JP7544421B1 - Method for installing a liquefaction monitoring device for monitoring the degree of soil liquefaction - Google Patents

Abstract

A method for installing a liquefaction monitoring device to accurately monitor the degree of soil liquefaction is provided.
[Solution] The method includes the steps of excavating the area to be monitored to obtain refill soil, lowering an outer tube 200 into the area, pushing and positioning a soil sampler 300 into the outer tube 200 and storing soil in the soil sampler 300, removing the soil sampler 300 to form a borehole, freezing and storing the soil sampler 300 to obtain a frozen soil column, placing a liquefaction monitoring device at the bottom of the borehole, removing the frozen soil column from the soil sampler 300 and returning it to the borehole in accordance with the position of the soil sampler 300 in the borehole, filling the space between the frozen soil column and the outer tube 200 with refill soil, and pulling up the outer tube 200.
[Selected Figure] Figure 4C

Description

The present invention relates to a method for installing a soil liquefaction monitoring device that uses a freezing method to backfill soil samples excavated at the site, thereby placing the liquefaction monitoring device at a relatively constant depth and maintaining the pile-up order of the soil above it, thereby enabling accurate detection of the state of soil liquefaction.

In the conventional method of installing the above-mentioned liquefaction monitoring device, the soil in the area to be detected is excavated, a water pressure gauge is installed in the borehole, and then clean soil (e.g., 7 rin gravel) is backfilled. This is because, in order to detect the condition of the subsoil, it may be necessary to excavate to a depth of 50 meters, in which case there is a possibility of crossing a clay layer and a calcium carbonate sand layer, and since the soil deposition order of each layer differs depending on the depth, it is not possible to backfill the excavated soil in the borehole in the original position. However, since the backfilled soil is different from the original excavated soil, the amount of excess pore water pressure generated by the earthquake, measured by the water pressure gauge, differs from the actual amount of excess pore water pressure generated in the original ground, making it difficult to accurately monitor soil liquefaction.

The present invention was made in consideration of the above problems, and its purpose is to provide a method for installing a liquefaction monitoring device so that the degree of soil liquefaction can be accurately monitored.

In order to achieve the above object, the present invention provides a method for installing a liquefaction monitoring device for monitoring the degree of liquefaction of subsoil in an area, the method comprising the steps of:
excavating the area to obtain refill soil;
lowering an outer tube into the region;
pushing at least one soil sampler into the outer tube to collect soil within the soil sampler;
removing said at least one sampler to form a borehole;
freezing and storing the soil sampler to obtain a plurality of frozen soil columns;
positioning a liquefaction monitoring device at the bottom of the borehole;
removing the frozen soil column from the sampler and returning the frozen soil column to the borehole according to the position of the sampler in the borehole;
filling the replenishment soil between the frozen soil column and the outer tube;
The method is characterized in that it includes a step of pulling up the outer tube.

In the method of installing a liquefaction monitoring device for monitoring the degree of liquefaction of subsoil in a certain area according to the present invention, the outer tube is a hollow tube.

In the method of installing a liquefaction monitoring device for monitoring the degree of liquefaction of subsoil in a certain area according to the present invention, the at least one soil sampler and the liquefaction monitoring device are pushed downward into the borehole by a push rod.

The present invention relates to a method for installing a liquefaction monitoring device for monitoring the degree of liquefaction of subsoil in a certain area, comprising the steps of:
The at least one sampler has an upper lid, two side walls, and a lower lid;
the top cover has a coupling device for coupling with the push rod;
The two side walls are engaged with the upper cover and the lower cover,
The lower cover has an opening through which soil enters the at least one soil sampler when the soil sampler is pushed down by the push rod.

