JP5505964B2 - Siphon suction force generator, suction force generation method and vacuum consolidation ground improvement method - Google Patents

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. According to this conventional suction device, a suction force that promotes compaction cannot be applied beyond the capacity of the vacuum pump. 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.

  Also, when using the suction force according to the siphon principle, if the position of the top of the installed drainage channel is higher than the level of the water that you want to suck and drain, the difference in height must be pumped. There is a need to solve the problem of loss.

  An object of the present invention is to provide a suction force generation device and a suction force generation method capable of efficiently generating a suction force according to the principle of siphon without separation of water and gas flows. In addition, even when there is a height difference between the top of the drainage channel and the water level of the suction / drainage water, a suction force generator and suction device that can efficiently generate suction force while suppressing loss of suction force The purpose is to provide a force generation method.

  Furthermore, an object of the present invention is to provide a vacuum consolidation ground improvement method capable of promoting vacuum consolidation in ground improvement and reducing or omitting loading due to embankment and shortening 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 A suction force generating device in which a suction force acts by a siphon function from the second tube toward the lower end of the first tube due to a water level difference between the lower end side of the tube and the second tube side. A siphon function maintaining device for maintaining a siphon function by supplying water into a drainage path formed from the second pipe toward the lower end side of the first pipe, and the supplied water And a reverse flow suppressing device that suppresses a reverse flow that flows toward the opposite side of the upper portion of the first pipe.

  According to this suction power generation device, even when water with a high air mixing rate is sucked and drained by the second pipe, the water is supplied into the drainage route by the siphon function maintaining device, so that The supplied water effectively flows toward the first pipe by the backflow suppressing device, so that the air mixing rate in the first pipe can be reduced, and the flow rate of the water flowing down in the first pipe is increased. Can be increased. For this reason, the gas-liquid two-phase flow is formed without separating the water and gas flows in the first pipe, and the siphon function can be maintained. Thus, since the suction force according to the principle of siphon can be generated continuously, the suction force by the siphon can be efficiently generated and used. 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, before the water flows into the drainage path in the second pipe under the condition that the level of the water to be sucked and drained is lower than the uppermost part of the second pipe and has a height difference. The drainage channel with the difference in elevation is filled with gas in a negative pressure state by draining through the drainage pipe from the inside of the sealed container arranged in the above and lowering the water level before flowing into the drainage channel in the sealed container. It is preferable to provide a suction force loss elimination device that eliminates the loss of suction force due to the difference in height. When the water level surface of the suction target is lower than the uppermost position of the second pipe, the suction force is lost due to the height difference, but as a countermeasure, a sealed container placed in front of the drainage path with the height difference By pumping up the water inside and draining it, it is possible to prevent the loss of suction force by filling the drainage path with a difference in height with a gas whose density is significantly smaller than the liquid in a negative pressure state, The suction force by the siphon function can be applied by the water level difference between the lower end side of the first pipe and the second pipe side. The uppermost portion of the second pipe is the horizontal height position portion when the second pipe is horizontally arranged, and the height difference due to the second pipe being inclined or stepped. Is the highest position part.

  In addition, the above-mentioned drainage path with a height difference can be comprised from a vertical path | route or an inclination path | route. Moreover, it is preferable that the pumped-up water is supplied to the above-mentioned water supply by sending it to the siphon function maintaining device through the drain pipe.

  In order to prevent inflow of air into the suction force loss elimination device, it is preferable to provide a check valve in the drain pipe. This prevents the atmospheric pressure from being transmitted because air does not flow into the suction force loss elimination device through the drainage pipe, and prevents the suction force loss elimination device from deteriorating due to atmospheric pressure inside the suction force loss elimination device. it can.

Moreover, it is preferable to provide the water saturation path | route comprised from the level | step difference or inclination pipe | tube which becomes high in the downstream so that water may be saturated in the said drainage path | route downstream from the said water supply position. Since the water saturation path in which water is saturated has a buffering effect, even when the suction force increases rapidly, the inflow of gas accompanying the rapid expansion of gas in the drainage path filled with gas can be suppressed. it can. Thereby, a siphon can be functioned more stably.

  Moreover, it is preferable that the said backflow suppression apparatus has at least any one of a flow regulating valve, a level | step difference path | route, an inclination path | route, and a constriction path | route. Thereby, the water supplied in the drainage channel can be effectively flowed toward the first pipe.

  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.

  The suction force generation method for achieving the above object includes a water level between a lower end side of a first pipe extending from the upper part toward the lower part and a second pipe side connected to the first pipe at the upper part. A suction force generation method in which a suction force is applied by a siphon function from the second tube toward a lower end of the first tube due to a difference, from the second tube to a lower end side of the first tube. The siphon function is maintained by supplying water into the drainage path formed toward the drain, and the supplied water is prevented from flowing back toward the opposite side of the upper part of the first pipe. It is characterized by that.

  According to this suction force generation method, even when water with a high air mixing rate is sucked and drained by the second pipe, by supplying water into the drainage path, the water supplied into the drainage path is further reduced. By suppressing the reverse flow, the air flow rate in the first pipe can be reduced by effectively flowing toward the first pipe, and the flow rate of the water flowing down in the first pipe is increased. Can be made. For this reason, the gas-liquid two-phase flow is formed without separating the water and gas flows in the first pipe, and the siphon function can be maintained. Thus, since the suction force according to the principle of siphon can be generated continuously, the suction force by the siphon can be efficiently generated and used. In addition, you may make it reuse the water drained from the lower end of a 1st pipe | tube for the water supply in a drainage channel | path.

