Continuous underground wall

Abstract

This invention provides a continuous underground wall that can reduce the amount of concrete excavation required. [Solution] A continuous underground wall 1 according to one embodiment has a leading element 10 and a trailing element that are constructed in an excavation trench H formed in the ground B. The continuous underground wall 1 includes a partition plate 31 positioned at the boundary between the leading element 10 and the trailing element, and a space-forming member 33 that, together with the partition plate 31, defines a space S in the area A where the trailing element is constructed. The space-forming member 33 is cuttable by an excavator. The leading element 10 has a reinforcing bar unit 11 positioned in the excavation trench H. In a plan view, the excavation trench H and the reinforcing bar unit 11 extend in the direction in which the leading element 10 and the trailing element are aligned. In a plan view, the length L1 of the partition plate 31 is shorter than the width L2 of the excavation trench H in a plan view, and longer than the width L3 of the reinforcing bar unit 11 in a plan view.

Description

Technical Field

[0001] The present disclosure relates to a diaphragm wall having a preceding element and a succeeding element.

Background Art

[0002] Patent Document 1 describes a diaphragm wall and a method for constructing a diaphragm wall. In this diaphragm wall, a preceding element and a succeeding element, which are a plurality of wall-shaped elements, are connected to each other via a joint portion. The joint portion has a partition plate and a T-shaped guide joined to the partition plate. The partition plate is trapezoidal in plan view. A plate-shaped shutter is provided at the lower base portion of the trapezoidal partition plate.

[0003] In this construction method, first, a preceding excavation part, which is a rectangular excavation hole, is formed in the ground, and joint portions are arranged at both ends of the preceding excavation part. At this time, the shutter is attached to the partition plate of the joint portion, and the joint portion is arranged so that the shutter faces both ends of the preceding excavation part. This shutter prevents the adhesion of soil to the partition plate. Then, reinforcement is arranged in the preceding excavation part, and concrete is placed in the preceding excavation part to complete the preceding element. Thereafter, a succeeding excavation part is formed in the area where the succeeding element is to be constructed, reinforcement is arranged in the succeeding excavation part, and concrete is placed in the succeeding excavation part to complete the succeeding element.

[0004] Patent Document 2 describes an end structure of a preceding element and a method for constructing a diaphragm wall. The diaphragm wall is constructed by continuously arranging a succeeding element adjacent to the preceding element. At the joint portion between the preceding element and the succeeding element, a concave portion is formed on the preceding element side, and a convex portion that engages with the concave portion is formed on the succeeding element side. At the bottom of the concave portion, a partition plate having a plurality of joint members and a water stop plate protruding therefrom is arranged. Joint bars are arranged in the convex portion.

[0005] The construction method for a continuous underground wall involves first forming reinforced concrete units that constitute the pre-element, and then placing these units in the pre-excavation trenches created by excavation. Next, space-forming members are installed at the ends of the reinforced concrete units. Granular material is then filled into the spaces enclosed by the space-forming members and partition plates. After that, concrete is poured into the pre-excavation trenches, completing the construction of the pre-element.

[0006] Next, a trailing trench is excavated, which is continuous with the preceding trench. The trailing trench is excavated while cutting the ends of the preceding elements. The excavation of the trailing trench cuts away the space-forming members provided at the ends of the preceding elements. As the space-forming members are cut away, a recess is formed at the end of the preceding element. When the space-forming members are cut away, the granular material collapses towards the trailing trench, exposing the partition plate, connecting member, and water-stopping plate. The granular material is recovered along with the soil generated by the excavation. Then, a reinforcing bar unit is inserted into the trailing trench, and after concrete is poured into the trailing trench, the construction of the trailing element is completed.

[0007] Patent Document 3 describes a continuous underground wall constructed by connecting preceding panels adjacent to succeeding panels in the longitudinal direction. Both the preceding and succeeding panels are formed by pouring concrete with reinforcing cages embedded in them. Two spaced-apart (one pair) corrugated steel plates are embedded in both the preceding and succeeding panels. The preceding panel is provided with a space-holding member that is positioned to cover the outside of the pair of corrugated steel plates. The concrete of the succeeding panel fills the space inside this space-holding member. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2020-165212 [Patent Document 2] Japanese Patent Publication No. 2018-9388 [Patent Document 3] Japanese Patent Publication No. 2024-113855 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] In the construction method for a continuous underground wall described in Patent Document 2 mentioned above, a trailing excavation trench is excavated that is continuous with the trailing excavation trench after the construction of the trailing element is completed. At this time, the ends of the trailing element and the space-forming members are cut, and a portion of the concrete of the trailing element is excavated. If a large amount of concrete is excavated at this time, problems such as an increased workload for the excavation work and wear and tear on the excavator may occur. Therefore, it is necessary to reduce the amount of concrete excavated.

[0010] This disclosure aims to provide a continuous underground wall that can reduce the amount of concrete excavation required. [Means for solving the problem]

[0011] (1) The diaphragm wall according to this disclosure has a leading element and a trailing element that are constructed in an excavation trench formed in the ground. The diaphragm wall comprises a partition plate positioned at the boundary between the leading element and the trailing element, and a space-forming member that, together with the partition plate, defines a space in the area where the trailing element is constructed. The space-forming member is cuttable by an excavator. The leading element has a reinforcing bar unit positioned in the excavation trench. In a plan view, the excavation trench and the reinforcing bar unit extend in the direction in which the leading element and the trailing element are aligned. In a plan view, the length of the partition plate is shorter than the width of the excavation trench in a plan view, and longer than the width of the reinforcing bar unit in a plan view.

