JP2008020279A - Thickness measuring apparatus for water-bottom earth and sand and drift sand observation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thickness measuring apparatus for water-bottom earth and sand and a drift sand observation system which can measure the thickness of earth and sand accumulated on the bottom of the sea, rivers, lakes and marshes, dam lakes, or the like and the thickness of earth and sand reduced by erosion at all times regardless of weather. <P>SOLUTION: The measuring apparatus 1 for water-bottom earth and sand is an apparatus for measuring the thickness of earth and sand accumulated on the water-bottom. The measuring apparatus 1 comprises a fine-particle earth and sand pressure gauge 5 which is buried horizontally at a predetermined depth position from the bottom to measure pressure by fine-particle earth and sand in the earth and sand accumulated on the water-bottom and by water, a soil material pressure gauge 6 which is placed horizontally at a position which is the same depth position from the bottom as the fine-particle earth and sand pressure gauge 5 and is in the vicinity thereof to measure pressure by soil material earth and sand in the earth and sand accumulated on the water-bottom and by water, and a calculation apparatus 21 which calculates the thickness of the earth and sound accumulated on the water-bottom on the basis of the difference between a first output signal indicating the pressure measured by the fine-particle earth and sand pressure gauge 5 and a second output signal indicating the pressure measured by the soil material pressure gauge 6. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a bottom sediment thickness measurement apparatus and a drift sand observation system that measure the thickness of sediment deposited on the bottom of a sea, a river, a lake, a dam lake, or the like, and the thickness of eroded sediment.

  In general, when it rains on the slopes of a mountainside and becomes flooded, the sediment on the mountainside flows into the river as a debris flow (also called a solid-liquid mixed phase flow), and eventually the sediment reaches the bottom of the river or dam lake. It may accumulate, or it may flow to the sea by water flow and accumulate on the seabed. In this way, in rivers, dam lakes, and the sea, the sediment thickness on the bottom surface changes due to sediment accumulation on the bottom surface, and the bottom surface and coastal topography change.

  In recent years, with the construction of dams and sabo dams, the inflow of earth and sand into the sea has decreased, and the coast has been eroded by the flow of waves and tides, and shallow coasts have decreased, Phenomenon such as position retreating has appeared. For this reason, the thickness of the sediment deposited on the coastal seafloor changes greatly in time series due to deposition and erosion.

  As means for measuring the thickness of sediment deposited on the bottom of the water, several bottom sediment thickness measuring devices have been developed. For example, as a measuring device for measuring the thickness of sediment deposited on the bottom surface of a dam lake, etc., the bottom of the lake is obtained by the operation of a light emitter disposed opposite to a sensor rod with a pitch of several [cm] and a light receiver in the light receiver. There is known a sand level meter that measures the position of the sand surface (see, for example, Patent Document 1).

  In addition, as a device to measure the thickness of the sand spread from the sand dredger to the sea floor, one of the depth gauges lowered from the sand dredger to the sea floor by the rope and the sand scattered from the sand dredger There is known a sand thickness measuring device that measures the thickness of spread sand based on the difference in water depth measured with the other depth gauge lowered by a rope (for example, see Patent Document 2).

Sediment accumulation and erosion in coastal and estuary areas were observed by using sand bathing data obtained by measuring the depth of the sea regularly every year using an acoustic sounding instrument mounted on a work boat. is doing.
In addition, when measuring the thickness of accumulated sediment with an acoustic sounding instrument, it is measured on the ship's ship. Is measured. As another method for measuring the thickness of earth and sand, there is a method in which an operator visually measures using a ruler.
Japanese Utility Model Publication No. 3-4895 (FIGS. 1 and 2) JP-A 64-35207 (FIG. 2)

However, the bottom sediment thickness measuring device as described in Patent Documents 1 and 2 is artificially measured when measuring the thickness of sediment deposited on the bottom surface of a river, a dam lake or the sea. Because of the measurement using a ship, it was difficult to measure the thickness of sediment deposited on the bottom of the water and to observe sediment dynamics during floods and stormy weather where the sediments were fluctuating.
For this reason, there has been a need for the development of a method that can observe drift sand during waves, measure the thickness of sediment deposited on the bottom of a water during floods, and observe sediment on the bottom of the water at any time during daily life.

  In addition, when the thickness of sediment deposited on the bottom of the water is artificially measured with the bottom sediment thickness measuring device described in Patent Documents 1 and 2, the measured value of the sediment is measured from the measured value on a sunny day after the flood. Since the thickness must be obtained, observation of changes in sediment thickness during waves, observation of changes in the topography of the bottom due to liquid sand and drift sand, measurement of wide-area sediment thickness over a given area, Observing the dynamics of sediment was virtually difficult.

  In such rivers, dam lakes, lakes, and seas, in order to understand the amount of sediment supplied from the river, the shape of sandy beaches along the coastline, and the shape of the bottom of the water, It is desired to measure the thickness of the eroded earth and sand on the bottom, and to comprehensively observe the distribution of the earth and sand on the bottom of the water during floods and waves.

  Therefore, the present invention was devised in view of the above circumstances, and the thickness of the earth and sand deposited on the bottom surface of the sea, rivers, lakes, and dam lakes, and the thickness of the earth and sand reduced by erosion are taken into account in the weather. It is an object of the present invention to provide a bottom sediment thickness measuring device and a drift sand observation system that can always measure without being influenced.

  In order to solve the above-mentioned problem, the bottom sediment thickness measuring device according to claim 1 is a bottom sediment thickness measuring device that measures the thickness of sediment deposited on the bottom surface, and a position at a predetermined depth from the bottom surface. A fine-grained pressure gauge that measures pressure due to fine-grained sediment and water in the sediment deposited horizontally on the bottom of the water, and the same depth from the bottom of the water where the fine-grained pressure gauge is embedded Soil material pressure gauge that is buried horizontally in the vicinity of the position and measures the pressure due to the soil material and sand in the sediment deposited on the bottom of the water, and the pressure measured by the fine grain pressure gauge An arithmetic unit that calculates the thickness of the sediment deposited on the bottom of the water by calculation based on a difference between the first output signal and the second output signal indicating the pressure measured by the soil material pressure gauge. Features.

Here, the predetermined depth from the bottom of the water is, for example, an arbitrarily set depth from the bottom of the sea, the riverbed of a river, the bottom of a lake, a lake of a dam lake, etc. into the ground. When the bottom surface is made of a soil material earth and sand, the water bottom surface has a depth of 0.5 to 1 [m]. In addition, when the bottom of the water is bedrock, the sediment thickness measuring instrument is directly fixed to the bottom of the water with an anchor or the like, and the thickness of sediment deposited is measured even if the predetermined depth is 0 [m]. It is possible.
Further, the fine grained sand means sand having a particle size of about 74 [μm] or less. The coarse-grained sediment is a gravel having a particle size of about 74 [μm] or less, and the soil material earth and sand includes a fine-grained and coarse-grained sediment.

