JP7367833B2 - Specific gravity measuring device - Google Patents

Description

The present invention relates to a specific gravity measuring device for measuring the specific gravity of a stabilizing liquid used in construction of cast-in-place concrete piles and underground walls.

Stabilizing fluid (bentonite mud) is used to prevent the wall of the drilled hole from collapsing. The properties of this stabilizing liquid are measured because they can affect the quality of the pile concrete built inside the hole. Generally, the viscosity, specific gravity, and sand fraction of the stabilizer are measured using a funnel viscometer, a mud balance, and a sand content meter, respectively. Furthermore, there is also a technique for periodically measuring the properties of the stabilizing liquid (for example, see Patent Document 1). In the method for measuring the properties of muddy water described in this document, the specific gravity, viscosity, and sand fraction of a stable liquid are measured. In this case, the sand fraction is determined by classifying the sand contained in the muddy water discharged from the muddy water measuring container and measuring the weight of the classified sand.

Japanese Patent Application Publication No. 8-35924

However, it takes time and effort to measure the properties of the stable liquid, such as the sand fraction.

The specific gravity measuring device that solves the above problem is a specific gravity measuring device that measures the specific gravity of a stabilized liquid, and includes a cylindrical container with a fixed volume with an open top, and a pressure gauge that measures the weight of the stabilized liquid in this container. The pressure gauge is attached to a lower mounting position from the top surface of the container, the lower end of the container is connected to a supply pipe through which the stabilizing liquid filled inside the hole flows, and In this case, a stable liquid is supplied from below through the supply pipe, and after flowing upward into the container, it overflows from the upper opening of the container, and the pressure gauge is placed at the mounting position. The weight of the stabilizing liquid is measured by measuring the pressure of the stabilizing liquid in the container located above.

According to the present invention, the properties of the stabilizer can be evaluated by efficiently measuring the sand fraction of the stabilizer.

An explanatory diagram illustrating a system configuration of an evaluation device in an embodiment. It is an explanatory view explaining the specific gravity difference in an embodiment, and (a) shows a sand meter used conventionally, and (b) is an explanatory view explaining the relationship between air, water, and soil particles. FIG. 3 is an explanatory diagram illustrating the relationship between the sand content and the converted sand content according to the conventional method in the embodiment, in which (a) is a graph showing the measured values of each stabilizing liquid, and (b) is a graph showing the numerical values in (a).

An embodiment of a specific gravity measuring device will be described below with reference to FIGS. 1 to 3. Here, properties such as the sand fraction of the stabilizing liquid discharged from the pile hole and recovered will be measured and evaluated.

As shown in FIG. 1, the inside of the excavated pile hole 10 is filled with a stabilizing liquid 11. A pump 15 is placed at the bottom of the pile hole 10. A recovery pipe 16 is connected to this pump 15 . The pump 15 is driven to discharge the stabilizing liquid 11 from the recovery pipe 16 to the outside of the pile hole 10. Recovery pipe 16 is connected to plant 17 . The plant 17 includes a plurality of water tanks in which the sand content of the stabilizing liquid is settled and removed. The plant 17 then precipitates the sand content of the recovered stabilizing liquid in each water tank, and supplies the good stable liquid from which the sand content has been removed to the pile hole 10. Thereby, the stabilizing liquid in the pile hole 10 is replaced with a good stabilizing liquid.

A supply pipe 18 is connected to the recovery pipe 16 by a branch via a valve (not shown). This supply pipe 18 is connected to an evaluation device 20 and supplies a portion of the stable liquid flowing through the recovery pipe 16 to the evaluation device 20 . Here, an amount of the stabilizing liquid that is approximately 1/5 to 1/30 of the flow rate flowing through the recovery pipe 16 is supplied to the supply pipe 18 . In this embodiment, the amount of the stabilizer flowing through the supply pipe 18 is set to about 1/15 of the stabilizing liquid flowing through the recovery pipe 16.

The evaluation device 20 includes a first specific gravity measuring section 21 , a second specific gravity measuring section 22 , a mud tank 23 , a cyclone device 25 , and a viscosity measuring section 26 . The stabilizing liquid supplied to the first specific gravity measuring section 21 , the second specific gravity measuring section 22 , and the viscosity measuring section 26 is accumulated in the muddy water tank 23 and then supplied to the plant 17 .

