JP5764245B2 - Construction method of underground structure and underground structure - Google Patents

Description

  The present invention relates to an underground structure construction method and an underground structure.

  When constructing an underground structure by the open-cut method, the frame is often a concrete structure (RC structure, SRC structure, etc.) and the concrete is cast in place so that it can flexibly respond to the situation at the site (for example, patent documents) 1 and 2).

  The reverse winding method (reverse driving method) disclosed in Patent Documents 1 and 2 is the construction of a concrete frame (top plate, mid-floor plate, beam, etc.) that also serves as a retaining ring support, and then the ground below the concrete frame After that, the construction method is to construct side walls and bottom slabs of the concrete structure. In addition to the underground construction in parallel with the underground construction in the basement, the underground structure is directly under the road or railway in service. Used when building things.

JP 2001-193082 A Japanese Patent Laid-Open No. 11-6164

  In concrete placement work, there is a concern about noise and vibration caused by agitators (concrete mixer trucks) and vibrators. In areas where houses and commercial facilities are densely populated, due to requests from neighboring residents and owners, The placement time zone may be restricted. If the underground structure is large-scale, the amount of concrete used will be enormous, so if the placement time zone is limited, the process may be lengthened.

  In addition, the reverse winding method (reverse casting method) requires the assembly of side bars and floor slab reinforcing bars and formwork under the concrete frame that also serves as the retaining support for the piles. In addition, there is a risk that it takes time to assemble the rebar and formwork because the work overhead is limited by the presence of the mountain retaining work and the large lifting machine cannot be used below the mountain retaining work. There is.

  From such a viewpoint, the present invention has an object to provide a construction method of an underground structure suitable for construction under a situation where there is a restriction on a concrete placement time zone and a work empty space, An object is to provide an underground structure capable of reducing the amount of concrete used.

  The construction method of an underground structure according to the present invention includes a frame building process for forming a concrete frame, an excavation process for digging the ground below the concrete frame to a floor surface, and a plurality of steels on the floor surface. A steel floor slab construction step of forming a floor slab portion by arranging the steel segments in parallel and joining the steel segments adjacent to each other.

In short, the present invention forms a concrete frame (for example, a top plate, an intermediate floor plate, a beam, etc.) that becomes a part of the main frame, digs down the ground below the concrete frame, and then below the concrete frame. A plurality of steel segments are juxtaposed on the side, and the adjacent steel segments are joined together to form a floor slab portion that is another part of the main housing.
The concrete frame is formed of a reinforced concrete structure, a steel reinforced concrete structure, a fiber reinforced concrete structure, or the like.

  According to the present invention, it is possible to reduce the quantity of concrete, formwork, reinforcing bars, etc., compared to the case where the entire structure of the main frame is a concrete structure. Even under circumstances, or even in the case of a work head that cannot use a large lifting machine, the construction period is unlikely to be prolonged.

  An underground structure according to the present invention is an underground structure constructed by an open-cut method for digging the ground to a floor surface, and a steel shell formed between a concrete frame and the concrete frame and the floor surface. The steel shell frame has a plurality of steel segments arranged side by side on the floored surface.

  According to the underground structure according to the present invention, since a plurality of steel segments are used, it is possible to reduce the amount of concrete used and, in turn, reduce the number of reinforcing bars and formwork. Become. The open-cut method includes a reverse winding method in which the concrete frame is first constructed, and a forward winding method in which the steel shell frame is first constructed.

  According to the construction method of an underground structure according to the present invention, the number of concrete, formwork, reinforcing bars, and the like can be reduced as compared with the case where the entire structure of the main structure is a concrete structure. Even in situations where there are restrictions on time and work heads, it is difficult to prolong the construction period.

  Moreover, according to the underground structure which concerns on this invention, it becomes possible to reduce the usage-amount of concrete.

It is a cross-sectional view of an underground structure according to an embodiment of the present invention. It is a bar arrangement diagram of an upper concrete frame. It is a steel arrangement figure of an upper concrete frame. It is a fracture perspective view of an underground structure concerning an embodiment of the present invention. (A) is a plan view of a steel segment for floor slabs and a steel segment for corners, (b) is a cross-sectional view, and (c) is a cross-sectional view taken along line X1-X1 of (a). (A) is a side view of the steel segment for a side wall, (b) is X2-X2 sectional drawing of (a). It is a perspective view which shows the reinforcing bar and steel shell frame of an upper concrete frame. It is a side view which shows the junction part of an upper concrete frame and a steel shell frame. It is X3-X3 sectional drawing of FIG. It is X4-X4 sectional drawing of FIG. (A) is a reinforcement arrangement | positioning of a lower concrete frame, (b) is X5-X5 sectional drawing of (a). It is a perspective view which shows the reinforcement steel material and steel shell frame of a lower concrete frame. (A) is a cross-sectional view which shows a primary excavation process, (b) is a cross-sectional view which shows a 1st frame construction process. (A) is a cross-sectional view showing a process following (b) of FIG. 13, and (b) is a cross-sectional view showing a secondary excavation process. (A) And (b) is a cross-sectional view which shows a 2nd housing construction process. (A)-(d) is an expanded cross-sectional view which shows the construction procedure of the junction part of an upper concrete frame and a steel shell frame. (A) And (b) is a cross-sectional view which shows a 3rd housing construction process. (A) is a side view showing the case where the segments are assembled, and (b) is a side view showing the case where the segments are assembled in a staggered manner.

  As shown in FIG. 1, the underground structure according to the embodiment of the present invention is a multi-story culvert constructed by an open-cut method, and an upper concrete frame A that also serves as a mountain retaining support and a lower side of the upper concrete frame A Two steel shell housings B, B, a lower concrete housing C formed between the steel shell housings B, B, and a column D formed between the upper concrete housing A and the lower concrete housing C. And.

<Upper concrete frame A>
The upper concrete frame A is a permanent frame designed to withstand soil water pressure and overload, but the steel shell frame B, the lower concrete frame C, and the support column D except for the joint with the steel shell frame B. It is constructed in advance, and functions as a mountain retaining support when digging between the mountain walls W. The upper concrete frame A of the present embodiment includes a top plate portion A1, a side wall portion A2 along the mountain retaining wall W, and a vertical beam portion A3 extending in the longitudinal direction.

  The upper concrete frame A has a steel frame reinforced concrete structure (SRC structure), and is composed of cast-in-place concrete and reinforcing steel materials such as steel frames 11 to 13 and reinforcing bars (not shown). In the present embodiment, in addition to the transverse steel frame 11, the side wall core steel frame 12, the longitudinal steel frame 13, etc., as shown in FIG. 2, the slab main bar 14, the side wall main bar 15, the vertical beam main bar 16, the shear reinforcement bar 17, the hunch bar 18, etc. The concrete is reinforced by. Of course, the upper concrete frame A may be precast.

  As shown in FIG. 3, a plurality of transverse steel frames 11 are arranged in parallel at intervals in the front-rear direction (longitudinal direction). In addition, illustration of a reinforcing bar is abbreviate | omitted in FIG. Each transverse steel frame 11 is arranged so that the material axis direction is the horizontal direction (left-right direction). The transverse steel frame 11 of the present embodiment is made of an H-shaped steel, but may be changed to an I-shaped steel or a grooved steel.

