Method for manufacturing an element comprising a grout activation cycle

Abstract

A method for manufacturing an element in a ground comprising a drilling step during which a grout comprising a first composition is introduced and after the drilling step, at least one grout activation cycle is performed during which at least part of the grout is pumped; a second composition configured to activate the grout by reacting with the first composition in order to initiate the hardening of said grout is added to the pumped grout; then the activated grout is introduced into the excavation; and after said at least one grout activation cycle, the activated grout is allowed to harden in order to form the element in the ground.

Claims

1. A method for manufacturing an element in the ground, the method comprising: a drilling step during which an excavation is drilled into the ground using a drilling tool, while introducing into said excavation a grout comprising a first composition; after the drilling step, at least one grout activation cycle is performed during which: at least part of the grout is pumped; a second composition is added to the pumped grout configured to activate the grout by reacting with the first composition in order to initiate the hardening of said grout; then the activated grout is introduced into the excavation; after said at least one grout activation cycle, the activated grout contained in the excavation is allowed to harden in order to form the element in the ground.

2. The method according to claim 1, further comprising a control step in which at least one physicochemical parameter of the pumped grout is measured and said at least one activation cycle is stopped when the value of said at least one physicochemical parameter becomes greater than a predetermined upper threshold or lower than a predetermined lower threshold.

3. The method according to claim 2, in wherein the predetermined upper threshold, respectively the predetermined lower threshold, is determined from said at least one physicochemical parameter measured for the activated grout.

4. The method according to claim 2, wherein said at least one physicochemical parameter is chosen from conductivity, pH, viscosity, temperature or the concentration of a specific ion of the pumped grout.

5. The method according to claim 2, wherein the physicochemical parameter of the pumped grout is measured on the surface, outside the excavation.

6. The method according to claim 2, wherein the amount of the second composition added in the pumped grout is adjusted during said at least one grout activation cycle, as a function of said physicochemical parameter measured on the pumped grout.

7. The method according to claim 1, wherein said at least one activation cycle for grout comprises, after adding the second composition to the pumped grout, a mixing step in which the pumped grout is mixed with the second added composition, using a mixing tool.

8. The method according to claim 7, wherein the mixture of the pumped grout with the second composition is performed above ground and/or in the excavation.

9. The method according to claim 1, wherein the grout is pumped from a lower part of the excavation, preferably near the bottom of the excavation.

10. The method according to claim 1, wherein the activated grout is introduced into the excavation in an upper part of said excavation.

11. The method according to claim 1, wherein the first composition of the grout comprises at least one non-activated aluminosilicate component or a silicate and aluminate compound.

12. The method according to claim 11, wherein said at least one non-activated aluminosilicate component is chosen from: a blast furnace slag, fly ash, a calcined clay, for example of the metakaolin or kaolin type, a clay of the bentonite, kaolinite, smectite, illite, attapulgite or sepiolite type, or a mixture of these.

13. The method according to claim 1, wherein the second composition comprises an alkaline preparation, for example an alkaline powder or an alkaline solution.

14. The method according to claim 13, wherein the alkaline preparation is an alkaline preparation of sodium, potassium or calcium, in particular chosen from: a preparation of sodium or potassium carbonate; a preparation of sodium, potassium or calcium silicate; a preparation of sodium, potassium or calcium hydroxide; a preparation of calcium oxide; a preparation of sodium, potassium, or calcium sulphate; or quicklime, slaked lime or air lime, or a combination of these.

15. The method according to claim 1, wherein at least one of the first and second compositions comprises at least one adjuvant configured to delay or accelerate the hardening of the activated grout or to fluidize the activated grout.

16. An installation for manufacturing an element in the ground, the installation comprising: a drilling tool configured to drill an excavation in the ground; an introduction device configured to introduce into the excavation, during drilling, a grout comprising a first composition; a grout activation device comprising: a pumping means configured to pump the grout, after drilling; a means for treating the grout configured to add into the pumped grout a second composition configured to activate the grout by reacting with the first composition in order to initiate the hardening of said grout; a means of introducing activated grout into the excavation.

