JP2010090696A - Suction force generation device and suction force generation method by siphon, and construction method for improving vacuum consolidated ground - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a suction force generation device and a suction force generation method capable of generating a suction force on the principle of siphon even without separating the flows of water and gas from each other and a construction method for improving a vacuum consolidated ground capable of reducing or eliminating a load by banking and shortening a ground improvement period by promoting vacuum consolidation in a ground improvement. <P>SOLUTION: This suction force generation device includes a siphon function maintaining device 3 which comprises a first pipe 1 extending from the upper side downward and a second pipe 2 connected to the first pipe on the upper side, in which, due to the water level difference &Delta;H between the bottom end 1a side of the first pipe and the top end 2a side of the second pipe, a suction force acts from the tip of the second pipe toward the bottom end of the first pipe through a siphon function, and which maintains a siphon function by supplying water into a drain passage formed from the tip of the second pipe toward the bottom end of the first pipe. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a siphon suction power generation device, a suction force generation method, and a vacuum consolidation ground improvement method using the suction force generation device or the suction force generation method.

  2. Description of the Related Art A suction device using a vacuum pump is known as a device that generates a suction force to suck and drain water. In the conventional technology, for example, after placing a vertical drain in soft ground, a method of promoting consolidation of the ground by using a vacuum pump suction device to apply a negative pressure to decompress the ground is used. (For example, see Patent Documents 1 to 4).

JP 2000-328550 A JP 2001-226951 A JP 2002-138456 JP JP 2003-261929 A

  In a suction device using a conventional vacuum pump, suction is performed only by the capability of the vacuum pump. For this reason, according to the conventional suction device, the suction force which promotes compaction beyond the capability of the vacuum pump cannot be applied. For this reason, in the conventional vacuum consolidation method for soft ground, if the suction force is insufficient with only the vacuum pump, loading by embankment has to be used in combination.

  In addition, regarding a suction device that uses the force of the vacuum pump and the force due to the difference in the water surface position, a volume reduction method for soft bottom water has been proposed for the purpose of suctioning pore water in the ground below the water surface (patent) Reference 4). In this prior art, the water surface is located at a position higher than the ground for suctioning the pore water, so that the compressive force due to water pressure acts to squeeze the pore water, and the ground for improvement is underwater. It can be applied only under the condition that the ground surface position is lower than the water level of the drainage part (decompression chamber). This conventional method does not assume that the ground to be improved is on land, and the hose guided from the top end position of the improved ground surface is coupled to the side surface of the decompression chamber.

  Under conditions that apply a large suction force, it is necessary to consider the vaporization of dissolved air, etc., and the presence of air flowing in from the airtight leaking part of the water pipe. Simply connecting the pipe to the pipe will cause the water and gas flows to separate, so the suction force according to the siphon principle will not work. That is, in the case of land on the ground, according to the prior art, it has not been possible to exert a suction force exceeding the capacity of the vacuum pump.

  An object of the present invention is to provide a suction force generation device and a suction force generation method capable of generating a suction force according to the principle of siphon without separation of water and gas flows. It is another object of the present invention to provide a vacuum consolidation ground improvement method capable of promoting vacuum consolidation in ground improvement and realizing reduction or omission of loading due to embankment and shortening of the ground improvement period.

  An attraction force generating apparatus for achieving the above object includes a first tube extending from an upper portion toward a lower portion, and a second tube connected to the first tube at the upper portion, the first tube Suction by which a suction force acts by a siphon function from the tip of the second tube toward the bottom of the first tube due to a water level difference between the lower end of the tube and the tip of the second tube A siphon function maintaining device for maintaining a siphon function by supplying water into a drainage path formed from a distal end side of the second pipe toward a lower end side of the first pipe. It is characterized by providing.

  According to this suction force generation device, even when water with a high air mixing rate is sucked and drained from the distal end side of the second pipe, the water is supplied into the drainage path by the siphon function maintaining device. Since the air mixing rate in the pipe can be reduced and the flow rate of the water flowing down in the first pipe can be increased, the flow of water and gas does not separate in the first pipe and the gas-liquid two-phase A flow is formed and siphon function can be maintained. Thus, since the suction force according to the principle of siphon can be generated continuously, the suction force by siphon can be used efficiently. In addition, you may make it supply the water into a drainage path | route by sending the water drained from the lower end of a 1st pipe | tube to a siphon function maintenance apparatus.

  In the suction force generator, it is preferable that the water supplied into the drainage path is deaerated water with a reduced amount of dissolved air so that the siphon function is not easily interrupted. By supplying deaerated water into the drainage path, the amount of air generated from the water under the negative pressure action is reduced, and the amount of air mixed in the water does not increase, so that the siphon function is not easily interrupted.

  In addition, in a condition where the level surface of the water to be sucked and drained is lower than the uppermost part of the second pipe, in order to prevent the loss of negative pressure due to the height difference, the water enters the drainage path in the second pipe. It is preferable to provide a negative pressure loss prevention device that drains before inflow and prevents the loss of the negative pressure by filling the inside of the drainage passage having a height difference with gas. If the water level of the water to be sucked is lower than the uppermost position of the second pipe, a negative pressure loss occurs due to the height difference, but as a countermeasure against this, the water before the drainage path with the height difference is pumped up. By draining the gas, the gas is filled in the drainage path having a difference in elevation, thereby preventing a negative pressure loss. In addition, it is preferable that the pumped water is supplied to the above-mentioned water supply by sending it to the siphon function maintaining device.

