US3735541A

US3735541A - Method and device for anchoring tie-rods in ground

Info

Publication number: US3735541A
Application number: US00160684A
Authority: US
Inventors: W Vanderlinde
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-07-08
Filing date: 1971-07-08
Publication date: 1973-05-29
Anticipated expiration: 1990-05-29

Abstract

A tie-rod or cable is anchored in the earth by drilling a hole in the soil or rock and placing in the hole a double-wall casing comprising spaced inner sleeves and outer sleeves. Annular spacers between successive sections of the inner and outer sleeves have longitudinal holes receiving strands or bars of the cable or the rod to be anchored. The inner and outer sleeves are weakened by longitudinal slits or cuts. Cement injected under pressure through an injection tube inserted inside the casing causes slits in the inner sleeves to open so that the cement fills the annular space containing the tie-rod or cable bars or strands and then causes bursting of the outer sleeves to fill any space surrounding the casing. Seals between the injection tube and the spacers limit the injection to one section at a time. After injection with cement, the middle of the casing is flushed out to permit subsequent reinjection.

Description

United States Patent 1 Vanderlinde [451 May 29, I973 METHOD AND DEVICE FOR ANCHORING TIE-RODS IN GROUND Waipy Vanderlinde, Rua 7 de Abril 127 9th Floor, Sao Paulo, S. Paulo, Brazil Filed: July 8, 1971 Appl. No.: 160,684

[76] Inventor:

US. Cl. ..52/98, 52/155, 61/35,

61/39, 61/45 B, 85/65, 85/72 Int. Cl. ..E02d 5/80 Field of Search, ..52/98, 155, 156,

[56] References Cited UNITED STATES PATENTS Debiton ..52/ 155 X Lagerstrom ....52/l56 X Ahlgren et al. ....52/1 55 X Jorge ..52/166 X Primary Examiner -Price C. Faw, Jr. Attorney-Robert E. Burns and Emmanuel J. Lobato [57] ABSTRACT A tie-rod or cable is anchored in the earth by drilling a hole in the soil or rock and placing in the hole a double-wall casing comprising spaced inner sleeves and outer sleeves. Annular spacers between successive sections of the inner and outer sleeves have longitudinal holes receiving strands or bars of the cable or the rod to be anchored. The inner and outer sleeves are weakened by longitudinal slits or cuts. Cement injected under pressure through an injection tube inserted inside the casing causes slits in the inner sleeves to open so that the cement fills the annular space containing the tie-rod or cable bars or strands and then causes bursting of the outer sleeves to fill any space surrounding the casing. Seals between the injection tube and the spacers limit the injection to one section at a time. After injection with cement, the middle of the casing is flushed out to permit subsequent reinjection. 1

14 Claims, 9 Drawing Figures 135 so 9519-1 43,8 ii

PATENTED W29 3. 735 541 SHEET 1 [IF 5 PATENTEL MAY 2 91973 SHEET 0F 5 METHOD AND DEVICE FOR ANCHORING TIE-RODS IN GROUND As is well known, in various engineering applications, a tie-rod is a structural element capable of transmitting tensile forces whenever fixed in soil or rock. The tensile load is transmitted from the tie-rod anchoring head to a predetermined rock or subsoil zone through the anchoring mass.

Thus installation of a tie-rod basically comprises three major parts:

a. Anchoring mass or the portion through which the load is transferred to the ground. This is the portion which is directly fixed or based in the subsoil or rock and through which the tensile load is transferred to the ground.

b. The free portion which is the portion through which the tensile force is transmitted.

c. The tie-rod anchoring head, which is the free portion extending out of the hole to which the tensile force is applied. The tensile load is applied by means of the anchoring device. This makes possible the application of the load to the supporting structure.

The major differences among the various methods of making a soil or rock-anchored tie-rod are related to the:

-- Drilling method Armor type and assembly, and

- Injection device and process.

The most commonly used drilling processes are the following:

- without washing and by means of a worm auger-bit with washing and by means of a rotary boring-bit The hole may be cased or without casing. This depends on the type of soil to be drilled, on the ground water level and on the drilling speed and tie-rod installation.

in the case of drilling performed in crumbling soils, temporary stability of the hole casing is achieved by means of circulation of bentonite mud, in a manner similar to that used for diaphragm walls.

