JP4017777B2 - Tunnel construction method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a construction method (URT = Under Railway / Road Tunneling construction method, etc.) for constructing a tunnel that is three-dimensionally crossed under a track or road.
[0002]
[Prior art]
As a method of constructing a tunnel that intersects three-dimensionally under a railroad or road, instead of the conventional construction method of a lining body made of cast-in-place concrete, a hollow box-shaped tunnel lining element is sequentially applied to the ground. The URT (Under Railway / Road Tunneling) method that constructs a tunnel by excavating and removing the soil inside the element connected body after arranging multiple elements in an approximately gate shape by connecting them to each other. Known (Japanese Utility Model Publication No. 8-3516).
[0003]
FIG. 4 shows a tunnel constructed in the ground G using elements. In this tunnel, a long hollow box-shaped steel element 1 is pushed horizontally with respect to the ground G so as to be perpendicular to the lining section, whereby a plurality of elements 1 are connected to a vertical portion V and a horizontal portion H connecting them. The PC cable (high-tensile steel wire) 3 is inserted into a hole (not shown) provided in the joint portion 2 of each element 1, and the inside of each element 1 and The concrete 4 is filled and placed in the space of the joint portion 2 of the adjacent element 1, and after the concrete 4 is hardened, the PC cable 3 is tensioned to introduce a compressive force between the elements 1, so that the element coupling body is a face plate. After that, it was constructed by excavating and removing the earth and sand inside the element coupling body.
[0004]
The PC cable 3 is arranged with a predetermined interval in the longitudinal direction (propulsion direction) of the element 1 and is routed along a portion where a tensile force acts on the element connection body so as to resist surrounding earth pressure. Has been. In addition, the role of the element 1 in this construction method is the following four.
(A) Means for safe construction by the element propulsion method without causing the face to collapse, deformation of the surrounding ground, or the like.
(B) A bending strength member in a direction orthogonal to the high-tensile steel wire secures the bending strength of the entire tunnel as a pipe, and at the same time, distributes the concentrated load applied to the tunnel lining surface.
(C) Reinforcing cracks as a unit block and protecting against deterioration of concrete and corrosion of high-strength steel wires.
(D) Concrete formwork for forming the lining body.
[0005]
The structure of the face plate formed by the above-described strengthening method using high-tensile steel wire (PC cable) (hereinafter referred to as “PC lateral fastening method”) has two-way structural characteristics. That is, in the axial direction of the element 1 (axial direction of the tunnel), the bending strength of the element 1 as a beam member is obtained, and in the direction orthogonal to the element 1, a concrete block reinforced in a rectangular shape with a steel plate is laterally penetrated. It has bending strength as a prestressed concrete member that is tensioned with high-strength steel wire.
[0006]
The load to be designed to secure the space of the cross section of the tunnel is the load perpendicular to the plate surface of the slab that is the lining body. Goes forward to. In a tunnel having a rectangular cross section, the load on the ceiling surface and the floor surface is supported by the side wall, and the load on the side wall surface is supported by the ceiling surface and the floor. For this reason, as a practical expedient design method, it is assumed that a flat frame is formed by rounding the tunnel as a shape created by the flow of shear force into unit lengths, which has sufficient strength against external pressure. It is reasonable to design to have The PC cable is arranged along this shape.
[0007]
[Problems to be solved by the invention]
By the way, the weak point of the tunnel lining body by the face plate structure formed by the PC horizontal fastening method is in the joint portion (joint joint) of the element. The element is a block whose periphery is reinforced with a steel plate, but the steel plate that covers the surface is discontinuous at the joint, so if a large bending stress is applied to the face plate, there may be an opening along the joint . The stress of the member due to the bending stress has a zero point inside the cross section of the surface slab, one is pulled, and one is compressed, and linearly changes as a large value as it approaches the surface.
[0008]
The key point of the structural design is to prevent the opening of the joints from occurring, or to limit the fine width to prevent a harmful state from occurring even if the opening occurs. It also prevents the concrete from collapsing due to compression stress reaching the limit. As these means, a method of prestressing a member is known. That is, a tension force is applied to the PC cable arranged at a position off the center of gravity of the member cross section, a bending stress opposite to the bending stress caused by the assumed load is added, the compression and the tension are offset, and the tensile stress degree This is a method of controlling the degree of compressive stress to a predetermined value or less.
[0009]
When the bending stress due to the load increases, the prestressing force is increased in terms of design, but eventually the limit is reached and the cross section of the member must be changed to be thicker. In the URT method, there is a restriction that the cable placement and the tension work are performed by an operator entering the element.
As described above, the stress due to the bending stress is concentrated on the surface layer portion of the surface slab, so it is extremely inefficient to apply prestress to the central portion. Therefore, if the thickness of the member is increased, the cross section of the inefficient central portion is also increased, and an extra PC cable is further required.
[0010]
For this reason, a cavity prestressed concrete panel (JIS A 6511) is known as an efficient bending member. As shown in FIG. 5, this is intended to reduce the weight of the member by providing continuous holes 6 along the direction of the PC cable 3 in the central layer of the plate, and at the same time, try to effectively apply the introduction prestress.