  Moreover, it is preferable that the amount of dissolved air is reduced by dissolving a soluble substance in the water supplied into the drainage path to raise the boiling point of the water, thereby making it difficult to interrupt the siphon function.

  Further, by providing a temperature rise prevention portion on at least a part of the outer surface of the first pipe and / or the second pipe, vaporization associated with negative pressure action is suppressed by keeping the temperature and water temperature in the pipe low. Thus, it is preferable to make the siphon function difficult to interrupt.

  The suction force generator is preferably used in combination with a power device using a vacuum pump. Thereby, when the siphon function is stopped, the resumption can be easily performed, and the suction force that is insufficient only by the siphon function can be compensated.

  A suction force generation method for achieving the above object is provided between a lower end side of a first tube extending from an upper portion toward a lower portion and a distal end side of a second tube connected to the first tube at the upper portion. A suction force generating method in which a suction force is applied by a siphon function from the tip of the second tube toward the lower end of the first tube due to a difference in water level of the second tube. The siphon function is maintained by supplying water into a drainage path formed toward the lower end side of one pipe.

  According to this suction force generation method, even when water with a large air mixing rate is sucked and drained from the tip side of the second pipe, the air mixing rate in the first pipe can be obtained by supplying water into the drainage path. And the flow rate of water flowing down in the first pipe can be increased, so that a gas-liquid two-phase flow is formed in the first pipe without separating the water and gas flows, Siphon function can be maintained. Thus, since the suction force according to the principle of a siphon can be generated continuously, the suction force by a siphon can be utilized efficiently. In addition, you may make it perform the said water supply by supplying the water drained from the lower end of a 1st pipe | tube into a drainage channel | path.

  A vacuum consolidation ground improvement method for achieving the above object is characterized in that ground improvement by vacuum consolidation is performed on soft ground using the above-described suction force generator or suction force generation method.

  According to this vacuum consolidation ground improvement method, the vacuum consolidation in the ground improvement can be promoted by using the suction of the siphon function by the suction force generation device or the suction force generation method described above, and the load reduction by the embankment can be reduced or omitted. Can reduce the amount of materials and equipment used, shorten the work period, increase the suction force compared to the conventional vacuum consolidation method, and efficiently apply the suction force. The ground improvement period required for the soft ground to reach a predetermined strength can be shortened.

  The second pipe in the suction force generation device or suction force generation method described above is connected to a drain material placed in soft ground, and between the groundwater level surface of the soft ground to be improved and the lower end side of the first pipe The ground can be consolidated by sucking the pore water in the soft ground G by the suction force by the siphon function resulting from the difference in water level.

  According to the suction force generation device and the suction force generation method of the present invention, a gas-liquid two-phase flow is formed in the first pipe without separation of water and gas flows, so that the siphon function can be maintained, and the principle of siphon is followed. A suction force can be generated continuously.

  According to the vacuum consolidation ground improvement method of the present invention, by using the above-described suction force generation device capable of continuously generating suction force according to the principle of siphon, vacuum consolidation in ground improvement is promoted, and load reduction by embankment can be reduced. Omission and shortening of ground improvement period can be realized.

It is a figure showing roughly the composition of the attraction power generator by a 1st embodiment. It is a figure which shows schematically the structure of the attraction | suction force generator which was made to supply deaeration water to the drainage path in a horizontal pipe | tube from the siphon function maintenance apparatus of FIG. FIG. 3 is a graph showing the relationship between temperature and vapor pressure for a solvent and a solution in order to explain a preferred embodiment of the suction force generator of FIGS. 1 and 2. It is a figure which shows the example which provided the temperature rise prevention part in the horizontal pipe | tube and the vertical pipe | tube of the attraction | suction force generator of FIG. 1, FIG. It is a figure which shows another example which provided the temperature rise prevention part in the horizontal pipe | tube and the vertical pipe | tube of the attraction | suction force generator of FIG. 1, FIG. It is a figure for demonstrating the negative pressure loss which generate | occur | produces in the attraction | suction force generator of FIG. It is a figure which shows roughly the structure which provided the negative pressure loss prevention apparatus for preventing a negative pressure loss in the attraction | suction force generator of FIG. It is a figure which shows roughly the structure of the vacuum consolidation ground improvement system which performs the vacuum consolidation ground improvement construction method by 2nd Embodiment. It is a fragmentary figure which shows the modification of the vacuum consolidation ground improvement system by 2nd Embodiment. It is a figure which shows roughly the experimental apparatus used in the present Example. In this example, the negative pressure acting in the horizontal water pipe is measured when the siphon function is maintained with the supply water amount maintained at 20 L / min and the siphon function is low with the supply water amount being 10 L / min. It is a figure which shows the result. FIG. 1 is a schematic diagram (a) for explaining the gas-liquid two-phase flow of water and air by the siphon function in the suction force generator of FIG. 1 and for explaining the state where the gas-liquid two-phase flow of water and air cannot be realized. It is a schematic diagram (b).

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

<First Embodiment>
FIG. 1 is a diagram schematically showing a configuration of a suction force generator according to the first embodiment.

  1 includes a vertical pipe 1 that is a first pipe that extends in the vertical direction from the upper part toward the lower part, and a horizontal pipe 2 that is a second pipe that extends in the horizontal direction above the vertical pipe 1. And a siphon function maintaining device 3 that maintains the siphon function by supplying water to the horizontal pipe 2. A drainage path is formed from the front end 2 a side of the horizontal pipe 2 toward the lower end 1 a side of the vertical pipe 1. The vertical tube 1 and the horizontal tube 2 are made of a cylindrical tube made of metal or plastic.

