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Title:
IMPROVEMENTS IN ANCHORING SUBJECT TO TENSILE AND/OR COMPRESSION STRESS, PERFORMED EITHER IN SOIL AND/OR ROCK
Document Type and Number:
WIPO Patent Application WO/1994/004787
Kind Code:
A2
Abstract:
A patent of invention for "improvements in anchoring subject to tensile and/or compression stresses, performed either in soil and/or rock", according to which the anchoring is formed by two or more independent anchorings, resistant to tensile and/or compression stress, formed by a special or otherwise device, installed within a hole made in the soil, filled, under pressure or not, with agglutinant material, and which allows, through said device, pressure injection of two or more independent bulbs, with the load capacity of said independent anchorings being evidenced by a jack which acts on the upper end of one or more of said anchorings and reacts against the other ones, while said anchorings may be connected, with agglutinant material, forming a sole anchoring unit with its total capacity duly computed.

Inventors:
VANDERLINDE WALPY (BR)
Application Number:
PCT/BR1993/000024
Publication Date:
March 03, 1994
Filing Date:
August 11, 1993
Export Citation:
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Assignee:
GEOBRAS S A ENGENHARIA E FUNDA (BR)
VANDERLINDE WALPY (BR)
International Classes:
E02D5/48; E02D5/74; E02D5/80; E02D27/50; (IPC1-7): E21B/
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Claims:
CLAIMS
1. "IMPROVEMENTS INANCHORING SUBJECT TO TENSILE AND/OR COMPRESSION STRESSES, PERFORMED EITHER IN SOIL AND/OR ROCK", characterized by being formed by two or more independent anchorings, coaxial or not, thrust and/compression resistant, formed or not by a special device (Fig. 1), installed in a hole made in the soil 2, filled, under pressure or otherwise, with cement mortar or other agglutinant material, which may, through said special device or otherwise, have agglutinant material injected under pressure, forming two or more independent bulbs 1, separate or not, by portion which were not injected under pressure, with the load capacity of said independent anchorings being possible of being checked directly by a jack operating on the upper end of one or more of said anchorings which react against the other ones and, after said checking, the mentioned anchorings, connected by the filling of the empty spaces still existing with agglutinant material, forming one single anchoring unit with total load capacity really computed, with the special device mentioned above being formed by two or more independent assemblies of thrust and/or compression resistant elements 3a,b, concentric or not, located or not within compartments which are not communicant one to the other, annular or not, filled or not with agglutinant, formed by two or more groups of pipes or jackets, special or otherwise, made or plastic or other appropriate material 5a,b,c,d, tubular or not, corrugated or not, concentric or not, connected successively one to the other or to special supports 6a.b, with said special supports having, in each end, two or more dents, annular or not 17 a,b,c for the coupling of the pipes or tubular jackets 5a,b,c,d and having a longitudinal opening 7, centrally located or not, which assures the continuity of the internal cylindrical space of the internal injection pipes or tubular jackets 5c, and having, also, said special supports, one or more sets of longitudinal non communicating openings or holes 8a,b, destined to the passage and positioning of thrust and/or compression resistant elements and to the communication of the annular or otherwise adjacent and corresponding compartments 4a,b, allowing their filling, when necessary, with cement mortar or other appropriate agglutinant, with said special supports having radial openings 9 for the injection or reinjection, under pressure, in order to communicate the inner injection space of the pipes or central jackets 7 with the outer space of the lining pipes or tubular jackets 11, with said radial openings being enveloped and closed by elastic sleeves 12 whichANCHORING SUBJECT TO TENSILE AND/OR COMPRESSION STRESSES, PERFORMED EITHER IN SOIL AND/OR ROCK", characterized by being formed by two or more independent anchorings, coaxial or not, thrust and/compression resistant, formed or not by a special device (Fig. 1), installed in a hole made in the soil 2, filled, under pressure or otherwise, with cement mortar or other agglutinant material, which may, through said special device or otherwise, have agglutinant material injected under pressure, forming two or more independent bulbs 1, separate or not, by portion which were not injected under pressure, with the load capacity of said independent anchorings being possible of being checked directly by a jack operating on the upper end of one or more of said anchorings which react against the other ones and, after said checking, the mentioned anchorings, connected by the filling of the empty spaces still existing with agglutinant material, forming one single anchoring unit with total load capacity really computed, with the special device mentioned above being formed by two or more independent assemblies of thrust and/or compression resistant elements 3a,b, concentric or not, located or not within compartments which are not communicant one to the other, annular or not, filled or not with agglutinant, formed by two or more groups of pipes or jackets, special or otherwise, made or plastic or other appropriate material 5a,b,c,d, tubular or not, corrugated or not, concentric or not, connected successively one to the other or to special supports 6a.b, with said special supports having, in each end, two or more dents, annular or not 17 a,b,c for the coupling of the pipes or tubular jackets 5a,b,c,d and having a longitudinal opening 7, centrally located or not, which assures the continuity of the internal cylindrical space of the internal injection pipes or tubular jackets 5c, and having, also, said special supports, one or more sets of longitudinal non communicating openings or holes 8a,b, destined to the passage and positioning of thrust and/or compression resistant elements and to the communication of the annular or otherwise adjacent and corresponding compartments 4a,b, allowing their filling, when necessary, with cement mortar or other appropriate agglutinant, with said special supports having radial openings 9 for the injection or reinjection, under pressure, in order to communicate the inner injection space of the pipes or central jackets 7 with the outer space of the lining pipes or tubular jackets 11, with said radial openings being enveloped and closed by elastic sleeves 1.
2. whichANCHORING SUBJECT TO TENSILE AND/OR COMPRESSION STRESSES, PERFORMED EITHER IN SOIL AND/OR ROCK", as per the terms of claim 1, characterized also by having special centralizers 14, hollow or not, arranged, in a convenient manner, to limit the formation of anchoring bulbs 1 to the desired regions.
3. "IMPROVEMENTS INANCHORING SUBJECT TO TENSILE AND/OR COMPRESSION STRESSES, PERFORMED EITHER IN SOIL AND/OR ROCK", as per the terms of claims 1 and 2, with said anchoring being characterized by having a group of free wires, cables or bars 3a,b, fixed to an anchoring block installed at the lower end of the anchoring bulb.
4. "IMPROVEMENTS INANCHORING SUBJECT TO TENSILE AND/OR COMPRESSION STRESSES, PERFORMED EITHER IN SOIL AND/OR ROCK", as per the terms of claims 1, 2 and 3, characterized, also, for having a steel pipe or concrete pipe, centrifuged or not, or of any other appropriate material, enveloping the tensile and/or compression elements in the portion between the crown block and the upper bulb of the anchoring.
5. "IMPROVEMENTS INANCHORING SUBJECT TO TENSILE AND/OR COMPRESSION STRESSES, PERFORMED EITHER IN SOIL AND/OR ROCK", characterized by having special jackets 5d, tubular or otherwise, with successive portions of frustum of cones 5e, wedged shaped, symmetrical or not or with other appropriate shapes, which allow the successive or otherwise molding of wedges, in the agglutinant material, with such wedges, when under the stress of anchoring, developing action and reaction forces, both against the hole walls 2 or bulb 1, as well as against the surfaces of the thrust and/or compression resistant elements 3a.
Description:
DESCRIPTIVE REPORT FOR THE PATENT OF INVENTION ENTITLED: IMPROVEMENTS IN ANCHORING SUBJECT TO TENSILE AND/OR COMPRESSION STRESS, PERFORMED EITHER IN SOIL AND/OR ROCK".

