JP5305957B2 - Suction force generator and vacuum consolidation ground improvement method - Google Patents
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本発明は、サイフォン機能による吸引力発生装置及びこの吸引力発生装置を用いた真空圧密地盤改良工法に関する。 The present invention relates to a suction force generation device using a siphon function and a vacuum consolidation ground improvement method using the suction force generation device.
吸引力を発生させて水を吸引・排水する装置として、真空ポンプを用いた吸引装置が知られている。従来の技術では、例えば、軟弱地盤内に鉛直ドレーンを打設後、真空ポンプによる吸引装置を用いて、負圧を作用させて地盤内を減圧することによって、地盤の圧密を促進する方法（真空圧密地盤改良工法）が用いられている（例えば、特許文献１〜４参照）。 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, a method of promoting the consolidation of the ground by placing a vertical drain in soft ground and then depressurizing the ground by applying a negative pressure using a vacuum pump suction device (vacuum) The consolidation ground improvement method) is used (for example, refer to Patent Documents 1 to 4).
従来の真空ポンプによる吸引装置は真空ポンプの能力のみに頼って吸引を行っている。このため、従来の吸引装置によれば、真空ポンプの能力以上に圧密を促進する吸引力を作用させることができない。このため、従来の軟弱地盤の真空圧密地盤改良工法において真空ポンプのみでは吸引力が不足する場合は、盛土による載荷を併用しなければならなかった。 A conventional vacuum pump suction device relies only on the capacity of the vacuum pump to perform suction. 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, when the suction force is insufficient with the vacuum pump alone in the conventional vacuum consolidation method for soft ground, it is necessary to use loading with embankment in combination.
また、真空ポンプの力と水面位置の差による力とを利用した吸引装置に関し、水面下の地盤の間隙水の吸引を目的にした水底軟弱地盤の減容化工法が提案されている（特許文献３参照）。この従来技術は、水面が、間隙水を吸引したい地盤よりも高い位置にあることにより、水圧による圧縮力が作用して、間隙水を搾り出すものであり、改良したい地盤が水中にあるとともに、地盤面位置が、排水部（減圧室）の水位よりも低い位置にあるという条件の下でのみ適用できるものである。この従来方法は、改良したい地盤が陸上にあることを想定するものでなく、改良地盤面の天端位置から導かれるホースは、減圧室の側面に結合される形態としている。 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 method for reducing the volume of the soft bottom has been proposed for the purpose of suctioning pore water in the ground below the water surface (Patent Document). 3). In this conventional technology, since the water surface is higher than the ground where the pore water is to be sucked, the compressive force due to the water pressure acts to squeeze the pore water, and the ground to be improved is in the water. It is applicable only under the condition that the ground surface position is lower than the water level of the drainage section (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.
大きな吸引力を作用させる条件では、溶存酸素等の気化や通水管の気密漏れ部から流入する気体の存在を考慮しなければならないが、陸上の地盤の間隙水を吸引するために、この従来方法の形態を単純に変更して、上部から鉛直に管をつなげるだけでは、水と気体の流れが分離してしまうため、サイフォンの原理に従う吸引力は働かない。すなわち、陸上域の地盤を対象にした場合には、従来技術によれば、真空ポンプの能力以上の吸引力を発揮させることはできなかった。 Under conditions that apply a large suction force, it is necessary to consider the vaporization of dissolved oxygen, etc., and the presence of gas flowing in from the airtight leak of the water pipe. By simply changing the shape of the pipe and connecting the pipe vertically from the top, the water and gas flows are separated, so the suction force according to the siphon principle does not work. That is, when the land on the ground is targeted, according to the prior art, it has not been possible to exert a suction force exceeding the capacity of the vacuum pump.
本発明は、水に気体が含まれる場合でもサイフォンの原理に従う吸引力を発生可能な吸引力発生装置を提供することを目的とする。また、地盤改良における真空圧密を促進させ盛土による載荷の縮小や省略及び地盤改良期間の短縮を実現可能な真空圧密地盤改良工法を提供することを目的とする。 An object of this invention is to provide the attraction | suction force generator which can generate | occur | produce the attraction | suction force according to the principle of siphon even when gas is contained in water. 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.
上記目的を達成するために、本実施形態による第１の吸引力発生装置は、上部から下部に向けて延びる第１の管と、前記第１の管と前記上部で接続し水平方向に延びる第２の管と、を有し、前記第１の管の下端側と、前記第２の管の先端側との間の水位差により、前記第２の管の先端から前記第１の管の下端に向けてサイフォン機能により吸引力が作用する吸引力発生装置であって、前記第１の管の通水断面積が前記第２の管の通水断面積よりも小さくなるように構成し、前記第２の管内に水と分離して存在する空気が前記第１の管内で気泡となって気液２相流として流下することでサイフォン機能により吸引力を発生させることを特徴とする。 In order to achieve the above object, the first suction force generator according to the present embodiment includes a first pipe extending from the upper part toward the lower part, and a first pipe extending in the horizontal direction connected to the first pipe and the upper part. And a lower end of the first tube from the tip of the second tube due to a water level difference between the lower end side of the first tube and the tip end side of the second tube. A suction force generating device in which a suction force acts by a siphon function towards the first pipe, wherein the water passage cross-sectional area of the first pipe is smaller than the water cross-sectional area of the second pipe, Air that is separated from water in the second pipe becomes bubbles in the first pipe and flows down as a gas-liquid two-phase flow, thereby generating a suction force by a siphon function.
この吸引力発生装置によれば、第１の管の通水断面積を第２の管の通水断面積よりも小さくすることで、第１の管内でサイフォン機能により吸引力を発生させることができ、第２の管の先端から空気を含む水を吸引し第１の管の下端から排水できる。このため、水に気体が含まれる場合でもサイフォンの原理に従う吸引力を発生させることができる。 According to this suction force generator, the suction force can be generated by the siphon function in the first pipe by making the water passage cross-sectional area of the first pipe smaller than the water cross-sectional area of the second pipe. The water containing air can be sucked from the tip of the second pipe and drained from the lower end of the first pipe. For this reason, even when gas is contained in water, the suction force according to the principle of siphon can be generated.
上記吸引力発生装置において前記第１の管及び前記第２の管は円筒管から構成され、前記第２の管の内径が０．１ｍ以下のとき前記第１の管の内径が前記第２の管の内径の７０％以下に、前記第２の管の内径が０．１ｍを超えるとき前記第１の管の内径が前記第２の管の内径の５０％以下に構成される。
In the suction force generation device, the first tube and the second tube are formed of a cylindrical tube, and when the inner diameter of the second tube is 0.1 m or less, the inner diameter of the first tube is the second tube. to less than 70% of the inner diameter of the tube, the inner diameter of the first tube when the inner diameter of the second tube is more than 0.1m is Ru is configured to less than 50% of the inner diameter of the second tube.
本実施形態による第２の吸引力発生装置は、上部から下部に向けて延びる第１の管と、前記第１の管と前記上部で接続し水平方向に延びる第２の管と、を有し、前記第１の管の下端側と、前記第２の管の先端側との間の水位差により、前記第２の管の先端から前記第１の管の下端に向けてサイフォン機能により吸引力が作用する吸引力発生装置であって、前記第１の管を複数本設け、前記各第１の管の通水断面積が前記第２の管の通水断面積よりもそれぞれ小さくかつ互いに異なるように前記各第１の管を構成し、前記第２の管に対し前記第１の管を切り替え可能に構成したことを特徴とする。 The second suction force generator according to the present embodiment includes a first pipe extending from the upper part toward the lower part, and a second pipe connected to the first pipe at the upper part and extending in the horizontal direction. Due to the difference in water level between the lower end side of the first tube and the distal end side of the second tube, the suction force by the siphon function from the distal end of the second tube toward the lower end of the first tube A plurality of the first pipes, each having a water passage cross-sectional area smaller than that of the second pipe and different from each other. As described above, each of the first pipes is configured such that the first pipe can be switched with respect to the second pipe.
