JP2626277B2 - Construction method of tunnel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing a tunnel for modifying a ground around a front side of a face into a high-strength vitreous consolidated arch prior to excavation of a face.

[0002]

2. Description of the Related Art When a tunnel is excavated on unconsolidated or soft ground by using a mountain tunnel method, it is intended to prevent collapse of the top of the tunnel pit or sinking of the ground surface and to promote the independence of the face. To be improved. Conventionally, as this improvement method, for example, a method of injecting a special solution such as jet grout around the excavated cross section or a method of injecting a solution using a hollow bolt is generally performed. There was a problem described in.

[0003]

First, in this method, there is a problem that soil and groundwater are contaminated by a chemical solution. Even if this contamination problem can be neglected, the injection amount and injection range of the chemical solution are affected by the permeability and cracks of the ground, and it is difficult to accurately predict and manage the contamination. For this reason, for example, there have been problems in safety due to lack of expected improvement effects, and conversely, problems in economics and construction time due to an unnecessary increase in the amount of chemical solution injected.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a method for constructing a tunnel capable of transforming the ground itself around the tunnel into a high-strength ground without using a chemical solution. I have.

[0005]

In order to achieve the above object, a construction method according to the present invention comprises, prior to excavation of a face, forming a circumferential shape of a predetermined excavation cross section at least toward the ground at the upper front side of the face. A plurality of electrode rods are penetrated at predetermined intervals along, and a current is caused to flow between the electrode rods to generate heat by heating the ground portion located between the electrode rods and melt it into a glass. By cooling, a vitreous compact is formed in an arch shape.

[0006]

In the above construction method, the arch of the vitreous solid formed inside the ground along the planned excavation cross-sectional shape has extremely high strength and prevents collapse of the top of the tunnel pit and sinking of the ground surface. Act as a permanent structure for.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIGS. 1A and 1B show a tunnel construction method according to the present invention.

The tunnel tunnel 1 in the figure is constructed by a mountain tunnel method. As is well known, this mountain tunnel method is a method of drilling a face 1a of a tunnel 1 with a rock drill, blasting the face 1a and crushing the face 1a. Prior to the above-mentioned excavation work, the method of the present invention improves at least the ground E on the upper side of the tunnel pit 1. First, the circumference of the planned excavation section A is directed toward the ground E on the upper side of the face 1a. A plurality of conductive holes 2 are cut obliquely upward at predetermined intervals according to the shape.

The length and angle of the guide hole 2 are set to at least several meters to several tens of meters in consideration of the amount of one excavation and the thickness of the ground E to be improved. Further, it is desirable that the drilling interval of each conductive hole 2 is set to about 1 to 2 m to about 7 to 8 m in consideration of resistance between electrodes described later.

After the drilling operation is completed, the electrode rod 3 having a low electric resistance is inserted into each of the conductive holes 2. Then each electrode rod 3 and several thousand
A high-current generator 4 of KW power is connected alternately between adjacent electrode rods 3, and then the device 4 is turned on and a large current is applied. Joule heat of 1000 ° C. or more is generated due to the resistance at the site of the mountain E, and the heat melts the silicon component in the soil contained in the substantially elliptical area surrounded by the oblique line in the figure. When the current is cut off in the molten state, the molten part cools down, and the arch of the glass-like solidified body 5 having a predetermined thickness and length integrated with each other along the hatched portion extends along the outer periphery of the predetermined excavation section A. And are integrally joined.
Since each consolidated body 5 is glassy and is integrally formed by connecting the electrodes 3 to each other, the uniaxial compressive strength thereof is 1000 kg / cm ² or more, and it is a very high-strength permanent structure. Become.

After completion of the above-mentioned improvement work, the inner peripheral side on which the solidified body 5 is formed is excavated along the planned excavation section A using blasting or the like, and lining with concrete or the like is performed once. Complete the excavation work cycle. Hereinafter, boring of the guide hole 2 and insertion of the electrode rod 3 prior to the excavation work,
The excavation is repeated while sequentially forming the arch of the consolidated body 5 by performing the current application operation.

Since the arch of the consolidated body 5 becomes an extremely high-strength layer and the melting range varies depending on the geology, the arch is not formed directly in contact with the outer periphery of the planned excavation section A and does not solidify to a certain extent. It is desirable to form via a layer. To this end, an insulator 3a or the like is provided on the outer periphery of a portion of the electrode rod 3 located on the entrance side of the conducting hole 2 as shown in FIG. The portion connecting the insulators 3a remains undisturbed without being melted, and subsequent excavation is easy to perform, and excavation can be accurately performed along the cross section A.

In addition to the method of excavating and inserting the conductive hole 2, the electrode rod 3 may be directly penetrated.

[0014]

As described in detail in the above embodiments, the tunnel construction method according to the present invention melts and solidifies the ground itself, so that no material such as a chemical solution is required, and soil contamination is prevented. This method is economical because it does not involve pollution or groundwater pollution, and can improve the ground in a relatively short time without taking a cycle time such as a chemical solution injection time and a consolidation time. According to the present invention, the improved and strengthened area can be predicted to some extent and the management thereof is relatively easy, and an extremely strong arch is formed on the outer peripheral side of the tunnel pit. There is no collapse and safety during excavation is improved.

[Brief description of the drawings]

FIG. 1A is a front sectional view showing a tunnel construction method according to the present invention. (B) is an explanatory side sectional view of the same.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tunnel 2 Conducting hole 3 Electrode rod 5 Vitreous solid

Claims (1)

(57) [Claims] 1. Prior to excavation of a face, a plurality of electrode rods penetrate at predetermined intervals along a circumferential shape of a planned excavation cross section toward a ground at least on an upper front side of the face, and each electrode is After passing the current between the rods, the ground part located between the electrode rods is heated and melted into a glass shape, and then cooled to form a glass-like consolidated body in an arch shape. Tunnel construction method.