  The siphon function maintaining device 3 includes a tank 4 disposed at the top of the horizontal pipe 2 for storing water, a water supply pipe 5 provided between the bottom of the tank 4 and the horizontal pipe 2, And a valve 6 provided on the way, and the water in the tank 4 is supplied to the drainage path of the horizontal pipe 2 through the water supply pipe 5 by opening the valve 6.

  As shown in FIG. 1, when the lower end 1a of the vertical pipe 1 is in water, the horizontal pipe is caused by the siphon function caused by the water level difference ΔH between the drainage level face H1 and the water level face H0 on the tip 2a side of the horizontal pipe 2. As a suction force is generated from the front end 2a side of 2 toward the lower end 1a side of the vertical tube 1, water flows in the horizontal direction c in the horizontal tube 2 and in the vertical direction d in the vertical tube 1. In addition, when the drainage surface of FIG. 1 does not reach the lower end 1a of the vertical pipe 1, the siphon function resulting from the water level difference between the lower end 1a of the vertical pipe 1 and the water level surface H0 on the tip 2a side of the horizontal pipe 2 Thus, a suction force is generated toward the lower end 1a side of the vertical pipe 1.

  Here, in order to apply the suction force in accordance with the siphon principle under the condition where the gas is contained in the horizontal pipe 2, the water and the gas must be flowed down integrally in the vertical pipe 1 without being separated. That is, as shown in FIG. 12 (a), even if air and water flow separately in the direction c in the horizontal pipe 2, the air is taken in as numerous bubbles B in the vertical pipe 1, and the gas-liquid 2 By flowing down in the direction d integrally as a phase flow, the siphon principle is established in the vertical pipe 1 and a suction force due to the water level difference ΔH is generated. As shown in FIG. 12 (b), if air and water flow separately in a horizontal pipe, and if water and air flow separately in a vertical pipe, the siphon principle does not hold, and the suction force due to the water level difference. Will not occur.

  In order to maintain the siphon function, the flow of gas in the vertical pipe 1 is necessary to maintain the siphon function because drainage is performed by the suction force in accordance with the siphon principle. Must be separated from the liquid flow, and a gas-liquid two-phase flow (bubble mixed flow) must be formed as shown in FIG. 1, the water in the tank 4 of the siphon function maintaining device 3 remains in the vertical direction b even when water with a high air mixing rate is sucked and drained from the tip 2a side of the horizontal pipe 2. By being supplied into the horizontal pipe 2 through the water supply pipe 5, the water sucked and flowing in the horizontal direction c has a low air mixing rate, and the flow rate of the water flowing down in the vertical pipe 1 increases. For this reason, in the vertical pipe 1, the gas flow and the liquid flow are not separated, and a gas-liquid two-phase flow in which water and gas are mixed is stably formed, and the siphon functions.

  As described above, the flow of water and air passing through the drainage path in the horizontal pipe 2 in FIG. 1 becomes a gas-liquid two-phase flow (bubble mixed flow) in the vertical pipe 1 so that the siphon function is easily exhibited. For this reason, it is preferable to reduce the air mixing rate in the pipe and increase the flow rate of the water flowing down in the pipe. However, according to the suction power generation device of this embodiment, water is supplied from the siphon function maintaining device 3 to the drainage path. Since the air mixing rate in the gas-liquid two-phase flow flowing down the vertical pipe 1 can be reduced and the flow rate of water flowing down the vertical pipe 1 can be increased, the siphon function Thus, the suction force according to the siphon principle can be continuously generated.

  Further, the amount of water supplied from the siphon function maintaining device 3 is adjusted by the valve 6 in accordance with the amount of air sucked from the horizontal pipe 2 to control the water flow rate, that is, the flow velocity, and smoothly flow down the air together with the water. Can do.

  Next, a preferable aspect of the suction force generator of this embodiment will be described with reference to FIGS.

  2 is provided with a deaerated water production device 26 and a depressurized sealed chamber 21 in the suction force generating device of FIG. 1, and the deaerated water is supplied from the siphon function maintaining device 3 to the drainage path in the horizontal pipe 2. It is comprised so that it may supply.

  The deaerated water production apparatus 26 is, for example, an apparatus in which an ultrasonic wave generation source is arranged in a tank in which water is stored, an apparatus for reducing the pressure in a decompression container in which water is stored, or an apparatus for heating a tank in which water is stored. However, it may be a device combining these. In addition, tap water, rain water, ground water, sea water, etc. can be used as water.

  As shown in FIG. 2, the deaerated water produced by the deaerated water production device 26 is supplied to the tank 4 of the siphon function maintaining device 3, and the deaerated water is supplied from the tank 4 to the drainage path in the horizontal pipe 2. The gas-liquid two-phase flow that flows down the vertical pipe 1 because the amount of dissolved air in the water in the drainage path is reduced, the amount of air generated from the water under the negative pressure action is reduced, and the amount of air mixed in the water does not increase The amount of air inside can be further reduced, and the siphon function is less likely to be interrupted.

  Further, as shown in FIG. 2, a sealed chamber 21 having a sealed structure is provided. The vertical pipe 1 extends into the sealed chamber 21 and is drained from the lower end 1 a, and the inside of the sealed chamber 21 is decompressed by the vacuum pump 25. Thus, when a certain level of negative pressure is applied in the horizontal pipe 2, the water drained by the pumping pump 22 becomes deaerated water. Therefore, the deaerated water is passed through the drain pipe 23 in the directions e and f. Alternatively, the tip 23a may be supplied to the tank 4 of the siphon function maintaining device 3. In this case, the deaerated water production apparatus 26 of FIG. 2 may be omitted.