In the above suction force generation method, before the water flows into the drainage path in the second pipe under the condition that the level of the water to be sucked and drained is lower than the uppermost part of the second pipe and there is a difference in elevation. By draining from the inside of the sealed container disposed in the water and lowering the water level before flowing into the drainage path in the sealed container, the inside of the drainage path having a difference in height is filled with a gas in a negative pressure state. It is preferable to eliminate the loss of suction force due to the height difference. When the water level surface of the suction target is lower than the uppermost position of the second pipe, the suction force is lost due to the height difference, but as a countermeasure, a sealed container placed in front of the drainage path with the height difference By pumping up the water inside and draining it, it is possible to prevent the loss of suction force by filling the drainage path with a difference in height with a gas whose density is significantly smaller than the liquid in a negative pressure state, The suction force by the siphon function can be applied by the water level difference between the lower end side of the first pipe and the second pipe side. The pumped water is preferably reused for water supply into the drainage channel. In addition, when the second pipe is horizontally arranged, the uppermost part of the second pipe is a horizontal height position portion thereof, and the second pipe has a height difference due to an inclination or a step. Is the highest position part.

  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.

  Another vacuum consolidation ground improvement method for achieving the above object is that, in the above-mentioned conditions, the water level of the water to be sucked and drained is lower than the uppermost part of the second pipe, and water is supplied to the second pipe. Using a suction force generator or suction force generation method that drains through a drain pipe before flowing into the drainage path and fills the drainage path with a height difference with gas to prevent loss of the suction force. The at least lower end side of the first pipe is disposed in a sealed chamber that can be depressurized by a vacuum pump, and a negative pressure resulting from depressurization of the sealed chamber is added to the suction force by the siphon function, and the ground due to vacuum consolidation in a soft ground When performing the improvement, the sealed chamber is installed on the ground surface.

  According to this vacuum consolidation ground improvement method, the negative pressure generated by reducing the pressure in the sealed chamber where at least the lower end side of the first pipe is decompressed is added to the suction force by the siphon function to improve the ground by vacuum consolidation in the soft ground. Thus, it is possible to promote vacuum consolidation in ground improvement and to reduce or omit loading due to embankment and shorten the ground improvement period. Further, under the condition that the level of the water to be sucked and drained in the soft ground is lower than the uppermost part of the second pipe, the water is drained in the second pipe by the above-described suction force generator or suction force generation method. Since it drains through the drainage pipe before flowing into the passage and the inside of the drainage passage with a difference in height is filled with a negative pressure gas whose density is significantly lower than the gas, the loss of suction force can be suppressed, so the sealed chamber Even if it is installed on the ground surface, it can be used for ground improvement by vacuum compaction by generating suction force by siphon function. Moreover, since it is not necessary to install a sealed chamber in the underground part, the ground improvement cost can be reduced.

  According to the suction force generation device and the suction force generation method of the present invention, it is possible to efficiently generate the suction force according to the siphon principle without separating the water and gas flows. Further, even when there is a difference in level between the uppermost portion of the drainage channel and the water level of the suction / drainage water, the suction force can be efficiently generated while suppressing the loss of the suction force.

  According to the vacuum consolidation ground improvement method of the present invention, vacuum consolidation in ground improvement can be promoted to reduce or omit loading by embankment and shorten the ground improvement period.

It is a figure showing roughly the composition of the attraction power generator by a 1st embodiment. It is a figure for demonstrating the attraction force loss generate | occur | produced when there is no attraction force loss elimination apparatus in the attraction force generator of FIG. 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). It is a figure which shows roughly the structure of the attraction | suction force generator which provided the level | step difference path | route in the horizontal pipe | tube as a backflow suppression apparatus of FIG. It is a figure which shows roughly the structure of the attraction | suction force generator which provided the stenosis path | route in the horizontal pipe as a backflow suppression apparatus of FIG. FIG. 2 is a partial view (a) schematically showing a state in which the siphon is functioning normally in the suction force generator of FIG. 1 and a partial view (b) schematically showing a state in which the siphon is interrupted. It is a figure which shows the example which provided the water saturation path | route in the horizontal pipe as a countermeasure when the pressure in a drainage path | route fluctuates in the suction power 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 fragmentary figure which shows another modification of the vacuum consolidation ground improvement system by 2nd Embodiment. It is a figure which shows schematically another structural example of the vacuum consolidation ground improvement system by 2nd Embodiment. It is a figure which shows schematically the further another structural example 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. It is a graph which shows the time fluctuation | variation of each working pressure measured in the case (the height difference part is saturated with water) which does not operate the attraction | suction force loss elimination apparatus in the preliminary experiment of a present Example. It is a graph which shows the time fluctuation of each working pressure measured in the experiment of a present Example in the case where the backflow rate of the water supplied from a water supply apparatus is about 3%, and the water supply amount was 30 L / min. .

  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. The siphon function maintaining device 3 that maintains the siphon function by supplying water to the horizontal pipe 2 and the backflow suppressing device 8 that suppresses the backflow of water supplied from the siphon function maintaining device 3 are provided. A drainage path is formed through 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 in FIG. 1 is disposed between the tank 4 which is disposed at the top of the horizontal pipe 2 and stores water, and between the bottom of the tank 4 and the horizontal pipe 2, and is connected to the horizontal pipe 2 at a water supply position 5a. A water supply pipe 5 to be connected and a valve 6 provided in the middle of the water supply pipe 5 are provided, and water is supplied by flowing the water in the tank 4 in the direction b through the water supply pipe 5 by opening the valve 6. Supply from the position 5 a into the drainage path of the horizontal pipe 2.

  1 is between the water supply position 5a of the siphon function maintaining apparatus 3 and the tip 2a of the horizontal pipe 2, that is, upstream of the water supply position 5a (on the opposite side to the water flow direction c). ) Arranged to suppress the reverse flow of water supplied from the tank 4 (flow in the direction opposite to the flow direction c of water in the horizontal pipe 2).

