JP5747654B2 - Water pressure measuring device, depth measuring device and penetration probe - Google Patents

Description

  The present invention relates to a water pressure measurement device, a depth measurement device, and an intrusion probe that are suitable for use in deep water.

  In recent years, methane hydrate has been spotlighted as a next-generation resource that can replace oil and natural gas. Even in the sea area around Japan, methane hydrate that is 100 times the annual consumption of natural gas in Japan exists, and the development of technology to produce it safely and economically is required. Among them, grasping the physical properties of methane hydrate and methane hydrate sedimentation ground is particularly important.

  Usually, in order to investigate the physical properties of a sample, it is common to carry a laboratory test by transporting the sampled sample to a laboratory. However, methane hydrate is stable under low temperature and high pressure conditions, but easily decomposes into water and gas under normal temperature and normal pressure conditions. In view of this, it has been pointed out that structural turbulence may occur due to gas generation accompanying hydrate decomposition and volume increase of dissolved gas. That is, it is important to grasp high-quality characteristic values that are not affected by the disturbance due to stress release.

  Since methane hydrate exists on the seabed ground at a depth of 300m or more, under these conditions, units and signal cables equipped with cone press-in / pull-out devices, data recording devices, etc. have been lowered to the seabed. The cone penetration test was conducted while taking the reaction force. However, in order to perform operations such as raising and lowering the unit and signal cables, drilling vessels and drilling rigs with large winches are indispensable, and surveys are very expensive and time consuming. There are very few examples at present.

  In order to solve such a problem, one of the inventors of the present invention has proposed a cone penetration testing machine shown in Patent Document 1. FIG. 4 shows a penetration probe used in this cone penetration tester. As shown in FIG. 4, the penetration probe 1 includes a cone 2 and a hollow rod 3. Inside the rod 3, a pressure sensor 4 for detecting an intrusion pressure acting on the cone 2, a data recording means 5, and a battery 6 are incorporated.

JP 2008-223378 A JP 2004-257858 A

  By the way, since the penetration depth at the time of penetration resistance measurement cannot be directly measured, a value corresponding to the elapsed time is calculated assuming that the penetration speed of the probe is constant, and this is regarded as the penetration depth. However, with such a method, the change in the depth direction of the penetration resistance cannot be accurately evaluated, which is a big problem. On the other hand, although the method of measuring the penetration depth based on the water depth converted from the water pressure is considered to be effective, a conventional water pressure gauge for large water depth (withstand pressure of 20 MPa, equivalent to a water depth of 2000 m) (for example, see Patent Document 2). There was a problem that the resolution of water depth measurement was insufficient.

  The present invention has been made in view of the above, and is a high-resolution water pressure measurement apparatus and depth measurement apparatus suitable for accurately measuring the penetration depth of a probe for a cone penetration test into the bottom of deep water. And to provide an intrusion probe.

In order to solve the above-described problems and achieve the object, a water pressure measuring device according to claim 1 of the present invention is a device for measuring the water pressure in the bottom ground, and includes a high pressure side introducing portion, a low pressure side introducing portion, A differential pressure gauge for measuring the differential pressure between the water pressure introduced by the high pressure side introduction portion and the water pressure introduced by the low pressure side introduction portion, a water pressure chamber capable of introducing a reference water pressure in water, and the water pressure chamber It has an on-off valve that opens and closes communication with the outside, and the low-pressure side introduction part introduces the pressure in the hydraulic chamber, and estimates the hydrostatic pressure from the excess pore water pressure in the bottom of the ground measured by a differential pressure gauge It is characterized by.

Moreover, the depth measuring apparatus which concerns on Claim 2 of this invention measures the depth in a water bottom ground based on the water pressure measured with the water pressure measuring apparatus of Claim 1 mentioned above.

  Moreover, the penetration probe which concerns on Claim 3 of this invention is a penetration probe for cone penetration tests, Comprising: The water pressure measuring device of Claim 1 mentioned above or the depth measuring device of Claim 2 is incorporated, It has a function of measuring its own penetration depth based on the measured water pressure or depth.

