FR2682975A1 - METHODS AND DEVICES FOR REMOVAL OF EXUDATION WATER FROM PRESSURE CONDUITS. - Google Patents

Abstract

To eliminate the exudation water formed in the grout (13) protecting, in their vertical sheath (3), the prestressing strands (2) with twisted wires, a bell (9) is placed on the anchor block ( 7) from the upper ends of the strands, a sealing (15) is formed in this bell such that communication between the sheath and the bell is possible only through the interstices separating the wires from the strands, a point (P) of the sheath to an upper grout reserve (12, 13) by a side pipe (11) and at the same time a vacuum is made in the bell by a pump (16).

Description

Methods and devices for removing exudation water

prestressing ducts.

  The invention relates to methods and

  positive intended to eliminate the exudation water coming from the cement grout injected into the vertical sheaths, or more generally having at least one section inclined on the horizontal, containing cables or strands of prestressing for concrete works, water which separates from said grout when it is set and which is

  collects in the upper parts of said sheaths.

  It relates more particularly to the case where the prestressed cables considered are constituted by strands or bundles of metallic wires, generally twisted, wires of which at least one end is stripped

  to be able to be securely clamped by an anchor jaw

  ge. It is of course necessary to avoid permanent contact between the water and the stripped portions of these strands to avoid the risks of corrosion, in particular by rust. This is one of the missions of the cement grout injected into the sheaths and filling the spaces, of these sheaths, not occupied by the strands: this grout indeed forms a protective coating for the bare portions

in question.

  The injection of the above grout is carried out in the liquid state in the sheaths from one of their ends and this grout, from its injection and during its subsequent setting, gradually separates into two masses, the one, hardened and relatively dense, and the other, liquid and lighter, corresponding to the water initially present in the grout and which collects above

the solidified mass.

  In the case where the strands and their sheaths are vertical or inclined to the horizontal, the liquid portion collects in the upper part of the sheath and, when these sheathed strands have a great length -which can exceed for example 20 or even 100 meters and more, as in the case of "off shore" concrete structures the length of the portion of each sheath which is filled with water at the end of the setting

  grout can reach several meters.

  Several solutions have been proposed for removing this water and replacing it with grout, in particular in FRANCE patents no 76 26800 (publication no 2 363

679) and 91 00 330.

  According to these solutions, elimination devices of the kind in question are made to include: on the one hand, a bell sealingly covering the anchoring block of the upper ends of the sheathed cables considered, oriented vertically, and, on the other hand , a lateral injection pipe connecting an upper reserve of grout to a lateral point of the sheath, point arranged in the vicinity of the level of separation between the two solid and liquid phases of the grout at the end of the separation of the water from exudation, level which is generally located a little lower than the narrowed lower end of the trumpet containing the open upper end of the cable and connecting vertically to the anchor block

upper sheath.

  For each of these solutions, it is necessary to wait until the exudation water coming from the main volume of grout injected into the whole of the sheath is collected in the upper part of this sheath to then push said water through the block of anchoring using an additional volume of grout injected through the

lateral tubing.

  The invention provides a variant of the above solutions

  which has a number of advantages, especially with regard to simplicity and speed

  of implementation, as well as the efficiency of filling

  final sage in grout of the sheaths considered.

  To this end, the devices for eliminating exudation water of the type in question according to the invention are essentially characterized in that they further comprise:

  a watertight seal formed on the anchor block

  ge, inside the bell, so that the

  munication between the interior volumes of the sheath and

  of the bell is carried out exclusively by the inter-

  stices comprised between the constituent wires of the strands, and a source of vacuum connected to the bell so as to be able to suck successively outside of the latter the air and water contained in the sheath, to

through the interstices above.

  As for the methods of eliminating exudation water using the above devices, they are essentially characterized according to the invention by the following steps: the communication being cut off between the reserve of grout to be injected and the sheath, the vacuum is applied in the bell, which creates a vacuum in the sheath by suction of the air initially contained in this sheath through the "interstices" included between the wires of the strands constituting the cable, then, when the degree of this vacuum has reached a sufficient value, establishing communication between the grout reserve and the sheath while continuing to apply the vacuum in the bell, which has the double effect of completely filling the sheath in grout and repelling the exudation water coming from this grout towards the bell, by discharging it through the above interstices and said bell, finally, when no more exudation water is collected at the outlet of the said interstices, we stop applying the depression in the bell and we cut the

  communication between the grout reserve and the sheath.

