JP5815316B2 - Muddy water density measuring device - Google Patents

Description

  The present invention includes, for example, muddy water accumulated in excavation holes / grooves in a method of drilling the ground using excavated water, unsolidified soil cement when a soil cement structure is constructed in an in-situ agitation method, cast-in-place Used to measure the density of suspension containing solid particles in the ground, such as hole wall stabilizing liquid injected into drilled holes in the construction of concrete piles, in the ground. The present invention relates to a muddy water density measuring device.

Generally, in the method of drilling the ground using drilling water, the density of mud collected in the drilling holes and grooves is measured in order to confirm the suitability of the drilling water volume. In the in-situ stirring method, in order to estimate the moisture content of the soil cement, the density of the unsolidified soil cement is measured. In order to confirm the quality, the density of the pore wall stabilizing solution is measured.
In suspension such as muddy water in such holes and grooves, solid particles such as soil particles, cement and other solidifying materials are suspended in water or dispersant, etc. or settled at a constant speed. In the case of measuring the density of a suspension containing such solid particles (hereinafter simply referred to as “muddy water”), conventionally, muddy water or the like is placed in a container having a certain volume, From the above, measure the mass and calculate by dividing the measured mass value by the volume of the container, or use a balance-type scale called mud balance and put a fixed amount of mud in one container. It is possible to measure the specific gravity by moving the weight on this arm so that the measurement scale extending from the arm is horizontal on the support pedestal and reading the scale of the arm at the position of the weight It has been broken.

  By the way, in such a method for measuring the density of muddy water using a container or mud balance, the muddy water to be measured is collected from a hole or groove in the ground, and the density of the muddy water is measured by a measuring device installed on the ground. Since the measurement is performed, the work is complicated and a lot of time is required. Thus, a measuring instrument that can measure the density of muddy water or the like in the ground at the original position in the ground has been demanded, and this type of measuring instrument has been proposed in Patent Document 1.

  This document 1 relates to a liquid hydrometer. The hydrometer of this document 1, as shown in FIG. 6, has a pressure sensing part 61 having an enlarged tip part, and contains a pressure transmission liquid 62 therein. A differential pressure transducer 64 that connects the sealed pressure transmission pipe 63 up and down; a waterproof box 640 that surrounds the differential pressure transducer 64; a pressure indicator 66 that is coupled to the differential pressure transducer 64 by a cord 65; A support frame 67 that supports the pressure transmission pipe 63 and is integrated with the waterproof box 640, a plurality of grips 68 provided on the top of the support frame 67, and a rope 69 connected to the grips 68. The ground is inserted into the muddy water in the drilled hole so that the specific gravity of the muddy water can be measured at a predetermined depth.

Japanese Utility Model Publication No. 61-82249

However, the conventional liquid hydrometer has the following problems.
(1) In the first place, this hydrometer is intended to measure the density of muddy water, etc., because it does not measure the liquid, and does not measure the muddy water in which solid particles such as soil particles are suspended or settled. It cannot be used as a device.
(2) Since the liquid that transmits the pressure is enclosed in the pressure transmission tube, if a temperature difference occurs in the liquid to be measured, the liquid enclosed in the pressure transmission tube is also affected by the temperature change, The density and volume change, and the change becomes an apparent pressure, and an accurate differential pressure cannot be measured.
(3) In order to deal with the problem (2) above, it is conceivable to eliminate the pressure transmission liquid and, for example, integrate the pressure receiving portion and the differential pressure gauge. However, in this case, the measured differential pressure becomes small. , Measurement accuracy will deteriorate.
(4) To cope with the problem of (3) above, it is conceivable to enlarge the differential pressure gauge. However, if the differential pressure gauge is enlarged, this causes the temperature change within the differential pressure gauge as in (2) above. The effect of.
(5) When the density is measured in the deep part of the muddy water in the ground, the pressure acting on the pressure receiving part increases with the depth of the muddy water, etc. The measurement accuracy of minute differential pressure is reduced compared to the pressure in the deep part. In this case, if an attempt is made to increase the pressure resistance performance by enclosing the fluid inside the pressure receiving portion, in addition to the error due to the compressibility of the fluid and a decrease in sensitivity, the effect of temperature change is increased as in (2) above. .
(6) The measurement capacity of the differential pressure gauge is preferably the optimum capacity for ensuring accuracy with respect to the differential pressure calculated from the density to be measured and the distance between two depths, but the maximum value of the differential pressure is muddy water. At the stage of inserting the differential pressure gauge into the mud, only the lower pressure receiving part is immersed in the muddy water, and the upper pressure receiving part occurs immediately before being immersed in the mud, so if you select the capacity of the differential pressure measuring part for this maximum differential pressure value, Measurement accuracy is lower than when the capacity is optimal for the differential pressure in the muddy water.
(7) Density of muddy water or the like to be measured is wide and the 1.0~1.05g / cm ³ about hole wall stabilizing solution until 1.2~1.6g / cm ³ order of mud and soil cement Therefore, in order to ensure measurement accuracy for each measurement target, it is desirable that the capacity of the differential pressure measurement unit can be changed according to the measurement target.

