JP4970416B2 - Groundwater level measurement method - Google Patents

Description

  The present invention relates to a method for measuring a groundwater level used to determine the state of groundwater as a preliminary survey of the ground.

  In recent years, in order to cope with ground liquefaction caused by earthquakes, it has been demanded to investigate the groundwater level as well as the geological configuration of ground for small buildings such as ordinary houses. However, the boring survey adopted for the normal ground survey has a problem that it is difficult to secure a working space in a residential land for a detached house, etc. in addition to being expensive and costly. In addition, the drilling water level in the borehole survey tends to be upward, so far it has not been regarded as a problem for safety reasons, but there was a concern that it would be forced to bear a large cost for measures to prevent liquefaction originally unnecessary .

  On the other hand, the Swedish sounding test established in the JIS standard has been conducted for the ground survey of detached houses. In this sounding test, as shown in FIG. 6, a solid rod 2 made of iron or stainless steel having a digging screw member (commonly referred to as a screw point) 21 attached to the lower end is vertically projected to the ground G. A clamp 22 and a handle 23 are attached to the upper part of the head. First, a plurality of disk-shaped weights 24 (95 kg for two 10 kg and three 25 kg for a total of 95 kg and a total weight of the loading clamp 5 kg) are mounted on the clamp 22. kg) is placed in sequence, and the sinking of the rod 2 is observed and recorded. When the rod 1 does not sink when all the weights 24 are placed, it is necessary to allow the rod 2 to sink by 25 cm by the scale 2a in increments of 25 cm on the surface of the rod 2 by digging by rotation by the handle 23. Record the number of rotations. Since the rod 2 has a maximum length of 1 m, the rod 2 is dug to a predetermined depth (usually 10 m underground) while adding. The proximal end side of the digging screw member 21 is larger in diameter than the rod 2. Reference numeral 25 in the figure denotes a bottom plate placed on the ground surface at the excavation position.

  In this sounding test, the above recorded data is analyzed to classify the soil into viscous or sandy soil, etc., but the wetness of the surface of the drawn rod 2 after the test is observed, and the position of water wetting The groundwater level WL is also determined from the above. However, in such a method, it is difficult to determine the wet position by the original ground water due to drying of the surface of the drawn rod 2 over time, and conversely, adhesion of water droplets or mud attached to the hole wall, In many cases, it was judged erroneously, and it was not reliable as a method for measuring the groundwater level.

Then, the groundwater level measuring apparatus which enabled it to measure a groundwater level simultaneously with such a Swedish sounding test is proposed (patent documents 1 and 2). This measuring device is provided with through holes (radial lateral holes) at regular intervals in the length direction (usually 25 cm intervals) on the same rod as described above, and these through holes are filled with wettable members such as felt and absorbent cotton. Yes, after performing a Swedish sounding test in the same manner as described above, the rod is pulled out and the water absorption state of the wettable member of each through hole is examined to determine the groundwater level.
JP2000-180243 JP2000-2221030

  However, conventional groundwater level measuring devices that use the Swedish sounding tester described above can only measure roughly and cannot know the exact groundwater level, and in the case of ground with a high water content, Since there is a possibility of being measured further upward, there is a problem that sufficient reliability cannot be obtained in the determination result, and labor and time are required and workability is poor.

  In view of the above circumstances, an object of the present invention is to provide a method capable of accurately and efficiently measuring the groundwater level of the ground with a simple operation and device configuration.

