JP5427044B2 - Construction method for deep foundation construction and construction structure for deep foundation construction - Google Patents

Description

  The present invention relates to a construction method for a foundation for deep foundation work and a structure for a foundation for deep foundation work.

The earth retaining structure for deep foundation work is determined according to the sediment layer such as the wellhead (surface layer) and the geological layer such as the bedrock layer.
Such a retaining structure generally employs a liner plate structure that assembles a liner plate along the hole wall of the excavation hole in the sediment layer, and was sprayed to the rock bolt and the hole wall surface that were driven into the ground in the rock section. The spray structure constructed with shotcrete is adopted (refer to patent documents 1 and patent documents 2).

Japanese Patent Laid-Open No. 06-033682 JP-A-11-303068

However, for example, in a spray structure-applied ground near the boundary between the earth and sand layer and the rock layer, a local weak spot may be detected during excavation.
When a section including such a weak spot occurs, it is necessary to switch to a liner plate structure or the like to construct a soil retaining structure.

However, the change of the earth retaining structure in the deep foundation work may affect the peripheral frictional force of the deep foundation pile constructed using the deep foundation work. Therefore, it was necessary to review the design of the superstructure, the pile length of the deep foundation pile, the pile diameter, etc., when the earth retaining structure was changed at the fragile point discovered during excavation. Therefore, in the construction of structures on the ground including fragile parts, the design of superstructure and piles could not be determined until the construction of the deep foundation work was completed.
In addition, the liner plate structure is expensive because of the large amount of steel used.

  The present invention proposes a method for constructing a foundation for deep foundation work that can be applied to a ground to which a liner plate structure is applied and a ground to which a spraying structure is applied, and a soil retaining structure for a foundation foundation. Is an issue.

  In order to solve the above-mentioned problem, the construction method of a foundation for retaining foundations according to claim 1 includes a primary excavation process for excavating a excavation hole, and a first vertical rebar along the hole wall surface that appears in the primary excavation process. A primary barbing step, a primary spraying step of spraying sprayed concrete against the hole wall surface, and a secondary excavation in which a bottom plate of the excavation hole is dug down to form a space below the first vertical reinforcing bar A step, a support arrangement step of arranging a ring support in the space, a secondary reinforcement step of arranging a second vertical rebar along the hole wall surface of the space shallower than the ring support, and the space And a secondary spraying step of spraying spray concrete against the hole wall surface shallower than the ring support.

  Moreover, the construction method of the foundation for earthwork according to claim 2 appeared by the excavation process for excavating the excavation hole, the support arrangement process for arranging the ring support at the bottom of the excavation hole, and the excavation process. It is characterized by comprising a reinforcing bar arrangement process for arranging vertical reinforcing bars along the hole wall surface shallower than the ring support, and a spraying process for spraying spray concrete to the hole wall surface.

According to such a method for constructing a foundation for deep foundation work, it is possible to construct a stable earth retaining structure regardless of natural ground conditions. Therefore, even if an unexpected ground condition is encountered, the earth retaining structure can be changed by making minor design changes (for example, changing the spraying thickness or changing the bar arrangement pitch) as necessary. It is possible to proceed with the construction without changing. As a result, it is difficult to influence the plan for superstructures and deep foundation piles.
Moreover, since it can construct | assemble without using a special material, it can construct | assemble simply and cheaply.

  Moreover, in the said support material arrangement | positioning process, if it arrange | positions in the state which suspended the said ring support work on the other ring support work adjacent to the upper side, it will become possible to arrange | position a ring support work easily.

  Moreover, the earth retaining structure for deep foundation work of the present invention includes a mesh bar arranged along the hole wall surface of the excavation hole, a plurality of ring support works arranged in parallel in the vertical direction at predetermined intervals, A plurality of vertical reinforcing bars arranged between the ring support works adjacent to each other, and sprayed concrete sprayed against the hole wall surface of the excavation hole, wherein the ring support work is an H-section steel. The vertical reinforcing bar is characterized in that both end portions are respectively inserted into concave portions formed by upper and lower flanges and webs of the ring support.