[0012] In this continuous underground wall, leading and trailing elements are constructed in excavation trenches formed in the ground, and partition plates are placed between the leading and trailing elements. In the area where the trailing elements are constructed, space-forming members are placed together with the partition plates to define the space. The space-forming members are designed to be cut by an excavator. In a plan view, the excavation trenches and the reinforcement units of the leading elements extend in the direction in which the leading and trailing elements are aligned. The length of the partition plates in a plan view is shorter than the width of the excavation trenches in a plan view, and longer than the width of the reinforcement units in a plan view. Because the length of the partition plates in a plan view is longer than the width of the reinforcement units in a plan view, the amount of concrete that flows from the partition plates into the space when concrete is poured onto the reinforcement units can be reduced. Therefore, the amount of concrete excavated when cutting the space-forming members with an excavator for the construction of the trailing elements can be reduced. Since the amount of concrete excavated when excavating the ends of the leading elements can be reduced, the excavation time can be shortened, the deterioration of the stabilizing fluid used for excavation can be reduced, and the wear and tear on the excavator can be reduced.

[0013] (2) In (1) above, the underground continuous wall may be provided with stress transmission members that protrude from the partition plate into the reinforcement unit and the space. In this case, stress can be transmitted from the reinforcement unit to the space via the stress transmission members.

[0014] (3) In (1) or (2) above, the underground continuous wall may be placed in the space and may be equipped with a reaction force member that applies a reaction force to the preceding element on the partition plate. In this case, a reaction force can be applied from the space to the preceding element by the reaction force member, so that the partition plate and the space forming member can be protected more reliably.

[0015] (4) In (3) above, the reaction member may have an opening and closing mechanism. The opening and closing mechanism may open when it contacts the bottom surface of the excavation trench and come into contact with the partition plate and / or stress transmission member to apply a reaction force, and may close when it moves away from the bottom surface of the excavation trench and move away from the partition plate. In this case, by bringing the opening and closing mechanism into contact with the bottom surface of the excavation trench and opening the opening and closing mechanism, a reaction force can be applied to the preceding element via the partition plate. Then, by moving the opening and closing mechanism away from the bottom surface of the excavation trench and closing the opening and closing mechanism, the reaction member can be removed from the excavation trench.

[0016] (5) In (3) above, the reaction force member may have an expandable portion that expands when air is supplied, and a plate-like portion that contacts the expandable portion and faces the partition plate. The plate-like portion may be in a state where it can contact the partition plate and apply a reaction force when the expandable portion expands, and may separate from the partition plate when the expandable portion contracts. In this case, by expanding the expandable portion with the supply of air, a reaction force can be applied to the preceding element via the plate-like portion and the partition plate. Then, by releasing the air from the expandable portion, the expandable portion can be contracted and the reaction force member can be removed from the excavated trench.

[0017] (6) In (3) above, the reaction force member may be a filling member that fills the space. In this case, the filling member that fills the space can be used as the reaction force member. [Effects of the Invention]

[0018] According to this disclosure, the amount of concrete excavation can be reduced. [Brief explanation of the drawing]

[0019] [Figure 1] Figure 1 is a schematic plan view showing a continuous underground wall according to the embodiment. [Figure 2] Figure 2 is a horizontal cross-sectional view showing a continuous underground wall according to the embodiment. [Figure 3] Figure 3 is an enlarged horizontal cross-sectional view of the end of the leading element in the diaphragm wall shown in Figure 2. [Figure 4]FIG. 4 is a perspective view showing a space forming member, a partition plate, a stress transmission member, and a reinforcing bar unit of the underground continuous wall of FIG. 3. [Figure 5] FIG. 5 is a plan view showing a reaction member in the underground continuous wall according to the embodiment. [Figure 6] FIG. 6 is a perspective view showing a reaction member different from that of FIG. 5. [Figure 7] FIGS. 7(a) and 7(b) are views showing an opening / closing mechanism of the reaction member of FIG. 6. [Figure 8] FIG. 8 is a plan view showing a reaction member different from those of FIGS. 5 and 6. [Figure 9] FIG. 9 is a perspective view showing an example of a specific structure of the reaction member of FIG. 8. [Figure 10] FIG. 10 is a plan view showing an example in which the reaction member is a filling member. [Figure 11] FIG. 11 is a schematic plan view showing the steps of a construction method of an underground continuous wall according to the embodiment. [Figure 12] FIG. 12 is a perspective view schematically showing an excavator. [Figure 13] FIG. 13 is a view showing an underground continuous wall according to a modified example. [Figure 14] FIGS. 14(a) and 14(b) are views showing an underground continuous wall according to a modified example. [Figure 15] FIGS. 15(a) and 15(b) are views showing an underground continuous wall according to a modified example. [Figure 16] FIGS. 16(a) and 16(b) are plan views showing an underground continuous wall according to a modified example. [Figure 17] FIG. 17(a) is a view showing an underground continuous wall according to a modified example. FIG. 17(b) is a view showing a lath net used for the underground continuous wall of FIG. 17(a).

MODE FOR CARRYING OUT THE INVENTION

[0020] The embodiments of the diaphragm wall according to this disclosure will be described below with reference to the drawings. In the description of the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant explanations are omitted as appropriate. For the sake of ease of understanding, some parts of the drawings may be simplified or exaggerated, and the dimensional ratios, etc., are not limited to those shown in the drawings.

[0021] Figure 1 is a schematic plan view showing the continuous underground wall 1 according to this embodiment. As shown in Figure 1, the continuous underground wall 1 is, for example, rectangular in plan view. The continuous underground wall 1 is constructed by placing reinforcing bar units in excavation trenches H formed in the ground B by excavating the ground B, and then pouring concrete into the reinforcing bar units.