  Adjacent transverse steel frames 11, 11 are connected by a plurality of connecting members 11a, 11a,. In addition, the edge part of the connection material 11a is connected to the stiffener of the crossing steel frame 11. FIG. As shown in FIG. 2, the end of the transverse steel frame 11 is placed on a bracket W2 provided on the core material W1 of the mountain retaining wall W, and the end surface of the transverse steel frame 11 and the inner wall surface of the mountain retaining wall W are A support member 11b is interposed therebetween.

  The side wall core steel frame 12 is a reinforcing steel material disposed in the side wall portion A2, and is disposed such that the material axis direction is the vertical direction. The upper end part of the side wall core steel frame 12 is joined to the lower surface of the end part of the transverse steel frame 11. Triangular reinforcing ribs 12 a are arranged at the inner corners of the joint between the transverse steel frame 11 and the side wall core steel frame 12. The side wall core steel frame 12 of the present embodiment is made of H-section steel, but may be changed to I-section steel or groove-section steel.

  The longitudinal steel frame 13 is a reinforcing steel material disposed in the upper half portion of the longitudinal beam portion A3, and is disposed such that the material axis direction is the longitudinal direction (see FIG. 3). The end of the longitudinal steel frame 13 is connected to a bracket protruding from the web of the transverse steel frame 11. Although the longitudinal steel frame 13 of this embodiment consists of channel steel, you may change into H-section steel, I-section steel, angle steel, etc.

  The slab main bar 14 is a reinforcing steel material that is arranged along the upper surface and the lower surface of the top plate portion A1, and is arranged so that the longitudinal direction is the horizontal direction. The slab main bar 14 penetrates the vertical beam part A3, and both ends of the slab main bar 14 are fixed to the concrete of the side wall parts A2 and A2.

  The side wall main reinforcement 15 is a reinforcing steel material arranged along the outer wall surface (wall surface on the mountain retaining wall W side) and the inner wall surface (wall surface on the inner sky side) of the side wall portion A2, so that the longitudinal direction becomes the vertical direction. Is arranged. In addition, the side wall main reinforcement 15 has entered the steel shell frame B.

  The longitudinal beam main reinforcing bars 16 are reinforcing steel members arranged along the upper surface and the lower surface of the longitudinal beam portion A3, and are arranged so that the longitudinal direction is the longitudinal direction.

  The shear reinforcing bar 17 is a reinforcing steel material arranged in a direction intersecting with the slab main bar 14 or the side wall main bar 15.

  The haunch bar 18 is a reinforcing steel material arranged in the haunch part, and the upper half of the haunch bar 18 is fixed to the concrete of the top plate portion A1.

<Steel shell B>
Steel shell housings B and B shown in FIG. 1 are permanent housings designed to withstand soil water pressure and overload. Both steel shell frames B, B are formed on both sides of the lower concrete frame C, and are opposed to each other with the columns D, D interposed therebetween. Each steel shell frame B has a floor slab portion B1 having a steel shell structure along the floor surface T2 and a side wall portion B2 having a steel shell structure along the mountain retaining wall W, and has an L shape in cross section. Yes.

  The floor slab portion B1 constitutes a part of the floor (inner floor slab) of the first basement floor, and is joined to the floor slab portion C1 of the lower concrete frame C which is the remaining part of the intermediate floor slab (floor slab) Junction J2). Moreover, side wall part B2 comprises a part of side wall of the 1st basement floor, and is joined to side wall part A2 of the upper concrete frame A (side wall joint part J1). The detailed structure of the joints J1 and J2 will be described later.

  As shown in FIG. 4, the steel shell frame B of the present embodiment includes two types of floor slab steel segments 20 and 30, corner steel segments 40, and two types of side wall steel segments 50. , 60. That is, the steel shell frame B is formed of a plurality of steel segments (floor slab steel segments 20 and 30, corner steel segments 40 and side wall steel segments 50 and 60).

In the following description, an L-shaped unit composed of five steel segments 20, 30, 40, 50, 60 is referred to as a “ring” following the shield tunnel. A joint portion (joint portion) between steel segments belonging to the same ring is referred to as a “segment joint”, and a joint portion (joint portion) between rings adjacent in the longitudinal direction is referred to as a “ring joint”.
Further, “front / rear / left / right” is based on the state of FIG.

  The floor slab steel segments 20 and 30, the corner steel segments 40 and the side wall steel segments 50 and 60 are arranged side by side so as to be in a potato assembly state, and the segment joints are continuous in the longitudinal direction. ing. That is, the position of the segment joint of one ring coincides with the position of the segment joint of another adjacent ring.

  The first floor slab segment 20 is a normal steel segment in which other steel segments are arranged on the front, rear, left and right sides thereof, and has a bottomed box shape with an open top surface. As shown in (a) and (b) of FIG. 5, the steel segment 20 for floor slab includes a skin plate 21, a pair of front and rear main girder plates 22 and 22, a pair of left and right joint plates 23 and 23, A plurality of vertical ribs 24, 24,... Provided between the main girder plates 22, 22. The floor slab steel segment 20 is joined to two steel segments (second floor slab steel segment 30 and corner steel segment 40) belonging to the same ring via each joint plate 23. Then, it is joined to the steel slab segments 20 belonging to other adjacent rings via the main girder plates 22. In addition, although illustration is abbreviate | omitted, the sealing material is affixed on the outer surface of the main girder plate 22 and the joint plate 23. FIG.

  The skin plate 21 is an outer shell (bottom) of the steel segment 20 for floor slab, and is made of a steel plate having a rectangular shape in plan view.

  The main girder plate 22 is erected on the front edge and the rear edge of the skin plate 21, and is abutted against the main girder plate 22 of another floor slab steel segment 20 adjacent in the longitudinal direction. The main girder plate 22 is inserted with a ring joint bolt b1.

  The joint plate 23 includes a water-stop end plate 23a erected on the skin plate 21, and structural reinforcing plates 23b and 23b disposed on the front and rear edges of the end plate 23a. The end face plate 23a is abutted against a joint plate of another segment adjacent in the same ring. The end face plate 23 a is fixed to the skin plate 21 and the main girder plates 22 and 22. The reinforcing plate 23b is disposed on the left and right edges of the main girder plate 21, and is fixed to the inner surfaces of the main girder plate 21 and the end face plate 23a. A segment joint bolt b2 is inserted through the end face plate 23a and the reinforcing plate 23b. An axial force equivalent to 75% of the yield axial force of the bolt b2 is introduced to the bolt b2 as an initial introduction axial force.

  Note that, when a force that causes a mesh opening is applied to the segment joint, load transmission between the main beam plate 22 and the bolt b2 is mainly performed via the reinforcing plate 23b. Since the portion exceeding the fulcrum of the “leverage reaction force” (portion only of the end face plate 23a) does not contribute to the load transmission, the end face plate 23a can be thinned, and thus the joint structure can be rationalized. Can do.

  The vertical ribs 24 are arranged in parallel with the joint plate 23. The vertical ribs 24 are erected on the skin plate 21 and fixed to the skin plate 21 and the main girder plates 22 and 22.

  As shown in FIG. 4, the second steel segment 30 for floor slab is a boundary installation type steel installed at the boundary portion between the floor slab portion B1 of the steel shell frame B and the floor slab portion C1 of the lower concrete C. A bottomed box-shaped main body 3A having an open top surface and a pair of embedded main girders 3B and 3B protruding from the main body 3A.