[0011]
By the way, as shown in FIG. 6, when the direction of the continuous hole 5 of the cavity prestressed concrete panel is changed by 90 degrees in the direction orthogonal to the shearing force, the surface layer portion left by the hole defect is obtained when the hole diameter is large. There is a risk of oblique cracking based on shear force.
In the bending member, the portion close to the surface layer mainly bears a large axial force due to bending, and the trunk portion near the cross-sectional centroid mainly bears a large amount of shearing force.
[0012]
In FIG. 5, since any part in the member direction (load transmission direction) is a continuation of the same cross section, the body part can mainly handle shear force transmission. In this way, when the middle layer portion is cut and the cross section is concentrated on the surface layer portion, the division of roles becomes clearer.
In FIG. 6, since the cavity appears in a form that divides the member direction (load transmission direction), the shearing force that has been transmitted through the body part moves the transmission path to the surface layer, so the surface layer part must bear with the axial force. Thus, the stress is greater than in the case of FIG.
[0013]
In consideration of the above circumstances, the present invention can efficiently introduce a compressive force only to a necessary portion of the cross-section of the joint portion, resulting in reducing the diameter and number of high-strength steel wires. It aims at providing the construction method of the tunnel which can aim at improvement of construction nature and economical efficiency.
[0014]
[Means for Solving the Problems]
According to the first aspect of the present invention, the hollow box-shaped elements are propelled in the direction orthogonal to the lining section with respect to the ground on which the tunnel is to be constructed. Embedded in a substantially gate shape composed of a horizontal portion to be connected, and at least elements arranged in a face plate shape to constitute the horizontal portion are penetrated by a high-tensile steel wire in the arrangement direction of the element, Concrete is filled in and placed in the joint portion space of the element and the adjacent element, and after the concrete is hardened, the high-tensile steel wire is tensioned to introduce a compressive force between the elements, thereby connecting the elements. In the construction method in which the tunnel is constructed by excavating and removing the soil and sand inside the element coupling body, Characterized in that a cushion material section.
[0015]
In this method, the cushion material is interposed in part of the joint part of the element, which is a weak point in the structure, so the compressive force due to the high-strength steel wire is not introduced in the part with the cushion material, and the remaining part is the remaining Sorted into a solid cross section. Therefore, the compression force can be positively increased particularly in the portion where the introduction of the compression force is necessary. That is, the compressive force can be efficiently introduced into the necessary part.
[0016]
The invention of claim 2 is characterized in that, in claim 1, the cushion material is applied to a part of the side wall of the joint portion of the element over the longitudinal direction of the element, and then concrete is placed.
[0017]
In a horizontal slab section, the stress changes in the depth direction (height direction) of the slab. Therefore, the cushion material is pasted in the longitudinal direction (propulsion direction) of the element at a specific position in the depth direction, and concrete is placed. Thereby, at a certain level (position in the height direction of the cross section) of the cushion material, the axial force by the high-tensile steel wire is not transmitted, and the portion is distributed to a solid cross section.
[0018]
The invention of claim 3 is characterized in that, in claim 1 or 2, a foam is used as the cushion material.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 is a cross-sectional view of a part of a tunnel constructed by using the method of the present invention, FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1, and FIG. 3 is a front view of an element connection body of the tunnel. It is.
[0020]
As shown in FIG. 3, in this construction method, a plurality of elements 1 made of hollow box-shaped steel having a rectangular cross section are horizontally propelled in a direction orthogonal to the cross section of the ground G on which a tunnel is to be constructed. The element 1 is embedded in a substantially gate shape including vertical portions V on both sides and horizontal portions H connecting the vertical portions V. In this example, a double box format is used.
[0021]
In this case, as shown in FIG. 1, the element 1 constituting the horizontal portion H is formed by integrating the upper surface steel plate 1 a, the lower surface steel plate 1 b, and the left and right side surface steel plates 1 c into a rectangular shape. A cushion material 5 made of a foam (a foamed polystyrene plate or the like) is pasted on the outer surface of a side steel plate (side wall) 1c constituting the joint portion 2.
[0022]
In this example, it is an intermediate portion in the height direction. However, since the method of generating tensile stress differs depending on the position of the elements 1 in the arrangement direction, the height to be applied depends on the position of the elements 1 in the arrangement direction. Change the size. The cushion material 5 is continuously pasted over the length direction of the element 1 at a predetermined position in the height direction as shown in FIG.
[0023]
Next, the PC cable 3 is penetrated by inserting the elements 1 arranged in a face plate shape in the horizontal portion H through the holes 7 of the side surface steel plates 1 c of the elements 1. A plurality of PC cables 3 are arranged at intervals in the length direction of the element 1.
[0024]
In this state, concrete 4 is filled and placed in the interior of each element 1 and in the space of the joint portion 2 between adjacent elements 1. When the concrete 4 is hardened, the PC cable 3 is tensioned to introduce a compressive force between the elements 1 so that the horizontal portion H of the element coupling body is integrated into a face plate shape.