[0022] The underground continuous wall 1 has leading elements 10 and trailing elements 20 that are constructed in an excavation trench H formed in the ground B. The underground continuous wall 1 comprises a plurality of leading elements 10 and a plurality of trailing elements 20. In the underground continuous wall 1, the trailing elements 20 are constructed after the leading elements 10 have been constructed. In the underground continuous wall 1, the leading elements 10 and trailing elements 20 are arranged alternately along the circumferential direction of the underground continuous wall 1.

[0023] Figure 2 is a cross-sectional view of the underground continuous wall 1 when cut along a horizontally extending plane. As shown in Figure 2, the leading element 10 includes a reinforcing unit 11 placed in the excavation trench H and concrete 12 poured onto the reinforcing unit 11. The trailing element 20, similar to the leading element 10, includes a reinforcing unit 21 placed in the excavation trench H and concrete 22 poured onto the reinforcing unit 21.

[0024] The underground continuous wall 1 includes a partition plate 31 and a stress transmission member 32, which are positioned at the boundary between the preceding element 10 and the succeeding element 20. Figure 3 shows the end of the preceding element 10 after the concrete 12 of the preceding element 10 has been poured and before the succeeding element 20 has been constructed.

[0025] The partition plate 31 is joined to the reinforcing bar unit 11. For example, the partition plate 31 is joined to the reinforcing bar unit 11 by welding. However, the partition plate 31 may also be joined to the reinforcing bar unit 11 by bolting, and the means of joining the partition plate 31 to the reinforcing bar unit 11 is not particularly limited.

[0026] As shown in Figures 2 and 3, in plan view, the excavation trench H and the reinforcing unit 11 extend in a first direction D1, where the leading element 10 and trailing element 20 are aligned. The first direction D1 is the longitudinal direction of the excavation trench H and the reinforcing unit 11. For example, the reinforcing unit 11 has a reinforcing cage 13 and an element frame 14. The element frame 14 is composed of multiple steel members combined together. For example, the element frame 14 is located in the space inside the reinforcing cage 13 in plan view.

[0027] For example, the element frame 14 comprises a pair of first steel members 14b extending in a first direction D1, a second steel member 14c connecting the pair of first steel members 14b to each other, and a diagonal member 14d. The element frame 14 has a plurality of first steel members 14b, a plurality of second steel members 14c, and a plurality of diagonal members 14d.

[0028] A pair of first steel members 14b are aligned along a second direction D2 that intersects a first direction D1. The second direction D2 is the width direction of the excavation trench H and the reinforcing unit 11. The second steel members 14c extend in the second direction D2 between the pair of first steel members 14b. Multiple second steel members 14c are aligned along the first direction D1. The diagonal members 14d are fixed to each of the four corners of the quadrilateral region defined by the pair of second steel members 14c aligned along the first direction D1 and the pair of first steel members 14b aligned along the second direction D2. However, the diagonal members 14d are placed as needed and may not be placed if unnecessary.

[0029] The reinforcing cage 13 has a plurality of first reinforcing bars 13b extending in a first direction D1, and a plurality of second reinforcing bars 13c extending in a third direction D3 that intersects both the first direction D1 and the second direction D2. In this embodiment, the third direction D3 is the vertical direction. The plurality of first reinforcing bars 13b are aligned along the second direction D2. The plurality of second reinforcing bars 13c are aligned along the first direction D1.

[0030] The above describes an example in which the reinforcing bar unit 11 has a reinforcing bar cage 13 and an element frame 14, as well as an example of the configuration of the reinforcing bar cage 13 and the element frame 14. However, the configuration of the reinforcing bar unit 11 is not limited to the above example and can be changed as appropriate. The configuration of the reinforcing bar unit 21 of the subsequent element 20 is, for example, similar to the configuration of the reinforcing bar unit 11. However, the configuration of the reinforcing bar unit 21 can also be changed as appropriate.

[0031] The underground continuous wall 1 includes a space-forming member 33 that, together with a partition plate 31, defines a space S in area A where the subsequent element 20 is constructed. The space S is filled with stabilizing fluid when the preceding element 10 is constructed. Area A is the wall joint between the preceding element 10 and the subsequent element 20. The space-forming member 33 is designed to be cut by an excavator, which will be described later, and is made of a material that is easy to cut. The space-forming member 33 is cut and removed when the subsequent element 20 is constructed.

[0032] For example, the strength of the space-forming member 33 is less than the strength of the partition plate 31. The space-forming member 33 is made of a low-strength material so that it can be easily cut later. For example, the space-forming member 33 is made of FRP (Fiber Reinforced Plastics). In this case, the space-forming member 33 can be easily crushed into small pieces during cutting. However, the material of the space-forming member 33 is not limited to FRP; for example, the space-forming member 33 may be made of polyvinyl chloride.

[0033] The space-forming member 33 is, for example, U-shaped in plan view. The space-forming member 33 has a pair of first plate-like portions 33b that extend in the first direction D1 and the third direction D3 and have thickness in the second direction D2, and a second plate-like portion 33c that extends in the second direction D2 from the ends of the pair of first plate-like portions 33b opposite to the partition plate 31.

[0034] The pair of first plate-like portions 33b are aligned along the second direction D2. The second plate-like portion 33c extends in the second direction D2 and the third direction D3 and has thickness in the first direction D1. In the space-forming member 33, the pair of first plate-like portions 33b and the second plate-like portion 33c are arranged in a U-shape in plan view.

[0035] For example, the underground continuous wall 1 has a pair of steel plate sections 34 that connect the partition plate 31 and the space-forming member 33 to each other. The pair of steel plate sections 34 are aligned along the second direction D2. The steel plate sections 34 extend in the first direction D1 and the third direction D3 and have thickness in the second direction D2. For example, the steel plate sections 34 are joined to the partition plate 31 and the space-forming member 33, respectively, by bolts and nuts.