  The flow rate adjustment valve of the backflow control device 8 is preferably one that can adjust the flow rate by adjusting the opening amount of the valve, and the flow rate of water flowing in the direction opposite to the water flow direction c in the horizontal pipe 2 is adjusted to a predetermined amount. Can be limited.

  FIG. 2 is a view for explaining the suction force loss that occurs when the suction force loss eliminating device is not provided in the suction force generation device of FIG. As shown in FIG. 2, the negative pressure by the siphon works greatly at the position of the horizontal pipe 2 at the top, but another horizontal pipe is provided below the horizontal pipe 2 via the connecting pipe 2b on the tip 2a side of the horizontal pipe 2. 2c, and when the water level surface H3 to be sucked is near the position of the lower horizontal pipe 2c and lower than the position of the horizontal pipe 2, the negative pressure according to the height difference Δh between the horizontal pipe 2 and the water level surface H3 Loss, that is, loss of suction force occurs. In other words, a portion corresponding to the height difference Δh must be pumped, resulting in a loss of suction power.

  In order to eliminate this suction force loss, the suction force generator of FIG. 1 drains water in the direction j through the drainage pipe 38 before water flows into the drainage path in the horizontal pipe 2 through the connection pipe 2b, and has a difference in height. A suction force loss elimination device 35 that eliminates the loss of suction force by filling the drainage path in the pipe 2b with gas is provided.

  As shown in FIG. 1, the suction loss eliminator 35 has a sealed container 36 in which a pumping pump 37 and a drain pipe 38 are installed, and the sealed water in which the water at the water level surface H3 to be drained exists at the inlet of the sealed container 36. The inlet pipe 34 connected to the space is connected, and the outlet pipe 39 connected to the outlet portion via the distal end 2a of the horizontal pipe 2 and the connecting pipe 2b is connected. Water to be drained is supplied from the inlet pipe 34 into the sealed container 36, and this water is drained in the direction j through the drain pipe 38 by the pumping pump 37, and from the tip 38 a of the drain pipe 38 to the tank 4 of the siphon function maintaining device 3. Supplied. In addition, although the connection pipe 2b connected with the front-end | tip 2a of the horizontal pipe 2 may be arrange | positioned in the perpendicular direction, you may arrange | position incline. Further, the inlet pipe 34 is connected to, for example, a vertical drain material 31 shown in FIG.

  Since the water level in the sealed container 36 is lowered by the drainage from the sealed container 36 by the pumping pump 37, compared to the liquid in the drainage path of the connecting pipe 2b connected to the outlet pipe 39 and the horizontal pipe 2 connected to the connecting pipe 2b. A gas having a remarkably low density flows and fills in the direction a toward the horizontal pipe 2 in a negative pressure state, so that loss of negative pressure (suction force) related to pumping of the height difference Δh of the drainage path can be suppressed. . As described above, the suction force generation device of FIG. 1 includes the suction force loss elimination device 35, and by pumping and draining water before the drainage path with the height difference Δh, the liquid is put into the drainage path with the height difference Δh. Compared to the above, the gas in a negative pressure state having a remarkably small density is filled, and the loss of suction force can be eliminated.

  Further, by providing a check valve 38 a in the middle of the drain pipe 38 connected to the sealed container 36 of the suction force loss canceling device 35, air flows into the sealed container 36 of the suction force loss canceling apparatus 35 through the drain pipe 38. It is preferable not to do so. Accordingly, it is possible to prevent atmospheric pressure from being transmitted into the sealed container 36 and the function of the suction force loss canceling apparatus 35 from being lowered due to the atmospheric pressure in the sealed container 36 of the suction power loss canceling apparatus 35.

  As shown in FIG. 1, when the lower end 1a of the vertical pipe 1 is in water, the tip of the horizontal pipe 2 is caused by a siphon function resulting from a water level difference ΔH between the drainage level surface H1 and the water level surface H2 in the horizontal pipe 2. A suction force is generated from the 2a side toward the lower end 1a side of the vertical pipe 1. At this time, even if there is a height difference Δh between the water level surface H3 to be sucked and the horizontal pipe 2, the suction force loss elimination device 35 can eliminate the loss of the suction force. With such a siphon function, water flows in the horizontal pipe 2 in the horizontal direction c and in the vertical pipe 1 in the vertical direction d. 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 H2 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.

  FIG. 3 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 generating device of FIG. 1 and a state where the gas-liquid two-phase flow of water and air cannot be realized. It is a schematic diagram (b) for demonstrating.

  In order for the suction force to act in accordance with the siphon principle under the condition that the gas is contained in the horizontal pipe 2, the water and the gas must be flowed together in the vertical pipe 1 without being separated. That is, as shown in FIG. 3A, even if air and water flow separately in the direction c in the horizontal pipe 2, the air is taken in as a large number of 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. 3B, if air and water flow separately in a horizontal pipe and 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.

  When draining by suction force according to the principle of siphon, since the inflow of air occurs from the vaporization of dissolved oxygen or the like and the airtight leak portion in the tube, the vertical tube 1 is maintained as described above in order to maintain the siphon function. The gas flow and the liquid flow must be prevented from being separated from each other, and a gas-liquid two-phase flow (bubble mixed flow) must be formed as shown in FIG. In order for the flow of water and air passing through the horizontal pipe 2 to become a gas-liquid two-phase flow in the vertical pipe 1 to facilitate the siphon function, the air mixing rate in the vertical pipe 1 is reduced and the vertical pipe is reduced. It is necessary to increase the flow rate of water flowing down 1.