If the means for achieving the above object is shown with reference numerals in the attached drawings, the groundwater level measuring method according to the invention of claim 1 is that the solid rod 2 having the excavating screw member 21 attached to the lower end is provided. After digging vertically into the ground by load loading and rotation by a Swedish sounding tester, the solid rod 2 is extracted to the ground, and then the length of the extraction hole H is determined in the longitudinal direction using a Swedish sounding tester. After rotating the hollow rod 1 provided with the lateral holes 11 passing through the inside and outside at intervals to vertically penetrate the ground G to a predetermined depth, the hollow rod 1 was connected to a measuring instrument 4B having a function of detecting a change in electric resistance. A cylindrical measurement insulated cable 3B composed of two core wires is inserted into the hollow rod 1, and an electrode portion 32a on the end face side and an electrode portion 33 on the peripheral face side of the cylindrical insulation cable 3B. Detects a change in electrical resistance between the electrode portions 32a and 33a when reaching the surface WF of the groundwater that has entered the hollow rod 1, and determines the groundwater level WL from the insertion length of the insulation cable 3B at the time of detection. The electrode portion 32a on the end face side and the electrode portion 33a on the peripheral surface side of the insulated cable are measured so that when the insulated cable 3B is inserted into the hollow rod 1, there is a water drop between the electrode portions 32a and 33a. It is characterized in that it is spaced apart in the axial direction so as to prevent conduction due to adhesion or the like.

The invention of claim 2 is the method of measuring the groundwater level of the claim 1, excavation screw member 12 to the lower end of the hollow rod 1 to penetration is configured to become mounted on the extraction hole H.

Next, effects of the present invention will be described with reference numerals in the drawings. First, in the method for measuring the groundwater level according to the invention of claim 1, when the hollow rod 1 with the horizontal hole 11 is rotated using a Swedish sounding tester and vertically penetrated to the aquifer WZ of the ground G, The groundwater W enters the hollow portion 10 of the hollow rod 1 from the lateral hole 11 below the level WL, and the water surface WF reaches the same level as the groundwater level WL and stabilizes. Therefore, by inserting the measurement insulated cable 3B into the hollow rod 1 in this state, the electrode portion 32a on the end face side and the electrode portion 33a on the peripheral surface side of the measurement insulated cable 3B are connected to the hollow rod 1. since both electrode portions 32a upon reaching the water surface WF of a conductive water inside, the electrical resistance between 33a changes (decreases), this change is detected by instrument 4B, the insulating cable at this time The groundwater level WL can be measured from the insertion length of 3B .

Therefore, according to this measurement method, since the electrode portions 32a and 33a of the insulated cable 3B can be instantaneously grasped to reach the water surface WF in the hollow rod 1, the groundwater level WL can be measured very accurately, Since the hollow rod 1 is isolated from the excavated hole wall, even the ground having a high water content ratio is not affected by the moisture of the hole wall, and thus the measurement result has high reliability. In addition, since it is only necessary to insert the insulated cable 3B from above into the hollow rod 1 for measurement, the operation is extremely simple and the hollow rod 1 is clogged with soil even if the drilled hole wall collapses. Since there is no fear that the insertion of the insulated cable 3B will be hindered, the measurement operation can be completed efficiently and in a short time. Still further, the electrode portion 32a on the end surface side of the insulated cable 3B and the electrode portion 33a on the circumferential surface side are such that when the insulated cable 3B is inserted into the hollow rod 1, both electrode portions 32a and 33a are attached by water droplets or the like. Since it is separated in the axial direction so as to prevent conduction, it is possible to prevent conduction between the electrode portions 32a and 33a due to adhesion of water droplets or the like when inserted into the hollow rod 1. Still further, according to the present invention, the solid rod 2 having the excavation screw member 21 at the lower end is penetrated perpendicularly to the ground G, and then the horizontal hole is inserted into the extraction hole H from which the solid rod 2 is extracted. The hollow rod 1 with 11 is inserted, and the insulation cable 3B is inserted into the hollow rod 1 to measure the groundwater level WL. Therefore, while it is possible to perform excavation drilling with the solid rod 2 without difficulty, the hollow rod 1 used for the measurement of the groundwater level only penetrates into the drilled hole, so that the hollow structure is insufficient for excavation drilling. There is no problem even if it is strong. Further, the excavation process by the solid rod 2 in the previous stage can be used for the Swedish sounding test.