A sort of mechanical reamer may be used to provide the anchorage, in order to increase the contact surface between cement and soil.

Usually the types of armor used are' made of steel bars, steel wires or tubes. The mechanical properties of the steels must fulfill the prestressing requirements, that is, high tensile strength, elastic deformation and small loss in tension load.

Further details on drilling and tie-rod armor are not necessary because the known systems for the production of tie-rods are basically difierent, according to the way of producing the anchor mass.

Concerning the injection devices and process, it is known that from the viewpoint of cement or chemical products injected, anchorages may be classified in two groups:

a. Tie-rods anchored by means of injection without pressure (gravity). The tie-rods produced in this way present limited load capacity.

b. The injection under pressure of the anchorage portion is the major key to achieve a greater load capacity of the anchorage. Besides, it assures a uniform behavior in large scale production.

Several existing patents are related to the production of under-pressure injection anchorage. The main types are the following:v

a. Soletanche Tie-Rod This method involves injection through an auxiliary tube placed in the inner part of the steel wire cable. Outlets for cement exit are provided along the anchorage portion of the tube. These outlets are covered with cuffs.

b. Bauer Tie-Rod This system involves injection through the drilling case. When the desired hole depth is reached, the tierod armor is joined to the last shoe. After this, the casing is gradually removed while simultaneously injecting cement under pressure, which entirely fills the space between the armor and the inner part of the'hole.

Soil and rock anchorages have several applications in the engineering field, such as:

stabilization of slopes supporting structures against earth or water pressures tunnel lining fixation concrete dams fixation, and many others.

For a better understanding of the disadvantages of the existing techniques, one may consider, at first, that those techniques provide, in most cases, for a fourlayer protection of the free portion.

1. Armor painting 2. Plastic casing 3. Cement or chemical product injection in the inner part of the plastic casing and entirely surrounding the armor 4. Cement injection in the outer part of the plastic casing, which entirely fills the hole.

Concerning the anchored portion, the various systems generally provide for a single protection layer formed by the injected cement. This is due to the fact that it would be impracticableto paint the armor, since this would weaken or even prevent the adherence to the cement.

Besides, there is a technical difficulty in assuring a uniform protection in all of the armor points, because as there is no other protection element previously mounted over the anchorage portion of the tie-rod, the armor may contact the soil directly during its adjustment phase. This fact makes it impossible to assure that all points will be adequately protected during the under-pressure injection phase.

Yet, to achieve a better protection, it is necessary to install the perfectly centered tie-rod in a hole having a much greater diameter, with the aid of centering devices. This is done in order to assure that the tie-rod, in its installation phase, will not contact the soil. Thus, all the armor points are maintained spaced a sufficient distance from the inner part of the hole. Obviously, this is an expensive system.

Even adopting the above-mentioned precautions, one can barely assure that local hole crumblings will not cover certain points of the cable with earth or mud, thus endangering its perfect protection.

Such disadvantage can be overcome by easing the hole. This is provided for by certain systems which obviously makes it a rather expensive method.

Such factors of protection against adverse environmental conditions are essentially important, mainly regarding permanent tie-rods, that is, those structural elements functioning in a permanent manner, with respect to load application.

The present invention has for its object a new method and device for the production of anchorages, whenever the fixation of tie-rods in soil or rock may be consid ered. They have been carefully designed to provide something new, original, economic, and highly efficient.

The new technique in accordance with the invention is based on the production of an anchorage by underpressure injection of cement or chemicals in the soil or rock. For a better understanding of the new technique, a general description will be next developed, concerning the tie-rod assembly process. The tie-rod armor is basically formed of a set of special steel wires or bundles of special steel wires arranged in a circle, the whole set forming a circular cable.

The above-mentioned steel wires or bundles of steel wires are arranged in that way in the anchorage portion, by means of special spacers to which a set of special sleeves is connected. These sleeves are mounted around and in the cable, thus forming two sets of successive chambers (external and internal ones), separated from each other. The spacers are internally provided with special retention devices.

Whenever required, the tie-rod may be also assembled in the free portion, in a similar manner to that already described for the anchorage portion.

The accompanying drawings illustrate the present conception by way of example.

FIG. 1A schematically shows a side view and FIG. 13 a cross-section of a device in accordance with the invention for anchorage of tie-rods in soil or rock.