  The present invention solves such a conventional problem, and in this type of muddy water equal density measuring apparatus, a hole drilled in the ground, mud water in a groove, etc. are suspended or submerged in the ground. An object is to easily and accurately measure the density of a liquid containing solid particles at an in-situ location in the ground.

In order to achieve the above-described object, the present invention provides a differential pressure measuring device that has pressure receiving portions at the top and bottom and measures a pressure difference between two points at different depths from the liquid surface containing solid particles such as muddy water. An arithmetic unit that calculates an average density of the liquid between the two points based on a pressure difference between the two points obtained from the differential pressure measuring device, a distance between the two points, and a gravitational acceleration. In the liquid density measuring device such as muddy water, the differential pressure measuring device is inserted into the liquid and measures an average density of the liquid between the two points at a predetermined depth. A differential pressure measuring section having upper and lower pressure receiving sections close to each other, and surrounding the upper pressure receiving section of the differential pressure measuring section in a watertight manner and raised upward from the lower pressure receiving section Extending up to a predetermined height corresponding to the distance between the two points A communication pipe having an opening at the bottom, the lower pressure receiving portion is in direct contact with the liquid at a lower point in the liquid, the pressure is received by the lower pressure receiving portion, and the communication pipe is filled with water. The upper end of the communication pipe is opened into the liquid in an open state without sealing , the opening is in contact with the liquid at a point above the liquid, and the upper part is connected via the water in the communication pipe. The gist is that the pressure is received by the pressure receiving portion of and the pressure difference between the two points is measured.

Moreover, it is preferable that this density measuring apparatus is provided with the following structures in each part.
(1) The differential pressure measuring unit has an upper pressure-receiving portion on the upper surface and can be expanded and contracted in the vertical direction, a lower bellows having a lower pressure-receiving portion on the lower surface and expandable and contracted in the vertical direction, A connecting member that is inserted on the inner shaft core of the upper bellows and the lower bellows and rigidly connects the upper pressure receiving portion and the lower pressure receiving portion; and installed in the upper bellows or the lower bellows, The amount of displacement of the connecting member that is displaced in the axial direction of the upper and lower bellows due to the deformation of the upper and lower bellows is detected with respect to the pressure difference received by the pressure receiving portion, and the pressure difference between the pressure receiving portions of the upper and lower portions is detected. A displacement meter to measure.
In this case, a non-contact type displacement meter is employed as the displacement meter, and this non-contact type displacement meter is installed inside the differential transformer core disposed in a part of the connecting member and the upper bellows or the lower bellows. And a differential transformer disposed around the differential transformer core.
(2) The communication pipe has means for extending or shortening the length in the vertical direction so that the height can be changed.
(3) The communication pipe communicates with a large diameter portion capable of enclosing from the outer peripheral surface of the differential pressure measuring portion to a predetermined height above the upper pressure receiving portion, and a part of the large diameter portion. A small-diameter portion extending upward to a predetermined height.
In this case, it is desirable to have an inlet for injecting water into the large diameter portion of the communication pipe.
Further, it is desirable that the small-diameter portion of the communication pipe has a substantially inverted L shape as a whole, its upper end portion is bent in the horizontal direction, and its end surface is opened.