  When the lower end 1a of the vertical pipe 1 is in water in the sealed chamber 21, the negative pressure resulting from the water level difference ΔH between the water level surface H1 and the water level surface H0 on the tip 2a side of the horizontal tube 2 and the sealed chamber 21 Due to the negative pressure generated by reducing the pressure inside the vacuum pipe 25, the negative pressure in the horizontal pipe 2 increases, for example, a negative pressure of about -90 kPa.

  The suction force generation device of FIG. 2 includes a sealed chamber 21 in which the vertical pipe 1 extends to collect water from the vertical tube 1 and a vacuum pump 25 that decompresses the inside of the sealed chamber 21, so that the suction force by the vacuum pump 25 is obtained. Since the suction force due to the siphon function by the horizontal tube 2 and the vertical tube 1 can be generated, a large suction force exceeding the capability of the vacuum pump 25 can be obtained. In addition, when the siphon function is stopped, the vacuum pump 25 can easily restart the function.

  In addition, as shown in FIG. 2, the external drainage pipe 24 is connected to the middle of the drainage pipe 23 via the valve 24a, and the water pumped up by the pumping pump 22 is passed through the external drainage pipe 24 in the external direction g by opening and closing the valve 24a. By appropriately discharging, the supply amount of deaerated water to the tank 4 of the siphon function maintaining device 3 can be adjusted.

  Next, in the suction force generator of FIGS. 1 and 2, the dissolved air amount of water is reduced by dissolving a soluble substance such as sodium chloride in the water supplied from the tank 4 of the siphon function maintaining device 3. It may be reduced to increase the boiling point of water, make the siphon function difficult to disrupt, and enhance the suction force by the siphon.

That is, if the vapor pressure of a certain solvent is p _0, and the vapor pressure of the solution when a non-volatile solute is dissolved in this solvent is p, then p ₀ > p at the same temperature, and the vapor pressure decreases. If the concentration of the solution is not too high, the vapor pressure drop of the solution is equal to the solute mole fraction. This relationship is called Raoult's law. When the amount of the solvent is N and the amount of the solute is n, it can be expressed as the following formula (A).

(P ₀ −p) / p ₀ = n / (N + n) (A)

  FIG. 3 shows the relationship between the temperature and the vapor pressure of the solvent and the solution. As can be seen from FIG. 3, the vapor pressure at the same temperature is higher than that of the solvent alone. Falls. This means that when the pressure is lowered while keeping the temperature constant, the solution in which the non-volatile solute is dissolved is less likely to boil than the solvent alone.

  Therefore, it is possible to increase the boiling point and decrease the amount of dissolved oxygen by dissolving a soluble substance such as sodium chloride in the water supplied from the siphon function maintaining device 3. For this reason, it becomes difficult to generate air from water in the drainage path of the suction power generation device of FIGS. 1 and 2, and the siphon function is not easily interrupted.

  Next, the temperature rise in the horizontal pipe 2 and the vertical pipe 1 is provided by providing the horizontal pipe 2 and the vertical pipe 1 of the suction force generating device of FIGS. In addition, by keeping the water temperature low, the vaporization associated with the negative pressure action may be suppressed to make it difficult for the siphon function to be interrupted.

  In the example of FIG. 4, a temperature rise prevention cover 28 made of a heat insulating material such as styrene foam is arranged on the outer periphery of the horizontal pipe 2 and the vertical pipe 1 of the suction force generator of FIGS. It is. According to the configuration of FIG. 4, since the horizontal pipe 2 and the vertical pipe 1 are not heated by the solar heat by the temperature rise prevention cover 28, the air temperature and water temperature in the horizontal pipe 2 and the vertical pipe 1 can be kept low, and negative It is possible to suppress the siphon function from being interrupted by suppressing the vaporization associated with the pressure action. The temperature rise prevention cover 28 does not necessarily need to cover the entire surface of the tubes 1 and 2, and may be disposed only in a portion exposed to sunlight, for example.

  In the example of FIG. 5, a relatively thin tube 29 is wound around the outer peripheral surfaces of the horizontal tube 2 and the vertical tube 1 of the suction force generator of FIGS. It is arranged so that cold water flows in the pipe 29. According to the configuration of FIG. 5, the horizontal pipe 2 and the vertical pipe 1 are cooled by flowing cold water in a spiral shape through the pipe 29 and the temperature thereof is lowered, so that the air volume in the vertical pipe 1 is reduced and the negative pressure is reduced. It is possible to suppress the siphon function from being interrupted by suppressing the vaporization due to the action. It should be noted that the range in which the thin tube 29 is wound around the tubes 1 and 2 may be only a part of the tubes 1 and 2.

  Here, according to Charles' law, the gas volume V can be expressed by the following equation (B) at an absolute temperature T under a constant pressure condition.

V = kT (B)
Where k is a positive constant

  This equation shows that the gas volume expands at high temperature conditions. For this reason, raising the temperature of the air in the vertical pipe 1 shown in FIGS. 1 and 2 expands the volume of dissolved air and suction air, thereby reducing the siphon function. Therefore, by eliminating the influence of solar heat on the horizontal tube 2 and the vertical tube 1 as shown in FIG. 4, and by lowering the temperature of the horizontal tube 2 and the vertical tube 1 as shown in FIG. Decline can be prevented.