As it is known in the technical field, the term "tie" means a structural element resistant to tensile or pulling stresses, introduced in the soil after the drilling of a hole in which, by the injection of an agglutinant material, generally a cement mortar, an anchoring bulb is formed which is connected to the structure, through the tensile resistant element and the tie head. The stress to be absorbed by the tie shall be transmitted to the soil only by the anchoring portions, after having traveled through the free portion. On the other hand, the term "pile" means a structural element resistant to compression and/or to thrust and which is either driven or molded, after previous drilling, into the soil, and which has the main purpose of transmitting compression stresses to the soil, either by its resistance under its lower end, or by its resistance along its lateral surface, or the combination of both. It may, also, transmit tensile stresses to the soil, in this case only through the resistance along its lateral surface.

The connotation given to an element resistant to tensile and/or compression stress in this patent is applied, generally, to rods, cables, wires, steel pipes or any other material which has such quality.

In the driven or molded piles, an agglutinant product, generally cement mortar, is injected under pressure, in order to increase the tensile and/or compression stress along its lateral surface. In such piles, the anchoring portion goes, generally, up to the stress application head, there being no free portion.

In the tie, the fixing head is formed by a special device where the tension resistant elements are attached to the supporting structure. Both in the ties and in the driven or molded piles, the anchoring portion is formed by pressure injections of an agglutinant product, generally cement mortar.