  According to such a deep foundation construction retaining structure, a stable construction structure can be constructed at low cost. Further, since the peripheral friction with the natural ground can be taken into account, it becomes possible to reduce the shape of the foundation constructed using the deep foundation construction retaining structure, which is economical.

If one flange of the ring support projecting from the surface of the shotcrete, the projecting part can be used as a shear key, and the foundation constructed using the deep foundation construction retaining structure and the Integration with the earth retaining structure is possible.
In addition, when installing the ring support work on the lower side during construction, it is possible to use the protruding part of another ring support work adjacent to the upper side, so the positioning of the ring support work is simplified. Can be performed.

  According to the construction method for deep foundation work and the construction structure for deep foundation work according to the present invention, it can be applied to the ground to which the liner plate structure is applied and the ground to which the spray structure is applied. .

(A) is sectional drawing which shows the earth retaining structure for deep foundation work which concerns on suitable embodiment of this invention, (b) is AA sectional drawing of (a). (A) is an expanded sectional view of the earth retaining structure for the deep foundation work, and (b) is a perspective view showing a vertical reinforcing bar and a mesh reinforcing bar. (A) is a flowchart figure which shows the procedure of the construction method of the foundation foundation for deep foundation work which concerns on this Embodiment, (b) The flowchart figure which shows the procedure of the construction method of the foundation foundation for deep foundation work which concerns on other embodiment. . (A)-(c) is sectional drawing which shows each construction step of the construction method of the earth retaining for deep foundation work of this Embodiment. (A)-(b) is sectional drawing which shows each construction step of the construction method of the earth retaining for deep foundation work of this Embodiment following FIG.

In the present embodiment, as shown in FIGS. 1A and 1B, a deep foundation construction retaining structure 1 formed in a cylindrical shape will be described.
The soil retaining structure 1 for deep foundation work is a soil retaining structure used for deep foundation work, and is formed as the ground G is excavated.

  As shown in FIG. 2 (a), a deep foundation earth retaining structure 1 includes a plurality of ring supporters 3 arranged in parallel at predetermined intervals in a vertical direction in an excavation hole 2 formed in the ground G. , The mesh reinforcement 4 arranged along the hole wall surface 2a of the excavation hole 2, and a plurality of vertical reinforcing bars 5, 5, ... arranged between the ring supporters 3 adjacent to each other vertically. Spray concrete 6 sprayed against the hole wall surface 2a of the hole 2 and configured.

  As shown in FIGS. 1 (b) and 2 (a), the ring support 3 is made of an H-shaped steel formed in an annular shape so as to be continuous in the circumferential direction of the excavation hole 2. In this embodiment, with respect to the depth direction of the excavation hole 2, a plurality of ring supporters 3, 3,.

  The ring support 3 is formed such that H-shaped steel flanges 3a and 3a are vertically oriented and the web 3b is horizontally oriented, and one (outside) flange 3a is in a state (parallel or In contact with each other).

  In the present embodiment, the sum of the width of the gap between the ring support 3 and the hole wall surface 2 a and the thickness (width dimension) of the ring support 3 is larger than the spray thickness of the shotcrete 6. The other (inner side) flange 3a of the ring support 3 projects from the surface of the shotcrete 6.

In addition, the number of the ring support works 3, a pitch, etc. are not limited, It is possible to set suitably. Moreover, what is necessary is just to set suitably the cross-sectional dimension of the H-section steel which comprises the ring support 3.
Further, the planar shape of the ring support 3 is not limited to a circular shape. For example, it may be formed in a rectangular shape or other polygonal shape according to the planar shape of the excavation hole 2.

  As shown in FIG. 2B, the mesh line 4 is a member formed in a lattice shape by combining a plurality of vertical mesh lines 4a, 4a,... And a plurality of horizontal mesh lines 4b, 4b,. .

