Composite wall structure, steel member for retaining wall, and method for constructing composite wall structure

Abstract

To provide a composite wall structure, a steel member for an earth retaining wall, and a construction method of the composite wall structure, superior in even erection performance of the steel earth retaining wall, while securing rigidity capable of coping even with a large depth.SOLUTION: This composite wall structure 1 is formed by sticking concrete to one surface of a steel earth retaining wall 9, constitutes a wall part of an underground space 5 formed by excavating the ground 13, and has a steel member 7 for the earth retaining wall for forming the steel earth retaining wall 9. The earth retaining wall constituent member 7 includes a steel sheet pile 15, an attachment member 17 made of T-shaped steel and provided on a surface of the steel sheet pile 15 to which concrete is attached so as to extend in an axial direction, and a stiffening member 19 made of T-shaped steel or H-shaped steel and provided on a surface of the steel sheet pile 15 on a natural ground side so as to extend in the axial direction. The stiffening member 19 is provided in a range of 60% or less of the wall height above the excavation bottom part 21.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a composite wall structure that forms a wall portion of an underground space by attaching concrete to one side of a steel earth-retaining wall, a steel member for the earth-retaining wall that forms the composite wall structure, and a method for constructing a composite wall structure using the steel member for the earth-retaining wall. [Background technology]

[0002] A method has been used in the past in which a steel retaining wall such as a steel sheet pile is used as a temporary earth retaining wall, the ground is excavated, and a shear stop member is attached to the steel retaining wall to integrate it with a reinforced concrete wall (see, for example, Patent Document 1). Headed studs are commonly used as shear connectors. After steel sheet piles are installed to form a steel earth retaining wall, the ground on one side of the steel earth retaining wall is excavated to expose the surface of the steel sheet piles, and then the headed studs are welded to the surface in situ.

[0003] On-site welding of shear stoppers requires the necessary work space, welding personnel, and equipment, which increases construction costs. Additionally, on-site welding is subject to the effects of weather, which can extend the construction period.

[0004] Therefore, with the aim of reducing the labor required for on-site work on shear-stop members, Patent Document 2 proposes a method in which perforated steel plate dowels are attached in advance to the steel sheet piles that form the retaining wall, and the steel sheet piles are then driven into the ground.

[0005] Furthermore, Patent Document 3 proposes a method of attaching T-shaped steel bars with holes for inserting rebar to steel sheet piles. In this method, by attaching small T-shaped steel bars to the steel sheet piles, it is possible to improve the cross-sectional performance of the steel earth retaining wall and also improve the adhesion performance with the concrete.

[0006] With the recent urbanization, excavation depths have become deeper than ever before. As a result, the earth and water pressure that earth retaining walls must withstand has also increased, making strengthening the rigidity of earth retaining walls an important issue in recent years.

[0007] Therefore, many inventions have been proposed to strengthen the rigidity of earth retaining walls. For example, as in Patent Documents 4 to 6, by joining reinforcing H-shaped steel to one or both sides of a steel sheet pile, the cross-sectional performance of the steel sheet pile is improved, making it possible to form a retaining wall that can withstand soil pressure and water pressure at great depths. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 50-158110 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-13134 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-183475 [Patent Document 4] Japanese Patent Application Laid-Open No. 2015-168995 [Patent Document 5] Japanese Patent Application Laid-Open No. 2008-175029 [Patent Document 6] Japanese Patent Application Laid-Open No. 2008-63765 Summary of the Invention [Problem to be solved by the invention]

[0009] The steel member for the earth retaining wall described in Patent Document 3 has a T-shaped steel for attaching to the concrete on the steel sheet pile, which gives it higher rigidity and better adhesion to the concrete than the steel member for earth retaining wall described in Patent Document 2, which has a perforated steel plate dowel. To further improve the rigidity of the steel member for earth retaining walls of Patent Document 3, it is advisable to increase the cross-sectional shape of the T-shaped steel, but if the cross-sectional shape is made too large, construction using existing hydraulic press-in machines may become difficult. Also, if the flange portion of the T-shaped steel is too far away from the steel sheet pile, there is a risk that the anchorage performance with the concrete will decrease, so from the viewpoint of concrete adhesion, a small web height is preferable. Therefore, the technology of Patent Document 3 has limitations in improving the rigidity of steel members for earth retaining walls.

