JP2021181965A - Underground water observation device and underground water observation method - Google Patents

Abstract

To provide an underground water observation device and an underground water observation method capable of simultaneously performing pressure observation and underground water sampling in one borehole.SOLUTION: An underground water observation device comprises: a casing pipe 12 which is inserted into and arranged in a borehole 10; a plurality of water-blocking packers 14 which are arranged around the casing pipe 12 vertically at an interval; a pressure gauge 18 which is provided outside the casing pipe 12 in order to measure water pressure of underground water in the section defined with the packers 14; and an optical fiber cable 16 which is arranged along between a borehole wall 10A and the casing pipe 12 in order to transmit light for pressure detection of the pressure gauge 18.SELECTED DRAWING: Figure 1

Description

The present invention relates to a groundwater observation device and a groundwater observation method.

An example of a conventional groundwater survey is shown in FIG. 4 (see Non-Patent Document 1). FIG. 4 (1) is a system in which a boring hole is excavated for each survey target depth to conduct a survey, and as many boring holes as the number of survey targets are excavated. On the other hand, FIGS. 4 (2) and 4 (3) are a system for investigating a plurality of investigation depths with one boring hole.

Each survey method has its own characteristics, but in general, the method of FIG. 4 (1) is more economical unless the survey depth is shallow and the number of survey depths is not so large. On the other hand, when the survey depth becomes deep and the number of survey points increases, the methods shown in FIGS. 4 (2) and 4 (3) are more convenient.

FIG. 5 shows an outline of the groundwater survey system (MP system) of FIG. 4 (3). In this MP system, a casing pipe with a plurality of packers 3 called an MP casing 2 is installed in a boring hole 1. In this MP system, as shown in FIG. 5A, a pressure gauge 5 connected to a cable 4 can be installed at a measurement port in the MP casing 2. As a result, the groundwater pressure in each section can be recorded in the data logger 6 on the ground. Further, as shown in FIG. 5B, the water sampling probe 7 and the water sampling bottle 8 connected to the cable 4 can be installed in the measurement port in the MP casing 2 via the winch 9 on the ground. As a result, the groundwater in each section divided by the packer 3 can be sampled into the sampling bottle 8 via the sampling probe 7. The features of this MP system are summarized below.
(1) It is possible to survey groundwater at multiple points with one boring hole.
(2) Pressure gauges can be installed at multiple survey points in the hole to observe pressure.
(3) By combining a water sampling probe for groundwater sampling and a water sampling bottle, it is possible to collect a groundwater sample in a sealed state.

Yuji Takeshita: “Recent Groundwater Survey Method and Measurement Technology” 6. Measurement of Groundwater Dynamics 6.1 Measurement Method of Groundwater Level and Pressure, Journal of Groundwater Society, Vol. 36, No. 3 (1994), 293-303.

Japanese Unexamined Patent Publication No. 2012-225002

In the above-mentioned conventional MP system, continuous pressure observation is performed by installing pressure gauges at multiple survey points in one hole, and groundwater sampling is performed by withdrawing the pressure gauge 7. .. In recent years, there has been a need to collect groundwater while maintaining the continuity of groundwater pressure observation, but it is difficult for conventional MP systems to meet that need. That is, in the state where the pressure gauge 5 is installed in the MP casing 2 as shown in FIG. 5A, the water sampling probe 7 and the water sampling bottle 8 cannot be further inserted into the MP casing 2 as shown in FIG. 5B. It is. If the conventional MP system can be used, it is conceivable to excavate two boring holes 1 and install a pressure gauge 5 in one to constantly observe the pressure and to collect water regularly in the other. Be done. In this case, there is a problem that the boring cost is doubled. Therefore, there has been a demand for an MP system capable of simultaneously performing pressure observation and groundwater sampling in one boring hole.

Therefore, the present inventor has diligently studied a method capable of simultaneously performing continuous pressure observation and groundwater sampling in one boring hole. Focusing on the need to be able to insert the groundwater sampling probe and sampling bottle into the MP casing while observing the pressure, a smaller diameter optical fiber is used for the pressure observation instead of the conventional pressure gauge. I thought about using it.

Since pressure observation using an optical fiber utilizes the difference between the waveforms of the input wave and the reflected wave, it is necessary to avoid adding optical fibers in order not to impair the accuracy. Therefore, since it is desired that there is only one from the hole opening to the hole bottom, it was found that the connection with the MP casing, particularly the connection with the packer, is very important, and the present invention was made.