  As shown in FIG. 2 (a), the mesh line 4 is disposed between the upper and lower ring support members 3 and 3, and the upper and lower ends thereof are the flanges 3a and 3a of the ring support member 3 and the web 3b, respectively. It is inserted into the recess 3c formed by the above. In the present embodiment, the upper and lower ends of the mesh bars 4 are in contact with the webs 3b of the upper and lower ring supporters 3, respectively.

The mesh reinforcement 4 may be a ready-made product such as a factory-produced one, or may be configured by combining reinforcing bars. Further, the diameters of the reinforcing bars of the vertical mesh bars 4a and the horizontal mesh bars 4b constituting the mesh bars 4 are not limited and can be set as appropriate.
In the present embodiment, the mesh streak 4 divided into upper and lower stages is used, and the upper mesh streak 4 and the lower mesh streak are arranged in this order as the excavation hole 2 advances (see FIG. 4 and FIG. 5). Note that the configuration of the mesh streak 4 is not limited. For example, one mesh streak may be disposed, or three or more mesh streaks may be disposed vertically.

As shown in FIG. 1A, the vertical reinforcing bars 5 are reinforcing bars arranged in the vertical direction, and a plurality of vertical reinforcing bars 5 are arranged at predetermined intervals in the circumferential direction along the hole wall surface 2a.
As shown in FIG. 2 (a), the longitudinal reinforcing bars 5 are inserted into recesses 3c formed by flanges 3a, 3a and webs 3b of the upper and lower ring supporters 3, 3, respectively.

  The vertical reinforcing bars 5 are arranged at the same pitch as the vertical mesh reinforcing bars 4a of the mesh reinforcing bars 4, and as shown in FIG. 2 (b), the mesh reinforcing bars 4 are connected via retaining members 7, 7,. It is fixed to.

In addition, the arrangement | positioning pitch of the vertical reinforcing bar 5 is not limited, It is possible to set suitably. Moreover, what is necessary is just to set the reinforcing bar diameter etc. of the vertical reinforcing bar 5 suitably.
Moreover, in this embodiment, what connected the 1st vertical reinforcement 5a and the 2nd vertical reinforcement 5b by the lap joint is called the vertical reinforcement 5 (refer FIG. 4 and FIG. 5). In addition, the structure of the vertical reinforcing bar 5 is not limited, One reinforcing bar may be arranged, and three or more reinforcing bars may be connected and arranged.

The shotcrete 6 is blown against the hole wall surface 2a in which the mesh bars 4 and the vertical reinforcing bars 5 are arranged.
Although the spraying thickness of the shotcrete 6 is not limited, in this embodiment, the flange 3a inside the ring support 3 (center side of the excavation hole 2) protrudes from the surface of the shotcrete 6. Thickness.

  As shown in FIG. 3 (a), the construction of the earth retaining structure 1 for deep foundation work includes a primary excavation step S11, a primary reinforcing step S12, a primary spraying step S13, a secondary excavation step S14, and a support work arrangement. It performs by process S15, secondary reinforcement process S16, and secondary spraying process S17.

The primary excavation step S11 is a step of excavating the ground G to dig down the bottom plate 2b of the excavation hole 2 as shown in FIG.
In addition, when there exists a possibility that the hole wall surface 2a may collapse, for example, a weak spot appears on the hole wall surface 2a of the excavation hole 2, the preceding sprayed concrete 6a is sprayed on the hole wall surface 2a. In addition, the preceding shotcrete 6a shall be implemented as needed and may be abbreviate | omitted.

  In the present embodiment, the case where the excavation hole 2 is dug down by excavating below the existing ring support 3 'will be described, but the presence or absence of the existing ring support 3' is not limited.

  As shown in FIG. 4B, the primary reinforcement step S12 is a step of arranging the mesh reinforcement 4 and the first vertical reinforcement 5a along the hole wall surface 2a that has appeared in the primary excavation process S11.