[0010] On the other hand, as in Patent Documents 4 to 6, by providing a stiffening member to the steel sheet pile, it is possible to form a steel member for an earth retaining wall that has enough rigidity to be applicable to construction at great depths. However, these technologies do not take into consideration the construction of a composite structural wall by integrating a steel earth retaining wall with a reinforced concrete wall.

[0011] Furthermore, when steel sheet piles are used to form a steel retaining wall and a concrete wall is used to construct an underground space, the following problems arise. An underground space equipped with a composite wall structure that integrates a steel retaining wall and a concrete wall is generally constructed in the following steps (1) to (4). (1) Steel components for the retaining wall are connected and cast into the ground to form opposing steel retaining walls. (2) Excavate the ground between the opposing steel retaining walls to form an excavation space. (3) Place retaining members (tension members) between the opposing steel retaining walls. (4) Pour a concrete wall on the side of the steel retaining wall facing the ground excavation.

[0012] When the ground is excavated in (2), a bending moment is generated in the steel members for the earth retaining wall due to earth pressure. This bending moment is largest near the bottom of the excavation, causing the upper end of the steel members for the earth retaining wall to displace toward the excavation space.

[0013] If the steel members for the retaining wall curve gently toward the excavation space, this is undesirable because it will compress the space in the underground space. Furthermore, if the steel components for the retaining wall are gently curved toward the excavation space, the thickness of the concrete wall in the steel components for the retaining wall near the bottom of the excavation must be increased, which results in extra concrete being used and increases costs.

[0014] The present invention has been made to solve the above-mentioned problems, and aims to provide a composite wall structure, steel members for retaining walls, and a method for constructing a composite wall structure that ensures rigidity that can be used at great depths, does not compress the space in the underground space, and does not result in unnecessarily thick concrete walls. [Means for solving the problem]

[0015] (1) The composite wall structure of the present invention is made by attaching concrete to one side of a steel retaining wall, and constitutes the wall part of an underground space formed by excavating the ground. steel members for the earth retaining wall that are connected to each other to form the steel earth retaining wall; The retaining wall constituent member comprises a steel sheet pile, an attachment member made of a T-shaped steel provided so as to extend in the axial direction on the surface of the steel sheet pile to which the concrete is attached, and a stiffening member made of a T-shaped steel or an H-shaped steel provided so as to extend in the axial direction on the surface of the steel sheet pile facing the ground, The attachment members are arranged in a range of 100% to 95% from the upper end of the steel sheet pile to the bottom of the excavation, and the stiffening members are arranged above the bottom of the excavation in a range of 60% or less of the wall height.

[0016] (2) In addition, in the above (1), the attachment member is characterized in that a plurality of T-shaped steels are provided spaced apart in the axial direction.

[0017] (3) The steel member for an earth retaining wall according to the present invention constitutes the composite wall structure described in (1) or (2) above, The present invention provides a steel sheet pile, an attachment member made of a T-shaped steel provided on the surface of the steel sheet pile to which the concrete is attached so as to extend in the axial direction, and a stiffening member made of a T-shaped steel or an H-shaped steel provided on the surface of the steel sheet pile facing the ground so as to extend in the axial direction, The attachment members are arranged in a range of 100% to 95% from the upper end of the steel sheet pile to the bottom of the excavation, and the stiffening members are arranged above the bottom of the excavation in a range of 60% or less of the wall height.

[0018] (4) Furthermore, the method for constructing a composite wall structure according to the present invention is a method for constructing a composite wall structure using the steel member for an earth retaining wall described in (3) above, a step of driving steel members for earth retaining walls into the ground while connecting them to form opposing steel earth retaining walls; a step of excavating the ground between the opposing steel earth retaining walls to form the underground space; a step of placing an earth retaining member between the opposing steel earth retaining walls to correct the steel earth retaining walls to an upright position; and a step of pouring concrete onto the surface of the steel retaining wall facing the underground space. [Effects of the Invention]

