EP2530237A1 - Sludge treatment plant associated with a tunnel boring machine with a pressurised heading face and method for managing such a plant. - Google Patents

Abstract

The installation has a collecting and evacuation unit i.e. tank (13), for collection and evacuation of non-utilized sludges (B3). A directing unit (14) is interposed between a sludge regeneration unit (6) and a sludge mixture preparation unit i.e. container (8), and directs a portion of regenerated and source sludges (B0, B1) issued from the preparation unit toward the collecting and evacuation unit. The directing unit directs only the part of the regenerated sludges issued from the regeneration unit toward the collecting and evacuation unit in an adjustable manner. An independent claim is also included for a method for management of a sludge treating installation.

Description

The invention relates to a sludge treatment plant associated with a pressurized leading-edge tunneling machine and to a method for managing such a station.

A tunnel pressurized front end is a public works machine comprising, in the front part, a circular shield, one side is equipped with a rotary cutting wheel. This cutting wheel digs a tunnel whose diameter substantially corresponds to the diameter of the shield. The cutting wheel works under pressure. It is mounted at the front of a chamber, called the slaughter chamber, depending on the direction of travel of the tunnel boring machine.

The rear part of the tunnel boring machine, called the follower train, comprises, in addition to various devices allowing the circulation of fluids between the tunnel and the surface, all the devices for piloting, safety and setting up the voussoirs constituting the tunnel. A tunnel boring machine drills the ground a distance corresponding generally to the width of a voussoir before stopping to ensure the establishment of the latter from the follower train. To ensure its advance in the ground, the tunneling machine advances by building on the voussoirs previously set up.

The cutting wheel works under pressure to balance the hydrostatic pressure exerted by the geological layers on the TBM shield. The pressures exerted by the ground on the cutting wheel are generally between 1 and 5 bar and may in some cases be greater than 12 bar.

This type of TBM is particularly used either to intervene in terrain, having a high hydrostatic pressure, or in land with pulverulent materials and / or with high risk of clogging due, for example, to a clay soil nature.

Mud is injected under pressure to the front of the leading edge from the slaughter chamber. This sludge, in addition to a lubrication role of the cutting wheel, ensures the stability of the walls of the excavation. The sludge, brought from the surface, also makes it possible, during its return trip to the surface, to ensure the transport of the materials resulting from the excavation. The circulation of the sludge in the slaughter chamber thus makes it possible to maintain a constant pressure at the level of the cutting wheel. Pressurizing the mud thus injected at the front of the tunnel boring machine is carried out by pumps, called pickling pumps. If necessary, a compressed air bubble created behind the slaughter chamber completes the pressure maintenance.

The sludge used generally includes bentonite. Such a clay, because of its rheological qualities, is injected on the cutting edge in order to consolidate and stabilize the latter by forming an impermeable coating on the walls, which makes it possible to keep the excavation in shape until it is put into place. in place of the voussoirs.

Bentonite is a non-Newtonian clay that has the property of being liquid when it is in motion, that is to say when it is conveyed in pipes and / or projected, and to form a rapidly drying paste in absence of stress, that is to say at rest, when projected on the walls of the excavation.

The sludge entering and leaving the tunnel boring machine is managed by a sludge treatment and preparation station which is permanently connected to the tunnel boring machine head. This station must ensure a regular supply of sludge both in quantity, that is to say in flow, as in quality, especially with respect to specific rheological characteristics. For this, it is appropriate to adapt the mud to the nature of the soil that digs the tunnel boring machine. This soil can be more or less clay, more or less hard with the presence of so-called polluted areas, especially in urban areas. Polluted areas include, for example, portions of concrete structures, which is typically the case at the beginning and at the end of digging of the tunnel since the tunnel boring machine must drill the wall of the well through which it was lowered or by which it will be reassembled. The pollution may also consist of gypsum or areas of salt that will also alter the characteristics of the mud.

Moreover, it is necessary to adapt the characteristics of the injected mud to the drilling constraints related to the nature of the soil and / or the interventions to be carried out on the tunnel boring machine. The sludge injected on the cutting edge may thus consist exclusively of so-called mother sludge, that is to say an aqueous solution of bentonite or, conversely, consisting solely of recycled sludge and / or without bentonite . Indeed, the spent sludge from the cutting wheel comprises a portion of the injected mother sludge, unused, and clearing materials. This used sludge is, initially, recycled.