In the muddy water equal density measuring device of the present invention, the differential pressure measuring device is inserted into a liquid containing solid particles suspended or settled in the ground, such as muddy water, at the predetermined depth, by the above-described configuration. The pressure receiving part of the liquid is in direct contact with the liquid at a lower point in the liquid, receives the pressure at the lower pressure receiving part, fills the communication pipe with water, and seals the opening at the upper end of the communication pipe. The inside is opened, this opening is contacted with the liquid at a point above the liquid, pressure is received at the upper pressure receiving part via the water in the communication pipe, and the pressure difference between the two points is measured. by the height, to increase the pressure difference between the upper and lower two points of measurement state, it is possible to improve the measurement accuracy of the pressure difference between the two points, also the communicating pipe to the opening at the upper end is opened in is open in the liquid, since the communicating pipe water is not sealed, water communicating tube, the temperature in the liquid Without being affected by changes, the pressure at the upper point in the liquid in contact with the opening at the upper end can be reliably transmitted to the differential pressure measurement unit, and solid particles suspended or settled in the ground such as muddy water There is an extraordinary effect that the density of the liquid containing can be easily and accurately measured at the original position in the ground.
Further, according to the muddy water equal density measuring device of the present invention, in particular, the differential pressure measuring part has a bellows structure, and the axial direction of the upper and lower bellows by the deformation of the upper and lower bellows with respect to the pressure difference received by the upper and lower pressure receiving parts The displacement of the connecting member that is displaced in the direction is detected with a displacement meter, and the pressure difference between the pressure receiving parts at the upper and lower parts is measured, so it can withstand large pressure in deep parts such as muddy water with a simple structure. At the same time, it has a remarkable effect that the measurement accuracy of the minute differential pressure can be increased as compared with the muddy water pressure. Also, in this case, by adopting a non-contact type displacement meter, for example, when pressure acts only on one pressure receiving part and becomes an excessive differential pressure, the connecting member in the bellows is displaced beyond the measurement capacity However, in the differential pressure measuring part, the displacement gauge and other parts do not damage any part, and if the connecting member is again within the measurement capacity, the displacement amount of the connecting member can be measured normally. There is.
Furthermore, according to the muddy water density measuring device of the present invention, in particular, the height in the vertical direction can be extended or shortened so that the height of the communication pipe can be changed. By changing the height of the communication pipe, it is possible to obtain an effect that the same high measurement accuracy can be ensured for each measurement object.

The figure which shows schematic structure of the muddy water equal density measuring apparatus in one embodiment of this invention Diagram showing the principle of measuring the density of mud etc. with the same density measuring device The figure which shows the result of the laboratory test about the same density measuring apparatus ((a): When the density of muddy water is 1.0-1.1 g / cm < ³ > (b): The density of muddy water is 1.0-1.8 g / cm ³ ) The figure which shows the result (especially the relationship between water temperature and density measured value) of the laboratory test about the same density measuring device The figure which shows the result of the field test about the same density measuring device Figure showing a conventional liquid hydrometer

  Next, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 shows an apparatus for measuring the density of muddy water. As shown in FIG. 1, the muddy water equal density measuring device S has pressure receiving portions 11 and 12 on the upper and lower sides, and measures a pressure difference between two points at different depths from the liquid surface containing solid particles such as muddy water. Differential pressure measuring device 1, a recording unit 2 that stores a pressure difference between two points measured by the differential pressure measuring device 1, a pressure difference between the two points stored in the recording unit 2, and the distance between the two points And an arithmetic device 3 that calculates the average density of the liquid between two points based on the distance and the gravitational acceleration. The differential pressure measuring device 1 is inserted into the liquid, and at a predetermined depth, 2 The average density of liquid between points is measured.

  In this density measuring device S, the differential pressure measuring device 1 includes a differential pressure measuring unit 10 having upper and lower pressure receiving units 11 and 12 close to each other, and a periphery of the pressure receiving unit 11 above the differential pressure measuring unit 10 in a watertight manner. And a communication pipe 20 having an opening 21 at the upper end that extends upward from the lower pressure receiving portion 12 to a predetermined height corresponding to the distance between the two points.

