JP3989633B2 - Riverbed probe - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a riverbed probe for investigating riverbed fluctuations.
[0002]
[Prior art]
It is important for knowing the hydraulic characteristics of the river channel to know the time-dependent positional changes of riverbed materials, that is, stones and gravel on the riverbed (hereinafter referred to as “river bed changes”).
[0003]
For example, the height and strength of a river dike or the thickness and strength of a bridge pier are determined based on riverbed fluctuations.
[0004]
Conventionally, this riverbed variation was obtained based on model tests or survey results of changes in riverbed shape before and after flooding.
[0005]
[Problems to be solved by the invention]
Conventionally, river bed changes have been obtained based on the results of model experiments and riverbed shape changes.
[0006]
However, in the conventional investigation of river bed fluctuations using an indirect method, the actual river bed fluctuations were not necessarily known accurately, and improvements were required.
[0007]
Accordingly, the present invention has been made to solve the above-described conventional problems, and an object thereof is to provide a river bed exploration tool that can know river bed changes closer to reality.
[0008]
[Means for Solving the Problems]
In order to solve the above-described conventional problems, a riverbed exploration tool according to the present invention is a riverbed exploration tool for investigating riverbed fluctuations in a river using a magnetic detection method, and is sized for the riverbed material of the river to be investigated. And a solid body imitating a shape and a permanent magnet embedded in the body, and the total weight of the solid body plus the weight of the permanent magnet is approximately equal to the weight of the riverbed material. It is made of a material having such a specific gravity.
[0009]
That is, the riverbed exploration tool according to the present invention has a permanent magnet embedded in the main body, so that the position can be specified using a magnetic exploration technique, and the solid main body has a total of the weight of the permanent magnet added to the weight. Since it is made of a material having a specific gravity such that the weight is substantially equal to the weight of the riverbed material, the riverbed exploration tool can have a flow resistance similar to that of the riverbed material.
[0010]
The permanent magnet preferably has a rod shape. By making the permanent magnet into a bar shape, it is possible to determine in which direction the riverbed exploration tool is located from the waveform of the magnetic field strength detected when the riverbed is scanned by the magnetic sensor.
[0011]
Moreover, it is preferable that the permanent magnet which has the said rod shape is arrange | positioned so that the major axis direction may be substantially parallel with respect to the elongate direction of the said solid main body. By arranging the rod-shaped permanent magnets so that the axial direction thereof is substantially parallel to the longitudinal direction of the main body, there is no bias in weight distribution, and the movement can be made closer to the actual riverbed material.
[0012]
The solid body is preferably concrete formed from a mold obtained by casting a riverbed material of a river to be investigated. By forming the main body from such a mold, the shape and size of the riverbed exploration tool is almost the same as that of the riverbed material of the surveyed river, and the surface friction coefficient is close to that of the actual riverbed material. The flow resistance can be almost the same as that of the riverbed material of the surveyed river.
[0013]
The concrete is preferably mixed with a colorant from the viewpoint of visibility. This makes it easy to find the riverbed exploration tool with the naked eye even in a cloudy river after flooding.
[0014]
If the length of the solid main body is in the range of 50 mm to 100 mm, it is preferable because it matches the general size of the riverbed material.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a riverbed search tool according to the present invention will be described in detail with reference to FIGS.
[0016]
FIG. 1 is a perspective view showing the structure of the first embodiment of the riverbed exploration tool of the present invention. The riverbed exploration tool 1 includes a main body 1a made of concrete and a metal bar-shaped permanent magnet 1b embedded in the main body 1a.
[0017]
FIG. 2 is a conceptual diagram of river bed exploration using this river bed exploration tool 1.
[0018]
A large number of riverbed exploration tools 1 are placed at the bottom of the river so that both banks of the river to be explored are connected by a straight line. The riverbed exploration tool 1 is caused to flow downstream as indicated by an arrow with the flow of water from the upstream as time elapses. Then, if the magnetic sensor is used so as to traverse the river, the magnetic sensor detects the magnetic field intensity of the magnetism emitted from the riverbed exploration tool 1, so that the position of the riverbed exploration tool 1 can be detected. Therefore, from the detected position of the riverbed exploration tool 1, the riverbed fluctuation, that is, the tendency of movement of the riverbed material can be known. Furthermore, since the position of the riverbed exploration tool 1 is detected by magnetism, the position can be detected even if it is hidden in the sediment of the riverbed, and the exploration is easy.