この吸引力発生装置によれば、第１の管内でサイフォン機能により吸引力を発生させることができ、第２の管の先端から空気を含む水を吸引し第１の管の下端から排水できる。このため、水に気体が含まれる場合でもサイフォンの原理に従う吸引力を発生させることができる。さらに、通水断面積が互いに異なる複数の第１の管を第２の管に対し切り替え可能にすることで、第２の管における流入水量の増減に対応して第１の管を切り替えることができ、流入水量の変動に対応することができる。 According to this suction force generator, suction force can be generated by the siphon function in the first pipe, and water containing air can be sucked from the tip of the second pipe and drained from the lower end of the first pipe. For this reason, even when gas is contained in water, the suction force according to the principle of siphon can be generated. Furthermore, by switching a plurality of first pipes having different water flow cross-sectional areas with respect to the second pipe, the first pipe can be switched in response to an increase or decrease in the amount of inflow water in the second pipe. It can cope with fluctuations in the amount of inflow water.
上記吸引力発生装置において前記第１の管及び前記第２の管を円筒管から構成し前記各第１の管の内径がそれぞれ異なるように構成することで、また、前記複数本の第１の管の少なくとも１つの管内に付帯物を設けることで、第１の管の通水断面積を調整することができる。 In the suction force generation device, the first tube and the second tube are formed of cylindrical tubes, and the first tubes are configured such that inner diameters of the first tubes are different from each other. By providing an accessory in at least one of the pipes, the water flow cross-sectional area of the first pipe can be adjusted.
なお、上記第１及び第２の吸引力発生装置において第１の管は、鉛直方向に延びるように設置されてよいが、鉛直方向に設置されるものに限定されず、傾斜して設置してもよく、さらに、直線形状に限定されるものでなく、気泡の上昇速度を抑えるために、屈折部や屈曲部を含む形状であってもよい。 In the first and second suction force generators, the first tube may be installed so as to extend in the vertical direction, but is not limited to the one installed in the vertical direction, and is installed at an inclination. In addition, the shape is not limited to a linear shape, and may include a shape including a refracting portion or a bent portion in order to suppress the rising speed of bubbles.
本実施形態による第３の吸引力発生装置は、上部から下部に向けて延びる第１の管と、前記第１の管と前記上部で接続し水平方向に延びる第２の管と、を有し、前記第１の管の下端側と、前記第２の管の先端側との間の水位差により、前記第２の管の先端から前記第１の管の下端に向けてサイフォン機能により吸引力が作用する吸引力発生装置であって、前記第１の管の通水断面積が前記第２の管の通水断面積よりも小さくなるように前記第１の管内に不透水棒を配置したことを特徴とする。 The third suction force generator according to the present embodiment includes a first pipe extending from the upper part toward the lower part, and a second pipe connected to the first pipe at the upper part and extending in the horizontal direction. Due to the difference in water level between the lower end side of the first tube and the distal end side of the second tube, the suction force by the siphon function from the distal end of the second tube toward the lower end of the first tube The impermeable rod is arranged in the first pipe so that the cross-sectional area of the first pipe is smaller than the cross-sectional area of the second pipe. It is characterized by that.
この吸引力発生装置によれば、第１の管内に不透水棒を配置することで、第１の管内でサイフォン機能により吸引力を発生させることができ、第２の管の先端から空気を含む水を吸引し第１の管の下端から排水できる。このため、水に気体が含まれる場合でもサイフォンの原理に従う吸引力を発生させることができる。 According to this suction force generation device, by arranging an impermeable rod in the first tube, suction force can be generated by the siphon function in the first tube, and air is contained from the tip of the second tube. Water can be sucked and drained from the lower end of the first tube. For this reason, even when gas is contained in water, the suction force according to the principle of siphon can be generated.
上記第１〜第３の吸引力発生装置は真空ポンプによる動力装置を併用することが好ましい。これにより、サイフォン機能が停止した場合に、その再開を容易に行うことができる。 The first to third suction force generators are preferably used in combination with a power device using a vacuum pump. Thereby, when a siphon function stops, the restart can be performed easily.
本実施形態による真空圧密地盤改良工法は、上述の吸引力発生装置を用いて軟弱地盤において真空圧密による地盤改良を行うことを特徴とする。 The vacuum consolidation ground improvement method according to the present embodiment is characterized in that ground improvement by vacuum consolidation is performed on soft ground using the above-described suction force generator.
この真空圧密地盤改良工法によれば、上述の吸引力発生装置によるサイフォン機能の吸引を併用することで地盤改良における真空圧密を促進させることができ、盛土による載荷の縮小や省略を図ることができるため、使用資材・機材の節減や作業工期の短縮を実現でき、また、従来の真空圧密工法に比べて吸引力が増加するため、軟弱地盤が所定の強度に達するまでに要する地盤改良期間を短縮することができる。 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 above-described suction force generator together, and the load due to the embankment can be reduced or omitted. Therefore, it is possible to reduce the amount of materials and equipment used and shorten the work period, and the suction force increases compared with the conventional vacuum consolidation method, so the ground improvement period required for the soft ground to reach the specified strength is shortened. can do.
なお、本実施形態による吸引力発生方法は、上部から下部に向けて延びる第１の管の下端側と、前記第１の管と前記上部で接続し水平方向に延びる第２の管の先端側との間の水位差により、前記第２の管の先端から前記第１の管の下端に向けてサイフォン機能により吸引力が作用する吸引力発生方法であって、前記第１の管の通水断面積を前記第２の管の通水断面積よりも小さくし、前記第２の管内に水と分離して存在する空気が前記第１の管内で気泡となって気液２相流として流下することでサイフォン機能により吸引力を発生させることを特徴とする。 The suction force generation method according to the present embodiment includes a lower end side of a first tube extending from the upper portion toward the lower portion, and a distal end side of a second tube extending in the horizontal direction by connecting the first tube to the upper portion. A suction force generating method 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 between the first tube and the water flow of the first tube The cross-sectional area is made smaller than the water flow cross-sectional area of the second pipe, and the air existing separately from the water in the second pipe flows as bubbles in the first pipe as a gas-liquid two-phase flow Thus, a suction force is generated by a siphon function.
この吸引力発生方法によれば、第１の管の通水断面積が第２の管の通水断面積よりも小さいことにより、第２の管内に水と分離して存在する空気が第１の管内で気泡となって気液２相流として流下しサイフォン機能により吸引力を発生させることができる。なお、第１の管の通水断面積を第２の管の通水断面積よりも小さくするには、円筒管の場合は内径の小さい管を用いること、管内に付帯物を設けること、管内に不透水棒を配置することなどによって実現できる。 According to this suction force generation method, the water cross-sectional area of the first pipe is smaller than the water cross-sectional area of the second pipe, so that the air existing separately from the water in the second pipe is the first. It becomes a bubble in the pipe and flows down as a gas-liquid two-phase flow, and a suction force can be generated by the siphon function. In order to make the water flow cross-sectional area of the first pipe smaller than the water flow cross-sectional area of the second pipe, in the case of a cylindrical pipe, use a pipe having a small inner diameter, provide an accessory in the pipe, This can be realized by arranging a water-impermeable rod.
なお、本明細書において、通水断面積とは、第１の管及び第２の管において通水が実質的に可能な断面の面積を意味し、円筒管の場合は内径を２ｒとすると、πｒ2である。また、気液２相流とは、液体と気泡が混合した流れのことである。 In addition, in this specification, the water flow cross-sectional area means an area of a cross section in which water flow is substantially possible in the first pipe and the second pipe, and in the case of a cylindrical pipe, the inner diameter is 2r. πr 2 . A gas-liquid two-phase flow is a flow in which liquid and bubbles are mixed.