[0036] As described above, the space S is defined by the partition plate 31, the space-forming member 33 (a pair of first plate-like parts 33b and a second plate-like part 33c), and the pair of steel plate parts 34. For example, in a plan view, the space S is rectangular. However, the shape of the space S in a plan view may be trapezoidal or semicircular, and is not particularly limited. Furthermore, the steel plate parts 34 may be omitted, and the space-forming member 33 may be directly joined to the partition plate 31. The space-forming member 33 is also called a space protection box or a curing box.

[0037] In a plan view, the partition plate 31 extends in the second direction D2. The partition plate 31 extends in the second direction D2 and the third direction D3 and has thickness in the first direction D1. The partition plate 31 is, for example, a steel plate. In a plan view, the length L1 of the partition plate 31 is shorter than the width L2 of the excavation trench H in a plan view, and longer than the width L3 of the reinforcing bar unit 11 in a plan view. In this embodiment, the length L1 is the length of the partition plate 31 in the second direction D2.

[0038] Since the length L1 of the partition plate 31 is longer than the width L3 of the reinforcing bar unit 11, the amount of concrete 12 that flows into the space S when pouring concrete 12 onto the reinforcing bar unit 11 can be reduced. Therefore, the amount of concrete 12 to be excavated when constructing the trailing element 20 can be reduced. Furthermore, the length of the space S in the second direction D2 can be increased.

[0039] Figure 4 is a perspective view showing the space S. As shown in Figures 3 and 4, the stress transmission member 32 protrudes from the partition plate 31 into the reinforcing bar unit 11 and the space S. For example, the stress transmission member 32 is a perforated steel plate dowel. In this case, the stress transmission member 32 has a through hole 32b that penetrates the stress transmission member 32 in the thickness direction. For example, the shape of the through hole 32b is circular. In addition, reinforcing bars may be passed through some of the through holes 32b of the multiple stress transmission members 32.

[0040] For example, the stress transmission member 32 is fixed to the partition plate 31 by welding. Alternatively, a through hole can be made in an L-shaped steel member and fixed with bolts. The stress transmission member 32 has a first projection 32c that protrudes from the partition plate 31 to the reinforcing bar unit 11 and a second projection 32d that protrudes from the partition plate 31 to the space S. The first projection 32c and the second projection 32d are aligned along the first direction D1.

[0041] Through holes 32b are formed in both the first protrusion 32c and the second protrusion 32d. The presence of the stress transmission member 32 in the underground continuous wall 1 enhances the integration between the reinforcing bar unit 11 of the preceding element 10 and the partition plate 31, and also allows stress to be transmitted to the outside of the preceding element 10.

[0042] As shown in Figure 5, the underground continuous wall 1 is equipped with a reaction force member 35 that applies a reaction force to the preceding element 10 on the partition plate 31. When the underground continuous wall 1 is equipped with a reaction force member 35, deformation of the space S due to the pouring pressure of the concrete 12 can be prevented. The reaction force member 35 is placed in the space S. The reaction force member 35 is, for example, rod-shaped.

[0043] The reaction force member 35 includes, for example, a pair of first rod-shaped portions 35b that contact the partition plate 31, a second rod-shaped portion 35c that connects the pair of first rod-shaped portions 35b to each other, a third rod-shaped portion 35d that extends from the second rod-shaped portion 35c to the space-forming member 33 (second plate-shaped portion 33c), and a fourth rod-shaped portion 35f that extends from one end to the other in the second direction D2 of the space portion S.

[0044] A pair of first rod-shaped portions 35b abut against the partition plate 31, and the third rod-shaped portion 35d abuts against the space-forming member 33, thereby applying a reaction force in the first direction D1 to the reinforcing bar unit 11. By providing the reaction force member 35, the underground continuous wall 1 can more reliably protect the space S. Various modifications of the reaction force member will be described below.

[0045] Figure 6 shows a modified example of the reaction member 35A. Figures 7(a) and 7(b) schematically show the operation of the reaction member 35A. As shown in Figures 6, 7(a), and 7(b), the reaction member 35A has an opening / closing mechanism 35h. The opening / closing mechanism 35h includes a base portion 35j, a pair of arms 35k that swing relative to the base portion 35j, a pair of opening / closing portions 35p attached to each arm 35k on the opposite side from the base portion 35j, and a support member 35q that penetrates the pair of opening / closing portions 35p above the base portion 35j.

[0046] The support member 35q includes a first through member 35q1 that penetrates a pair of opening / closing parts 35p, and a retainer 35q2 that prevents the opening / closing parts 35p from coming out of the first through member 35q1. The support member 35q further includes a second through member 35q3 that protrudes upward from the base portion 35j and penetrates the first through member 35q1, and a retainer 35q4 that prevents the second through member 35q3 from coming out of the first through member 35q1.

[0047] The support member 35q supports the base portion 35j so that it can move relative to the pair of opening / closing portions 35p, by having a second through member 35q3 that protrudes upward from the base portion 35j supported by the first through member 35q1. The base portion 35j is movable along the longitudinal direction of the base portion 35j relative to the pair of opening / closing portions 35p.

[0048] As an example, the base portion 35j is an H-shaped steel beam. The base portion 35j has, for example, a plate-like portion extending in a third direction D3, and this plate-like portion may be a flange of an H-shaped steel beam. A pair of arms 35k are arranged along the width direction of the base portion 35j. The reaction force member 35A has a plurality of sets C consisting of pairs of arms 35k, and the plurality of sets C are arranged along the longitudinal direction of the base portion 35j.

[0049] The arm 35k has a first shaft portion 35k1 rotatably fixed to the base portion 35j, an extension portion 35k2 extending outward in the width direction from the first shaft portion 35k1 to the base portion 35j, and a second shaft portion 35k3 rotatably fixed to the opening / closing portion 35p. The second shaft portion 35k3 is located on the opposite side of the extension portion 35k2 from the first shaft portion 35k1.