[0019] In the present invention, stiffening members are provided only in the areas of the steel sheet pile where the bending moment is large, i.e., from near the bottom of the excavation to deeper than the bottom of the excavation, and stiffening members are not provided in the areas of the steel sheet pile where the displacement is large, i.e., within a certain range from the top end of the steel sheet pile.This ensures rigidity that can be used at great depths, without compressing the space in the underground space, and does not make the concrete walls unnecessarily thick. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is an explanatory diagram (part 1) of a composite wall structure according to an embodiment of the present invention. [Figure 2] FIG. 2 is an explanatory diagram (part 2) of a composite wall structure according to an embodiment of the present invention. [Figure 3] FIG. 3 is an explanatory diagram (part 3) of a composite wall structure according to an embodiment of the present invention. [Figure 4] FIG. 10 is a diagram illustrating the bending moment that occurs in a steel member for a retaining wall installed underground. [Figure 5]FIG. 1 is an explanatory diagram (part 1) of another aspect of a composite wall structure according to an embodiment of the present invention. [Figure 6] FIG. 2 is an explanatory diagram (part 2) of another aspect of the composite wall structure according to an embodiment of the present invention. [Figure 7] 1 is an explanatory diagram of a method for constructing a composite wall structure according to one embodiment of the present invention; [Figure 8] This is a cross-sectional view comparing the case where a composite wall structure is constructed without correcting the posture of a steel retaining wall and the case where a composite wall structure is constructed with correcting the posture. DETAILED DESCRIPTION OF THE INVENTION

[0021] A composite wall structure 1 according to one embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view showing two composite wall structures 1 formed opposite each other and a reinforced concrete floor 3 formed between them. FIG. 2 is a perspective view of the composite wall structure 1 in the foreground of FIG. 1, viewed from the underground space 5 side. FIG. 3 is an enlarged view of one of the steel members 7 for the earth retaining wall that constitutes the composite wall structure 1, viewed from above. 1 to 3, in order to make it easier to understand the configuration of the steel member 7 for the earth retaining wall, the reinforced concrete floor 3, the reinforced concrete wall 11, and the ground 13 other than the steel earth retaining wall 9 are shown in a transparent manner.

[0022] The composite wall structure 1 of this embodiment constitutes the wall portion of an underground space 5 formed by excavating the ground 13, and as shown in Figures 1 and 2, is formed by attaching concrete (reinforced concrete wall 11) to one side of a steel retaining wall 9. The underground space 5 may be used as, for example, an underpass at an intersection, an underground passage, or an underground water tank.

[0023] The steel retaining wall 9 is formed by connecting adjacent steel members 7 for the retaining wall to each other. The steel member 7 for the retaining wall comprises a steel sheet pile 15, an attachment member 17 provided on the surface of the steel sheet pile 15 where the concrete adheres, and a stiffening member 19 provided on the surface of the steel sheet pile 15 facing the ground. Hereinafter, each component of the steel member 7 for the earth retaining wall will be described in detail.

[0024] <Steel sheet piles> In this embodiment, a hat-shaped steel sheet pile (see Figure 3) is used as an example of the steel sheet pile 15, but the present invention is not limited to this and steel sheet piles of other cross-sectional shapes, such as U-shaped steel sheet piles, may also be used. Regardless of the cross section of the steel sheet pile used, the attachment member 17 is attached to the side where the reinforced concrete wall 11 is formed so that it is contained within the reinforced concrete wall 11. In addition, the stiffening member 19 is attached to the natural ground side so that it can resist the bending moment caused by earth pressure.

[0025] <Attachment material> The attachment member 17 is a member made of a T-shaped steel having a shape extending in the axial direction of the steel sheet pile 15. Examples of T-shaped steel used as attachment member 17 include those formed by rolling, those formed by cutting the web portion of an existing H-shaped steel (CT steel), and those formed by combining thick plates into a T shape and welding them together.

[0026] The attachment member 17 is attached in advance by welding or the like to the surface of the steel sheet pile 15 to which concrete will be attached (the surface on which the reinforced concrete wall 11 will be formed). Specifically, the web portion of the T-shaped steel is welded to the steel sheet pile 15 so that the flange portion of the T-shaped steel faces the steel sheet pile 15 with a predetermined gap therebetween.

[0027] The attachment members 17 are provided in a range of 100% to 95% of an area A (see FIG. 2) from the upper end of the steel sheet pile 15 to the bottom 21 of the excavation. The lower end of the attachment member 17 may be extended to a depth deeper than the bottom of the excavation, but there is no need to provide the attachment member 17 in areas that do not need to be integrated with the reinforced concrete wall 11.