本発明の吸引力発生装置によれば、水に気体が含まれる場合でもサイフォンの原理に従う吸引力を発生させることができる。 According to the suction force generator of the present invention, suction force according to the principle of siphon can be generated even when water contains gas.
本発明の真空圧密地盤改良工法によれば、上述の吸引力発生装置を真空ポンプと併用することにより、地盤改良における真空圧密を促進させることができ、盛土による載荷の縮小や省略及び地盤改良期間の短縮を実現できる。 According to the vacuum consolidation ground improvement method of the present invention, by using the above suction force generator together with a vacuum pump, vacuum consolidation in ground improvement can be promoted, load reduction or omission due to embankment and ground improvement period Can be shortened.
以下、本発明を実施するための形態について図面を用いて説明する。 Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
〈第１の実施形態〉
図１は第１の実施形態による吸引力発生装置の構成を概略的に示す図である。図２は図１の吸引力発生装置におけるサイフォン機能による水と空気との流れを説明するための模式図（ａ）及びサイフォン機能による水と空気との流れを実現できない状態を説明するための模式図（ｂ）である。なお、図１，図２の縦方向が鉛直方向、横方向が水平方向である。
<First Embodiment>
FIG. 1 is a diagram schematically showing a configuration of a suction force generator according to the first embodiment. 2 is a schematic diagram (a) for explaining the flow of water and air by the siphon function in the suction power generation device of FIG. 1, and a schematic for explaining the state where the flow of water and air by the siphon function cannot be realized. FIG. 1 and 2, the vertical direction is the vertical direction, and the horizontal direction is the horizontal direction.
図１の吸引力発生装置は、上部から下部に向けて鉛直方向に延びる第１の管としての鉛直管１と、鉛直管１の上部で接続し水平方向に延びる第２の管としての水平管２と、を有し、鉛直管１及び水平管２は円筒管からなる。鉛直管１は、鉛直管１の内径が水平管２の内径の５０％以下（水平管２の内径が０．１ｍを超えるとき）または７０％以下（水平管２の内径が０．１ｍ以下のとき）に構成されることで、鉛直管１の通水断面積が水平管２の通水断面積よりも小さくなっている。 1 includes a vertical pipe 1 as a first pipe extending in the vertical direction from the upper part toward the lower part, and a horizontal pipe as a second pipe connected to the upper part of the vertical pipe 1 and extending in the horizontal direction. 2, and the vertical pipe 1 and the horizontal pipe 2 are cylindrical pipes. The vertical pipe 1 has an inner diameter of the vertical pipe 1 of 50% or less (when the inner diameter of the horizontal pipe 2 exceeds 0.1 m) or 70% or less (the inner diameter of the horizontal pipe 2 is 0.1 m or less). The vertical cross-sectional area of the vertical pipe 1 is smaller than the horizontal cross-sectional area of the horizontal pipe 2.
図１のように、鉛直管１の下端１ａが水中にあるとき、その排水面と水平管２の先端２ａ側の水面との間の水位差ΔＨに起因するサイフォン機能により鉛直管１の下端１ａ側に吸引力が発生することで、破線で示す方向ｆに水が流れる。なお、図１の排水面が鉛直管１の下端１ａに達していないときは、鉛直管１の下端１ａと水平管２の先端２ａ側の水面との間の水位差に起因するサイフォン機能により鉛直管１の下端１ａ側に吸引力が発生する。 As shown in FIG. 1, when the lower end 1a of the vertical pipe 1 is in water, the lower end 1a of the vertical pipe 1 is caused by a siphon function caused by the water level difference ΔH between the drainage surface and the water surface on the tip 2a side of the horizontal pipe 2. By generating a suction force on the side, water flows in a direction f indicated by a broken line. When the drainage surface of FIG. 1 does not reach the lower end 1a of the vertical pipe 1, the siphon function caused by the water level difference between the lower end 1a of the vertical pipe 1 and the water surface on the front end 2a side of the horizontal pipe 2 causes vertical A suction force is generated on the lower end 1 a side of the tube 1.
ここで、水平管２内に気体が含まれる条件においてサイフォンの原理に従って吸引力を作用させるためには、鉛直管１内において水と気体を分離させず、一体的に流下させなければならない。図１の吸引力発生装置では、図２（ａ）のように、水平管２内において空気と水とが分離して流れても、水平管２よりも内径の小さい鉛直管１内においては空気が多数の気泡Ｂとして取り込まれ、気液２相流として一体的に方向ｆに流下することで、鉛直管１内においてサイフォンの原理が成立し、水位差ΔＨによる吸引力が発生する状態となる。 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. 1, even if air and water flow separately in the horizontal pipe 2 as shown in FIG. 2A, the air is generated in the vertical pipe 1 having an inner diameter smaller than that of the horizontal pipe 2. Is taken in as a large number of bubbles B and flows down in the direction f integrally as a gas-liquid two-phase flow, whereby the principle of siphon is established in the vertical pipe 1, and a suction force due to a water level difference ΔH is generated. .
ここで、図２（ｂ）のように、水平管と鉛直管とが同じ径であり各通水断面積が同じであると、水平管内で空気と水とが分離して流れ、鉛直管内でも水と空気が分離して流下し、サイフォンの原理が成立せず、水位差による吸引力が発生しない状態となる。 Here, as shown in FIG. 2 (b), when the horizontal pipe and the vertical pipe have the same diameter and the same water flow cross-sectional area, air and water flow separately in the horizontal pipe, and even in the vertical pipe. Water and air are separated and flow down, the siphon principle is not established, and no suction force is generated due to the difference in water level.
上述のように、鉛直管１の内径を水平管２の内径よりも小さくした吸引力発生装置により、鉛直管１内で水と気体が混合した気液２相流を形成させ、サイフォンを機能させる。このとき、水平管２の先端２ａ側の流入部の水位と鉛直管１の下端１ａ側の水位との水位差に起因する吸引力（流体が重力に従って下方に移動しようとすることによる吸引力）が作用する。したがって、従来の真空ポンプによる吸引装置と比較すると、真空ポンプに頼らずにサイフォンの自然エネルギーを極力使用することによって、電力等のコストを削減することが可能になる。 As described above, a gas-liquid two-phase flow in which water and gas are mixed in the vertical pipe 1 is formed in the vertical pipe 1 by the suction force generator in which the inner diameter of the vertical pipe 1 is smaller than the inner diameter of the horizontal pipe 2, and the siphon functions. . At this time, a suction force due to a water level difference between the water level at the inflow portion on the tip 2a side of the horizontal tube 2 and the water level on the lower end 1a side of the vertical tube 1 (suction force due to the fluid trying to move downward according to gravity) Works. Therefore, as compared with a suction device using a conventional vacuum pump, it is possible to reduce costs such as electric power by using the natural energy of the siphon as much as possible without depending on the vacuum pump.
また、従来の真空ポンプを併用すれば、真空ポンプの能力以上の吸引力を発揮することができ、例えば、軟弱地盤の間隙水をより多く吸引し排水し、圧密を大きく促進させることが可能となる。 In addition, if a conventional vacuum pump is used in combination, a suction force exceeding the capacity of the vacuum pump can be exerted. For example, it is possible to suck and drain a larger amount of pore water in soft ground and greatly promote consolidation. Become.
また、鉛直管１内の水位差による吸引力が効果的に発揮されるためには、１０ｋＰａ程度以上の吸引力が作用するように地下水位面から下の鉛直透水管の長さを１ｍ以上にすることが好ましい。 Moreover, in order for the suction force due to the water level difference in the vertical pipe 1 to be effectively exhibited, the length of the vertical permeation pipe below the groundwater level surface is set to 1 m or more so that a suction force of about 10 kPa or more acts. It is preferable to do.
