JPH073778A - Rigid-connection joint of underground continuous wall - Google Patents

Abstract

PURPOSE:To provide a rigid-connection joint that can resist the lateral pressure of concrete when the concrete is placed and resist a sharing force after an underground continuouns wall is complete by forming the joint out of a web which extends in the direction of depth of a wall body while taking a semicylindrical shape and shearing plates each having a shear resisting portion. CONSTITUTION:A partition steel sheet 2 comprises a curved web 3 the diameter of curving of which almost coincides with the separation part between main reinforcements 6 and a T-flange 4 connected to the end portion thereof. Shearing plates 5 are welded to both of the center of the web 3 along the direction of depth, and the outer edge of each plate 5 is saw-toothed. The lateral pressure of concrete placed in the body of a continuous underground wall acts on the steel sheet 2 as well as on the natural ground, and the web 3 resists the working lateral pressure with its arching effect, and the working lateral pressure is transmitted to a joint box 8 via a flange 4. A joint portion resists an out-of- plane shearing force exerted by the plates 5, and the in-plane shearing force is transmitted to the concrete via the end face of the thick saw-toothed portion of each plate 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rigid joint for a continuous underground wall, and in particular, it resists the lateral pressure of concrete acting on the concrete wall of the continuous underground wall, and at the time of completion of the predetermined wall body. The present invention relates to a rigid joint for an underground continuous wall capable of transmitting stress.

[0002]

2. Description of the Related Art Underground continuous walls are used not only as temporary earth retaining walls but also as two-way lateral pressure-resistant walls or earthquake-resistant walls of large-scale structures that use underground spaces, and their structural advantages are widely recognized. It is a basic structure. In construction of long bridges and skyscrapers, it is first used as a highly rigid temporary mountain retaining wall that receives earth pressure and water pressure, and then used as a basic structure or part of the main structure in main body construction. In this way, as its applications spread, specifications for construction accuracy and structural strength become strict, and various studies and countermeasures are being made in design and construction.

Normally, a continuous underground wall has its construction shape, extension,
It is assigned to multiple elements depending on the scale of the excavating machine, first the wall of the preceding element part is built in a predetermined construction cycle, then the subsequent trailing element that is adjacent to connect the wall of the preceding element is constructed, and it is continuous. The completed underground wall is completed. As described above, since the underground continuous wall is constructed by connecting a plurality of wall bodies as a whole, it is necessary for the joint portion to also maintain the waterproofness as the wall body and surely transmit the stress as an integral structure. is there. (Hereinafter, in the present specification, the vertical joint portion formed along the depth direction in the groove between the adjoining leading element and trailing element is simply referred to as "joint portion".
Will be described. For this reason, various joint structures have been developed and put into practical use that reliably transmit stress between the wall of the preceding element and the wall of the following element of the underground wall.

By the way, at the time of placing concrete of the preceding element, the cast concrete generates a fluid pressure in the form until it hardens, and this fluid pressure acts as a lateral pressure on the ground and the joint portion. The magnitude of this lateral pressure varies depending on the mix of concrete, the pouring speed, the wall thickness, etc., but is usually 10
It can be up to 15 t / m ² . On the other hand, since the thickness of the steel plate used for the partition steel plate is about 9 mm at the maximum, the steel plate alone cannot resist the concrete lateral pressure, and the partition steel plate may be deformed or the partition steel plate itself may be broken. Therefore, conventionally, the partition steel plate is reinforced by various reinforcing structures so as to resist the lateral pressure of concrete.

FIG. 5 shows an example in which partition steel plates installed at both ends of the wall element are connected by tie rods so that the partition steel plates can resist the lateral pressure of concrete. In the figure, the lateral pressure of the cast concrete 50 acts on the partition steel plate 51 as a substantially even load. The end portion 51 a of the partition steel plate 51 is supported by the joint box 53 against this load. The joint box 53 is a temporary member that is embedded to protect the main rebar 54 extending from the partition steel plate 51 when the trailing element is excavated. Further, tie rods 52 made of steel rods are provided at predetermined positions on the partition steel plate 51 at predetermined intervals in the depth direction. The end portion of the tie rod 52 penetrates the partition steel plate 51 and is fixed to the outer surface of the partition steel plate 51 via a fixing nut 55. Tie rod 5 like this
Since 2 is arranged, when concrete side pressure acts on the partition steel plate 51, a tensile force is generated in the tie rods 52 to support the partition steel plate 51 and prevent deformation.