According to this configuration, the fine grain pressure gauge and the soil material pressure gauge are embedded in the earth and sand having a predetermined depth from the bottom of the water. The earth and sand filled with the fine-grain pressure gauge and the soil material pressure gauge and the water in the earth and sand are the gap between the earth and sand particles in the so-called solid-liquid mixed phase part of the earth and sand (solid phase) and water (liquid phase) due to water pressure and the like. The ratio becomes dense and is loaded onto the fine grain pressure gauge and the soil material pressure gauge. For example, the earth and sand carried by the flow of water or the like is deposited on the bottom of the water above the fine particle pressure gauge and the soil material pressure gauge in a state where a solid-liquid mixed phase portion is formed by water pressure or the like. The pressure by the solid-liquid mixed phase part of fine-grained sediment and water in the sediment is measured by a fine-grained pressure gauge. Moreover, the pressure by the solid-liquid mixed phase part of the earth material earth and water in the earth and sand is measured by the earth material pressure gauge. From the fine grain pressure gauge and the soil material pressure gauge, a first output signal and a second output signal indicating the pressure are output to the arithmetic unit, respectively. The computing device calculates the thickness of the sediment deposited on the bottom of the water from the start of measurement based on the difference between the first output signal from the fine grain pressure gauge and the second output signal from the soil material pressure gauge.
In addition, the bottom sediment thickness measuring device is a value of sediment thickness calculated by the arithmetic unit based on the pressure measured by the fine particle pressure gauge and soil material pressure gauge embedded at a predetermined depth from the bottom of the water. When the value exceeds the reference value (initial value), the thickness of the sediment deposited on the bottom of the water is measured. When the value falls below the reference value (initial value), the thickness of the eroded sediment on the bottom of the water Can be measured.

  The underwater sediment thickness measuring device according to claim 2 is the underwater sediment thickness measuring device according to claim 1, wherein the fine particle pressure gauge is present at a position where the fine particle pressure gauge is embedded. A hollow fine-grain sensor housing having an inflow port through which fine-grained sediment in the sediment and water in the sediment flows, and the fine-grain sensor housing are installed in the fine-grain sensor housing. A filter that allows the fine-grained sediment and water in the sediment flowing into the body to pass therethrough, and a pressure that is installed below the filter and that passes through the filter to detect pressure due to the fine-grained sediment and the water. A fine particle sensor unit that generates the first output signal, and a substrate on which the fine particle sensor unit and the fine particle sensor housing are mounted.

  According to this configuration, the fine grain pressure gauge is embedded in the bottom sediment. The earth and sand filled with the fine particle pressure gauge and the water in the earth and sand are formed in a state where the pore ratio of the earth and sand particles in the solid-liquid mixed phase portion of the earth and water is dense due to water pressure or the like. Sediment in the solid-liquid mixed phase portion existing at the position where the fine particle pressure gauge is embedded flows into the hollow fine particle sensor housing from the inlet of the fine particle sensor housing. The fine-grained sediment and water in the infused earth-and-sand flow through the filter in the state of the solid-liquid mixed phase part, flow into the fine-grain part sensor part, and press the fine-grain part sensor part. And the earth and sand which were carried and accumulated above the fine particle pressure gauge by the flow of water etc. are deposited on the bottom of the water above the fine particle pressure gauge in a state where a solid-liquid mixed phase portion is formed by water pressure or the like. The pressure by the solid-liquid mixed phase part of fine-grained sediment and water in the sediment is measured by a fine-grained pressure gauge.

  The bottom sediment thickness measuring device according to claim 3 is the bottom sediment thickness measuring device according to claim 1 or 2, wherein the soil material pressure gauge is a soil material in the sediment deposited on the bottom of the water. A soil material sensor unit that detects the pressure of the soil and the water and generates the second output signal, and the soil material pressure gauge in the soil where the soil material pressure gauge is embedded on the soil material sensor unit A cover body installed with a gap through which the soil material soil and water in the soil material soil flow in, a substrate on which the soil material sensor unit is placed, and an intervening space between the substrate and the cover body And a plurality of struts for forming a space through which the soil material earth and sand and the water flow into the gap.

  According to such a configuration, the soil material pressure gauge is embedded in the bottom sediment. The earth and sand filled with the soil material pressure gauge and the water in the earth and sand are formed in a state where the pore ratio of the earth and sand particles in the solid-liquid mixed phase portion of the earth and sand is dense due to the water pressure or the like. Sediment in the solid-liquid mixed phase portion existing at the position where the soil material pressure gauge is embedded flows into the soil material sensor casing from the space below the cover body. The soil material and sand in the inflowed soil enter the gap between the cover body and the soil material sensor unit, and press the soil material sensor unit. And the earth and sand which were conveyed above the soil material pressure gauge by the flow of water etc. accumulates on the water bottom above the soil material pressure gauge in the state which formed the solid-liquid mixed phase part by the water pressure. The pressure by the solid-liquid mixed phase part of the soil material earth and water in the soil is measured by a soil material pressure gauge.

  The bottom sediment thickness measuring device according to claim 4 is the bottom sediment thickness measuring device according to any one of claims 1 to 3, wherein the fine particle pressure gauge and the soil material pressure gauge are And mounted on a pedestal embedded at a predetermined depth from the water bottom.

  According to such a configuration, the fine-grain pressure gauge and the soil material pressure gauge are mounted on the same pedestal embedded at a predetermined depth from the water bottom, so that the fine-grain pressure gauge near the bottom of the water And the pressure by the soil material pressure gauge are respectively detected. Therefore, based on the difference between the pressure value measured with the fine-grained pressure gauge and the pressure value measured with the soil material pressure gauge, the thickness of the sediment deposited on the bottom of the bottom of the bottom sediment thickness measuring device or eroded It becomes possible to calculate the thickness of earth and sand.

  The underwater sediment thickness measuring apparatus according to claim 5 is the underwater sediment thickness measuring apparatus according to any one of claims 1 to 4, wherein the arithmetic unit is configured to output the second output signal and the second output signal. The thickness of the sediment deposited on the bottom of the water as a result of dividing the difference from one output signal by the difference between the preset constant rate correction coefficient of the solid-liquid mixed phase composed of sediment and water and the weight per unit volume of water It is characterized by seeking the thickness.

According to such a configuration, in the arithmetic device, the difference between the second output signal and the first output signal is divided by the difference between the constant rate correction coefficient of the solid-liquid mixed phase portion and the weight per unit volume of water on the bottom surface of the water. The thickness of the accumulated sediment.
For example, the thickness of the deposited sediment H1, the fine fraction manometer and ΔP the difference in pressure measured with a soil material pressure gauge and a fixed-rate correction coefficient and gamma _a, the thickness H1 of the deposited sediment,
H1 = ΔP / (γ _a −1)
It is.
Here, “1” is the weight per unit volume of water.

The sand drift observation system according to claim 6 is a sand drift observation system for observing the thickness of the sediment deposited on the bottom of the water, and is a fine sand measurement system for measuring the pressure caused by finely divided sediment and water in the sediment deposited on the bottom of the water. A granule pressure gauge, a soil material pressure gauge for measuring the pressure of the soil material earth and sand in the sediment deposited on the bottom of the water, and a pedestal on which the fine grain pressure gauge and the soil material pressure gauge are mounted A plurality of sediment thickness measuring instruments that are horizontally embedded at a predetermined depth from the bottom surface of the water and installed at predetermined intervals along the bottom surface of the water, and the fine particle pressure gauge An arithmetic device for determining the thickness of the sediment deposited on the bottom of the water by calculation based on a difference between a first output signal indicating the measured pressure and a second output signal indicating the pressure measured by the soil material pressure gauge; Between the earth and sand thickness measuring instrument and the arithmetic unit. Or characterized by comprising a signal transmitting means for transmitting a wireless signal.
Here, the predetermined interval along the bottom surface is an arbitrary distance interval, for example, 5 to 20 [m] when the bottom surface is the sea bottom.