FIGS. 2, 3, 4 and 5 are side views and partial sections illustrating the possible and different ways of connecting the components of the device.

FIGS. 6 and 7 are side views and partial sections of the device during the injection and washing phases, respectively.

FIG. 8 is a side view and partial section illustrating an alternative way of performing the same function.

As illustrated in the drawings, the device for the anchorage of tie-rods in soil or rock is composed by two sets of successive chambers, respectively internal and external chambers, separated from each other and connected through special spacers which also position the wires or bundles of wires that form the tie-rod armor.

The external chamber (FIG. 1) is formed by special annular sleeves 1, preferably made of asbestos cement, metal, plastic or other suitable material.

Such sleeves 1 may be provided with specialmeans of weakening their structure, such as longitudinal slots or fissures 2, or other means.

The ends of the annular sleeves l are shown provided with external annular grooves 3 (FIG. 2) or internal ones, against which special parts such as sleeves 4, threaded sleeves 5, spacers 6 or other pieces may be ccmented, threaded or merely fitted.

The internal chamber is formed by a special annular sleeve 7 (FIG. 2) preferably made of elastic material, for example plastic, elastomeric material or sheet metal, and provided with special means of weakening the material, such as external or internal longitudinal slots or cuts 8 (FIG. 1). The sleeve 7 may be also surrounded by very elastic expansive media with the purpose of facilitating the successive explosions.

After being exploded, the above-mentioned sleeve acts like a valve, allowing for the flow of the cement to the exterior and preventing its return.

Such sleeves are internally joined to the special spacers 6 by threading, cementing or simple fitting.

Several systems are provided to connect consecutive sleeves, such as one-hinge, two-hinge, threaded or other connectors.

In the one-hinged system of connection (FIG. 2) use is made of a special spacer 6 having longitudinal holes 9, arranged in a circular or other pattern for the purpose of guiding and spacing the tie-rod armor wires 10, connecting consecutive sleeves and housing the sealing and hinging devices.

Externally, in one end the spacer 6 has an annular groove 11, the purpose of which is to house an elastic ring 12 or other sealing or hinging device, upon which the external sleeve 1 of the corresponding chamber is connected, by means of a simple sleeve 4.

At the opposite end the spacer 6 is provided with an extension 13, which externally fits with the annular groove 3 in the corresponding end of the neighboring external chamber sleeve 1.

Internally, the spacer 6 has an annular groove 14 or other cavity for the purpose of housing one or more elastic retention rings 15 or other adequate sealing and retention device.

The spacer 6 also has two internal annular recesses 16, for the purpose of connecting consecutive internal chamber sleeves 7, which may be secured to the spacers by any suitable means.

In the two-hinged system of connection (FIG. 3), there is provided another special type of spacer 6', which is also an annular member, with longitudinal holes 9' arranged in a circular pattern to receive the tie-rod wires 10. In its external surface the spacer 6' has a pair of annular grooves 11' and,in its internal face, a similar groove 14, all of which being for the purpose of receiving one or more elastic sealings rings 12' and 15. The external sealing rings 12' are each in front of the corresponding sleeve 4 which is applied to the ends of two consecutive external sleeves l. The internal ring 15' faces the injection tube described below.

In the threaded joint system (FIG. 4), the ends of the external sleeves 1 are fitted in special threaded sleeves 5, one of which is the male part, the other the female part. Each of the sleeves 5 has an inwardly projecting part 17. When the parts are assembled, the salient part 17 forms an annular housing which locks the special spacer 6".

In this case, the spacer 6", externally, presents an annular cylindrical shape so as to fit inside the sleeves 5. Internally, the spacer 6" is provided with groove 14" to receive an elastic sealing ring 15''.

The internal sleeves 7 may be in the form of a continuous tubing (FIG. 5) engaged at the separation points between successive chambers by the special spacers 6". In this case, the sealing rings 18' instead of being provided on the spacers internal faces are applied in circular grooves 18 provided in the injection tube 19.

The injection tube 19 is preferably of a constant section for the sake of exactly fitting into the sealing rings housed in the special spacers. It may be opened in its inner end or else may have side outlets 20. In the latter case, it must be sealed at its inner end.

The above descriptions, as well as the corresponding drawings are only examples of the construction in accordance with the present patent. Of course, it may present several variations, within the same basic concepts.