Next, the principle of the suction force generator of this embodiment will be described.
The bubble rising speed ν _a due to buoyancy can be evaluated by the following equation (1) based on the balance between buoyancy and drag.

ν _a = [8 gr _a / (3C _D )] ^0.5 (1)

Here, r _a is the radius of the bubble, the size of the bubble can be a half of the pipe diameter at the maximum. Also, C _D is the drag coefficient is given by 0.5.

When the water flow cross-sectional area of the pipe is A, the maximum bubble radius ra _(max) can be expressed by the following equation (2).

r _{a (max)} = (A / π) ^0.5 (2)

When the flow rate of water flowing into the vertical pipe is Q, the flow velocity ν _w of the water flowing down the vertical pipe can be evaluated by the following equation (3).

ν _w = Q / A (3)

  The above formula (3) increases the flow rate by reducing the inner diameter of the vertical tube and reducing the cross-sectional area of water flow with respect to the flow rate flowing from the horizontal tube, or by supplying water into the drainage path. It shows that the flow rate increases.

Here, in the vertical pipe, by setting the conditions such that the flow velocity of water flowing down the vertical pipe ν _w > the rising speed ν _a of the bubbles, the bubbles are entrained in the flow of water, and the gas-liquid mixed phase flow (gas Since the two-phase liquid) is formed, the siphon functions.

In order to satisfy the above condition (ν _w > ν _a ), the following methods and means are conceivable.
(1) The maximum diameter of bubbles that can be formed is reduced, and the rising speed of bubbles is suppressed (formulas (1) and (2)).
(2) By devising the components and temperature of the flowing water, the maximum bubble diameter is reduced, and the rising speed of the bubbles is suppressed (Formula (1)).
(3) The vertical flow rate is narrowed or the amount of water supplied is increased to increase the water flow rate (formula (3)).

  The suction force generator of this embodiment has a configuration using the above (1), (2), and (3). In order to enhance the effect of (3) above, the inner diameter of the vertical pipe 1 is made smaller than the inner diameter of the horizontal pipe 2 so that the cross-sectional area of the vertical pipe 1 is smaller than the cross-sectional area of the horizontal pipe 2. Alternatively, a gradually decreasing portion in which the inner diameter gradually decreases downward in the vertical pipe 1 may be provided in the middle of the vertical pipe 1.

  Next, a configuration for preventing a negative pressure loss in the suction force generator of FIG. 2 will be described with reference to FIGS. FIG. 6 is a view for explaining a negative pressure loss generated in the suction force generator of FIG. FIG. 7 is a view schematically showing a configuration in which a negative pressure loss prevention device for preventing negative pressure loss is provided in the suction force generation device of FIG.

  As shown in FIG. 6, the negative pressure due to the siphon acts greatly at the position of the horizontal pipe 2 at the top, but it is separately provided below the horizontal pipe 2 via a relatively short connecting pipe 2b on the tip 2a side of the horizontal pipe 2. When the horizontal pipe 2c is arranged and the water level surface H3 to be sucked is in the vicinity of the position of the lower horizontal pipe 2c and lower than the position of the horizontal pipe 2, a loss of negative pressure occurs according to the height difference Δh. In other words, since a portion corresponding to the height difference Δh has to be pumped, a loss of negative pressure occurs.

  In order to prevent this negative pressure loss, it is preferable to provide a negative pressure loss prevention device 35 in the suction force generation device of FIG. 2 as shown in FIG. The negative pressure loss prevention device 35 has a sealed container 36 in which a pumping pump 37 and a drain pipe 38 are installed. An inlet pipe 34 connected to the water of the water level surface H3 to be drained is connected to the inlet of the sealed container 36, and the outlet The outlet pipe 39 connected to the horizontal pipe 2 and the connecting pipe 2b is connected to the section. Water to be drained is supplied into the sealed container 36 from the inlet pipe 34 in the direction i, and this water is drained in the direction j through the drain pipe 38 by the pumping pump 37, and the siphon function maintaining device from the tip 38a of the drain pipe 38. 3 tank 4.

  Since the water level in the sealed container 36 is lowered by drainage by the pump 37, the outlet pipe 39 connected to the horizontal pipe 2 is filled with gas, and a negative pressure loss due to the height difference Δh of the drainage path occurs. Absent.

  As shown in FIG. 7, by providing the negative pressure loss prevention device 35 in the suction force generation device of FIG. 2, the water in front of the drainage path with the height difference Δh is pumped up and drained, so that the inside of the drainage path with the height difference Δh Can be filled with gas to prevent the loss of negative pressure. In addition, by sending the water pumped up to prevent negative pressure loss to the siphon function maintaining device 3, the amount of water supplied into the vertical pipe 1 is increased, the air mixing rate is lowered, and the flow velocity flowing down is increased. Thus, the siphon functions easily in the vertical pipe 1.

