JP5882159B2 - Simple measurement method for soil saturation - Google Patents

Description

The present invention belongs to the technical field of a method for measuring the degree of saturation of a ground (particularly sand ground, sandy ground) based on an actual measurement value of an undisturbed sample collected by a sampler, and more specifically, by ground freezing sampling. The present invention relates to a simple method for measuring the degree of saturation of a ground, which can measure the degree of saturation with high accuracy by a simple and inexpensive method.

Saturation degree (Sr) of the ground is a ratio of the volume of pore water existing in the gap between the soil particles (Vw / Vv), and serves as an index of strength against liquefaction of the ground.
The method of measuring the degree of saturation of the ground is roughly divided into a method in which a sample that is not disturbed is collected and measured (calculated) by a laboratory test, and a method in which the sample is measured (estimated) without taking a sample.

  As for the former, various methods for collecting undisturbed samples have been disclosed (see, for example, Patent Documents 1 to 3), but since the collected samples are dehydrated more or less when they are pulled to the ground, so-called ground freezing sampling It is difficult to measure the degree of saturation with accuracy other than the method (for example, see Patent Document 4).

  For the latter, the water content ratio is determined from the volumetric water content obtained using a method for measuring the saturation from the change in specific resistance by specific resistance tomography (for example, see Patent Document 5) and a soil moisture meter (for example, see Patent Document 6). A method for measuring the degree of saturation and calculating the degree of saturation, and a method for measuring the P-wave propagation speed correlated with the degree of saturation of the ground by inserting a probe for measuring the P-wave propagation speed into a measurement hole provided in the ground (for example, patent Various methods for obtaining a specific storage coefficient of the ground correlated with the degree of saturation from the relationship between the pumping time and the amount of lowered water level (see, for example, Patent Document 8) are disclosed.

Japanese Patent Laid-Open No. 11-71744 JP 11-101083 A Japanese Patent Laid-Open No. 11-152982 JP-A-9-287378 JP 2009-121066 A JP-A-8-219972 JP 2003-278141 A JP 2003-155735 A

The ground freezing sampling method according to the former is frozen in a state in which the microscopic skeleton structure of the soil particles is maintained in the original position, and therefore can be sampled in a state in which the amount of air in the gap, that is, the degree of saturation is also maintained. Therefore, the degree of saturation can be accurately measured based on the actual measurement value, so that the reliability is high.
However, there is a problem that it is necessary to freeze the sample, and it takes a long time to measure the degree of saturation and the cost is increased. In addition, since the cost per sample increases, there is a problem that it is difficult to apply to the foundation ground of a linear structure such as an existing railway line or pipeline that has been laid long on the ground.
The latter method has a common problem that the number of members is large, and a precise and large-scale device needs to be accurately arranged on the ground around the measurement point, which is very complicated and expensive. In addition, it takes time for measurement and analysis, and there is a problem that the maintenance cost of the apparatus increases. Further, since the apparatus is large, there is a problem that it is difficult to apply to the foundation ground of the linear structure.

  By the way, the former method of collecting undisturbed samples and measuring them by laboratory tests is an inexpensive and highly accurate saturation measurement if a series of operations from sample collection to saturation measurement can be performed while preventing dehydration. It is clear that can be done.

The purpose of the present invention is to quickly and reliably measure the numerical values of the collected samples while maintaining the water retention state maintaining the in-saturation degree without taking out the collected undisturbed samples from the water. It is to provide a simple method for measuring the degree of saturation of the ground, which can measure (calculate) the degree of saturation with high accuracy.

