Ground anchorage means utilizing a reinforcement or tie insulated from the ground

The ground anchorage means comprises a reinforcement combined with an adjacent injection tube furnished with sleeves acting as retention valves and a distensible sack intended to obturate the drilled hole. The fixing zone of the reinforcement is protected by an impervious envelope made of a rot-proof and anti-corrosive material in which the reinforcement is immersed in a hardenable material such as grouting cement. The free zone is immersed in an anti-corrosive product, which may be flexible in another envelope or sheath, the two envelopes being joined together by a sealing sleeve. Application, particularly for supporting walls.

This invention relates to ground anchorage means, for example in order to 
support retaining walls, and comprising the combination of a tie-rod 
forming a reinforcement and an injection tube adjacent the tie-rod, 
perforated with apertures having retention valves to allow the exit of an 
injectable grouting material but not the inlet of such material. At least 
one distensible sack is generally mounted in a sealed manner on a part of 
the reinforcement and of the tube, at least one opening of this tube being 
situated in the sack in such a manner that it can be distended by using 
the said tube. 
A device of this type is described in the applicants' French Specification 
No. 1,539,176, corresponding to U.S. Pat. No. 3,494,134. 
To use such means, a hole is drilled in the ground, the anchoring means is 
introduced into it, the sack is distended by injecting suitable material 
into it, such as a cement mix, in order to delineate in the drilled hole a 
sealed fixing area into which is injected hardenable material, such as 
grouting cement, and subsequently the reinforcement is put under tension 
thus anchoring the structure to be supported. 
The devices which have just been mentioned have a disadvantage in that the 
bulb formed by the anchoring material is subjected to tension, at least in 
certain of its parts, which can result in the formation of cracks. If 
cracks are formed, water can penetrate from the soil into the bulb even to 
the extent of coming into contact with the reinforcement and corroding it. 
The main object of this invention is to prevent this disadvantage. 
To this effect, according to the invention, the reinforcement is protected 
by an impervious envelope of a rot-proof material which is not subject to 
corrosion, for example a plastics material, in which it is sealed and 
immersed in a material such as grouting cement, ensuring the transference 
of forces between the reinforcement and the fixing bulb outside the 
envelope, the envelope being able to contain, if required, anti-corrosive 
or insulating products. 
In the area of the reinforcement intended to be immersed in the fixing 
bulb, a zone which is often called the root, the envelope is preferably 
crenellated, for example by helically winding thereabout a ribbon of 
suitable section, in such a manner as to ensure good adhesion and, if 
required, to form, on the interior as well as on the exterior, a 
thread-like formation which ensures good transference of forces and 
correct filling of the envelope. 
This filling may be facilitated by means for removing water comprising a 
hollow tip with perforated walls which fits on the envelope and contains a 
porous mass ensuring the elimination of air and residual water after 
injection of the internal sealing product. This tip may be left in place 
or replaced by an impervious cap after fixing. 
In the area of the reinforcement outside the fixing zone and which is 
called the free area, a smooth envelope or sheath is provided which can be 
furnished internally with an anti-corrosion product which does not hinder 
free play of the reinforcement, for example a product having a base of 
pitch and epoxy resin or of grease, a plug and sleeve connecting device 
ensuring the continuity between the free zone and the fixing zone and the 
two envelopes being joined together by an impervious sleeve. 
Advantageously, the head of the reinforcement is equipped with masking 
means ensuring electrical insulation and preventing corrosion.