In addition, a reaction material made of assembled steel is arranged in the joint box, and the reaction material and the H-shaped steel are combined to support the intermediate position of the partition steel plate to prevent the partition steel plate from being deformed. Some of them are made of crushed stone or gravel that is filled into the joint to support the steel plate.

By the way, in consideration of the integrity of the completed wall body structure, unlike the general wall body portion, the ordinary stirrup cannot be installed at the joint portion, so that it is necessary to adopt a structure that bears the acting out-of-plane shear force. There is. Further, when the underground continuous wall is used as a main body integrated structure or a basic structure, in-plane shear force is also generated in the depth direction. In the general part of the wall body, this shearing force can be borne by arranging a predetermined shear reinforcing bar, but in the joint part, since the concrete is cut with an edge and placed, the shearing resistance cannot be borne.
Therefore, it is necessary to provide a reinforcing steel material as a predetermined shear resistance element to the partition steel plate that constitutes the joint surface of concrete to make a rigid joint, and to have a structure that reliably transmits the in-plane and out-of-plane shear forces described above. .

As the reinforcing steel material, there are an example in which a stud bolt as a shear connector is welded on the surface of a partition steel plate, or a deformed rebar or shaped steel bent into a loop shape or a lattice shape is welded to the partition steel plate. FIG. 6 shows an example in which equilateral angle steel (angle material) and flat steel plate are combined to form a shear resistance element having a predetermined shape. As shown in the figure, angle members each having a length substantially equal to the wall thickness are welded to both sides of the partition steel plate in the horizontal direction at predetermined intervals. Further, flat steel is fixed to the center of the partition steel plate so as to extend in the depth direction of the wall body. This flat steel bears the out-of-plane shearing force of the wall joint portion and also functions as a water stop plate. As described above, in the conventional joint structure, the structure is determined in consideration of the deformation prevention of the partition steel plate at the time of placing concrete and the function as the out-of-plane and in-plane shear resistance elements.

[0009]

However, in the joint structure described above, when the tie rod is used to prevent the deformation of the partition steel plate due to the lateral pressure of concrete, for example, the wall shape is made to function effectively as a tensile member. Is limited to straight walls and cannot be used as is for corner walls. In addition, when a reaction material is used, it is expected that the reaction material size will increase as the wall depth increases, increasing the material cost and reducing the workability.
Furthermore, when filling crushed stones, it is necessary to take measures to reliably remove the crushed stones from the wall body after construction, and if the wall thickness increases, the amount of crushed stones used will increase sharply, leading to an increase in overall cost.

On the other hand, there are various structural problems when using the conventional reinforcing steel material as the shear resistance element. For example, in a structure in which a stud bolt or a reinforcing bar is welded to a partition steel plate as a share connector, the number of stud bolts and the like used becomes enormous, and it takes a long time to manufacture this reinforcing member. Further, in the structure shown in FIG. 6 in which a plurality of mold steels are combined, the number of welds is large at the time of production, and the welding length is long, which is disadvantageous in terms of cost. In this case, slime is likely to be caught in the shape steel during concrete pouring, which may deteriorate the quality of the wall concrete. Further, in the structure shown in FIG. 6, the stress transmission between flat steel and concrete is achieved only by the adhesive force of the concrete, so that the in-plane shear force cannot be surely transmitted from the flat steel to the concrete.

Therefore, an object of the present invention is to solve the problems of the above-mentioned conventional techniques, prevent the partition steel plate from being deformed during concrete pouring, and sufficiently resist the acting shear force after completion. It is to provide a rigid joint for a medium continuous wall.