In this differential pressure measuring device 1, a differential pressure measuring unit 10 has an upper pressure receiving portion 11 on the upper surface, an upper bellows 101 that can be expanded and contracted in the vertical direction, and a lower pressure receiving portion 12 on the lower surface, and the vertical direction. A lower bellows 102 that can be expanded and contracted, a connecting member 13 that is inserted over the inner bellows of the upper bellows 101 and the lower bellows 102 and rigidly connects the upper pressure receiving portion 11 and the lower pressure receiving portion 12, and the upper bellows 101 or A connecting member 13 installed inside the lower bellows 102 and displaced in the axial direction of the upper and lower bellows 101, 102 by deformation of the upper and lower bellows 101, 102 with respect to the pressure difference received by the upper and lower pressure receiving portions 11, 12. And a displacement meter 14 for measuring the pressure difference between the upper and lower pressure receiving portions 11 and 12.
In the case of the differential pressure measuring unit 10, the upper bellows 101 and the lower bellows 102 are the same type and have the same size. Each of the upper and lower bellows 101, 102 has a bellows-like substantially cylindrical shape, and has a high pressure resistance performance against the cylindrical side surface, and with respect to pressure in the axial direction of the cylindrical shape, it expands and contracts according to its acting force. And act as a spring. These upper and lower bellows 101 and 102 are superposed vertically and joined via the partition plate 15. A rigid connecting rod is employed for the connecting member 13 that connects the upper and lower pressure receiving portions 11 and 12, and the upper and lower pressure receiving portions 11 and 12 are inserted on the shaft core inside the upper and lower bellows 101 and 102. Connected by connecting rod.
The displacement meter 14 is a non-contact displacement meter. The non-contact type displacement meter 14 is installed inside the differential transformer core 141 disposed in a part of the connecting member 13 and the upper bellows 101 or the lower bellows 102, and is disposed around the differential transformer core 141. In this case, the differential transformer core 141 is arranged near the center position in the vertical direction of the connecting member 103, and the differential transformer 142 corresponds to the differential transformer core 141 in the upper bellows 101. Arranged. In this way, the differential transformer core 141 integrated with the connecting member 103 that is displaced by the pressure difference received by the upper and lower pressure receiving portions 11 and 12 is detected by the differential transformer 142, and the upper and lower pressure receiving portions 11, The pressure difference between 12 is measured, converted into an electrical signal, and output.

The communication pipe 20 includes a large-diameter portion 201 that can surround a predetermined height above the upper pressure-receiving portion 11 from the outer peripheral surface of the differential pressure measuring portion 10, and a part of the large-diameter portion 201, in this case, The small-diameter portion 202 communicates with the center and extends upward on the upper surface of the large-diameter portion 201 approximately vertically to a predetermined height.
In the case of this communication pipe 20, it has means for extending or shortening the length in the vertical direction so that the height can be changed. In this case, the communication pipe 20 may be provided with a plurality of communication pipes having different lengths in the vertical direction, and each may be detachably attached to the outer peripheral surface of the differential pressure measuring unit 10. May be formed by connecting a plurality of pipes, and the vertical length may be adjusted by increasing or decreasing the number of pipes to be connected.
In this case, the outer peripheral surface of the large diameter portion 201 extends slightly below the level of the pressure receiving portion 12 below the differential pressure measuring portion 10, and the lower surface is opened. A filter 22 for protecting the differential pressure measuring unit 10 is attached to the opening. The large-diameter portion 201 is vertically divided by a partition plate 15 between the upper and lower bellows 101 and 102, and the upper and outer peripheral surfaces of the upper bellows 101 are surrounded in a watertight manner. An inlet 23 for injecting water into the communication pipe 20 is formed on the outer peripheral surface of the large diameter portion 201 on the upper side surrounding the outer peripheral surface of the upper bellows 101. The water inlet 23 is opened and closed by a valve.
The small-diameter portion 202 has a substantially inverted L shape as a whole, the upper end portion is bent in the horizontal direction, and the end surface is opened.

  In this density measuring apparatus S, the recording unit 2 is embodied by a data logger or the like, and the computing unit 3 is implemented by a personal computer and OS software stored in the personal computer and various application software. Since data loggers and personal computers that are generally available on the market are used, detailed explanation of each is omitted here.