According to the invention of claim 2, since the hollow rod 1 used for the measurement of the groundwater level in the subsequent stage in the two-stage operation is provided with the digging screw member 12 at the lower end, the extraction hole H after drilling by the solid rod 2 in the previous stage Even when the hollow wall 1 is partially blocked by the collapse of the hole wall, the hollow rod 1 in the subsequent stage can be sufficiently deeply penetrated into the extraction hole H simply by being submerged with rotation.

  Hereinafter, an embodiment of a groundwater level measurement method according to the present invention will be specifically described with reference to the drawings. 1 shows the main part of the hollow rod 1 used in the present invention, FIG. 2 shows the measuring method of the first embodiment of the present invention, FIG. 3 shows the measuring method of the second embodiment, and FIG. 4 shows the one-core wire used in the present invention. FIG. 5 shows the distal end side of the measurement insulated cable 3A, and FIG. 5 shows the distal end side of the measurement insulated cable 3B of the two-core wire. 3 and 4, the hollow rod 1 and the solid rod 2 are schematically shown in a simplified manner. The solid rod 2 for Swedish sounding test shown in FIG. 6 is also used in the measurement method of the second embodiment of the present invention.

  As shown in FIG. 1 (A), the hollow rod 1 is provided with lateral holes 11 penetrating in the radial direction at regular intervals d along the length direction, and the inside and outside of the hollow portion 10 are transparent through these lateral holes 11. The excavation screw member 12 is attached to the tip. Further, as shown in FIG. 5B, the horizontal holes 11 are formed so that the directions of the horizontal holes 11 are alternately changed by 90 ° at the upper and lower positions so that the strength is not biased in the circumferential direction of the hollow rod 1. Has been. In addition, although the space | interval d is normally set to 25 cm, the distance from the front-end | tip of the digging screw member 12 to the lowest horizontal hole 11 is also equal to the space | interval d.

  Thus, the hollow rod 1 is used in addition to the solid rod 2 (see FIG. 6) used in the Swedish sounding test described above, and the added portion is shown in FIGS. 1C and 1D. Thus, the joint member 5 is used. The joint member 5 has a cylindrical shape and is formed with a male screw 51 on the outer periphery, and both ends 52a of the center hole 52 are open in a trumpet shape to prevent catching. On the other hand, female threads 13 are formed on the inner periphery of both ends of the hollow rod 1, and the upper and lower hollow rods 1 as shown in FIG. Are connected so that their end faces are in direct contact with each other.

  In the measurement method of the first embodiment, first, as shown in FIG. 2A, the hollow rod 1 made of a conductive material such as iron or stainless steel is vertically penetrated to a predetermined depth of the ground G. Although not shown in FIG. 2 (A), the clamp 22 and the handle 23 are attached to the upper portion of the hollow rod 1 in the same manner as the solid rod 2 shown in FIG. The weight 24 is loaded and the handle 23 is rotated. Thus, when the hollow rod 1 penetrates to the aquifer WZ, the groundwater W enters the hollow portion 10 of the hollow rod 1 from the lateral hole 11 which is lower than the groundwater level WL, and the hollow water 1 is about several minutes after the penetration stops. The water surface WF in the rod 1 reaches the same level as the groundwater level WL and stabilizes. In addition, the penetration penetration may be performed up to a depth reaching the underground aquifer, but may be performed up to 10 m underground in accordance with the Swedish sounding test.

  Next, as shown in FIG. 2 (B), one of the insulation cables 3A and 3A ′ for measurement consisting of one core wire connected to the measuring instrument 4A having a function of detecting a change in electrical resistance is insulated. The tip of the cable 3A ′ is electrically connected to the ground portion of the hollow rod 1, and the other insulated cable 3A having the electrode portion 31 on the tip side is inserted into the hollow portion 10 of the hollow rod 1 from above. When the electrode portion 31 of the insulated cable 3A reaches the water surface WF in the hollow rod 1, the electrical resistance between the electrode portion 31 and the hollow rod 1 constituting the electrode decreases due to the conductivity of the water W. This change in electrical resistance is detected and displayed by the measuring instrument 4A.