  At this point in the description, it is appropriate to

  recall that it has already been proposed: on the one hand, to expel the exudation water coming from the protective grout of a prestressing cable housed in its sheath through the interstices between the different wires making up the upper end of the strands constituting said cable, by a "chimney effect" generated by an upward push of the grout during injection (see patent FRANCE NO 2

188 004),

  on the other hand, to inject such a grout into its sheath by prior vacuuming of the interior volume thereof and subsequent communication of the sheath with a reserve of grout in the liquid state or at all

  less fluid enough (see FRG patent no. 1 684 437).

  However, these two techniques had not been used simultaneously before the invention and only their combination here proposed makes possible perfect and rapid elimination of the exudation water from the grout concerned.

  The invention comprises, apart from these arrangements

  main provisions, certain other provisions which are preferably used at the same time and which will be

  more explicitly question below.

  In the following, a preferred embodiment of the invention will be described with reference to

  drawing appended hereto in a way understood without limitation

  tive. Figures 1 and 2 of this drawing show

  schematically a device for eliminating exhaust water

  dating established according to the invention, respectively during two successive phases of the process used for

ensure this elimination.

  Figure 3 is an enlarged section of

  one of the strands included in the above device.

  In a manner known per se, a concrete structure 1 of great height, such as a nuclear reactor casing or a dam buttress is reinforced by at least one cable composed of strands 2 which are housed side by side in a sheath 3 inclined to the horizontal or oriented vertically. Each strand 2 is composed of a bundle of metallic wires 4.5 (FIG. 3) comprising a central core 4 surrounded by a plurality of strands 5 twisted around

from her.

  As clearly visible in FIG. 3, this beam reveals, between the different wires 4 and 5, small interstices i having in cross section

the shape of a curved triangle.

  The section of these interstices i is such that they can be traversed longitudinally by the air and by

  water, but not the grout injected.

  The open upper end of each cable is housed in a trumpet 6 or frustoconical sleeve which

  is connected to the upper end of the cor-

  corresponding, and the upper ends of the strands 2 are individually anchored in a block 7, which they

  cross, using suitable jaws 8.

  The block 7 is itself supported on the structure 1 by means of an annular seat, for example

  consisting of a flange 61 extending horizontally-

  outwardly the upper end of the trumpet 6 and it is capped by a bell 9 also resting on said collar 61 in a sealed manner and communicating with the outside through a connector

higher 10.

  In addition, a lateral tube 11 embedded in the structure 1 connects a lateral point P of the sheath 3 to a

  external receptacle 12 containing grout to be injected 13.

  Point P is very close to the upper end

  lower of the sheath: it is arranged at a distance L, generally between 0.5 and 3 meters, below

of the anchor block 7.

  A valve 14 mounted on the upper end of the tubing 11, projecting above the structure 1, makes it possible to establish communication between this tubing

and the receptacle base 12.

  In addition, and in accordance with the present invention, a "sealing" or plug 15 is formed on the block 7, inside the bell 9, in order to seal the assembly of the block 7 and the jaws. 8 which it carries, with the exception of the interstices i above: for this purpose, the upper ends of the different strands 2 are made to overlap above the sealing 15, as well

visible in Figures 1 and 2.

  The sealing 15 can be made of any desirable material such as a cement mortar or a resin. In addition, the connection 10 is connected to a vacuum source 16 such as a vacuum pump with interposition

of a water collecting tank 17.

  That said, we proceed as follows.

  The valve 14 being initially closed, the vacuum is applied in the bell 9 using the vacuum pump 16, which has the effect of sucking towards this pump 16, through the said bell 9 and the tank 17, the volume of air contained in the sheath 3: this volume is sucked through the interstices i, as shown diagrammatically by the arrows f in FIG. 1, then from the bell 9

to pump 16 (arrow F).

  We thus very quickly achieve a relative vacuum-

  pushed inside the sheath 3.

  When the degree of this vacuum is considered to be sufficient, and that for example the pressure prevailing inside the sheath 3 is no more than of the order of 5

  at 20 millibars, the valve 14 is opened.