The present invention relates to a method for installing a liquefaction monitoring device for monitoring the degree of liquefaction of subsoil in a certain area, comprising the steps of:
The liquefaction monitoring device comprises:
an upper portion having a connection hole for connection with the push rod;
a first hole portion and a second hole portion penetrating the upper portion and positioned on both sides of the connecting hole;
An outer wall defining a storage space together with the upper portion;
An earth pressure gauge and a water pressure gauge disposed in the accommodation space,
The monitoring signal lines of the earth pressure gauge and the water pressure gauge are connected to a data extractor in the ground through a first opening;
The outer wall of the liquefaction monitoring device is intended to sink into soil.

In the method of installing a liquefaction monitoring device for monitoring the degree of liquefaction of subsoil in an area according to the present invention, the step of disposing the liquefaction monitoring device at the bottom of the borehole further includes the following steps:
A signal line protection tube is connected to the first hole portion of the liquefaction monitoring device, and before the monitoring device is lowered, the signal line is connected to the earth pressure gauge and water pressure gauge in the liquefaction monitoring device and the first hole portion is sealed with a waterproof material.
An inlet/outlet pipe having a valve and allowing air and water to pass through is connected to the second hole.
Here, after the liquefaction monitoring device is positioned at the bottom of the borehole by the push rod, the valve of the inlet/outlet pipe is opened to allow water and air to flow into the inlet/outlet pipe to fill the inside of the liquefaction monitoring device with water and air, and then the push rod is used to push the liquefaction monitoring device into the subsoil in the area to be monitored to allow excess water and air to flow out of the inlet/outlet pipe, and then the valve is closed to attach the soil to the liquefaction monitoring device.

1 is a schematic diagram showing the appearance of a liquefaction monitoring device applied to a method for installing a liquefaction monitoring device according to the present invention. FIG. FIG. 2 is a schematic diagram showing the inside of the liquefaction monitoring device of the present invention. FIG. 2 is a schematic diagram of an outer tube according to the present invention. FIG. 2 is a schematic diagram of a pottery sampler according to the present invention. 4 is a schematic diagram of a step of removing refill soil in the method for installing a liquefaction monitoring device according to the present invention. FIG. 4 is a schematic diagram of a step of sinking the outer tube in the installation method of the liquefaction monitoring device of the present invention. FIG. 2 is a schematic diagram of a step of sinking a soil sampler in the method of installing a liquefaction monitoring device according to the present invention. FIG. 4 is a schematic diagram of a step of sinking a liquefaction monitoring device in the installation method of the liquefaction monitoring device of the present invention. FIG. 4 is a schematic diagram of the step of returning frozen soil in the installation method of the liquefaction monitoring device of the present invention. FIG.

1A is a schematic diagram showing an example of a liquefaction monitoring device 100 applied to the installation method according to the present invention. The liquefaction monitoring device 100 includes an upper portion 101 and an outer wall 102. The upper portion 101 has a quick-connect type connection hole 103, which is for connecting with a push rod 400 (not shown) for pushing the liquefaction monitoring device 100. The upper portion 101 also has a hole 105 and a hole 107 that penetrate the upper portion 101 and are located on both sides of the connection hole 103. FIG. 1B is a schematic diagram showing the inside of the liquefaction monitoring device 100. As shown in FIG. 1B, the upper portion 101 and the outer wall 102 define an accommodation space that can accommodate an earth pressure gauge 111 and a water pressure gauge 113. The earth pressure gauge 111 and the water pressure gauge 113 are arranged, for example, inside the upper portion 101 or inside the outer wall 102. The liquefaction monitoring device 100 has a structure without a bottom so that the outer wall 102 can be sunk into the soil. Note that multiple earth pressure gauges or water pressure gauges may be installed depending on the measurement method or design conditions.

2 is a schematic diagram of the outer tube 200 in the present invention. The outer tube 200 is hollow and may have an outer diameter D _o of 10 to 13 cm, a thickness t _o of 0.5 to 0.7 cm, and an inner diameter D _i of 8.6 to 12 cm. The outer tube 200 is for defining the position of the earthen sampler 300 to be lowered.