In the evaluation device 20, the supply pipe 18 is connected to a cyclone device 25 as a sand removal device. Further, a branch pipe of the supply pipe 18 is connected to the first specific gravity measuring section 21 via a valve 21v. The first specific gravity measurement unit 21 measures the specific gravity (first measurement value) of the stabilizing liquid flowing through the supply pipe 18 . The first specific gravity measurement unit 21 includes a cylindrical container 21c with an open top and a constant capacity, and a pressure gauge 21a that measures the weight of the stabilizing liquid in the container 21c.

A branch pipe is connected to the lower end of the container 21c, and a stabilizing liquid is supplied to the container 21c from below. Due to this supply, the stable liquid inside the container 21c flows upward and overflows from the upper opening of the container 21c. Further, a drain pipe 21d is provided below the container 21c of the first specific gravity measuring section 21 via a valve to drain the stabilizing liquid inside the container 21c as necessary.

The pressure gauge 21a is attached at a position (mounting position) a predetermined distance (for example, 1 m) lower than the upper surface of the container 21c. Then, the pressure gauge 21a measures the weight (pressure) of the stabilizing liquid in the container 21c located above the mounting position, and transmits the measured value to the management unit 30 as the specific gravity of the stabilizing liquid.

Further, a branch pipe of the supply pipe 18 is connected to the viscosity measuring section 26 . The viscosity measurement unit 26 measures the viscosity of the stable liquid flowing through the supply pipe 18. In this embodiment, a vibratory viscometer is used as the viscosity measuring section 26.

The cyclone device 25 connected to the supply pipe 18 is a centrifugal separator that separates sand (soil particles with a particle size of 0.075 mm or more) contained in the stabilizing liquid. This cyclone device 25 discharges the sand separated from the stable liquid flowing through the supply pipe 18 from below. Further, the cyclone device 25 discharges the stable liquid from which the sand has been separated into the muddy water tank 23 via a discharge pipe 28 connected to the upper part. Details of this cyclone device 25 will be described later.

A branch pipe of the discharge pipe 28 is connected to the second specific gravity measuring section 22 via a valve. The second specific gravity measuring section 22 measures the specific gravity of the stabilizing liquid flowing through the discharge pipe 28. Here, the second specific gravity measuring section 22 has the same configuration as the first specific gravity measuring section 21. The second specific gravity measuring section 22 also includes a cylindrical container 22c with a constant capacity and a pressure gauge 22a that measures the weight (pressure) of the stabilizing liquid in the container 22c. Furthermore, a drain pipe 22d is provided below the container 22c of the second specific gravity measuring section 22 via a valve.

Furthermore, the evaluation device 20 includes a management unit 30. The management unit 30 is connected to the first specific gravity measuring section 21, the second specific gravity measuring section 22, and the viscosity measuring section 26, and acquires the measurement values measured by these.

The management unit 30 includes a control section 31 and a display section 32.
The control unit 31 calculates the sand fraction contained in the stabilizing liquid. The sand fraction is the volume ratio of sand present in muddy water (stable liquid). The control unit 31 acquires the specific gravity measured by the first specific gravity measuring unit 21 (first measured value) and the specific gravity measured by the second specific gravity measuring unit 22 (second measured value). Then, the control unit 31 calculates the sand fraction using the first measurement value, the second measurement value, and a sand content calculation formula (formula (2) described later) stored in advance. Details of the calculation of this sand fraction will be described later. Then, the control unit 31 stores the calculated sand fraction, the measured specific gravity of the stabilizing liquid (first measurement value), and the viscosity acquired from the viscosity measurement unit 26 in the memory.

Furthermore, the management unit 30 controls the opening and closing of the valves 21v and 22v of the first specific gravity measuring section 21 and the second specific gravity measuring section 22, and the valves of the drain pipes 21d and 22d.
The display section 32 is a display that displays the specific gravity, viscosity, and sand fraction of the stabilizing liquid.

