JP6313533B2 - Buried tank and its construction method - Google Patents

Buried tank and its construction method Download PDF

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JP6313533B2
JP6313533B2 JP2012126240A JP2012126240A JP6313533B2 JP 6313533 B2 JP6313533 B2 JP 6313533B2 JP 2012126240 A JP2012126240 A JP 2012126240A JP 2012126240 A JP2012126240 A JP 2012126240A JP 6313533 B2 JP6313533 B2 JP 6313533B2
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tank
cylinder
guide frame
peripheral wall
outer peripheral
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JP2013249667A (en
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善明 玉田
善明 玉田
英樹 東崎
英樹 東崎
雅之 齊藤
雅之 齊藤
俊之 串田
俊之 串田
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玉田工業株式会社
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この発明は、ケーソン工法ないし井筒沈下工法と呼ばれる工法で構築される縦筒形（一般的には縦円筒形）のタンク及びその構築方法に関するもので、特に施工中における地下水の排水及び地盤の液状化対策に特徴がある上記タンク及び構築方法に関するものである。   TECHNICAL FIELD The present invention relates to a vertical cylinder (generally vertical cylindrical) tank constructed by a construction method called caisson method or well-cylinder subsidence method and a construction method thereof, and in particular, drainage of groundwater and liquid of ground during construction. The present invention relates to the tank and the construction method characterized by countermeasures for composting.

図４〜９を参照して、ケーソン工法ないし井筒沈下工法と呼ばれる従来工法を説明する。   With reference to FIGS. 4 to 9, a conventional method called a caisson method or a well subsidence method will be described.

まず、タンクを設置する地面を浅く掘削して、その底面を水平に均し、タンクの周寸法より若干大きな周寸法を備えたガイド枠２を設置する。縦円筒形のタンクの場合は、ガイド枠２はリング状となる。ガイド枠２は、Ｌ字のステム（縦棒）の部分を外周側にした倒立Ｌ形断面をしている。次に、このガイド枠２の上にタンクの周壁となる筒体１１を設置する。ガイド枠２や筒体１１は、通常、周方向に幾つかに分割した形状（円の場合は円弧形状）のものを工場で製作し、それらを現場で溶接して組み立てて一体化する。筒体１１の上下端付近には、タンクの底板１２及び頂板１３を溶接するための内フランジ１４、１５が設けられている。   First, the ground on which the tank is installed is excavated shallowly, the bottom surface thereof is leveled, and the guide frame 2 having a circumferential dimension slightly larger than the circumferential dimension of the tank is installed. In the case of a vertical cylindrical tank, the guide frame 2 has a ring shape. The guide frame 2 has an inverted L-shaped cross section with an L-shaped stem (vertical bar) portion on the outer peripheral side. Next, a cylindrical body 11 serving as a peripheral wall of the tank is installed on the guide frame 2. The guide frame 2 and the cylindrical body 11 are usually manufactured in a factory in a shape divided into several parts in the circumferential direction (arc shape in the case of a circle), and these are welded and assembled on site to be integrated. Inner flanges 14 and 15 for welding the bottom plate 12 and the top plate 13 of the tank are provided in the vicinity of the upper and lower ends of the cylindrical body 11.

次に、ガイド枠２が載置されている地面の当該ガイド枠の外周壁２１より内側の部分を掘削してゆく。この掘削は、例えば筒体１１の内側に吊り降ろした小型のパワーショベルと地上に設置した大型のパワーショベルを用いて行う。底面の掘削に従ってガイド枠２とその上に載置されている筒体１１（以下、「井筒」と言う。）は、沈下してゆく。地下水のある地盤では、掘削した地面から地下水が湧出するので、掘削した穴の底に置いた水中ポンプ６で地下水を汲み上げながら掘削を続ける。   Next, a portion inside the outer peripheral wall 21 of the guide frame on the ground on which the guide frame 2 is placed is excavated. This excavation is performed using, for example, a small excavator suspended inside the cylinder 11 and a large excavator installed on the ground. As the bottom surface is excavated, the guide frame 2 and the cylindrical body 11 (hereinafter referred to as “well tube”) placed thereon sink. In the ground with groundwater, groundwater springs from the excavated ground, so the excavation is continued while pumping up the groundwater with the submersible pump 6 placed at the bottom of the excavated hole.