As a means for solving the problems of the background art, the soil saturation simple measurement method according to the invention described in claim 1 is:
After collecting a sample that is not disturbed below the groundwater level at the bottom of the borehole with a sampler provided at the tip of the rod, the sampler is placed in a borehole in an environment filled with muddy water in the borehole in the water-retained state with a water retainer. Picking it up from the
With the water retention device submerged in water in a container on the ground, take out the sampler from the water retention device, disassemble the sampler and take out the tube storing the collected sample;
While the tube is submerged in water, the end surfaces of both ends of the sample are molded, and after measuring the total length of the sample, the tube containing the sample is loaded into a measurement container that is also submerged in water. And sealing,
After taking out the measurement container from the water and measuring the mass of the collected sample, measure the mass and volume of the soil particles of the collected sample, these measured values, and the density of the soil particles measured using the collected sample From the above, the saturation ratio is obtained by calculating the gap ratio and the water content ratio.

The invention described in claim 2 is the ground saturation simple measuring method according to the invention described in claim 1, wherein the water retaining device is longer than the sampler length by at least twice, and a cylinder having a guide bar at the lower end. The cylindrical vinyl is guided by the guide bar, and is lowered so as to surround the sampler from above the rod removed from the boring machine main body to below the sampler, and the upper end of the water retainer The sampler is taken out from the borehole in the water retaining state filled with muddy water by pulling the lower end of the portion to the ground while holding the portion on the ground.

A third aspect of the present invention is the simple method of measuring the degree of saturation of the ground according to the first aspect of the present invention, wherein the water retaining device is a cylinder having a backflow prevention lid at the bottom that is pivotable upward and closed by its own weight. The cylindrical member is lowered from above the rod removed from the boring machine main body, and the backflow prevention lid is rotated upward with the rod so as to communicate with the boring hole. Positioning,
Inject muddy water to the extent that the inside of the tubular member is filled, pull up the sampler to the inside of the tubular member, the backflow prevention cover closes the bottom, and then closes the upper end of the tubular member with the cover material, It is characterized in that it is taken out from the boring hole in a water retaining state filled with muddy water.

The invention according to claim 4 is the ground saturation simple measurement method according to any one of claims 1 to 3, wherein the measurement container is taken out of the water and the mass of the sample collected is measured. A pressurizing device is connected to the measurement container, the volume change due to pressurization is measured to determine the volume of air, and the saturation based on the numerical value of the volume of the air is also determined.

The invention described in claim 5 is the ground saturation simple measurement method according to any one of claims 1 to 3, wherein the sampler has a short length of about 1 m with a tube length shortened by about 50 cm. It is a rotary triple pipe sampler.

According to the simple method for measuring the degree of saturation of the ground according to the present invention, a series of operations from sampling by a sampler to measuring various values necessary for obtaining the degree of saturation cause dehydration without taking out from the water at all. It can be carried out promptly without any water retention.
Therefore, it is possible to obtain an actual measurement value of the collected sample in a state where the saturation at the original position is substantially maintained. Therefore, it is possible to measure (calculate) highly accurate saturation based on the actual measurement value.
Further, by utilizing the numerical value of the volume of air derived using the pressurizing apparatus according to FIG. 5, it is possible to obtain a highly reliable saturation degree at the soil covering pressure at the original position.
The instrument used in the present invention only requires a water retaining device (cylindrical vinyl or cylindrical member) as compared with the conventional sampling method, and the series of operations is about 2/3 shorter. Since it uses a sampler, it is excellent in economic efficiency and workability. Of course, a highly reliable saturation can be measured.
In short, according to the simple method for measuring the degree of saturation of the ground according to the present invention, it is easy to use because it can measure the degree of saturation inexpensively, simply, quickly and reliably, and is excellent in versatility, for example, the foundation ground of a linear structure. Moreover, it can implement suitably.