<Cyclone device 25>
Next, details of the cyclone device 25 for removing sand will be explained.
Here, in order to separate the sand component, consideration is given to the sedimentation rate of the sand calculated from the effective diameter of the cyclone device 25 and the residence time of the stabilizing liquid in the cyclone device 25.
The settling velocity (V) of sand in the cyclone device 25 is expressed by the Stokes equation (Equation (1) below).
V=(ρs-ρw) ^gD2 /18μ=(ρs-ρw) ^Vt2D2 / ^18μr ...(1)

Here, ρs is the density of sand (2.65×10 ³ kg/m ³ ), ρw is the density of water (1.00×10 ³ kg/m ³ ), g is the gravitational acceleration (9.807 m/s ² ), and μ is the muddy water. , D is the diameter of the sand particle (m), r is the radius of the centrifugal field (m), and Vt is the circumferential velocity (m/s).
As shown in equation (1) above, the settling speed of sand is influenced by the diameter, circumferential velocity, and viscosity of the sand particles to be removed.

The grain size of the sand is 0.075mm to 2mm. In this embodiment, the cyclone device 25 is set so as to be able to remove the particle size of sand contained in the stabilizing liquid, taking into consideration the properties of the earth and sand generated at the actual site. Further, during the work of replacing the stabilizing liquid in the pile hole 10, the peripheral speed of the cyclone device 25 is adjusted in consideration of fluctuations in the viscosity of the stabilizing liquid. Since this circumferential speed is determined by the diameter (shape) of the cyclone device 25 and the flow rate of the cyclone device 25, it is adjusted by the speed of the stabilizing liquid (inflow speed). Note that if the viscosity of the muddy water is expected to further increase, the peripheral speed of the cyclone device 25 is further increased.

<How to calculate sand fraction>
Next, a method for calculating the sand fraction executed by the control unit 31 will be described using FIGS. 2 and 3. Here, the sand content (%) calculated using the calculation method of this embodiment is referred to as a converted sand content.
The control unit 31 of this embodiment calculates the converted sand content x (%) using the following equation (2).
x=140×(ρi−ρf)/(2.65−ρf)…(2)
Here, ρi and ρf are the specific gravity of the stable liquid before passing through the cyclone device 25 (first measured value) and the specific gravity of the stable liquid after passing (second measured value), respectively. This calculation of the converted sand content is obtained from the difference in specific gravity and the difference in the loss of sand content, assuming that the difference in specific gravity is mainly due to the sand content.

Specifically, a conventional method of measuring the sand fraction using a sand meter 50 will be described with reference to FIG. 2(a). In this sand content meter 50, 100 mL of stabilizing solution is used. The sand content meter 50 measures the sand fraction by removing particles of 75 μm or less with a sieve, washing with water, and measuring the stacked volume of sand (soil particles of 75 μm or more) remaining in the water 51. get. For example, a sand content of 5% means that 5 mL of sand is contained in 100 mL of the stabilizing solution placed in the sand meter 50.

The mass difference due to the difference in specific gravity before and after passing through the cyclone device 25 per 100 mL of the stabilized liquid is shown as follows.
Mass difference due to specific gravity difference = 100 × (ρi - ρf)...(3)

Here, as shown in the diagram of the structure of soil (sand) in Figure 2(b), the volumes of air, water, and soil particles are respectively Va, Vw, and Vs, and the total volume of air and water is Vv, air Let V be the total volume of water and soil particles.
The mass difference due to the loss of sand before and after passing through the cyclone device 25 is determined by the porosity of the sand 52 in the part of the sand meter 50 where the sand is deposited as n (=Vv/V×100), and the density of the sand as n (=Vv/V×100). When ρs (=2.65 g/cm ³ ), it is shown as follows.
Mass difference due to sand loss = (ρs - ρf) x x x (1 - n/100)... (4)

Since the mass difference due to specific gravity before and after passing through the cyclone device 25 and the mass difference due to sand loss are (approximately) equal, the following formula can be obtained from the above equations (3) and (4).
100×(ρi−ρf)=(ρs−ρf)×x×(1−n/100)…(5)

When this equation (5) is transformed with respect to the converted sand content x, the following equation is obtained.
x=100(ρi−ρf)/((ρs−ρf)×(1−n/100))…(6)

Here, if α is a coefficient that takes into consideration the characteristics of the evaluation device 20 and the gap ratio of the sand 52, the value of the converted sand content x is expressed by the following equation. This coefficient α can be individually set for each usage condition of the evaluation device 20.
x=α×(ρi−ρf)/(ρs−ρf)
This time, from the correlation of the measured values during the experiment, α = 140, and the specific gravity of sand was set to 2.65, and the conversion was performed using the following formula.
x=140×(ρi−ρf)/(2.65−ρf)