  According to such a configuration, a plurality of earth and sand thickness measuring instruments equipped with fine grain pressure gauges and soil material pressure gauges are embedded at a predetermined depth from the bottom of the water, and are thus measured with each earth and sand thickness measuring instrument. Based on the difference between the first output signal indicating the generated pressure and the second output signal, the thickness of the sediment deposited above each sediment thickness measuring instrument from the start of measurement or eroded The thickness of the earth and sand is calculated. By installing a plurality of earth and sand thickness measuring instruments at predetermined intervals along the water bottom surface, it becomes possible to measure the thickness of sediment or eroded earth and sand on the water bottom surface in a predetermined area when desired.

The sand drift observation system according to claim 7 is the sand drift observation system according to claim 6,
A plurality of the earth and sand thickness measuring devices are installed at a first interval from the coast toward the offshore side, and a plurality of the sand and sand thickness measuring devices are installed at a second interval along the coast, and the arithmetic unit is an observation installed on the land. It is provided in the station.
Here, the 1st space | interval which goes to the offshore side from a coast is arbitrary distance intervals, for example, in the case of a coast, it is 5-10 [m]. Moreover, the 2nd space | interval along a coast is arbitrary distance intervals, for example, in the case of a coast, it is 10-20 [m].

  According to this configuration, the plurality of sediment thickness measuring instruments are installed at the first interval from the coast to the offshore side, and are installed at the second interval along the coast. It is possible to measure the thickness of sediment deposited on the bottom of the water or the thickness of eroded sediment from the beginning of measurement and observe the distribution of sediment on the bottom of the area. It becomes. Sediment data of the calculation device calculated based on the output signals from the sediment thickness measuring instruments provided at various locations on the bottom of the water can be remotely observed at an observation station on land.

  According to the bottom sediment thickness measuring apparatus according to claim 1 of the present invention, the fine grain pressure gauge and the soil material pressure gauge are measured in a state where they are buried in the bottom of the water, so that the sea, rivers, lakes, dam lakes, etc. Measure the thickness of sediment deposited on the bottom of the water, measure the thickness of sediment deposited or eroded on the bottom of the water in the event of a flood or stormy weather, etc. Etc. can always be measured efficiently without being influenced by the weather.

  According to the bottom sediment thickness measuring apparatus according to claim 2 of the present invention, the fine-grain pressure gauge is provided with a filter that allows the fine-grained sediment sand and water in the sediment to pass therethrough, so Pressure due to granulated sediment and water can be accurately detected.

  According to the bottom sediment thickness measuring apparatus according to claim 3 of the present invention, the soil material pressure gauge has the soil material from the clearance by installing the cover body through the clearance above the soil material sensor housing. Since the earth and sand flows into the sensor casing and presses the earth material sensor part, the pressure due to the earth material and sand in the accumulated earth and sand can be accurately detected.

  According to the bottom sediment thickness measuring apparatus according to claim 4 of the present invention, the fine grain pressure gauge and the soil material pressure gauge are buried at a predetermined depth from the bottom of the water by the same pedestal. It is possible to accurately calculate the thickness of the earth and sand accumulated on the bottom surface and the thickness of the eroded earth and sand. Moreover, since the bottom sediment thickness measuring apparatus can be installed on the bottom of the water by fixing the fine grain pressure gauge and the soil material pressure gauge to the bottom of the water on the same pedestal, the number of installation work steps can be reduced.

  According to the bottom sediment thickness measuring apparatus according to claim 5 of the present invention, the difference between the second output signal and the first output signal is the difference between the constant rate correction coefficient of the solid-liquid mixed phase portion and the weight per unit volume of water. The result of dividing by can be accurately calculated as the thickness of the sediment deposited on the bottom of the water.

According to the sand drift observation system according to claim 6 of the present invention, the plurality of earth and sand thickness measuring instruments are embedded at a predetermined depth from the bottom of the water and installed at predetermined intervals along the bottom of the water. Thus, it becomes possible to grasp the distribution state and dynamics of the bottom sediment in a predetermined area when desired.
As a result, the drift sand observation system is capable of measuring changes in sediment thickness during stormy weather, time-series changes in which the thickness of the sediment increases and decreases, changes in riverbed and seafloor topography due to sediment flow and drift sand, In addition, it is possible to observe changes in coastal topography at any time as desired, and it is also possible to predict the thickness of drifting sand. Therefore, it is possible to exert an effect in disaster prevention measures at the time of flooding and coastal erosion measures at the time of waves.

According to the sand drift observation system according to claim 7 of the present invention, the thickness of the sediment deposited on the bottom of the water or the thickness of the eroded sediment is measured by the observation station installed on the land, thereby measuring the sediment thickness. It is possible to remotely observe the distribution of sediment on the bottom, changes in river bed topography, coastal erosion and shallow shape in the area where the vessel is located. As a result, once the earth and sand thickness measuring instrument is installed at the bottom of the water, the thickness of the earth and sand deposited on the bottom of the water can be measured at any time without being influenced by the weather.
In addition, it is possible to observe and monitor the shape of rivers, dam lakes, estuaries and sea coastlines, and the shape of the bottoms of those coasts as needed, which is effective for flood damage countermeasures.

Next, a bottom sediment thickness measuring apparatus and a drift sand observation system according to an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a schematic diagram showing a bottom sediment thickness measuring apparatus and a drift sand observation system. 2A and 2B are diagrams showing a bottom sediment thickness measuring apparatus and a drift sand observation system, in which FIG. 2A is a schematic diagram showing an installation state when installed in the sea, and FIG.

≪Configuration of sand drift observation system≫
As shown in Fig. 1, earth and sand move from the hillside slope of the uppermost stream of the river to the sand drifting area of the coast due to floods, etc. The thickness of the earth and sand has fluctuated. The drift sand observation system S is used to measure the thickness H1 (see Fig. 2) of the sediment deposited on the bottom of the predetermined area of the sea, rivers, lakes, dam lakes, etc. This is a system for comprehensively remotely observing the thickness H2 (see FIG. 2) or the like by wire or wireless.

As shown in FIG. 1, the drift sand observation system S is disposed on a sabo dam, a dam lake, a river, the sea, or the like where erosion or accumulation is expected, and the thicknesses H1 and H2 of the earth and sand (see FIG. 2) are set. Each observation station 2, 2A, 2B, 2C in which equipment for transmitting data of each bottom sediment thickness measurement apparatus 1 to be observed and data of each bottom sediment thickness measurement apparatus 1 is installed, and each observation station 2, 2A, And an observation base station 3 that aggregates data from 2B and 2C.
In this drift sand observation system S, data such as sediment measured by each bottom sediment thickness measuring device 1 described later installed in various places is sent from the bottom sediment thickness measuring device 1 to the observation stations 2, 2A, 2B, 2C. After that, the data is sent to the observation base station 3 and managed, so that the data of the earth and sand (flowing sand and drifting sand) of the observation base stations 3 in various places can be observed by monitoring of the data processing device 31. In addition to this, the drift sand observation system S includes a wave height meter (not shown) for measuring waves and a direction meter (not shown) for detecting the direction of water flow in order to make it possible to predict sediment accumulation or erosion. In addition, an anemometer (not shown) that measures the flow velocity of water is also installed and provided in various places.

  The bottom sediment thickness measuring apparatus 1 and the drift sand observation system S according to the present invention can measure the thickness of sediment and eroded sediment on all bottoms of the sea, rivers, lakes and dam lakes. An example will be described.