筒体１１が設計した深さに達するまで井筒２、１１が沈下したら掘削を終了する。通常、タンクの底部には、タンク内の液体を汲み上げるためのピット３が設けられるので、このピットを設ける部分に上下が開口している筒のみからなるピット筒３１を、下側の内フランジ１４にボルト留めした仮ブラケット３４に上端を固定して取り付ける。ピット筒３１の下端には、後でピット底３２を取り付けるための内フランジやスタッドが設けられている。ピット底３２の位置（レベル）は、ガイド枠２の下端と同レベルか、若干上方である。   When the wells 2 and 11 sink until the cylindrical body 11 reaches the designed depth, the excavation is finished. Usually, since the pit 3 for pumping up the liquid in the tank is provided at the bottom of the tank, a pit cylinder 31 consisting only of a cylinder whose upper and lower sides are opened at the portion where the pit is provided is connected to the lower inner flange 14. The upper end is fixed and attached to the temporary bracket 34 bolted to. An inner flange and a stud for attaching the pit bottom 32 later are provided at the lower end of the pit cylinder 31. The position (level) of the pit bottom 32 is the same level as the lower end of the guide frame 2 or slightly above.

次に、掘削した穴の底面に砕石層５１を設ける。この砕石層５１の上面は、ピット筒３１の下部が埋設される高さとし、水中ポンプ６をピット筒３１内に設置して、地下水が砕石層５１の上面に達する前に水中ポンプ６で排水されるようにする。この状態で、砕石層５１の上に鉄筋を配置し、コンクリートを打設して鉄筋コンクリート層５２を形成する。一般的には、鉄筋コンクリート層５２の上に、上面が下側の内フランジ１４の上面と同一高さとなるように、アスファルト層５３を設け、その上にタンクの底板１２を吊り降ろし、その外周を内フランジ１４に溶接する。   Next, the crushed stone layer 51 is provided on the bottom surface of the excavated hole. The upper surface of the crushed stone layer 51 is set to a height at which the lower portion of the pit cylinder 31 is buried, and the submersible pump 6 is installed in the pit cylinder 31 so that the groundwater is drained by the submersible pump 6 before reaching the upper surface of the crushed stone layer 51. So that In this state, a reinforcing bar is placed on the crushed stone layer 51, and concrete is cast to form a reinforced concrete layer 52. In general, an asphalt layer 53 is provided on the reinforced concrete layer 52 so that the upper surface is flush with the upper surface of the lower inner flange 14, and the tank bottom plate 12 is suspended on the asphalt layer 53. Weld to the inner flange 14.

次にマンホール１６を予め取り付けた頂板１３を上側の内フランジ１５に載置して、その外周を当該内フランジ１５に溶接する。このようにしてタンク本体が完成したら、頂板１３の上面に鉄筋を組んでコンクリートを打設することによって、鉄筋コンクリート層５４を形成し、その上に土砂５５を埋め戻して、周囲の地表面と同一高さとする。埋設されたタンク１には、地下水の静水圧による浮力が作用するが、タンクの自重とその上に形成した鉄筋コンクリート層５４及び埋め戻し土砂層５５との上載荷重によってタンク１の浮上が防止される。   Next, the top plate 13 to which the manhole 16 is attached in advance is placed on the upper inner flange 15, and the outer periphery thereof is welded to the inner flange 15. When the tank main body is completed in this way, a reinforced concrete layer 54 is formed by laying a reinforcing bar on the top surface of the top plate 13 and placing concrete, and the earth and sand 55 is backfilled thereon to be the same as the surrounding ground surface. The height. Buoyancy due to the hydrostatic pressure of groundwater acts on the buried tank 1, but the tank 1 is prevented from rising due to the weight of the tank and the overload of the reinforced concrete layer 54 and the backfill soil layer 55 formed thereon. .