  In the negative pressure loss prevention device 35 of FIG. 7, when drainage by the pumping pump 37 is performed to an amount equal to or more than the amount of water flowing into the sealed container 36, the gas and liquid are separated in the sealed container 36. Become. At this time, since the inside of the drainage path having a height difference is filled with gas, no negative pressure loss occurs, and the negative pressure loss prevention device 35 is fully functioning. On the other hand, when the amount of water flowing into the sealed container 36 is larger than the amount of drainage by the pumping pump 37, the inside of the sealed container 36 is saturated with water. At this time, water remains in the drainage channel (connecting pipe 2b) having a height difference, and the water level in the drainage channel varies depending on the amount of water flowing into the sealed container 36, but a negative pressure loss corresponding to the water level in the drainage channel. Therefore, the negative pressure loss prevention device 35 is partially functioning. As described above, in order to fully exhibit the negative pressure loss function in the negative pressure loss prevention device 35, the drainage capacity of the pumping pump 37 is always equal to or more than the amount of water flowing into the closed vessel 36, and the inside of the closed vessel 36 is increased. In this case, it is preferable to separate the gas and the liquid, but the negative pressure loss function can be partially exhibited even if the gas and the liquid are not separated.

<Second Embodiment>
FIG. 8 is a diagram schematically showing the configuration of a vacuum consolidation ground improvement system that performs the vacuum consolidation ground improvement method according to the second embodiment.

  The vacuum consolidation ground improvement system 50 in FIG. 8 includes a suction force generator having a vertical water conduit 11 and a horizontal water conduit 12 and a vacuum decompressor 30. The horizontal water pipe 12 is connected to the vertical water pipe 11 at the upper end of the vertical water pipe 11, and the vertical drain member 31 placed in the soft ground G for improving the vacuum consolidated ground is provided with an air-impermeable portion 32. It is connected via the connection part 33. In addition, the vertical water pipe 11 and the horizontal water pipe 12 may be the same structure as the vertical pipe 1 and the horizontal pipe 2 of the attraction | suction force generator of FIG. 1, FIG.

  Further, the vacuum consolidation ground improvement system 50 of FIG. 8 includes the siphon function maintaining device 3 similar to that of FIG. 2, and the water in the tank 4 of the siphon function maintaining device 3 opens the valve 6 and horizontally through the water supply pipe 5. The water is supplied into the water pipe 12.

  As shown in FIG. 8, the vacuum decompression device 30 may be configured in substantially the same manner as in FIG. 2, and the sealed chamber 21 is installed in the ground. The sealed chamber 21 houses the vertical water pipe 11, the pumping pump 22, and the drain pipe 23, and the vacuum pressure reducing device 30 functions as a pressure reducing source by reducing the pressure inside the vacuum pump 25.

  The vertical drain material 31 is placed in the soft ground G to suck pore water in the soft ground G, and the air-impermeable portion 32 connected to the upper end of the vertical drain material 31 is located on the groundwater level surface H3. . Note that a plurality of vertical drain members 31 are placed in the soft ground G as necessary, and the configurations disclosed in Patent Documents 2 to 4, for example, together with the air-impermeable portion 32 and the connection portion 33. it can.

  The process of the vacuum consolidation ground improvement method by the vacuum consolidation ground improvement system 50 of FIG. 8 will be described.

  (1) The valve 12a of the horizontal water pipe 12 and the valve 11a of the vertical water pipe 11 are closed. At this time, it is preferable to cure each part of the horizontal water pipe 12 and the vertical water pipe 11 exposed to sunlight so as not to be affected by the heat of sunlight. For example, as shown in FIGS. It is preferable to provide a temperature rise prevention part.

  (2) After the vertical water pipe 11 and the horizontal water pipe 12 are filled with water, the valve 11a of the vertical water pipe 11 and the valve 6 of the siphon function maintaining device 3 are opened, and there is flowing water by the siphon function. To. At this time, it is preferable to dissolve a non-volatile solute such as sodium chloride in running water.

  (3) Water flowing into the sealed chamber 21 is drained by the pumping pump 22 and supplied to the tank 4 of the siphon function maintaining device 3.

  (4) The pressure in the sealed chamber 21 is gradually reduced by the vacuum pump 25, and when the pressure decreases to the target value, the valve 12a of the horizontal water pipe 12 is opened, and the ground water level surface H3 and the water level surface in the sealed chamber 21 are opened. The suction force generated by the siphon function caused by the water level difference ΔH (= H3−H1) with H1 is combined with the suction force of the vacuum pump 25, and the pore water in the soft ground G is sucked in the direction m through the vertical drain material 31. To do.

  (5) The siphon function maintaining device 3 and the valves 6 and 12a of the horizontal water pipe 12 are adjusted according to the amount of air and water flowing in from the vertical drain material 31 and the joints of the pipes, and the siphon is not interrupted. Like that. The amount of water supplied to the tank 4 of the siphon function maintaining device 3 through the drain pipe 23 is adjusted by adjusting the opening / closing of the valve 24a and appropriately draining the water through the external drain pipe 24 to the outside.

  As described above, ground compaction can be promoted by sucking the pore water in the soft ground G. At this time, suction by decompressing the inside of the sealed chamber 21 by the vacuum pump 25 of the vacuum decompression device 30 is performed. In addition to the force, suction force is generated by the siphon function due to the difference in water level ΔH between the groundwater level surface H3 and the water level surface H1 in the sealed chamber 21, and the suction water in the soft ground G is sucked by these suction forces. Thus, the soft ground G is consolidated, so that this vacuum consolidation can be performed with a larger suction force than the suction force caused by the water level difference ΔH, compared to the case where the suction is performed by the vacuum pump 25 alone.

  When using a siphon as a suction force, it becomes a problem that the siphon is easily interrupted due to air mixing into the water. In the vacuum consolidation ground improvement method using siphon together, the siphon function is easy when the amount of air mixing is large. On the other hand, according to the present embodiment, the amount of air mixed in the vertical water pipe 11 is reduced by supplying water to the horizontal water pipe 12 by the siphon function maintaining device 3 and the inside of the vertical water pipe 11 is reduced. The siphon function can be maintained by increasing the flow velocity. Thereby, a suction force can be efficiently applied to the soft ground.