The present invention has been made in view of the above, and an object of the present invention is to provide a groundwater observation device and a groundwater observation method capable of simultaneously performing pressure observation and groundwater sampling in one boring hole.

In order to solve the above-mentioned problems and achieve the object, the groundwater observation device according to the present invention has a casing pipe inserted in the boring hole and a plurality of groundwater observation devices arranged at intervals in the vertical direction with respect to the circumference of the casing pipe. A packer for impermeable water, a pressure gauge provided on the outside of the casing pipe to measure the water pressure of the groundwater in the section separated by the packer, and light for pressure detection in the pressure gauge. It is characterized by comprising an optical fiber cable arranged along between the boring hole wall and the casing pipe.

Further, another groundwater observation device according to the present invention is characterized in that, in the above-mentioned invention, the optical fiber cable is inserted and arranged in the gap between the boring hole wall and the packer.

Further, another groundwater observation device according to the present invention is characterized in that, in the above-mentioned invention, the optical fiber cable is inserted and arranged in the gap provided in the packer.

Further, in the other groundwater observation apparatus according to the present invention, in the above-described invention, the optical fiber cable is arranged along the outside of the casing pipe in the section where the packer of the casing pipe is not arranged, and in the section where the packer is arranged. Is characterized in that it is arranged along the inside of the casing pipe.

Further, the groundwater observation method according to the present invention includes a pressure observation step for continuously measuring the water pressure of groundwater in a section divided by a packer using the pressure gauge of the above-mentioned groundwater observation device, and the inside of the casing pipe from the ground. The water sampling probe and the water sampling bottle are unloaded, the water sampling probe is connected to the water sampling port provided in the casing pipe, and the groundwater in the section separated by the packer is collected in the water sampling bottle via the water sampling probe. It is characterized by performing the sampling steps at the same time.

According to the groundwater observation device according to the present invention, a casing pipe inserted into the boring hole, a plurality of impermeable packers arranged at intervals in the vertical direction with respect to the circumference of the casing pipe, and a packer are used to separate the casing pipes. A pressure gauge provided on the outside of the casing pipe to measure the water pressure of the groundwater in the section, and placed along between the boring hole wall and the casing pipe to transmit light for pressure detection in the pressure gauge. Since it is equipped with an optical fiber cable, the groundwater sampling probe and sampling bottle can be inserted into the casing pipe while observing the pressure. Therefore, it is possible to perform pressure observation and groundwater sampling at the same time in one boring hole.

Further, according to another groundwater observation device according to the present invention, the optical fiber cable is inserted and arranged in the gap between the boring hole wall and the packer, so that the groundwater sampling probe and the groundwater sampling probe are sampled while the pressure is being observed. The water bottle can be inserted into the casing pipe, which has the effect of simultaneously performing pressure observation and groundwater sampling in one boring hole.

Further, according to another groundwater observation device according to the present invention, the optical fiber cable is inserted and arranged in the gap provided in the packer, so that the groundwater sampling probe and the sampling bottle can be used while observing the pressure. It can be inserted into the casing pipe, and has the effect that pressure observation and groundwater sampling can be performed simultaneously in one boring hole.

Further, according to another groundwater observation device according to the present invention, the optical fiber cable is arranged along the outside of the casing pipe in the section where the packer of the casing pipe is not arranged, and the casing pipe is arranged in the section where the packer is arranged. Since it is placed along the inside of the casing, the groundwater sampling probe and sampling bottle can be inserted into the casing pipe while observing the pressure, and the pressure observation and groundwater sampling can be performed simultaneously in one boring hole. It has the effect of being able to do it.

Further, according to the groundwater observation method according to the present invention, a pressure observation step for continuously measuring the water pressure of groundwater in a section divided by a packer using the pressure gauge of the above-mentioned groundwater observation device, and a casing pipe from the ground. The water sampling probe and the water sampling bottle are lowered inside the water sampling probe, the water sampling probe is connected to the water sampling port provided in the casing pipe, and the groundwater in the section separated by the packer is collected in the water sampling bottle via the water sampling probe. Since the groundwater sampling steps to be performed are carried out at the same time, there is an effect that continuous pressure observation and groundwater sampling can be performed simultaneously in one boring hole.

FIG. 1 is a side sectional view showing the first embodiment of the groundwater observation device and the groundwater observation method according to the present invention. FIG. 2 is a plan sectional view showing the second embodiment of the groundwater observation device and the groundwater observation method according to the present invention. FIG. 3 is a side sectional view showing the third embodiment of the groundwater observation device and the groundwater observation method according to the present invention. FIG. 4 is a diagram showing an example of a conventional groundwater survey. FIG. 5 is a diagram showing an outline of a conventional MP system.