  The water pressure measuring device according to the present invention comprises a high-pressure side introduction part and a low-pressure side introduction part, and measures the differential pressure between the water pressure introduced by the high-pressure side introduction part and the water pressure introduced by the low-pressure side introduction part. Since it has a pressure gauge, a water pressure chamber capable of introducing a reference water pressure in water, and an open / close valve that opens and closes communication between the water pressure chamber and the outside, the low pressure side introduction portion introduces the pressure of the water pressure chamber. The differential pressure gauge measures the water pressure based on the differential pressure between the water pressure introduced by the high pressure side introduction portion and the water pressure in the water pressure chamber introduced by the low pressure side introduction portion. When the on-off valve is closed in water, the water pressure at that position is introduced into the water pressure chamber. Even if the external water pressure introduced by the high-pressure side introduction section changes, the water pressure chamber is kept at this reference water pressure, and the differential pressure gauge measures the differential pressure from this reference water pressure. For this reason, there is an effect that it is possible to accurately measure a change in water pressure even under a high pressure in a deep water region.

  Moreover, according to the depth measuring apparatus according to the present invention, since the depth is measured based on the water pressure measured by the above-described water pressure measuring apparatus, the differential pressure gauge is formed by the water pressure introduced by the high-pressure side introducing unit and the low-pressure side introducing unit. The water pressure is measured by the differential pressure of the water pressure in the introduced water pressure chamber. When the on-off valve is closed in water, the water pressure at that position is introduced into the water pressure chamber. Even if the external water pressure introduced by the high-pressure side inlet changes, the water pressure chamber is kept at this reference water pressure, and the differential pressure gauge sets the hydrostatic pressure distribution based on the differential pressure from the reference water pressure in the water pressure chamber. Estimate depth. In particular, when the penetration probe penetrates into the bottom ground at a constant speed, the excess pore water pressure is measured. Therefore, the hydrostatic pressure distribution in the bottom ground is estimated from the tendency of this excess pore water pressure distribution. Based on the distribution, the penetration depth in the ground is estimated. Since the value of the hydrostatic pressure distribution is based on the differential pressure from the latest reference water pressure, there is an effect that the depth change can be accurately measured even under a high pressure in a large water depth region.

  Further, according to the penetration probe according to the present invention, it is a penetration probe for a cone penetration test, and includes the above-described water pressure measuring device or depth measuring device, and measures its own penetration depth based on the measured water pressure or depth. Therefore, by using the water pressure and depth measured by the water pressure measuring device or depth measuring device, it is possible to accurately measure the penetration depth of the penetrating probe into the bottom of the ground even under high pressure in the deep water. There is an effect.

FIG. 1 is a diagram showing an embodiment of a water pressure measuring device, a depth measuring device, and a penetrating probe according to the present invention. FIG. 2 is a diagram for explaining the concept of depth measurement by water pressure measurement. FIG. 3 is a conceptual diagram of measurement of the penetration depth of the penetration probe according to the present invention. FIG. 4 is a side sectional view of a penetration probe of a conventional cone penetration tester.

  Hereinafter, embodiments of a water pressure measurement device, a depth measurement device, and an penetration probe according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

[Water pressure measuring device]
First, the water pressure measuring device according to the present invention will be described.
As shown in FIG. 1, a water pressure measuring device 10 according to the present invention includes a differential pressure gauge 16, a water pressure chamber 18 capable of introducing a reference water pressure in water, and an open / close that opens and closes communication between the water pressure chamber 18 and the outside. And a valve 22.

  The differential pressure gauge 16 includes a high pressure side introduction portion 12 and a low pressure side introduction portion 14, and measures a differential pressure between the external water pressure introduced by the high pressure side introduction portion 12 and the water pressure introduced by the low pressure side introduction portion 14. It is. A commercially available differential pressure gauge 16 can be used. For example, a differential pressure gauge with a relatively high measurement range of 50 to 100 kPa may be used.

  Since the low pressure side introduction part 14 introduces the pressure of the water pressure chamber 18, the differential pressure gauge 16 calculates the external water pressure introduced by the high pressure side introduction part 12 and the water pressure of the water pressure chamber 18 introduced by the low pressure side introduction part 14. The water pressure is measured by the differential pressure. When the on-off valve 22 is closed in water, the water pressure at that position is introduced into the water pressure chamber 18. Even if the external water pressure introduced by the high pressure side introduction unit 12 changes, the inside of the water pressure chamber 18 is maintained at this reference water pressure, and the differential pressure gauge 16 measures the differential pressure from this reference water pressure. For this reason, it is possible to accurately measure a change in water pressure even under a high pressure in a deep water region.