[0050] A pair of first shaft portions 35k1 are arranged in the width direction of the base portion 35j. One of the pair of second shaft portions 35k3 is attached to one of the pair of opening / closing portions 35p, and the other of the pair of second shaft portions 35k3 is attached to the other of the pair of opening / closing portions 35p. The lower end of the base portion 35j is located below the lower end of the pair of opening / closing portions 35p.

[0051] Therefore, as shown in Figures 5, 6, 7(a), and 7(b), when the lower end of the base portion 35j is brought into contact with the bottom surface H1 of the excavation trench H, the base portion 35j moves relatively upward with respect to the pair of opening / closing portions 35p, and as a result of this movement, the pair of opening / closing portions 35p open (move away from each other). Then, one of the pair of opening / closing portions 35p comes into contact with the partition plate 31, and the other of the pair of opening / closing portions 35p comes into contact with the space forming member 33. In this way, the opening / closing mechanism 35h opens when it comes into contact with the bottom surface H1 of the excavation trench H, and becomes capable of contacting the partition plate 31 and applying a reaction force.

[0052] Then, when the reaction member 35A is lifted using the pair of opening / closing parts 35p, the lower end of the base part 35j separates from the bottom surface H1 of the excavation trench H, and the base part 35j moves downward relative to the pair of opening / closing parts 35p. As this movement occurs, the pair of opening / closing parts 35p close (move closer to each other). In this way, the opening / closing mechanism 35h closes when it separates from the bottom surface H1 of the excavation trench H and separates from the partition plate 31 and the space-forming member 33. In summary, the reaction member 35A is designed to be lifted and retrieved. In this case, obstacles during the construction of the trailing element 20, obstacles during the erection of the reinforcing cage, and insufficient load-bearing capacity due to cross-sectional defects at the joint can be more reliably avoided.

[0053] Figure 8 is a plan view showing a modified reaction member 35B. The reaction member 35B has an expansion portion 35r that expands when air is supplied, and a plate-like portion 35s that contacts the expansion portion 35r and faces the partition plate 31. The plate-like portion 35s contacts the partition plate 31 and can apply a reaction force when the expansion portion 35r expands, and separates from the partition plate 31 when the expansion portion 35r contracts. For example, the plate-like portion 35s contacts the partition plate 31 via the stress transmission member 32 when the expansion portion 35r expands.

[0054] For example, the reaction member 35B has a plurality of expansion portions 35r, which are arranged along the second direction D2. Figure 9 is a perspective view showing a specific example of the configuration of the reaction member 35B. As shown in Figures 8 and 9, for example, the reaction member 35B has a fixing plate 35t to which the plurality of expansion portions 35r are fixed, and a plate-like portion 35s to which the opposite side of the plurality of expansion portions 35r from the fixing plate 35t is fixed.

[0055] The fixed plate 35t and the plate-like portion 35s are, for example, rectangular in shape. The multiple expansion portions 35r are arranged so as to be aligned along the longitudinal and width directions of the fixed plate 35t. That is, the multiple expansion portions 35r are arranged in a grid pattern. As an example, three expansion portions 35r are arranged along the longitudinal direction of the fixed plate 35t, and two expansion portions 35r are arranged along the width direction of the fixed plate 35t. However, the number and arrangement of the expansion portions 35r are not particularly limited.

[0056] For example, the fixing plate 35t is fixed to the space forming member 33. When the expansion section 35r expands, the plate-shaped portion 35s separates from the fixing plate 35t, and the plate-shaped portion 35s comes into contact with the partition plate 31. The expansion section 35r is, for example, a balloon jack. For example, the reaction force member 35B has a tube 35x connected to the expansion section 35r, and air can be injected into and expelled from the expansion section 35r via the tube 35x. The reaction force member 35B can be recovered by deflating the expansion section 35r by removing the air from it. In this way, since the reaction force member 35B is recoverable, it has the same effect as the reaction force member 35A described above.

[0057] Figure 10 is a plan view showing a modified reaction member 35C. The reaction member 35C is a filling member 35v that fills the space S. The filling member 35v is, for example, crushed stone or gravel. However, the filling member 35v is not limited to crushed stone or gravel, and the type of filling member 35v is not particularly limited. The filling member 35v may be, for example, a stabilizing liquid that fills the space S.

[0058] Next, with reference to Figure 11, an example of a construction method for a continuous underground wall according to this embodiment will be described. The following describes how to construct the continuous underground wall 1. First, the ground B is excavated to form an excavation trench H for constructing the preceding element 10 (step of forming the excavation trench). Next, the reinforcing bar unit 11 is installed in the excavation trench H (step of installing the reinforcing bar unit).

[0059] A partition plate 31 is installed at the end of the excavation trench H in the first direction D1 (step of installing the partition plate). At this time, the partition plate 31, to which the stress transmission member 32 is fixed, is installed on the reinforcing bar unit 11 at a position facing the first direction D1. Then, a space forming member 33 is installed to form a space S (step of forming a space). The space forming member 33 may be connected to the partition plate 31 via a steel plate portion 34.

[0060] A reaction force member 35 is placed in the space S (step of placing the reaction force member). In Figure 11, the illustration of the reaction force member 35 is omitted to avoid complexity. Alternatively, one of reaction force members 35A, 35B, or 35C may be placed in the space S instead of reaction force member 35.

[0061] Then, concrete 12 is poured into the reinforcing bar unit 11 (concrete pouring process). For example, since the length of the partition plate 31 in the second direction D2 is approximately the same as the length of the excavation trench H in the second direction D2, the amount of concrete 12 that flows from the partition plate 31 into the space S can be reduced. The preceding element 10 is completed after the concrete 12 has hardened.