[0025]
At this time, since the cushion material 5 is provided in a part of the joint portion 2 of the element 1 which is a weak point in the structure, that is, a part of the cross section where the compression force is introduced, the compression force by the PC cable 3 is generated in a portion where the cushion material 5 exists. It will not be introduced. In this way, by reducing the concrete cross-sectional area that transmits the axial force of the joint portion 2, a larger compressive force can be introduced into the remaining limited cross-section. In this case, a large compressive force is positively introduced into the upper and lower cross sections of the cushion material 5 which are the remaining dense cross sections.
[0026]
After that, the process is completed by excavating and removing the sand inside the element coupling body and penetrating the tunnel.
[0027]
In this construction method, it is possible to effectively introduce the compressive force to the cross-sectional portion where the compressive force should be originally introduced. Therefore, it is necessary to take measures such as increasing the girder height of the element as a measure against insufficient axial force. It can be lost. In addition, since it is possible to save the amount of the PC cable 3 to be arranged (cross-sectional area × number), it is possible to reduce the labor when the operator enters the element 1 and inserts or tensions the PC cable 3. It is possible to improve work efficiency and economy.
[0028]
In the above construction method, in particular, the element 1 constituting the vertical portion V uses a structure in which the inner space of the upper and lower elements 1 is in a communicating state with the upper and lower surfaces of the element 1 as a lattice plane in relation to filling concrete inside. . In addition, the element 1 is provided with a truss reinforcement member or a lattice structure having a lattice structure inside as required so as to withstand a load or a propulsive force.
[0029]
In addition, the cushion material is not limited to the horizontal portion H of the gate-shaped element coupling body, but can be applied to any surface plate structure on which bending acts, including a curved surface having a circular cross section.
[0030]
【The invention's effect】
As described above, according to the first aspect of the present invention, since the cushion material is provided in a part of the cross section of the joint portion of the element where the compressive force is introduced, the compressive force generated by the high-tensile steel wire is applied to the portion where the cushion material exists. Is no longer introduced, and the compressive force corresponding to that amount can be intensively introduced into the originally required cross section. As a result, the compressive force can be effectively introduced into the necessary cross section, the axial force can be increased, and there is no need for extra measures such as increasing the beam height of the element. In addition, by increasing the axial force, the amount of high-strength steel wire can be reduced, and accordingly, labor for inserting and tensioning high-strength steel wire can be reduced, and economic efficiency can be improved. .
Further, in the construction method of the present invention, since a thin cushion material is used, a place where there is a risk that the oblique crack crosses is limited, and this place is surely reinforced by the steel plate of the element. That is, although the steel plate portion of the element is interrupted in a slit shape, the missing portion is thin, the joint portion is narrowly limited, and sufficient reinforcement can be obtained by covering with engagement of the steel plate and the joint. There is no problem that stress is increased as compared with the conventional case in which continuous holes are formed.
[0031]
According to the invention of claim 2, the cushion material is applied to a part of the side wall of the joint portion of the element over the longitudinal direction of the element and then the concrete is placed. It can be done easily. As the cushion material, it is preferable to use a resin foam or the like as in the invention of claim 3.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view seen from the front of an element joint portion of a tunnel constructed by a method according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along the line II-II in FIG.
FIG. 3 is a front view of a tunnel constructed by the construction method according to the embodiment of the present invention.
FIG. 4 is a cross-sectional view seen from the front of a tunnel constructed by a conventional construction method.
FIG. 5 is a schematic perspective view of a prestressed concrete plate for explaining the structure of the prestressed concrete plate provided with a PC cable.
FIG. 6 is a schematic perspective view of a prestressed concrete plate for explaining the structure of the prestressed concrete plate provided with a PC cable.
[Explanation of symbols]
1 Element 2 Joint 3 PC cable (high tensile steel wire)
4 Concrete 5 Cushion material G Ground H Horizontal part V Vertical part

Claims (3)

By advancing each hollow box-shaped element in the direction perpendicular to the lining section to the ground on which the tunnel is to be constructed, a plurality of elements are roughly composed of a vertical part on both sides and a horizontal part connecting these vertical parts. A high-strength steel wire is penetrated in the arrangement direction of the elements through the elements embedded in the gate type or box type and arranged at least in the form of a plate to form the horizontal portion, and in this state, the inside of each element and Concrete is filled and placed in the joint space of adjacent elements, and after the concrete hardens, the high-tensile steel wire is tensioned to introduce a compressive force between the elements, and the element connection body is formed into a face plate shape. In the method of building a tunnel by excavating and removing the earth and sand inside the element coupling body,
A tunnel construction method characterized in that a cushioning material is provided on a part of a cross section of the joint portion of the element where a compressive force is introduced. 2. The tunnel construction method according to claim 1, wherein the cushion material is applied to a part of the side wall of the joint portion of the element over the longitudinal direction of the element, and then the concrete is cast. The tunnel construction method according to claim 1 or 2, wherein a foam is used as the cushion material.

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