最後に、ピット筒３１の底に設けてある内フランジ上にシール材を介してピット底３２をスタッドにナットで固定して取り付け、下端をピット内に開口した吸水管やその他の必要な配管類を設けて、マンホール１６を蓋１７で閉鎖することにより、タンク１を完成する。   Finally, the pit bottom 32 is fixed to the stud with a nut attached to the stud on the inner flange provided at the bottom of the pit cylinder 31, and the lower end opens into the pit, and other necessary pipes. The tank 1 is completed by closing the manhole 16 with the lid 17.

特許第２７２５５１６号公報Japanese Patent No. 2725516

前述したように、地下水の静水圧によるタンク１の浮上は、タンクの自重とタンク上の上載荷重とによって抑えられている。上載荷重の重さは、タンク１に作用する浮力に対して十分な余裕を見た重さとしている。しかし、タンク１を埋設した地盤５に液状化が起ると、埋設地盤５内に大きな過剰間隙水圧が発生してタンク１を浮上させたり、地下水がタンク１の周壁に沿って流れて、タンク１の周囲から泥水が噴き上る現象などが発生する危険が指摘されている。   As described above, the rising of the tank 1 due to the hydrostatic pressure of the groundwater is suppressed by the weight of the tank and the load on the tank. The weight of the loading load is a weight with a sufficient margin for the buoyancy acting on the tank 1. However, when liquefaction occurs in the ground 5 in which the tank 1 is buried, a large excess pore water pressure is generated in the buried ground 5 to float the tank 1 or groundwater flows along the peripheral wall of the tank 1. It has been pointed out that there is a danger that muddy water will erupt from around 1.

また、地下水が湧出する地盤では、掘削している穴の底に水中ポンプ６を置いて常時排水を行わねばならない。しかし、パワーショベルで穴底を掘削するとき水中ポンプ６が邪魔になるため、水中ポンプ６の位置を移動しながら掘削をしなければならないという面倒がある。   In addition, on the ground where groundwater springs out, the submersible pump 6 must be placed at the bottom of the excavated hole to drain the water at all times. However, when excavating the bottom of the hole with a power shovel, the submersible pump 6 gets in the way, so that the excavation must be performed while moving the position of the submersible pump 6.

そこで、この発明は、地下水の湧出量が多い地盤において、井筒沈下工法による地下タンクの構築をより容易に行うことができるようにすること、及び地盤の液化現象による過剰間隙水圧によってタンクが浮上するのをより確実に防止することができる技術手段を得ることを課題としている。   Therefore, the present invention makes it possible to more easily construct an underground tank by a well subsidence method in the ground where there is a large amount of groundwater discharge, and the tank rises due to excess pore water pressure due to the ground liquefaction phenomenon. It is an object of the present invention to obtain technical means that can more reliably prevent this.

この発明では、井筒沈下工法による縦筒型のタンクの構築において、タンク１の周壁を形成する筒体１１とその筒体の下端に固定された当該筒体より周寸法の大きなガイド枠２とからなる井筒の沈下を開始する前に、筒体１１の周囲に複数本の排水パイプ４を立設し、各排水パイプの下端をガイド枠の外周壁２１の内側に開口すると共にその上端を排水ポンプ６に接続し、当該排水ポンプでガイド枠２の外周壁２１の内側周縁部の複数箇所から地下水を排水しながら井筒２、１１を沈下し、所定深さまで沈下したガイド枠２の内側に排水パイプ４の下端が埋設される深さで砕石層５１を施工し、その後、タンクの底板１２及び頂板１３をタンクの胴となる筒体１１に固定してタンク１を形成し、タンク１の上載荷重となるコンクリート層５４や埋め戻し土砂層５５を形成した後、排水ポンプ６を取り外して排水パイプ４の上端を地上に開口しておく、というものである。   In the present invention, in the construction of a vertical cylinder tank by the well subsidence method, the cylinder 11 forming the peripheral wall of the tank 1 and the guide frame 2 having a larger circumferential dimension than the cylinder fixed to the lower end of the cylinder. Before starting the sinking of the well, the plurality of drain pipes 4 are erected around the cylinder 11, the lower ends of the drain pipes are opened inside the outer peripheral wall 21 of the guide frame, and the upper ends thereof are drain pumps. 6, the wells 2 and 11 are submerged while draining groundwater from a plurality of locations on the inner peripheral edge of the outer peripheral wall 21 of the guide frame 2 with the drainage pump, and a drain pipe is placed inside the guide frame 2 that has subsided to a predetermined depth. The crushed stone layer 51 is constructed at a depth at which the lower end of 4 is buried, and then the tank bottom plate 12 and the top plate 13 are fixed to the cylinder 11 serving as a tank body, and the tank 1 is formed. Concrete layer 54 After the formation of the sand layer 55 backfill, keep open the top end of the drainage pipe 4 on the ground to remove the drain pump 6, is that.