AE is the schematic which showed in steps the process which takes out a sampler from a boring hole using a water retention tool (cylindrical vinyl), and FG is the state where the water retention tool was submerged in water, It is the schematic which showed the process of taking out a sampler from a water holding tool in steps. In addition, the guide bar (refer code | symbol 6 of FIG. 6) provided in the lower end part of cylindrical vinyl was abbreviate | omitted for convenience of illustration. AC is the schematic which showed in steps the process which takes out the lining tube which stored the extract | collected sample from the sampler in the state which submerged the sampler in water, and performs the end surface shaping | molding of the both ends of this extract | collected sample. It is the schematic which shows the state which loaded the lining tube which stored the extract | collected sample into the measuring container in the state immersed in water, and was sealed. It is the schematic which shows the state which mounted the measuring container taken out from water on the weight measuring device. It is the schematic which shows the state which connected the measurement container taken out from water to the pressurization apparatus (double tube burette). It is detail drawing which showed the said cylindrical vinyl. AE is the schematic which showed in steps the process which takes out a sampler from a boring hole using a water retention tool (bottomed cylindrical member), and FG is the state which submerged the water retention tool in water It is the schematic which showed the process of taking out a sampler from a water retention tool in steps.

Next, an embodiment of a simple method for measuring soil saturation according to the present invention will be described with reference to the drawings.

FIGS. 1-5 has shown in steps the Example of the soil saturation simple measuring method concerning the present invention. First, as shown in FIG. 1A, a ground 10 at a measurement point is excavated to a required depth by a boring machine (not shown), and a sampler 2 provided at the tip of a rod (boring rod) 1 is used to drill the bottom of the boring hole 11. Collect undisturbed sample 3 deep below groundwater level .
The sampling operation of the sample 3 is performed in substantially the same manner as the procedure of the conventional sampling method. However, as the sampler 2, a short rotary triple pipe sampler having a tube length of about 50 cm and a total length of about 1 m is preferably used. The reason for shortening the sampler 2 is to increase the efficiency of a series of operations according to the present invention described later.

Next, as shown in FIG. 1B, the sampler 2 from which the sample 3 has been collected is pulled up to the vicinity of the ground surface while being submerged in the mud 12 in the borehole 11.
Since the ground 10 at the measurement point is often for soft ground, the borehole 11 is often filled with muddy water 12 to the vicinity of the ground surface. If the muddy water 12 is small, the muddy water 12 is suitably added before the sampler 2 is pulled up, and the muddy water 12 is filled to the vicinity of the ground surface.

Next, as shown in FIG. 1C, a cylindrical vinyl (water retaining device) 4 longer than the entire length of the sampler 2 (about 3 times in the illustrated example) is removed from the boring machine body. The sampler 2 is lowered from above to below the sampler 2 so as to surround the sampler 2.
The said cylindrical vinyl 4 is manufactured with the material which has waterproofness, and as shown in FIG. 6, the guide bar 6 is attached to the one end part (lower end part) via the string material 5. As shown in FIG. By guiding with the guide bar 6, the lower end portion of the cylindrical vinyl 4 can be smoothly lowered or raised.

  Next, as shown in FIG. 1D, the upper end of the cylindrical vinyl 4 is held on the ground 10, and the lower end is guided by the guide bar 6 and pulled up onto the ground 10. Thus, the sampler 2 filled with the muddy water 12 can be accommodated in the cylindrical vinyl 4.

  Next, as shown in FIG. 1E, the upper and lower ends of the cylindrical vinyl 4 are appropriately tied with a string member and taken out from the boring hole 11. Thus, the sampler 2 can be transported without causing dehydration in an environment filled with the muddy water 12 in the borehole 11 while keeping the water retained by the tubular vinyl (water retaining device) 4. it can.

  Next, as shown in FIGS. 1F to G, the cylindrical vinyl 4 is immediately submerged in the water in the ground container 7 prepared near the measurement point, and the cylindrical vinyl 4 is submerged in the water. Then, the sampler 2 is taken out from the vinyl 4. The container 7 may be a general water tank or a container having a sufficient capacity to store the tubular vinyl 4 and a waterproof property, such as a waterproof vinyl stretched inside the mold. . The cylindrical vinyl 4 is removed as appropriate.

  Subsequently, as shown in FIG. 2A, the sampler 2 is disassembled in the container 7, and a tube (lining tube) 2 a storing the collected sample 3 is taken out.