17. The installation according to claim 16, further comprising a control device comprising at least a first measuring instrument configured to measure at least one physicochemical parameter of the pumped grout, the control device being configured to stop the addition of the second composition into the pumped grout when the value of said at least one physicochemical parameter becomes greater than a predetermined upper threshold or becomes lower than a predetermined lower threshold.

18. The installation according to claim 17, wherein said at least one first measuring instrument is disposed on the surface, outside the excavation, upstream of the grout treatment means.

19. The installation according to claim 17, wherein the control device comprises: at least one second measuring instrument disposed downstream of the grout treatment means and configured to measure said at least one physicochemical parameter for the activated grout; and a threshold determination module configured to determine the predetermined upper threshold, respectively the predetermined lower threshold, from said at least one physicochemical parameter measured for the activated grout.

20. The installation according to claim 16, comprising a mixing tool configured to mix the pumped grout with the second composition added.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0097] The present disclosure will be better understood on reading the following description of embodiments of the present disclosure given by way of non-limiting examples, with reference to the attached drawings, in which:

[0098] FIG. 1 illustrates the initial state of a method for manufacturing an element according to the present disclosure;

[0099] FIG. 2 illustrates a drilling step of the method according to the present disclosure;

[0100] FIG. 3 illustrates a step of removing the drilling tool of the method according to the present disclosure;

[0101] FIG. 4 illustrates an installation for implementing the method according to the present disclosure;

[0102] FIG. 5 illustrates the start of the activation cycle of the method according to the present disclosure;

[0103] FIG. 6 illustrates an intermediate step of the activation cycle of the method according to the present disclosure;

[0104] FIG. 7 illustrates the end of the activation cycle;

[0105] FIG. 8 illustrates an element manufactured in the ground by means of the method according to the present disclosure;

[0106] FIG. 9 illustrates the change in the conductivity of the pumped grout as a function of the mass concentration of the second composition; and

[0107] FIG. 10 illustrates the change in the compressive strength of the manufactured element as a function of the mass concentration of the second composition.

DESCRIPTION OF THE EMBODIMENTS

[0108] The present disclosure relates to a method for manufacturing an element in the ground. This method makes it possible to manufacture an element such as a temporary retaining screen or a waterproofing screen by activating a drilling grout.

[0109] Using FIGS. 1 to 7, we will describe a non-limiting embodiment of the method, in accordance with the present disclosure, for manufacturing an element E in the ground S. The method is implemented by means of an installation 10 manufacturing an element in the ground according to the present disclosure. This installation is also illustrated in FIGS. 1 to 7.

[0110] The installation 10 comprises a drilling machine 12, comprising a drilling tool 14, configured to drill an excavation into the ground S. The geometry of the excavation depends on the drilling tool 14. The tool here is cylindrical. As can be seen in FIG. 2, the installation 10 also comprises an introduction device 16 configured to introduce grout into an excavation. In this non-limiting example, the introduction device 16 comprises a spray nozzle disposed at the distal end of the drilling tool 12. As a variant, and in a non-limiting manner, the introduction device 16 may comprise a conduit opening at the head of the excavation and allowing the grout to be introduced into the excavation as said excavation is drilled.

[0111] As shown in FIG. 4, installation 10 further comprises a grout activation device 20. The grout activation device 20 comprises a pumping means 22. The pumping means 22 comprises suction conduit 24 configured to extend into an excavation and suction nozzle 26 arranged at the distal end of the suction conduit and configured to be disposed in an excavation.

[0112] The activation device 20 also comprises a treatment means 30 for a grout configured to add a second composition to the pumped grout. The treatment means 30 comprises tank 32 configured to receive said second composition and a treatment conduit 34. The treatment conduit 34 and the suction conduit 24 come together at a mixing tool 36. In this non-limiting example, the mixing tool 36 comprises an in-line mixer. In a non-limiting manner, the mixing tool may be static or comprise a mobile element. Treatment conduit 34 is fitted with a valve 35 capable of taking an open or closed position, which may or may not authorize the circulation of the second composition present in the tank towards the mixing tool 36.