The sand drift observation system S includes a fine grain pressure gauge 5 and a soil material pressure gauge 6 which will be described later, and a pedestal 41 on which the fine grain pressure gauge 5 and the soil material pressure gauge 6 are mounted. A plurality of earth and sand thickness measuring instruments 4 that are buried horizontally at a predetermined depth H0 from the (water bottom) and installed at predetermined intervals a, b, and c along the sea bottom, and fine-grain pressure gauges 5 is deposited on the seabed (bottom) surface based on the difference between the first output signal (pressure signal) indicating the pressure measured at 5 and the second output signal (pressure signal) indicating the pressure measured by the soil material pressure gauge 6. A computing device 21 for computing the thickness H1 of the soil or sand that has been eroded or a thickness H2 of the eroded sediment, a cable (signal transmission means) 7 for transmitting a wired signal between the sediment thickness measuring instrument 4 and the computing device 21; It has.
In the sand drift observation system S, the sediment thickness measuring instrument 4 to be described later is arranged at a predetermined interval (first interval) b and a predetermined interval c from the coast to the offshore side, and at a predetermined interval (first step) along the coast. The computing device 21 is provided in the observation station 2 installed on the land, and the earth and sand thickness measuring instrument 4 and the computing device 21 are electrically connected by a cable 7.

In addition, the predetermined space | interval a along the shore (coast) shown in FIG. 1 is 10-20 [m], for example. The earth and sand thickness measuring device 4 is arranged at a predetermined interval a along the coast according to the progress of sediment accumulation on the seabed of the coast and the progress of erosion of the sediment.
The predetermined distances b and c from the coast to the offshore are, for example, 5 to 10 [m], and the distance (predetermined distance b) from the coast to the first sediment thickness measuring instrument 4 toward the offshore is 6 [M], and the predetermined interval c thereafter is 10 [m]. The sediment thickness measuring instrument 4 is installed in a straight line at predetermined intervals b and c from the coast toward the offshore side, such as a coast where sediment or erosion progresses quickly, or a coast where sediment or erosion is expected.

  In this way, in the sand drift observation system S, several sediment thickness measuring instruments 4 are connected to the offshore side from the coast by connecting with the cable 7 at predetermined intervals b and c, and desired at a predetermined interval a along the coastline. Are connected by a cable 7 for a distance of. As a result, in the drift sand observation system S, the thickness H1 of the sediment deposited in the seabed area after the sediment thickness measuring instrument 4 is installed and the thickness H2 of the eroded sediment are measured at predetermined intervals a, b, c. It is installed so that the distribution of sediment on the seabed in the area can be observed.

  As shown in FIG. 2, in the sand drift observation system S, each sediment thickness measuring instrument 4 is set by being embedded at a predetermined depth H0 from the sea bottom. The predetermined depth H0 is, for example, 0.5 to 1 [m] when the sea bottom is formed of a layer of soil material earth and sand. In the case of bedrock, it is 0 [m].

FIG. 3 is a table showing particle size classification names according to the Japanese unified soil classification method.
As shown in FIG. 3, the fine-grained soil is sand (fine-grained) having a particle size of 74 [μm] or less. The soil material earth and sand refers to sand (soil material) having a particle size of 75 [mm] or less including finely divided soil.

≪Configuration of bottom sediment thickness measuring device≫
As shown in FIG. 2, the bottom sediment thickness measuring apparatus 1 is configured to measure the thickness H1 of sediment deposited on the seabed (water bottom) surface from the start of measurement (reference time), and the thickness of eroded sediment on the bottom of the sea. The pressure difference measured by the fine particle pressure gauge 5 and the soil material pressure gauge 6 embedded in the vicinity of each other on the bottom of the water is added to the constant constant correction coefficient set in advance for the solid-liquid mixed phase portion of water and earth and sand. It is a measuring device which calculates by dividing by the difference with the weight per unit. This bottom sediment thickness measuring apparatus 1 is embedded horizontally at a predetermined depth H0 from the bottom of the sea (bottom of the sea), and is based on a solid-liquid mixed phase portion of fine-grained sediment and water in the sediment deposited on the bottom of the sea. A fine-grained pressure gauge 5 for measuring pressure, and a soil material in the earth and sand deposited horizontally on the bottom of the seabed where the fine-grained pressure gauge 5 is embedded horizontally at the same depth The soil material pressure gauge 6 for measuring the pressure of the solid-liquid mixed phase with water, the first output signal (pressure signal) indicating the pressure measured by the fine particle pressure gauge 5 and the soil material pressure gauge 6 were measured. And an arithmetic unit 21 for calculating the thicknesses H1 and H2 of the earth and sand deposited on the sea bottom based on a difference from a second output signal (pressure signal) indicating pressure.

≪Configuration of observation station≫
As shown in FIGS. 1 and 2, the observation station 2 is provided with, for example, a computing device 21 connected to each earth and sand thickness measuring instrument 4 arranged on the seabed in a predetermined area on the coast by a cable 7. It is an observation facility. This observation station 2 is installed on the land near the seabed where the earth and sand thickness measuring instrument 4 is installed. The observation station 2 includes an arithmetic unit 21, a power supply device (not shown) for supplying power to each sediment thickness measuring instrument 4 and the like, and radio wave transmission means for transmitting data to the observation base station 3 described later ( (Not shown) etc. are installed so that the earth and sand thickness measuring instrument 4 can be remotely observed.
In the observation station 2, since the computing device 21 is connected to each sediment thickness measuring instrument 4 by the cable 7, power is constantly supplied from the power source in the observation station 2 to the sediment thickness measuring instrument 4 and continuously. Can be observed.

<Configuration of arithmetic unit>
The arithmetic unit 21 calculates the thickness of sediment deposited based on the difference between the first output signal from the fine grain pressure gauge 5 of each sediment thickness measuring instrument 4 and the second output signal from the soil material pressure gauge 6. This is a device that calculates H1 or the thickness H2 of the eroded earth and sand and outputs the calculated thickness of the earth and sand to a display device (not shown). In this computing device 21, the result of dividing the difference between the second output signal and the first output signal by the difference between the constant rate correction coefficient of the solid-liquid mixed phase portion and the weight per unit volume of water is sediment deposited on the sea floor. Of thickness. The earth and sand data calculated by the arithmetic unit 21 is transmitted to the observation base station 3.
For example, the thickness of the deposited sediment H1, fine fraction manometer 5 and ΔP the difference in pressure measured with a soil material pressure gauge 6, when a fixed-rate correction coefficient and gamma _a, the thickness H1 of the deposited sediment ,
H1 = ΔP / (γ _a −1)
It is.

<Configuration of observation base station>
As shown in FIG. 1, the observation base station 3 aggregates, digitally records, and monitors data sent from the observation stations 2, 2A, 2B, and 2C provided in various places by means of radio wave transmission means. It is a facility that includes a data processing device (personal computer) 31 that observes the sediment thickness. In this observation base station 3, in addition to the thickness of the seabed sediment or eroded earth and sand, high wave observation, wave direction observation, seawater flow direction, seawater flow velocity observation, etc. .

  4A and 4B are diagrams showing the earth and sand thickness measuring instrument, in which FIG. 4A is a perspective view and FIG. 4B is a plan view showing a state when the base is removed.

≪Configuration of earth and sand thickness measuring instrument≫
As shown in FIGS. 4 (a) and 4 (b), the earth and sand thickness measuring instrument 4 includes the fine particle pressure gauge 5, the earth material pressure gauge 6, the fine particle pressure gauge 5, and the earth material pressure gauge. 6 and a pedestal 41 for embedding both of them at a predetermined depth H0 (see FIG. 2) from the sea bottom. When this earth and sand thickness measuring instrument 4 is installed on the seabed, a fine particle pressure gauge 5 and a soil material pressure gauge 6 are installed in a pair on a pedestal 41 made of the same member, and the pedestal 41 is placed on the seabed. Then, a hole having a predetermined depth H0 is dug, and is embedded horizontally in the bottom of the same hole (see FIG. 2).