Next, as shown in FIGS. 2B to 2C, the both ends of the sample 3 were leveled using an end face molding machine 8 having a cutter on the surface while the lining tube 2a was submerged in water. Thereafter, both ends (upper and lower ends) of the sample 3 are pressed (inserted) with the perforated plate 9 so that the sample 3 does not collapse. Then, the total length of the sample 3 is measured from the insertion depth of the perforated plate 9. In addition, the shavings generated at the time of end face molding are appropriately removed by a suction device (not shown).
This operation can also be performed by moving the container 7 to a vertically long container 7 ′ such as a drum can. In this case, the lining tube 2a in which the sample 3 is stored is wrapped with waterproof vinyl so that dehydration does not occur.

  Next, as shown in FIG. 3, the lining tube 2 a in which the collected sample 3 is stored is filled with water in a measurement container 13 that is also submerged in water so that air does not enter the container 7 (7 ′). Load in state and seal. The measurement vessel 13 is preferably a steel cylindrical vessel that is provided with screwed lids at both ends and is not deformed by pressurization, similar to the triaxial pressure chamber used in the conventional indoor triaxial compression test. Used.

Next, the measurement container 13 is taken out of the water, and as shown in FIG. 4, the measurement container 13 is placed on the weight measuring instrument 14, and the lining tube 2a, the measurement container 13, and the water that have been measured in advance are measured. The weight is subtracted and the mass of the collected sample 3 is measured. When the water in the measurement container 13 becomes cloudy, the degassing water is circulated through an on-off valve 13 a provided in the measurement container 13.
Thereafter, as in the conventional sampling method, the mass and volume of the soil particles of the collected sample 3 are measured. From these measured values and the density of the soil particles measured using the collected sample 3, the gap ratio, And the water content ratio is calculated and the saturation is obtained.
In addition, after measuring the mass of the sample 3 in FIG. 4, a pressurization device (double tube burette) 15 is connected to the measurement container 13 as shown in FIG. The inside of the measurement container 13 is pressurized to measure the volume change amount, the air volume is obtained according to Boyle's law, which is the relationship between the pressure and the air amount, and the saturation is obtained based on the numerical value of the air volume. . Incidentally, reference numeral 16 in FIG. 5 denotes a pressure, 17 denotes a water pressure gauge, 18 denotes a copper tube, and 19 denotes a differential pressure gauge.

Here, the procedure for measuring (calculating) the degree of saturation based on the measured values will be described based on the calculation formula of soil mechanics.
As described in paragraph [0024] above, when the total length of the sample 3 is measured from the insertion depth of the perforated plate 9, the cross-sectional area of the sample 3 can be determined from the inner diameter of the lining tube 2a. Volume (V) is obtained.
As described in the paragraph [0026], when the mass (m) of the sample 3 is measured, the wet density (ρ _t = m / V) of the sample 3 is obtained.
Moreover, the density (ρ _s = m _s / V _s ) of the soil particles is measured using the collected sample 3, and the dry density (ρ _d = m _s ) is determined from the dry mass (m _s ) and the volume (V) of the collected sample 3. / V) is obtained. Further, the gap ratio (e = ρ _s / ρ _d −1) is also obtained.
The water content ratio (w) is obtained by substituting previously known numerical values of ρ _t and ρ _d in the formula w = 100 (ρ _t / ρ _d −1).
Therefore, since the saturation Sr (%) is obtained by the calculation formula of Sr = (w · ρ _s ) / (e · ρ _w ), the water content ratio (w), the soil particle The saturation is obtained by substituting numerical values of density (ρ _s ), gap ratio (e), and water density (ρ _w = 1).

Further, when the pressurizer 15 is connected to the measurement container 13 and the volume of air (V _a ) is obtained, the volume of the entire sample (V) and the volume of soil particles (V _s ) have already been found. Therefore, the volume of water in the gap (V _w = V−V _s −V _a ) and the volume of the soil gap (V _v = V−V _s ) are obtained.
Therefore, the saturation Sr (%) is obtained by substituting the numerical values of V _w and V _v into the calculation formula of (V _w / V _v ) × 100.