  In the primary reinforcement step S12, first, the mesh reinforcement 4 is disposed, and then the first vertical reinforcement 5a is fixed to the mesh reinforcement 4 with the retaining member 7 to arrange the first vertical reinforcement 5a.

  The mesh streaks 4 are arranged so that the upper ends thereof are in contact with the lower surface of the web 3b of the existing ring support 3. Note that the mesh streaks 4 do not necessarily have to contact the web 3b of the ring support 3.

  The installation method of the mesh reinforcement 4 is not limited. For example, the mesh reinforcement 4 may be fixed to the ring support 3 via a fastener, or the mesh reinforcement 4 is locked to the anchor member inserted into the hole wall surface 2a. It may be done by doing.

The first vertical reinforcing bar 5 a is fixed to the mesh bar 4 via the retaining member 7 in a state of being superposed on the vertical mesh bar 4 a of the mesh bar 4.
In the present embodiment, the vertical pitch of the vertical mesh bars 4a and the first vertical bars 5a (longitudinal bars 5) are made the same by arranging the first vertical bars 5a along the vertical mesh bars 4a. The vertical mesh bars 4a and the vertical reinforcing bars 5 are not necessarily arranged at the same pitch.

  In addition, when there is no existing ring support 3, the position above the bar arrangement location of the mesh reinforcement 4 and the first vertical reinforcement 5 a prior to the arrangement of the mesh reinforcement 4 and the first vertical reinforcement 5 a. The ring support 3 is arranged on the side.

  As shown in FIG. 4C, the primary spraying step S13 is a step of spraying the spray concrete 6 against the hole wall surface 2a in which the first vertical reinforcing bars 5a are arranged.

  The shotcrete 6 is performed so that the lower end of the first vertical rebar 5a protrudes from the lower surface of the shotcrete 6 as shown in FIGS. The protruding length of the first vertical reinforcing bar 5a is set to a length that can secure a fixing length necessary for connection between the first vertical reinforcing bar 5a and the second vertical reinforcing bar 5b (see FIG. 5A).

The shotcrete 6 passes through each grid formed by the grid-like mesh bars 4 and the first vertical reinforcing bars 5a, and is sprayed onto the hole wall surface 2a (the surface of the preceding shotcrete 6a).
The shotcrete 6 is also applied to the recess 3c of the ring support 3. The shotcrete 6 is performed by a shot thickness at which the first vertical reinforcing bar 5a can secure a predetermined covering concrete thickness and a part of the ring support 3 can protrude.

  As shown in FIG. 4C, the secondary excavation step S14 forms a space 2c for digging down the bottom plate 2b of the excavation hole 2 and installing the ring support 3 below the first vertical rebar 5a. It is.

  In addition, in the secondary excavation process S14, when the weak spot where collapse of the hole wall surface 2a is expected is exposed, the preceding shotcrete 6a (see FIG. 4B) may be performed.

  As shown in FIG. 4C and FIG. 5A, the support placement step S15 is a step of placing the ring support 3 in the space 2c formed in the secondary excavation step S14.

In this embodiment, as shown to Fig.5 (a), it carries out by making the existing ring support 3 'adjoining the upper side through the attachment member 8 to suspend the ring support 3. In the present embodiment, a plurality of attachment members 8 are used.
In addition, the installation method of the ring support work 3 is not limited, It can carry out suitably. For example, you may fix to the attachment member (for example, anchor etc.) fixed to the hole wall surface 2a of the excavation hole 2. FIG.

The mounting member 8 of the present embodiment includes a bar 8a and hook-shaped locking portions 8b and 8b provided on the upper and lower ends thereof.
With the upper locking portion 8b of the attachment member 8 locked to the upper surface of the flange 3a of the existing ring support 3 ', the flange 3a of the ring support 3 is locked to the lower locking portion 8b. Thus, the ring support 3 is disposed at a predetermined position.