[0062] After the preceding element 10 is completed, the ground B located between the pair of preceding elements 10 aligned along the first direction D1 is excavated, and the succeeding element 20 is installed in the excavated area. At this time, the space-forming member 33 is cut by the excavator M (space-forming member cutting process). For example, the fragments of the space-forming member 33 that have been broken by cutting are crushed into small pieces until they can be sucked up by a pump attached to the excavator M. The fragments of the space-forming member 33 sucked up by the pump are then classified, for example, by a classification plant.

[0063] As mentioned above, the space-forming member 33 may be made of FRP, in which case the space-forming member 33 is lighter and weaker than steel. Therefore, since no reaction force is required when the space-forming member 33 is cut by the excavator M, the advantages of not impairing the vertical accuracy of the excavator M even when excavating on one side, and the advantage of being able to excavate with multiple gutters G can be obtained.

[0064] Incidentally, during the excavation described above, it is necessary to protect the stress transmission member 32 provided at the wall joint of the leading element 10. Therefore, the excavator M is equipped with a guide M1, which is a protective material for protecting the stress transmission member 32. Figure 12 shows a specific example of the configuration of the guide M1. As shown in Figures 11 and 12, the excavator M has, for example, an excavation section M2 that performs excavation and a guide M1 that extends from the excavation section M2.

[0065] The guide M1 includes, for example, a first rod-shaped portion M11 extending from the excavation portion M2, a second rod-shaped portion M12 extending in a direction intersecting the first rod-shaped portion M11 at the end of the first rod-shaped portion M11 opposite to the excavation portion M2, and a pair of diagonal members M13 extending from the first rod-shaped portion M11 to the second rod-shaped portion M12.

[0066] A pair of diagonal members M13 extend diagonally to the first rod-shaped section M11 and away from each other. In the guide M1, when the excavation section M2 excavates, the second rod-shaped section M12 comes into contact with the partition plate 31, thereby separating the excavation section M2 from the stress transmission member 32. Therefore, since the excavation section M2 does not come into contact with the stress transmission member 32, damage to the stress transmission member 32 can be prevented. After the space-forming member 33 is cut by the excavation of the excavator M to form the area where the trailing element 20 will be installed, the reinforcing bar unit 21 is placed in the excavation trench H and concrete 22 is poured. After that, a series of steps for the construction method of the underground continuous wall is completed.

[0067] Next, the effects obtained from the underground continuous wall 1 and the construction method of the underground continuous wall according to this embodiment will be described. As shown in Figures 2 and 3, in the underground continuous wall 1, a leading element 10 and a trailing element 20 are constructed in an excavation trench H formed in the ground B, and a partition plate 31 is placed between the leading element 10 and the trailing element 20. In the area A where the trailing element 20 is constructed, a space-forming member 33 is placed together with the partition plate 31 to define a space S. The space-forming member 33 is designed to be cut by an excavator M. In a plan view, the excavation trench H and the reinforcing bar unit 11 of the leading element 10 extend in the direction in which the leading element 10 and the trailing element 20 are aligned (first direction D1). The length L1 of the partition plate 31 in a plan view is shorter than the width L2 of the excavation trench H in a plan view, and longer than the width L3 of the reinforcing bar unit 11 in a plan view. Because the length L1 of the partition plate 31 in a plan view is longer than the width L3 of the reinforcing bar unit 11 in a plan view, the amount of concrete 12 that flows from the partition plate 31 into the space S when pouring concrete 12 onto the reinforcing bar unit 11 can be reduced.

[0068] Therefore, the amount of concrete 12 excavated when the space-forming member 33 is cut by the excavator M for the construction of the trailing element 20 can be reduced. Since the amount of concrete 12 excavated when the end of the leading element 10 can be reduced, the excavation load can be reduced and wear of the excavator can be prevented. Furthermore, the pressure difference between the inside and outside of the space S surrounded by the space-forming member 33 can be reduced.

[0069] As mentioned above, the space-forming member 33 is made of a material that is easy to cut. Therefore, no reaction force is required when the space-forming member 33 is cut by the excavator M, so even with single-sided excavation, the vertical accuracy of the excavator M is not compromised, and excavation can be performed with multiple guts G. However, conventionally, it was difficult to ensure the vertical accuracy of the excavator unless the concrete between the walls at both ends was excavated simultaneously, and there was a problem that the trailing element was limited to one gut (the width of the excavator).

[0070] In contrast, the continuous underground wall 1 according to this embodiment reduces the amount of concrete excavation required when constructing the trailing element 20, allowing for excavation in multiple gut Gs and improving the flexibility of element placement. For example, as shown in Figure 1, the length of the trailing element 20 can be made to be approximately the same as the length of the leading element 10, increasing the flexibility of placement for both the leading element 10 and the trailing element 20. Furthermore, by making the leading element 10 and the trailing element 20 longer, the number of joints can be reduced, contributing to shorter construction periods and reduced costs.

[0071] In the underground continuous wall 1, the partition plate 31 prevents the concrete 12 from flowing almost completely to the trailing element 20 side. Therefore, since the solidified concrete 12 is not excavated, the concrete hardly dissolves into the stabilizing fluid, and the deterioration of the stabilizing fluid can be suppressed. In other words, when the concrete 12 is excavated, components of the solidified concrete 12 dissolve into the stabilizing fluid, which can increase the alkalinity of the stabilizing fluid and deteriorate its performance. However, in this embodiment, the absence of excavation of the concrete 12 suppresses the deterioration of the stabilizing fluid's performance. As a result, material costs and industrial waste disposal costs can be reduced. When the space-forming member 33 is made of FRP, cutting the space-forming member 33 will generate FRP fragments, but these fragments dissolve into the stabilizing fluid and do not deteriorate.