[0113] The activation device 20 further comprises a means 38 for introducing an activated grout into an excavation. In this non-limiting example, the introduction means 38 consists of an introduction conduit configured to be connected to the mixing tool 36 and to open into an upper part of an excavation, close to the surface. The introduction means 38 could comprise an introduction nozzle disposed at the end of the introduction pipe.

[0114] In FIG. 4, it is noted that the installation 10 comprises a control device 40 comprising a first measuring instrument 42 and a second measuring instrument 44.

[0115] The first measuring instrument 42 is configured to measure at least one physicochemical parameter on a grout pumped from an excavation and circulating in the suction conduit 24, upstream of the grout treatment means 30, and upstream of the mixing tool 36. In this non-limiting example, the first measuring instrument 42 is configured to measure said physicochemical parameter on the surface, outside the excavation.

[0116] The second measuring instrument 44 is configured to measure at least one physicochemical parameter on an activated grout circulating in the introduction conduit 38 and intended to be introduced into the excavation. The second measuring instrument 44 is configured to measure said physicochemical parameter downstream of the grout treatment means 30 and the mixing tool 36.

[0117] The control device 40 further comprises a control unit 46 with which the first and second measuring instruments 42, 44 communicate. The control unit 46 is able to control the valve 35 in order to stop the circulation of the second composition from the tank 32 to the mixing tool 36, in particular depending on the physicochemical parameters measured by the first and second measuring instruments 42, 44. The control unit 46 comprises a threshold determination module.

[0118] The method for manufacturing an element in the ground will now be described in detail using FIGS. 1 to 7.

[0119] As shown in FIG. 1, the drilling machine 12 is initially supplied equipped with drilling tool 14. The ground S is devoid of excavation.

[0120] A drilling step is then performed, illustrated in FIG. 2, during which an excavation H is drilled into the ground using the drilling tool 14. During drilling, a grout F comprising a first composition is introduced into said excavation, using the introduction device 16. Said grout then plays the role of a drilling fluid. In particular, the grout allows hydrostatic pressure to be exerted on the walls of the excavation to prevent them from collapsing.

[0121] This grout F introduced during drilling is inert and non-activated, such that it is configured not to harden until the first composition reacts with an activating composition. The first composition of the grout comprises at least one non-activated aluminosilicate component chosen from: a blast furnace slag, fly ash, a calcined clay, for example of the metakaolin or kaolin type, a clay of the bentonite, kaolinite, smectite, illite, attapulgite, sepiolite type or a mixture of these.

[0122] During tests conducted by the inventors, the grout F is made up of water in an amount of 920 litres per cubic metre (L/m.sup.3), bentonite in an amount of 45 kilograms per cubic metre (kg/m.sup.3) and blast furnace slag in an amount of 185 kg/m.sup.3. The density of this grout F is approximately 1.15. The first composition of the grout therefore comprises a mixture of bentonite and blast furnace slag.

[0123] The grout may also contain an adjuvant configured to delay or accelerate curing of the grout.

[0124] The retarding adjuvant can be chosen from the family of gluconates, lignosulfonates, calcium, sodium or ammonium phosphonates as well as from salts derived from citric acid, boric acid or sodium citrate.

[0125] The accelerator adjuvant can be chosen from calcium, sodium and ammonium salts, for example calcium carbonate, calcium chloride, calcium sulphate, calcium nitrate, sodium silicate, sodium aluminate.

[0126] The adjuvant can also be a superplasticizer chosen from the following families: polynaphthalene sulfonate, polymelamine sulfonate, polycarboxylate ether, sodium polyacrylate, pyrophosphate or sodium hexametaphosphate.

[0127] As shown in FIG. 3, and in a non-limiting manner, the drilling tool 14 is extracted from the excavation H. Excavation H is then filled with non-activated grout F introduced during the drilling step by means of the introduction device 16.