この発明の方法により構築された縦型埋設タンク１は、タンクの周壁の外側に、タンクの周壁より外側に位置するタンク下端のガイド枠２の内側周縁部に下端が開口しかつ上端が地上に開口している複数本の排水パイプ４を備えている。この複数本の排水パイプ４が、地震などによりタンク１の設置地盤５が液状化した際に、タンク下の過剰間隙水圧を地上に放出するための通路となり、地盤の液状化に伴う過剰間隙水圧によるタンクの浮上や泥を含んだ地下水の噴出が防止される。   The vertical buried tank 1 constructed by the method of the present invention has a lower end opened at the inner peripheral edge of the guide frame 2 at the lower end of the tank located outside the peripheral wall of the tank and the upper end at the ground. A plurality of drainage pipes 4 are provided. When the ground 5 where the tank 1 is installed is liquefied due to an earthquake or the like, the plurality of drain pipes 4 serve as a passage for discharging excess pore water pressure below the tank to the ground, and excess pore water pressure associated with liquefaction of the ground. Prevents tank levitation and mud-containing groundwater eruption.

すなわち、この発明の縦型埋設タンクの構築方法は、タンク１を埋めるために掘削する穴の周縁を画定するガイド枠２の外周壁２１と当該ガイド枠の上面に載置固定される筒体１１との間に、下端が外周壁２１の内側に開口する複数本の排水パイプ４を立設し、当該排水パイプ４の上端に排水ポンプを接続する。そして、ガイド枠の外周壁２１より内側となる穴の底面を掘削して所定の深さまで井筒（ガイド枠と筒体）２、１１を沈下した後、排水パイプ４の下端が埋設される深さに砕石層５１を設けた後タンクの底板１２を取り付け、更にタンクの頂板１３及び上載荷重となるコンクリート層や埋め戻し土砂層５５を施工した後、排水ポンプ６を取り外して排水パイプ４の上端を開口状態としておくというものである。   That is, according to the construction method of the vertical buried tank of the present invention, the cylindrical body 11 placed and fixed on the outer peripheral wall 21 of the guide frame 2 that defines the periphery of the hole to be excavated to fill the tank 1 and the upper surface of the guide frame. A plurality of drainage pipes 4 whose lower ends open to the inside of the outer peripheral wall 21 are erected, and a drainage pump is connected to the upper end of the drainage pipe 4. And after excavating the bottom face of the hole inside the outer peripheral wall 21 of the guide frame to sink the wells (guide frame and cylinder) 2 and 11 to a predetermined depth, the depth at which the lower end of the drainage pipe 4 is buried After installing the crushed stone layer 51 on the tank, the bottom plate 12 of the tank is attached, and the top plate 13 of the tank and the concrete layer and the backfilling earth and sand layer 55 to be loaded are constructed, and then the drain pump 6 is removed and the upper end of the drain pipe 4 is attached. It is to make it open.

又この発明の埋設タンクは、外周壁２１を備えたガイド枠２と、このガイド枠２上に下縁を固定された筒体１１と、下端をガイド枠の外周壁２１の内側に開口させて筒体１１の外側に立設された複数本の排水パイプ４と、ガイド枠の外周壁２１の内側に排水パイプ４の下端が埋設される深さで形成された砕石層５１と、筒体１１の下端部に周縁を溶接されて砕石層５１の上方に位置する底板１２と、筒体１１の上端部に周縁を溶接された頂板１３と、この頂板上の上載荷重となるコンクリート層５４や埋め戻し土砂層５５とを備えている。   The buried tank according to the present invention has a guide frame 2 having an outer peripheral wall 21, a cylinder 11 having a lower edge fixed on the guide frame 2, and a lower end opened inside the outer peripheral wall 21 of the guide frame. A plurality of drainage pipes 4 erected on the outside of the cylinder 11, a crushed stone layer 51 formed at a depth at which the lower end of the drainage pipe 4 is embedded inside the outer peripheral wall 21 of the guide frame, and the cylinder 11 The bottom plate 12 is welded at its lower end to the upper side of the crushed stone layer 51, the top plate 13 is welded to the upper end of the cylinder 11, and the concrete layer 54 is buried as an overlay load on the top plate. And a return soil layer 55.