  The pedestal 41 is a plate member for fixing the fine grain pressure gauge 5 and the soil material pressure gauge 6 at the same depth H0 from the sea bottom. keeping. The pedestal 41 is made of, for example, a metal plate member having corrosion resistance such as stainless steel, and is made of a disk-shaped member having a diameter of 120 [mm] and a thickness of about 2 [mm].

In the present embodiment, a single common substrate 42 is interposed between the pedestal 41 and the fine particle pressure gauge 5 and the soil material pressure gauge 6. Although the example in the case of holding the soil material pressure gauge 6 has been given, the substrate 42 may be a dedicated substrate separately provided on the lower surface of the fine particle pressure gauge 5 and the soil material pressure gauge 6. The base 41 may share the role of the substrate 42.
Further, the pedestal 41 may be fixed in the seabed using an anchor or the like as appropriate according to the condition of the seabed sediment where the sediment thickness measuring instrument 4 is embedded. When the seabed is bedrock, anchors or the like are driven into the bedrock and the pedestal 41 is fixed.

  As shown in FIGS. 4A and 4B, the substrate 42 is a bottom plate member on which the fine particle sensor housing 51 of the fine particle pressure gauge 5 and the column 63 of the soil material pressure gauge 6 are mounted. It is a member that fulfills the role and the role of the wiring board for mounting the fine grain sensor unit 53 and the soil material sensor unit 61 to connect to the cable 7 (see FIG. 2). The substrate 42 is made of a metal insulated wiring substrate such as an enamel substrate having an insulating layer disposed on the upper surface to which the fine grain sensor unit 53 and the soil material sensor unit 61 are bonded. On the insulating layer of the substrate 42, a fine particle sensor unit 53, a soil material sensor unit 61, and a conductive foil (not shown) for electrical connection to the cable 7 are fixed. The substrate 42 is made of, for example, a rectangular flat plate material having a length of 50 [mm], a width of 100 [mm], and a thickness of 2 [mm]. On the upper surface of the substrate 42, the fine particle sensor unit 53 and the soil material sensor unit 61 are arranged at an interval of 65 [mm]. The board | substrate 42 is being fixed to the base 41 with the screw member, for example.

≪Configuration of fine grain pressure gauge≫
FIG. 5 is an enlarged longitudinal sectional view in the direction of arrow XX in FIG.
As shown in FIG. 5, the fine particle pressure gauge 5 is a hollow fine pressure gauge having an inlet 51a through which the earth and sand present at the position where the fine particle pressure gauge 5 is embedded and water in the earth and sand. A fine particle sensor housing 51, a filter 52 provided in the fine particle sensor housing 51, for passing water flowing into the fine particle sensor housing 51 and fine fine particle sediment in the earth and sand, A fine particle sensor unit 53 that is installed below the filter 52 in the particle sensor housing 51 and detects the pressure due to the water and fine particle soil that has passed through the filter 52, and the fine particle sensor unit 53, And a substrate 42 on which a fine particle sensor housing 51 is mounted.

As shown in FIGS. 4 (a), 4 (b) and 5, the fine particle sensor housing 51 is a housing having a hollow portion 51b for installing a filter 52 and a fine particle sensor portion 53. For example, it is made of a metal having corrosion resistance such as stainless steel. The fine particle sensor housing 51 has an opening of a hollow portion 51b on the lower surface and is formed in a state in which the upper surface is closed, and has inlets 51a communicating with the hollow portion 51b at four positions on the upper side, front, rear, left and right. It is drilled.
The inflow port 51a is a hole drilled so that fine-grained sediment and water can pass through, and has a diameter of 1.0 [mm], for example.
The opening of the hollow portion 51b is blocked by the substrate 42 so as to cover the fine particle sensor portion 53 with the fine particle sensor portion 53 as the center. The fine particle sensor housing 51 is fixed to the substrate 42 by screwing a plurality of locations on the lower end surface to the substrate 42.

  As shown in FIG. 5, the filter 52 is made of, for example, a mesh-like metal filter having a mesh of 0.05 [mm], and between the inlet 51 a in the hollow portion 51 b and the fine particle sensor unit 53. Fixed.

  The fine grain sensor unit 53 is a sensor that outputs an electric resistance value that is changed by a minute change (strain) in mechanical dimensions by being pressed by the water and fine granule sand that have passed through the filter 52. The strain gauge is fixed on the substrate 42. The fine particle sensor unit 53 is made of a metal material resistor. The metal material forming the fine particle sensor unit 53 has a resistance value unique to the metal, and when an external tensile force (compression force) is applied, the metal material expands (shrinks) and the resistance value increases (decreases). It is like that.

For example, when R is a specific resistance value of a metal material, ΔR is a resistance value changed when strain is applied to the metal material, and Ks is a cage rate representing sensitivity of the strain cage.
ΔR / R = Ks
There is a relationship.

≪Configuration of soil material pressure gauge≫
FIG. 6 is an enlarged longitudinal sectional view in the direction of arrow YY of FIG.
As shown in FIGS. 4 (a), 4 (b), and 6, the soil material pressure gauge 6 includes a soil material sensor unit 61 that detects pressure caused by water and the soil material soil in the soil, and the soil material sensor. A cover body disposed on the portion 61 with a gap 64 through which the soil material earth and sand in the earth and sand existing at the position where the soil material pressure gauge 6 is embedded and the water in the soil material earth and sand are interposed. 62, a substrate 42 on which the soil material sensor unit 61 is mounted, and a space 65 that is interposed between the substrate 42 and the cover body 62 so that the soil material soil and water can enter and exit from the outside. And a plurality of columns 63.

  The soil material sensor unit 61 is a sensor that outputs an electrical resistance value that is changed by a minute change (strain) in mechanical dimensions when pressed by the water flowing into the cover body 62 and the soil material earth and sand. The strain gauge is fixed on the substrate 42.

  The cover body 62 is a protective member for covering the upper portion of the soil material sensor unit 61 through the gap 64 so that unnecessary load due to rocks or the like is not applied to the soil material sensor unit 61. For example, the cover body 62 includes four support columns 63. Is supported by. The cover body 62 is made of, for example, a disk-shaped stainless steel plate having a diameter of 25 [mm] and a thickness of 2 [mm].

  A soil material sensor 61 is bonded onto the substrate 42, and columns 63 are erected on the front, rear, left and right sides around the soil material sensor 61.

  The plurality of struts 63 are formed longer than the height of the soil material sensor unit 61, and a space 65 between the substrate 42 and the cover body 62 is constant so that the cover body 62 does not contact the soil material sensor unit 61. It keeps in. The support | pillar 63 consists of a cylindrical member made from stainless steel, for example.

≪Action≫
Next, with reference to FIGS. 1-6, the effect | action of the bottom sediment thickness measuring apparatus 1 and the sand drift observation system S which concern on embodiment of this invention is demonstrated with a work procedure.

<Setting of earth and sand thickness measuring instrument>
When measuring the thickness H1 of the sediment deposited on the bottom of the sea (the bottom of the sea) or the thickness H2 of the eroded sediment, as shown in FIG. Or digging a hole with a predetermined depth H0 on the seabed in an area where the terrain of the coastline may be deformed, and setting the earth and sand thickness measuring instrument 4 and the cable 7 back to the original state.

  In this case, as shown in FIG. 1, after a predetermined interval (second interval) a along the coast and a predetermined interval b from the coast to the offshore side, a constant predetermined interval (first interval) c. An appropriate number of sediment thickness measuring instruments 4 are arranged linearly toward the offing. By arranging a large number of earth and sand thickness measuring instruments 4 in a grid pattern in this way, the thicknesses H1 and H2 of the changed earth and sand from the start of measurement over a wide range of the sea floor near the coast and the changed sea bottom It becomes possible to grasp the shape. Each earth and sand thickness measuring instrument 4 is connected to the computing device 21 of the observation station 2 by a cable 7 wired in the seabed and on the land.

