EP0532441A1 - Method for consolidating tunnel walls, gallery walls, or the like, anchoring bolt for carrying out the method, and method for making such anchoring bolts - Google Patents

Abstract

The invention relates to a method for reinforcing tunnel walls, gallery walls or the like, to an anchoring bar for implementing the said reinforcing method and to a method for making such an anchoring bar. It will apply in particular in the field of construction, drilling and/or earthworks. According to the reinforcing method of the invention, a channel (5) having a cross-section which is greater than that of the anchoring bars is drilled into the rock (3), a hollow anchoring bar is placed in each channel and a hardenable grout is injected inside the bars which runs along the said bar and then fills the space (7) between the rock and the outside of the bar. Furthermore, the anchoring bar is in the form of a tube (2) of which at least the external casing (16) has helical protuberances (15). <IMAGE>

Description

The invention relates to a method of consolidating walls of tunnels, galleries or the like, to an anchor rod authorizing the implementation of said method, as well as to a method of producing such anchor rods.

It will find its application in the field of construction, drilling and / or soil exploitation.

In this area, when digging galleries, tunnels or similar in the ground, it is necessary to consolidate the wall to avoid crumbling and strengthen it. This is implemented both in the provisional and final phases.

To achieve such consolidation, it is known to drive one or more anchor rods, also known as nails or anchor bolts, into said rock.

Depending on the rock and according to the conditions, rods of about 30 millimeters in diameter are generally inserted, the length of which can go up to 6 meters, this at the rate of 3 to 6 rods per m² of walls.

In this regard, anchor bolts are known, consisting of a substantially annular body split from one end to the other of its length, which will be introduced into conduits previously drilled in the wall of the rock, the diameter is substantially close to that of the bolt.

In this case, in order to allow the introduction of the bolt into the conduit, the body of the compressed anchor bolt is maintained so that it has a diameter substantially less than the diameter of said conduit. Once introduced, the body is released from the anchor bolt, so that thanks to its elasticity it relaxes to come into contact with the surrounding rock wall and clings to it.

One of the main drawbacks of this technique lies in the realization of the preliminary perforations of the wall which are carried out with augers of diameter close to 30 millimeters which break easily during drilling, this being amplified by the significant length of the perforation to be carried out .

Another difficulty consists in maintaining the anchor bolt in the compressed state at the time of introduction. Furthermore, if the expansion force is low, and depending on the quality of the rocks, there is relative sliding between the bolt and the wall when the force applied to the bolt is high.

The object of the present invention is to propose a method of consolidating walls of tunnels, galleries or the like, as well as anchor rods allowing the implementation of said method which make it possible to overcome the drawbacks of known systems, in particular by causing less breakage during the drilling of the wall, and secondly by facilitating the implementation of the consolidation process.

Another object of the present invention is to provide anchor rods, intended for the consolidation of walls of tunnels, galleries or the like whose structure allows significant adhesion, the anchor rod installed in the wall being able to withstand stresses traction greater than 5 tonnes.

Another object of the present invention is to provide anchor rods, of simple structure, the production method of which is easy to implement.

Another object of the present invention is to provide an anchor rod whose structure allows the attachment to be distributed over the entire length while avoiding point anchor points at which the stresses would concentrate.

Other objects and advantages of the present invention will appear in the description which is however given only for information and which is not intended to limit it.

• on fore la roche pour constituer un conduit de section supérieure à celle des dites tiges,
• on place dans chaque conduit une tige d'ancrage creuse,
• on injecte à l'intérieur des tiges un coulis durcissable qui traverse la dite tige puis vient remplir l'espace compris entre la roche et l'extérieur de la tige.

According to the present invention, the method of consolidating walls of tunnels, galleries or the like, by which in particular the crumbling of the rock forming the wall is avoided by driving one or more anchoring rods into said rock is characterized by the fact than :

• the rock is drilled to form a duct with a cross section greater than that of the said rods,
• a hollow anchor rod is placed in each conduit,
• a curable grout is injected inside the rods which crosses said rod and then fills the space between the rock and the outside of the rod.

However, the anchor rod, authorizing the implementation of the inventive method, is characterized in that it is in the form of a tube of which at least the outer casing has helical protuberances.

According to the method for producing the anchor rod of the invention, one starts from a cylindrical tube which is twisted to create, at least on the outside, the said helical protuberances.

The invention will be better understood on reading the following description, accompanied by the accompanying drawings which form an integral part thereof.