この発明では、穴の底面を掘削する際の排水のために穴底に水中ポンプを置いておく必要がないため、掘削作業、特にパワーショベルを使っての掘削作業が容易になる。また、井筒２、１１を所定深さに沈下させた後の砕石層５１やタンク下の鉄筋コンクリート層５２を形成する際における継続的な地下水の排水を容易に行うことができ、特に地下水の湧出量が多い場合の施工が容易になる。   In the present invention, it is not necessary to place a submersible pump at the bottom of the hole for draining when the bottom surface of the hole is excavated, and therefore excavation work, particularly excavation work using a power shovel, is facilitated. Moreover, continuous ground water can be easily drained when forming the crushed stone layer 51 and the reinforced concrete layer 52 under the tank after the wells 2 and 11 are submerged to a predetermined depth. When there is much, construction becomes easy.

また、タンク１の底に設けるピットとして、ピット底３２をピット筒３１に予め溶接した一体構造のピット３を取り付けるので、従来のように、地下水が流入してくるピット筒３１の底にピット底３２をシールを介してスタッドなどで固定するという面倒な作業が不要になる。従って、この発明により、地下水の湧出がある場所での井筒沈下工法による地下タンクの設置をより容易に行うこともできるという効果がある。   Further, as the pit provided at the bottom of the tank 1, the pit 3 having an integral structure in which the pit bottom 32 is pre-welded to the pit cylinder 31 is attached, so that the bottom of the pit cylinder 31 into which groundwater flows in is conventionally provided. The troublesome work of fixing 32 with a stud or the like through a seal becomes unnecessary. Therefore, according to the present invention, there is an effect that it is possible to more easily perform the installation of the underground tank by the well subsidence method in the place where the groundwater is discharged.

更に、タンク構築中の地下水の排水のために設けた複数本のパイプ４がタンク構築後も下端をタンク１の底面の外周複数箇所に開口した状態で残るため、地震等によりタンクの設置地盤が液状化したとき、タンク底部に発生するおそれのある過剰間隙水圧をこれらのパイプ４によって放出することが可能となり、地震に伴う液状化現象によってタンク１が浮上したり、タンク１の周囲から泥水が噴き上るという危険を防止することができるという効果がある。   Furthermore, since the plurality of pipes 4 provided for draining groundwater during the construction of the tank remain after the construction of the tank with the lower ends opened to a plurality of locations on the outer periphery of the bottom surface of the tank 1, When liquefied, the excess pore water pressure that may be generated at the bottom of the tank can be released by these pipes 4, and the tank 1 rises due to the liquefaction phenomenon accompanying the earthquake, or mud water is generated around the tank 1. There is an effect that it is possible to prevent the danger of spraying up.

この発明によるタンクの構築手順を示す第１の縦断面図1st longitudinal cross-sectional view which shows the construction procedure of the tank by this invention 同第２の縦断面図Second longitudinal sectional view この発明の実施例のタンクの縦断面図Longitudinal sectional view of a tank according to an embodiment of the present invention 従来のタンクの構築手順を示す第１の縦断面図1st longitudinal cross-sectional view which shows the construction procedure of the conventional tank 同第２の縦断面図Second longitudinal sectional view 同第３の縦断面図Third longitudinal sectional view 同第４の縦断面図Fourth vertical sectional view 同第５の縦断面図Fifth longitudinal section 従来構造のタンクの縦断面図Longitudinal section of a conventional tank

以下、図１ないし３を参照して、この発明の井筒沈下工法と、当該工法によって構築された埋設タンクについて具体的に説明する。以下の工法の説明においては、図４〜９で説明した従来工法と異なる所のみを説明する。   Hereinafter, with reference to FIG. 1 thru | or 3, the well subsidence construction method of this invention and the buried tank constructed | assembled by the said construction method are demonstrated concretely. In the following description of the construction method, only the differences from the conventional construction method described with reference to FIGS.