  The ring support 3 is easily positioned by being supported by the mounting member 8. That is, by installing the ring support 3 through the attachment member 8, the interval between the ring support 3 'and 3 is determined (arranged at a predetermined depth), and the ring support 3 is planar. The position is also determined. The ring support 3 is arranged directly below the existing ring support 3 'adjacent to the upper side. Here, the configuration of the attachment member 8 is not limited and can be set as appropriate.

  The secondary reinforcement step S16 is a step of arranging the mesh reinforcement 4 and the second vertical reinforcing bar 5b along the hole wall surface 2a of the space 2c shallower than the ring support 3 as shown in FIG. 5A. .

  The mesh streak 4 is configured as one sheet by connecting the lower mesh streak 4 to the existing mesh streak 4 disposed on the upper side via a binding line or the like.

The second vertical reinforcing bar 5b is arranged with a predetermined lap joint secured to the lower end of the first vertical reinforcing bar 5a. The second vertical reinforcing bars 5b are arranged by being fixed to the mesh bars 4 via the retaining members 7 while being superposed on the vertical mesh bars 4a of the mesh bars 4.
In the present embodiment, a structure in which the first vertical reinforcing bar 5a and the second vertical reinforcing bar 5b are connected by a predetermined lap joint is referred to as a vertical reinforcing bar 5.

  The secondary spraying step S17 is a step of spraying the sprayed concrete 6 against the hole wall surface 2a shallower than the ring support 3 in the space 2c.

The shotcrete 6 passes through each grid formed by the grid-like mesh bars 4 and the second vertical reinforcing bars 5b, and is sprayed onto the hole wall surface 2a.
The shotcrete 6 is also applied to the recess 3c of the ring support 3. Further, the shotcrete 6 is performed by the shot thickness in which the second vertical reinforcing bar 5 a can secure a predetermined covering concrete thickness and a part of the ring support 3 projects from the surface of the shotcrete 6.

  As described above, according to the earth retaining structure 1 for deep foundation work of the present embodiment, the ring support 3, the vertical rebar 5, and the shotcrete 6 are integrated to express excellent proof stress. It has sufficient strength against the compression force caused by

  Moreover, since it is comprised by the combination of the concrete wall formed by the vertical reinforcement 5 and shotcrete 6, and the ring support work 3, it constructs the earth retaining structure according to the natural ground condition by performing strength calculation. (Specification of each material and setting of spraying thickness) are possible. Therefore, the overall cost can be reduced.

  In addition, it is possible to construct a stable earth retaining structure without being affected by natural ground conditions. Therefore, even when an unexpected ground condition is encountered, it is possible to proceed with construction without changing the earth retaining structure. As a result, it is difficult to influence the plan for superstructures and deep foundation piles. At this time, the earth retaining structure 1 for deep foundation work, if necessary, change of spraying thickness, change of bar arrangement pitch of vertical rebar 5, change of cross-sectional dimensions of steel materials such as ring support 3 and vertical rebar 5, etc. Minor design changes may be made.

  Moreover, since the earth retaining structure 1 for deep foundation work can be constructed without using a special material, it can be constructed simply and inexpensively.

In addition, since a part of the ring support 3 protrudes from the surface of the shotcrete 6, the earth retaining structure 1 can be integrated with the foundation pile using the protruding portion as a shear key.
Furthermore, since the earth retaining structure 1 for deep foundation work is a concrete structure, it is possible to consider frictional resistance, and to reduce the cross section of the foundation structure constructed using the earth retaining structure 1.

  Moreover, the ring support 3 can be easily arranged and positioned by suspending the ring support 3 adjacent to the lower side by using the projecting portion of the ring support 3 from the shotcrete 6. It becomes possible.

  Moreover, according to the construction method of a deep foundation earth retaining of this embodiment, even when the distance between the ring supporters 3 is large, the excavation of the excavation hole 2 is divided into a primary excavation process and a secondary excavation process. Thus, each work can be performed in a state where safety during construction is ensured.