  This opening puts the grout mass 13 to be injected into communication with the vacuum chamber constituted by the sheath 3 and the tube 11: this mass therefore flows immediately, under the combined effect of vacuum and gravity, through the tubing 11, up to point P (arrow G) and, from this point, inside the sheath 3, first downwards (arrow H), then, when the filling of the sheath reaches the point P, upwards until complete filling of the sheath and

trumpet 6 (arrow K).

  During this filling, we continue to apply

  quer the depression in the bell 9 (arrow F).

  Experience shows that the cumulative effect of said filling -due itself both to the previous vacuum and to the gravity and of the permanent suction exerted towards

  the top through the interstices i has the effect of

  kill a "forced exudation" of the water comprised by the grout being injected and push this water, first upwards, then through said interstices,

  towards tray 17: this forced expulsion of exudate water

  tion up is represented in bell 9 by the

arrows g in Figure 2.

  Experience also shows that, after a relatively short period T following the opening of the valve 14, no more water is collected at the outlet of the interstices i, which means that all of the water exudation of the grout injected into the sheath 3 was eliminated. The duration T is short compared to the times usually required to obtain a natural gathering of the grout exudation water at the top of the sheath, times which generally exceed two or three hours, the time T generally being of the order of

only a quarter of an hour.

  Of course, as soon as we notice the end of the elimination of the exudation water, we can consider the operation of filling the sheath 3 with grout as finished and therefore close the valve 14, stop the pump at vacuum 16 and collect the bell 9 and the reserve 12 for

other fillings.

  It is then necessary to complete the sealing of the sheath thus filled with grout at the interstices i by covering the first sealing 15 with a second finishing sealing (not shown) in which are,

  this time, completely submerged the upper ends

strands 2.

  As a result of what, and whatever the mode of

  adopted implementation, there is a method for eliminating

  ner the exudation water from the protective grouts of the prestressing cables in their vertical sheaths - or at least having at least one section inclined to the horizontal which has many advantages compared to those previously known, in particular as regards is about simplicity, efficiency and speed

of the implementation.

  As goes without saying and as it already follows from the foregoing, the invention is in no way limited to those of its modes of application and embodiments which have been more especially envisaged; on the contrary, it embraces all variants, in particular: those where a grout pump would be used to raise the reserve of grout to be injected to a level higher than the top of the sheath to be filled and / or to perfect at the end of injection filling of the sheath obtained essentially by the combined effect of vacuum and gravity, and those where the sheath considered would have

  only one or more sections inclined on the horizon-

  tale, extending for example along a sinuous line

included in a vertical plane.

Claims (2)

  1 Device for removing the exudation water from the cement slurry (13) injected into a sheath (3) having at least one section inclined to the horizontal and containing a prestressing cable made up of strands (2) for concrete structure (1), comprising, on the one hand, a bell (9) sealingly covering the anchoring block (7) at one end of the sheathed cable considered, and, on the other hand, a lateral tube injection (11) connecting an upper reserve (12) of grout to a lateral point (P) of the sheath, characterized in that it further comprises a sealed sealing (15) formed on the anchoring block (7 ), inside the bell (9), so that the communication between the interior volumes   sheath (3) and bell (9) is made ex-   clusively by the interstices (i) included between the various wires making up the strands (2), and a source of vacuum (16) connected to the bell so as to be able to suck successively outside of it the air and the water contained in the sheath (3), through the interstices (i) above.   2 A method of eliminating exudation water using the device according to claim 1, characterized by the following steps: the communication being cut between the reserve of grout to be injected (12,13) and the sheath (3 ), the vacuum is applied in the bell (9), which creates a vacuum in the sheath by suction of the air initially contained in this sheath through the "interstices" (i) between the wires of the strands constituting the cable (2), then, when the degree of this vacuum has reached a sufficient value, the communication is established between the reserve (12) of grout and the sheath while continuing to apply the vacuum in the bell, which has a double effect to completely fill the sheath with grout, by the combined action of vacuum and gravity, and to push the exudation water from this grout back   the bell, by evacuating it through the interstices below   above and said bell, finally, when we no longer collect exudation water at the outlet of said interstices, we stop applying the vacuum in the bell and we cut the   communication between the grout reserve and the sheath.