FIG. 2 illustrates the measurement principle of the density measuring device S. In FIG. 2, M is muddy water mixed with water and solidifying material such as soil particles and cement, a dispersing agent, etc., and the solid particles such as soil particles are suspended or settled at a constant velocity in the liquid phase. It has become.
This density measuring device S measures the pressure difference between the upper and lower two depths in such muddy water M, and divides this pressure difference by the distance between the two depths and the gravitational acceleration. Find the average density of M, such as muddy water.
In the case of this density measuring device S, water W is filled in the communication pipe 20 of the differential pressure measuring device 1 up to the opening 21 at the upper end, the differential pressure measuring device 1 is inserted into muddy water or the like M, and a predetermined depth is reached. Then, the lower pressure receiving portion 12 is directly brought into contact with the muddy water M at a lower point in the muddy water M, and the lower pressure receiving portion 12 receives pressure, and the opening 21 at the upper end of the communication pipe 20 is placed in the muddy water M. Open, the opening 21 is brought into contact with the muddy water M at the upper point in the muddy water M, etc., and the pressure is received by the upper pressure receiving portion 11 to measure the pressure difference between the upper and lower predetermined points in the muddy water M. . This pressure difference is stored in the data logger 2. Then, using a personal computer 3 (see FIG. 1), based on the pressure difference between the upper and lower predetermined points stored in the data logger 2, the distance between the two points, and the gravitational acceleration, mud water between the two points Calculate the average density.
In this case, the average density of mud water between two depths is obtained by the following equation (1).
Mean mud density _{P avr = (P 2 -P 1} ) / (H + h) / g
= ( _Pw · g · H + ΔP) / (H + h) / g (1)
However, in Formula (1),
H: Communication pipe head (height of the communication pipe above the upper surface of the differential pressure measurement part (upper pressure receiving part))
h: Height of the differential pressure measurement part (height between the upper pressure receiving part and the lower pressure receiving part)
P _w : Density of water in the communication pipe g: Gravitational acceleration P ₁ : Upper mud pressure P ₂ : Lower mud pressure ΔP: Measurement differential pressure

According to this density measuring device S, even when solid particles such as soil particles are suspended or settled at a constant velocity in water, such as muddy water M, by measuring the pressure difference between the upper and lower two depths, The average density of the section can be obtained. In this case, the lower pressure receiving portion 12 is directly brought into contact with the muddy water M at a lower point in the muddy water M, etc., is subjected to pressure by the lower pressure receiving portion 12, is raised on the upper pressure receiving portion 11, and the water W The upper end opening 21 of the communication pipe 20 filled with is opened in muddy water or the like M, and this opening 21 is brought into contact with muddy water or the like at a point above the muddy water or the like M so that pressure is received by the upper pressure receiving portion 11. The pressure difference between the upper and lower two points to be measured is increased by the height of the communication pipe 20 raised on the upper pressure receiving portion 11, and the height of the communication pipe 20 is set appropriately for each measurement object. The required measurement accuracy can be obtained between these two points.
In this case, since the upper end opening 21 of the communication pipe 20 is opened in the muddy water M and the water W in the communication pipe 20 is not sealed, the temperature of the water W in the communication pipe 20 changes in the muddy water M. The measurement error can be reduced to such an extent that it can be ignored in practice, and the pressure at the upper point in the muddy water or the like M that is in contact with the opening 21 at the upper end is changed to the differential pressure measuring unit 10 (the upper pressure receiving unit 11). Can be transmitted reliably.
Since the differential pressure measuring unit 10 has a bellows structure, it can withstand a large pressure in a deep part such as muddy water, and the bellows 101 and 102 are axially applied to a minute differential pressure compared to the muddy water pressure. Since the connecting member 13 is displaced inside the bellows 101 and 102 due to deformation, the pressure difference between the upper and lower pressure receiving portions 11 and 12 is measured simply by detecting the displacement of the connecting member 13 using the displacement meter 14. can do. In this case, since a non-contact-type transformer displacement meter is adopted as the displacement meter 14, the pressure of muddy water acts only on one pressure receiving portion (12) and an excessive differential pressure between both pressure receiving portions 11, 12. Even if the connecting member 13 in the bellows 101, 102 is displaced beyond the measurement capacity, the displacement gauge 14 and other parts are not damaged, and the connecting member 13 is again accommodated in the measurement capacity. Thus, the displacement amount of the connecting member 13 can be measured normally.
Further, in this density measuring device S, the length in the vertical direction of the communication pipe 20 can be extended or shortened, so that the rise of the communication pipe 20 with respect to the differential pressure measuring unit 10 is matched to the density of the muddy water to be measured. By appropriately changing the height, that is, when the density is small, the rising height is appropriately increased, and when the density is large, the rising height is appropriately decreased, so that the differential pressure to be measured can be changed. It can adjust so that it may become the optimal to the measurement capacity | capacitance to have, and can measure the density, such as a muddy water, for every measuring object with the same measurement precision, without changing the differential pressure measurement part 10 itself.