  As shown in FIGS. 5A and 5B, the main body 3A includes a skin plate 31, main girder plates 32 and 32, a joint plate 33, vertical ribs 34, a boundary plate 35, reinforcing ribs 36, and the like. I have. The main body portion 3A is joined to a normal type floor slab steel segment 20 belonging to the same ring via a joint plate 33, and is connected to a boundary installation type belonging to another adjacent ring via a main girder plate 32. It is joined to the main body 3A of the steel segment 30 for floor slab. Further, although not shown, a sealing material is continuously attached to the outer surfaces of the main beam 32, the joint plate 33 and the boundary plate 35. In addition, the sealing material stuck to the boundary plate 35 is disposed below the embedded main girders 3B and 3B.

The skin plate 31, the main girder plates 32 and 32, the joint plate 33, and the vertical rib 34 have the same configuration as that of the first floor slab steel segment 20.
That is, the skin plate 31 is an outer shell (bottom) of the main body 3 </ b> A, and the main girder plate 32 is erected on the front and rear edges of the skin plate 31. Further, the joint plate 33 includes a water stop end plate 33a erected on the skin plate 31, and structural reinforcing plates 33b and 33b disposed on the front and rear edges of the end plate 33a. The vertical ribs 34 are arranged in parallel with the joint plate 33.

  The boundary plate 35 is located on the opposite side of the joint plate 33 with the vertical rib 34 interposed therebetween, and connects the side edges of the main girder plates 32 and 32 on the embedded main girder 3B side. The boundary plate 35 of the present embodiment is made of a single steel plate having a thickness equivalent to that of the reinforcing plate 33b, and is fixed to the skin plate 31 and the main girder plates 32, 32. In this embodiment, since the segments are “assembled”, the boundary plates 35, 35,... Are aligned on a straight line.

  The reinforcing rib 36 is fixed to the inner corner of the joint between the main girder plate 32 and the boundary plate 35. In the present embodiment, two upper and lower reinforcing ribs 36 are disposed per one inner corner (see FIG. 5B).

  The embedded main girders 3B and 3B are arranged in parallel and face each other with the concrete placing space 3C interposed therebetween. It should be noted that skin plates and cover plates are not fixed to the upper and lower portions of the embedded main girders 3B and 3B, and the upper and lower portions of the concrete placing space 3C are open. Each embedded main beam 3B is joined to the embedded main beam 3B of another adjacent ring. As shown in FIG. 5B, the embedded main girder 3B projects from the main body 3A in a cantilever shape. The height of the embedded main girder 3B is smaller than that of the main girder plate 32, and the upper edge of the embedded main girder 3B is located one step lower than the upper edge of the main body 3A. The lower edge is located one level higher than the lower edge of the main body 3A.

  The embedded main girder 3 </ b> B of the present embodiment has rigidity equivalent to that of the main girder plate 32, and includes an overhang plate 37 and flanges 38 and 38 attached to the overhang plate 37.

  The overhang plate 37 is located on the extension of the main girder plate 32 as shown in FIG. The overhanging plate 37 is an extension of the main girder plate 32 and has the same thickness as the main girder plate 32. The main girder plate 32 and the overhanging plate 37 of this embodiment are cut from the same steel plate, and both are continuous without a break.

  The overhang plate 37 is abutted against the overhang plate 37 of the floor slab segment 30 of another adjacent ring. A ring joint bolt b <b> 1 is inserted through the overhang plate 37.

  The flange 38 is disposed for the purpose of increasing the secondary moment of section of the embedded main beam 3B. The flange 38 of the present embodiment is disposed over the entire length of the overhang plate 37 and is fixed to the boundary plate 35 and the overhang plate 37. As shown in FIG. 5C, the flanges 38 are provided on the upper and lower edges of the overhanging plate 37 and project toward the other embedded main beam 3B. The cross-sectional secondary moment of the overhanging plate 37 is smaller than the cross-sectional secondary moment of the main girder plate 32. However, if the flanges 38, 38 are integrated with the overhanging plate 37, the cross-sectional secondary moment of the embedded main girder 3B. The moment can be increased to the same extent as the main girder plate 32.

  As shown in FIG. 4, the corner steel segment 40 is disposed at a corner where the floor slab B1 and the side wall B2 intersect. It is interposed between the steel segments 50. In this embodiment, since the corner steel segments 40 are juxtaposed so as to be in the potato assembly state, the upper end surfaces of the plurality of corner steel segments 40, 40,. Become one.

  As shown in FIGS. 5A and 5B, the steel segment 40 for the corner portion of the present embodiment is provided on the skin plate 41 serving as the outer shell, and the front edge and the rear edge of the skin plate 41. Main girder plates 42, 42, joint plates 43, 43 provided on the side and upper edges of the skin plate 41, and vertical ribs 44, 44 provided between the main girder plates 42, 42. . Further, although not shown, a sealing material is stuck to the outer surfaces of the main girder plate 42 and the joint plate 43.

  The skin plate 41 is obtained by connecting a steel plate arranged along the floor surface T2 (see FIG. 1) and a steel plate arranged along the mountain retaining wall W (see FIG. 1). It is L-shaped.

  The main girder plate 42 has an L shape corresponding to the skin plate 41. As shown to (a) of FIG. 5, the main girder plate 42 is faced | matched with the main girder plate 42 of the steel segment 40 for other corner parts adjacent to a longitudinal direction.

  Each of the joint plates 43 and 43 includes a water stop end plate 43a and structural reinforcing plates 43b and 43b disposed on the front and rear edges of the end plate 43a. The end face plate 43a is abutted against the floor slab segment 20 or the side wall segment 50 in the same ring.

  As shown in FIG. 4, the lower-side side wall steel segment 50 is a normal type steel segment in which other steel segments are arranged on the front, rear, upper and lower sides, and the inner side surface (side surface on the inner side) is open. It has a box shape.

  The lower-side side wall steel segment 50 has the same configuration as that of the normal type floor slab segment 20 and becomes an outer shell as shown in FIGS. 6 (a) and 6 (b). A skin plate 51, a pair of front and rear main girder plates 52, 52, a pair of upper and lower joint plates 53, 53, and a plurality of vertical ribs 54, 54,. ing. In addition, although illustration is abbreviate | omitted, the sealing material is affixed on the outer surface of the main girder plate 52 and the joint plate 53. FIG.

  The lower side wall steel segment 50 is joined to two steel segments (corner steel segment 40 and upper side wall steel segment 60) belonging to the same ring via each joint plate 53. These are joined to the side wall steel segments 50 belonging to other adjacent rings via the main girder plates 52.

  As shown in FIG. 4, the upper side steel segment 60 for side walls is a boundary installation type steel segment installed at a boundary portion between the side wall portion A2 of the upper concrete frame and the side wall portion B2 of the steel shell frame B. And a box-shaped main body portion 6A having an open inner surface and a bottomed rectangular tube-shaped tubular portion 6B having an open upper surface. The main body 6A is joined to the lower side wall steel segment 50 belonging to the same ring and to the main body 6A of the side wall steel segment 60 belonging to another adjacent ring. Moreover, the cylindrical part 6B is joined to the cylindrical part 6B of the steel segment 60 for side walls belonging to another adjacent ring. In addition, although illustration is abbreviate | omitted, the sealing material is affixed on the outer surface of the joint plate 63. FIG. Further, a seal material (hereinafter referred to as “vertical seal material”) extending in the vertical direction is attached to the outer surface of the main girder plate 62, and the upper end surface of the skin plate 61 and the main girder plate 62, A sealing material is adhered to the upper end surface of 62 so as to extend from the upper end portion of the vertical sealing material of one main girder plate 62 to the upper end portion of the vertical sealing material of the other main girder plate 62.