FIG. 3 is a schematic diagram of a soil sampler 300 in the present invention. The material of the soil sampler 300 may be non-stainless steel. The soil sampler 300 has an upper cover 301, two side walls 305, 307, and a lower cover 303. The upper cover 301 has a connection device (not shown, but for example, one having a quick release mechanism) for connecting with the push rod 400. The two side walls 305, 307 are engaged with the upper cover 301 and the lower cover 303. The lower cover 303 has an opening. When the soil sampler 300 pushed by the push rod 400 sinks into the soil, the soil enters the soil sampler 300 through the opening of the lower cover 303. The outer diameter or external dimension of the soil sampler 300 may be configured to be smaller than the outer diameter D _o of the outer tube 200. The outer diameter or external dimensions of the sampler 300 may be configured to be larger than the dimensions of the liquefaction monitoring device 100 (e.g., the outer diameter of the outer wall 102) so that the liquefaction monitoring device 100 can be accommodated in the borehole formed by the sampler 300. The sampler 300 may be configured to have only one side wall, or to have three or more side walls that are combined with each other, depending on the needs of the user.

The following describes how to install the liquefaction monitoring device according to the present invention.

First, as shown in FIG. 4A, excavation is performed in an area adjacent to the installation location of the liquefaction monitoring device 100, and the soil removed by the excavation is set aside as make-up soil 500 for the installation hole of the soil liquefaction monitoring device 100. The final location where the make-up soil 500 is buried may not correspond to the original depth position of the make-up soil 500 before excavation, but the amount of make-up soil 500 required is much less than the amount of soil obtained by the soil sampler 300 in the subsequent step, so it does not affect the measurement results of the earth pressure gauge 111 and the water pressure gauge 113 in the present invention.

Next, the outer tube 200 is lowered into the soil as shown in FIG. 4B.

Next, as shown in FIG. 4C, the soil sampler 300 connected to the push rod 400 via the upper cover 301 is lowered into the soil by pushing the push rod 400 with a hydraulic reaction frame (or machinery such as a truck). At this time, the soil that has entered the soil sampler 300 is held in the soil sampler 300 by the frictional force between the soil sampler 300 and the wall. After that, the soil sampler 300 is pulled up by the push rod 400 to separate the soil sampler 300 from the push rod 400, and then the soil sampler 300 is frozen. This step is repeated. The multiple soil samples 300 to be frozen can be marked to indicate their corresponding positions, for example, the first soil sampler 300 removed can be marked with number 1 to indicate that it is the topmost position, and the second soil sampler 300 removed can be marked with number 2. By freezing, the water and soil are combined and maintained in their original pile order and state. In order to shorten the operation time, two (or more) soil samples 300 may be placed at the same time and the two samples 300 may be removed at the same time. In this case, the samples 300 may be configured so that the upper cover of one sampler 300 and the lower cover of the other sampler 300 can be connected via a quick release mechanism. This makes it possible to push the two samples 300 at the same time using the push rod 400. In addition, in the present invention, if the outer tube 200 is configured larger, it becomes possible to accommodate one or more samples 300 at a time within the area of the borehole defined by the outer tube 200. The size of the outer tube 200 can be set according to the user's measurement needs, etc.

4D, a signal line protection tube 701 for accommodating the earth pressure gauge signal line 112 and the water pressure gauge signal line 114 is connected to the first hole 105 of the liquefaction monitoring device 100, and the signal line connection is completed before the installation of the monitoring device, and the first hole 105 is sealed with a waterproof material. In addition, an inlet/outlet pipe 703 is connected to the second hole 107 of the liquefaction monitoring device 100. The inlet/outlet pipe 703 is provided with a valve that controls whether or not fluid can pass through it. Then, after the liquefaction monitoring device 100 is placed at the bottom of the borehole using the push rod 400, the valve of the inlet/outlet pipe 703 is opened, and water and air are poured into the inlet/outlet pipe 703 to fill the liquefaction monitoring device 100 with water and air. Next, the liquefaction monitoring device is pushed into the subsoil of the area to be monitored by the push rod 400, and excess water and air are discharged from the inlet/outlet pipe 703. After that, the valve is closed, and the liquefaction monitoring device 100 is maintained in a generally constant position because it is attached to the soil by external pressure. The signal line protection tube 701 is for housing and protecting the earth pressure gauge signal line 112 and the water pressure gauge signal line 114.