It is therefore necessary to control and optimize in real time the so-called pickling sludge that is injected at the leading edge of the tunnel boring machine, that is to say the mixture comprising mother sludge, therefore the new sludge that contains freshly dissolved bentonite, and mud already used, called recycled or regenerated. For this, the characteristics of the pickling sludge are continuously adapted to the conditions encountered by the cutting wheel.

To optimize sludge management, we know by FR-A-2,754,850 a sludge treatment station where, upstream of a tank forming a sludge buffer reserve prior to its injection at the cutting wheel, there is a treatment tank in which the mixing of the mother sludge and recycled . This tank is provided, upstream, a means for evacuating the surplus of the slurry mixture. This means is formed by a float valve. In this way, only a given quantity of the sludge mixture produced in the treatment tank is taken. Using this float valve, excess sludge is directed to a used sludge storage tank prior to its treatment as ultimate waste, for example, by pressing into slabs.

Such a solution makes it possible to have, permanently, a given amount of sludge corresponding to the mixture that is to be reinjected and which has been prepared in the pickling tank. This tray provides a constant and steady flow of sludge at the cutting wheel.

Such a solution, known as high level management, nevertheless results in the rejection, in some cases, of a sludge mixture very rich in mother sludge, and therefore in bentonite, and this in relatively large proportions. In other words, even if this system makes it possible to optimize the volume balance of sludge by compensating in particular for any loss of sludge in volume and maintaining the balance of the mass flow rate, that is to say having a known density mud reinjected at the cutting wheel, it remains nonetheless, in the case where the mother sludge is present in large quantities in the circuit, a significant amount of this mother sludge, made from bentonite, is not used at all and is directly treated as waste.

This is all the more marked that, during certain maintenance operations, to secure the slaughter chamber in which personnel intervene, is injected a slurry consisting of almost mother sludge, that is to say a almost pure bentonite solution. This injection is done without passing through the mixing tank, before the intervention. Once the intervention has been carried out, during the restart, the float valve is in a position where the lines are purged and thus the mother sludge remaining in the pipes is removed and not used, in order to maintain the flow rate.

Conversely, in some cases, it is not necessary to have a high percentage of mother sludge in the pickling sludge, which may be almost exclusively composed of regenerated sludge. Furthermore, it is interesting to avoid incorporating, temporarily, the mother mud in the pickling sludge, for example when the tunnel boring machine drills in polluted soil, to avoid pollution of the mother sludge. In this case, recycled sludge may be suitable.

Moreover, the operation of such a float valve is controlled by the single level of sludge in the tank, without the possibility of adjustment. Moreover its maintenance is not easy.

It is to these drawbacks and constraints that the invention particularly intends to meet by proposing a sludge treatment station to optimize the quality of pickling sludge, while limiting the loss of mother sludge before its first use.

To this end, the subject of the invention is a sludge treatment plant associated with a pressurized front-end tunneling machine, comprising at least one first means of regeneration of the sludge coming from the tunneling machine leading edge, a second means of preparation of new sludge called mother sludge, a third means for preparing a mixture of sludge for use in the leading edge, said pickling sludge, from sludge from the first and second means, a fourth feed means the pickling mud leading edge, a fifth means for collecting and discharging the unused and non-regenerable sludge, a sixth means, interposed between the first and third means and adapted to direct to the fifth means a portion of the sludge from the third means, characterized in that the sixth means is adapted to adjustably direct to the fifth means only a portion of the regenerated mud from the first way.

Thus, with this sixth means, it is possible to inject into the third preparation means of the sludge mixture only the necessary quantity of regenerated sludge and thus, thereby, to optimize the quantity of mother sludge to be incorporated into the pickling sludge. This allows, at least, to limit the release of "new" sludge before its first use. The sludge discharge to be carried out to adapt the rheology and / or the flow rate and / or the density of the pickling sludge is made prior to the injection of mother sludge into the pickling sludge, from the regenerated sludge.

• le sixième moyen comprend au moins une vanne papillon disposée sur le trajet de la boue entre le premier moyen et le troisième moyen.
• Au moins une vanne de sécurité, de type tout ou rien, est disposée en amont de la vanne papillon selon le sens d'écoulement de la boue.
• Le sixième moyen est disposé pour alimenter par gravité au moins un bac constitutif du cinquième moyen.
• Le bac constitutif du cinquième moyen est relié par une conduite à un bac intermédiaire situé en sortie du troisième moyen et propre à recevoir la boue de marinage.
• Le bac intermédiaire est relié par une conduite, d'une part, à un bac de stockage temporaire de la boue de marinage et, d'autre part, par une conduite à un bac d'alimentation du tunnelier en boue de marinage.
• Au moins une conduite de liaison entre les différents moyens est équipée d'une vanne permettant de régler le débit de boue transféré.
• Au moins un bac constitutif du quatrième moyen est pourvu d'un capteur de niveau.