また、図１の吸引力発生装置は、サイフォン機能がいったん停止した後に、サイフォンを再開させる場合などを考えると、真空ポンプの動力装置と併用することが好ましい。 Further, the suction force generating device of FIG. 1 is preferably used in combination with a power device of a vacuum pump in consideration of a case where the siphon is restarted after the siphon function is temporarily stopped.
次に、鉛直管１の内径が好ましくは水平管２の内径の５０％以下（水平管２の内径が０．１ｍを超えるとき）及び７０％以下（水平管２の内径が０．１ｍ以下のとき）であることについて図６を参照して説明する。 Next, the inner diameter of the vertical tube 1 is preferably 50% or less (when the inner diameter of the horizontal tube 2 exceeds 0.1 m) and 70% or less (the inner diameter of the horizontal tube 2 is 0.1 m or less). This will be described with reference to FIG.
浮力による気泡の上昇速度νaは、浮力と抗力のつりあいにより、次の式（１）によって評価できる。 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.
νa＝［８ｇｒa／（３ＣD）］0.5 （１）
ここで、ｒa：気泡の半径（最大で管内径の１／２）である。また、ＣDは抗力係数であり、０．５で与えられる。
ν a = [8 gr a / (3C D )] 0.5 (1)
Here, r a is the bubble radius (maximum ½ of the inner diameter of the tube). Also, C D is the drag coefficient is given by 0.5.
また、鉛直管に流入してくる水の流量がＱのとき、管の断面積をＡとすると、鉛直管を流下する水の流速νwは、次の式（２）で評価できる。 Further, when the flow rate of water flowing into the vertical pipe is Q and the cross-sectional area of the pipe is A, the flow velocity ν w of the water flowing down the vertical pipe can be evaluated by the following equation (2).
νw＝Ｑ／Ａ （２） ν w = Q / A (2)
上記式（２）によれば、水平管から流入してくる流量に対して、鉛直管の内径を小さくし、通水断面積を小さくすると、流速が増加することがわかる。サイフォンが機能する条件として、気泡が水の流れに連行され、気液２相流が形成されるためには、鉛直管の内径を次の条件式（３）を満足するように定めることが重要である。 According to the above formula (2), it can be seen that the flow velocity increases when the inner diameter of the vertical pipe is reduced and the cross-sectional area of water flow is reduced with respect to the flow rate flowing from the horizontal pipe. As a condition for the siphon to function, in order for bubbles to be entrained in the water flow and a gas-liquid two-phase flow to be formed, it is important to determine the inner diameter of the vertical pipe to satisfy the following conditional expression (3) It is.
νw＞νa （３） ν w > ν a (3)
図６は、縮小すべき鉛直管の内径を水平管の内径に対して水平管の内径に対する比で示す図であり、水平管内における流速が１．０ｍ／ｓ、０．７５ｍ／ｓ、０．５０ｍ／ｓである場合について上記式（１）（２）（３）を用いて評価したものである。用いる水平管の内径に対して、図６にプロットされる点よりも、小さい内径の鉛直管を用いれば、気液２相流が形成されることを示しており、例えば、水平管の内径が０．１５ｍのとき、鉛直管の内径が水平管の内径の５５％程度より小さければ、気液２相流が形成されることを意味している。図６から、水平管の内径が０．１ｍ以下のとき水平管の内径に対して鉛直管の内径を７０％以下に設定し、水平管の内径が０．１ｍを超えるとき水平管の内径に対して鉛直管の内径を５０％以下に設定すれば、気液２相流が形成されることが明らかである。 FIG. 6 is a diagram showing the inner diameter of the vertical pipe to be reduced as a ratio of the inner diameter of the horizontal pipe to the inner diameter of the horizontal pipe. The flow velocity in the horizontal pipe is 1.0 m / s, 0.75 m / s,. The case of 50 m / s was evaluated using the above formulas (1), (2), and (3). This shows that a gas-liquid two-phase flow is formed when a vertical pipe having a smaller inner diameter than the point plotted in FIG. 6 is used with respect to the inner diameter of the horizontal pipe to be used. If the inner diameter of the vertical pipe is smaller than about 55% of the inner diameter of the horizontal pipe at 0.15 m, it means that a gas-liquid two-phase flow is formed. From FIG. 6, when the inner diameter of the horizontal pipe is 0.1 m or less, the inner diameter of the vertical pipe is set to 70% or less with respect to the inner diameter of the horizontal pipe, and when the inner diameter of the horizontal pipe exceeds 0.1 m, On the other hand, if the inner diameter of the vertical pipe is set to 50% or less, it is clear that a gas-liquid two-phase flow is formed.
次に、通水断面積が異なる複数本の鉛直管を水平管に対し切り替え可能に構成した別の吸引力発生装置の構成について図３を参照して説明する。図３は第１の実施形態による別の吸引力発生装置の構成を概略的に示す図である。 Next, a configuration of another suction force generator configured to switch a plurality of vertical tubes having different water flow cross-sectional areas with respect to the horizontal tube will be described with reference to FIG. FIG. 3 is a diagram schematically showing the configuration of another suction force generator according to the first embodiment.
図３の吸引力発生装置は、円筒管からなる水平管２に対し円筒管からなる複数本の鉛直管１１，１２，１３を切り替え可能に設けたものである。複数本の鉛直管１１，１２，１３の各内径は、それぞれ異なり、順に小さく構成されるとともに、いずれも水平管２の内径よりも小さくなっている。 The suction force generator shown in FIG. 3 is provided such that a plurality of vertical tubes 11, 12, and 13 made of cylindrical tubes can be switched with respect to a horizontal tube 2 made of cylindrical tubes. The inner diameters of the plurality of vertical tubes 11, 12, and 13 are different from each other, are configured to be smaller in order, and are all smaller than the inner diameter of the horizontal tube 2.
各鉛直管１１〜１３は、それらの上部でそれぞれバルブ１１ｂ，１２ｂ，１３ｂを介して水平管２に接続しており、バルブ１１ｂ〜１３ｂの開閉により、いずれかの鉛直管１１，１２または１３が水平管２に対し通水可能となる。図１，図２（ａ）と同様に、その排水面（または、各鉛直管１１〜１３の下端１１ａ，１２ａ，１３ａ）と水平管２の先端２ａとの間の水位差に起因するサイフォン機能により鉛直管１１〜１３の下端１１ａ〜１３ａ側に吸引力が発生することで、図の下方に水が流れる。 Each of the vertical pipes 11 to 13 is connected to the horizontal pipe 2 via valves 11b, 12b, and 13b at the top thereof, and any of the vertical pipes 11, 12 or 13 is opened or closed by opening or closing the valves 11b to 13b. Water can be passed through the horizontal pipe 2. Similar to FIGS. 1 and 2 (a), the siphon function caused by the water level difference between the drainage surface (or the lower ends 11a, 12a, 13a of the vertical pipes 11 to 13) and the tip 2a of the horizontal pipe 2 As a result, a suction force is generated on the lower ends 11a to 13a of the vertical pipes 11 to 13, so that water flows downward in the figure.