The applicant of the present application conducted an indoor test and a field test on the density measuring device S as follows, and obtained the following results.
(Indoor test)
In the laboratory test, a water tank of a size that can accommodate the density measuring device S is provided in the room, fresh water is stored in the water tank, the density measuring device S is installed, the density of the fresh water is measured, and then the clay, Sand was added and stirred to create muddy water. The density of this muddy water was increased stepwise, and the density of the muddy water was measured with the density measuring device S each time. The results of this laboratory test are shown in FIG.
And the muddy water was extract | collected and it confirmed that the density of the muddy water calculated | required from the volume and mass and the density of the muddy water measured with the density measuring apparatus S became the substantially same value.
In addition, fresh water is stored in the water tank, the density measuring device S is inserted, and the initial temperature is heated from 20 ° C. to 30 ° C. with a heater, and then 20 ° C. fresh water is injected from the bottom of the water tank and drained at the top. The water inside was replaced with fresh water at 20 ° C. The results of this test are shown in FIG.
As the water temperature increases, the density decreases, and as the water temperature decreases, the density increases. The measured density shows the same tendency as the density of distilled water indicated by the solid line, and the change in the measured density due to the temperature change is mostly due to the change in the density of the water itself. It can be seen that the error due to is practically negligible (0.001 g / cm ³ ).
(Field test)
In the field test, a cement solidified pile with a depth of 5 m was placed on the actual ground. In this case, the cement solidified pile was formed by injecting cement slurry into which the cement, bentonite and water were mixed. A density measuring device S was inserted in the vicinity of the center of the cement solidified pile immediately after placing, and the density of the cement slurry was measured every 50 cm in depth. The results of this field test are shown in FIG.
The density of the cement-solidified pile was obtained by taking a core by all-core boring after hardening and calculating from the volume and mass. The core density is smaller at the upper part and larger at the lower part than the density measured in-situ. This is because the cement particles continue to settle after the density is measured in-situ. This is thought to be due to the small size and the large size at the bottom. From this, the density measured in-situ is considered to be a reasonable value as the density at the time of measurement.

  As described above, according to the density measuring device S, the differential pressure measuring device 1 includes the differential pressure measuring unit 10 having the pressure receiving units 11 and 12 close to each other in the vertical direction, and the upper part of the differential pressure measuring unit 10. A communication having an opening 21 at the upper end that surrounds the periphery of the pressure receiving portion 11 in a watertight manner and extends upward to a predetermined height corresponding to the distance between the upper and lower two points measured from the lower pressure receiving portion 12. The pipe 20 is configured so that the communication pipe 21 of the differential pressure measuring device 1 is filled with water W, and the differential pressure measuring device 1 is inserted into muddy water M and the like at a predetermined depth. The pressure receiving part 12 is directly in contact with the muddy water M at a lower point in the muddy water M, etc., receives pressure at the lower pressure receiving part 12, and opens the opening 21 at the upper end of the communication pipe 20 into the muddy water M, The opening 21 is in contact with the muddy water M at a point above the muddy water M, and receives pressure at the upper pressure receiving portion 11. Since the pressure difference between the points is measured, the pressure difference between the two upper and lower points to be measured is increased by the height of the communication pipe 20 raised on the upper pressure receiving portion 11, and the pressure difference between the two points is measured. Further, since the upper end opening 21 of the communication pipe 20 is opened in the muddy water or the like M and the water W in the communication pipe 20 is not sealed, the water W in the communication pipe 20 is not sealed. Can be reliably transmitted to the differential pressure measuring unit 10 without being affected by temperature changes in the muddy water M, and the pressure at the upper point in the muddy water M that is in contact with the opening 21 at the upper end. The density of equal M can be easily and accurately measured at the original position in the ground.