According to advantageous but non-compulsory aspects of the invention, such a station can incorporate one or more of the following characteristics:

• the sixth means comprises at least one butterfly valve disposed in the path of the sludge between the first means and the third means.
• At least one safety valve, all or nothing type, is arranged upstream of the butterfly valve in the direction of flow of the sludge.
• The sixth means is arranged to feed by gravity at least one tank constituting the fifth means.
• The tank constituting the fifth means is connected by a pipe to an intermediate tank located at the outlet of the third means and adapted to receive the pickling sludge.
• The intermediate tray is connected by a pipe, on the one hand, to a temporary storage tank of the pickling sludge and, on the other hand, by a pipe to a feed tank of the tunneling machine pickling sludge.
• At least one connecting line between the different means is equipped with a valve for adjusting the transferred sludge flow rate.
• At least one tank constituting the fourth means is provided with a level sensor.

• a) définir des caractéristiques voulues de la boue de marinage,
• b) selon les caractéristiques définies à l'étape a), adapter les caractéristiques de la boue régénérée,
• c) selon les caractéristiques définies aux étapes a) et b), produire de la boue mère avec des caractéristiques données,
• d) définir la quantité de boue présente dans le quatrième moyen,
• e) à l'aide du sixième moyen, n'utiliser que la quantité nécessaire de boue régénérée pour obtenir, par mélange de la boue régénérée avec la boue mère, les caractéristiques voulues de la boue de marinage.

The invention also relates to a method of managing a treatment station as mentioned above comprising at least steps consisting of:

• a) define desired characteristics of the pickling sludge,
• b) according to the characteristics defined in step a), to adapt the characteristics of the regenerated sludge,
• c) according to the characteristics defined in steps a) and b), to produce mother sludge with given characteristics,
• (d) define the quantity of sludge present in the fourth means,
• (e) Using the sixth method, use only the required amount of regenerated sludge to obtain, by mixing the regenerated sludge with the parent sludge, the desired characteristics of the pickling sludge.

• la figure 1 est un diagramme synoptique d'une telle station de traitement des boues conforme à l'invention et
• la figure 2 est un diagramme illustrant la gestion des caractéristiques des boues dans la station de traitement des boues illustrée à la figure 1.

The invention will be better understood and other advantages thereof will appear more clearly on reading the following description of a sludge treatment plant according to the invention, given solely as an example and made with reference to the accompanying drawings in which:

• the figure 1 is a block diagram of such a sludge treatment station according to the invention and
• the figure 2 is a diagram illustrating the management of sludge characteristics in the sludge treatment plant illustrated in figure 1 .

A tunnel boring machine 1 is schematically and partially shown, in longitudinal section, in the lower right part of the figure 1 . Only the front part of the TBM, ie the shield, is represented. The follower train, known per se, is not illustrated. A cutting wheel forms the front end of the tunnel borer intended to be in contact with the ground to be excavated. It comprises a rotating wheel 2, provided with cutting and / or abrasive elements 3. The cutting wheel 2 is rotatably mounted about a longitudinal axis A of the tunnel boring machine 1. The Thus, the wheel 2 drills the ground in a direction parallel to the longitudinal axis A of the tunnel boring machine 1, this direction corresponding to the path of the tunnel boring machine in the ground.

At the rear of this cutting wheel 2 is a chamber 4 maintained, if necessary, in pressure by a bubble of compressed air. Such a case occurs during maintenance operations, in particular when changing the cutting elements of the wheel 2. For this, the tunnel boring machine moves back to clear a space between the wheel 2 and the ground allowing the operators to intervene. In order to guarantee their safety and to limit the risks of collapse, compressed air is injected into this space. This room 4 is called slaughter room. It communicates with the outside of the tunnel boring machine and participates with slurry injection pumps, called pickling pumps, to send under pressure, both laterally and frontally, sludge at the cutting wheel 2. These injections of mud are represented by arrows F and L.

