JPH04231599A - Device for applying preload to flexible board under foot of arch used for tunnel excavation - Google Patents

Abstract

PURPOSE: To block sinking of an arch used for excavation of a tunnel and sinking of a protection top rail consisting of micropiles most of which are placed on the arch. CONSTITUTION: A device is designed to apply a preload for a floor 6 apt to bend below legs 3 of an arch in order to block sinking of an arch on which a load is exerted due to the weight of earth situated above a tunnel, which occurs as a result of a protection coping being apt to bend subsequently to excavation of earth below the protection coping supported by an arch. A base consisting of two surfaces to form the flanks is arranged at legs 3 of the arch of a room 8, the surface coupled to the leg has rigidity and a surface 9 placed on a ground has bendability and stretchability. The room 8 is pressurized by fluid and deformed on a ground apt to bend and this constitution blocks sinking of the arch.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for excavating tunnels using protective umbrella technology and to the installation of an arch that continues during operation.

0002

BACKGROUND OF THE INVENTION Among the techniques currently known are so-called protective umbrellas, which are used particularly in unstable soils or in soils subject to landslides.

[0003] It consists of inserting into the ground a row of steel pipes equipped with check valves. These tubes are of the type customarily used for the injection of stabilizing and reinforcing mixtures, primarily cement grouts. The support umbrella is formed by a plurality of micropiles.

This supporting umbrella structure, which is approximately cylindrical in shape,
Helps support the ground above, especially during driving. The support bulk has a truncated conical shape and the micropiles have an average length of 13 meters. Once the first set is completed, it is necessary to insert another row of micropiles in the next 13 meters. The next series of micropiles overlaps the previous micropiles like fish scales.

[0005] For each successive set of piles, it is necessary to remove the soil beneath the previous set. During this operation, previously installed micropiles are uncovered.

[0006] Then, the supporting arch is 1 of the average tunnel.
~2 meters apart, with an average distance of 1 meter. The arch, which contacts the protective umbrella formed by the micropiles, usually consists of two beams of H-shaped cross section, suitably shaped to follow the shape of the tunnel vault. The arch is supported by feet that stand at a temporary excavation level in the ground.

[0007] The weight of the umbrella and the overlying soil is concentrated on the supporting foot when the umbrella is emptied, causing the foot, arch and overlying protective umbrella to sink several centimeters into the ground.

[0008]

SUMMARY OF THE INVENTION It is an object of the invention to provide a device for preventing or suppressing the settling of an arch and therefore of the protective umbrella which rests for the most part on the arch.

[0009]

[Means for Solving the Problems] To achieve the above object, following the excavation of the soil under the structure supported by the arch, the soil overlying the tunnel, which occurs as a result of the flexibility of the structure, is In a device for preloading a flexible floor under the foot of an arch in order to eliminate or prevent weight-loaded arch settlement, the foot is provided with a chamber partitioned between the feet. A base consisting of two surfaces is provided, and the surface connected to the feet is rigid, while the surface resting on the ground is flexible. It is sufficient to create a deformation and increase the reaction force to resist the arch's subsidence.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below with reference to embodiments shown in the drawings.

Referring to FIGS. 1, 2 and 3, the rows of micropiles constitute a protective umbrella 1 with an underlying series of arches 2 supported by feet 3. Only during the final stage of perforation excavation, when the reinforcing pile 4 is carried out and the beam 5 is installed, the arch is attached to the flexible floor 6 (Fig. 7), and the foot 3 of the arch is attached to the flexible floor 6 by the plate 7. Posted. The flexible floor 6 is relatively soft,
and has low load capacity.

In order to prevent the plate 7 (FIGS. 4, 5, 6) from sinking into the ground, a chamber 8 is located below the plate 7. This chamber 8 is defined between a pot-shaped plate 7 and a flexible flexible sheet metal 9, preferably made of special steel.

A sheet metal 9 is welded to the edge of the plate 7 so as to form a watertight seal and has a concave shape in the inactive state (FIG. 4). The plate 7 has a grouting inlet valve 10 with a slide 11. The plate also has ventilation holes with caps 12 and support beams 1 of the arch feet 13.
3 is welded to the upper part of plate 7.