According to the simple method for measuring the degree of saturation of the ground according to Example 1, a series of operations from sampling by the sampler 2 to measuring various values necessary for obtaining the degree of saturation such as the mass of the sample 3 is performed. It can be carried out promptly in a water retaining state without causing any dehydration without taking out from the water. Therefore, it is possible to obtain the actual measurement value of the collected sample 3 in a state where the in-saturation degree is substantially maintained. Therefore, it is possible to measure the degree of saturation with high accuracy based on the actual measurement value.
Further, by utilizing the numerical value of the air volume derived using the pressurizing device 15 according to FIG. 5, it is possible to obtain a highly reliable saturation level at the soil covering pressure at the original position.
The instrument used in the present invention is only required to add a cylindrical vinyl (water retaining device) 4 as compared with the conventional sampling method, and the series of operations is performed using a short sampler of about 2/3. Because it does, it is excellent in economic efficiency and workability. Of course, a highly reliable saturation can be measured. In short, according to the simple method for measuring the degree of saturation of the ground according to Example 1, it is easy to use because it can measure the degree of saturation inexpensively, simply, quickly and reliably, and is excellent in versatility, for example, the basis of a linear structure It can also be suitably applied to the ground.

FIGS. 7A to G show different embodiments of the simple method for measuring the degree of saturation of the ground according to the present invention step by step. The second embodiment is mainly different from the first embodiment in the method of pulling out the sampler 2 from the boring hole 11 while keeping the water retaining state filled with muddy water. Subsequent operations are the same as those in Example 1 (refer to FIGS. 2 to 5). Since the configuration of the rod 1, the sampler 2, the sample 3 and the like is the same as that of the first embodiment, the same reference numerals are given and the description thereof is omitted as appropriate.

In other words, saturation simple measurement method of the ground according to the second embodiment, first, as shown in FIG. 7A, and required depth drilling ground 10 measurement points boring machine (not shown), rod (boring rod) The sample 3 that does not disturb the bottom of the bore hole 11 is collected by the sampler 2 attached to the tip of 1. The operations up to this point are exactly the same as in the first embodiment.

Next, as shown in FIG. 7B, the cylindrical member (water retaining device) 20 provided with a backflow prevention lid 20 a that is pivotable upward and is closed by its own weight at the bottom is above the rod 1 from which the boring machine body has been removed. Then, the rod 1 is positioned on the ground 10 so as to communicate with the boring hole 11 while the backflow prevention lid 20a is rotated upward.
In short, the cylindrical member 20 corresponds to a baler type water sampler, and has a cross-sectional shape that is substantially the same as the cross-sectional shape of the boring hole 11 and is sufficiently longer than the entire length of the sampler 2. A shaped bottomed steel pipe is preferably used. A projecting portion (a U-shaped member, a ring-shaped member, etc.) 20 b for easily positioning the tubular member 20 on the ground 10 is provided on the outer peripheral surface below the tubular member 20.

  Next, as shown in FIGS. 7C to 7D, muddy water 12 ′ is injected to fill the inside of the cylindrical member 20, and the sampler 2 is pulled up to the inside of the cylindrical member 20. Specifically, when the lower end of the sampler 2 is pulled up until it passes through the backflow prevention lid 20a, the backflow prevention lid 20a closes the bottom by its own weight. And the said sampler 2 is mounted in the upper surface of the backflow prevention lid | cover 20a which obstruct | occluded the bottom part.

  Next, after confirming that the muddy water 12 ′ is filled up to the top end of the tubular member 20, as shown in FIG. 7E, the rod 1 is removed from the screw joint portion and shortened. The upper end of the member 20 is closed with a lid material 21. Thus, the sampler 2 can be transported without causing dehydration in the water retaining state filled with the muddy water 12 '.

  Next, as shown in FIGS. 7F to G, the cylindrical member 20 is immediately submerged in the water in the container 7 prepared near the measurement point, and the cylindrical member 20 is submerged in the water. The sampler 2 is removed from the shaped member 20. The cylindrical member 20 is removed as appropriate.