In FIG. 1, a complete anchoring device is shown after insertion of a 
reinforcement 1, sealed in a protective envelope 10, which is positioned 
in a drilling 2 in the ground and secured by a mass or bulb 3 of grouting 
cement or other suitable material supporting the reinforcement under 
tension against a structure 4 to be supported, by means of a suitable 
system 5 advantageously having electrical and ionic insulation which 
imparts good insulation to the reinforcement. 
The reinforcement comprises a fixing part or zone, otherwise termed the 
root, and a part or zone which is not fixed, called "free". Between these 
two parts or zones an obturation sack 6 is situated into which is injected 
a hardenable material, such as grouting cement, in order to partition off 
the drilled hole 2 and to delineate the injection zone 3 from the free 
zone 2, which will be filled with a suitable material according to usual 
practice. 
The injection of the zone 3 and the filling of the obturation sack 6 is 
carried out by means of a tube 7 which is adjacent the reinforcement 1 and 
which passes through the sack 6 in a sealed manner. This tube is provided 
with a plurality of spaced outlet orifices furnished with retention valves 
comprising sleeves 8 made of rubber or a similar elastomer. The majority 
of the sleeves 8 are situated in the fixing zone; at least one is provided 
in the sack 6 and at least one other in the free zone. Injection is 
accomplished by means of an auxiliary tube (not shown) provided with 
outlet orifices situated between two obturators which block the tube 7 on 
either side of the orifices where the injection is to take place. All this 
is well known in the state of the art and forms the subject, for example, 
of French Specification No. 986619, published in 1951. 
The fixing zone or root of the reinforcement is surrounded and protected by 
a continuous envelope 10, with a crenellated longitudinal section which 
can be of helical form, in such a manner that the envelope can be sealed 
and have inside as well as outside a relief pattern, for example a 
thread-like formation, ensuring good transmission of forces between the 
material inside the envelope (material 30) and the material outside the 
envelope (material 3). 
The shape and the dimensions of the crenellations, as well as the thickness 
of the envelope, are selected so as to avoid unnecessary shearing 
stresses. In addition, the crenellated shape of the envelope avoids 
possible loss of adhesion of the fixing material, internally as well as 
externally, to the material of which the envelope is made. 
Furthermore, it is of advantage to use a continuous spiral crenellation, in 
order to facilitate the circulation of the internal fixing material in the 
envelope during its injection so as to completely fill the envelope in 
order to ensure a complete encasement of the reinforcing tie-rod. 
The lower free end of the envelope is provided with a drying or water 
removing device 11 which will be described in greater detail with respect 
to FIG. 2 and which allows the injection under pressure into the envelope 
of the internal fixing material, for example, a grouting mortar or cement, 
which may be the same as the material forming the outer bulb or may be 
different. 
At the other end of the root, the envelope contains a plug 12 which 
separates the root from the free zone, and through which the reinforcement 
1 passes. 
This latter zone includes another smooth, flexible and continuous envelope 
or sheath 13 which passes through the obturation sack 6. This sheath does 
not adhere to the materials it contains and those which surround it, thus 
allowing free movement of the reinforcement. 
The continuity between the envelope 10 and the sheath 13 is ensured by a 
sleeve 14 extending about plug 12 consisting of a crenellated portion, 
which is fitted in a sealing manner to the envelope 10, and a smooth 
portion which is fitted in a similar manner to the sheath 13 or glued or 
welded thereto. 
FIG. 2 shows the water removing device which consists of an ogival cap or 
tip 15 pierced with holes 16, integral with a crenellated extension 17 
fitted on the envelope 10. 
The ogive is provided with a vent 18 permitting the escape of air before 
forcing the injected material into the envelope 10 around the 
reinforcement 1; it is lined with a porous material 19. 
The water removal device may be left in place or replaced by a sealing cap, 
after the envelope 10 has been filled with the injected material. This cap 
is advantageously made of the same material as the envelope 10 and welded 
thereto in order to ensure continuity of the envelope. 
In FIG. 3 can be seen the support system 5 which features a pressure plate 
20 resting directly on the structure 4 around the entrance to the drill 
hole 2. The sheath 13 of the reinforcement is surrounded in a sealing 
manner by an insulating socket 21 extending into an insulating flange 22 
on which rests a plate 23 receiving a member 24 which clamps the tie-rods 
25 of the reinforcement. The tie rods extend to the end cap 15, as shown 
in FIG. 2. 
The whole is covered by a cap 26 which insulates it from the outside. 
The interior of the sheath 13 is covered with an insulating material 27, 
preferably flexible and deformable, such as a pitch-epoxy based material, 
a grease or any other non-corrosive product, or a cement grouting. To this 
effect, the tie-rods 25 are kept spaced apart, for example by tubular 
spacers (not shown), so as to permit the passage of an injection tube. 
After the cap 26 has been put in place a sealing compound 28, preferably 
similar or identical to the material 27, is injected into this cap. 
The anchoring device can very conveniently be manufactured in the factory 
or in another suitable place before being inserted into the ground, thus 
considerably facilitating its employment and assuring every safety factor 
from the point of view of quality. 
It is clear that the method of manufacture shown is only an example and 
that it can be modified, notably by substituting equivalent techniques, 
without departing from the framework of the invention.