[0019]
Next, the features of the riverbed probe 1 of this embodiment will be described.
[0020]
The riverbed exploration tool 1 is embedded with a rod-shaped permanent magnet, and the direction of the riverbed exploration tool 1 can be detected by linearly scanning the riverbed with a magnetic sensor.
[0021]
That is, FIG. 3 is a positional relationship diagram between the magnetic sensor and the permanent magnet 1b for explaining the method of determining the orientation of the riverbed exploration tool 1, and FIG. 4 shows the detected magnetic field strength that varies depending on the orientation of the permanent magnet 1b. FIG.
[0022]
As shown in FIG. 3, the direction of the riverbed exploration tool 1 on the riverbed is such that the permanent magnet 1b is positioned vertically (vertical position) or parallel to the scanning direction of the magnetic sensor (parallel position). ) 2 minutes. In the vertical position, the detected magnetic field strength waveform is detected at one peak detected when the center line of the magnetic sensor passes just beside the permanent magnet 1a, as shown in FIG. It has two peaks with small polarity opposite to the above-mentioned peak. On the other hand, at the parallel position, as shown in FIG. 4B, the detected magnetic field strength waveform has two peaks with opposite polarities detected before and after the center line passes right next to the permanent magnet 1a. Have.
[0023]
Therefore, the direction of the riverbed exploration tool 1 with respect to the scanning direction of the magnetic sensor can be determined from the waveform of the magnetic field intensity detected during the linear scanning with the magnetic sensor.
[0024]
Moreover, it is preferable that the permanent magnet 1b which has a rod shape is arrange | positioned so that the axial direction may be substantially parallel with respect to the elongate direction of the main body 1b. With such an arrangement, there is no weight bias, and the riverbed exploration tool can be moved closer to the actual riverbed material.
[0025]
Next, a method for manufacturing the riverbed probe according to this embodiment will be described.
[0026]
As shown in FIG. 5, the production process is roughly divided into riverbed material collection, mold production, and concrete pouring.
[0027]
First, go to the river to be surveyed, actually collect the riverbed material, and make a mold to form the main body from the riverbed material. By forming the main body of the riverbed exploration tool from such a mold, the shape and size thereof are almost the same as those of the riverbed material of the river to be investigated.
[0028]
In this embodiment, basically, a riverbed exploration tool is manufactured by producing a collected riverbed material mold, but from the conventional research and empirical rules, the general shape of the riverbed material is described later. Since the coefficient is obtained, it is actually preferable to select and sample a riverbed material close to this shape factor and mold it.
[0029]
Riverbed materials vary in shape from flat to nearly spherical. In general, the following shape factor (hereinafter referred to as SF) is used to express the shape of the riverbed material. That is, as shown in FIG. 6, the shape factor SF is SF = c / √ (ab) when the length of the riverbed material is a, the medium length is b, and the short length is c. The shape factor SF of the riverbed material subjected to natural friction is in the range of 0.3 to 1.0. In an actual river, a material having a shape factor of about 0.7 is dominant. If the shape factor is too small, it is easily affected by uncertain factors such as meshing with other riverbed materials and water flow direction. Therefore, it is preferable to select and collect a riverbed material whose shape factor SF falls within the range of 0.5 to 1.0.
[0030]
The riverbed material size also varies depending on whether the river to be surveyed is upstream or downstream, or the amount of water in the river, but a representative riverbed material is selected from the river to be surveyed. In view of the size of a general riverbed material, the length is selected and set in the range of 50 mm to 100 mm, but in a rapid river, it may be set to 300 mm or more.
[0031]
The permanent magnet embedded in the main body is a metal bar magnet having a diameter of about 10 mm and has an uneven shape on the surface. This uneven | corrugated | grooved part can make the coupling | bonding of the concrete and magnet mentioned later robust.
[0032]
The length of the permanent magnet is determined according to the length of the riverbed exploration tool, but since the strength of the magnetic field is proportional to the length of the magnet, the magnetic exploration can be efficiently performed by setting the length to at least about 30 mm. .
[0033]
The main body of the riverbed probe is made of concrete. Cement used for concrete is general Portland cement. Since the friction coefficient of the surface of the main body made from concrete is close to that of the actual riverbed material, the flow resistance of the riverbed exploration tool can be made realistic.
[0034]
In order to improve the strength of the main body, the cement is mixed with aggregate, that is, gravel. The average of the long, medium and short lengths of the riverbed probe is about 2mm to 8mm, and the riverbed probe with larger size is less than 1/10 of the average. Standard ones are used.