Further, in this density measuring device S, the differential pressure measuring unit 10 has an upper pressure receiving part 11 on the upper surface, an upper bellows 101 that can be expanded and contracted in the vertical direction, and a lower pressure receiving part 12 on the lower surface. A lower bellows 102 that can be expanded and contracted in the direction, a connecting member 13 that is inserted through the inner bellows of the upper bellows 101 and the lower bellows 102 and rigidly connects the upper pressure receiving portion 11 and the lower pressure receiving portion 12, and the upper bellows 101 Alternatively, a connecting member that is installed inside the lower bellows 102 and is displaced in the axial direction of the upper and lower bellows 101 and 102 by the deformation of the upper and lower bellows 101 and 102 with respect to the pressure difference received by the upper and lower pressure receiving portions 11 and 12. 13 displacement amount, and a displacement gauge 14 for measuring the pressure difference between the upper and lower pressure receiving portions 11 and 12, and the whole has a two-stage upper and lower bellows structure. Pressure With respect to the pressure difference performance that is smaller than the muddy water pressure, the connecting member 13 inside the bellows 101, 102 is displaced by the axial deformation of the bellows 101, 102, and this connecting member Since the 13 displacements are detected by the displacement meter 14, the sensitivity to pressure can be increased.
In this case, a non-contact type displacement meter is adopted as the displacement meter 14 and is installed in the differential transformer core 141 disposed in a part of the connecting member 13 and the upper bellows 101 or the lower bellows 102. Since the differential transformer 142 is arranged around the differential transformer core 141, the pressure of the muddy water acts only on one pressure receiving portion 12 to generate an excessive differential pressure, and the connecting members in the bellows 101 and 102 Even when 13 is displaced beyond the measurement capacity, the displacement gauge 14 and other parts in the differential pressure measurement unit 10 are not damaged, and if the connection member 13 falls within the measurement capacity again, the connection member 13 Can be measured normally.

Further, in this density measuring apparatus S, the communication pipe 20 has means for extending or shortening the length in the vertical direction so that the height can be changed. Therefore, the difference in the communication pipe 20 is adjusted according to the density of the muddy water or the like to be measured. By appropriately changing the rising height with respect to the pressure measuring unit 10, it is possible to improve the measurement accuracy for each measuring object such as muddy water without changing the differential pressure measuring unit 10 itself.
Further, the communication pipe 20 is communicated with the center of the upper surface of the large diameter portion 201 and the large diameter portion 201 that can surround a predetermined height above the upper pressure receiving portion 11 from the outer peripheral surface of the differential pressure measuring section 10. Since the upper surface of the large-diameter portion 201 is configured by the small-diameter portion 202 that extends substantially vertically to a predetermined height, the entire communication pipe 20 can be attached to the differential pressure measuring unit 10 with a simple structure. The entire differential pressure measuring device 1 together with the pressure measuring unit 10 can be made compact.
And in the case of this communication pipe 20, since the injection port 23 for injecting water into the large diameter portion 201 is provided, the communication pipe 20 can be easily filled with water using this injection port 23, Moreover, even if muddy water or the like enters the communication pipe 20 while the differential pressure measuring device 1 is inserted into the muddy water M and the operation of measuring the pressure difference between the upper and lower two points is repeated, the large diameter portion By injecting water into the communication pipe 20 from the water inlet 23 of 201, muddy water or the like M can be easily discharged from the communication pipe 20. Further, since the entire small-diameter portion 202 has a substantially inverted L shape, the upper end portion is bent in the horizontal direction, and the end surface thereof is opened, the opening 21 at the upper end of the communication pipe 20 is located at a point above the muddy water M (predetermined The water W filled up to the upper end of the communication pipe 20 can be reliably subjected to pressure such as muddy water.
Further, since the upper end portion is bent in the horizontal direction, even if muddy water or the like enters from the opening 21 of the communication pipe 20, solid soil particles accumulate at the bottom of the horizontal portion of the communication pipe 20, and the communication pipe. It becomes difficult to invade to the substantially vertical part of 20, and it becomes difficult to influence the density of the water in the substantially vertical part of the communication pipe 20, and a measurement error can be reduced.