  As shown in FIG. 6A, the upper side steel segment 60 for side walls includes a partition plate 65, a lid plate 66, a skin plate 61, a main girder plate 62, a joint plate 63, and vertical ribs 64. , Perforated steel plate gibbels 67, 67,... And through reinforcing bars 68, 68,.

The skin plate 61, the main girder plates 62 and 62, the joint plate 63, and the vertical ribs 64 have the same configuration as that of the normal-type side wall steel segment 50.
That is, the skin plate 61 is an outer shell of the main body portion 6A and the cylindrical portion 6B, and the main girder plate 62 is erected on the front edge and the rear edge of the skin plate 61. Further, the joint plate 63 includes a water stop end plate 63a erected on the skin plate 61, and structural reinforcing plates 63b and 63b disposed on the front and rear edges of the end plate 63a. The vertical ribs 64 are arranged in parallel with the joint plate 63.

  The partition plate 65 is disposed at the boundary between the main body portion 6A and the cylindrical portion 6B. The partition plate 65 of the present embodiment is disposed above the vertical rib 64 and is parallel to the joint plate 63. The partition plate 65 is made of a single steel plate having a thickness equivalent to that of the reinforcing plate 63b, and is fixed to the skin plate 61 and the main girder plates 62, 62.

  The lid plate 66 constitutes the inner surface of the cylindrical portion 6B, and is disposed to face the upper half of the skin plate 61 (the outer surface of the cylindrical portion 6B). The lid plate 66 is a structural member having a stress transmission function and is made of a steel plate. As shown in FIG. 7, the front edge portion and the rear edge portion of the lid plate 66 are joined to the first connection plates 62 a and 62 a using a plurality of bolts b <b> 3, and the lower edge portion of the lid plate 66 is a plurality of The bolt b3 is used to be joined to the second connection plate 65a. The first connection plate 62 a is fixed to the side end of the main girder plate 62, and the second connection plate 65 a is fixed to the side end of the partition plate 65.

  The perforated steel plate gibels 67, 67,... Function as shear transmission members and are arranged above the partition plate 65. The inner peripheral surface (skin plate 61, main girder plate 62) of the cylindrical portion 6B. Or it is fixed to the lid plate 66). The skin plate 61 and the lid plate 66 are provided with a plurality (four in the present embodiment) of perforated steel plate gibbles 67, 67,... Extending in the vertical direction. A plurality of (three in this embodiment) perforated steel plate gibbels 67, 67,. It should be noted that the plurality of perforated steel plate gibels 67, 67,... Arranged on the same plane are arranged so that the through holes provided in each are aligned in a straight line.

  The penetration rebar 68 is inserted into the through hole of the perforated steel plate gibber 67. The plurality of penetrating rebars 68, 68,... Arranged along the skin plate 61 are all arranged in the front-rear direction (horizontal direction), and a plurality of perforated steel plate gibels 67 protruding from the skin plate 61. , 67,... Although illustration is omitted, the same applies to a plurality of penetrating reinforcing bars arranged along the lid plate 66. The plurality of penetrating reinforcing bars 68, 68,... Arranged along the main girder plate 62 are all arranged in the vertical direction (vertical direction), and have a plurality of perforations projecting from the main girder plate 62. Crosses with steel plate gibbels 67, 67,.

<Lower concrete frame C>
A lower concrete frame C shown in FIG. 1 is a permanent frame designed to withstand soil water pressure and an overload. The lower concrete frame C includes the floor slab C1 that is a part of the floor (inner floor slab) of the first basement, the side walls C2 and C2 that are the side walls of the second basement, and the bottom slab that is the floor of the second basement. Part (not shown).

  The floor slab portion C1 has a steel frame reinforced concrete structure, and is composed of cast-in-place concrete and reinforcing steel materials such as a main steel frame 71 and a reinforcing bar (not shown). In the present embodiment, in addition to the main steel frame 71, as shown in FIG. 11A, concrete is reinforced by a slab main bar 72, a distribution bar 73, a shear reinforcement bar 74, and the like. The thickness of the floor slab portion C1 is larger than the floor slab portion B1 of the steel shell frame B.

  The floor slab portion C1 of the present embodiment includes a joint region C11 in which the embedded main beam 3B is embedded, a main bar fixing region C12 in which the side wall main bars of the side wall portion C2 are arranged, and a general region designed as a normal slab. C13. The joining region C11 is located on the side portion of the floor slab portion C1, and projects from the side wall portion C2 to the steel shell housing B side. The main bar fixing region C12 is a region immediately above the side wall portion C2, and is located between the joining region C11 and the general region C13.

  The main steel frame 71 is arranged so that the material axis direction is the horizontal direction (left-right direction). The main steel 71 is disposed so as to straddle the main muscle fixing region C12 and the general region C13, and the end of the main steel 71 enters the joining region C11 and is a boundary installation type steel segment 30 for floor slabs. It is joined to the main body 3A. The girder height of the main steel frame 71 is larger than the girder height of the embedded main girder 3B and smaller than the main girder 32.

  In the floor slab portion C1, a plurality of main steel frames 71 are arranged in parallel at intervals in the front-rear direction (longitudinal direction). The adjacent main steel frames 71 and 71 are connected by connecting materials 71a and 71a. An end portion of the connecting material 71 a is connected to a stiffener of the main steel frame 71.

  The main steel frame 71 is installed before the side wall C2 and the bottom slab (not shown) are constructed, and functions as a mountain retaining support when digging between the piles P, P (see FIG. 1).

  The slab main bar 72 and the distribution bar 73 are arranged along the upper surface and the lower surface of the floor slab portion C1. The slab main bar 72 is arranged so as to straddle the main bar fixing region C12 and the general region C13, and an end portion of the slab main bar 72 is fixed to the joining region C11. Note that the width dimension (length in the left-right direction) of the bonding region C11 is set to be 1.5 times or more the thickness dimension of the bonding region.

  The reinforcing bars 73 are arranged in all of the joining area C11, the main reinforcement fixing area C12, and the general area C13, and the shear reinforcing bars 74 are arranged in the joining area C11 and the general area C13.

  The side wall portion C2 has a reinforced concrete structure, and is composed of reinforcing steel materials such as side wall main bars 75, shear reinforcement bars (not shown), and hunch bars 76 and 77, and cast-in-place concrete.

  Although a detailed description is omitted, the bottom plate portion (not shown) is also formed of a reinforced concrete structure. Note that the side wall portion C2 and the bottom plate portion may have a steel reinforced concrete structure.

<Post D>
The support column D shown in FIG. 1 is a permanent structure designed to withstand soil water pressure and an overload. The column D of the present embodiment is erected on the floor slab portion C1 of the lower concrete frame C, and supports the vertical beam portion A3 of the upper concrete frame A. In addition, the support | pillar D is a concrete filling steel pipe structure (CFT structure).

<Joint part of upper concrete frame A and steel shell frame B>
With reference to FIGS. 7-10, the structure of side wall junction part J1 (section which changes from the upper concrete housing A to the steel shell housing B) is demonstrated in detail.

  As shown in FIG. 7, the side wall joint portion J1 includes the side wall main bars 15 and the shear reinforcement bars 17 surrounded by the internal space of the cylindrical portion 6B (skin plate 61, a pair of main girders 62, 62, and a lid plate 66. It is formed by filling the internal space of the cylindrical portion 6B with concrete (not shown) in a state where the bars are arranged in the space.