  According to the conventional vacuum consolidation ground improvement method, when the suction force is insufficient with only the vacuum pump, loading with embankment is used together, but with the suction force by siphon function as in this embodiment, By maintaining the siphon function and applying suction force to the soft ground efficiently, loading due to embankment can be reduced or omitted, so the use of materials and equipment can be saved and the work period can be shortened. In addition, the suction force can be increased and the suction force can be efficiently applied as compared with the conventional construction method. Therefore, the ground improvement period required for the soft ground to reach a predetermined strength can be shortened.

  The pumping pump 22 is preferably a high head type with a head difference of 10 m or more, the sealed chamber 21 is installed deep in the ground, and the water level surface H1 in the sealed chamber 21 with respect to the ground water level surface H3 is secured in order to secure the water level difference ΔH. Even if it is made lower, the stored water in the sealed chamber 21 can be drained.

  In addition, as described above, the siphon is easier to function if the flow speed is increased by using a thin vertical water pipe. In order to satisfy the condition that the siphon function can be maintained with respect to water mixed with air while ensuring a sufficient amount of drainage, a plurality of vertical water pipes 41, 42, and 43 having different inner diameters are sealed as shown in FIG. 21 and connected to the horizontal water pipe 12 via the valves 41a, 42a and 43a, so that a preferred vertical water pipe can be selected quickly by opening and closing the valves 41a to 43a according to the amount of inflow water. May be. As a result, the siphon function can be maintained while ensuring a sufficient amount of drainage even with water mixed with air.

  EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited to a present Example.

Outline of experiment An experiment was conducted to verify the effect of water supply to the horizontal water pipe by the siphon function maintenance device on the sustainability of the siphon function. The experimental apparatus is shown in FIG.

The experiment was performed by the following procedure using the experimental apparatus of FIG.
Step 1: Water is injected from the water injection pipe, and the horizontal water pipe and the vertical water pipe are saturated with water. When the pipe is full, close the irrigation valve.
Step 2: Open the valve of the siphon function maintenance device and the valve of the vertical water pipe, let the siphon work, and gradually lower the pressure in the sealed chamber.
Step 3: With the negative pressure in the sealed chamber maintained at -50 kPa, the horizontal water pipe valve is opened.
Step 4: While measuring the amount of water supplied from the siphon function maintaining device, the valve of the siphon function maintaining device is gradually closed to measure the amount of water supplied when the siphon is turned off.

Experimental results When the siphon functions in the vertical water pipe, the suction force due to the water head difference is exerted, and therefore, a higher negative pressure acts on the horizontal water pipe than in the sealed chamber. It has been found that when a negative pressure of −90 kPa or more acts in the horizontal water pipe due to the siphon function, the dissolved air is vaporized and the volume of the air increases, thereby making the siphon difficult to function.

Furthermore, under the condition that the inner diameter of the vertical water pipe is 3 cm, when the water supply flow rate from the siphon function maintaining device is 15 L (liter) / min or more, a bubble mixed flow is formed in the vertical water pipe and the siphon function is maintained. We were able to. On the other hand, when the supply flow rate is reduced to 15 L / min or less, the flow rate of the water flowing down in the vertical water pipe becomes slow, so that the bubbles are not easily discharged by the water flow. As a result, the bubble mixed flow disappeared, and the water and air flows separated, and the siphon function disappeared. This is because, as described above, in the vertical water pipe, the condition that the flow velocity ν _{w of} the water flowing down the vertical water pipe is higher than the bubble rising speed ν _a is satisfied. This is because a flow cannot be formed. At this time, the negative pressure acting on the horizontal water pipe is the same as the vacuum pump pressure because no suction force is applied by the siphon.

  In addition, the limit supply amount of water in which the siphon function can be established in this experiment using a vertical water pipe with an inner diameter of 3 cm is converted into a condition using a pipe with an inner diameter of 5 cm so that the flow rate of water flowing down the pipe is the same. If it converts into the conditions using 42 L / min and the pipe | tube with an internal diameter of 10 cm, it will be 167 L / min.

  In this experiment, the amount of water supply was maintained at 20 L / min, and the siphon functioned by supplying sufficient supply water amount, and the condition where the siphon function did not function because the supply water amount was as low as 10 L / min. FIG. 11 shows the result of measuring the negative pressure acting on the. From the measurement result of FIG. 11, when the amount of supplied water satisfies the condition of 15 L / min or more, it can be confirmed that a bubble mixed flow is formed in the vertical water pipe and a sufficient negative pressure can be applied to the horizontal water pipe. It was. Moreover, when the amount of supplied water did not satisfy the condition of 15 L / min or more, the siphon did not function, and only the negative pressure by the vacuum pump acted.

  In addition, the amount of dissolved oxygen in water (deaerated water) supplied from the sealed chamber to the siphon function maintenance device was measured by a pump. The tap water left for 1 day at room temperature was compared as normal water. Table 1 shows a comparison result of the amount of oxygen present.