Figure 1 shows, by way of example, a sectional view of a gallery consolidated by anchor rods.

Figure 2 shows a sectional view of an anchor rod according to the present invention inserted into the rock to consolidate the wall.

FIG. 3 shows a view, partly in section, of the anchoring rod illustrated in FIG. 2.

Figures 4a and 4b illustrate a front view and a side view of an anchor rod according to the invention during its manufacture.

The invention relates to a method of consolidating walls of tunnels, galleries or the like, an anchor rod authorizing the implementation of said method, as well as a method of making such anchor rods.

In the field of construction, drilling and / or exploitation of the ground, it is usual during the realization of tunnels, galleries or the like to consolidate the walls to prevent the rock from crumbling. Generally, the walls are consolidated by driving one or more anchor rods per m² into the rock.

These rods commonly have a diameter close to 30 millimeters and, depending on the nature of the rock and the consolidation to be carried out, have lengths of three to six meters.

Figure 1 schematically illustrates the implementation of such a consolidation of a gallery 1 by means of anchor rods 2 driven into the rock 3 forming the wall of the gallery.

Figure 2 shows a sectional view of an anchor rod 2 according to the invention inserted in the rock.

For this, according to the method of the invention, the rock 3 is drilled beforehand to constitute a conduit 5 of section "C" greater than that of said rods 2.

Then, a hollow anchor rod 2 is placed in each conduit 5 which will be held in place in the conduit, and consequently in the rock, by the addition of materials 6 such as cement or resin for example.

In this regard, according to the method of the invention, a hardenable grout 6 is injected inside the hollow rods 2 which crosses said rod 2 and then fills the space 7 between the rocky envelope of the conduit and the outside of rod 2.

In Figure 2, the arrows simulate the injection of said curable grout that is introduced at the wall 4 at the inlet 8 of the tube 2, as shown by arrow 9. This grout is then conveyed by the pipe formed by the internal part of the tube 2, as the arrow 10 simulates, to evacuate at the distal end 11 of the tube at the bottom of the conduit 5.

Therefore, as the arrows 12 simulate, at the bottom of the duct, the curable grout is forced around the tube in the duct 5 towards the wall 4 of the gallery.

When the grout is evacuated at the entrance to the conduit 5, around the tube 2, as the arrows 13 and 14 simulate, the injection is stopped and the setting of the curable grout takes place.

As a result, the rod is completely embedded in the rock and, after setting, there is an adhesion of the rod in the rock. It should be noted that good results have been obtained by injecting a cement or resin grout at a few kilos of pressure, and by providing a conduit 5 with a diameter close to 60 millimeters for an anchor tube whose diameter is close from 30 to 40 millimeters.

Also, larger diameter perforations can be made in the rock with augers with higher resistance due to their diameter. Thus, there is a gain because it breaks much less augers, which inevitably affects the cost of the site.

Furthermore, the central injection into the tube and the discharge of the grout outside the tube makes it possible to avoid air bubbles, which would be detrimental to the coefficient of adhesion.

In this regard, according to the method of the invention, the coefficient of adhesion of the rod 2 is increased by deformation of its envelope.

For this, according to an advantageous embodiment of the present invention, the rod is twisted to create, at least on the outside, protrusions 15, while retaining a constant mean section for filling. This is particularly illustrated in FIG. 3 which shows a view with partial section of an anchor rod according to an embodiment of the present invention.

As specified above, the rod is in the form of a tube 2, at least the outer envelope 16 of which has helical protuberances 15.

The shape of such protrusions makes it possible to give a pitch to attachment zones over the entire length of the tube. In addition, these will also make it possible to strengthen the tube and prevent it from twisting along its longitudinal axis so that it remains rectilinear.

It should also be noted that the helical deformation makes it possible to obtain a constant mean diameter, which will on the one hand promote the resistance of the tube and on the other hand the flow of the curable grout.

Indeed, with regard to resistance, the helical deformation of the envelope will not cause point anchor thus avoiding localized stress concentrations and ruptures at this level.

Regarding the flow, the grout will circulate constantly during the filling phase and we will avoid "air bubbles" which could be caused in areas masked by large and protruding protrusions.

It should be noted that good results have been obtained with a pitch "p" of the helical protrusions of between 5 and 20 cm for a tube of diameters 30, 50 millimeters.

As specified above, to produce these helical protuberances, a cylindrical tube is twisted to reveal, at least outside the tube, a twist as shown diagrammatically in FIG. 3.