<Relationship between sand content and converted sand content by conventional method>
FIG. 3(a) shows the sand content measured by the sand content meter 50 (according to the conventional method) and the converted sand content of the present invention for stable liquids with different properties. Furthermore, FIG. 3(b) shows a graph in which the horizontal axis represents the sand fraction value obtained by the conventional method and the vertical axis represents the converted sand content. According to this, the sand fraction obtained by the conventional method and the converted sand content almost correspond to each other, indicating that the converted sand content has almost the same accuracy as the conventional method.

<Measurement processing of evaluation device 20>
Next, measurement processing in the evaluation device 20 shown in FIG. 1 will be explained.
First, the pump 15 disposed in the pile hole 10 is driven to discharge the stabilizing liquid in the pile hole 10 to the plant 17 via the recovery pipe 16. Furthermore, in the plant 17, the adjusted stabilizing liquid is supplied to the pile hole 10.

Here, a part of the stabilizing liquid in the recovery pipe 16 is supplied to the cyclone device 25 of the evaluation device 20 via the supply pipe 18. In this case, since the valve 21v is open, the stabilizing liquid is supplied from the supply pipe 18 to the first specific gravity measuring section 21. In this embodiment, adjustment is made so that a part (for example, 30% or less) of the flow rate of the stabilizing liquid flowing through the evaluation device 20 flows to the first specific gravity measuring section 21 . This stabilizing liquid is supplied from below the container 21c of the first specific gravity measuring section 21, and causes the stabilizing liquid in the container 21c to flow upward and overflow from the top of the container 21c. The pressure gauge 21a of the first specific gravity measuring section 21 measures the pressure (specific gravity) of the stable liquid in the container 21c periodically (for example, every 5 seconds). The pressure gauge 21 a transmits the measured value (first measured value) of the stabilized liquid to the management unit 30 .

Furthermore, the stabilizing liquid is supplied to the viscosity measuring section 26 via a branch pipe of the supply pipe 18 . The viscosity measurement unit 26 measures the viscosity of the stabilizing liquid periodically (for example, every 5 seconds) and transmits the measured value (viscosity) to the management unit 30.

Further, the stable liquid from which sand has been removed by the cyclone device 25 is discharged to the muddy water tank 23 via the discharge pipe 28. In this case, the valve 22v is opened to supply the stabilizing liquid in the discharge pipe 28 to the second specific gravity measuring section 22. In this embodiment, the stabilizing liquid is adjusted to flow into the second specific gravity measuring section 22 at approximately the same flow rate as the first specific gravity measuring section 21 . Since this stabilizing liquid is gradually supplied from below the container 22c of the second specific gravity measuring section 22, the stabilizing liquid in the container 22c slowly flows upward and overflows from the top of the container 22c. The pressure gauge 22a of the second specific gravity measurement unit 22 periodically (for example, every 5 seconds) measures the pressure (specific gravity) of the stable liquid in the container 22c, and the measured value (second measurement value) of the stabilized liquid is measured. is supplied to the management unit 30.

The control unit 31 of the management unit 30 calculates the sand fraction using the acquired first measurement value and second measurement value and the sand content calculation formula. The control unit 31 associates the calculated sand fraction with the specific gravity (first measurement value) and viscosity of the stabilizing liquid acquired at the same time, and stores them in a built-in memory. Then, the control section 31 of the management unit 30 displays information regarding the stabilizing liquid (sand content, specific gravity, and viscosity) on the display section 32. The administrator monitors the measured values (sand content of the stabilizing liquid, etc.) displayed on the display unit 32.

Furthermore, the management unit 30 periodically (for example, every 30 minutes) closes the valves 21v and 22v and opens the valves of the drain pipes 21d and 22d. As a result, the stable liquid in the containers 21c, 22c is discharged from the lower ends of the containers (21c, 22c) of the first and second specific gravity measuring sections (21, 22). After a predetermined period of time (for example, several seconds) has passed, the valves of the drain pipes 21d and 22d are closed, and the valves 21v and 22v are opened to open the containers (21c, 22c) of the first and second specific gravity measurement sections (21, 22). After filling with stabilizing solution, measure the specific gravity of the stabilizing solution again. As a result, the evaluation device 20 is calibrated at regular time intervals.