The anchorings have several applications in Engineering, amongst which we may point out the following: - Stabilization of slopes;

- Propping of excavation walls;

- Fixing of structures which are subject to sub- pressure;

- Fixing and/or increasing of the height of concrete dams;

- Foundations for buildings, soils, tanks, etc.;

- Reaction for load bearing tests.

The anchorings are different, one from the other, basically due to:

- Drilling method;

- Type and arrangement of the tensile and/or compression resistant elements;

- Injection device and system;

- Device used for fixing the head to the structure;

- Corrosion protection of the pulled and/or compressed elements;

- Inspection system of the specified load capacity.

The differences related to the drilling method are not relevant for the purposes of this patent, for the improvement therein is in the arrangement of the tensile and/or compression resistant elements, in the injection device and system, in the total protection of the tie and/or pile and in the inspection system of the specified load capacity.

The construction of anchorings, for the fixing of ties or of excavated and injected piles, faces the challenge of its basic proposition: the introduction, into the soil, of tensile and/or compression resistant elements which, by their own nature, need a permanent protection against the aggressivity of the environment and have to subject said structural elements to tensile and/or compression stresses. The problem, up to the present state of art, is to void the direct contact of the tensile and/or compression resistant elements with the soil, therefore promoting a total and permanent protection of such elements against corrosion without hindering the development of the soil/agglutinant friction, which is the basic principle of anchoring. The present state of art faces, also, the challenge of the problem relative to the computation of the compression load capacity of an anchoring element, by direct methods and in a simple and economic way, such as the one used for ties.

With such objectives, the existing patents in the field of ties have peculiarities, which may be grouped as follows:

1st. group: Non reinjectable systems;

2nd. group: Reinjectable systems. In the 1st. group, there are the processes which are characterized by the insertion of a pipe into the soil, either by rotation, percussion, wash-out or drilling, up to the determined depth. After the cleaning of the interior of said pipe, the appropriate steel frame and the agglutinant are introduced. The lining pipe is then removed and additional agglutinant matter is introduced (cement or hydraulic mortar, etc.) either under pressure or not. The free portion is protected by a plastic sheath.

The 2nd. group is formed by anchorings comprising wires (or cordages) concentrically arranged around a central pipe provided with openings in the portion corresponding to the anchoring. Such openings are closed by valves or sleeves, which avoid the backflow of the injection mortar after the pressure is over. Said valves allow the repetition of injections whenever necessary. The free portion of the wires (or cordages) is protected by a plastic sheath. The ties of the 1st. group do not allow the total utilization, in case of shortage of load capacity.

The ties of the 2nd. group do not have permanent protection against corrosion.

As for the piles, excavated and injected, also known as small diameter injected piles, rood pile and tubular micropiles, the anchoring of the tensile and/or compression resistant elements in the soil is done as follows:

ROOT PILE: The drilling is made, obligatorily, with a metal lined pipe and, after the cleaning of the interior of said pipe, the compression resistant elements (steel bars) are installed and, after the filling with the mortar, the steel pipe is removed, as the air pressure (1 to 4 kgfi\'cm^) is applied in the mouth of the lining.

TUBULAR MICROPILES: The drilling may be made by any process which keeps the hole open: the introduction of the steel pipe with valves or sleeves, through which the cement mortar is injected under pressure, in different phases; the introduction of the complementary structure within the steel pipe. None of said types allows the reinjection, in case of shortage in its load capacity, and does not allow a simple inspection of the specified working load. It is not possible to have a total protection for the metal elements against corrosion, mainly if said piles are subject to tensile stress.

With the Patent of Invention No. 7019728 and, later, with the improvement, through the Patent of Invention No. 7705314, the applicant has already introduced surprising results in the technical field, for the anchorings made under said

methods and devices have shown a complete solution for the final protection problems against corrosion of the elements subjected to tensile stress.

The now improved technique is based upon the execution of anchorings formed by several groups of thrust and/or compression resistant elements, surrounded by kits of special tubular jackets which are interconnected by special supports, which allow the injection and reinjection, under pressure, of the agglutinant agent, as many times as necessary, therefore allowing the forming of two or more bulbs or anchoring portions, separated, one from the other, by a portion which is not injected under pressure.

For a better understanding of the improved technique, we shall hereinafter make a general description of the configuration of said anchoring.