During work, the arch 2 and the two side legs 3
shall be placed in their proper positions. Then, the arch is connected to the side foot using the joint flange 14,
And the correct position of all the arches must be checked. Finally, attach the arch to the pile of protective umbrellas. Several wedges must be hammered into the bottom of board 7. For this purpose, edge 15 of plate 7 (
Figure 4) is suitably dimensioned to resist stress.
To prevent damage to the adjacent sheet metal 9 and chamber 8.

At this point, grout is injected through conduit 10 to fill chamber 8 while allowing air to escape through vent 12. As soon as the grout starts coming out of the vent, close the vent while continuing to spray the grout. As a result, the sheet metal 9 assumes a convex shape (see Figure 6) and pushes against the underlying ground. As grouting continues, the pressure within chamber 8 will eventually become sufficient to counteract the sinking load. Subsidence is avoided or reduced.

Once the injection is complete, the slide 11 is closed and the grout hardens over time to form a hard homogeneous block.

Among the various injection methods possible, one uses a single line for each leg and a single actuator with a respective pressure gauge to check the pressure of the injected grout. It is possible to inject two or three arches at once, depending on 4 to 6 feet. In this way, a constant, gradual and simultaneous thrust force is obtained on all loaded arches. After this, the already installed arch can be stiffened by jetting concrete or using a similar technique (sprayed concrete).

[0018] Once this operation is complete, excavation can continue. The reinforcing and supporting columns 4 can be carried out later and the ground can then be excavated down to the level 16 of the lower arch and the beams 5 can be fitted and connected to the holes 17 in the plate 7 (FIG. 5). .

[0019]

The preloading device according to the invention makes it possible to prevent the arch from sinking and therefore the protective umbrella which rests largely on the arch.

[Brief explanation of the drawing]

1 is a perspective view of the protective umbrella, with the dash-dotted line being the axis of the arch, but also showing the reinforcing struts for supporting the arch after its installation; FIG.

FIG. 2 is a cross-section of the arch under the protective umbrella and the lateral reinforcing and supporting elements installed after installation of the arch;

FIG. 3 is a longitudinal section through the underlying arch and protective umbrella with varying radii to follow the slope of the pile;

4 is a cross-sectional view taken along the line IV-IV of FIG. 5 and a front view of the support plate of the arch foot with the device; FIG.

5 is a cross-sectional view taken along the line V-V in FIG. 4 and a plan view of the support plate of the arch foot with the device; FIG.

6 shows the pressurization of the chamber following the layout of FIG. 4; FIG.

FIG. 7 is a cross-sectional view of a tunnel incorporating a device according to the invention and having an arch supported by the foot;

[Explanation of symbols]

1 Protective umbrella 2 Arch 3 feet 6. Flexible floor 7 Board 8 Room 9 Sheet metal 10 Slide valve 12 Ventilation hole

Claims (6)

[Claims] Claim 1: A structure supported by an arch (2) (
1) to eliminate or prevent the settlement of the arch loaded by the weight of the soil above the tunnel, which occurs as a result of the flexibility of the structure (1) following the excavation of the soil under the arch. The flexible floor under the feet (3) of (2) (
6), the foot (3) is provided with a base consisting of two surfaces (7, 9) which partition a chamber (8) between them, and a surface connected to the foot ( 7) is rigid, and the surface (9) resting on the ground is flexible, and the chamber (8) is connected to a fluid supply means for deforming the surface (9) that presses against the ground below. A preloading device characterized by: 2. Device according to claim 1, characterized in that the chamber (8) is closed and the flexible surface (9) is made of flexible sheet metal. 3. Device according to claim 1, characterized in that the fluid injected into the chamber (8) is cement grout. 4. The conduit supplying the fluid to the chamber (8) is provided with a slide valve (10), while the rigid plate (7) has vent holes (12) for exhausting the fluid from the chamber. 2. The device according to claim 1, further comprising: ). 5. Claim characterized in that fluid is injected into the chamber (8) until the pressure in the chamber (8) is equal to the pressure exerted on the foot (3) by the weight of the arch (2). A method of applying a preload using any one of the devices 1 to 4. 6.Characterized in that several arches (2) are acted upon simultaneously with gradual pressure increases so as to distribute an equal thrust on both the flexible floor (6) and the opposing arches. The method of claim 5.