  As shown in FIG. 5, the fine-grain pressure gauge 5 when it is set is buried in the ground of the seabed, so that sediment is deposited on the fine-grain sensor housing 51 and the inlet 51a. The fine-grained sediment and seawater in the earth and sand enter the hollow part 51b, and the earth and sand that have been in the hollow part 51b until now are pushed out from the other inflow port 51a by the earth and sand, Fine-grained sediment and seawater having a particle size of 50 [μm] or less pass through the filter 52 and press the fine-grain sensor unit 53. The first output signal of the pressure measured by the fine particle pressure gauge 5 at the time of setting is transmitted to the computing device 21 via the cable 7 and is used as a reference pressure signal of the fine particle pressure gauge 5.

As shown in FIG. 6, when the soil material pressure gauge 6 is set, the soil material is deposited on the cover body 62 by being buried in the ground of the seabed, and the soil material in the soil from the space 65. Sediment and seawater flow into the soil material sensor unit 61, and the soil and sand that have been in the space 65 until now are pushed out by the soil that has flowed in, and the soil material and sand and seawater pass through the soil material sensor unit 61. It is in a pressed state. The second output signal of the pressure measured by the soil material pressure gauge 6 at the time of setting is transmitted to the computing device 21 via the cable 7 and used as a reference pressure signal of the soil material pressure gauge 6.
Thus, when the embedding of all the earth and sand thickness measuring instruments 4 and the connection by the cables 7 are completed, and the fine particle pressure gauge 5 and the soil material pressure gauge 6 are initially set, the thickness and thickness of the earth and sand are measured and monitored. Is possible. Once the earth and sand thickness measuring instrument 4 and the cable 7 are installed on the seabed, the measurement can be performed as many times as desired without depending on the weather.

<Measurement of sediment thickness using a submarine sediment thickness measurement system and drift sand observation system>
Then, the measurement of the thickness of the sediment by the bottom sediment thickness measuring apparatus 1 and the drift sand observation system S which concern on embodiment of this invention is demonstrated.
After the embedding of the sediment thickness measuring instrument 4, the sediment on the sea floor is washed away by waves and ocean currents, and sediment is deposited or eroded on the sea floor on the sediment thickness measuring instrument 4 installed in the seabed. Move. Moreover, on the coast, the fluctuation of the earth and sand at a point of 5 to 10 [m] on the beach is large due to the waves approaching the coast, and the earth and sand may be washed off by the waves.

For example, as shown by phantom lines in FIG. 2, when sediment H1 having a thickness H1 is deposited on the sea bottom on the sediment thickness measuring instrument 4 after the start of measurement, the fine grain sensor of the fine grain pressure gauge 5 The part 53 is loaded with pressure by finely divided sediment and seawater that has passed through the inlet 51a (see FIG. 5A) and the filter 52, and this pressure indicates an output signal (first output signal) indicating an electric resistance value. Is output to the arithmetic unit 21.
On the other hand, the soil material sensor 61 of the soil material pressure gauge 6 is loaded with the pressure of the soil material earth and sand flowing into the gap 64 from the space 65 (see FIG. 5B), and this pressure has an electrical resistance value. To the output signal (second output signal) shown in FIG.

  In the arithmetic unit 21, the difference between the measured pressure values is obtained from the first output signal from the fine grain pressure gauge 5 and the second output signal from the soil material pressure gauge 6, and the sediment thickness measuring instrument 4 is calculated based on this difference. The thickness H1 of the earth and sand deposited on the sea bottom above is calculated. Then, as shown in FIG. 2, when the earth and sand thickness H0 is reduced to H2 and eroded, it can be calculated based on the set pressure value (initial value) at the start of measurement.

In this way, the sediment thickness measuring instrument 4 measures the sediment thickness H1 during normal times or during floods by continuously measuring the accumulated sediment thickness H1 and the eroded sediment thickness H2 in time series. It is possible to observe fluctuations in the thicknesses H1 and H2 of the earth and sand deposited on the sea bottom above the vessel 4 and the eroded earth and sand.
The sediment thickness data and ocean current data are aggregated in time series and analyzed by computer to predict sediment movement, prediction of seafloor topography fluctuations, and eroded beaches. It is possible to predict the topography of the terrain.

≪Modification≫
The present invention is not limited to the above-described embodiment, and various modifications and changes can be made within the scope of the technical idea. The present invention extends to these modifications and changes. Of course.

FIG. 12 is a schematic diagram illustrating a case where the bottom sediment thickness measuring apparatus and the drift sand observation system according to the embodiment of the present invention are used for a river or a lake.
For example, in the above-described embodiment, the case has been described in which the bottom sediment thickness measuring apparatus 1 and the drift sand observation system S measure and observe the thickness of sediment deposited or eroded on the sea bottom. The drift sand observation system S is not limited to this, and as shown in FIG. 12, it can also be used as an apparatus for measuring and observing the thickness of sediment deposited on the bottom surface of a river or a lake or the thickness of eroded sediment. .

  In this case, as shown in FIG. 12, the earth and sand thickness measuring instrument 4 has a predetermined soil material earth and sand between the sludge made of clay or silt deposited on the bottom of the water and the rocky material (or rock mass). Embed in the depth position. Even in this way, the thickness H1 of the earth and sand deposited on the water bottom and the thickness (H2) of the eroded earth and sand can be measured in the same manner as in the above embodiment.

  Moreover, in the above-described embodiment, the case where each sediment thickness measuring instrument 4 and the computing device 21 are connected by the cable 7 has been described. However, the bottom sediment thickness measuring apparatus 1 and the sand drift observation system S are not limited to this, A transmitter may be installed in the earth and sand thickness measuring instrument 4, and an output signal of the pressure measured by the fine particle pressure gauge 5 and the soil material pressure gauge 6 may be transmitted to the arithmetic device 21 wirelessly.

  In the above-described embodiment, the fine particle sensor unit 53 of the fine particle pressure gauge 5 and the soil material sensor unit 61 of the soil material pressure gauge 6 illustrated in FIG. 4 are sensors that measure pressure. For example, a sensor for detecting a load may be used.

Next, an embodiment of the bottom sediment thickness measuring apparatus according to the present invention will be described with reference to FIGS.
FIG. 7 is a perspective view showing a test instrument.

≪Test equipment configuration≫
A test instrument 8 shown in FIG. 7 includes an acrylic transparent bottomed cylindrical column shaped container 81 and the earth and sand thickness measuring instrument 4A described in the above embodiment. On the inner bottom of the container 81, a sediment thickness measuring instrument 4A on which a fine particle pressure gauge 5 and a soil material pressure gauge 6 are mounted is fixed.

In the experiment, a vinyl chloride tube having a height of 3250 [mm], an inner diameter of 119.2 [mm], and an outer diameter of 127.0 [mm] is used as the container 81, and water and earth and sand are put into the container 81. successively introduced to obtain the difference between the measured value of the measurement values of soil material pressure gauge 6 (W ₂₎ and the fine fraction manometer 5 of the measuring value (W ₁₎ (pressure difference). In the experiment, the correlation between the difference between the measured values (W ₂ −W ₁ ) and the thickness of the accumulated earth and sand (h ₃ ), that is, the thickness of the solid-liquid mixed phase portion C due to water and earth and sand, The value was obtained from the experimental value B by 81 scale plate 82 and the calculated value J by calculation described later.