[0028] Although not shown in FIGS. 1 to 3, the attachment members 17 and / or the steel sheet piles 15 are provided with a slippage prevention function for preventing slippage between the concrete and the attachment members 17 . The shear stop function can be added by attaching a shear stop member or by forming an uneven portion on the steel sheet pile 15 or the attachment member 17. Examples of shear stop members include deformed steel bars, steel plates with striped projections, corrugated steel plates, and steel pipes with projections on the outer surface.

[0029] The anti-slip member is preferably provided at a position on the attachment member 17 and / or the steel sheet pile 15 facing the flange portion of the attachment member 17 and the area surrounded by the steel sheet pile 15. By providing the shear stopper in this area, the adhesion between the shear stopper and the concrete is increased due to the blocking effect, so that the adhesion with the concrete can be efficiently exerted. The positions facing the above-mentioned area include the surface facing the flange portion of the attachment member 17 of the steel sheet pile 15, the surface of the web portion of the attachment member 17, and the inner surface of the flange portion of the attachment member 17.

[0030] Furthermore, through holes for inserting reinforcing bars may be provided in advance in the web portion of the attachment member 17, so that horizontal reinforcing bars can be arranged in the through holes when the reinforced concrete wall 11 is formed. This further strengthens the unity between the steel retaining wall 9 and the reinforced concrete wall 11.

[0031] The size of the attachment member 17 is not particularly limited, but should be determined taking into consideration the limitations of the construction machine and the concrete fixing effect. For example, if the web height of the attachment member 17 is made too large, it may become difficult to install using an existing hydraulic press-in installation machine for hat-type steel sheet piles, or the aforementioned blocking effect may be reduced, resulting in a decrease in adhesion to the concrete. Therefore, it is desirable to set the web height of the attachment member taking these factors into consideration.

[0032] <Stiffening material> The stiffening member 19 is a member made of a T-shaped steel having a shape extending in the axial direction of the steel sheet pile 15. The T-shaped steel used as the stiffening member 19 may be one formed by rolling, similar to the attachment member 17, one formed by cutting the web portion of an existing H-shaped steel (CT steel), or one formed by combining and welding thick plates into a T shape. Also, H-shaped steel can be used instead of T-shaped steel.

[0033] The stiffening member 19 is attached in advance by welding or the like to the surface of the steel sheet pile 15 facing the ground. Specifically, the stiffening member 19 is attached by welding the web portion of the T-shaped steel to the steel sheet pile 15 so that the flange portion of the T-shaped steel faces the steel sheet pile 15 with a predetermined gap therebetween. When the stiffening member 19 is an H-shaped steel, the stiffening member 19 is attached to the steel sheet pile 15 by fixing one flange portion to the steel sheet pile 15 by welding or the like.

[0034] The stiffening members 19 are provided above the bottom 21 of the excavation in an area of ​​60% or less of the wall height, and are not provided near the upper end of the steel sheet pile 15. Here, being installed within a range of 60% or less of the wall height means that the extension length a of the stiffening member 19 above the bottom 21 of the excavation is set to be less than 60% of the wall height H of the reinforced concrete wall 11 (see Figure 4). Further, below the bottom of the excavation 21, no trenches are provided near the lower end of the steel sheet pile 15.

[0035] That is, as shown in FIG. 4, stiffening members 19 are provided at locations in the steel sheet piles 15 where bending moments of a predetermined magnitude or more (greater than the fine broken lines attached to the bending moment distribution) occur. The reason for limiting the range in which the stiffening member 19 is provided will be explained below with reference to FIG. explain.

[0036] Figure 4 is a cross-sectional view showing steel retaining wall components 7 installed facing each other in the ground, and a reinforced concrete wall 11 and a reinforced concrete floor 3 that were poured by excavating the ground 13 between the opposing steel retaining wall components 7. In Figure 4, the attachment member 17 is shown between the steel sheet pile 15 and the reinforced concrete wall 11, but this is to show the positional relationship of the attachment member 17, and in reality, the attachment member 17 is contained within the reinforced concrete wall 11.