  That is, the side wall joint portion J1 includes a plurality of side walls extending from the cylindrical portion 6B of the side wall steel segment 60 (skin plate 61, the pair of main girders 62 and 62, and the lid plate 66) to the internal space of the cylindrical portion 6B. Are composed of main reinforcing bars 15, 15, ..., a plurality of shear reinforcing reinforcing bars 17, 17, ... arranged in a direction crossing the side wall main reinforcing bars 15, and concrete filled in the internal space of the cylindrical portion 6B. .

  As shown in FIG. 8, among the plurality of side wall main bars 15, 15,..., The side wall main bars 15 reaching the cylindrical portion 6B are pre-assembled reinforcing bars 15a embedded in the upper concrete frame A in advance, and steel shells. And a rear assembled bar 15b to be added to the lower end portion of the pre-assembled reinforcing bar 15a after the housing B is installed.

  The rear assembled rebar 15b is added to the lower end portion of the front assembled rebar 15a after installing the boundary installation type side wall steel segment 60. In this embodiment, the rear assembled bar 15b is connected to the pre-assembled reinforcing bar 15a via a mechanical reinforcing bar joint, but the type of the reinforcing bar joint is not limited.

  As shown in FIG. 9, the lower end of the rear assembled bar 15b is lower than the lower end of the perforated steel plate diver 67 extending in the vertical direction (the perforated steel plate diver 67 attached to the skin plate 61 or the lid plate 66). Is located. A fixing portion is formed at the lower end portion of the rear assembled bar 15b.

  As shown in FIG. 10, the rear assembled bar 15 b is arranged in a region surrounded by the reference planes S <b> 1, S <b> 2, S <b> 6 so as not to interfere with the steel plate gibber 67.

Here, the reference plane S1 is an imaginary plane set so as not to interfere with the perforated steel plate diver 67 attached to the skin plate 61 (that is, the separation distance from the skin plate 61 is larger than the protruding length of the perforated steel plate gibel 67. And a plane parallel to the skin plate 61.
Similarly, the reference surface S6 is an imaginary plane set so as not to interfere with the perforated steel plate divel 67 attached to the lid plate 66 (that is, the distance from the lid plate 66 is larger than the protruding length of the perforated steel plate gibel 67). And a plane parallel to the lid plate 66.
Further, the reference plane S2 is a virtual plane set so as not to interfere with the perforated steel plate divel 67 attached to the main girder plate 62 (that is, the distance from the main girder plate 62 is the protruding length of the perforated steel plate gibel 67). And a plane parallel to the main girder plate 62.

  As shown in FIG. 9, the shear reinforcement bars 17 are arranged so that the material axis direction is the wall thickness direction (left-right direction). The shear reinforcement bars 17 in the tubular part 6B are arranged after the installation of the side wall steel segments 60, and intersect the rear assembly bars 15b on the skin plate 61 side and the rear assembly bars 15b on the lid plate 66 side.

  The haunch bar 18 includes a pre-assembled haunch bar 18a embedded in the upper concrete frame A in advance, and a rear-assembled haunch bar 18b added to the lower end portion of the pre-assembled haunch bar 18a after the installation of the side wall steel segment 60. In this embodiment, the rear assembled haunch muscle 18b is connected to the front assembled haunch muscle 18a via a mechanical reinforcing bar joint.

  In the side wall joint portion J1, bending moment, axial force, and shearing force are transmitted through the perforated steel plate gibels 67, 67,.

  That is, the stress (tensile stress, compressive stress) acting on the side wall main bars 15, 15,... Is perforated steel plate gibber 67 (attached to the skin plate 61 or the lid plate 66 through the concrete in the tubular portion 6B. It is transmitted to the perforated steel plate gibel 67) extending in the vertical direction and the penetrating rebar 68, and further to the main girder plate 62 via the skin plate 61 or the lid plate 66. Incidentally, the stress acting on the lid plate 66 is transmitted to the connection plates 62a and 65a (see FIG. 7) via the frictional force applied by the bolt b3, and is transmitted to the main girder plate 62 via the connection plates 62a and 65a.

  Further, the stress acting on the shear reinforcement 17 is applied to the perforated steel plate gibber 67 (perforated steel plate extending in the left-right direction) attached to the main girder plate 62 through the concrete in the cylindrical portion 6B and the penetration reinforcing bar 68. To the gibber 67) and further to the main girder plate 62.

  In the side wall joint portion J1 configured as described above, the upper concrete frame A and the steel shell frame B can be integrated to such an extent that it can be evaluated as rigid.

<Joint part of steel shell frame B and lower concrete frame C>
With reference to FIG. 11, FIG. 12, the structure of the floor slab joint part J2 (section which changes from the steel shell frame B to the lower concrete frame C) is demonstrated in detail.

  As shown in FIG. 11A, the floor slab joint J2 is formed by embedding the embedded main girders 3B, 3B of the steel segment 30 for floor slabs in the lower concrete frame C.

  As shown in FIG. 12, the floor slab joint J2 of this embodiment includes a steel segment 30 for floor slabs constituting the floor slab portion B1 of the steel shell frame B and a reinforcing steel material (mainly constituting the lower concrete frame C). Steel frame 71, main slab bar 72, distribution bar 73, shear reinforcement bar 74, etc.) and concrete (not shown) constituting lower concrete frame C.

  As shown in FIG. 11B, the end of the main steel frame 71 is disposed between the embedded main girders 3B, 3B of the steel segment 30 for floor slabs, and is spaced from each embedded main girder 3B. Open and face each other. The main steel frame 71 is arranged so as to be parallel to the embedded main beam 3B. The end surface (end plate 71b) of the main steel frame 71 is abutted against the boundary plate 35 of the main body 3A, and is joined to the boundary plate 35 using bolts and nuts.

  As shown in FIG. 11A, the upper slab main bar 72 is arranged at the same height as the upper edge of the main girder plate 32, and the lower slab main bar 72 is connected to the lower edge of the main girder plate 32. Arrange the bars at the same height. As shown in FIG. 12, the slab main bar 72 is arranged along the material axis direction of the embedded main girder 3B, and the distribution bar 73 crosses the plurality of embedded main girder 3B, 3B,. Arrange the bars. The slab main bar 72 and the distribution bar 73 are also arranged above and below the embedded main beam 3B and the main steel 71 (see FIG. 11B).

  As shown in FIG. 11B, the shear reinforcement bars 74 are arranged before and after the embedded main girder 3B, and intersect the slab main bars 72 and 72 arranged above and below the embedded main girder 3B. . When a bending moment or shearing force is applied to the floor slab joint J2, the concrete positioned above and below the embedded main girder 3B is pressed by the embedded main girder 3B. However, the slab main bar 72 and the distribution bar 73 are arranged above and below the embedded main girder 3B, and cross the slab main bars 72 and 72 at a position close to the embedded main girder 3B. By arranging the shear reinforcement bars 74 in this manner, it becomes possible to prevent punching shear failure, so that the floor slab part B1 of the steel shell frame B and the floor slab part C1 of the lower concrete frame C are integrated. It becomes possible to evaluate.

  The side wall main bar 75 extends to the position of the upper slab main bar 72 and is fixed to the concrete in the main bar fixing region C12. When the main steel frame 71 and the side wall main bar 75 interfere with each other, an insertion hole is formed in the flange of the main steel frame 71, and the side wall main bar 75 is inserted into the insertion hole.