DESCRIPTION OF SYMBOLS S Muddy water equal density measuring apparatus 1 Differential pressure measuring apparatus 10 Differential pressure gauge main body 101 Upper bellows 102 Lower bellows 11 Upper pressure receiving part 12 Lower pressure receiving part 13 Connecting member 14 Displacement meter 141 Differential transformer core 142 Differential transformer 15 Partition plate 20 Communication pipe 201 Large diameter part 202 Small diameter part 21 Opening 22 Filter 23 Water inlet 2 Recording part (data logger)
3 Arithmetic unit (PC)

Claims (8)

A differential pressure measuring device that has pressure receiving portions above and below and measures a pressure difference between two points above and below at different depths from a liquid surface containing solid particles such as muddy water, and the 2 obtained from the differential pressure measuring device An arithmetic device that calculates an average density of the liquid between the two points based on a pressure difference between the points, a distance between the two points, and a gravitational acceleration, and the differential pressure measuring device is disposed in the liquid. In a liquid density measuring device such as muddy water that measures the average density of the liquid between the two points at a predetermined depth,
The differential pressure measuring device is
A differential pressure measuring unit having the upper and lower pressure receiving units close to each other;
The upper end of the differential pressure measuring unit is surrounded by water tightly around the upper pressure receiving unit and is raised upward to extend to a predetermined height corresponding to the distance between the two points from the lower pressure receiving unit. A communication pipe having an opening;
With
The lower pressure receiving portion is in direct contact with the liquid at a lower point in the liquid, and receives pressure at the lower pressure receiving portion,
The communication pipe is filled with water to open the liquid in an open state without sealing the opening at the upper end of the communication pipe, the opening is in contact with the liquid at a point above the liquid, and the communication Receiving pressure at the upper pressure receiving part through the water in the pipe ,
Measuring the pressure difference between the two points;
An apparatus for measuring the density of liquid such as muddy water.   The differential pressure measuring unit has an upper pressure-receiving portion on the upper surface and can be expanded and contracted in the vertical direction, a lower bellows having a lower pressure-receiving portion on the lower surface and expandable and contracted in the vertical direction, the upper bellows, A connecting member that is inserted on the inner shaft core of the lower bellows and rigidly connects the upper pressure receiving portion and the lower pressure receiving portion; and the upper and lower pressure receiving portions that are installed inside the upper bellows or the lower bellows. Displacement that detects the amount of displacement of the connecting member that is displaced in the axial direction of the upper and lower bellows due to the deformation of the upper and lower bellows, and measures the pressure difference between the pressure receiving portions of the upper and lower parts. The liquid density measuring apparatus such as muddy water according to claim 1, further comprising a meter.   The liquid density measuring device such as muddy water according to claim 2, wherein the displacement meter is a non-contact type displacement meter.   The non-contact type displacement meter includes a differential transformer core disposed in a part of the connecting member, a differential transformer disposed within the upper bellows or the lower bellows, and disposed around the differential transformer core; The liquid density measuring apparatus for muddy water or the like according to claim 3.   The liquid density measuring apparatus such as muddy water according to any one of claims 1 to 4, wherein the communication pipe includes means for extending or shortening a length in a vertical direction so that a height thereof can be changed.   The communication pipe communicates with a large-diameter portion capable of enclosing from the outer peripheral surface of the differential pressure measuring portion to a predetermined height above the upper pressure-receiving portion, and a part of the large-diameter portion, and is directed above the large-diameter portion. The liquid density measuring device such as muddy water according to any one of claims 1 to 5, further comprising a small-diameter portion extending to a predetermined height.   The liquid density measuring apparatus such as muddy water according to claim 6, further comprising an inlet for injecting water into a large diameter portion of the communication pipe.   The liquid density measuring device such as muddy water according to claim 6 or 7, wherein the small-diameter portion of the communication pipe has a substantially inverted L shape as a whole, an upper end portion thereof is bent in the horizontal direction, and an end surface thereof is opened.

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