In this experiment, No. 2 silica sand (average particle size (d ₅₀ ) is 2.2 [mm]), No. 3 silica sand (average particle size (d ₅₀ ) is 1.3 [mm]), 4 No. silica sand (average particle size (d ₅₀ ) was 1.1 [mm]) and No. 6 silica sand (average particle size (d ₅₀ ) was 0.49 [mm]), respectively.
I will explain one of the experiments with No. 6 silica sand. In the experiment at that time, water having a temperature of 11.9 ° C., a water temperature of 11.0 ° C., and a weight of 158.83 [g] was poured into the container 81, and the weight before charging was 250. 74 was charged with silica sand of [g] in the container 81, after the sequence of sediment particles containers 81 shake 25 times (void ratio) was dense state, the height h ₃ of the deposited sediment was measured. At this time, the height h ₃ (experimental value B) of the accumulated earth and sand measured with the scale plate 82 was 18.9 [cm], and the change in the water level was 9.2 [cm]. In the experiment, the experimental value B and the calculated value J of the height h ₃ of the deposited earth and sand were obtained by changing the amount of the silica sand and the average particle diameter (d ₅₀ ) of the silica sand in this way.

≪Explanation of constant rate correction coefficient≫
For example, the measured value of the fine grain pressure gauge 5 (pressure signal of mixing of water and fine grained sediment) is W ₁ , and the measured value of the soil material pressure gauge 6 (water and soil material earth and sand (fine grained sand and coarse sand and coarse sand) W ₂ ), the depth [mm] from the water surface to the fine-grain pressure gauge 5 and the soil material pressure gauge 6, h ₁ , the depth of the water supernatant B The depth [mm] is h ₂ , the depth [mm] of the solid-liquid mixed phase portion C of the accumulated earth and sand, that is, water and earth and sand is h ₃ , the weight per unit volume of water is γ _W , and the solid and liquid by water and earth and sand If the fixed-rate correction coefficient of the mixed phase portion C and gamma _a following equation holds.

W ₁ = h ₁ γ _W
W ₂ = h ₂ γ _W + h ₃ γ _a
The fine fraction manometer 5 measured value W ₁ and the difference between the measured value and the measured value W ₂ of the soil material the pressure gauge 6 (pressure difference) W ₂ -W ₁ is
W ₂ −W ₁ = h ₂ γ _W + h ₃ γ _a −h ₁ γ _W
= H ₂ γ _W + h ₃ γ _a − (h ₂ + h ₃ ) γ _W
= H ₂ γ _W + h ₃ γ _a -h ₂ γ _W -h ₃ γ _{W
= H 3 γ a -h 3 γ} W
= H ₃ (γ _a −γ _W )
Here, γ _w = 1.0, and if this is substituted,
W ₂ −W ₁ = h ₃ (γ _a −1.0)
Therefore, the thickness h ₃ of the accumulated earth and sand is
h ₃ = (W ₂ −W ₁ ) / (γ _a −1.0)

In other words, the depth h ₃ of the solid-liquid mixed phase portion C by water and sediments, the difference W ₂ -W ₁ between the measured value W ₁ of the measured value W ₂ and the fine fraction manometer 5 of soil material manometer 6 It can be calculated by the constant rate correction coefficient γ _a of the solid-liquid mixed phase portion C due to water and earth and sand.

When the constant rate correction coefficient γ _a is obtained,
γ _a = (W ₂ −W ₁ ) / h ₃ +1
It becomes. That is, fixed-rate correction coefficient gamma _a solid-liquid mixed phase portion C by water and sediment, the difference W ₂ -W ₁ between the measured value W ₁ of the measured value W ₂ and the fine fraction manometer 5 of soil material manometer 6 And by calculating the depth h ₃ of the solid-liquid mixed phase portion C due to water and earth and sand.

Figure 8 shows the data of the experiments with No. 6 silica sand, and the difference W ₂ -W ₁ with (a) is the measured value W ₁ of the measured value W ₂ and the fine fraction manometer soil material pressure gauge, is a graph showing the relationship between the depth h ₃ of the solid-liquid mixed phase portion by the water and sediment, is a table of (b) is (a). Figure 9 shows the data of the experiments with No. 3 silica sand, and the difference W ₂ -W ₁ with (a) is the measured value W ₁ of the measured value W ₂ and the fine fraction manometer soil material pressure gauge, is a graph showing the relationship between the depth h ₃ of the solid-liquid mixed phase portion by the water and sediment, is a table of (b) is (a).

When No. 6 silica sand was tested with the test device 8, data as shown in FIGS. 8 (a) and 8 (b) was obtained. Thus, soil material pressure gauge 6 of the measured value W ₂ and the fine fraction manometer 5 measured value W ₁ and the difference W ₂ -W ₁ solid-liquid mixed phase portion C by the water was measured by calculating the sediment in The depth h ₃ (calculated value J) of the liquid and the depth h ₃ (experimental value B) of the solid-liquid mixed phase portion C of water and earth and sand visually measured by the scale plate 82 of the container 81 in the experiment are substantially the same. ing.

In the same manner, when No. 2 silica sand, No. 3 silica sand and No. 4 silica sand were tested with the test equipment 8, data substantially the same as the data shown in FIGS. 8 (a) and (b) was obtained. It was. For example, in the case of No. 3 silica sand, as shown in FIGS. 9A and 9B, the depth h ₃ of the solid-liquid mixed phase portion C is almost equal to the experimental value B by the scale plate 82 and the calculated value J. Match.
Therefore, the soil material pressure gauge 6 of the measured value W ₂ and the fine fraction manometer 5 measured value W ₁ Metropolitan of sediment deposited on the water bottom thickness H1 (see FIG. 2 and FIG. 12) and eroded soil Thickness H2 (see FIG. 2) can be measured.

10, and the fixed-rate correction coefficient gamma _a solid-liquid mixed phase portion C by a sand water obtained in experiments, the soil material the pressure gauge 6 measured value W ₂ and fine fraction manometer 5 between the measured value W ₁ it is a graph showing the relationship between the difference W ₂ -W ₁ depth h ₃ of the solid-liquid mixed phase portion C by and the sediment water measured by calculating at.

As shown in FIG. 10, the constant rate correction coefficient γ _a of the solid-liquid mixed phase portion C due to water and earth and sand is always constant even when the depth h ₃ of the solid-liquid mixed phase portion C due to water and earth and sand changes. 1.1.

≪Description of fine grain pressure gauge and soil material pressure gauge≫
In the sediment under the water, pore fluid exists in the gaps of the skeleton created by the soil particles. In the earth and sand of the groundwater zone, the soil gap is saturated with pore water, and the pore water exists in a continuous state due to the capillary water phenomenon. As long as the static water is continuous with each other, it shows a static water distribution in which no water flows, regardless of how they are connected. Therefore, when the water pressure at which pore water is working is the pore water pressure (also referred to as osmotic water pressure) u, the weight per unit volume of water is γ _W, and z is the depth, the pore water pressure u is
u = γ _W z (z <0)
Then, a straight line distribution is formed.

In the fine-grain pressure gauge 5, it was confirmed that the measured values of the pressure of water and fine-grained sediment (from water molecules to a particle size of about 50 [μm]) match the scale of the scale plate 82 of the container 81. It was.
The soil material pressure gauge 6 measures the weight in water in the solid-liquid mixed phase portion C of water and the soil material soil.

In the seabed, the value of the gap ratio e of the earth and sand deposited on the bottom of the sea due to seawater pressure, flow and waves is in the most dense state.
In this experiment, when sand and water were mixed in the container 81 and vibration was sufficiently applied, the value of the sand gap ratio e became the most dense.