[Depth measurement device]
Next, the depth measuring apparatus according to the present invention will be described.
As shown in FIG. 1, the depth measurement device 20 according to the present invention measures depth based on the water pressure measured by the above-described water pressure measurement device 10. The differential pressure gauge 16 sets the hydrostatic pressure distribution based on the differential pressure from the reference water pressure in the hydraulic chamber 18 and estimates the underwater depth. In particular, when the penetration probe penetrates into the bottom ground at a constant speed, the excess pore water pressure is measured as shown in the left figure of FIG. The hydrostatic pressure distribution is estimated (see the right diagram in FIG. 2), and the penetration depth in the ground is estimated based on the hydrostatic pressure distribution. Since the value of the hydrostatic pressure distribution is based on the differential pressure from the latest reference water pressure, it is possible to accurately measure changes in depth even under high water depth.

[Penetration probe]
Next, the penetration probe according to the present invention will be described.
As shown in FIG. 1, a penetration probe 100 according to the present invention is a penetration probe for a cone penetration test, and includes a cone 24 and a hollow rod 26. The water pressure measuring device 10 or the depth measuring device 20 is built in the rod 26. The penetration probe 100 has a function of measuring its own penetration depth based on the water pressure or depth measured by the water pressure measurement device 10 or the depth measurement device 20.

  The rod 26 may further include a pressure sensor for detecting the penetration pressure acting on the cone 24, a data recording means, and a battery (none of which are shown) as in a conventional penetration probe. . Moreover, as an opening / closing operation method of the opening / closing valve 22, an opening / closing operation using a messenger weight, a remote operation using an electromagnetic valve, or the like can be used.

The operation and action of the above configuration will be described.
When the penetrating probe 100 is lowered in water, the on-off valve 22 is opened, and the pressure inside the hydraulic pressure chamber 18 and the outside pressure are made equal. And the on-off valve 22 is closed immediately before penetrating the penetration probe 100 into the water bottom ground. By doing so, the reference water pressure is introduced into the water pressure chamber 18.

  Next, the penetration probe 100 is penetrated into the ground with the on-off valve 22 being closed. During the penetration, the external water pressure is introduced by the high pressure side introduction portion 12 of the differential pressure gauge 16, and the water pressure of the water pressure chamber 18 is introduced by the low pressure side introduction portion 14, thereby measuring the pressure difference inside and outside the water pressure chamber 18. To do. Since the water pressure chamber 18 is maintained at the reference water pressure (water pressure on the ground surface) with the on-off valve 22 closed, the water pressure at the penetration depth is measured as a difference from the reference water pressure. By converting this measured water pressure into a penetration depth from the ground surface, the penetration depth of the penetration probe 100 can be accurately measured.

  When the penetrating probe 100 is pulled up, the on-off valve 22 may be opened again to equalize the pressure inside and outside the hydraulic chamber 18.

  Thus, according to the penetration probe 100 of the present invention, by using the water pressure and the depth measured by the water pressure measurement device 10 or the depth measurement device 20, the penetration probe penetrates into the water bottom ground even under high pressure in a large depth region. Depth can be measured accurately.

  FIG. 3 is a view showing the concept of measuring the penetration depth of the penetration probe according to the present invention. Fig. 3 (a) assumes the measurement of the cone tip resistance value in the normal sedimentary ground, and Fig. 3 (b) assumes the corn tip resistance value in the ground where the methane hydrate is deposited at a depth of 2 m or more. As shown in FIG. 3, it is expected that changes in the penetration resistance in the depth direction can be accurately evaluated, and that it is easy to estimate the strength characteristics of the sedimentary ground and the methane hydrate sedimentation depth.

  The water pressure measuring device, depth measuring device, and penetration probe of the present invention are mainly applied in the range of the surface layer number m of the bottom of the deep water (sea bottom / lake bottom). This is exactly the depth of deposition of methane hydrate that exists on the ground surface of the bottom of the water. As described above, there are very few measurement examples, but the water pressure measurement device, depth measurement device, and penetration probe of the present invention are present. The number of measurement examples is expected to increase in the future.