[0072] As shown in Figures 2 and 3, in this embodiment, the underground continuous wall 1 includes a stress transmission member 32 that protrudes from the partition plate 31 into the reinforcement unit 11 and the space S. In this case, stress can be transmitted between the leading element 10 and the trailing element 20 via the stress transmission member 32. Furthermore, a portion of the stress transmission member 32 is located in the space S. In this case, it is possible to protect the stress transmission member 32 by preventing concrete or soil from adhering to it.

[0073] As shown in Figures 5, 6, 7(a), and 7(b), in this embodiment, the underground continuous wall 1 is positioned in the space S and may also be equipped with a reaction force member (at least one of the reaction force members 35, 35A, 35B, and 35C mentioned above) that applies a reaction force to the preceding element 10 on the partition plate 31. In this case, a reaction force can be applied from the space S to the preceding element 10 by the reaction force member, so that the partition plate 31 and the space forming member 33 can be protected more reliably.

[0074] The reaction force member 35A may have an opening / closing mechanism 35h. The opening / closing mechanism 35h may open when it contacts the bottom surface H1 of the excavation trench H, making it possible to contact the partition plate 31 and apply a reaction force, and may close when it moves away from the bottom surface H1 of the excavation trench H and move away from the partition plate 31. In this case, by bringing the opening / closing mechanism 35h into contact with the bottom surface H1 of the excavation trench H and opening the opening / closing mechanism 35h, a reaction force can be applied to the leading element 10 via the partition plate 31. Then, by moving the opening / closing mechanism 35h away from the bottom surface H1 of the excavation trench H and closing the opening / closing mechanism 35h, the reaction force member 35A can be removed from the excavation trench H.

[0075] As shown in Figures 8 and 9, the reaction force member 35B may have an expansion portion 35r that expands when air is supplied, and a plate-like portion 35s that contacts the expansion portion 35r and faces the partition plate 31. The plate-like portion 35s may be in a state where it can contact the partition plate 31 and apply a reaction force when the expansion portion 35r expands, and may separate from the partition plate 31 when the expansion portion 35r contracts. In this case, by expanding the expansion portion 35r with the supply of air, a reaction force can be applied to the preceding element 10 via the plate-like portion 35s and the partition plate 31. Then, by releasing the air from the expansion portion 35r, the expansion portion 35r can be contracted and the reaction force member 35B can be removed from the excavation trench H.

[0076] As shown in Figure 10, the reaction force member 35C may be a filling member 35v that fills the space S. In this case, the filling member 35v that fills the space S can be used as the reaction force member 35C.

[0077] The following describes various modifications of the diaphragm wall. Figure 13 shows a diaphragm wall 1A according to a modification. As shown in Figure 13, the lower end of the space-forming member 33 is located above the lower end of the partition plate 31. The diaphragm wall 1A has a base reinforcement portion 36 at the lower end of the partition plate 31.

[0078] The reinforcement section 36 may be used instead of Consheet (registered trademark). The reinforcement section 36 is made of, for example, mortar. The reinforcement section 36 is filled below the reinforcing bar unit 11 and below the partition plate 31. The reinforcement section 36 prevents concrete 12 from flowing from below the partition plate 31 into the space S.

[0079] Figures 14(a) and 14(b) show a modified example of the underground continuous wall 1B. As shown in Figures 14(a) and 14(b), the underground continuous wall 1B has crushed stone 37b filled below the space-forming member 33 and a sheet member 37c provided between a pair of partition plates 31. The crushed stone 37b is filled to a depth below the lower end of the partition plates 31.

[0080] Crushed stone 37b is filled, for example, by a crushed stone input pipe 37d inserted into the excavation trench H from the ground. The crushed stone input pipe 37d may be inserted inside the space forming member 33. The sheet member 37c is, for example, ConSheet (registered trademark). The sheet member 37c extends from one of the pair of partition plates 31 to the other. This stabilizes the reinforcing bar unit 11 and prevents the concrete 12 from flowing around it.

[0081] Figures 15(a) and 15(b) show a modified example of a continuous underground wall 1C. As shown in Figures 15(a) and 15(b), the continuous underground wall 1C is equipped with fixing spikes 15 for fixing the reinforcing cage 13 to the bottom surface H1 of the excavation trench H. The fixing spikes 15 allow the reinforcing unit 11 to be stabilized in the excavation trench H. The fixing spikes 15 extend downward from the partition plate 31 and are positioned to penetrate the bottom surface H1 of the excavation trench H. From the state shown in Figures 15(a) and 15(b), crushed stone 37b is filled (see Figures 14(a) and 14(b)), or mortar is filled.

[0082] Figure 16(a) is a schematic plan view of the diaphragm wall 1 described above. Figure 16(b) is a schematic plan view of a modified diaphragm wall 1D. As shown in Figure 16(a), in the diaphragm wall 1, a small gap is formed between the inner surface H2 of the excavation trench H and the partition plate 31, so there is a possibility that concrete 12 from the tremie pipe T may seep around the partition plate 31 and the space-forming member 33 through this gap. In this case, there is a concern that the space-forming member 33 may be damaged by the seeping concrete 12.

[0083] Therefore, as shown in Figure 16(b), the underground continuous wall 1D is equipped with a wrap-around suppression member 16 that suppresses the wrap-around of concrete 12 from the partition plate 31. The underground continuous wall 1D is equipped with a pair of wrap-around suppression members 16, and the pair of wrap-around suppression members 16 are positioned at each end of the second direction D2 of the excavation trench H. The wrap-around suppression members 16 may be made of metal, or for example, the wrap-around suppression members 16 may be made of tinplate.