  In the suction force generator of FIG. 1, by supplying water from the siphon function maintaining device 3 into the drainage path, the air mixing rate in the vertical pipe 1 can be reduced, and the flow rate of water flowing down the vertical pipe 1 is set. The effect to increase appears, and the siphon function can work stably. Further, even if there is a height difference Δh in the drainage path, the suction force loss canceling device 35 fills the drainage path with the height difference Δh with a gas in a negative pressure state having a significantly lower density than the liquid, thereby reducing the suction force. Loss can be prevented. Furthermore, by providing the backflow suppression device 8 upstream of the water supply position 5a from the siphon function maintaining device 3, the water supplied from the siphon function maintaining device 3 is less likely to flow in the direction opposite to the horizontal direction c. In order to effectively flow toward the pipe 2, it is possible to stably form a gas-liquid two-phase flow in the vertical pipe 1 while the inside of the drainage path having a height difference on the tip 2 a side of the horizontal pipe 2 is filled with gas. it can.

  As described above, according to the suction force generator of FIG. 1, when water is supplied from the siphon function maintaining device 3 into the horizontal pipe 2, the water supplied into the horizontal pipe 2 is also a backflow suppressing device. By effectively flowing toward the vertical pipe 1 by 8, the water sucked and flowing in the horizontal direction c has a low air mixing rate, and the flow velocity 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 can function. Furthermore, even if there is a height difference Δh in the drainage path, the suction force can be maintained by eliminating the loss of the suction force by the suction force loss eliminating device 35. In this way, the suction force according to the principle of the siphon can be continuously generated while maintaining the siphon function.

  Further, in the siphon function maintaining device 3 in FIG. 1, 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 in the horizontal pipe 2, thereby managing the water flow rate, that is, the flow velocity. Can flow smoothly with water.

  In addition, the suction force loss elimination device 35 in FIG. 1 can effectively use water by sending water pumped from the sealed container 36 to the tank 4 of the siphon function maintaining device 3 to prevent suction force loss. As a result, the amount of water supplied into the vertical pipe 1 is increased, the air mixing rate is reduced, and the flow velocity of the water flowing down is increased, so that the siphon can easily function in the vertical pipe 1.

  In the suction force loss elimination device 35 in FIG. 1, when drainage by the pumping pump 37 is performed to the same 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, the drainage path having a height difference is filled with a negative-pressure gas whose density is remarkably smaller than that of the liquid, so that a loss of negative pressure (suction force) does not occur, and the suction force loss elimination device 35 is completely It will be in a functioning state. 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 difference in height, and the water level in the drainage channel varies depending on the amount of water flowing into the sealed container 36, but the negative pressure loss corresponding to the water level in the drainage channel. Therefore, the suction force loss eliminating device 35 is partially functioning. As described above, in order to fully exhibit the suction force loss function in the suction force loss eliminating device 35, the drainage capacity of the pumping pump 37 is always equal to or more than the amount of water flowing into the sealed container 36, and the inside of the sealed container 36 is set. However, 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.

Next, the principle of the suction force generation device of the present embodiment, that is, the conditions for causing the siphon to function 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 ν _{w of} the water flowing down the vertical pipe is larger than the rising speed ν _a of the bubbles, the bubbles are entrained in the flow of water and the gas-liquid multiphase 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) Decreasing the aeration rate, reducing the maximum diameter of bubbles that can be formed, and suppressing the rising speed of bubbles (Equations (1) and (2)).
(2) Narrow the vertical pipe or increase the amount of water to be supplied to increase the water flow speed (formula (3)).

  The suction force generator of the present embodiment has a configuration using the above (1) and (2). In order to enhance the effect of (2) 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, two other examples relating to the backflow suppressing device 8 of the suction force generating device of FIG. 1 will be described with reference to FIGS. FIG. 4 is a diagram schematically showing a configuration of a suction force generating device in which a step path is provided in a horizontal pipe as the backflow suppressing device of FIG. FIG. 5 is a diagram schematically showing a configuration of a suction force generating device in which a narrowing path is provided in a horizontal pipe as the backflow suppressing device of FIG.

  In the example of FIG. 4, instead of the flow rate regulating valve of the backflow suppressing device 8 of FIG. 1, a step path 8 a having a step as a backflow suppressing device is provided with a water supply position 5 a of the siphon function maintaining device 3 and a tip 2 a of the horizontal pipe 2 Between the two. The horizontal pipe 2 is slightly higher on the tip 2a side and slightly lower on the water supply position 5a side via the step path 8a. In the step path 8a provided in the middle of the horizontal pipe 2, the water supplied from the siphon function maintaining device 3 becomes difficult to flow backward, and the backward flow can be suppressed. Thereby, the water supplied from the water supply position 5 a of the siphon function maintaining device 3 effectively flows toward the vertical pipe 1. Instead of the step path 8a, the step path 8a may be configured as an inclined path, and similarly, the backflow of water supplied from the siphon function maintaining device 3 can be suppressed.

  In the example of FIG. 5, instead of the flow rate adjustment valve of the backflow suppression device 8 of FIG. 1, the narrowed path 8 b that is narrowed by reducing the internal cross-sectional area as a backflow suppression device It is provided between the tip 2 a of the tube 2. In the constriction path 8b provided in the middle of the horizontal pipe 2, the water supplied from the siphon function maintaining device 3 becomes difficult to flow backward, and the backward flow can be suppressed. Thereby, the water supplied from the water supply position 5 a of the siphon function maintaining device 3 effectively flows toward the vertical pipe 1. In addition, although it is preferable to provide the constriction path | route 8b in the vertical direction upper part of the horizontal pipe 2 like FIG. 5, it is not limited to this, You may provide in the vertical direction middle or lower part.

  4 and 5, a flow rate regulating valve as shown in FIG. 1 may be further provided in the vicinity of the step path 8a and the constriction path 8b as a backflow suppressing device.