The thrust and/or compression resistant elements are constituted, basically by a set of steel wires, steel pipes, steel bars or other appropriate material, arranged in a parallel and concentric way, forming or not coaxial cables, surrounded by pipes or jackets, corrugated or not. In the anchoring portions, the position of the elements which are resistant to thrust and/or compression is achieved by the use of special supports which form elongations, in such a way to allow the connection of two or more tubular jackets, made of plastic or any other appropriate material, which keep the continuity of the annular internal space of the inner tubular injection jackets. In the upper portion, the arrangement of the thrust and/or compression resistant elements is assured, also, by simple spacers which, when the anchoring is used to support compression stress, makes it possible to confine the elements which are compression resistant, therefore avoiding the individual buckling of said elements and/or of the whole set. In this upper portion, outside the area of the bulb, the whole assembly is surrounded by a steel pipe, or of other appropriate material, in order to resist the compression, tensile or shearing stress, or a combination thereof.

In the illustrative drawings attached hereto, the basic aspects of this improvement are submitted, where: Figure 1 is a lateral view of the anchoring, pointing out the portions of the injected bulbs, characterized by the tubular corrugated protection jackets, separated one from the other by special supports, and the upper portion, not injected under pressure (free portion, when using it as a tie), characterized by the envelopment of the whole assembly of thrust and/or compression resistant elements by a steel pipe, or a pipe of any other appropriate material, to support the compression, tensile and/or shearing stresses, combined or otherwise.

Figure 2 shows, in a diagrammatic section, the upper portion of the anchoring.

Figure 3 shows, also in a diagrammatic section, the portion of the anchoring in the mid point of the special support, in the upper bulb area. Figure 4 shows a diagrammatic section, in the portion of the upper bulb, corrugated pipes or jackets, enveloping the thrust and/or compression resistant elements.

Figure 5 shows, in a cross section, the spacing portion between the anchoring bulbs. Figure 6 shows a diagrammatic section in the center of the special support, in the portion of the lower bulb.

Figure 7 shows a cross section in the lower portion of the anchoring.

Figure 8 shows a diagrammatic longitudinal section, characterizing the upper portion of the anchoring, close to the soil surface. It shows, also, the total protection of the thrust and/or compression resistant elements, with the outer centralizing members of the steel jacket.

Figure 9 shows a diagrammatic longitudinal section covering the special support in the upper bulb portion. It characterizes, further the passage of the thrust and/or compression resistant elements, through the longitudinal openings of the special supports, and the connection of the central longitudinal hole for injection with the outside, through radial openings closed by the elastic sleeve.

Figure 10 is a longitudinal section of the annular transition supports, where there is shown, also, an elastic sleeve which allows the injection for the filling of annular compartments.

Figure 11 shows diagrammatic longitudinal section covering the special support of the lower bulb portion.

Figure 12 shows, in a diagrammatic longitudinal section, the lower end of the anchoring, with indication of the tubular jacket coupling and of the assembly of elements resistant to thrust and/or compression.

Figure 13 shows a diagrammatic longitudinal section of an anchoring with the indication of special jackets with portions shaped like frustum of cone wedges.

We shall now describe each one of the elements represented in this set of drawings, and the manner how a combination of such elements may provide the improvements which constitute the object of this patent.

First of all, we shall discuss the special annular support 6a of the upper anchoring bulb, shown in figures 3 and 9.

This support, which has preferably a cylindrical shape, is characterized by having a longitudinal hole 7, normally in the central area, through which the injection of cement or of other agglutinant is made in order to form the sheath and the anchoring bulbs.

It has, also, one or more groups of longitudinal, non communicating openings, 8a,b, intended for the passage and positioning of steel wires, cables or bars, 3a,b, and radial openings 9 closed by elastic sleeves 12, which allow the communication between the central longitudinal hole 7 and the outer space in respect to the tubular jackets 11.

The elastic sleeve does not allow the backflow of the injected material towards the interior of the special annular support.

It has, also, dents 17a,b,c which connect the tubular jackets 5a,b,c. Such special tubular jackets protect the thrust and/or compression resistant elements and have dents and bosses which allow the transfer of the applied stresses to the soil.

The special support 6b of the lower anchoring bulb, seen in figures 6 and 11, is different from the one described above 6a, for not having any dent 17a and the longitudinal opening 8a.

The annular transition supports 10a,b,c sheen in figures 8 an 10 have, also, a preferred cylindrical shape, dents 17a,b,c for the coupling of the special tubular jackets 5a,b,c and/or a dent 17d for the coupling of the wires, cables or bars 3a.