[0037] The bending moment distribution shown in FIG. 4 indicates the bending moment of the steel sheet pile 15 caused by the earth pressure of the ground 13 around the underground space 5. The bending moment acting on the steel sheet pile 15 is greatest at a point slightly deeper than the bottom of the excavation 21, and decreases toward the upper end and the lower end. For this reason, when a large bending moment occurs near the bottom of the excavation 21, the steel sheet pile 15 is significantly bent toward the underground space 5 because there is no natural ground on the underground space 5 side above the bottom of the excavation 21, and the upper end of the steel sheet pile 15 is displaced toward the excavation part. The amount of displacement caused by this becomes larger the closer to the ground surface, so the amount of displacement of the upper end of the steel sheet pile 15 toward the excavation part is the largest. In order to suppress such displacement, stiffening members 19 may be provided in the area where the bending moment is large and where bending starts, specifically in the range of 60% or less of the wall height.

[0038] On the other hand, above 60% of the wall height, the bending moment itself is small, so even if stiffening members 19 are provided in this portion, the effect of suppressing the displacement of the upper end of the steel sheet pile 15 is small. In addition, the reason why the stiffening members 19 are not provided above 60% of the wall height is as follows.

[0039] As mentioned above, even if stiffening members 19 are installed within a range of 60% or less of the wall height, the bending deformation of the steel sheet piles 15 cannot be completely suppressed, and the steel sheet piles 15 will have a gently curved shape toward the underground space. In this case, as stated in the "Problem to be Solved by the Invention" section, the thickness of the concrete wall in the steel sheet pile 15 near the bottom of the excavation must be increased, which results in the use of extra concrete. To prevent this, it is effective to correct the steel sheet pile 15 to an upright position before pouring concrete.

[0040] To correct the posture, a retaining wall member is placed between opposing steel retaining walls 9 made of steel sheet piles 15 so that it is stretched, and the pressing force of the retaining wall member is used to push the steel retaining wall member 7, which is tilted toward the ground excavation side, back toward the natural ground. To make this possible, it is necessary to make the steel sheet pile 15 deformable without increasing the rigidity of the portion where displacement increases. For the above reasons, in this embodiment, the stiffening members 19 are not provided above 60% of the wall height.

[0041] In addition, near the lower end of the steel sheet pile 15, the bending moment is small and bending deformation is suppressed by the natural ground, so no stiffening member 19 is provided in this area either.

[0042] As described above, by placing the steel sheet piles 15 in areas where the bending moment is large, i.e., in a range of less than 60% of the wall height, rigidity that can withstand earth pressure at great depths can be ensured, and the collapse of the steel members 7 for the retaining wall into the underground space is minimized. Furthermore, by not providing stiffening members 19 above 60% of the wall height of the steel sheet piles 15, it is easier to correct the posture of the steel sheet piles 15. This allows for the formation of a highly upright composite wall structure 1, which does not compress the underground space and prevents the concrete wall from becoming unnecessarily thick, and also reduces the weight of the steel for the stiffening members 19. The effect of reducing the concrete wall thickness by increasing the uprightness of the steel earth retaining wall 9 will be described in detail in the method for constructing the composite wall structure 1 described later.

[0043] In addition, an attachment member 17 is provided at the upper end of the steel sheet pile 15, but as mentioned above, a small T-shaped steel with a small web height is used for this attachment member 17 to ensure adhesion to the concrete, so it does not have a stiffening effect that makes it difficult to correct the posture.

[0044] Furthermore, the larger the cross-sectional shape of the stiffening member 19, the greater the rigidity of the stiffening member 19 and the better the stiffening effect. In this embodiment, however, the stiffening member 19 is positioned inside the hat-shaped portion of the steel sheet pile 15, so the web height of the stiffening member 19 can be set large.

[0045] In the above, an example is shown in which the attachment member 17 consists of a single T-shaped steel, but the present invention is not limited to this.As shown in Figures 5 and 6, the attachment member 17 may also consist of multiple T-shaped steels spaced apart in the axial direction of the steel sheet pile 15. By doing so, adhesion to the concrete is ensured while the rigidity of areas that are subject to large displacement due to earth pressure is further reduced, making posture correction even easier.

[0046] When a plurality of T-shaped steel beams are provided at intervals as the attachment members 17, the length L of each T-shaped steel beam may be, for example, 1 to 30 times the flange width W (1W≦L≦30W).