Hereinafter, embodiments of the groundwater observation device and the groundwater observation method according to the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment.

(Embodiment 1)
First, Embodiment 1 of the present invention will be described.
As shown in FIG. 1, the groundwater observation device 100 according to the first embodiment has a plurality of casing pipes 12 inserted and arranged in the boring hole 10 and a plurality of casing pipes 12 at intervals in the vertical direction with respect to the periphery of the casing pipe 12. A packer 14 for impermeable water to be arranged, an optical fiber cable 16 inserted through a gap between the boring hole wall 10A and the packer 14, and a pressure gauge 18 are provided.

The casing pipe 12 guides the water sampling probe and the water sampling bottle descended from the ground via the cable to the water sampling port when the groundwater is sampled (see FIG. 5B). The water sampling port is provided in the casing pipe 12 of each section separated by the packer 14. The descended water sampling probe can be brought into close contact with a predetermined water sampling port by an air jack or the like under the control of a control device arranged on the ground. The groundwater on the outside of the casing pipe 12 can be sampled into a sampling bottle via a sampling probe in close contact with the sampling port.

The optical fiber cable 16 is for transmitting light for pressure detection in the pressure gauge 18, and is basically arranged outside the casing pipe 12. The optical fiber cable 16 of the present embodiment is assumed to have a diameter of about 5 mm, but the present invention is not limited to this. The optical fiber cable 16 transmits the value detected by the pressure gauge 18 to a data logger or the like on the ground by an optical signal. The transmitted detection value is recorded in the data logger. Since it is better not to add an optical fiber cable so as not to impair the pressure measurement accuracy, it is desirable to use one optical fiber cable continuous from the hole opening of the boring hole 10 to the hole bottom.

The pressure gauge 18 is for measuring the water pressure of the groundwater in the section divided by the packer 14. In this embodiment, an FBG (Fiber Bragg Grating) sensor using an optical fiber is used as the pressure gauge 18. The FBG sensor utilizes the fact that parts with different refractive indexes, called diffraction gratings, are arranged in a grid pattern at regular intervals on a part of the core of the optical fiber, and only light of a specific wavelength proportional to the intervals is reflected. It is a sensor that measures pressure. A plurality of the FBG sensors can be arranged in series on one optical fiber cable 16. The pressure gauge of the present invention is not limited to the FBG sensor, and may be configured by using another type of optical fiber sensor such as BOTDA or BOTDR. The pressure gauge 18 may be arranged between the boring hole wall 10A of each section and the casing pipe 12, or may be fixed to the outer peripheral surface of the casing pipe 12.

According to this embodiment, the water sampling probe and the water sampling bottle can be inserted into the casing pipe 12 from the ground while the pressure is being observed by the pressure gauge 18. Therefore, continuous pressure observation and groundwater sampling can be performed simultaneously in the MP system of one boring hole 10.

Further, by using an optical fiber for pressure observation, unlike a conventional electric pressure measurement system, performance deterioration and failure due to water intrusion are eliminated, so that maintenance-free operation can be realized. Further, if the above-mentioned conventional MP system is to be used for pressure observation and groundwater sampling, two boring holes and an MP system are required, which is costly. However, if this embodiment is applied, pressure observation and groundwater sampling can be performed simultaneously with one boring hole and the MP system, so that the cost can be saved as compared with the conventional MP system.

(Embodiment 2)
Next, Embodiment 2 of the present invention will be described.
As shown in FIG. 2, the groundwater observation device 200 according to the second embodiment inserts and arranges the optical fiber cable 16 in the gap between the boring hole wall 10A and the packer 14 in the first embodiment. A gap 20 penetrating the inside of the packer 14 in the vertical direction is provided, and the optical fiber cable 16 is inserted and arranged in the gap 20. That is, in the section where the packer 14 is arranged, the optical fiber cable 16 is wound around the packer 14 and arranged. Even in this way, the same effects as described above can be obtained.

(Embodiment 3)
Next, Embodiment 3 of the present invention will be described.
As shown in FIG. 3, the groundwater observation device 300 according to the third embodiment inserts and arranges the optical fiber cable 16 in the gap between the boring hole wall 10A and the packer 14 in the first embodiment. The optical fiber cable 16 passes through the casing pipe 12 only in the section where the packer 14 is arranged. Specifically, the optical fiber cable 16 is arranged along the outside of the casing pipe 12 in the section where the packer 14 is not arranged, and is arranged along the inside of the casing pipe 12 in the section where the packer 14 is arranged. .. The optical fiber cable 16 is passed through the casing pipe 12 via the insertion holes 22 provided at the upper and lower positions of the packer 14. Even in this way, the same effects as described above can be obtained.