  In addition, when there is no fear of collapse of the hole wall surface between the excavation of the ground and the spraying to the hole wall surface 2 as shown in FIG. The foundation structure 1 for deep foundation work may be constructed by the excavation step S21, the support placement step S22, the bar arrangement step S23, and the spraying step S24.

  That is, in the excavation step S21, the bottom plate 2b of the excavation hole 2 is dug down to a depth that allows a space for arranging the ring support 3 to be secured, the arrangement of the support 3, the arrangement of the mesh reinforcement 4 and the vertical reinforcement 5, It is only necessary to spray the attached concrete 6.

The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and it goes without saying that the above-described constituent elements can be appropriately changed without departing from the spirit of the present invention.
For example, in the above embodiment, a part of the ring support is projected from the shotcrete, but the ring support need not necessarily protrude from the shotcrete.

Further, in the above-described embodiment, after arranging the mesh reinforcement at a predetermined position, the vertical reinforcement is arranged by fixing the vertical reinforcement to the mesh reinforcement. Arrangement of mesh bars and vertical reinforcing bars may be performed at the same time by arranging them at positions.
In addition, what is necessary is just to arrange | position a mesh line | wire as needed and may abbreviate | omit.

  In addition, if the construction site of the foundation for deep foundation work, such as soft ground laminated on the surface side, includes a stratum where it is difficult for the ground to stand on its own, it will be constructed in combination with the liner plate method. May be.

  Moreover, you may arrange | position a lock bolt with respect to a natural ground as needed.

Next, a description will be given of the result of a demonstration experiment performed on the earth retaining structure for deep foundation work of the present invention.
In this demonstration experiment, if the vertical reinforcing bars are properly arranged, there will be no problems in ensuring the quality of shotcrete, and the quality (strength, etc.) of the retaining structure can be improved. It was confirmed.

  In this demonstration experiment, with respect to a mesh streak having a depth (thickness) of 200 mm and a longitudinal mesh and a transverse mesh streak arranged on the surface side of a test box of 1 m × 1 m in length and width, arranged at a constant pitch. Thus, the amount of sprayed concrete adhering and permeating and the quality of the shotcrete were confirmed when shotcrete was sprayed with the pitch of the vertical reinforcing bars changed.

  In this demonstration experiment, a mesh bar having a vertical interval and a horizontal interval of 150 mm is used. When only the test piece A is a mesh bar, the pitch of the vertical bar as the test piece B is the same as the vertical mesh bar of the mesh bar (150 mm). In the case where the pitch of the vertical reinforcing bars is 100 mm as the specimen C, the pitch of the vertical reinforcing bars is 75 mm as the specimen D.

In addition, the permeation | transmission amount measurement of shotcrete was performed by measuring the volume of shotcrete in a test box.
The amount of adhesion was measured by measuring the weight of sprayed concrete adhering to the reinforcing bars and mesh bars.
The strength was measured by a pneumatic pin penetration test, and the quality was measured by an appearance inspection.
The experimental results are shown in Table 1.

As a result of the demonstration experiment, as shown in Table 1, the spraying density of the shot concretes of the specimens B to D (1. 1) is higher than the spray density of the shot concrete of the specimen A (1.133 t / m ³ ). 1.347 to 1.512 t / m ³ ) was larger. For this reason, the effect on the amount of permeation due to the placement of vertical reinforcing bars was small.

Moreover, as shown in Table 1, the amount of adhesion to the vertical bars and mesh bars is the amount of adhesion of the specimens B to D (0.200 to 0.257 kg / piece) in which the vertical bars are arranged. It became larger than the adhesion amount (0.029 kg / piece) of the specimen A which has not been arranged. From this, it can be seen that the amount of adhesion increases by arranging the vertical reinforcing bars.
In addition, the adhesion amounts of specimens B, C, and D were 0.257 kg, 0.200 kg, and 0.246 kg per reinforcing bar, respectively, and the effect of the change in the bar arrangement pitch was small.