[0047] In addition, it is desirable to set the spacing S between adjacent T-shaped steel beams to a size that prevents them from interfering with each other when the steel members 7 for the retaining wall are bent and deformed by earth pressure or loads during construction. For example, when the web height of the T-shaped steel is 280 mm and the construction accuracy of the steel retaining wall 9 is 1 / 100, that is, when the steel retaining wall 9 is constructed so that the displacement of the upper end of the steel retaining wall 9 is 1 / 100 or less of the wall height H formed by the retaining wall, it is advisable to set the spacing S to approximately 3 mm. In the above case, if the steel sheet pile 15 is inclined by 1 / 100 toward the excavation part, the T-shaped steel constituting the attachment member 17 will also be inclined by 1 / 100 so as to approach the adjacent T-shaped steel below, which may narrow the distance between the flanges of adjacent T-shaped steels by up to about 2.8 mm. Therefore, it is preferable to set the spacing S to about 3 mm, as this will prevent the flanges of adjacent T-shaped steels from interfering with each other.

[0048] Next, a method for constructing a composite wall structure 1 using the steel member 7 for an earth-retaining wall of this embodiment will be described with reference to FIG. First, as shown in FIG. 7(a), steel members 7 for earth-retaining walls are cast into the ground while being connected together to form opposing steel earth-retaining walls 9. Although not shown in Figure 7(a), the steel members 7 for the retaining walls that form each of the opposing steel retaining walls 9 have attachment members 17 on the surface facing the other steel retaining wall 9, and stiffening members 19 on the opposite surface.

[0049] Next, while taking care not to damage the attachment members 17, the ground 13 between the opposing steel earth retaining walls 9 is excavated to form an underground space 5, as shown in FIG. 7(b). Furthermore, the surface of the steel retaining wall 9 is washed to thoroughly remove soil and loose rust adhering to the steel members 7 for the retaining wall.

[0050] Next, as shown in Figure 7(c), the earth retaining member 23 is placed so that it is braced between the opposing steel earth retaining walls 9. In Figure 7(b), the steel earth retaining wall 9 appears to be maintaining an upright position, but in reality, a bending moment is generated by the earth pressure around the underground space 5, causing the upper end to displace toward the excavation. By positioning the retaining member 23 to resist this bending moment, the portion of the steel member 7 for the retaining wall that faces the underground space is pushed back toward the ground by the pressing force of the retaining member 23, and the posture of the steel retaining wall 9 is corrected so that it is upright. Although Figure 7 shows an example in which the earth retaining members 23 are installed after excavation to the target depth, the process of excavating the ground and the process of installing the earth retaining members 23 may be carried out in parallel by installing the earth retaining members 23 each time excavation is performed to a predetermined depth.

[0051] Next, while the temporary earth retaining members 23 are sequentially removed, concrete (reinforced concrete wall 11, reinforced concrete floor 3) is poured onto the surface of the steel retaining wall 9 facing the underground space 5, as shown in Figure 7(d). At this time, it is desirable to perform compaction so that the concrete is reliably filled between the flange portion of the attachment member 17 and the steel sheet pile 15. By following the steps shown in Figures 7(a) to 7(d), a composite wall structure 1 can be constructed by attaching concrete to one side of a steel retaining wall 9 formed by connecting steel components 7 for the retaining wall.

[0052] In the construction method of the composite wall structure 1 described above, the amount of displacement of the upper end of the steel retaining wall 9 can be reduced by using a steel member 7 for the retaining wall that has stiffening members 19 in areas where the bending moment is particularly large (areas located near the bottom of the excavation 21 and slightly deeper than the bottom of the excavation 21).

[0053] Furthermore, the area where the stiffening members 19 are installed is limited to an area above the bottom of the excavation 21 that is no more than 60% of the wall height of the reinforced concrete wall 11, and the area near the upper end is not reinforced intentionally, so that the upper end of the steel earth retaining wall 9 is easily pushed back toward the natural ground when the earth retaining members 23 are placed. This further reduces the amount of displacement of the upper end of the steel earth retaining wall 9, and makes it possible to further improve the uprightness of the steel earth retaining wall 9.

[0054] Next, the effect of reducing the concrete wall thickness by increasing the uprightness of the steel earth-retaining wall 9 will be explained using Fig. 8. Fig. 8(a) is a cross-sectional view showing the composite wall structure 1 when concrete is poured into the steel earth-retaining wall 9 that has not been corrected, and Fig. 8(b) is a cross-sectional view showing the composite wall structure 1 when concrete is poured into the steel earth-retaining wall 9 that has been corrected.