As described above, according to the groundwater observation device according to the present invention, the casing pipe inserted into the boring hole and a plurality of casing pipes arranged at intervals in the vertical direction with respect to the circumference of the casing pipe are used for impermeable water. A packer, a pressure gauge provided on the outside of the casing pipe to measure the water pressure of the groundwater in the section separated by the packer, and a boring hole wall and a casing pipe to transmit light for pressure detection in the pressure gauge. Since it is equipped with an optical fiber cable arranged along the space between the two, the groundwater sampling probe and the sampling bottle can be inserted into the casing pipe while observing the pressure. Therefore, pressure observation and groundwater sampling can be performed simultaneously in one boring hole.

Further, according to another groundwater observation device according to the present invention, the optical fiber cable is inserted and arranged in the gap between the boring hole wall and the packer, so that the groundwater sampling probe and the groundwater sampling probe are sampled while the pressure is being observed. A water bottle can be inserted into the casing pipe, and pressure observation and groundwater sampling can be performed simultaneously in one boring hole.

Further, according to another groundwater observation device according to the present invention, the optical fiber cable is inserted and arranged in the gap provided in the packer, so that the groundwater sampling probe and the sampling bottle can be used while observing the pressure. It can be inserted into the casing pipe, and pressure observation and groundwater sampling can be performed simultaneously in one boring hole.

Further, according to another groundwater observation device according to the present invention, the optical fiber cable is arranged along the outside of the casing pipe in the section where the packer of the casing pipe is not arranged, and the casing pipe is arranged in the section where the packer is arranged. Since it is placed along the inside of the casing, the groundwater sampling probe and sampling bottle can be inserted into the casing pipe while observing the pressure, and the pressure observation and groundwater sampling can be performed simultaneously in one boring hole. It can be carried out.

Further, according to the groundwater observation method according to the present invention, a pressure observation step for continuously measuring the water pressure of groundwater in a section divided by a packer using the pressure gauge of the above-mentioned groundwater observation device, and a casing pipe from the ground. The water sampling probe and the water sampling bottle are lowered inside the water sampling probe, the water sampling probe is connected to the water sampling port provided in the casing pipe, and the groundwater in the section separated by the packer is collected in the water sampling bottle via the water sampling probe. Since the groundwater sampling steps to be performed are carried out at the same time, continuous pressure observation and groundwater sampling can be performed simultaneously in one boring hole.

As described above, the groundwater observation device and the groundwater observation method according to the present invention are useful for investigating a plurality of investigation depths with one boring hole, and are particularly suitable for performing pressure observation and groundwater sampling at the same time. ing.

10 Boring hole 10A Boring hole wall 12 Casing pipe 14 Packer 16 Optical fiber cable 18 Pressure gauge 20 Gap 22 Insertion hole 100-300 Groundwater observation device

Claims (5)

To measure the water pressure of the casing pipe inserted into the boring hole, the packer for impermeable arrangement arranged at intervals in the vertical direction with respect to the circumference of the casing pipe, and the groundwater in the section separated by the packer. It is characterized by having a pressure gauge provided on the outside of the casing pipe and an optical fiber cable arranged along between the boring hole wall and the casing pipe to transmit light for pressure detection in the pressure gauge. Groundwater observation device. The groundwater observation device according to claim 1, wherein the optical fiber cable is inserted and arranged in a gap between the boring hole wall and the packer. The groundwater observation device according to claim 1, wherein the optical fiber cable is inserted and arranged in a gap provided in the packer. A claim is characterized in that the optical fiber cable is arranged along the outside of the casing pipe in the section where the packer of the casing pipe is not arranged, and is arranged along the inside of the casing pipe in the section where the packer is arranged. The groundwater observation device according to 1. Using the pressure gauge of the groundwater observation device according to any one of claims 1 to 4, the pressure observation step for continuously measuring the water pressure of the groundwater in the section divided by the packer, and the inside of the casing pipe from the ground. The water sampling probe and the water sampling bottle are unloaded, the water sampling probe is connected to the water sampling port provided in the casing pipe, and the groundwater in the section separated by the packer is collected in the water sampling bottle via the water sampling probe. A groundwater observation method characterized by performing sampling steps at the same time.

Images