The specific gravity Gs of the soil particles is defined by the following equation, where γ _W is the weight per unit volume of water and γ _S is the weight of the soil particles.
G _S = γ _S / γ _W

FIG. 11 is a table showing specific gravity values of each mineral particle and each soil particle.
There are sediments made of various minerals on the bottom of the sea. However, as shown in FIG. 11, the specific gravity of each mineral is approximately 2.3 to 2.86, and the value of the specific gravity Gs of the soil particles hardly changes depending on the type of mineral. It has little effect on the measurement of the thickness of sediment deposited and eroded sediment.

From the above, the thickness of various sediments (depth h ₃ of the solid-liquid mixed phase C due to water and sediment) deposited on the bottom of the sea such as the seabed and lake bottom is measured by the soil material pressure gauge 6. ₂ and the measured value W ₁ of the fine particle pressure gauge 5 (pressure difference) W ₂ −W ₁ and the constant rate correction coefficient γ _a of the solid-liquid mixed phase portion C due to water and earth and sand are accurately calculated in any case. I understand that I can do it.

It is a schematic diagram which shows a bottom sediment thickness measuring apparatus and a drift sand observation system. It is a figure which shows a bottom sediment thickness measuring apparatus and a drift sand observation system, (a) is a schematic diagram which shows the installation state when installing in the sea, (b) is the A section enlarged view. It is a table | surface which shows the classification name of the particle size by Japan unified soil classification method. It is a figure which shows an earth-and-sand thickness measuring device, (a) is a perspective view, (b) is a top view which shows a state when removing a base. FIG. 5 is an enlarged longitudinal sectional view in the direction of the arrow XX in FIG. 4. FIG. 5 is an enlarged longitudinal sectional view in the direction of arrow line YY in FIG. 4. It is a perspective view which shows a test instrument. Those due 6 silica sand No. shows the data of the experiment, (a) represents the difference W ₂ -W ₁ between the measured value W ₁ of the measured value W ₂ and the fine fraction manometer soil material pressure gauge, water and sediment is a graph showing the relationship between the depth h ₃ of the solid-liquid mixed phase portion by a table of (b) is (a). 3 shows the data of the experiments with silica sand, and the difference W ₂ -W ₁ with (a) is the measured value W ₁ of the measured value W ₂ and the fine fraction manometer soil material pressure gauge, due to the water and sediment is a graph showing the relationship between the depth h ₃ of the solid-liquid mixed phase portion, is a table of (b) is (a). Based on the constant rate correction coefficient of the solid-liquid mixed phase part obtained by the experiment with water and earth and sand, and the water and earth and sand measured by calculating the pressure difference between the measured value of the soil material pressure gauge and the measured value of the fine grain pressure gauge It is a graph which shows the relationship with the depth of a solid-liquid mixed phase part. It is a table | surface which shows the value of specific gravity of a mineral particle and a soil particle. It is a schematic diagram which shows the case where the bottom sediment thickness measuring apparatus and drift sand observation system which concern on embodiment of this invention are used for a river or a lake.

Explanation of symbols

1 Underwater sediment thickness measuring device 2, 2A, 2B, 2C Observation station 4, 4A Sediment thickness meter 5 Fine grain pressure gauge 6 Soil material pressure gauge 7 Cable (signal transmission means)
DESCRIPTION OF SYMBOLS 21 Arithmetic unit 41 Base 42 Substrate 51 Fine particle sensor housing 51a Inlet 52 Filter 53 Fine particle sensor unit 61 Soil material sensor unit 62 Cover body 63 Support column 64 Space 65 Clearance a Predetermined interval (second interval)
c Predetermined interval (first interval)
C Solid-liquid mixed phase S Sediment observation system H0 Predetermined depth H1 Thickness of accumulated sediment H2 Thickness of eroded sediment

Claims (7)

In the bottom sediment thickness measuring device that measures the thickness of sediment deposited on the bottom of the water,
A fine-grain pressure gauge that is buried horizontally at a predetermined depth from the bottom surface of the water and measures the pressure of fine-grained sediment and water in the sediment deposited on the bottom surface of the water;
Soil material pressure that measures the pressure of soil material and sand in the soil buried horizontally in the vicinity of the same depth position from the bottom of the water where the fine grain pressure gauge is embedded, and deposited on the bottom of the water Total
Based on the difference between the first output signal indicating the pressure measured by the fine particle pressure gauge and the second output signal indicating the pressure measured by the soil material pressure gauge, the sediment accumulated on the water bottom is calculated. An arithmetic unit for determining the thickness;
An underwater sediment thickness measuring device comprising: The fine-grain pressure gauge is a hollow fine-grain sensor having an inlet through which fine-grained sediment in the earth and sand present at the position where the fine-grained pressure gauge is embedded and water in the sediment flows in. A housing,
A filter that is installed in the fine particle sensor housing and allows the fine particle sand and the water in the earth and sand flowing into the fine particle sensor housing to pass through,
A fine-grain sensor unit that is installed below the filter and detects the pressure of the fine-grained sediment that has passed through the filter and the water to generate the first output signal;
A substrate on which the fine particle sensor unit and the fine particle sensor housing are mounted;
The underwater sediment thickness measuring device according to claim 1, comprising: The soil material pressure gauge detects a pressure caused by the soil material earth and sand in the sediment deposited on the bottom surface of the water and the water, and generates a second output signal.
A cover body installed above the soil material sensor section with a gap between the soil material earth and sand in the earth and sand existing at the position where the soil material pressure gauge is buried and the water in the soil material earth and sand flows in. When,
A substrate on which the soil material sensor unit is mounted;
A plurality of struts that are interposed between the substrate and the cover body to form a space through which the soil material soil and water flow into the gap;
The underwater sediment thickness measuring device according to claim 1 or 2, characterized by comprising:   4. The fine particle pressure gauge and the soil material pressure gauge are mounted on a pedestal embedded at a predetermined depth from the water bottom. The bottom sediment thickness measuring device described in the item   The arithmetic unit calculates a difference between the second output signal and the first output signal by a difference between a preset constant rate correction coefficient of a solid-liquid mixed phase portion made of earth and sand and a weight per unit volume of water. The bottom sediment thickness measuring apparatus according to any one of claims 1 to 4, wherein the thickness of sediment deposited on the bottom surface of the water is obtained as a result of the removal. In the drift sand observation system that observes the thickness of sediment deposited on the bottom of the water,
Fine granule pressure gauge that measures the pressure due to fine-grained sediment and water in the sediment deposited on the bottom of the water, and soil material that measures the pressure due to soil and sand in the sediment deposited on the bottom of the water A pressure gauge, and a pedestal on which the fine grain pressure gauge and the soil material pressure gauge are mounted, and are embedded horizontally at a predetermined depth from the water bottom, along the water bottom. A plurality of sediment thickness measuring instruments installed at predetermined intervals,
Based on the difference between the first output signal indicating the pressure measured by the fine particle pressure gauge and the second output signal indicating the pressure measured by the soil material pressure gauge, the sediment accumulated on the water bottom is calculated. An arithmetic unit for determining the thickness;
A signal transmission means for transmitting a wired or wireless signal between the earth and sand thickness measuring instrument and the arithmetic unit;
Drift sand observation system characterized by having. A plurality of the earth and sand thickness measuring devices are installed at a first interval from the coast toward the offshore side, and a plurality of the sand and sand thickness measuring devices are installed at a second interval along the coast,
The sand drift observation system according to claim 6, wherein the arithmetic unit is provided in an observation station installed on land.

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