[0055] If stiffening members 19 were installed along the entire length of the steel member 7 for the retaining wall, the rigidity of the upper end, which is subject to large displacement, would also increase, and even if retaining members 23 were placed in the process shown in Figure 7(c), it would not be possible to push the upper end back toward the ground, and there is a risk that posture correction would not be sufficient. If the reinforced concrete wall 11 is poured without correcting the position of the steel retaining wall 9, the thickness of the lower part of the reinforced concrete wall 11 will be thick, as shown in 8(a), which will increase the amount of concrete used and increase costs. In addition, there is a risk that the underground space 5 will be compressed and the required space will not be secured.

[0056] In contrast, by forming a steel retaining wall 9 using the steel member 7 for the retaining wall of this embodiment, the steel retaining wall 9 can be corrected to an upright position when the retaining member 23 is placed in the process shown in Figure 7(c). By increasing the uprightness of the steel retaining wall 9 before pouring the reinforced concrete wall 11, as shown in 8(b), the reinforced concrete wall 11 can be poured with a nearly uniform wall thickness, reducing concrete waste. In addition, the underground space 5 can be made larger.

[0057] The dashed circle in Figure 8(b) indicates the area where the stiffening members 19 are installed in the retaining wall steel member 7, i.e., the area where the rigidity is enhanced. The area where the stiffening members 19 are installed is difficult to correct its posture with the earth retaining members 23, but the amount of displacement due to bending moment in this area is small, so the effect on the wall thickness is also small.

[0058] As described above, according to this embodiment, by providing attachment members 17 at the portions of the steel members 7 for the retaining wall where the concrete will adhere, and by providing stiffening members 19 at the portions where the bending moment is large during ground excavation, it is possible to construct a composite wall structure 1 with sufficient rigidity to be applicable to deep construction work. Furthermore, by not providing stiffening members 19 in the parts of the steel retaining wall member 7 where the bending moment is small and the amount of displacement is large, it is easy to correct the posture of the steel retaining wall 9. This increases the uprightness of the steel retaining wall 9, reducing waste of concrete and ensuring a larger underground space 5. [Explanation of symbols]

[0059] 1 Composite wall structure 3 Reinforced concrete floor 5 Underground space 7 Steel members for earth retaining walls 9 Steel retaining wall 11 Reinforced concrete wall 13 Ground 15 Steel sheet piles 17 Adhesion material 19 Stiffening members 21 Bottom of excavation 23 Earth retaining members

Claims

1. A composite wall structure consisting of a steel retaining wall with concrete attached to one side, forming a wall portion of an underground space formed by excavating the ground. steel members for the earth retaining wall that are connected to each other to form the steel earth retaining wall; The retaining wall component comprises a steel sheet pile, an attachment member made of a T-shaped steel provided so as to extend in the axial direction on the surface of the steel sheet pile to which the concrete is attached, and a stiffening member made of a T-shaped steel or an H-shaped steel provided so as to extend in the axial direction on the surface of the steel sheet pile facing the ground, A composite wall structure characterized in that the attachment members are provided in a range of 100% to 95% from the upper end of the steel sheet pile to the bottom of the excavation, and the stiffening members are provided above the bottom of the excavation in a range of 60% or less of the wall height.

2. 2. The composite wall structure according to claim 1, wherein the attachment member comprises a plurality of T-shaped steel members spaced apart in the axial direction.

3. A steel member for an earth retaining wall constituting the composite wall structure according to claim 1 or 2, The present invention provides a steel sheet pile, an attachment member made of a T-shaped steel provided on the surface of the steel sheet pile to which the concrete is attached so as to extend in the axial direction, and a stiffening member made of a T-shaped steel or an H-shaped steel provided on the surface of the steel sheet pile facing the ground so as to extend in the axial direction, A steel member for a retaining wall, characterized in that the attachment member is provided in a range of 100% to 95% from the upper end of the steel sheet pile to the bottom of the excavation, and the stiffening member is provided above the bottom of the excavation in a range of 60% or less of the wall height.

4. A method for constructing a composite wall structure using the steel member for an earth retaining wall according to claim 3, a step of driving steel members for earth retaining walls into the ground while connecting them to form opposing steel earth retaining walls; a step of excavating the ground between the opposing steel earth retaining walls to form the underground space; a step of placing an earth retaining member between the opposing steel earth retaining walls to correct the steel earth retaining walls to an upright position; A method for constructing a composite wall structure, comprising the step of pouring concrete onto the surface of the steel retaining wall facing the underground space.

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