<Specific example>
Here, the sand fraction of the recovered liquid will be explained.
For example, assume that the measured value of the first specific gravity measuring section 21 (first measured value) and the measured value of the second specific gravity measuring section 22 (second measured value) are the values shown in Table 1 below. In this case, since the equivalent sand content is equal to or higher than the judgment value (1.0%), the stabilizing liquid replacement work is continued. Then, when the converted sand content becomes smaller than the determination value, the stabilizing liquid replacement operation is stopped.

According to this embodiment, the following effects can be obtained.
(1) In this embodiment, a formula includes the specific gravity (first measured value) of the stabilizing liquid supplied to the cyclone device 25 and the specific gravity (second measured value) of the stabilizing liquid from which sand has been removed in the cyclone device 25. From this, calculate the sand content of the stabilizing solution. Thereby, the sand fraction of the stabilizing liquid can be efficiently measured.

(2) In this embodiment, a part of the stabilizing liquid collected from the pile hole 10 to the plant 17 is passed through the evaluation device 20, and the properties of the stabilizing liquid are evaluated in the evaluation device 20. Thereby, the properties of the stabilizing liquid flowing from the pile hole 10 to the plant 17 can be efficiently evaluated.

(3) In the present embodiment, a branch pipe of the supply pipe 18 is connected to the lower ends of the containers (21c, 22c) of the first and second specific gravity measurement units (21, 22). As a result, the stabilizing liquid is supplied from below to the containers 21c and 22c and flows upward, and the specific gravity of the stabilizing liquid is measured while gradually replacing a part of the inside of the containers 21c and 22c, so that sudden property changes can occur. It is possible to continuously and efficiently measure the specific gravity of the flowing stable liquid without causing any problems. Furthermore, the stabilizing liquid flows in several seconds from the supply pipe 18 to which the first specific gravity measuring section 21 is connected to the discharge pipe 28 to which the second specific gravity measuring section 22 is connected. Thereby, the first specific gravity measuring section 21 and the second specific gravity measuring section 22 can measure the specific gravity of almost the same stable liquid almost simultaneously with almost no delay.

(4) The first and second specific gravity measurement units (21, 22) of the present embodiment include pressure gauges 21a, 22a provided in the containers (21c, 22c) at positions 1 m from the open upper end. Thereby, the pressure gauges 21a, 22a measure the pressure inside the containers 21c, 22c, so that the specific gravity of the stable liquid in each container 21c, 22c can be efficiently measured.

(5) In the present embodiment, the control section 31 of the management unit 30 displays on the display section 32 the measured values of the specific gravity, viscosity, and sand fraction of the stabilizing liquid measured at the same time. This makes it possible to grasp multiple properties necessary for property management of the stable liquid at the same time.

(6) In the present embodiment, the control section 31 of the management unit 30 periodically opens the valves of the drain pipes 21d and 22d of the first specific gravity measuring section 21 and the second specific gravity measuring section 22. Thereby, the evaluation device 20 can be calibrated at regular time intervals.

This embodiment can be modified and implemented as follows. This embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
- In the above embodiment, the specific gravity difference obtained by subtracting the second measurement value measured by the second specific gravity measurement unit 22 from the first measurement value measured by the first specific gravity measurement unit 21 is calculated from the specific gravity (2.65) of the sand. The sand fraction was calculated by dividing the second measurement value by the subtracted specific gravity difference and multiplying by a coefficient (140). The sand fraction of the stabilizer is not limited to this coefficient (140) or the calculation method; for example, the sand fraction can be calculated by dividing the first measurement value by the second measurement value and using the corresponding conversion table. It is only necessary that the sand fraction can be measured using the comparison result between the first measurement value and the second measurement value. Furthermore, the sand fraction may be adjusted and calculated according to the measured viscosity. Specifically, the value obtained by comparing the first measured value and the second measured value is corrected using a correction value corresponding to the measured viscosity value, and the sand fraction is calculated according to this correction value.