[0128] As can be seen in FIG. 4, the elements of the installation 10 allowing the activation of the grout F are then put in place, and in particular the activation device 20, the treatment means 30 and the control device 40. The suction conduit 24 of the pumping means 22 is disposed in the excavation so that the suction nozzle 26 extends near the bottom of the excavation H. The introduction conduit 38 is connected to the mixing tool 36 and is positioned so as to open into an upper part of the excavation H, close to the surface.

[0129] The suction conduit 26 and the introduction conduit 38 are initially empty while the tank 32 is filled with a second composition C. The valve 35 is initially closed. This second composition C is an activation composition, comprising activator components. This second composition C is configured to react with the first composition of the grout F initially introduced into the excavation H when drilling, in order to activate this grout F and initiate its hardening.

[0130] In a non-limiting manner the second composition C comprises an alkaline preparation, which is in this non-limiting example an alkaline solution, which may be an alkaline solution of sodium, potassium or calcium, in particular chosen from: a solution of sodium or potassium carbonate; a solution of sodium, potassium or calcium silicate; a solution of sodium, potassium or calcium hydroxide; or a solution of calcium oxide; or a combination of these.

[0131] In a non-limiting manner, the alkaline solution could be replaced by an alkaline powder consisting of the same compounds as the alkaline solution.

[0132] During the tests, and in a non-limiting manner, the inventors retained a second composition C comprising limewater (CaO), or quicklime, at a rate of 20 L/m.sup.3.

[0133] This second composition may also contain an adjuvant configured to delay or accelerate the hardening of the grout or to fluidize it.

[0134] Then an activation cycle for the grout F present in the excavation H is performed using activation device 20, illustrated in FIGS. 5 to 7.

[0135] During this activation cycle, as illustrated in FIG. 5, a step of pumping the grout F is performed using the pumping means 22. Grout F is sucked up by the suction nozzle 26 from the bottom of the excavation H and is transported to the surface, outside the excavation, via the interior of the suction conduit 24. The grout F is brought to the treatment means 30.

[0136] In conjunction with the activation cycle, a control step is performed during which, using the first measuring device 42, a plurality of physicochemical parameters on the pumped grout F is measured. These physicochemical parameters are measured outside the excavation, upstream of the treatment means 30 and the addition of the second composition C. As a variant, these physicochemical parameters could be measured in the excavation, for example at the suction nozzle 26.

[0137] In this non-limiting example, the pH, conductivity and density of the pumped grout F are measured. The initial pH measured on the pumped grout, before starting the addition of the second composition C, is 9.9. The initial conductivity of the pumped grout is 1.32 millisiemens per centimetre (mS/cm) and the initial density of the pumped grout is 1.15.

[0138] Said physicochemical parameters are advantageously measured continuously throughout the activation cycle. An advantage is to be able to follow the evolution of these parameters.

[0139] As shown in FIG. 5, the activation cycle further comprises a step according to which the second composition C is added into pumped grout F, using said treatment means 30. More precisely, the valve 35 is open to allow the flow of the second composition C and bringing the pumped grout F into contact with the second composition. Bringing the first composition of the pumped grout, comprising bentonite and blast furnace slag, into contact with the second composition C comprising calcium oxide has the effect of activating the pumped grout F and initiating its hardening, by reaction of the second composition with the first composition.

[0140] Pumping of the grout from the excavation is continued during this step of adding the second composition C.

[0141] After adding the second composition C into the pumped grout, the pumped grout F is mixed with the second composition C added using the blender tool 36. An advantage is to improve the homogeneity of the mixture obtained and therefore of the activated grout F. At the output of the mixing tool 36, activated grout F circulates in the introduction conduit 38. As a variant, mixing could be performed in the excavation.

[0142] The activated grout F is then introduced into the excavation, routing it into the excavation H by means of the introduction conduit 38, as indicated by the arrows in FIG. 5. Activated grout F is introduced into the upper part of the excavation, close to the surface.