  Further, in the conventional cone penetration test described above, it is possible to investigate even deeper, but even when only the surface layer is investigated, the same cost and time as the deeper investigation are required. However, the water pressure measuring device, depth measuring device, and penetration probe of the present invention can be widely used not only for surface hydrate surveys but also for surveys where the mechanical properties of the surface layer of the seabed and lake bottom are required. .

  As described above, according to the water pressure measuring device according to the present invention, the high pressure side introduction portion and the low pressure side introduction portion are used, the water pressure introduced by the high pressure side introduction portion and the water pressure introduced by the low pressure side introduction portion. It has a differential pressure gauge that measures the differential pressure, a water pressure chamber that can introduce a reference water pressure in the water, and an on-off valve that opens and closes communication between the water pressure chamber and the outside. Since the pressure is introduced, the differential pressure gauge measures the water pressure by the differential pressure between the water pressure introduced by the high-pressure side introducing portion and the water pressure of the water pressure chamber introduced by the low-pressure side introducing portion. When the on-off valve is closed in water, the water pressure at that position is introduced into the water pressure chamber. Even if the external water pressure introduced by the high-pressure side introduction section changes, the water pressure chamber is kept at this reference water pressure, and the differential pressure gauge measures the differential pressure from this reference water pressure. For this reason, it is possible to accurately measure a change in water pressure even under a high pressure in a deep water region.

  Moreover, according to the depth measuring apparatus according to the present invention, since the depth is measured based on the water pressure measured by the above-described water pressure measuring apparatus, the differential pressure gauge is formed by the water pressure introduced by the high-pressure side introducing unit and the low-pressure side introducing unit. The water pressure is measured by the differential pressure of the water pressure in the introduced water pressure chamber. When the on-off valve is closed in water, the water pressure at that position is introduced into the water pressure chamber. Even if the external water pressure introduced by the high-pressure side inlet changes, the water pressure chamber is kept at this reference water pressure, and the differential pressure gauge sets the hydrostatic pressure distribution based on the differential pressure from the reference water pressure in the water pressure chamber. Estimate depth. In particular, when the penetration probe penetrates into the bottom ground at a constant speed, the excess pore water pressure is measured. Therefore, the hydrostatic pressure distribution in the bottom ground is estimated from the tendency of this excess pore water pressure distribution. Based on the distribution, the penetration depth in the ground is estimated. Since the value of the hydrostatic pressure distribution is based on the differential pressure from the latest reference water pressure, it is possible to accurately measure changes in depth even under high water depth.

  Further, according to the penetration probe according to the present invention, it is a penetration probe for a cone penetration test, and includes the above-described water pressure measuring device or depth measuring device, and measures its own penetration depth based on the measured water pressure or depth. Therefore, by using the water pressure and depth measured by the water pressure measuring device or the depth measuring device, it is possible to accurately measure the penetration depth of the penetration probe into the bottom ground even under a high pressure in a large water depth region.

  As described above, the water pressure measurement device, the depth measurement device, and the penetration probe according to the present invention are useful for the cone penetration test on the bottom of the deep water, and particularly for accurately measuring the penetration depth of the penetration probe. Is suitable.

DESCRIPTION OF SYMBOLS 10 Water pressure measuring device 12 High pressure side introduction part 14 Low pressure side introduction part 16 Differential pressure gauge 18 Water pressure chamber 20 Depth measurement device 22 On-off valve 24 Cone 26 Rod 100 Penetration probe

Claims (3)

A device for measuring the water pressure in the bottom of the ground ,
It consists of a high-pressure side introduction part and a low-pressure side introduction part, and introduces a differential pressure gauge that measures the differential pressure between the water pressure introduced by the high-pressure side introduction part and the water pressure introduced by the low-pressure side introduction part, and the reference water pressure in the water A possible hydraulic chamber and an on-off valve that opens and closes communication between the hydraulic chamber and the outside,
The low pressure side introduction part introduces the pressure of the hydraulic chamber ,
A water pressure measuring device for estimating a hydrostatic pressure from an excess pore water pressure in a water bottom ground measured by a differential pressure gauge . A depth measuring device that measures the depth in the bottom of the ground based on the water pressure measured by the water pressure measuring device according to claim 1.   A penetration probe for a cone penetration test, comprising the water pressure measuring device according to claim 1 or the depth measuring device according to claim 2, and a function of measuring its own penetration depth based on the measured water pressure or depth. A penetrating probe characterized by comprising:

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