  Next, problems and countermeasures in the case where the pressure in the drainage path fluctuates in the suction force generators of FIGS. 1, 4 and 5 will be described with reference to FIGS. 6 and 7. FIG. 6 is a partial view (a) schematically showing a state in which the siphon is functioning normally in the suction force generator of FIG. 1 and a partial view (b) schematically showing a state in which the siphon is interrupted. FIG. 7 is a view showing an example in which a water saturation path is provided in a horizontal pipe as a countermeasure when the pressure in the drainage path fluctuates in the suction force generator of FIG.

  In the suction force generator of FIG. 1, as shown in FIG. 6 (a), when the drainage path with a difference in height such as the connecting pipe 2 b is filled with a negative pressure gas, the gas flows in the direction a. Then, water and air flow from the horizontal pipe 2 in the direction c, and a gas-liquid two-phase flow in the vertical pipe 1 flows in the vertical downward direction d so that the siphon functions normally.

  Here, if the pressure p fluctuates in the state where the drainage path constituted by the horizontal pipe 2, the connecting pipe 2b, and the outlet pipe 39 on the upstream side of the backflow suppression device 8 is filled with gas, the volume of the gas V changes according to Boyle's law (pV = constant).

  For example, when the suction force of the siphon increases instantaneously, the gas in the drainage path having a difference in height flows rapidly in the direction a and expands rapidly. As a result, as shown in FIG. 6B, a large amount of gas flows from the horizontal pipe 2 into the vertical pipe 1 that causes the siphon to function, and the unsaturated state in which water and air are separated in the vertical pipe 1 spreads to increase the siphon. Will be interrupted, making it easier to interrupt.

  As a measure for preventing the siphon function from being interrupted as described above, in the example of FIG. 7, the water saturation path 9 is provided in the horizontal pipe 2 on the downstream side of the water supply position 5a of the siphon function maintaining apparatus 3 in the suction force generator of FIG. It is provided. The water saturation path 9 is composed of a step where the horizontal pipe 2 is slightly higher in the upper part on the downstream side of the water supply position 5a. That is, the horizontal pipe 2 extends to the downstream side of the water supply position 5a substantially horizontally in the water flow direction c while being slightly lower in the step path 8a than the tip 2a side, and is slightly higher in the water saturation path 9. After that, it is connected to the upper part of the vertical pipe 1.

  As shown in FIG. 7, while the siphon function maintaining device 3 supplies water from the water supply position 5a into the drainage path, the gas flowing from the direction a in the drainage path because the suction force has increased rapidly as described above. Flows rapidly in the direction c from the step path 8a. As a result, the water level H is lowered in the drainage path downstream of the step path 8a, but the water hits the step of the water saturation path 9 and becomes saturated at this step, so that air enters the water. It is taken in and mixed and flows vertically upward c ′. For this reason, the siphon function is not interrupted and is not interrupted by the water mixed with air flowing from the upper part of the vertical pipe 1 in the vertical pipe 1 while maintaining the gas-liquid two-phase flow.

  As described above, the water saturation path 9 has a buffering effect on the flow of water and air, and when the suction force (negative pressure) increases rapidly in the horizontal pipe 2, the gas filled in the drainage path suddenly increases. It is possible to suppress the inflow of gas into the vertical pipe 1 due to the expansion. For this reason, a siphon can be functioned more stably. The water saturation path 9 in FIG. 7 can obtain the same effect when applied to the suction force generation apparatus in FIGS.

  When using a siphon as a suction force, there is a problem that the siphon is easily interrupted due to air mixing into water, and the siphon function easily deteriorates when the amount of air mixing is large in the vacuum consolidation method using siphon. On the other hand, according to the suction force generator of this embodiment, a gas-liquid two-phase flow is formed in the vertical pipe 1 to exert the siphon function, and the uppermost part of the drainage path and the suction / drainage Even when there is a difference in level between the desired water level and the water level, suction and drainage can be performed effectively without losing the suction power of the siphon.

<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 100 in FIG. 8 includes a suction force generator having a vertical water conduit 11 and a horizontal water conduit 12 and configured in substantially the same manner as FIG. 1, 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. 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.

  In order to improve the vacuum consolidated ground, the vertical drain material 31 is placed in the soft ground G from the ground surface S so as to suck the pore water in the soft ground G, and is impervious connected to the upper end of the vertical drain material 31. The lower end of the air portion 32 is at a position deeper than 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 suction force generating device of the vacuum consolidation ground improvement system 100 of FIG. 8 includes the siphon function maintaining device 3 similar to FIG. 1, and the water in the tank 4 of the siphon function maintaining device 3 opens the valve 6 so that the water supply pipe 5 is supplied into the horizontal water pipe 12 at a water supply position 5a.

  Further, the suction force generation device of FIG. 8 includes a backflow suppression device 8 and a suction force loss elimination device 35 similar to those of FIG. The inlet pipe 34 of the sealed container 36 of the suction force loss eliminating device 35 is connected to the vertical drain material 31 through the impermeable portion 32 and the connecting portion 33. The sealed container 36 is installed on the ground surface S, and is at a position higher than the groundwater level surface H3 in the ground G to be improved. The horizontal water pipe 12 is at a higher position than the closed container 36, but the outlet pipe 39 of the closed container 36 is connected to the horizontal water pipe 12 via a valve 12a and a connecting pipe 12b.

  As shown in FIG. 8, the vacuum decompression device 30 includes a sealed chamber 21 provided in the ground so that the vertical water pipe 11 extends and water from the vertical water pipe 11 is accumulated, and a vacuum pump that decompresses the inside of the sealed chamber 21. 25 and a pumping pump 22 for discharging the water accumulated in the sealed chamber 21 through the drain pipe 23 in the direction e. The drain pipe 23 extends to the tank 4 of the siphon function maintaining device 3, and drains water from the tip 23 a to the tank 4, thereby reusing the water accumulated in the sealed chamber 21.