  The haunch muscles 76 and 77 extend to the position of the upper slab main muscle 72. One haunch bar 76 is fixed to the concrete in the joining region C11 (concrete placed in the concrete placement space 3C shown in FIG. 5A), and the other haunch bar 77 is fixed in the general region C13. Fix to concrete.

Although not shown, the embedded main beam 3B may be extended to the main bar fixing region C12, and the embedded main beam 3B and the side wall main bar 75 may be crossed.
<How to build underground structures>

  As shown in FIG. 14, the construction method of the underground structure according to the present embodiment forms an upper concrete frame A that is a part of the main frame, and digs up the ground while using the upper concrete frame A as a mountain retaining support. After that, as shown in FIG. 15, a plurality of steel segments 20 to 60 are juxtaposed on the lower side of the upper concrete frame A, and the adjacent steel segments 20 to 60 are joined together, so that That is, a steel shell frame B that is a part of is formed.

Hereinafter, with reference to FIG. 13 thru | or FIG. 17, the construction method of the underground structure which concerns on this embodiment is demonstrated in detail.
The construction method of the underground structure according to the present embodiment includes a primary excavation process, a first chassis construction process, a secondary excavation process, a second chassis construction process, a tertiary excavation process, and a third chassis construction. A process and a strut construction process.

  The primary excavation step is a step of excavating the ground between the mountain retaining walls W, W to the lower side of the planned construction position of the upper concrete frame A, as shown in FIG. The mountain retaining wall W is a so-called columnar continuous underground wall. To construct the Yamato wall W, excavate the ground with an earth auger, mix and agitate the excavated soil and cement slurry at the original position to form a soil cement, lift the earth auger from the excavation hole, The core material W1 may be built in the ground (excavation hole) before the soil cement is hardened.

  When excavating the ground, the soil cement inside the core material W1 is scraped to expose the core material W1. When the core material W1 is exposed, the bracket W2 is installed on the core material W1.

  When the ground is dug down to the floored surface T1, an intermediate pile M is constructed between the retaining walls W, W, and as shown in FIG. Install the jack M1. In addition, the intermediate pile M temporarily receives the intermediate part of the upper concrete frame A, and consists of the soil cement pile which uses H-shaped steel as a core material.

  The first frame construction step is a step of forming the upper concrete frame A. In the first building construction process, first, a slab formwork or beam formwork is installed on the floored surface T1, and a lower slab main bar 14 or vertical beam main bar 15 (see FIG. 2) is arranged thereon. Make a streak. Next, the transverse steel frame 11 is installed between the brackets W2 and W2, and a support member 11b (see FIG. 2) is installed between the end surface of the transverse steel frame 11 and the inner wall surface of the mountain retaining wall. Restrain movement. Note that the side wall core steel 12 is joined to the transverse steel 11 in advance.

  When the plurality of transverse steel frames 11, 11,... Are installed, the longitudinal steel frame 13 and the connecting material 11a (see FIG. 3) are installed, and further, the upper slab main bar 14, the side wall main bar 15, and the upper vertical beam main bar shown in FIG. 16, shear reinforcement bar 17, haunch bar 18 etc. are arranged. Then, concrete is cast and cured until it reaches a predetermined strength.

  Thus, when the mold is removed while jacking up the jack M1 of the intermediate pile M, as shown in FIG. 14 (a), an upper concrete frame A that also serves as a mountain retaining support appears. In addition, when constructing an underground structure below the existing structure, the existing structure is replaced with the upper concrete frame A.

  As shown in FIG. 14B, the secondary excavation process is a process of digging the lower ground of the upper concrete frame A to the floor surface T2. In the secondary excavation process, the upper concrete frame A is used as a mountain retaining support. In the present embodiment, the cut beam K is installed below the upper concrete frame A. However, the presence or absence of the cut beam K, the number of steps, and the like may be appropriately set according to the excavation depth and the excavation width.

  After excavation to the floor surface T2, although not shown, a waterproof sheet is laid along the floor surface T2 and the inner wall surface of the mountain retaining wall W, and protective mortar and foundation concrete are placed on the waterproof sheet. In addition, the parent piles P and P that are the mountain stops in the third excavation are constructed on both sides of the planned construction position of the lower concrete frame C (see FIG. 1). When the parent piles P, P are constructed, the upper end of the parent pile P is dug down a little, an erection is placed horizontally on the exposed head of the parent stake P, and a bracket P1 is installed on the erection.

  As shown in FIG. 15, in the second case construction step, a plurality of steel segments 20, 30, 40, 50, 60 are arranged in parallel on the lower side of the upper concrete case A, and these are joined to each other to join the steel. This is a process of forming the shell shell B. The second frame construction process includes a steel slab construction process, a steel frame installation process, a steel wall construction process, and the like.

  As shown in FIG. 15 (a), the steel slab construction process is a process of forming steel slab floor slabs B1 and B1 on the left and right floor-attached surfaces T2 and T2. In the steel slab construction process, a plurality of floor slab steel segments 20, 30 and a plurality of corner steel segments 40 are juxtaposed so as to be in a potato assembly state, and these are joined together to form a floor slab. Portions B1 and B1 are formed. For example, the steel segment is installed using a handling machine capable of self-propelling on the floored surface T2 while holding the segment, or using a small lifting machine capable of suspending the segment. You can do it.

  When the segments are “assembled”, the assembling order becomes difficult to be constrained, so various assembling orders can be adopted. For example, three types of steel segments 20, 30, 40 are juxtaposed in a horizontal row. After the horizontally adjacent steel segments 20, 30, 40 are joined to each other to form a horizontally long structure, the other steel segments 20, 30, 40 are aligned in a row on the front side or the rear side. The steel segments 20, 30, and 40 adjacent to each other in the lateral direction may be joined together, and the same kind of segments adjacent in the longitudinal direction may be joined together. In addition, after arranging one kind of segment in parallel in the longitudinal direction, another kind of segment may be arranged in parallel in the longitudinal direction on the side.

  The segments adjacent in the lateral direction are joined by a tensile joining method using bolts b2 (see FIG. 5). An axial force equivalent to 75% of the yield axial force of the bolt b2 is introduced to the bolt b2 as an initial introduction axial force. In the case of “potato assembly”, the position of the segment joint becomes continuous in the longitudinal direction. Therefore, it is not possible to expect the splicing effect as in the case of zigzag assembly, but as described above using the bolt b2. If a small axial force is introduced and the segments are tensile-bonded to each other, the rigidity of the segment joints is hardly lowered, so that it can be designed as a structure having uniform rigidity.

  The steel frame installation process is a process of installing the main steel frame 71 between the floor slab parts B1 and B1. In the steel frame installation process, the main steel frame 71 is disposed in a region where the remaining part of the midslab slab (the floor slab part C1 of the lower concrete frame C) is to be formed, and the end of the main steel frame 71 is used as the main body of the steel segment 30 for floor slab Join to part 3A. Since there are no skin plates above and below the embedded main girders 3B, 3B, the main steel frame 71 can be disposed between the main body portions 3A, 3A simply by lowering the main steel frame 71. In this embodiment, after placing the main steel frame 71 on the bracket P1 of the parent pile P, the end of the main steel frame 71 is joined to the main body 3A of the steel segment 30 for floor slabs. The main steel frame 71 is also joined to the bracket P1.