  Therefore, the groundwater level WL can be accurately determined from the insertion length of the insulated cable 3A when this change in electrical resistance is detected. That is, the groundwater level WL is a value obtained by subtracting the protruding height of the hollow rod 1 from the ground surface GL from the insertion length. The hollow rod 1 digging process in the measurement method of the first embodiment can be used for a general Swedish sounding test.

  In FIG. 2B, the one-core insulated cable 3A is inserted into the hollow rod 1, but a two-core insulated cable 3B connected to the measuring instrument 4B as shown in FIG. 2C may be used. . In this two-core insulated cable 3B, electrode portions 32a and 33a corresponding to both the core wires are arranged apart from each other on the tip side, and inside the hollow rod 1 that penetrates to the aquifer WZ of the ground G as shown in the figure. When both the electrode portions 32a and 33a come into contact with the water W in the hollow rod 1, the electrical resistance between the electrode portions 32a and 33a decreases, and this change in electrical resistance is applied to the measuring instrument 4A. Therefore, the groundwater level WL can be accurately measured from the insertion length at the time of detection as described above.

  In the measurement method of the second embodiment, first, as shown in FIG. 3A, the solid rod 2 having the excavation screw member 12 attached to the tip is dug vertically to a predetermined depth of the ground G, The solid rod 2 is pulled out to form an extraction hole H as shown in FIG. The solid rod 2 has the same configuration as that used in the Swedish sounding test shown in FIG. 6 and is attached with a clamp 22 and a handle 23 shown in FIG. Rotate. Thus, if the hollow rod 1 penetrates to the aquifer WZ, the groundwater W will be leached and collected in the extraction hole H.

  Next, as shown in FIG. 3 (C), when the hollow rod 1 similar to that used in the first embodiment is inserted into the extraction hole H, from the horizontal hole 11 that is lower than the groundwater level WL. The groundwater W enters the hollow portion 10, and the water surface WF in the hollow portion 10 reaches the same level as the groundwater level WL and stabilizes. Subsequently, as shown in FIG. 4D, as in the case of the first embodiment, one insulation cable 3A ′ connected to the measuring instrument 4A is electrically connected to the ground portion of the hollow rod 1 and the other insulation is provided. If the cable 3A is inserted into the hollow portion 10 of the hollow rod 1, when the electrode portion 31 reaches the water surface WF in the hollow rod 1, the electrical resistance between the electrode portion 31 and the hollow rod 1 is increased. This change in electrical resistance is detected and displayed by the measuring instrument 4A.

  Accordingly, also in the measurement method of the second embodiment, as in the case of the first embodiment, the groundwater level WL is accurately determined from the insertion length of the insulated cable 3A when a change in electrical resistance is detected. it can. And in this 2nd embodiment, since the excavation drilling with respect to the ground G of the front | former stage is performed with the solid rod 2 of high intensity | strength, the hollow rod 1 used for a ground water level measurement of a back | latter stage is the extraction | drawer of the solid rod 2 of a front | former stage. It is only necessary to penetrate into the hole H, and there is no problem even if the strength is insufficient for excavation due to the hollow structure. Further, the excavation process by the solid rod 2 in the previous stage can be used for the Swedish sounding test.

  In addition, when performing a two-stage operation as in the second embodiment, a pipe material with a simple horizontal hole 11 that does not have the digging screw member 12 attached to the lower end is also used as the hollow rod 1 used for the subsequent measurement of the groundwater level. Is possible. However, in the case where the ground G includes a soft stratum, even if the extraction hole H from which the solid rod 2 is pulled out is partially blocked by the collapse of the hole wall or the like, the latter hollow rod If 1 is provided with the digging screw member 12, there exists an advantage that it can penetrate deeply into this extraction hole H only by making it sink with light rotation. In the subsequent measurement of the groundwater level, a two-core insulated cable 3B [see FIG. 2C] connected to the measuring instrument 4B is used instead of the one-core insulated cable 3A as in the first embodiment. it can.