[0035]
Moreover, in order to improve the visibility of the riverbed exploration tool, it is preferable to add a colorant to the cement as necessary. This makes it easier to find the riverbed exploration tool with the naked eye even in a cloudy river after a flood. As this colorant, one made of an alkali-resistant pigment-based material is used. By using such an alkali-resistant pigment-based material, the riverbed exploration tool is less likely to fade even when placed in a river for a long time.
[0036]
When selecting these cement, aggregate, and colorant materials, those having an appropriate specific gravity are selected so that the weight of the riverbed exploration tool is approximately equal to that of the riverbed material obtained by sampling. However, since it has been known that the general gravity of the riverbed material is in the vicinity of 2.65, it is desirable that the specific gravity of the riverbed exploration tool does not greatly deviate from this value.
[0037]
Cement, aggregate and colorant prepared in this way are mixed, water is added to this, kneaded to an appropriate viscosity, poured into a mold, and a permanent magnet is placed parallel to the longitudinal direction of the mold. After leaving the concrete to harden, remove the mold to complete the riverbed probe.
[0038]
A riverbed exploration tool that is made by imitating riverbed material collected in an actual river is suitable for investigating actual riverbed fluctuations. By making a number of riverbed exploration tools with the same quality and using them for surveying multiple target rivers, the hydraulic characteristics of each river can be compared.
[0039]
As described above, the riverbed exploration device according to the present invention can identify the position by using a magnetic exploration technique by embedding a permanent magnet in the main body, and the solid main body has a weight of the permanent magnet in addition to its weight. Is made of a material having a specific gravity such that the total weight of the riverbed material is approximately equal to the weight of the riverbed material, so that the riverbed exploration tool can have a flow resistance similar to that of the riverbed material. Is appropriately arranged on the riverbed of the actual river to be surveyed, and the position of the riverbed exploration tool flowed using the magnetic exploration technique is obtained, so that it is possible to obtain a more realistic riverbed fluctuation.
[0040]
【The invention's effect】
According to the riverbed exploration tool of the present invention, since the permanent magnet is embedded in the main body, the position can be specified by using a magnetic exploration technique, and the solid main body adds the weight of the permanent magnet to the total weight. Because it is made of a material that has a specific gravity that is almost equal to the weight of the riverbed material, the riverbed exploration tool can have a flow resistance similar to that of the riverbed material. It is possible to know the near river bed change.
[Brief description of the drawings]
FIG. 1 is a perspective view showing the structure of a first embodiment of a riverbed exploration tool according to the present invention.
FIG. 2 is a schematic diagram showing a usage pattern of the riverbed probe shown in FIG.
3 is a schematic diagram showing a method for detecting the direction of the riverbed probe shown in FIG. 1. FIG.
4A and 4B are waveform diagrams of detection of the magnetic field strength in the detection method shown in FIG. 3, where FIG. 4A is a waveform diagram when the permanent magnets are arranged vertically and FIG. 4B is a waveform diagram when the permanent magnets are arranged horizontally.
FIG. 5 is a flowchart showing a manufacturing process of the riverbed exploration tool shown in FIG. 1;
FIGS. 6A and 6B are a front view and a top view for explaining a shape factor that is a guide for producing the riverbed exploration tool shown in FIG. 1;
[Explanation of symbols]
1 Riverbed Exploration Tool 1a Body 1b Permanent Magnet

Claims (6)

A riverbed exploration tool for investigating riverbed changes in rivers using a magnetic detection method,
A solid body imitating the size and shape of the riverbed material of the river under investigation;
With a permanent magnet embedded in this body,
The riverbed probe according to claim 1, wherein the solid body is made of a material having a specific gravity such that a total weight obtained by adding a weight of the permanent magnet to a weight of the solid body is substantially equal to a weight of the riverbed material. The river bed exploration tool according to claim 1, wherein the permanent magnet has a bar shape. The river bed exploration tool according to claim 2, wherein the permanent magnet having the rod shape is arranged so that an axial direction thereof is substantially parallel to a longitudinal direction of the solid main body. The river bed according to any one of claims 1 to 3, wherein the solid main body is concrete formed from a mold obtained by casting a riverbed material of a river to be surveyed. Probe. The river bed exploration tool according to claim 4, wherein a colorant is mixed in the concrete. The riverbed exploration tool according to any one of claims 1 to 5, wherein the length of the solid main body is in a range of 50 mm to 100 mm.

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