  When the main steel frames 71, 71,... Are installed, connecting materials 71a, 71a (see FIG. 11) are installed between the main steel frames 71, 71 adjacent in the longitudinal direction, and the main steel frames 71, 71 are connected via the connecting materials 71a, 71a. Are connected. The connecting members 71a and 71a are arranged on both sides of the intermediate pile M, and are also fixed to the intermediate pile M so as to prevent the intermediate pile M from buckling.

  Next, a backing material 81 such as mortar (see FIG. 15B) is injected into the gap between the corner steel segment 40 and the retaining wall W. When the backing material 81 is hardened, the structure formed by connecting the steel segments 20, 30, 40 and the main steel frame 71 can function as a mountain support, so that the cut beam K can be removed. it can.

  Further, as shown in FIG. 15B, the interior of the first floor slab steel segment 20, the interior of the main body 3A of the second floor slab segment 30 and A filling material 82 is placed inside the corner steel segment 40 to smooth the upper surface of the floor slab B 1, and a lining plate 83 is laid on the main steel frame 71. In addition, although there is no restriction | limiting in the kind and material of the padding material 82, In this embodiment, in order to achieve cost reduction, non-structural materials (for example, poor mix | blended concrete, fluidized soil, etc.) are used. .

  The steel wall construction step is a step of forming the side wall portion B2 of the steel shell structure along the mountain retaining wall W. In the steel wall construction step, the plurality of side wall steel segments 50 and 60 are juxtaposed so as to be in a potato assembly state, and these are joined together to form the side wall portions B2 and B2. Segments adjacent in the up-down direction are joined by a tensile joining method using a bolt b2 (see FIG. 6). The bolt b2 corresponds to 75% of the yield axial force of the bolt b2 as an initial introduction axial force. Introduce axial force.

  The installation work of the steel segment is performed using, for example, a handling machine capable of self-propelled on the filling material 82 while holding the segment, or a small lifting machine capable of suspending the segment. You can do it. Since the upper surface of the floor slab B1 is flattened and the beam K (see FIG. 15A) that hinders the movement of the construction machine has already been removed, the installation work of the steel segment is smooth. Can be done.

  The lower side wall steel segment 50 is placed on the upper end surface of the corner steel segment 40 (upper joint plate 43 shown in FIG. 5B). In this embodiment, since the height positions of the upper end surfaces of the plurality of corner steel segments 40, 40,... Are aligned (see FIG. 4 and FIG. 18A), the side wall steel segments 50 are used. Can be easily installed. That is, if it is a "potato assembly", even if it is a case where a steel deck slab construction process precedes, the steel segments 50 and 60 for side walls can be installed easily. In addition, if the steel floor slab construction process is performed prior to the steel wall construction process and the “flat space” by the interlining material 82 is secured at an early stage, the installation work of the steel segments 50 and 60 for the side walls can be performed more efficiently. It becomes possible.

  When the segments are staggered, as shown in FIG. 18 (b), the height of the upper end surfaces of the plurality of corner steel segments 40, 40,... When the side wall steel segments 50 are installed on the corner steel segments 40, it is necessary to insert them between the corner steel segments 40, 40 on both sides. Care must be taken not to peel off the sealing material provided on the surface.

  As shown in FIG. 16A, the upper side wall steel segment 60 has an upper end surface of the lower side wall steel segment 50 without the cover plate 66 (see FIG. 16C) attached. (The upper joint plate 53 shown in FIG. 5B) is placed. In the present embodiment, since the height positions of the upper end surfaces of the lower side wall steel segments 50, 50,... Are aligned (see FIG. 4), the upper side wall steel segments 60 can be easily installed. it can. Note that there is only a clearance between the upper concrete frame A and the lower side wall steel segment 50 so that the upper side wall steel segment 60 just fits, but the rear assembled bar 15b (see FIG. 16). Since (b) is not joined to the pre-assembled reinforcing bar 15a, the side wall steel segments 60 can be installed smoothly.

  When the side wall steel segments 50 and 60 are installed, a backing material 84 such as mortar is provided in the gap between the side wall steel segments 50 and 60 and the retaining wall W as shown in FIG. It inject | pours and restrains the side part of side wall part B2.

  Subsequently, the rear assembled bar 15b is added to the lower end portion of the pre-assembled reinforcing bar 15a (joint portion arranging step). That is, the rear assembly main bar 15b which becomes a part of the side wall main reinforcement 15 is arranged inside the skin plate 61 of the side wall steel segment 60, and the upper end portion of the rear assembly main reinforcement 15b is connected to the lower end portion of the front assembly main reinforcement 15a. . In the present embodiment, a perforated steel plate gibber 67 is disposed outside the area surrounded by the reference planes S1, S2, S6 (see FIG. 10), and the rear side is located inside the area surrounded by the reference planes S1, S2, S6. Since the braiding main bar 15b is arranged, even if there is some bar arrangement error in the pre-braking main bar 15a, the rear braiding main bar 15b is smoothly arranged while avoiding interference with the perforated steel plate gibber 67. can do.

  After that, as shown in FIG. 16C, the shear reinforcing bars 17, 17,... Are arranged between the pair of main girder plates 62, 62, and the rear assembled haunch bars 18b that become a part of the haunch bars 18 are arranged. Are arranged, and the upper end of the rear assembled haunch muscle 18b is connected to the lower end of the preassembled haunch muscle 18a. Since the lid plate 66 is not yet attached, the rear assembly main reinforcement 15b, the shear reinforcement 17 and the like can be easily arranged, and thus the construction period can be shortened.

  When the necessary reinforcing bars are arranged between the pair of main girder plates 62, 62, the lid plate 66 is arranged, and the lid plate 66 is fixed to the main girder plates (cylindrical portion forming step). In the cylindrical part forming step, the side opening of the cylindrical part 6B is closed with the lid plate 66, and as shown in FIG. 16 (d), the three sides of the lid plate 66 are first connected using a large number of bolts. It joins to board 62a, 62a and the 2nd connection board 65a (refer to Drawing 7).

  Thereafter, concrete 19a is filled into the internal space of the cylindrical portion 6B (the space surrounded by the skin plate 61, the pair of main girder plates 62 and 62, and the lid plate 66) (concrete filling step). When placing the concrete 19a, a concrete injection hole (not shown) penetrating the upper concrete frame A vertically is used. The concrete 19a is driven up to the upper edge of the cylindrical portion 6B.

  When the concrete 19a is hardened, the high fluid expansion concrete 19b is filled between the upper surface of the concrete 19a and the lower surface of the upper concrete frame A. When filling the high fluid expansion concrete 19b, mortar injection holes (not shown) penetrating the upper concrete frame A up and down are used. When the existing structure is replaced with the upper concrete frame A, the weight of the existing structure acts on the mountain retaining wall W via the upper concrete frame A, but the upper concrete frame A and the steel shell When the frame B is joined, a rectangular frame structure is formed by the upper concrete frame A, the steel shell frames B and B, and the main steel frame 71, and the weight of the existing structure via the structure. Part of the wall acts on the floored surface T2 and the like, so that the burden on the retaining wall W can be reduced. Instead of the high fluid expansion concrete 19b, non-shrink mortar or the like may be filled.

  The tertiary excavation process is a process of digging the ground between the steel shell frames B, B to a floor surface (not shown) as shown in FIG. In the tertiary excavation process, the ground on the lower side of the main steel 71 is dug down while using the main steel 71 as a mountain retaining support. In addition, you may perform a tertiary excavation process in parallel with an above described side wall construction process. Further, as the third excavation progresses, a cutting beam may be installed below the main steel frame 71.