Said supports serve to connect the tubular jackets in the transitions, such as that of the upper anchoring bulbs for the upper portion which was not pressure injected.

In the upper portion of the anchoring, the special transition supports are connected, externally, to a steel pipe or to a centrifuged or not concrete pipe 16, with the strength to absorb horizontal stress, bending and torsional moments, combined or otherwise, which load the anchoring.

Finally, the terminal portion 15 shown in figures 1 and 12, has dents 17b,c,d for the coupling of the tubular jackets and of the wires, cables or bars 3b.

The above mentioned embodiments serve only for the purpose of this Patent, and said parts may have the most different shapes, while maintaining the basic ideas.

We shall not describe the production phases of said anchoring.

In the first place, the special annular supports, the transition annular supports, the terminal portion and the jackets are arranged on a bench, without being coupled one to the other.

Then the wires, cables or bars are introduced within the compartments of the jackets and through the longitudinal openings of the annular supports, therefore connecting all parts.

After the assembly, the appropriate agglutinant is injected, on the bench, within the annular compartments, 4b and the longitudinal openings of the annular supports, as well as within the corresponding spaces 4a of the upper bulb portion.

After a sufficient time for the setting of the agglutinant material used in the injection on the bench, the device is placed within a hole previously drilled in the soil, with appropriate diameter with rotative or roto-hammering equipment.

Once the device is duly installed, the injection of the sheath is performed, in order to fill the total outer annular space 11 of the hole.

Then the injections for the formation of the anchoring bulbs is performed. The system allows successive reinjections, at any time, in order to allow the reaching of the specified load capacity of the anchoring.

* Such load capacity is checked by the tensile or compression test, through jacks which exert a pulling force on the assembly of the inner wires 3b, and a corresponding compression force on the assembly of outside wires 3a. Such an assembly may take a different configuration, to allow the application of tensile stress on the outside wires 3a and compression stress on the inner wires 3b, when compartment 4a is not injected and when the set of inner wires 3b is confined along the portion of the upper bulb and of the steel pipe 16, in such a way to avoid the buckling of the wires, higher individual or of the whole set. In this case, the spacer shall be eliminated, with supports 10b,c being coupled one to the other.

The improvements now submitted extend to the injected piles the possibility of inspection of their load capacity, at any time, as for the ties.

After the load test, once the anchoring is approved, the inner spaces of the anchoring are filled, through the pipe or central tubular jacket 5c and through the elastic sleeve 12 shown in figure 10.

The described device, as well as its construction system mentioned in the "Improvements in anchoring, subject to tensile and/or compression stress performed either in soil and/or rock" results in an anchoring with two bulbs injected under pressure, where the internal steel wires, cables or bars 3b act as a tie, where the lower bulb, formed in the soil, resists to a tensile stress, and where the outside assembly 3a acts as a pile, transmitting compression stress through the upper bulb.

On the other hand, as an alternative of the assembly described above, we may have also an anchoring where the set of internal wires, cables or bars 3b act as a pile, where the lower bulb formed in the soil resists to compression stresses and where the outer assembly 3a acts as a tie, transmitting tensile stresses through the upper bulb.

Such a characteristic gives the anchoring the capability of being self-stable, where one assembly acts as a reaction to load the other one.

Once the acceptance of the anchoring is checked through the appropriate standard test, it becomes clear that both anchoring bulbs resist to loads which are, at least, twice as great as the tested load.

Another advantage of the anchoring herein described is the small diameter of the drilling which is necessary for equivalent loads of anchorings existing in the market, resulting in a lower cost and bringing, therefore, larger benefits to the work.

This allows, also, an inspection of the group effect for a series of anchorings, through the simple operation of different jacks which operate simultaneously on the group of anchorings (piles or ties), therefore allowing the checking of the real operation of the anchorings (piling) under the total load which act on the structure, such as columns, tanks, bins, etc.

With the presently available technology, this checking of the pile system as a whole, for high loads, requires a gigantic reaction structure, making impossible its performance in the present works.

Another advantage of the anchoring system herein submitted, is to allow the use of the wedging effect, generated by multiple wedges 5e, cast in the agglutinant material, by the special jacket 5d with the successive cone frustums, allowing a substantial reduction of the length of anchoring bulbs 1, for the action and reaction forces developed by the wedges 5e against the walls of the hole 2 and against the surface of the thrust and/or compression resistant elements 3a, create high friction forces.