During this twisting phase, we will slightly shorten the tube, and gradually form bulges "a" arranged in helicoid. The alternation of the concave and convex forms thus created will allow the attachment of the tube in the grout and consequently with respect to the rock.

Figures 4 a and b show schematically the method of producing said anchor rod according to the present invention, and show in particular the tube 2 whose casing 16 is cylindrical at the start.

One of the ends of the tube, 11 for example, is immobilized, then a torque is applied to the other end, 8 in this case, until the said torsional deformation of the envelope is obtained.

To immobilize the end 11 of the tube, one can for example introduce inside the tube, at least locally, a piece of square tube 17 which will be immobilized in rotation, as shown by the arrows 18, by means of 'a vice for example. Then, we will come and tighten the end 11 of the rod 2 on this square tube 17 to immobilize it also in rotation, as the arrows 19 simulate.

For the rotational drive of the other end 8, as simulated by arrow 20, one can use another piece of square tube 21 which will drive the end 8 of the tube which will then be deformed on the square.

One can also imagine driving this end in rotation by any other means, for example by threading the end of the tube and using a nut and lock nut.

In this regard, it should be noted that generally the ends of the anchor rods, at least on the wall side, have a thread which allows the fixing of a support plate on the rock, not shown in the figures.

In order not to reduce the resistance of the tube by the thread, according to the present invention, one of the ends 8 is pushed back, so that a thread can be produced on the turned-down part 22.

This upsetting 22 will advantageously be carried out prior to the twisting deformation of the rod 2. For this, the thickness of the envelope 16 of the rod 2 is increased by hot delivery such that it is at least equal to the thickness nominal of the tube plus the depth of the thread.

In other words, if as shown in FIG. 3, the outside diameter of the tube 2 is marked with "φ _e ", the inside diameter of the tube 2 is marked with "φ _i ", the delivery diameter is marked with "D" and the diameter at the bottom of the thread is marked with "d",

Under these conditions, the discharge "D" is such that a thread can be produced whose diameter at the bottom of the thread d is at least equal to "φ _e ". That is to say that below this diameter remains an amount of material equivalent to the thickness of the tube (φ _e - φ _i ) / 2.

That said, we can advantageously use the presence of this thread, as specified above in the twisting phase of the tube, and it is this end that we will rotate 20 by placing therein for example a nut and a lock nut, not shown in the figure in order to rotate it.

Naturally, other implementations of the present invention, within the reach of those skilled in the art, could have been envisaged, without however going beyond the framework of this one.

Claims (10)

Method for consolidating walls of tunnels, galleries (1) or the like, by which in particular the crumbling of the rock (3) forming the wall (4) is avoided by driving one or more anchor rods (2) into said rock ), characterized by the fact that: - the rock (3) is drilled to form a conduit (5) of section "C" greater than that of said rods (2), - a hollow anchor rod (2) is placed in each conduit (5), - One injects inside the rods (2) a curable grout (6) which crosses said rod (2) and then comes to fill the space (7) between the rock and the outside of the rod (2). Process according to Claim 1, characterized in that a cement or resin grout is injected at a few kg of pressure. Method according to claim 1, characterized in that the coefficient of adhesion of the rod (2) is increased by deformation of its envelope (16). Method according to claim 3, characterized in that the rod (2) is twisted to create, at least on the outside, protrusions (15), while maintaining a constant mean section for filling. Anchor rod (2), intended for the consolidation of walls of tunnels, galleries (1) or the like, authorizing the implementation of the consolidation process according to claim 1, characterized in that it is in the form a tube whose outer casing (16) has helical protrusions (15). Rod according to claim 5, characterized in that the pitch "p" of the helical protuberances is between 5 and 20 centimeters. Method for producing an anchor rod, according to claim 5, characterized in that one twists a cylindrical tube (2) to create, at least on the outside, helical protuberances (15). Method according to claim 7, characterized in that one end (11) of the tube (2) is immobilized and a torque (20) is applied to the other end (8) until torsional deformation of the envelope (16). Method according to Claim 8, characterized in that, prior to the deformation of the rod (2), one of its ends (11) is pushed back so that a thread can be produced on the pushed back part (22). Method according to claim 5, characterized in that the thickness of the casing of the rod (2) is increased by hot delivery such that it is at least equal to the nominal thickness (φ _e - φ _i ) / 2 plus the thread depth (D - d) / 2.

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