図３の吸引力発生装置では、水平管２に対する流入水量の増減に対応して鉛直管１１〜１３をバルブ１１ｂ〜１３ｂの開閉により切り替えることで、流入水量の変動に対応することができる。すなわち、水平管２への流入水量が減少すれば、鉛直管１１→１２→１３のように内径の小さい鉛直管に切り替えることで、流入水量が減少してもサイフォン機能を維持できる。水平管２への流入水量が増加すれば、鉛直管１３→１２→１１のように内径の大きい鉛直管に切り替えることで、流入水量が増加した場合に排水量を大きくできる。 In the suction power generation device of FIG. 3, the vertical pipes 11 to 13 are switched by opening and closing the valves 11 b to 13 b in response to the increase and decrease of the inflow water quantity with respect to the horizontal pipe 2, thereby responding to fluctuations in the inflow water quantity. That is, if the amount of inflow water to the horizontal pipe 2 decreases, the siphon function can be maintained even if the inflow water amount decreases by switching to a vertical pipe having a small inner diameter such as the vertical pipes 11 → 12 → 13. If the amount of inflow water to the horizontal pipe 2 increases, the amount of drainage can be increased when the amount of inflow water increases by switching to a vertical pipe having a large inner diameter such as vertical pipes 13 → 12 → 11.
なお、図３のように、水平管２内に流れる水量を測定する水量計１５を水平管２に設けるとともに、バルブ１１ｂ〜１３ｂを電動式自動開閉バルブから構成し、水量計１５の水量測定結果に基づいてバルブ１１ｂ〜１３ｂを自動的に開閉制御するようにしてもよい。 As shown in FIG. 3, a water meter 15 for measuring the amount of water flowing in the horizontal pipe 2 is provided in the horizontal pipe 2, and the valves 11 b to 13 b are constituted by electric automatic open / close valves. The valves 11b to 13b may be automatically controlled to open and close based on the above.
次に、図３の鉛直管１１〜１３内の通水断面積を水平管２内の通水断面積よりも小さくするための別の構成例について図４を参照して説明する。 Next, another configuration example for making the water cross-sectional area in the vertical pipes 11 to 13 in FIG. 3 smaller than the water cross-sectional area in the horizontal pipe 2 will be described with reference to FIG. 4.
図４（ａ）の例は、鉛直管１１〜１３の内面に内面から半径方向に突き出るように複数の突起体６を設けたものである。図４（ｂ）の例は鉛直管１１〜１３内に網状体７を充填したものである。網状体７は、立体的に網目状になって透水可能であれば、いずれの材料も使用でき、例えば、金網、針金を丸めたものなどを使用できるが、これらに限定されるものではない。 In the example of FIG. 4A, a plurality of protrusions 6 are provided on the inner surfaces of the vertical pipes 11 to 13 so as to protrude in the radial direction from the inner surfaces. In the example of FIG. 4B, the mesh body 7 is filled in the vertical pipes 11 to 13. Any material can be used for the mesh body 7 as long as it is three-dimensionally mesh-like and can be permeable to water. For example, a wire mesh or a rolled wire can be used, but is not limited thereto.
図４（ａ）（ｂ）のように、鉛直管１１〜１３の内面に突起体６や網状体７などの付帯物を設けることで、鉛直管１１〜１３の通水断面積を水平管２の通水断面積よりも小さくなるように調整できるとともに、このような付帯物に水と空気の流れが衝突すると、渦ができ易く、水と空気が混合する状態をより生成し易くなる効果を得ることができる。図３の鉛直管１１〜１３においてそれらの内径が同一であっても図３と同様の効果を得ることができる。また、突起体６の大きさや取り付け個数、または、網状体７の網目の大きさや充填量などを変えることで鉛直管１１〜１３の通水断面積を調整できる。 As shown in FIGS. 4 (a) and 4 (b), by providing the inner surfaces of the vertical pipes 11 to 13 with incidental objects such as the protrusions 6 and the net-like body 7, the water flow cross-sectional areas of the vertical pipes 11 to 13 are set to the horizontal pipe 2. The flow cross-sectional area can be adjusted to be smaller, and if the flow of water and air collides with such an accessory, vortices are easily formed, and the effect of making it easier to generate a state where water and air are mixed is achieved. Can be obtained. Even if the inner diameters of the vertical tubes 11 to 13 in FIG. 3 are the same, the same effect as in FIG. 3 can be obtained. Moreover, the water flow cross-sectional area of the vertical pipes 11-13 can be adjusted by changing the magnitude | size and attachment number of the protrusion body 6, or the magnitude | size of the mesh | network of the mesh body 7, and the filling amount.
なお、図４（ａ）（ｂ）の例では、鉛直管１１〜１３のすべてに付帯物を設ける必要はなく、いずれか１つまたは２つに設けてもよく、また、内径を変えかつ付帯物を設けるようにしてもよい。また、図４（ａ）（ｂ）の構成を図３の鉛直管に適用してもよい。 In the examples of FIGS. 4A and 4B, it is not necessary to provide an accessory for all of the vertical pipes 11 to 13, and any one or two of them may be provided. You may make it provide a thing. Moreover, you may apply the structure of Fig.4 (a) (b) to the vertical pipe of FIG.
次に、鉛直管内に不透水棒を配置することで鉛直管の通水断面積を変えるようにしたさらに別の吸引力発生装置の構成について図５を参照して説明する。図５は第１の実施形態によるさらに別の吸引力発生装置の構成を概略的に示す図である。 Next, a configuration of still another suction force generating device in which a water-permeable cross-sectional area of a vertical pipe is changed by disposing an impermeable rod in the vertical pipe will be described with reference to FIG. FIG. 5 is a diagram schematically showing a configuration of still another suction force generator according to the first embodiment.
図５の吸引力発生装置は、鉛直管１内に不透水材料からなる不透水棒３を設置することで、鉛直管１の通水断面積を水平管２の通水断面積よりも小さくするように構成したものである。具体的には、鉛直管１と水平管２との接続部４の上部の開口を蓋５で開閉可能に構成し、蓋５を開いて不透水棒３を挿入し載置部５ａに載せてから蓋５を閉じる。不透水棒３は、例えば円筒管から構成でき、鉛直管１の下端１ａ近傍まで延びるようにし、また円筒管内には水が流れないようにする。載置部５ａは、例えば、不透水棒３の上端をフランジ構造とし、そのフランジが接続部４内に設けた受け部に載るように構成できる。 The suction force generator of FIG. 5 installs the water-impermeable rod 3 made of a water-impermeable material in the vertical pipe 1 so that the water flow cross-sectional area of the vertical pipe 1 is smaller than the water flow cross-sectional area of the horizontal pipe 2. It is comprised as follows. Specifically, the upper opening of the connection part 4 between the vertical pipe 1 and the horizontal pipe 2 is configured to be openable and closable with a lid 5, the lid 5 is opened and the water-impermeable rod 3 is inserted and placed on the placement part 5 a. Close the lid 5. The impervious rod 3 can be composed of, for example, a cylindrical tube, extends to the vicinity of the lower end 1a of the vertical tube 1, and prevents water from flowing into the cylindrical tube. The mounting portion 5 a can be configured so that, for example, the upper end of the water-impermeable rod 3 has a flange structure, and the flange is mounted on a receiving portion provided in the connection portion 4.
図５のように、鉛直管１内に不透水棒３を設置することで、鉛直管１内の通水断面積を水平管２内の通水断面積よりも小さくなるように調整できるので、図２（ａ）と同様のサイフォン機能を得ることができる。また、不透水棒３の外径を変えることで鉛直管１内の通水断面積を調整できる。また、通常の鉛直管と水平管とを有する装置を、鉛直管を小さい径のものに取り替えなくとも、図２（ａ）と同様のサイフォン機能を持つように迅速に対応させることができる。 As shown in FIG. 5, by installing the impermeable rod 3 in the vertical pipe 1, the water cross-sectional area in the vertical pipe 1 can be adjusted to be smaller than the water cross-sectional area in the horizontal pipe 2. A siphon function similar to that shown in FIG. In addition, the cross sectional area of the water passage in the vertical pipe 1 can be adjusted by changing the outer diameter of the water-impermeable rod 3. Further, an apparatus having a normal vertical pipe and a horizontal pipe can be quickly adapted to have the same siphon function as that of FIG. 2A without replacing the vertical pipe with a small diameter pipe.
