JPS6354877B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a prestressing method for tunnel construction. Tunnel structures include general tunnels used for railways, roads, humanity, etc.
It is broadly divided into waterway tunnels used for power generation waterways, water supply and sewage systems, etc. In general tunnels, except in special cases such as during construction, after the tunnel construction is completed, the pressure applied to the tunnel structure is mainly external pressure due to the thickness of the earth cover, surrounding geology, groundwater pressure, etc., and is applied from inside the tunnel. Almost no internal pressure is generated.
In addition, waterway tunnels are classified into unpressure waterways that flow while maintaining a free water surface and pressure waterways that have no free water surface.
In particular, pressure waterways require a strong lining method in geological conditions with low ground reaction force, so when constructing tunnel structures with internal pressure, conventionally concrete, reinforcing bars, or steel plates were used. A shape with an excavated cross section that can withstand the internal pressure used is constructed. In this case, the forces generated on the cross section of the tunnel structure are an axial tensile force due to internal pressure and an axial compressive force due to external pressure.The axial tensile force due to internal pressure increases in proportion to the tunnel cross-sectional diameter, In waterway tunnels, in addition to the thickness of the earth cover and the strength of the surrounding ground, the axial tensile force due to internal pressure is greater than the axial compressive force due to external pressure. For this reason, an increase in the thickness of rolled concrete and reinforcing materials is required, and concrete-based materials are often used as tunnel lining materials, and reinforcing bars and steel plates are often used to prevent cracking under tensile forces. However, there are many problems with the placement and construction of reinforcing bars and steel plates, and as a result, cracks often occur in waterway tunnel structures, damage to concrete due to water leakage from small cracks, and corrosion of reinforcing bars and steel plates. Holding costs will be significant. The present invention provides a prestressing construction method for tunnel structures that solves the above-mentioned problems. Next, the present invention will be explained based on the drawings. Figure 1 shows an example of the conventional construction method. An appropriate number of notches 10 having a sufficient size are provided in the rolled concrete 1 to be cast around the circumference of the tunnel excavation cross section in order to attach the tension fixing fittings 5 and the tension jacks 3, and the PC steel wire 6
This is a prestressed construction method in which a PC cable 2 consisting of a cable and a sheath 7 is arranged. When introducing the prestress, the axis of the tensioning jack 3 at the tensioning end 4 and
It is necessary to match the axes of PC cable 2,
Further, since the tension end 5 has a cross-sectional shape that can withstand stress concentration, the tension end 5, where the maximum tension force is concentrated, is required to have a considerably large cross-section. Furthermore, when a general structure has a wide space, there are relatively few restrictions on the structure of the tensioning end and the space for tensioning. Furthermore, the tensioning jack notch 10 is provided on the circumference of the tunnel excavation cross section at a predetermined excavation cross section, which results in a major change in the tunnel excavation method, which is economically expensive. FIG. 2 shows an embodiment of the construction method according to the present invention.
Rolled concrete 1 to be placed on tunnel excavation cross section
A PC cable 2 composed of a PC steel wire 6 and a sheath 7 is arranged around the circumference of the tunnel cross section, and an appropriate number of tension fixing fittings 7 are installed in advance in the rolled concrete 1. 9, and tension the PC steel wire 6 in the sheath at both ends 5 with the tensioning jacks 3 through the ladder-shaped tensioning auxiliary fittings 8 supported by the lining metal fittings 11. After PC cable 1 has hardened to a predetermined strength, align the axes of the PC cable 2 and the tensioning jack 3 so as to apply an axial compressive force that can withstand the axial tensile force, and then tighten the tensioning jack 3 with the fixing fitting 9. Fixed under tension, the PC cable 2 is filled with cement grout material, and the fixing metal notch 10 is
A non-shrinkable material is filled inside. Therefore, according to this construction method, the cutout portion 8 can be minimized. FIG. 3 shows another embodiment of the construction method according to the present invention. This construction method is similar to that shown in Fig. 2, without providing the notch 10 in the rolled concrete 1, and by installing the fixing metal fitting 9 between the tensioning metal fitting 8 and the tensioning jack 3.
Attach the PC cable 2 temporarily and connect the PC cable 2.
This is a construction method in which a pre-forced grouting material is injected and fixed, and then the fixing fitting 9 is removed and a predetermined prestress is introduced. FIG. 4 shows a construction method in which the tensioning fittings shown in FIG. 3 are made into triangular shapes 12, and the PC steel wire 6 is tensioned individually by the tensioning jacks 3. As described above, according to the present invention, in the construction of a hydraulic tunnel structure, the cutouts for fixing fittings in the conventional reinforced concrete or steel plate lining method can be minimized or eliminated.
By tensioning the PC cable, it is possible to prevent cracks from occurring at the notch, and there is no need to place the rolled concrete thicker than necessary, and it is easy to introduce durable and watertight prestressing, making it economical. It is effective.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a conventional prestressing method for a tunnel structure, and FIGS. 2 to 4 are cross-sectional views of a prestressing method for a tunnel structure according to the present invention. 1: Rolled concrete, 2: PC cable,
3: Jack for tension, 5: Fixing end for tension, 6:
PC steel wire, 7: sheath, 8: auxiliary metal fitting for ladder-shaped tension, 9: fixing metal fitting, 10: notch, 11: lining hardware, 12: auxiliary metal fitting for triangular tensioning.

Claims (1)

[Claims] 1. A PC cable made of a PC steel wire and a sheath is arranged around the circumference of a tunnel excavation cross section, and rolled concrete with an appropriate number of notches for attaching fixing metal fittings is placed. After hardening to a high strength, the prestressed concrete is given a predetermined prestress by tensioning the prestressed concrete wire at both ends with tensioning jacks via tensioning auxiliary fittings supported by lining metal fittings. A prestressing construction method for tunnel structures characterized by holding the PC cable with a fixing fitting attached to the notch, filling the notch with a non-shrinkage concrete material, and filling the PC cable with a cement grout material. 2 A PC cable composed of a PC steel wire and a sheath is placed around the circumference of the tunnel excavation cross section, and rolled concrete is placed, and after hardening to a specified strength, an appropriate number of tension cables supported by lining metal fittings are placed. The prestressed concrete wire is tensioned with a tension jack via the auxiliary fitting to give the pre-stressed concrete a predetermined prestress, and is temporarily attached using the tensioning auxiliary fitting, and the PC cable is filled with early-strength grout material. A prestressing construction method for tunnel structures, which is characterized by removing temporary attachment after fixing. 3. The prestressing method for tunnel structures according to claim 2, wherein the tensioning auxiliary fittings are triangular in shape, and each tensioning jack is used to tension the PC steel wire.