実施例のガイド枠２は、従来と同様に断面は倒立Ｌ形であるが、筒体１１を設置する位置とガイド枠の外周壁２１との間の位置に、一般的には周方向に等間隔に、適当数の貫通孔２２が設けられ、上端に管用テーパ雌ねじを設けたソケット４１が各貫通孔２２に予め溶接してある。ソケット４１の下端は開口しており、その開口高さはガイド筒の外周壁２１の下縁より若干高い高さである。   The guide frame 2 of the embodiment has an inverted L-shaped cross section as in the prior art, but is positioned between the position where the cylinder 11 is installed and the outer peripheral wall 21 of the guide frame, generally in the circumferential direction, etc. A suitable number of through holes 22 are provided at intervals, and a socket 41 having a pipe taper female screw at the upper end is welded to each through hole 22 in advance. The lower end of the socket 41 is open, and the opening height is slightly higher than the lower edge of the outer peripheral wall 21 of the guide cylinder.

浅く掘削した穴の底面に上記構造でソケット４１を溶接したガイド枠２を組み立て、従来と同様な構造の筒体１１を、ソケット４１より内側の位置にして、ガイド枠２上に載置固定する。そして、下端に管用テーパ雄ねじを設けた複数本の排水パイプ４を、それぞれのソケット４１に下端を接続して、筒体１１に沿わせた状態で立設する。   The guide frame 2 in which the socket 41 is welded with the above structure is assembled to the bottom surface of the hole excavated shallowly, and the cylindrical body 11 having the same structure as the conventional one is placed and fixed on the guide frame 2 at a position inside the socket 41. . Then, a plurality of drain pipes 4 provided with pipe taper male threads at the lower ends are erected in a state where the lower ends are connected to the respective sockets 41 and along the cylindrical body 11.

立設した排水パイプ４と筒体１１の間に形成される隙間には、スペーサ４４を適宜挿入して、側方からの土圧によるパイプ４の曲がりを防止する。排水パイプ４は、グラスファイバーを混入したエポキシ樹脂などで、スペーサ４４を挟んで筒体１１に固定しておくことができる。排水パイプ４の上端には、エルボ４２やチーズ４３を設けて、フレキシブルホース６１などにより排水ポンプ６の吸入口に接続する。この場合、複数本の排水パイプの上端を１本にまとめて１台の排水ポンプ６に接続してやればよい。   A spacer 44 is appropriately inserted into a gap formed between the standing drain pipe 4 and the cylinder 11 to prevent the pipe 4 from being bent due to earth pressure from the side. The drainage pipe 4 can be fixed to the cylindrical body 11 with a spacer 44 sandwiched by an epoxy resin mixed with glass fiber. An elbow 42 and cheese 43 are provided at the upper end of the drainage pipe 4 and connected to the suction port of the drainage pump 6 by a flexible hose 61 or the like. In this case, the upper ends of the plurality of drain pipes may be combined into one and connected to one drain pump 6.

この状態で穴の底を掘削して井筒２、１１を沈下させる。この掘削のとき、穴の底に水中ポンプが置かれていないので、パワーショベルによる穴の底面の掘削作業が容易である。穴の底面に地下水が湧出してきたら、排水ポンプ６を運転して複数本の排水パイプ４を通してガイド枠の外周壁２１の内側の複数箇所に開口しているソケット４１の下端から地下水を吸引して排水する。ソケット４１の下端は、倒立Ｌ形断面のガイド枠２の外周壁２１の内側に開口しているので、ガイド枠２の外側から穴の底面へと流入してくる地下水を有効に排水することができる。   In this state, the bottom of the hole is excavated to sink the wells 2 and 11. At the time of this excavation, since the submersible pump is not placed at the bottom of the hole, excavation work on the bottom surface of the hole by a power shovel is easy. When groundwater comes out to the bottom of the hole, the drainage pump 6 is operated and the groundwater is sucked through the plurality of drainage pipes 4 from the lower ends of the sockets 41 opened at a plurality of locations inside the outer peripheral wall 21 of the guide frame. Drain. Since the lower end of the socket 41 opens to the inside of the outer peripheral wall 21 of the guide frame 2 having an inverted L-shaped cross section, groundwater flowing from the outside of the guide frame 2 to the bottom of the hole can be effectively drained. it can.