なお、図５の例では、鉛直管１の内径は、水平管２の内径と同じであってよく、また、大きくてもよい。 In the example of FIG. 5, the inner diameter of the vertical pipe 1 may be the same as the inner diameter of the horizontal pipe 2 or may be larger.
また、図５の鉛直管内に不透水棒を配置する構成は、図３の吸引力発生装置に適用してもよく、例えば、各鉛直管１１〜１３の内径を同一にし、各鉛直管１１〜１３に設置する不透水棒の外径を変えることで各鉛直管の通水断面積を調整するようにしてもよい。 Moreover, the structure which arrange | positions an impermeable rod in the vertical pipe | tube of FIG. 5 may be applied to the attraction | suction force generator of FIG. 3, for example, makes the internal diameter of each vertical pipe | tube 11-13 the same, You may make it adjust the water flow cross-sectional area of each vertical pipe | tube by changing the outer diameter of the impermeable rod installed in 13. FIG.
〈第２の実施形態〉
図７は第２の実施形態による真空圧密地盤改良工法を行うシステム構成を概略的に示す図である。
<Second Embodiment>
FIG. 7 is a diagram schematically showing a system configuration for performing the vacuum consolidation ground improvement method according to the second embodiment.
図７の真空圧密地盤改良システムＳＡは、図の破線で示す真空減圧装置２０を備え、真空減圧装置２０の水平通水管２２に、真空圧密地盤改良のために軟弱地盤Ｇ中に打設される鉛直ドレーン材３１が不透気部３２と接続部３３とを介して連結されている。 The vacuum consolidation ground improvement system SA in FIG. 7 includes a vacuum decompression device 20 indicated by a broken line in the figure, and is placed in a horizontal ground pipe 22 of the vacuum decompression device 20 in a soft ground G for improvement of the vacuum consolidation ground. The vertical drain material 31 is connected through the air-impermeable portion 32 and the connection portion 33.
真空減圧装置２０は、鉛直通水管２１と、鉛直通水管２１の上端に接続された水平通水管２２と、真空ポンプ２３と、排水設備である揚水ポンプ２４・排水管２５と、地中内部に設置された密閉室２６と、を備える。密閉室２６は、鉛直通水管２１と揚水ポンプ２４・排水管２５とを収納し、真空ポンプ２３により減圧されることで、真空減圧装置２０は減圧発生源として機能するようになっている。 The vacuum pressure reducing device 20 includes a vertical water pipe 21, a horizontal water pipe 22 connected to the upper end of the vertical water pipe 21, a vacuum pump 23, a pumping pump 24 and a drain pipe 25 as drainage equipment, and an underground And an installed sealed chamber 26. The sealed chamber 26 accommodates the vertical water pipe 21, the pumping pump 24, and the drain pipe 25, and is decompressed by the vacuum pump 23 so that the vacuum decompression device 20 functions as a decompression generation source.
また、鉛直通水管２１及び水平通水管２２は、図１，図２（ａ）の鉛直管１及び水平管２に対応し、それぞれ円筒管からなり、鉛直通水管２１の内径は、図１，図２（ａ）のように、水平通水管２２の内径よりも小さくなっている。 Moreover, the vertical water pipe 21 and the horizontal water pipe 22 correspond to the vertical pipe 1 and the horizontal pipe 2 in FIG. 1 and FIG. As shown in FIG. 2A, the inner diameter of the horizontal water pipe 22 is smaller.
鉛直ドレーン材３１は、軟弱地盤Ｇ内の間隙水を吸引するために軟弱地盤Ｇ内に打設され、鉛直ドレーン材３１の上端に接続される不透気部３２は地下水位面Ｈ０に位置する。不透気部３２の上端が地表面Ｇ１上で接続部３３を介して真空減圧装置２０の水平通水管２２に連結される。 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 H0. . The upper end of the air-impermeable portion 32 is connected to the horizontal water pipe 22 of the vacuum pressure reducing device 20 via the connection portion 33 on the ground surface G1.
なお、鉛直ドレーン材３１は、軟弱地盤Ｇ内に必要に応じて複数本打設され、不透気部３２や接続部３３とともに、例えば、特許文献１〜３に開示された構成とすることができる。 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 1 to 3, for example, together with the air-impermeable portion 32 and the connection portion 33. it can.
軟弱地盤Ｇ内で鉛直ドレーン材３１により方向ａに吸引された間隙水が水平通水管２２，鉛直通水管２１を方向ｂに流れて鉛直通水管２１の下端２１ａから排水され、密閉室２６の底部に貯留するが、その貯留水は、揚水ポンプ２４により排水管２５を方向ｃに流れて外部に排水される。 The pore water sucked in the direction a by the vertical drain material 31 in the soft ground G flows through the horizontal water pipe 22 and the vertical water pipe 21 in the direction b and is drained from the lower end 21a of the vertical water pipe 21, and the bottom of the sealed chamber 26 However, the stored water flows through the drain pipe 25 in the direction c by the pumping pump 24 and is drained to the outside.
図７の真空圧密地盤改良システムＳＡによる真空圧密地盤改良工法を説明すると、真空減圧装置２０の真空ポンプ２３で密閉室２６内を減圧することによる吸引力に加えて、地下水位面Ｈ０と密閉室２６内の水位面Ｈ１との水位差ΔＨ（＝Ｈ０−Ｈ１）に起因するサイフォン機能による吸引力が発生し、これらの吸引力により軟弱地盤Ｇ内の間隙水を吸引することで軟弱地盤Ｇを圧密する。この真空圧密を、真空ポンプ２３のみで吸引する場合と比べて水位差ΔＨに起因する吸引力が加わる分だけより大きな吸引力で行うことができる。 The vacuum consolidation ground improvement method by the vacuum consolidation ground improvement system SA in FIG. 7 will be described. In addition to the suction force generated by the vacuum pump 23 of the vacuum decompression device 20 reducing the pressure in the sealed chamber 26, the groundwater level surface H0 and the sealed chamber The suction force by the siphon function due to the water level difference ΔH (= H0−H1) with the water level surface H1 in 26 is generated, and the soft ground G is sucked by sucking the pore water in the soft ground G by these suction forces. Consolidate. This vacuum compaction can be performed with a larger suction force as much as the suction force due to the water level difference ΔH is applied, compared with the case where suction is performed only by the vacuum pump 23.
従来の真空圧密地盤改良工法によれば真空ポンプのみでは吸引力が不足する場合は、盛土による載荷を併用していたのに対し、本実施形態のようにサイフォン機能による吸引力を併用することにより、盛土による載荷を縮小したり省略できるため、使用資材・機材の節減や作業工期の短縮を期待することができる。また、従来の工法に比べて吸引力が増加するため、軟弱地盤が所定の強度に達するまでに要する地盤改良期間を短縮することができる。 According to the conventional vacuum consolidation ground improvement method, when the suction force is insufficient with only the vacuum pump, loading by embankment was used together, but by using the suction force by siphon function as in this embodiment Because loading due to embankment can be reduced or omitted, it can be expected to save materials and equipment and shorten the work period. In addition, since the suction force is increased as compared with the conventional construction method, the ground improvement period required for the soft ground to reach a predetermined strength can be shortened.