  The third frame construction step is a step of forming the lower concrete frame C. The lower concrete frame C is constructed by the forward winding method. That is, in the third frame construction process, the side wall portion C2 and the bottom plate portion (not shown) of the lower floor (the second basement floor) are formed in the space below the main steel frame 71, and thereafter the main steel frame 71 is included. By placing concrete in this manner, a floor slab portion C1 serving as an intermediate floor slab of the upper floor (first basement floor) is formed.

  As described above, in the third case construction step, first, a bottom slab part of a reinforced concrete structure is constructed on the floor surface (not shown), and side wall parts C2 and C2 of the reinforced concrete structure are constructed on the bottom slab part. In addition, the side wall main reinforcement 75 of the side wall portion C <b> 2 extends to the vicinity of the height position of the upper surface of the main steel frame 71.

  When the side walls C2 and C2 are constructed, a mold frame (not shown) is disposed below the main steel frame 71, and the slab main bars 72 and the distribution bars 73 shown in FIG. Arrange the bars, and further arrange the shear reinforcement bars 74 and the hunch bars 76 and 77. Since the main steel frame 71 is a reinforcing steel material for the lower concrete frame C, the work of removing the main steel frame 71 is not necessary.

  When the bar arrangement work is finished, concrete is placed on the formwork and cured until it reaches a predetermined strength. When the mold is removed, as shown in FIG. 17 (b), steel slab floor slabs B1 and B1 and steel reinforced concrete floor slabs C1 appear, and the upper floors and An intermediate floor slab is formed.

  The support construction process is a process of forming the support D. In the strut construction process, first, a steel pipe serving as the outer shell of the strut D is installed between the longitudinal beam part A3 and the main bar fixing region C12 of the floor slab part C1, and then the concrete is filled into the steel pipe.

  After the concrete strength reaches a predetermined strength, when the intermediate pile M is removed and the ground material is backfilled in the space above the upper concrete frame A, the state shown in FIG. 1 is obtained.

  According to the underground structure according to the present embodiment, as shown in FIG. 4, since a part of the main housing has a steel shell structure, compared to the case where the entire main housing has a concrete structure, It is possible to reduce the amount of use, and in turn, it is possible to reduce the number of reinforcing bars and formwork.

  In addition, according to the construction method of an underground structure according to the present embodiment, the number of concrete, formwork, rebar, etc. can be reduced, so that the concrete placement time zone is limited. However, even if the work head is too large to use a large lifting machine, it is difficult to prolong the construction period.

  In this embodiment, since the steel segments 20, 30, 40, 50, 60 are arranged side by side so as to be in the potato assembly state, the degree of freedom in the assembly order is increased, and as a result, the construction efficiency can be improved. It becomes possible. In the present embodiment, the steel segments adjacent to each other on the left and right or top and bottom are joined by a tensile joining method using bolts b2.

  In the side wall joint portion J1, as shown in FIG. 7, the main reinforcement 15 of the concrete frame A enters the cylindrical portion 6A of the side wall steel segment 60, and the skin plate 61, the main girder plate 62 and the lid plate 66 are perforated. Since the steel plate gibber 67 (shear transmission member) is protruded, the proof strength of the side wall joint portion J1 can be made more than the proof strength of the upper concrete case A, and between the upper concrete case A and the steel shell case B. The cross-sectional force can be transmitted reliably.

  Further, as shown in FIG. 10, a perforated steel plate gibber 67 is disposed outside the region surrounded by the reference surfaces S1, S2, S6, and the rear assembly is performed inside the region surrounded by the reference surfaces S1, S2, S6. Since the main reinforcement 15b is arranged, a clearance is secured between the main reinforcement 15 and the perforated steel plate gibber 67. In other words, it is possible to absorb the bar arrangement error of the main bar 15 and the installation error of the steel segment 60 for the side wall. The rear assembled main bar 15b can be arranged smoothly while avoiding interference with the gibber 67. Further, since the lid plate 66 is not yet attached at the time when the rear assembly main reinforcement 15b, the shear reinforcement 17 and the like are arranged, it is possible to arrange the arrangement easily, and thus it is possible to shorten the construction period. Become.

  In the floor slab joint J2, as shown in FIG. 12, embedded main girders 3B, 3B are disposed between the upper and lower slab main bars 72, 72, and above and below the embedded main girders 3B, 3B. Since the skin plate is not disposed, the construction work of the main steel frame 71 and the reinforcement work of the shear reinforcement bars 73 can be easily performed, and further, the occurrence of air pockets can be prevented. Moreover, since the concrete placement situation can be visually confirmed, it is possible to easily perform the concrete placement around the embedded main girder 3B and the compacting work around the embedded main girder 3B.

  Further, since the main steel frame 71 is used as the reinforcing steel material for the lower concrete frame C, it is possible to simplify the bar arrangement by reducing the amount of reinforcing bars, and therefore, the bar arrangement work and the compaction work at the side wall joint portion J2 can be performed. It becomes easy.

  Further, since the skin plates are not arranged above and below the embedded main girders 3B, 3B, as shown in FIG. 11A, a reinforcing bar (in this embodiment) extending from the side wall C2 of the lower concrete frame C is used. The haunch bar 76 can be fixed to the concrete in the joining region C11 (concrete placed in the concrete placement space 3C shown in FIG. 5A). In addition, although illustration is abbreviate | omitted, the side wall part C2 may be provided directly under the joining area | region C11, and the main reinforcement of the side wall part C2 may be fixed to the joining area | region C11.

  Further, the upper edge of the embedded main girder 3B is located one level lower than the upper edge of the main body 3A, and the lower edge of the embedded main girder 3B is located one level higher than the lower edge of the main body 3A. Therefore, a large cover thickness can be secured above and below the embedded main beam 3B, and the punching shear failure of the concrete is difficult to occur.

  In this embodiment, as shown in FIG. 15, the main steel frame 71, which is the reinforcing steel material of the lower concrete frame C, is joined to the floor slab part B <b> 1 of the steel shell frame B before the installation of the side wall steel segments 50, 60. Since these are used as the retaining support for the mountain retaining, the beam K used in the secondary excavation process can be removed without waiting for the completion of the floor slab portion C1 of the lower concrete frame C. The installation work of the steel segments 50 and 60 for the side walls can be performed in a state without any gap.

  In addition, the main steel frame 71 not only functions as a support work between the mountain retaining walls W, W, but also functions as a support work when retaining the main piles P, P as shown in FIG. Since it is designed, the lower side of the main steel frame 71 can be dug without waiting for the completion of the mid-floor plate, and thus the construction period can be shortened.

A Upper concrete frame B Steel shell frame 20, 30 Steel segment 50, 60 for floor slabs Steel segment b1, b2 for side wall Bolt W Yamadome wall T1, T2 Floor with floor

Claims (2)

A frame construction process for forming a concrete frame;
An excavation step of digging the ground below the concrete frame to a floor surface;
A steel floor slab construction step in which a plurality of steel segments are juxtaposed on the floor surface and the adjacent steel segments are joined together to form a floor slab part. How to build a structure. An underground structure built by the open-cut method of digging the ground to the floor surface,
Concrete frame,
A steel shell housing formed between the concrete housing and the floored surface,
The steel shell frame has a plurality of steel segments arranged side by side on the floored surface, and is an underground structure.

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