このようにして地下水を排水しながら所定の深さまで井筒２、１１を沈下させたら、ピット底を一体に溶接した逆ハット形のピット３を設置し、ソケット４１の下端が埋設される高さに砕石層５１を形成する。ピット３は、予めピット底３２を溶接した逆ハット形の部品を準備して、井筒２、１１を沈下させた後に取り付ける。   When the wells 2 and 11 are submerged to a predetermined depth while draining groundwater in this way, the inverted hat-shaped pit 3 in which the pit bottom is integrally welded is installed and the lower end of the socket 41 is buried at a height. A crushed stone layer 51 is formed. The pit 3 is attached after preparing a reverse hat-shaped part welded to the pit bottom 32 in advance and sinking the wells 2 and 11.

穴内に湧出する地下水は、砕石の間の空隙を通って複数のソケット４１の下端から継続して排水される。この状態で、従来と同様に鉄筋コンクリート層５２、アスファルト層５３及びタンクの底板１２を施工し、更にタンクの頂板１３、上載荷重となる鉄筋コンクリート層５４及び埋め戻し土砂層５５を従来と同様な手順で施工する。これらの施工の間、タンク１の底部に湧出する地下水は、複数本の排水パイプ４から継続して排水されるので、タンク１が浮上することはない。   The groundwater that springs into the hole is continuously drained from the lower ends of the plurality of sockets 41 through the gaps between the crushed stones. In this state, the reinforced concrete layer 52, the asphalt layer 53 and the tank bottom plate 12 are constructed in the same manner as in the prior art, and the top plate 13 of the tank, the reinforced concrete layer 54 and the backfill earth and sand layer 55 serving as an overload are processed in the same procedure as before. Install. During these constructions, the groundwater that flows out to the bottom of the tank 1 is continuously drained from the plurality of drain pipes 4, so that the tank 1 does not rise.

排水ポンプ６は、鉄筋コンクリート層５４及び埋め戻し土砂層５５を形成した後、すなわちタンク１に上載荷重がかかった後、取り外してやればよい。タンク底のピット３は予めピット底を溶接して一体化したものが取り付けられるので、上載荷重をかけた後でピット筒にピット底を取り付けるという作業は不要である。   The drainage pump 6 may be removed after the reinforced concrete layer 54 and the backfill earth and sand layer 55 are formed, that is, after an overload is applied to the tank 1. Since the pit 3 at the bottom of the tank is integrated by previously welding the pit bottom, the work of attaching the pit bottom to the pit cylinder after applying an overload is unnecessary.

このようにして構築されたこの発明の埋設タンクは、図３に示すように、タンク１の側壁に沿って下端がガイド枠２のすぐ内側に開口している複数本の排水パイプ４が取り付けられて、その上端が地表に開口しているという点、及び、ピット底３２のピット筒３１への固定構造が従来構造のタンクと異なっている。複数本の排水パイプ４には、周囲の地盤５の地下水と同じレベルまで地下水が流入している。   As shown in FIG. 3, the buried tank of the present invention constructed in this way is attached with a plurality of drain pipes 4 whose lower ends are opened just inside the guide frame 2 along the side wall of the tank 1. Thus, the upper end of the pit bottom 32 is fixed to the pit cylinder 31 in that the upper end of the pit bottom 32 is open to the ground surface. The groundwater flows into the plurality of drainage pipes 4 to the same level as the groundwater of the surrounding ground 5.