本実施形態においては、水平通水管２２内に気体が含まれる条件においても、サイフォンを機能させるためには、鉛直通水管２１内において水と気体が混合した気液２相流を形成させることが重要であり、上述のように、水平通水管２２の内径に対し鉛直通水管２１の内径を調整することが必要であり、好ましくは、鉛直通水管２１の内径は水平通水管２２の内径の５０％以下（水平通水管２２の内径が０．１ｍを超えるとき）または７０％以下（水平通水管２２の内径が０．１ｍ以下のとき）であり、また、必要に応じて、図７の鉛直通水管２１に図４（ａ）（ｂ）や図５の構成を適用でき、また、図７の真空圧密地盤改良システムＳＡに図３の吸引力発生装置の構成を適用できる。 In the present embodiment, a gas-liquid two-phase flow in which water and gas are mixed in the vertical water pipe 21 is formed in order to make the siphon function even under the condition that the horizontal water pipe 22 contains gas. As described above, it is necessary to adjust the inner diameter of the vertical water pipe 21 with respect to the inner diameter of the horizontal water pipe 22. Preferably, the inner diameter of the vertical water pipe 21 is 50 times the inner diameter of the horizontal water pipe 22. % Or less (when the inner diameter of the horizontal water pipe 22 exceeds 0.1 m) or 70% or less (when the inner diameter of the horizontal water pipe 22 is 0.1 m or less). 4 (a) and 4 (b) and FIG. 5 can be applied to the water flow pipe 21, and the structure of the suction force generator of FIG. 3 can be applied to the vacuum consolidation ground improvement system SA of FIG.
なお、揚水ポンプ２４は、揚程差１０ｍ以上の高揚程タイプが好ましく、密閉室２６を地中深く設置し、水位差ΔＨの確保のため密閉室２６内の水位面Ｈ１を地下水位面Ｈ０に対しより低くした場合でも、密閉室２６内の貯留水を排水できる。 The lift pump 24 is preferably a high head type with a head difference of 10 m or more, the sealed chamber 26 is installed deep in the ground, and the water level surface H1 in the sealed chamber 26 with respect to the ground water level surface H0 is secured to ensure the water level difference ΔH. Even if it is made lower, the stored water in the sealed chamber 26 can be drained.
次に、本発明を実施例により具体的に説明するが、本発明は本実施例に限定されるものではない。 EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited to a present Example.
図８に、本実施例においてサイフォン機能による吸引力を併用する真空減圧装置の効果を検証するために用いた実験装置を示す。この実験装置は真空ポンプを併用したものである。 FIG. 8 shows an experimental apparatus used for verifying the effect of the vacuum pressure reducing apparatus using the suction force by the siphon function in the present embodiment. This experimental apparatus uses a vacuum pump in combination.
図８の実験装置を用いて以下の手順で実験を行った。
ステップ１：排水用バルブ、空気量調整バルブ、水量調整バルブを閉じた後、注水用バルブを開いて注水し、水平管（円筒管）内および鉛直管（円筒管）内を水で飽和させる。
ステップ２：注水用バルブを閉じた後、排水用バルブのみを開き、密閉室内の水位が鉛直管の下端より５ｃｍ上になるまで排水する。
ステップ３：排水用バルブを閉じた後、真空ポンプを作動させる。このとき、 鉛直方向レベルの異なるステージ（Ｓｔ．）Ａ〜Ｅで水圧計を用いて、同時に水圧計測を開始する。
ステップ４：密閉室内の圧力が−６０ｋＰａまで減圧されたとき、空気量調整バルブ、水量調整バルブを開き、管内に水と空気を導く。
ステップ５：密閉室内の水位変化と、経過時間を計測し、水の流量および管内流速を算定する。
The experiment was performed by the following procedure using the experimental apparatus of FIG.
Step 1: After closing the drainage valve, the air amount adjustment valve, and the water amount adjustment valve, the water injection valve is opened to inject water, and the inside of the horizontal pipe (cylindrical pipe) and the vertical pipe (cylindrical pipe) is saturated with water.
Step 2: After closing the water injection valve, open only the drain valve and drain until the water level in the sealed chamber is 5 cm above the lower end of the vertical pipe.
Step 3: After closing the drain valve, the vacuum pump is activated. At this time, water pressure measurement is simultaneously started using a water pressure gauge in stages (St.) A to E having different vertical levels.
Step 4: When the pressure in the sealed chamber is reduced to -60 kPa, the air amount adjustment valve and the water amount adjustment valve are opened to introduce water and air into the pipe.
Step 5: Measure the water level change in the sealed chamber and the elapsed time, and calculate the water flow rate and the pipe flow velocity.
下記表１に示すように、鉛直管内を流れる流速を変化させながら、空気の混入がないケース１〜３と、空気の混入があるケース４〜６に対して実験を行った。ここで、鉛直管内の流速については、水量調整バルブの調整や径の異なる鉛直管の使用により、変化させた。ケース６が実施例である。なお、上述の式（１）を用いて評価される最大の気泡の上昇速度は、１．１ｍ／ｓである。 As shown in Table 1 below, experiments were performed on cases 1 to 3 in which no air was mixed and cases 4 to 6 in which air was mixed while changing the flow velocity flowing in the vertical pipe. Here, the flow velocity in the vertical pipe was changed by adjusting the water amount adjusting valve or using a vertical pipe having a different diameter. Case 6 is an example. It should be noted that the maximum bubble rising speed evaluated using the above formula (1) is 1.1 m / s.
実験結果
水を供給する前のステップ３における鉛直管・水平管内の負圧計測結果を図９に示す。水位差に従って鉛直管内に働く吸引力により、図８の最上部にあるＳｔ．ＤとＳｔ．Ｅでは、最下部にあるＳｔ．Ａに比べて、水位差に相当する２５ｋＰａ程度負圧が大きく作用することが確認できる。
Experimental results Fig. 9 shows the results of measuring the negative pressure in the vertical and horizontal pipes in Step 3 before supplying water. St. force at the top of FIG. D and St. In E, St. Compared to A, it can be confirmed that the negative pressure acts largely about 25 kPa corresponding to the water level difference.
また、実験開始後における鉛直管・水平管内の負圧計測結果について、最下部にあるＳｔ．Ａの圧力を基準とした各地点における圧力偏差分を図１０（ａ）〜（ｃ）と図１１（ａ）〜（ｃ）に示す。 In addition, regarding the negative pressure measurement results in the vertical and horizontal pipes after the start of the experiment, St. FIGS. 10A to 10C and FIGS. 11A to 11C show pressure deviations at each point with the pressure of A as a reference.
図１０（ａ）〜（ｃ）のように、ケース１〜３の空気が混入していないケースでは、すべてのケースで、サイフォンが機能し、鉛直管内に働く吸引力により、最上部にあるＳｔ．ＤとＳｔ．Ｅでは、最下部にあるＳｔ．Ａに比べて、水位差に相当する２５ｋＰａ程度負圧が大きく作用することが確認できる。このように、鉛直管の下部に比べて水平管部で負圧が増加することは、サイフォン機能によって吸引力が作用していることを示唆するものである。 As shown in FIGS. 10 (a) to 10 (c), in cases 1 to 3 where the air is not mixed, the siphon functions in all cases, and the uppermost St is applied by the suction force acting in the vertical pipe. . D and St. In E, St. Compared to A, it can be confirmed that the negative pressure acts largely about 25 kPa corresponding to the water level difference. Thus, an increase in the negative pressure in the horizontal pipe portion as compared with the lower portion of the vertical pipe suggests that the suction force is acting by the siphon function.