Next, as shown in FIG. 4E, the frozen soil columns in the soil sampler 300 are removed and sequentially returned to their original positions in the borehole, and the gap between the frozen soil columns and the borehole is filled with the make-up soil 500 set aside in the previous step, after which the outer tube 200 is lifted up. This completes all steps.

Although the present invention has been described with reference to the above embodiments, the present invention is not limited to these disclosed embodiments, and any equivalents that are modified and altered by a person skilled in the art without departing from the technical spirit of the present invention are included in the technical spirit of the present invention. Therefore, the scope of the present invention is defined in the appended claims.

REFERENCE SIGNS LIST 100 Liquefaction monitoring device 101 Upper part 102 Outer wall 103 Connecting hole 105, 107 Hole part 111 Earth pressure gauge 112 Earth pressure gauge signal line 113 Water pressure gauge 114 Water pressure gauge signal line 200 Outer tube 300 Soil sampler 301 Upper cover 303 Lower cover 305, 307 Side wall 400 Push rod 500 Refill soil 701 Signal line protection tube 703 Inlet/outlet pipe

Claims (6)

A method for installing a liquefaction monitoring device for monitoring the degree of liquefaction of subsoil in an area, comprising:
excavating the area to obtain refill soil;
lowering an outer tube into the region;
Pushing and positioning at least one soil sampler into the outer tube and allowing soil to be collected within the soil sampler;
removing said at least one sampler to form a borehole;
freezing and storing the soil sampler to obtain a plurality of frozen soil columns;
positioning a liquefaction monitoring device at the bottom of the borehole;
removing the frozen soil column from the sampler and returning the frozen soil column to the borehole according to the position of the sampler in the borehole;
filling the replenishment soil between the frozen soil column and the outer tube;
and raising the outer tube. The method of claim 1, wherein the outer tube is a hollow tube. The method of claim 1, wherein the at least one sampler and the liquefaction monitoring device are positioned downwardly within the outer tube by a push rod. The at least one sampler has an upper lid, at least one sidewall, and a lower lid;
the top cover has a coupling device for coupling with the push rod;
the at least one side wall is engaged with the top lid and the bottom lid;
4. The method of claim 3, wherein the lower cover has an opening through which soil enters the at least one sampler when the sampler is pushed down by the push rod. The liquefaction monitoring device comprises:
an upper portion having a connection hole for connection with the push rod;
A first hole and a second hole penetrating the upper portion;
An outer wall defining a storage space together with the upper portion;
an earth pressure gauge and a water pressure gauge disposed in the accommodation space;
The method of claim 3 , wherein the exterior wall of the liquefaction monitoring device is for submersion into soil. locating the liquefaction monitoring device at the bottom of the borehole,
a step of connecting a signal line protection tube that houses a signal line to the first hole portion of the liquefaction monitoring device and sealing the first hole portion in a watertight state;
and connecting an inlet/outlet pipe having a valve to the second hole.
6. The method of claim 5, further comprising: positioning the liquefaction monitoring device at the bottom of the borehole by the push rod; opening the valve of the inlet/outlet pipe; allowing water and air to flow into the inlet/outlet pipe to fill the inside of the liquefaction monitoring device with water and air; and then pushing the liquefaction monitoring device into the subsoil of the area by the push rod to allow excess water and air to flow out of the inlet/outlet pipe; closing the valve; and attaching soil to the liquefaction monitoring device.

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