[0012]

In order to achieve the above object, the present invention relates to a web extending in a semi-cylindrical shape in the depth direction of a wall of an underground wall, and fixed to a part of the web. Is
At least a shear plate capable of transmitting an in-plane shearing force acting on the wall body to the concrete, and having a shear plate capable of bearing an out-of-plane shearing force acting on the wall body formed at one end thereof; To do.

At this time, it is preferable that the web has a substantially arcuate planar cross-section having a diameter substantially equal to the distance of the composite rebars arranged in the wall body. Further, it is preferable that the shear resistance portion extends in a saw blade shape in the depth direction of the wall body.

[0014]

According to the present invention, the in-plane shearing force acting on the wall of the underground continuous wall can be transmitted to the concrete in a part of the web extending in a semi-cylindrical shape in the depth direction of the wall. Since a shear plate capable of bearing an out-of-plane shearing force acting on the wall body having a shearing resistance portion formed at one end is fixed, the web functions as an arch structure against concrete lateral pressure and resists during concrete pouring. While you can
The in-plane shearing force acting on the wall at the time of completion can be reliably transmitted to the concrete by the shearing resistance portion, and the out-of-plane shearing force acting by the shearing plate can be reliably resisted.

At this time, by making the flat cross-sectional shape of the web into a substantially arc shape having a diameter almost equal to the distance of the composite rebars arranged in the wall body, the arch effect of the web against concrete lateral pressure is most efficiently exhibited. be able to. Further, the shear resistance portion extends in a sawtooth shape in the depth direction of the wall body so that the in-plane shear force can be reliably transmitted to the concrete at the sawtooth portion.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a rigid joint for an underground wall according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a perspective view schematically showing a top portion of a rigid joint 1 according to the present invention.
In the figure, reference numeral 2 indicates a partition steel plate, and this partition steel plate 2 comprises a semi-cylindrical curved web 3 and a T-shaped flange 4 connected to the end of the curved web 3. Further, shear plates 5 extending over the entire length in the depth direction are welded and bonded to both surfaces of the curved web 3 at the central position. The curved web 3 has a curved diameter substantially corresponding to the rebar separation of the main rebar 6 which is a double rebar, has a semicircular planar shape, and has a semicylindrical shape in the depth direction. At this time, the concrete lateral pressure acts on the curved web 3 as a uniformly distributed load directed toward the center of the arc at a predetermined depth, but since the curved web 3 functions as an arc arch structure, it is excellent for the curved web 3. Compressive force is generated, and bending moment is hardly generated. Therefore, the curved web 3 can be designed as a compression member, and its plate thickness can be set to an allowable compression stress in consideration of buckling, and can be made thinner than a partition steel plate having a flat plate structure.

Further, the shear plate 5 fixed to the curved web 3 has a sawtooth shape of an acute triangular shape having continuous outer edges as shown in the figure, and functions as a plate-shaped portion and serves as an out-of-plane shear resistance element at a joint portion. It can resist the acting out-of-plane shearing force, and can also serve as a water blocking plate to block the passage of groundwater and the like at the wall joint. A T-shaped flange 4 is welded to both ends of the curved web 3, and an outer plate 4b is connected to a partition web 4a of the T-shaped flange 4. The outer plate 4b contacts the wall excavation surface,
The rigid joint 1 is adapted to be held in place within the wall. Further, the partition web 4a can hold the main rebar 6 through as shown in the drawing. A tab plate 7 is attached to the end of the outer plate 4b, and the end of the joint box 8 can be connected via the tab plate 7. Thus, the lateral pressure from the concrete is transmitted as a compressive force in the curved web 3 which is the partition steel plate, and is further transmitted to the joint box 8 through the T-shaped flange 4, so that the partition steel plate 2 is reinforced in the joint box 8. It is not necessary to provide a steel material, etc.