  In the case of the single-core insulated cable 3A, the use of a thick core wire with a strong waist facilitates the insertion into the hollow rod 1 and thus has the advantage that the work efficiency can be improved accordingly. In particular, when the core wire is made of wire, it is very easy to insert into the hollow rod 1 because it is strong, and the cost of material can be reduced because an inexpensive wire wire with a resin tube can be used. is there. On the other hand, in the case of the two-core insulated cable 3B, since the hollow rod 1 does not need a function as an electrode, there is an advantage that a non-conductive material such as plastic can be used as the hollow rod 1.

  FIG. 4 shows a configuration example of a one-core insulated cable 3 </ b> A made of a wire wire with a resin tube. In this insulated cable 3A, a core wire 31 of a wire is encapsulated by a resin tube 34 of an insulating material, and a part of the core wire 31 is exposed by removing a part of the resin tube 34 at the tip side thereof. In addition to forming the portion 31a, a tapered end 35 having a tapered tip and made of rubber or soft plastic is formed at the cable end. Thus, by having such a projecting end portion 35, it is possible to prevent the horizontal hole 11 and the joint member 5 from being caught when inserted into the hollow rod 1, so that the insertion operation becomes easier. Note that the insertion length L of the insulated cable 3A with respect to the hollow rod 1 is based on the electrode portion 31a.

FIG. 5 shows a configuration example of a two-core insulated cable 3B. In this insulated cable 3B, of the two core wires 32 and 33 embedded in the insulating layer 36, one core wire 32 protrudes from the front end surface of the cable to form an electrode portion 32a, and insulation on the cable peripheral surface side. A part of the core wire 33 is exposed by the notch 36a of the layer 36 to constitute the electrode portion 33a. Thus both electrode portions 32a, by 33a is spaced and end surface side and peripheral surface side of the cable, the electrodes portion 32a in the deposition of water droplets during insertion into the hollow rod 1, that the inter-33a conducts Can be prevented. With respect to the insertion length L of the insulated cable 3B with respect to the hollow rod 1, the electrode portion 33a on the peripheral surface side becomes the reference O.

  As the measuring instruments 4A and 4B having a function of detecting a change in electrical resistance, various commercially available products such as an electric wire type water level meter and a tester (ammeter) can be used. Thus, when a change in electrical resistance is detected, a method of notifying the user by a buzzer or a light-emitting lamp may be used in addition to the indication by a pointer or a screen.

  Further, as a means for digging the hollow rod 1 and the solid rod 2, FIG. 6 illustrates a manual method of loading with the weight 24 and rotating operation with the handle 23. However, in the present invention, the loading is performed by a machine using a hydraulic cylinder or the like. It is also possible to adopt a method of performing mechanical pressurization or mechanically performing a rotation operation with a motor or the like. Further, the hollow rod 1 and the solid rod 2 used in the present invention are not limited to those meeting the prescribed dimensions of the Swedish sounding tester established in the JIS standard, and those having various inner and outer diameters can be adopted. Also, as the excavation screw member attached to the tip of the rod, one having a shape and structure different from the screw point of the sounding tester can be used.

[Groundwater level measurement test]
Using a hollow rod with a horizontal hole shown in FIG. 1 (outer diameter 19 mm, inner diameter 7 mm, horizontal hole diameter 4 mm, horizontal hole interval 250 mm) with a screw point for Swedish sounding test as an excavation screw member. In each of the four planned detached house construction sites listed in Table 1, after passing the hollow rod to a depth of 4 m perpendicular to the ground according to the sounding test method, each elapsed time listed in Table 1 Insert a commercially available insulated cable (outer diameter: 5 mm, 2 cores) into the hollow rod for each pair of rod-type water gauges. It was confirmed that the electrode portion reached the surface of the groundwater in the hollow rod, and the groundwater level was measured from the insertion length of the insulated cable at that time. On the other hand, an observation hole with a diameter of about 0.2 m and a depth of about 1 m is formed by digging at a position 3 m away from the measurement point of the groundwater level, and the groundwater level in this observation hole is directly measured with a measure. Measured and used as the reference water level. And when the difference with a reference | standard water level was investigated about each said measurement water level, the result of Table 1 was obtained.