Furthermore, as shown in Table 1, the compressive strength by the pin penetration test of specimens B to D in which vertical reinforcing bars are arranged is 4.50 to 4.96 N / mm ^{2 in} the reinforcing bar non-interfering part, and 4 in the reinforcing bar crossing part. .39 to 4.67 N / mm ² , from the compressive strength 4.23 N / mm ^{2 of} the reinforcing bar non-interfering portion of the specimen A with no vertical reinforcing bars, and the compressive strength of the reinforcing bar crossing portion 4.13 N / mm ² The result also became larger.
The compressive strengths of specimens B, C, and D with longitudinal reinforcing bars are 4.50, 4.69, and 4.96 N / mm ^{2 at} the reinforcing bar non-interfering parts, respectively, and 4.39 at the reinforcing bar crossing parts, respectively. The results were 4.42 and 4.67 N / mm ² , and the strength did not decrease even when the interval between the vertical bars was reduced.

As a result of the above, compared to the quality of shotcrete when only mesh bars with a spacing of 150 mm are placed, the quality of shotcrete is also improved even when vertical bars are placed at intervals of 150 mm to 75 mm in addition to the mesh bars. Was confirmed not to decrease. In other words, no trouble was observed by arranging the vertical reinforcing bars at a pitch of 1 to 0.5 times the vertical mesh reinforcing bars.
Therefore, it was proved that the strength of the retaining structure can be increased without deteriorating the quality of the shotcrete of the foundation for deep foundation work by appropriately arranging the reinforcing steel bars.

DESCRIPTION OF SYMBOLS 1 Retaining structure for deep foundation work 2 Excavation hole 2a Hole wall surface 2b Bottom board 2c Space 3 Supporting work 3a Flange 3b Web 3c Recessed part 4 Mesh reinforcement 5 Vertical reinforcement 5a First vertical reinforcement 5b Second vertical reinforcement 6 Shotcrete

Claims (5)

A primary excavation process for digging a drill hole;
A primary reinforcement step of arranging the first vertical rebar along the hole wall surface that appears in the primary excavation step;
A primary spraying step of spraying spray concrete against the hole wall surface;
A secondary excavation step of digging down the bottom of the excavation hole to form a space below the first vertical rebar;
A support work placement step of placing a ring support work in the space;
A secondary reinforcement step of arranging a second vertical rebar along the hole wall surface of the space shallower than the ring support,
A secondary spraying step of spraying spray concrete against the hole wall surface shallower than the ring support in the space;
A construction method of a soil retaining for deep foundation works, characterized by comprising: An excavation process for digging the excavation hole;
A support work placement step of placing a ring support work at the bottom of the excavation hole;
A bar arrangement process for arranging vertical reinforcing bars along the hole wall surface shallower than the ring support that appeared in the excavation process;
A spraying step of spraying spray concrete against the hole wall;
A construction method of a soil retaining for deep foundation works, characterized by comprising:   3. The deep foundation work according to claim 1, wherein, in the support placement step, the ring support is placed in a state of being suspended by another ring support adjacent to the upper side. How to construct a retaining ring. Mesh streaks arranged along the hole wall of the excavation hole;
A plurality of ring support works arranged in parallel in the vertical direction with a predetermined interval;
A plurality of vertical reinforcing bars arranged between the ring support works adjacent to each other vertically;
Sprayed concrete sprayed against the hole wall surface of the excavation hole;
A soil retaining structure for deep foundation work with
The ring support is made of H-section steel,
The vertical reinforcing bar retaining structure for deep foundation works, wherein both end portions are respectively inserted into recesses formed by upper and lower flanges and webs of the ring support work.   The earth retaining structure for deep foundation works according to claim 4, wherein one flange of the ring support projectingly protrudes from the surface of the shotcrete.

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