JPS61179999A - Method of excavating tunnel to rock - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention reduces the risk of a tunneling shield becoming stuck in rock weakened by rock deformation (compression and expansion of sediment) and at the same time reducing the risk of jamming in tunnel linings. This relates to a method of lowering pressure.

Excavation of a tunnel changes the stress in the rock surrounding the tunnel and causes the rock to deform. The deformation of rock into the tunnel is usually a few millimeters in hard rocks, but can be tens of centimeters in weak rocks. Rock deformation is time-related and if not handled in the correct manner, weak rocks will deform unacceptably large amounts or impose unacceptably high loads on tunnel supports. Modern tunneling requires consideration of this and the New Australian Tunneling Method (NATM) in the design of tunnel and cave supports.
Au5tralian Tunnel 1 ing
Method) takes into account more systematic principles.

It is generally known that geological and petrophysical principles will reduce the load on a tunnel support if the supported rock mass is deformed to such an extent that its shear strength is exerted.

Means to Solve the Problem A unique feature of the present invention is that it tunnels through weak rock by filling the gap between the shield and the rock with a specially selected fluid material that rapidly expands, hardens, and compresses. It's in the way you dig. The expanded and hardened material reduces the stress in the rock closest to the tunnel wall and transmits only this reduced stress into the tunnel. At the same time, the expanded material helps seal the tunnel against water and gas ingress.

The present invention relates to a novel method for substantially reducing the pressure from weak rocks on shields used in tunneling, as well as reducing the pressure on the tunnel lining.

The invention is to fill the void between the shield and its surrounding rock with a material that can expand, harden and deform.

The gaps formed between the shield 11 and the rock 3 and between the tunnel support and the rock are filled with a particularly selected expanding material. The deformation and strength properties of this material allow for controlled deformation of the shield and tunnel supports to reduce the stress exerted on the rock.

The present invention reduces the risk of shield jamming due to crushing by deforming rock, and also allows tunnel supports to be designed to be subjected to rock pressures that are significantly reduced.

The invention will now be described with reference to the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is based on the interaction between the response of a rock to removal of a load and the response of a support to a load, as shown in the accompanying drawings. FIG. 1 shows how the pressure from the rock decreases over time to a minimum value before the rock subsequently ruptures due to increased pressure. Figure 2 shows an example of how the rock can be allowed to deform to a certain extent before the pressure on the tunnel supports increases rapidly, and how the load on the supports can increase to a maximum value before the supports collapse. be. The overlap of these curves provides the basis for the proper design of supports that are installed at the correct time and with sufficient strength, as shown in FIG.

The line marked with a bar indicates that contact between the expanding rock and the support occurs quickly, and that the support must be designed to withstand large loads in order to prevent the support from collapsing. "
The line marked by Tsukasa is after the exposed rock surface has split, indicating that contact has occurred too late. The line marked by the threshold is the line of best fit, which means that if contact between the rock and the support occurs at a reasonable time, the lining can be designed for the minimum load and has a large safety margin. Show that you can.

In weak rocks, the standing time (the time from when the tunnel is excavated until the unsupported rock collapses) is very short, meaning that the deformation occurs quickly and the shield becomes immobile due to the frictional force generated by the pressure of the rock (Figure 4). reference).

Referring to FIG. 4, the support behind the shield 1 of the tunnel boring machine is generally formed of prefabricated segments 2 which, when assembled, form a complete cylindrical ring. In current tunnel excavation methods, cement mortar, pea-sized gravel or similar hard material is driven between the support 2 and the rock 3 to create the necessary overall action and to evenly transfer the load from the rock to the support.

Additionally, complete lining rings can be cast in place. All of these supports are so rigid that the pressure exerted by the rock on the supports can be very high (between the lines in Figure 3). The present invention utilizes a special material that is implanted between the rock and the support. In particular, materials suitable for individual tunnel excavation conditions harden quickly and can be deformed by transferring part of the load applied by the rock (see Figure 5).

The substance 6 fills the void created between the rock 3 and the shield 11 protecting the excavator. The same material "6" is of the same thickness as the outer shield 11 of the lining or support 2 and fills the voids present behind the shield 11.

This material and the system that injects it have the following characteristics: In other words, (]) deformation characteristics that can be adapted to 11 types of tunnel excavation conditions and that can optimally design a tunnel support by deforming the material as the rock moves and gradually increasing the load and transferring it to a relatively rigid tunnel support. Strength.

(2) The injected substance can expand and fill the gap between the shield and the lining.

(3) The injected material does not retard the advancement of the tunneling shield due to increased friction. This is accomplished by appropriate design of the shield and its associated machinery and systems.

(4) The injected material is stable and durable, and maintains its strength over time by preventing increased deformation of the rock and the corresponding increase in load on the tunnel support.

(5) The injected material will not dissolve in water and will not be chemically disturbed by gases or salts present in the rock even after the injection is finished.

The characteristics of the injected material cannot be specified in further detail than those described above without explanation of the rock condition and quantitative measurements. Several currently suitable classes of materials are formulated to produce varying degrees of compaction, such as polyurethane.

The overall load response as a function of the time of engagement of the injected material 6 and the tunnel support 2 is shown in FIG. The symbols used in Figure 6 indicate the following. Ps = stabilization load, i.e. the required load of the injected mass to stabilize the support.

Popt = Optimal rock load to be applied to the support.

Pkap = ultimate load capacity of support.

Po = maximum rock load.

topt=<time when the rock load is at its minimum just before shifting.

tinj = time to start injection.

tforst = time at which the support begins to take on the load.

The following conditions are necessary to carry out the present invention.

That is, as the tunnel is excavated, the rock is stressed, and this stress deforms the rock into the tunnel cavity.The surface of the tunnel is covered by either the shield 11 or a lining or support 2 erected or driven at the trailing edge of the shield. It is strengthened to resist this deformation.

The material filling the outer void between the shield 11 and the tunnel support has properties tailored to the properties of the rock in contact with it. Relevant properties of this material are the rate of increase in strength over time, strength properties, elastic properties, creep properties and water permeability.

It is essential that the tunnel boring machine 5 (or cutter head in the case of a tunnel poling machine), the shield 11 and the lining segment 2 are designed to carry out the method described above. In particular, the diameter of the shield must be designed to leave sufficient space between the shield and the rock to achieve the desired thickness of the injected material.

[Brief explanation of the drawing]

Fig. 2 is a graph showing the load of rock transferred to the rigid support installed at different times after excavation; Fig. 2 is a graph showing the relationship between the reaction load applied to the tunnel support K and time; Fig. 3 The figure is a graph showing the relationship between the load applied to tunnel supports and time, and shows the criteria for designing tunnel supports. Figure 4 is a schematic cross-sectional view of a conventional excavation head used in a tunnel polling machine (TBM). , FIG. 5 is a schematic cross-sectional view of a tunnel polling machine performing work involving the injection of material outside the shield according to the invention, and FIG. 1 is a graph showing the relationship between the total load of material and the total load curve of the tunnel support; (5 other people)

Claims (1)

[Claims] During excavation, the gaps formed between the excavated rock surface and the shield 11 and between the tunnel support are filled with a material 6 that expands when injected and is deformable after hardening, thereby reducing the amount of rock that is placed between the shield and the tunnel support. A method of excavating tunnels in rock, characterized in that it reduces the pressure and, as a result, prevents the shield from becoming stuck due to excessive friction and reduces the strength required for tunnel support.