FIG. 2 is a plan view and a partial cross-sectional view schematically showing a state in which the rigid joints shown in FIG. 1 are arranged at both ends of the preceding element and concrete is poured. As shown by the arrow in the figure, the lateral pressure of the concrete poured into the wall acts not only on the ground but also on the partition steel plates of the rigid joints at both ends of the element, but the curved web 3 of the partition steel plate is affected by the arch effect. Can withstand working side pressure. Further, the acting side pressure is transmitted to the joint box via the T-shaped flange 4 which is a support portion of the partition steel plate, and the entire partition steel plate is supported by the ground through the crushed stones filled in the clearance. Further, as shown in FIG. 3B, one of the shear plates 5 is surely embedded in the concrete of the preceding element, and the other end of the shear plate 5 is also embedded in the following element (not shown). The shear plate 5 allows the joint portion to have a structure sufficiently resistant to the acting out-of-plane shear force. Further, the in-plane shearing force is transmitted to the concrete through the end face of the plate thickness portion of the saw blade portion formed on the shearing plate 5. As described above, the shear plate 5 according to the present invention can surely resist the in-plane shear force when completed.

3 and 4 are schematic perspective views showing modifications of the above-mentioned shear plate. In FIG. 3, the web 20b of the I-shaped steel, which is the material, is cut into a shape for producing a honeycomb shape, and the flange portion 20a of each shear plate member 20 is joined to the central position of the curved web 3 at the welded portion W and sheared. It shows a modified example of the plate 20. According to this modification, since the flange 20a is already integrally formed with the shear plate 20, the welding to the curved web 3 can be easily performed via the flange 20a.

FIG. 4 shows a modification in which a flat steel plate as a shear plate 21 is cut out at a predetermined interval and the plate ends 21a are alternately bent so as to form a Y shape in a plane and are joined to the curved web 3 at the welding portion W. This is an example. According to this modification, the region of the concrete portion to which the in-plane shear force is transmitted from the shear plate 21 can be made larger, and the shear resistance force of the concrete can be set correspondingly larger, and as a rigid joint. The joint effect of can be improved. Although the joint described above is manufactured at the factory, since the welding portion is almost straight, it can be manufactured in an extremely short time by using an automatic welding machine or the like. Further, there is an advantage that the joint portion can be cleaned easily and surely before the concrete casting of the following element, because the joint shape is simple.

[0022]

As is apparent from the above description, according to the present invention, the arching effect of the curved web improves the stability at the time of construction without the need for a reinforcing steel material, and the wall force is exerted. This has the effect of reliably resisting.

[Brief description of drawings]

FIG. 1 is a partial perspective view showing an embodiment of a rigid joint for a continuous underground wall according to the present invention.

2 is a plan view and a partial vertical cross-sectional view showing an example of an underground continuous wall to which the rigid joint shown in FIG. 1 is applied.

FIG. 3 is a partial perspective view showing a modified example of the rigid joint shown in FIG.

FIG. 4 is a partial perspective view showing another modified example of the rigid joint shown in FIG.

FIG. 5 is a plan sectional view showing an example of conventional concrete lateral pressure reinforcing means for a partition steel plate.

FIG. 6 is an explanatory view showing an example of an out-of-plane and in-plane shear resistance element of a conventional joint portion.

[Explanation of symbols]

 1 Rigid joint 2 Partition steel plate 3 Curved web 4 T-shaped flange 5, 20, 21 Shear plate 6 Main rebar 8 Joint box

Claims (3)

[Claims] 1. A web extending in a semi-cylindrical shape in the depth direction of a wall of an underground wall, and an in-plane shearing force fixed to a part of the web and acting on the wall to concrete. A rigid joint for a continuous underground wall, which comprises at least a shear plate capable of transmitting an out-of-plane shearing force acting on the wall body having a shearable resistance portion formed at one end thereof. 2. The underground continuous wall according to claim 1, wherein the web has a substantially arcuate cross-sectional shape with a diameter substantially equal to the distance of the composite rebar arranged in the wall body. Rigid joint. 3. The rigid joint for a continuous underground wall according to claim 1, wherein the shear resistance portion extends in a saw blade shape in the depth direction of the wall body.