一方、図１１（ａ）〜（ｃ）のように、ケース４〜６の空気が混入するケースでは、サイフォンが確実に機能するのは、水平管の内径に対して鉛直管の内径を１／２に定め、気泡が浮力によって上昇する速度より流速を速くした条件のケース６のみであることがわかる。このとき、鉛直管内では、図２（ａ）に示すような気液２相流が形成され、空気が気泡として水に取り込まれながら一体的に流れる状況が観察された。気泡の上昇速度に比べて流速が十分でないケース４と５では、実験開始後しばらくの間、空気が排出されずに鉛直管内に蓄積されていき、最上部から最下部にわたって空気が占有するに至ると、最終的に図２（ｂ）に示すような水と空気が分離した流れが形成され、別々に排出されることが確認された。このような分離状況では、サイフォンが機能しないため、最上部にあるＳｔ．ＤとＳｔ．Ｅにおいて、負圧の増加は見られなかった。 On the other hand, as shown in FIGS. 11 (a) to 11 (c), in the case where the air in the cases 4 to 6 is mixed, the siphon functions reliably because the inner diameter of the vertical pipe is less than the inner diameter of the horizontal pipe. It can be seen that this is only case 6 where the flow velocity is higher than the speed at which the bubbles rise by buoyancy. At this time, a gas-liquid two-phase flow as shown in FIG. 2 (a) was formed in the vertical pipe, and it was observed that air flowed integrally while being taken into water as bubbles. In Cases 4 and 5, where the flow rate is not sufficient compared to the rising speed of the bubbles, the air is not exhausted for a while after starting the experiment and is accumulated in the vertical pipe, and the air occupies from the top to the bottom. Finally, it was confirmed that a flow in which water and air were separated as shown in FIG. 2B was formed and discharged separately. In such a separation situation, since the siphon does not function, the St. D and St. In E, no increase in negative pressure was observed.
以上の実験により、溶存酸素等の気化や水平管や鉛直管等の通水管の気密漏れ部から流入する気体の存在があるような条件においても、確実にサイフォンの吸引力を作用させるためには、鉛直管内で、浮力による気泡の上昇速度νa以上に流速νwを速くし、気液２相流を形成させることが重要であることを検証した。すなわち、サイフォンの吸引力を確実に発揮させるためには、鉛直管の内径を、上述の条件式（３）νw＞νaとなるように定めることが重要である。 From the above experiments, in order to ensure that the siphon suction force acts even under conditions where vaporization of dissolved oxygen or the like exists in the presence of gas flowing from the airtight leaking part of a water pipe such as a horizontal pipe or a vertical pipe. In the vertical pipe, it was verified that it is important to increase the flow velocity ν w above the bubble rising velocity ν a due to buoyancy and to form a gas-liquid two-phase flow. That is, it is important to determine the inner diameter of the vertical pipe so as to satisfy the above-described conditional expression (3) ν w > ν a in order to reliably exert the siphon suction force.
また、本実験では、図１２のように、負圧が高まると、溶存気体が気化する状況が観察され、また、−１００ｋＰａに達すると、水が沸騰し、完全に気化することが確認された。すなわち、本真空減圧装置によって作用させることのできる限界の負圧は、−１００ｋＰａである。 Further, in this experiment, as shown in FIG. 12, when the negative pressure increased, the situation where the dissolved gas vaporized was observed, and when it reached −100 kPa, it was confirmed that water boiled and completely vaporized. . That is, the limit negative pressure that can be applied by the vacuum decompression apparatus is −100 kPa.
以上のように本発明を実施するための形態及び実施例について説明したが、本発明はこれらに限定されるものではなく、本発明の技術的思想の範囲内で各種の変形が可能である。例えば、本発明による吸引力発生装置を真空圧密地盤改良システムに適用したが、これに限定されず、他の装置・システム・他の工法に適宜適用してよく、同様の効果を得ることができる。また、鉛直管、水平管は、円筒管以外であってもよく、例えば角筒管でもよい。 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, the suction force generator according to the present invention is applied to the vacuum consolidation ground improvement system, but is not limited to this, and may be applied as appropriate to other devices, systems, and other construction methods, and similar effects can be obtained. . Further, the vertical tube and the horizontal tube may be other than the cylindrical tube, for example, a rectangular tube.
本発明による吸引力発生装置によれば、水に気体が含まれる場合でもサイフォンの原理による吸引力を発生させることができるので、真空ポンプに頼らずにサイフォンの自然エネルギーを極力使用可能となり、電力等のコストを削減可能となる。 According to the suction force generating device of the present invention, even when gas is contained in water, the suction force based on the principle of siphon can be generated, so that the natural energy of siphon can be used as much as possible without relying on a vacuum pump, Etc. can be reduced.
本発明による真空圧密地盤改良工法によれば、サイフォン機能による吸引力を併用することで盛土による載荷の縮小・省略が可能となり、使用資材・機材の節減や作業工期の短縮を実現でき、また、従来の工法に比べて吸引力が増加するため、軟弱地盤が所定の強度に達するまでに要する地盤改良期間を短縮できる。 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. Since the suction force increases as compared with the conventional construction method, the ground improvement period required until the soft ground reaches a predetermined strength can be shortened.
１ 鉛直管（第１の管）
１ａ 鉛直管の下端
２ 水平管（第２の管）
２ａ 水平管の先端
３ 不透水棒
６ 突起体（付帯物）
７ 網状体（付帯物）
１１〜１３ 鉛直管
２０ 真空減圧装置
２１ 鉛直通水管
２２ 水平通水管
２３ 真空ポンプ
２４ 揚水ポンプ
２６ 密閉室
３１ 鉛直ドレーン材
ＳＡ 真空圧密地盤改良システム
Ｇ 軟弱地盤
Ｈ０ 地下水位面
Ｈ１ 密閉室内の水位面
ΔＨ 水位差
1 Vertical pipe (first pipe)
1a Lower end of vertical pipe 2 Horizontal pipe (second pipe)
2a End of horizontal pipe 3 Impervious stick 6 Projection (attachment)
7 Reticulated body (accessory)
11-13 Vertical pipe 20 Vacuum decompression device 21 Vertical water pipe 22 Horizontal water pipe 23 Vacuum pump 24 Pumping pump 26 Sealed chamber 31 Vertical drain material SA Vacuum consolidated ground improvement system G Soft ground H0 Ground water level surface H1 Water level surface ΔH in the sealed chamber Water level difference
Claims (6)
前記第１の管を複数本設け、
前記各第１の管の通水断面積が前記第２の管の通水断面積よりもそれぞれ小さくかつ互いに異なるように前記各第１の管を構成し、
前記第２の管に対し前記第１の管を切り替え可能に構成したことを特徴とする吸引力発生装置。 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 extending in the horizontal direction; and a lower end side of the first pipe; A suction force generator 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 between the tip of the two tubes,
Providing a plurality of the first tubes;
Each of the first pipes is configured such that the cross sectional area of each of the first pipes is smaller than and different from the cross sectional area of the second pipe;
A suction force generating device, wherein the first tube is switchable with respect to the second tube.
前記各第１の管の内径がそれぞれ異なることを特徴とする請求項１に記載の吸引力発生装置。 The first tube and the second tube are composed of cylindrical tubes,
The suction force generator according to claim 1 , wherein an inner diameter of each of the first tubes is different.
前記第１の管の通水断面積が前記第２の管の通水断面積よりも小さくなるように前記第１の管内に不透水棒を配置したことを特徴とする吸引力発生装置。 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 extending in the horizontal direction; and a lower end side of the first pipe; A suction force generator 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 between the tip of the two tubes,
A suction force generating device, wherein an impermeable rod is disposed in the first pipe so that a water flow cross-sectional area of the first pipe is smaller than a water flow cross-sectional area of the second pipe.
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| JP2009025758A JP5305957B2 (en) | 2009-02-06 | 2009-02-06 | Suction force generator and vacuum consolidation ground improvement method |
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| JP6886576B2 (en) * | 2017-02-24 | 2021-06-16 | 五洋建設株式会社 | Negative pressure generator for ground improvement |
| CN108691310A (en) * | 2018-06-21 | 2018-10-23 | 中国华电科工集团有限公司 | A kind of soft foundation discharge fixing system and method |
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| JP2656432B2 (en) * | 1993-02-23 | 1997-09-24 | 住友建設株式会社 | Liquefaction prevention method and liquefaction prevention drain hole |
| JP3656217B2 (en) * | 2000-12-13 | 2005-06-08 | 丸山工業株式会社 | Improvement method and equipment for soft ground |
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