- In the above embodiment, the control section 31 of the management unit 30 displayed the calculated sand fraction and the measured specific gravity and viscosity on the display section 32. In addition to this, the control unit 31 may determine whether or not the calculated sand fraction exceeds a reference value, and may indicate the determination result. Furthermore, the management unit 30 may manage information regarding the properties of the stabilizing liquid other than the sand fraction, specific gravity, and viscosity, such as the pH of the stabilizing liquid and the amount of filtrated water. Furthermore, the management unit 30 may be provided with a communication section to transmit the sand fraction, specific gravity, and viscosity to the administrator's terminal.

- In the above embodiment, the administrator monitors the sand fraction displayed on the display section 32 of the management unit 30. Alternatively, the control unit 31 of the management unit 30 may automatically stop collecting and supplying the stabilizing liquid when the sand content becomes equal to or less than the determination reference value. In this case, valves are provided in the recovery pipe 16 and the supply pipe. When the sand fraction becomes equal to or less than the determination reference value, the control unit 31 outputs an instruction signal to close these valves and controls the supply and recovery of the stabilizing liquid.

- In the above embodiment, the recovered liquid flowing from the pile hole 10 to the plant 17 was evaluated. The stabilizing liquid to be evaluated is not limited to the recovered liquid collected from the pile hole 10, but may be a supply liquid supplied to the pile hole 10. In this case, the evaluation device 20 is attached to the pipeline that supplies the stabilizing liquid from the plant 17 to the pile hole 10 via a supply pipe. For example, as shown in Table 2 below, if the sand content contained in the supplied stabilizing liquid is equal to or less than the reference value (for example, 1.0%), the supply of the stabilizing liquid is continued.

Then, if the sand content contained in the supplied stabilizing liquid exceeds a reference value (for example, 1.0%), an alarm may be displayed on the display unit 32. Furthermore, this alarm may be sent to the administrator's terminal.
Furthermore, the evaluation device 20 may be provided in each of the pipe line for the recovered liquid flowing from the pile hole 10 to the plant 17 and the pipe line for the supply liquid supplied from the plant 17 to the pile hole 10.

- In the above embodiment, the stabilizing liquid supplied to the evaluation device 20 via the supply pipe 18 is temporarily stored in the mud tank 23 and then returned to the plant 17. Instead of temporarily accumulating the stabilizing liquid in the muddy water tank 23, the stabilizing liquid supplied to the evaluation device 20 may be returned to the downstream side of the pipe line (recovery pipe 18 in the above embodiment) to which the supply pipe 18 is connected. good.
- In the above embodiment, the cyclone device 25 was used as the sand removal device. The device is not limited to the cyclone device 25 as long as it can remove sand.

DESCRIPTION OF SYMBOLS 10... Pile hole, 11... Stabilizing liquid, 15... Pump, 16... Recovery pipe, 17... Plant, 18... Measurement supply pipe, 20... Evaluation device, 21... First specific gravity measurement part, 21a, 22a... Pressure gauge, 21c , 22c... Container, 21d, 22d... Drain pipe, 21v, 22v... Valve, 22... Second specific gravity measuring section, 23... Measuring mud tank, 25... Cyclone device, 26... Viscosity measuring section, 28... Discharge pipe, 30 ...Property management section, 31...Control section, 32...Display section, 50...Sand meter, 51...Water, 52...Sand.

Claims (2)

A specific gravity measuring device for measuring the specific gravity of a stabilizing liquid,
a cylindrical container with a fixed capacity and an open top;
Equipped with a pressure gauge to measure the weight of the stable liquid in this container,
The pressure gauge is installed at a mounting position corresponding to the volume for measuring specific gravity from the upper end of the container ,
The lower end of the container is connected to a supply pipe through which the stabilizing liquid filled inside the hole flows,
A stabilizing liquid is supplied to the container from below via the supply pipe,
After the stabilizing liquid supplied inside the container flows upward, it overflows from the upper opening of the container,
A specific gravity measuring device characterized in that the weight of the stable liquid above the mounting position is determined as the specific gravity of the stable liquid by measuring the pressure of the stable liquid in the container using the pressure gauge. . A drain pipe is provided below the container to drain the stabilizing liquid inside the container via a valve,
2. The method according to claim 1, wherein the specific gravity of the stabilizing liquid is calibrated by discharging the stabilizing liquid from the container by closing a valve of the supply pipe and opening a valve of the drain pipe. The specific gravity measuring device described.