  In the vacuum decompression device 30 of FIG. 8, the inside of the sealed chamber 21 is decompressed by the vacuum pump 25, so that the vacuum decompression device 30 functions as a decompression (negative pressure) generation source. For this reason, according to the vacuum consolidation ground improvement system 100 of FIG. 8, since the suction force by the vacuum pump 25 and the suction force resulting from the siphon function by the horizontal water pipe 12 and the vertical water pipe 11 can be generated. A large suction force exceeding the capacity 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.

  Further, even if there is a difference in level between the horizontal water pipe 12 and the groundwater level surface H3 in the ground G to be improved, the suction force loss elimination device 35 in FIG. The drainage passage through the connecting pipe 12b is filled with a negative-pressure gas whose density is remarkably smaller than that of the liquid, and by suppressing the energy loss related to pumping in the drainage passage having a height difference, The loss of the suction force due to the siphon caused by the water pipe 11 can be eliminated.

  The process of the vacuum consolidation ground improvement method by the vacuum consolidation ground improvement system 100 of FIG. 8 is demonstrated.

  (1) The sealed chamber 21 of the vacuum pressure reducing device 30 that generates a reduced pressure by the vacuum pump 25 is sealed. The vertical drain material 31 placed in the soft ground to be improved is connected to the inlet pipe 34 of the suction force loss eliminating device 35, and the outlet pipe 39 is connected to the horizontal drain pipe 12 via the connecting pipe 12b.

  (2) The valve 12a of the horizontal water pipe 12 and the valve 11a on the lower end 1a side of the vertical water pipe 11 are closed.

  (3) 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 to allow water to flow. 11 in a state where the siphon function is activated.

  (4) 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 through the drain pipe 23.

  (5) The pressure in the sealed chamber 21 is gradually reduced by the vacuum pump 25, and when the pressure is reduced to the target value, the valve 12a of the horizontal water pipe 12 is opened and the pumping pump 37 of the suction power loss eliminating device 35 is turned on. Operate. Thereby, the suction force by the vacuum pump 25 is added to the suction force by the siphon function caused by the water level difference ΔH (= H2−H1) between the uppermost water level surface H2 of the horizontal water pipe 12 and the water level surface H1 in the sealed chamber 21. In combination, the pore water in the soft ground G is sucked through the vertical drain material 31 in the direction m and flows into the sealed container 36 in the direction f through the inlet pipe 34.

  (6) Adjusting the opening and closing of the valve 6 of the siphon function maintaining device 3 and the flow rate regulating valve of the backflow control device 8 according to the amount of air and water flowing in from the vertical drain material 31 and the joint portion of each pipe, etc. Keep the siphon function so that there is no interruption. 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, a suction force is generated by the siphon function due to the water level difference ΔH between the water level surface H2 in the horizontal water pipe 12 and the water level surface H1 in the sealed chamber 21, and the soft ground G is generated by these suction forces. Since the soft ground G is consolidated by sucking the interstitial water in the inside, this vacuum consolidation is performed by a suction force larger than the suction force caused by the water level difference ΔH as compared with the case of suctioning only by the vacuum pump 25. It can be carried out.

  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 water supplied to the horizontal water pipe 12 by the siphon function maintaining device 3 and the water supplied into the horizontal water pipe 12 are vertically converted by the backflow suppressing device 8 according to the present embodiment. By effectively flowing toward the water flow pipe 11, the amount of mixed air in the vertical water flow pipe 11 can be reduced and the flow velocity flowing down in the vertical water flow pipe 11 can be increased to maintain the siphon function. Thereby, a suction force can be efficiently applied to the soft ground.

  Furthermore, even if there is a height difference between the horizontal water pipe 12 and the groundwater level surface H3 in the ground G to be improved, the suction power loss can be eliminated by the suction power loss elimination device 35. It can be applied to soft ground efficiently without reducing the force.

  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 horizontal water pipe 12 is secured to ensure 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 as shown in FIG. By connecting to the horizontal water pipe 12 through the valves 41a, 42a and 43a, the preferred vertical water pipe can be quickly selected by opening and closing the valves 41a to 43a according to the amount of inflow water. You may be able to do it. As a result, the siphon function can be maintained while ensuring a sufficient amount of drainage even with water mixed with air.

  In addition, the suction force generator of FIGS. 4, 5 and 7 may be applied to the vacuum consolidation ground improvement system 100 of FIG. 8, and the same effects as described above can be obtained. In this case, the step path 8a of the backflow suppressing device 8 of FIG. 4 may be composed of a plurality of vertical pipes 51, 52, 53 having different diameters. That is, the horizontal water pipe 12c which comprises the front-end | tip 2a side of the horizontal pipe 2 of FIG. 4 is arrange | positioned at the upper part of the horizontal water pipe 12, and several vertical pipe 51, between the horizontal water pipe 12 and the horizontal water pipe 12c, 52 and 53 are arranged via valves 51a, 52a and 53a. Depending on the amount of water supplied from the siphon function maintaining device 3 to the horizontal water pipe 12, the vertical pipes 51, 52, and 53 having a high backflow suppression effect may be quickly selected by opening and closing the valves 51a to 53a.

  Next, two examples of another configuration of the vacuum consolidation ground improvement system according to the second embodiment will be described with reference to FIGS. FIG. 11 is a diagram schematically showing another configuration example of the vacuum consolidation ground improvement system according to the second embodiment. FIG. 12 is a diagram schematically showing still another configuration example of the vacuum consolidation ground improvement system according to the second embodiment.