このように設置されたタンク１の地盤５に地震等による液状化が起こったとき、タンク１の底部に生じた過剰間隙水圧は、複数本の排水パイプ４を通って地表に放出される。すなわち、井筒構築時の地下水の排水のために設けたパイプ４がタンクが構築された後も地中の過剰な水圧を放出するための放出路として機能し、地震などによりタンクの設置地盤が液状化したときに、タンク１が浮き上がったり、タンクの周囲から泥水が噴出するという事態を防止できるのである。   When liquefaction due to an earthquake or the like occurs in the ground 5 of the tank 1 installed in this way, excess pore water pressure generated at the bottom of the tank 1 is released to the ground surface through the plurality of drain pipes 4. That is, after the tank is constructed, the pipe 4 provided for draining groundwater at the time of the construction of the well functions as a discharge path for releasing excessive water pressure in the ground. Therefore, it is possible to prevent the tank 1 from floating or the muddy water from being ejected from the surroundings of the tank.

１ 縦型埋設タンク
２ ガイド枠
４ 排水パイプ
５ 地盤
６ 排水ポンプ
11 筒体
12 タンクの底板
13 タンクの頂板
21 外周壁
51 砕石層
54 コンクリート層
55 埋め戻し土砂層 1 Vertical tank 2 Guide frame 4 Drain pipe 5 Ground 6 Drain pump
11 Tube
12 Tank bottom plate
13 Tank top plate
21 outer wall
51 Crushed stone layer
54 Concrete layer
55 Backfill soil layer

Claims (2)

縦筒型の埋設タンクの構築方法において、埋設する筒体の下縁に当該筒体より周寸法の大きなガイド枠を固定し、前記筒体の外側でかつ
掘削する穴の周縁を画定する前記ガイド枠の外周壁より内側でかつ前記筒体の外側である前記外周壁と前記筒体との間に、下端が前記外周壁の内側に開口する複数本の排水パイプを前記筒体に沿わせた状態で立設し、当該排水パイプの上端に排水ポンプを接続し、前記外周壁より内側となる穴の底面を掘削して所定の深さまで前記ガイド枠及び筒体を沈下した後、前記排水パイプの下端が埋設される深さに砕石層を設け、タンクの底板、頂板及び上載荷重となる層を形成し、前記排水ポンプを取り外して排水パイプの上端を開口状態とすることを特徴とする、埋設タンクの構築方法。 In the construction method of the vertical cylinder type buried tank, a guide frame having a larger circumferential dimension than the cylinder is fixed to the lower edge of the cylinder to be buried, and the periphery of the hole to be drilled is formed outside the cylinder. A plurality of drainage pipes whose lower ends are opened to the inside of the outer peripheral wall between the outer peripheral wall and the cylindrical body, which are inside the outer peripheral wall of the guide frame to be defined and outside the cylindrical body. The drainage pipe is connected to the upper end of the drainage pipe, and the bottom of the hole inside the outer peripheral wall is excavated to sink the guide frame and the cylinder body to a predetermined depth. The crushed stone layer is provided at a depth at which the lower end of the drainage pipe is embedded, the bottom plate, the top plate and the layer serving as an overload are formed, and the drainage pump is removed to make the upper end of the drainage pipe open. A method for constructing a buried tank. 外周壁を備えたガイド枠と、このガイド枠より周寸法の小さい筒体であって当該ガイド枠上に下縁を固定された縦筒型の筒体と、下端を前記外周壁の内側に開口させて前記筒体の外側でかつ前記外周壁より内側である前記外周壁と前記筒体との間に前記筒体に沿わせた状態で立設された複数本の排水パイプと、前記外周壁の内側に前記排水パイプの下端が埋設される深さで形成された砕石層と、前記筒体の下端部に周縁を溶接されて当該砕石層の上方に位置する底板と、前記筒体の上端部に周縁を溶接された頂板と、この頂板上の上載荷重となる層とを備えている、埋設タンク。 A guide frame having an outer peripheral wall, opening a vertical tubular cylindrical body which is fixed to the lower edge to the guide frame on a small cylindrical body having a circumferential dimension than the guide frame, a lower end inside the outer peripheral wall A plurality of drainage pipes erected in a state along the cylinder between the outer wall and the cylinder outside the cylinder and inside the outer wall; and the outer wall A crushed stone layer formed at a depth at which the lower end of the drainage pipe is embedded inside, a bottom plate that is welded to the lower end of the cylindrical body and located above the crushed stone layer, and an upper end of the cylindrical body A buried tank comprising a top plate whose periphery is welded to a portion and a layer serving as an overload on the top plate.
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