diameter of 5a [l], and a guide plate with a diameter of 20 ann. Then, a cryotube and other equipment were placed in the hole as shown in Figure 1. The difference from the figure is that drilling debris remains at the bottom of the hole, and the soil removed by rotational press-in of the frozen pipe is discharged to the bottom of the hole. Collection is possible. It was decided that liquid nitrogen would be used as the freezing heat source, and that freezing would start in the evening and would be supplied at a rate of 20 kg per hour. As a result, the next morning, 15 hours later, 300 kg of liquid nitrogen had been consumed and the soil temperature 11 cm from the center had fallen to 15 degrees Celsius. Since the soil temperature is such that problems such as freezing are less likely to occur, we used a digging pipe to cut the edges while circulating mud water cooled to 2°C, and the cutting was completed in 15 minutes. Immediately after that, the frozen soil sample was pulled up and the diameter of the collected frozen soil was 22 mm.
an ~23 on, the length was 65 an, and the test specimen could be sufficiently collected. Following the above-mentioned 6 m depth, the same work as above was carried out for sampling at a depth of 12 m, and all work was completed by noon the next day.

If such a sample is collected using the conventional single-hole freeze-overcoring method, a diameter of 8C can be obtained from the ground to a depth of 125m.
[In order to drill a hole in Step 11, insert a cryotube into the hole, freeze it with liquid nitrogen, and collect frozen soil at a distance of 30cm from the cryotube, it is necessary to create frozen soil with a radius of 40cm or more. Furthermore, compared to the method of the present invention,
Experience has shown that the freezing time will be several times longer and the amount of liquid nitrogen consumed will be 5 to 10 times more necessary.

〔Effect of the invention〕

As described above, according to the present invention, high-quality frozen ground samples can be easily collected without disturbing the ground condition, and furthermore, frozen soil creation and management can be carried out easily and efficiently, and other remarkable effects are achieved.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are both explanatory diagrams showing one embodiment of the present invention. 1-3 Pressure gauge Pressure adjustment valve Pressure source Lubricant Pressure tank Heat shield Freezing connection pipe Lubricant injection pipe Cable for geothermometer Hole wall digging pipe Drilling bit Geothermometer Guide plate Hole bottom screw Vane Freezing pipe Lubricant injection hole Freezing heat source Low temperature Fluid injection control valve Low-temperature fluid injection pipe Thermal insulation material for low-temperature fluid Load cell Measurement and control device Frozen soil Cutting groove Figure 2

Claims (5)

[Claims] (1) In a method of inserting a freezing pipe into the ground, supplying cryogenic fluid into the pipe to freeze the surrounding ground, and then collecting a frozen soil sample, a hole is drilled to the top of the frozen ground position at the depth to be sampled, From the bottom of the hole, a cryotube with spiral blades on the outer periphery is rotatably press-fitted, and then a cryogenic fluid is supplied into the cryotube while measuring the surrounding soil temperature to create frozen soil. A screw pipe method for collecting frozen ground samples. (2) The screw pipe type frozen ground sample collection method according to claim 1, wherein the frozen tube is rotationally press-fitted while injecting lubricant into the ground from the lower end of the frozen tube. (3) An excavation means that drills a hole to the top of the frozen soil at the depth to be sampled, a freezing pipe that is rotated and press-fitted into the ground from the bottom of the drilled hole with spiral blades on the outer periphery, and a freezing pipe that has a low temperature inside it. A screw pipe type ground freezing sample collection device comprising a means for supplying a fluid, which is characterized by supplying a low temperature fluid into a rotationally press-fitted freezing pipe to create frozen soil, and then collecting frozen soil of a predetermined size. . (4) The apparatus according to claim (3), further comprising a guide plate having one or more geothermometers provided at the upper end of the freezing tube. (5) The device according to claim (3) or (4), wherein a lubricant injection hole for injecting lubricant into the ground is provided at the lower end of the freezing tube.