  The example of FIG. 11 has the same configuration as the vacuum consolidation ground improvement system 100 of FIG. 8, but the sealed chamber 21 of the vacuum decompression device 30 is installed on the ground surface S1 instead of in the ground. In addition, the airtight container 36 of the suction force loss elimination apparatus 35 is also installed on the ground surface S1.

  According to the vacuum consolidation ground improvement system of FIG. 11, even if there is a height difference between the horizontal water pipe 12 and the groundwater level surface H3 in the ground G to be improved, the horizontal water pipe is removed by the suction force loss eliminating device 35. Since the loss of the suction force in the twelve drainage paths is eliminated, the vacuum consolidation ground improvement method using the suction force by the siphon function can be implemented as in FIG. 8, and the sealed chamber 21 is placed on the ground surface S1. Can be installed. For this reason, the cost of installing the sealed chamber 21 of the vacuum decompression device 30 in the underground portion becomes unnecessary, and it can contribute to the cost reduction of the vacuum consolidation ground improvement.

  12 is basically the same configuration as the vacuum consolidation ground improvement system of FIG. 11, but a mountain-shaped obstacle J such as a dike or embankment is provided between the ground improvement target area and the vacuum decompression device 30. It is a structural example when it exists.

  As shown in FIG. 12, a suction loss eliminating device 35 is installed near the vertical drain material 31 placed in the soft ground G in the ground improvement target area, and the upper part of the mountain-shaped obstacle J such as an embankment or embankment. The horizontal water pipe 12 and the siphon function maintaining device 3 are installed, and the vacuum decompression device 30 is installed on the ground surface S opposite to the mountain-shaped obstacle J with respect to the ground improvement target area. The suction force loss eliminating device 35 and the horizontal water pipe 12 are connected by an inclined connecting pipe 12b.

  According to the vacuum consolidation ground improvement system of FIG. 12, the horizontal water pipe 12 and the connecting pipe 12 b are arranged so as to exceed the mountain-shaped obstacle J, so that the embankment is provided between the ground improvement target area and the vacuum decompression device 30. Even when mountain-shaped obstacles J such as banking and embankment exist, the vacuum consolidation ground improvement method using the suction force by the siphon function can be implemented. That is, since the horizontal water pipe 12 is arranged on the top of the mountain-shaped obstacle J, even if there is a height difference between the horizontal water pipe 12 and the groundwater level surface H3 in the ground G to be improved, FIG. Similarly, since the loss of the suction force in the drainage path of the horizontal water pipe 12 is eliminated by the suction force loss elimination device 35, the vacuum consolidation ground improvement method using the suction force by the siphon function can be implemented. Moreover, since the sealed chamber 21 can be installed on the ground surface S1, the cost of installing the sealed chamber 21 of the vacuum decompression device 30 in the underground portion is unnecessary, which can contribute to the cost reduction of the vacuum consolidation ground improvement.

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

Outline of experiment An experiment was performed using the experimental apparatus shown in Fig. 13 in order to verify the effect of the siphon function as described above and the reduction in suction force loss.

The experiment was performed by the following procedure using the experimental apparatus of FIG.
Step 1: After closing the bottom of the vertical water pipe and each valve of the backflow control device, open the valve of the water supply device (siphon function maintaining device) to inject water, and saturate the horizontal water pipe and the vertical water pipe with water. Let
Step 2: After opening the valve of the vertical water pipe and operating the siphon, the pressure in the sealed chamber is gradually lowered using a vacuum pump.
Step 3: The valve of the backflow control device is slightly opened and the pump in the suction force loss elimination device is operated.
Step 4: Measure the working pressure at the top of the horizontal water pipe, the sealed chamber, and the bottom of the height difference part, and measure the amount of water supplied from the water supply device and the flow rate toward the vertical water pipe.

Experimental result

  As a preliminary experiment, the pumping pump in the suction power loss elimination device was not operated, the drainage path with the difference in height was filled with water, and the pure establishment condition of the siphon function in the vertical water pipe was investigated.

  FIG. 14 is a graph showing the time variation of each working pressure measured in the case where the suction force loss eliminating device is not operated in the preliminary experiment (the height difference portion is saturated with water).

  When the siphon functions in the vertical water pipe, the suction force due to the water head difference is exerted, so a higher negative pressure acts in 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, making the siphon difficult to function.

Under the present experimental conditions in which the inner diameter of the vertical water pipe is 3 cm, a bubble mixed flow is formed in the vertical water pipe when the supply flow rate from the siphon function maintenance device (water supply device) is 15 L (liter) / min or more. Was able to maintain the siphon function. In this case, in the vertical water pipe, the condition that the flow velocity of water flowing down the vertical water pipe ν _w > the bubble rising speed ν _a is satisfied, and a bubble mixed flow is formed.

However, even when the siphon is functioning in the vertical water pipe, the suction power loss elimination device is not operated, and in the case where the height difference portion is saturated with water, as shown in FIG. Although a high negative pressure is generated at the top, energy is used to pump up the difference in height, so that a negative pressure loss occurs at the bottom position of the difference in height. The amount of negative pressure loss is about 15 kN / m ² corresponding to a water head with a height difference of 1.5 m at the height difference portion.

  Next, while adjusting the opening and closing of the valve of the backflow control device, the suction force loss elimination device was operated to investigate the feasibility of the siphon function in the vertical water pipe and the suction force loss elimination effect due to gas filling of the height difference part. .