[0084] The wrap-around suppression member 16 has a first plate portion 16b facing the partition plate 31 in a first direction D1, and a second plate portion 16c extending from the first plate portion 16b along the inner surface H2 of the excavation groove H, and in plan view, the first plate portion 16b and the second plate portion 16c are L-shaped. By arranging the wrap-around suppression member 16 so that the first plate portion 16b is in contact with the partition plate 31 and the second plate portion 16c is in contact with the inner surface H2, it is possible to suppress the concrete 12 from wrapping around from the partition plate 31 to the space-forming member 33.

[0085] Figure 17(a) shows a modified example of a continuous underground wall 1E. The continuous underground wall 1E has a plate-shaped member 38 fixed to the lower end of the space-forming member 33. Figure 17(b) is a perspective view showing the plate-shaped member 38. As shown in Figures 17(a) and 17(b), the plate-shaped member 38 is made of mesh. For example, the plate-shaped member 38 is made of lath mesh.

[0086] The plate-shaped member 38 allows the stabilizing fluid to pass through but not the concrete. Because the plate-shaped member 38 is fixed to the lower end of the space-forming member 33, it is possible to erect the reinforcing cage 13 with high precision without generating excess buoyancy in the reinforcing cage 13. Furthermore, it eliminates the need to fill the space S of the space-forming member 33 with stabilizing fluid.

[0087] The embodiments and various modifications of the diaphragm wall according to this disclosure have been described above. However, the diaphragm wall according to this disclosure is not limited to the embodiments or modifications described above, and may be further modified within the scope of the gist described in the claims. That is, the structure, shape, size, material, number, and arrangement of each part of the diaphragm wall can be appropriately changed within the scope of the gist described above.

[0088] For example, in the embodiment described above, an example was given in which the stress transmission member 32 is a perforated steel plate dowel. However, the stress transmission member 32 may be something other than a perforated steel plate dowel. The stress transmission member 32 may be, for example, a headed stud, and the type of stress transmission member 32 can be changed as appropriate. Furthermore, in a continuous underground wall, it is possible to omit at least one of the stress transmission member 32 and the reaction force device. [Explanation of Symbols]

[0089] 1, 1A, 1B, 1C, 1D, 1E…Continuous underground wall, 10…Leading element, 11…Reinforcement unit, 12…Concrete, 13…Reinforcement cage, 13b…First reinforcement, 13c…Second reinforcement, 14…Element frame, 14b…First steel member, 14c…Second steel member, 14d…Diagonal member, 15…Fixing spike, 16…Wrapping suppression member, 16b…First plate section, 16c…Second plate section, 20…Lagging element 21…Reinforcement unit, 22…Concrete, 31…Partition plate, 32…Stress transmission member, 32b…Through hole, 32c…First projection, 32d…Second projection, 33…Space forming member, 33b…First plate-shaped part, 33c…Second plate-shaped part, 34…Steel plate part, 35,35A,35B,35C…Reaction force member, 35b…First rod-shaped part, 35c…Second rod-shaped part, 35d…Third rod-shaped part, 35f…Fourth rod-shaped part, 35h...Opening / closing mechanism, 35j...Base part, 35k...Arm, 35k1...First shaft part, 35k2...Extending part, 35k3...Second shaft part, 35p...Opening / closing part, 35q...Support member, 35q1...First through member, 35q2...Retaining member, 35q3...Second through member, 35q4...Retaining member, 35r...Expansion part, 35s...Plate-shaped part, 35t...Fixing plate, 35v...Filling member, 35x...Tube, 36...Root reinforcement part, 37b...Crushed stone, 37c...Sheet member, 37d...Crushed stone input pipe, 38...Plate member, A...Area, B...Ground, C...Assembly, D1...First direction, D2...Second direction, D3...Third direction, G...Gut, H...Excavation trench, H1...Bottom surface, H2...Inner surface, L2, L3...Width, M...Excavator, M1...Guide, M2...Excavation section, M11...First rod-shaped section, M12...Second rod-shaped section, M13...Diagonal member, S...Space, T...Tremie pipe.

Claims

1. A continuous underground wall having a leading element and a trailing element, which is constructed in an excavated trench formed in the ground, A partition plate is placed at the boundary between the preceding element and the succeeding element, The area in which the preceding element is installed is provided with a space-forming member that defines a space together with the partition plate, The aforementioned space-forming member is designed to be cut by an excavator. The preceding element has a reinforcing bar unit that is placed in the excavation trench, In a plan view, the excavation trench and the reinforcing bar unit extend in the direction in which the leading element and the trailing element are aligned. In a plan view, the length of the partition plate is shorter than the width of the excavation trench in a plan view, and longer than the width of the reinforcing bar unit in a plan view. Continuous underground wall.

2. The partition plate is provided with stress transmission members that protrude from the reinforcing bar unit and the space. A continuous underground wall according to claim 1.

3. The partition plate is provided with a reaction force member that is arranged in the space and applies a reaction force to the preceding element, A continuous underground wall according to claim 1 or claim 2.

4. The reaction member has an opening and closing mechanism, The opening and closing mechanism opens when it contacts the bottom surface of the excavation trench, making contact with the partition plate and enabling the application of the reaction force, and closes when it moves away from the bottom surface of the excavation trench, moving away from the partition plate. A continuous underground wall according to claim 3.

5. The reaction member has an expandable portion that expands when air is supplied, and a plate-shaped portion that contacts the expandable portion and faces the partition plate. The plate-like portion comes into contact with the partition plate when the expansion portion expands, enabling it to apply the reaction force, and separates from the partition plate when the expansion portion contracts. A continuous underground wall according to claim 3.

6. The reaction member is a filling member that fills the space. A continuous underground wall according to claim 3.

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