The related method of installing an anchoring device, first involves the drilling and cleaning of the hole, the installationof the tie-rod and then follows either the introduction of an injection tubing through its inner part, until it reaches the corresponding chamber in the tierod foot, or the introduction of the injection tubing along the outer part of the tie-rod until it reaches the bottom of the hole.

Cement is then injected through the tubing, until the achievement of a complete hole obturation.

After the cement was cured, the injection of cement under pressure is started. For this purpose, the injection tubing 19 (FIG. 5, 6, and 8) is introduced inside the tie-rod, until its end penetrates one of the chambers. Cement is-then injected through the tubing under pressure.

At first, the injected cement fills the internal chamber formed by the inner sleeve 7, and then causes it to blow up, as injection pressure increases. The slots or cuts 8 open up under the pressure of the cement and the cement thereupon begins to flow to the external chamber and to surround the armor. In a similar way, the outer sleeve also blows up, thus allowing the cement to flow through the slots in the sealing cement layer.

The cement is injected until it reaches the desired pressure or, if it is not possible, the injection is interrupted when a certain volume has been pumped in.

This operation is similarly repeated in succession for all of the other chambers, after which, washing of the internal chambers is performed by water circulation through a suitable tubing 21 (FIG. 7).

After the injected cement has cured, as above described, new reinjections under pressure are successively performed, until the desired pressures have been reached in all chambers.

In order to allow for future eventual reinjections, the operation is finished bywashing the internal chambers with circulating water as above described.

In certain cases, depending on the application, the anchorage portion of the tie-rod may be assembled using only one of the chambers sets (external or internal) as illustrated in FIG. 8.

In both cases, injections are performed in a similar way to that already described. However, this is done by using only one chamber set.

The advantage which characterizes the presented process is based on the fact that this anchorage can be achieved with the assurance of total protection of the armor, against adverse environmental conditions. For this reason, it can be regarded, with absolute reliability, as a permanent structural member, whenever the armor protection is a primary requirement.

The protection may be considered as complete because, in addition to the existent chambers in the anchorage, the inner steel of the armor is directly and completely surrounded by cement injected under high pressure thus resulting in a substantial increase of the adherence.

The system allows for successive reinjection in such a manner that it can be successfully performed with any type of soil. Also, if the specified load is not reached during the prestressing phase, the anchorage strength may be later increased through new reinjections (FIG.

Provided that the free portion is assembled with the same type of chamber used for the anchorage portion, it may, after prestressing, be injected under high pressure, thus increasing the protection for this portion and compacting through injections the corresponding portion of the ground and so increasing the construction safety.

The proposed technique, depending on the type of formation or on the nature of the application with respect to its duration, makes possible the execution of more economical alternatives.

Thus, in permanent constructions, whenever working with granular or other resistant formations, which do not present the clacage phenomenon, one can omit the internal chamber. This will result in material and labor savings, technical quality being maintained for the tie-rod.

In this event, the injection may be performed using the simple injection tube which provides cement exit through the inner end and starting with the most distant chamber.

Whenever working in constructions for which the tierod application is a temporary one, it will not be neces sary to assemble the external chamber. In this event, it will be enough to use the internal chamber, in which case there will be substantial savings, either in material or in drilling.

The system provides an actual uniform operation of the free portion, thus identifying itself with the theoretical results.

The drilling operation, when compared with prior systems, makes it possible to use smaller hole diameters for the same load capacity.

The system allows for tie-rod utilization with any type of soil or rock, even though the anchorage portion presents flaws such as cracks, clacage veins, etc.

Moreover, the system has the following additional advantages:

The utilized equipment is light and has a high operational efficiency Materials are available for manufacturing the tierod cable and components.

From the above comments, it follows that the tie-rod anchorage produced in accordance with the proposed technique and devices, is able to achieve an extreme degree of technical excellence. It is also possibleto exert a rigorous quality control since all the components are industrial designs.

In conclusion, it is highly economical because of the ease of its assembly process and besides, it can be introduced in a hole with a smaller diameter.