From the results in the above table, it can be seen that the water level in the hollow rod is stabilized in a short time after the hollow rod has penetrated , and that the difference between the measured water level and the actual water level (reference water level) is very small. Therefore, it can be said that the groundwater level measuring method of the present invention can measure the groundwater level of the ground accurately and efficiently in a short time with a simple apparatus configuration. In this groundwater level measurement test, drilling is performed up to 4 m underground, but it is also possible to drill up to 10 m underground in accordance with the Swedish sounding test.

The hollow rod used for the measuring method of the groundwater level of this invention is shown, (A) is a side view of the principal part, (B) is a sectional view taken along the line XX of (A), and (C) is a connection part. A longitudinal cross-sectional view, (D) is a cross-sectional view taken along line YY of (A). 1 shows a groundwater level measurement method according to a first embodiment of the present invention, wherein (A) is a state where a hollow rod is intruded, (B) is an inserted state of an insulation cable for measuring one core wire, and (C) is a two core wire. It is a model longitudinal cross-sectional view of the insertion state of the measurement insulated cable, respectively. The measurement method of the groundwater level which concerns on 2nd embodiment of this invention is shown in order of a process, (A) is the digging penetration state of a solid rod, (B) is the extraction state of a solid rod, (C) is to an extraction hole. (D) is a schematic longitudinal cross-sectional view of the penetration state of the hollow rod, and the insertion state of the measurement insulated cable of one core wire. It is a perspective view which shows the structural example of the front end side of the measurement insulated cable of 1 core wire used by this invention. It is a perspective view which shows the structural example by the side of the front-end | tip of the measurement insulated cable of 2 core wires used by this invention. It is a longitudinal cross-sectional view which shows the digging penetration state of the solid rod used for this invention and a Swedish sounding test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hollow rod 10 Hollow part 11 Horizontal hole 12 Digging screw member 2 Solid rod 21 Digging screw member 3A Insulation cable for measurement of 1 core wire 3B Insulation cable for measurement of 2 core wire 31 Core wire (wire)
31a Electrode part 32 Core wire 32a Electrode part 33 Core wire 33a Electrode part 4A Measuring instrument 4B Measuring instrument G Ground H Extraction hole L Insertion length W Groundwater WF Water surface WL Groundwater level

Claims (2)

A solid rod with an excavating screw member attached to the lower end is penetrated vertically into the ground by the load and rotation by a Swedish sounding tester, and then the solid rod is extracted to the ground, and then into the extraction hole. A function that detects the change in electrical resistance after rotating a hollow rod with a horizontal hole that penetrates the inside and outside at predetermined intervals in the longitudinal direction using a Swedish sounding tester and vertically penetrating it to a predetermined depth in the ground. A cylindrical measurement insulated cable consisting of a two-core wire connected to a measuring instrument equipped with is inserted into the hollow rod, and the electrode part on the end face side and the electrode part on the peripheral face side of the cylindrical insulation cable are in the hollow rod. Detecting the change in electrical resistance between the two electrode parts when reaching the surface of the groundwater infiltrated into the groundwater, measuring the groundwater level from the insertion length of the insulated cable at the time of detection,
The electrode portion on the end surface side and the electrode portion on the peripheral surface side of the insulated cable are configured to prevent conduction between the electrode portions due to adhesion of water droplets or the like when the insulated cable is inserted into the hollow rod. A method for measuring a groundwater level, characterized by being spaced apart in the axial direction. The groundwater level measuring method according to claim 1 , wherein an excavation screw member is attached to a lower end of a hollow rod that penetrates into the extraction hole.

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