  As a result of the experiment, in order to fill the height difference part with gas while allowing the siphon to function in the vertical water pipe, (1) supply sufficient water from the water supply device, and (2) the valve of the backflow suppression device It was found that it is important to adjust the opening and closing of the water to reduce the flow rate when water flows backward. In this experiment, when the valve of the backflow suppression device was slightly opened and the backflow rate of water supplied from the water supply device was adjusted to about 3%, the establishment of the siphon function and the elimination of the suction force loss were achieved. The amount of water supply to be simultaneously established needs to be about 30 L / min or more.

  In addition, when the opening amount of the valve of the backflow suppression device is increased and the backflow rate of the water supplied from the water supply device is adjusted to about 5 to 10%, the establishment of the siphon function and the elimination of the suction force loss are simultaneously established The amount of water supplied was required to be about 40 L / min or more. If the backflow of water to be supplied is large, it is necessary to increase the amount of water supplied from the water supply device accordingly. However, an excessive burden is placed on the water supply device and the pump, which makes realization difficult. Become.

  FIG. 15 is a graph showing the time fluctuation of each working pressure measured in the case where the backflow rate of water supplied from the water supply device is about 3% and the water supply amount is 30 L / min in this experiment.

  From FIG. 15, due to the establishment of the siphon function, a high negative pressure is generated at the top of the horizontal tube, and since the height difference portion is filled with gas, there is no loss of suction force even at the bottom surface position of the height difference portion. Recognize.

  In this experiment using a vertical water pipe with an inner diameter of 3 cm, the limit water supply amount that simultaneously establishes the siphon function and eliminates the suction force loss is set to be equal to the flow velocity flowing down the vertical water pipe. If converted into a condition using a vertical water pipe, it is 83 L / min, and if converted into a condition of a vertical water pipe having an inner diameter of 10 cm, it is 333 L / min.

  As mentioned above, although the form and Example for implementing this invention were demonstrated, this invention is not limited to these, Various deformation | transformation are possible within the range of the technical idea of this 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.

  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 thereof may be used as long as the suction force acts by the siphon function from the second pipe toward the lower end side of the first pipe due to the difference in water level. 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.

DESCRIPTION OF SYMBOLS 1 Vertical pipe 1a Lower end of a vertical pipe 2 Horizontal pipe 3 Siphon function maintenance apparatus 5a Water supply position 8 Backflow control apparatus 8a Step path 8b Narrow path 9 Water saturation path 11 Vertical water pipe 12 Horizontal water pipe 21 Sealed chamber 22 Pumping pump 25 Vacuum Pump 30 Vacuum decompression device 31 Vertical drain material 35 Suction force loss elimination device 36 Sealed container 37 Pumping pump 38 Drain pipe 38a Check valve 100 Vacuum consolidation ground improvement system G Soft ground Δh Height difference ΔH Water level difference

Claims (10)

A first pipe extending from the upper part toward the lower part; a second pipe connected to the first pipe at the upper part; a lower end side of the first pipe; and the second pipe side A suction force generator in which a suction force acts by a siphon function from the second pipe toward the lower end of the first pipe due to a difference in water level between
A siphon function maintaining device for maintaining a siphon function by supplying water into a drainage path formed from the second pipe toward the lower end side of the first pipe;
A suction force generation device comprising: a backflow suppression device that suppresses a backflow in which the supplied water flows toward the opposite side of the upper portion of the first pipe. In a sealed container disposed before water flows into the drainage path in the second pipe under the condition that the level of the water to be sucked and drained is lower than the uppermost part of the second pipe and has a height difference When the water level is lowered before draining from the drainage pipe and flowing into the drainage path in the sealed container, the drainage path with the height difference is filled with a negative pressure gas so that the suction by the height difference is achieved. The attraction | suction force generation | occurrence | production apparatus of Claim 1 provided with the attraction | suction force loss elimination apparatus which eliminates the loss of force.   The suction force generation device according to claim 2, wherein a check valve is provided in the drain pipe to prevent air from flowing into the suction force loss elimination device. The attraction | suction force generator of Claim 2 or 3 provided with the water saturation path | route comprised from the level | step difference or inclination pipe | tube which becomes high in the downstream so that water may saturate in the said drainage path | route downstream from the said water supply position. .   5. The suction force generation device according to claim 1, wherein the backflow suppression device includes at least one of a flow rate adjustment valve, a step path, an inclined path, and a constriction path.   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 water level difference between the lower end side of the first pipe extending from the upper part toward the lower part and the second pipe side connected to the first pipe at the upper part, the first pipe is removed from the second pipe. A suction force generation method for applying a suction force by a siphon function toward the lower end of a tube,
While maintaining the siphon function by supplying water into the drainage path formed from the second pipe toward the lower end side of the first pipe,
A method for generating a suction force, characterized in that the supplied water is prevented from flowing back toward the opposite side of the upper portion of the first pipe. In a sealed container disposed before water flows into the drainage path in the second pipe under the condition that the level of the water to be sucked and drained is lower than the uppermost part of the second pipe and has a height difference wherein by the water level before flowing drops drainage path loss of the suction force by the difference in height it is filled with the waste water path with the height difference with a gas negative pressure state in the waste water to the airtight container from The suction force generation method according to claim 7, wherein the problem is solved.   A vacuum consolidation characterized by performing ground improvement by vacuum consolidation in a soft ground using the suction force generation device according to any one of claims 1 to 6 or the suction force generation method according to claim 7 or 8. Ground improvement method. Using the suction force generation device according to any one of claims 2 to 4 or the suction force generation method according to claim 8,
At least the lower end side of the first pipe is disposed in a sealed chamber that can be depressurized by a vacuum pump, and a vacuum is generated in soft ground by adding a negative pressure generated by depressurizing the sealed chamber by the vacuum pump to a suction force by the siphon function. A vacuum consolidation ground improvement method characterized by installing the sealed chamber on the ground surface when performing ground improvement by consolidation.

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