  The amount of dissolved oxygen in normal water is 9.01 mg / L under the conditions of theoretically 19 ° C, normal pressure, and oxygen concentration of 20.9%, so the measurement result of normal water shows a value close to the theoretical value. It was. On the other hand, the water (deaerated water) supplied from the sealed chamber to the siphon function maintaining device by the pump is about 60% of the dissolved oxygen content of normal water. Therefore, it was confirmed that the water supplied to the siphon function maintaining device was deaerated and the amount of dissolved oxygen was reduced, and deaerated water supplied from the sealed chamber was preferable.

  According to the above experiment, in order to ensure that the siphon suction force acts even under conditions where gas such as dissolved oxygen is vaporized or there is gas flowing in from an airtight leaking part such as a horizontal water pipe, It was verified that supplying water from the function maintenance device is important for forming a gas-liquid two-phase flow in a vertical water pipe. It was also confirmed that the water supplied from the siphon function maintaining device is preferably deaerated water.

  As described above, the modes for carrying out the present invention have been described. However, the present invention is not limited to these, and various modifications can be made within the scope of the technical idea of the present invention. For example, in FIG. 8, the water supply portion (tank 4) of the siphon function maintaining device 3 may use a concave ground formed by excavation or ground subsidence instead of a tank manufactured in a factory or the like. Moreover, it is needless to say that the degassed water production apparatus 26 of FIG. 2 and the negative pressure loss prevention apparatus 35 of FIG. 7 may be provided in the vacuum consolidation ground improvement system 50 of FIG. 8 as necessary.

  1, 2, and 8, the position of the water supply pipe 5 of the siphon function maintaining device 3 in the horizontal pipe 2 and the horizontal water pipe 12 is an arbitrary position of the horizontal pipe 2 and the horizontal water pipe 12 (however, In FIG. 8, it may be an arbitrary position on the downstream side of the valve 12a.

  In addition, the suction force generator according to the present invention is applied to the vacuum consolidation ground improvement system, but is not limited thereto, and may be applied as appropriate to other devices, systems, and other construction methods, and similar effects can be obtained. . Further, the vertical pipe (vertical water pipe) and the horizontal pipe (horizontal water pipe) may be other than the cylindrical pipe, for example, a rectangular tube.

  1, 2 and 8, the first pipe is arranged as a vertical pipe (vertical water pipe) and the second pipe as a horizontal pipe (horizontal water pipe). The invention is not limited to this, and any arrangement may be used as long as the suction force acts by the siphon function from the tip side of the second tube toward the lower end side of the first tube due to the difference in water level. For example, the first tube and the second tube may be inclined.

  According to the suction force generation device and the suction force generation method of the present invention, the suction force based on the siphon principle can be generated stably and continuously even when gas is contained in water. Siphon's natural energy can be used as much as possible, and costs such as electric power can be reduced.

  According to the vacuum consolidation ground improvement method according to the present invention, it is possible to reduce or omit loading by embankment by using the suction force by the siphon function, and it is possible to reduce the use materials and equipment and shorten the work period. The ground improvement period required for the soft ground to reach a predetermined strength can be shortened.

1 Vertical pipe (first pipe)
2 Horizontal pipe (second pipe)
3 Siphon Function Maintenance Device 21 Sealed Chamber 22 Pumping Pump 25 Vacuum Pump 26 Deaerated Water Production Device 35 Negative Pressure Loss Prevention Device 30 Vacuum Decompression Device 31 Vertical Drain Material 11 Vertical Water Pipe 12 Horizontal Water Pipe 50 Vacuum Consolidation Ground Improvement System G Soft Ground ΔH Water level difference

Claims (8)

A first pipe extending from the upper part toward the lower part; a second pipe connected to the first pipe at the upper part; and a lower end side of the first pipe; A suction force generating device in which a suction force acts by a siphon function from the tip of the second tube toward the lower end of the first tube due to a difference in water level with the tip side;
Suction comprising a siphon function maintaining device that maintains a siphon function by supplying water into a drainage path formed from a tip side of the second pipe toward a lower end side of the first pipe. Force generator.   The suction force generator according to claim 1, wherein the water supplied into the drainage path is deaerated water with a reduced amount of dissolved air so that the siphon function is hardly interrupted.   In order to prevent the loss of negative pressure due to the difference in height under the condition that the level surface of the water to be sucked and drained is lower than the uppermost part of the second pipe, water flows into the drainage path in the second pipe. The suction force generation device according to claim 1, further comprising a negative pressure loss prevention device that drains before and prevents the loss of the negative pressure by filling the drainage passage having a height difference with gas.   4. The siphon function is made difficult to be interrupted by reducing the amount of dissolved air by dissolving a soluble substance in water supplied into the drainage path and increasing the boiling point of water. The suction power generator according to claim 1.   By providing a temperature rise prevention part on at least a part of the outer surface of the first pipe and / or the second pipe, the vaporization associated with the negative pressure action is suppressed by keeping the temperature and water temperature in the pipe low. The suction force generator according to claim 1, wherein the siphon function is less likely to be interrupted.   The attraction | suction force generator of any one of Claim 1 thru | or 5 which uses the power device by a vacuum pump together. Due to the difference in water level between the lower end side of the first pipe extending from the upper part to the lower part and the front end side of the second pipe connected to the first pipe at the upper part, the tip of the second pipe A suction force generation method for applying a suction force by a siphon function toward a lower end of the first pipe,
A suction force generation method characterized in that a siphon function is maintained by supplying water into a drainage path formed from a tip side of the second pipe toward a lower end side of the first pipe. .   A ground consolidation improvement by vacuum consolidation in soft ground using the suction power generation device according to any one of claims 1 to 6 or the suction power generation method according to claim 7. Construction method.

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