What'l claim and desire to secure by letters patent is:

l. A method of anchoring tie-rods in the earth, comprising preparing a hole in the earth, positioning in said hole a double-wall casing comprising spaced inner and outer sleeves with annular spacers between successive sections of said sleeves and positioning tie-rod elements in longitudinal holes in said spacers so that said tie-rod elements are positioned between said inner and outer sleeves, said sleeves being prepared for opening or bursting upon application of internal pressure, inserting an injection tube inside said casing and injecting fluid cement under pressure into the interior of said casing to burst or open said inner sleeve, continuing the injection of cement under pressure to fill the annular space between the inner and outer sleeves and thereby fully envelope said tie-rod elements, and further continuing the injection of cement under pressure to burst or open the outer sleeve and inject cement into said hole around said casing.

2. A method according to claim 1, further comprising providing longitudinally spaced annular seals between said injection tube and said spacers to confine the injection of cement to one section at a time, and injecting cement into successive sections successively.

3. A method according to claim 1, further comprising flushing out the interior of said casing after an injection of cement to clear it of cement, and subsequently reinjecting cement in said casing.

4. A system for anchoring tie-rods in holes in the earth, comprising a double wall casing comprising radially spaced inner and outer sleeves, longitudinally spaced annular spacers disposed between successive sections of said sleeves, said spacers having circumferentially spaced longitudinally extending holes, elements of said tie-rod to be anchored being received in said holes and thereby positioned between said inner and outer sleeves, and means for injecting cement under pressure into the interior of said casing, said inner and outer sleeves being weakened to be burst or opened upon application of pressure of said injected cement, whereby the injected cement fills the annular space between said inner and outer sleeves, thereby fully enveloping said tie-rod elements, and is further injected into said hole around said casing.

5. An anchoring system according to claim 4, in which each of said annular spacer has an inwardly opening annular groove and a flexible sealing ring posi tioned in said groove and engageable with said injection tube to provide a flexible seal between said injection tube and said spacer.

6. An anchoring system, according to claim 4, in

which each said annular spacer has at least one outwardly opening groove and a flexible sealing ring positioned in said groove and engaging an end portion of an adjacent outer sleeve section to provide a flexible fluidtight joint between successive outer sleeve sections.

7. An anchoring system according to claim 6, in which each said annular spacer has two said outwardly opening grooves containing said flexible sealing rings engaging respectively end portions of two adjacent outer sleeve sections to provide a flexible fluid-tight joint between said outer sleeve sections.

8. An anchoring system according to claim 4, in which said outer sleeve sections are of frangible material.

9. An anchoring system according to claim 8, in which said outer sleeve sections are weakened between said spacers by longitudinally extending slits or cuts.

10. An anchoring system according to claim 8, in which said outer sleeve sections are formed of asbestos cement.

11. An anchoring system according to claim 4, in which said inner sleeve sections are formed of flexible material.

12. An anchoring system according to claim 11, in which said inner sleeve sections are weakened between said spacers by longitudinally extending slits or cuts.

13. An anchoring system according to claim 4, in which said injection tube is of constant section and is closed at its inner end and provided with openings in its sides.

14. An anchoring system according to claim 4, further comprising means for flushing out the interior of said casing after said injection of cement.

Claims

1. A method of anchoring tie-rods in the earth, comprising preparing a hole in the earth, positioning in said hole a doublewall casing comprising spaced inner and outer sleeves with annular spacers between successive sections of said sleeves and positioning tie-rod elements in longitudinal holes in said spacers so that said tie-rod elements are positioned between said inner and outer sleeves, said sleeves being prepared for opening or bursting upon application of internal pressure, inserting an injection tube inside said casing and injecting fluid cement under pressure into the interior of said casing to burst or open said inner sleeve, continuing the injection of cement under pressure to fill the annular space between the inner and outer sleeves and thereby fully envelope said tie-rod elements, and further continuing the injection of cement under pressure to burst or open the outer sleeve and inject cement into said hole around said casing.

3. A method according to claim 1, further comprising flushing out the interior of said casing after an injection of cement to clear it of cement, and subsequently re-injecting cement in said casing.

5. An anchoring system according to claim 4, in which each of said annular spacer has an inwardly opening annular groove and a flexible sealing ring positioned in said groove and engageable with said injection tube to provide a flexible seal between said injection tube and said spacer.

6. An anchoring system, according to claim 4, in which each said annular spacer has at least one outwardly opening groove and a flexible sealing ring positioned in said groove and engaging an end portion of an adjacent outer sleeve section to provide a flexible fluid-tight joint between successive outer sleeve sections.