[0143] By continuing the activation cycle, and as illustrated by going from FIG. 5 to FIG. 6, activated grout F gradually takes the place of the non-activated grout F within the excavation H. In the excavation, the amount of non-activated grout F, initially introduced during drilling, gradually decreases, while the activated grout F is gradually driven towards the bottom of the excavation H and gradually fills said excavation, as illustrated in the intermediate step of FIG. 6.

[0144] In this non-limiting example, the physicochemical parameters mentioned above are also measured, i.e., pH, conductivity and density on the activated grout F. This measurement is performed using the second measuring instrument 44, downstream of the addition of the second composition C and downstream of the mixing tool 36. The measurement is performed on the surface, outside the excavation, but could be performed in the excavation. The values of these physicochemical parameters serve as references and indicators of grout activation.

[0145] The activation cycle is continued, and the physicochemical parameters continue to be measured on the pumped grout F and on the activated grout F. These parameters change over time.

[0146] Each of the physicochemical parameters measured is associated with an upper threshold or a lower threshold. The upper and lower thresholds are determined by a threshold determination module of the control unit 46 of the control device 40. In this non-limiting example, the upper and/or bas predetermined thresholds are determined for each of the three physicochemical parameters from said physicochemical parameters measured for the activated grout F, using the second measuring instrument 44. More precisely, the value of said physicochemical parameters measured on the activated grout F is chosen as a predetermined upper threshold for these parameters. In accordance with the measurements made on the activated grout, the predetermined upper threshold for pH is set at 12, the predetermined upper threshold for conductivity is set at 8.5 mS/cm+/?0.5 mS/cm and the predetermined upper threshold for density is set at 1.16.

[0147] When the value of at least one of the physicochemical parameters measured by the first measuring instrument 42 becomes greater than the predetermined upper threshold associated with it, the activation cycle is stopped. To do this, the control unit 46 of the control device 40 compares the value of the physicochemical parameters measured on the pumped grout F at the predetermined upper thresholds. The control unit 46 then orders the interruption of the addition of the second composition into the pumped grout F, which is reflected in this non-limiting example by the closing of the valve 35. It is then considered that all of the grout initially introduced during drilling has been activated or, at the very least, a satisfactory quantity of grout has been activated.

[0148] For example, FIG. 7 illustrates a final state of the activation cycle in which all of the grout has been activated. It is seen that the excavation is entirely filled with activated grout F. As a result, all of the grout has been activated and the already activated grout is now pumped. The values of the physicochemical parameters measured on the pumped grout are then substantially equal to the values of said parameters measured on the activated grout, and greater than or equal to the predetermined upper thresholds.

[0149] Grout pumping is interrupted. Then the activation device 20 and the treatment means 30 are removed and the activated grout is allowed to harden in the excavation, until the element is formed in the ground.

[0150] FIG. 8 illustrates the element E formed in the ground S, by implementing the method according to the present disclosure, described previously.

[0151] FIG. 9 illustrates the change in conductivity, measured using the first measuring instrument 42, of the grout pumped during the activation cycle, depending on the mass concentration of second composition C added into the pumped grout F, for two different grouts. It is seen that the conductivity gradually increases with the introduction of the second composition C into the pumped grout, until reaching a maximum. This maximum corresponds to the total activation of the pumped grout, and the predetermined upper threshold can be set slightly lower than this maximum.

[0152] Beyond this maximum, the conductivity no longer increases, so that the introduction of the second composition can be stopped. Activation of the grout is achieved, and the grout is then saturated with activator.

[0153] FIG. 10 illustrates the change in the compressive strength, expressed in Megapascals (MPa) measured using the first measuring instrument 42, on a grout pumped during the activation cycle, as a function of the mass concentration of second composition C added in the pumped grout F.

[0154] It is noted that the compressive strength increases with the addition of the second composition C, until reaching a maximum, then remains constant once this maximum is reached. The addition of the second composition can then be interrupted.