  Subsequently, the steps after disassembling the sampler 2 in the container 7 and taking out the lining tube 2a storing the sample 3 and the technique for obtaining the saturation are exactly the same as in the first embodiment (the paragraph above). [0023] to [0028]).

According to the simple method for measuring the degree of saturation of the ground according to Example 2, a series of operations from sampling by the sampler 2 to measuring various values necessary for obtaining the degree of saturation such as the mass of the sample 3 is performed. As in the first embodiment, since it can be carried out quickly without leaving the water and without causing dehydration, the same effects as in the first embodiment can be obtained (see paragraph [0029] above). reference).

  As described above, the first and second embodiments have been described with reference to the drawings. However, the present invention is not limited to the illustrated examples, and variations of design changes and application that are usually performed by those skilled in the art without departing from the technical idea thereof. Note that it includes the range.

1 Rod 2 Sampler 2a Lining tube 3 Collected sample 4 Cylindrical vinyl (water retaining device)
DESCRIPTION OF SYMBOLS 5 String material 6 Guide bar 7 Container 7 'Container 8 End face shaper 9 Perforated board 10 Ground 11 Boring hole 12 Muddy water 12' Muddy water 13 Measuring container 13a On-off valve 14 Weight measuring instrument 15 Pressurizing device (double tube burette)
16 Pressure 17 Water pressure gauge 18 Copper pipe 19 Differential pressure gauge 20 Cylindrical member (water retaining device)
20a Backflow prevention lid 20b Projecting portion 21 Lid

Claims (5)

After collecting a sample that is not disturbed below the groundwater level at the bottom of the borehole with a sampler provided at the tip of the rod, the sampler is placed in a borehole in an environment filled with muddy water in the borehole in the water-retained state with a water retainer. Picking it up from the
With the water retention device submerged in water in a container on the ground, take out the sampler from the water retention device, disassemble the sampler and take out the tube storing the collected sample;
While the tube is submerged in water, the end surfaces of both ends of the sample are molded, and after measuring the total length of the sample, the tube containing the sample is loaded into a measurement container that is also submerged in water. And sealing,
After taking out the measurement container from the water and measuring the mass of the collected sample, measure the mass and volume of the soil particles of the collected sample, these measured values, and the density of the soil particles measured using the collected sample From the above, a simple method for measuring the degree of saturation of the ground, wherein the saturation is calculated by calculating the gap ratio and the water content ratio. The water retainer is longer than the sampler length and is made of cylindrical vinyl having a guide bar at the lower end, and the cylindrical vinyl is removed from the boring machine body by guiding with the guide bar. Further, the sampler is lowered from above the rod to below the sampler so as to surround the sampler, while holding the upper end of the water retainer on the ground and pulling the lower end to the ground, the sampler is filled with muddy water. The ground saturation simple measuring method according to claim 1, wherein the ground saturation is taken out from the boring hole in a state. The water retainer is a cylindrical member provided with a backflow prevention lid that can be rotated upward and closed by its own weight at the bottom, and the cylindrical member is lowered from above the rod removed from the boring machine body, and the rod Positioning the backflow prevention lid on the ground so as to communicate with the boring hole in a state in which the backflow prevention lid is rotated upward.
Inject muddy water to the extent that the inside of the tubular member is filled, pull up the sampler to the inside of the tubular member, the backflow prevention cover closes the bottom, and then closes the upper end of the tubular member with the cover material, The ground saturation simple measuring method according to claim 1, wherein the ground saturation is taken out from the borehole in a water retaining state filled with muddy water. After taking out the measurement container from the water and measuring the mass of the collected sample, a pressure device is connected to the measurement container, the volume change due to the pressure is measured to determine the volume of the air, and the numerical value of the volume of the air The saturation saturation simple measuring method according to any one of claims 1 to 3, wherein a saturation degree based on the ground is also obtained. The ground sample simple measurement method according to any one of claims 1 to 3, wherein the sampler is a short rotary triple pipe sampler having a tube length of about 50 cm and a total length of about 1 m. .

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