This sludge is intended not only to facilitate drilling, by lubricating the wheel 2, but also, once solidified, to consolidate and stabilize the excavation, behind the wheel 2. Such sludge is referred to in the following "mud of marinage B2 ".

The pickling sludge B2 is fed to the wheel 2 by pipes from the surface. Other pipes allow, from the slaughter chamber 4, to collect unused pickling sludge, that is to say not solidified, as well as excavated materials. These are driven by the unused pickling sludge in order to evacuate them to the surface.

Waste sludge B is the mixture of unused pickling sludge B2 and excavation debris that is discharged to the surface. Thus, a portion of the pickling sludge B2 remains in the tunnel as wall reinforcement product and a part forms a means of transport excavated materials.

The spent sludge B coming from the tunneling machine 1 is collected at the rear of the chamber 4 and fed via conduits 5 to a first means 6 for regenerating the sludge.

This first means 6 is located on the surface, near the working area of the TBM. It comprises several devices, known per se, to recycle sludge B. For this, sludge B goes into a first device to evacuate debris of larger size, typically more than 6 mm. This first device performs an operation called scalping or precranking. In the following operations, the sands, that is to say the debris of caliber less than 6 mm, are evacuated. These operations are called desanding or desanding and desilting or trimming, depending on the size of the treated debris.

This first means 6 comprises, in the example, devices 60, 61, 62, known per se, successively respectively providing the pre-screening, the grit removal and the settling of the sludge B. The pre-screening apparatus comprises a rotary filter 60 called trommel. Descaling and settling devices include hydrocyclones 61, 62 whose characteristics are adapted to the geology of the lands crossed and therefore to the mud B to be treated.

Separated and unusable solid materials, namely large debris or pebbles 63 and sands 64 from apparatuses 60 to 62 are dewatered and removed, before use for example as backfill or in cement plants.

As a function of the needs for B2 pickling sludge and thus of the nature of the terrain, the operations carried out by the first means 6 are adapted, in particular with regard to the characteristics of the apparatuses 60 to 62 and / or their number.

Thus, at the outlet of the first means 6, a sludge called regenerated sludge B0 comprising water, a certain quantity of fine, solid materials from the excavated soil and which have not been recovered by the apparatus 60 to 62 is obtained. and B2 pickling sludge. This sludge B0 is in fact a sludge B resulting from the tunneling work from which excavation debris was removed, at least the largest ones.

This regenerated B0 sludge can be reinjected into the tunneling machine slurry supply system. Advantageously, the regenerated sludge B0 is mixed with new sludge, called mother sludge B1, before being returned to the tunnel boring machine.

The sludge treatment plant comprises a second means 7 for preparing the new sludge B1. The apparatus constituting this second means 7 comprises a silo 70 for storing bentonite. The rheological characteristics of this type of clay are known and mastered. In particular, bentonite is a non-Newtonian, thixotropic type clay, its apparent viscosity diminishing with shear and this in a reversible manner. In addition, its ability to absorb water and inflate is used to seal some structures, for example basins.

A mixing apparatus 7, also known per se, dissolves the bentonite from the silo 70. The aqueous solution of the bentonite is made from water from the network stored in a reservoir 72. new sludge, called mother sludge B1, which is stored in at least one buffer tank 73 before any use.

The sludge treatment plant comprises a third means 8 for preparing the sludge intended to be re-injected at the leading edge of the tunnel boring machine 1. This sludge, referred to as a pickling sludge B2, is prepared in a tank 8, called tank marinating, having two compartments 80, 81 independent and not communicating with each other. In a non-illustrated embodiment, the tray 8 comprises more than two compartments.

A compartment 80 is connected to the first means 6 for regenerating the sludge. Thus, the compartment 80 receives the regenerated sludge B0. The other compartment 81 is connected to the buffer tank 73 containing mother sludge B1. This second compartment 81 is also connected to the tank 72 of clean water and another tank 82 of recycled water. This recycled water comes, on the one hand, from the first means 6 for treating the sludge B and, on the other hand, from a treatment of the unused sludge B3 which is stored in a fourth means 13 for collecting and separating the sludge B. evacuation of unused and non-regenerable sludge. This sludge B3 is, in ultimate treatment, separated by means 9 in water and solid waste 10. The solid waste 10 are, in known manner, compacted and intended for use in public works, for example as backfill. In a variant not shown, the compartment 81 is connected only to a tank 72 of clean water or a tank 82 of recycled water.

The compartment 81 is also equipped with devices 11 for injecting additives, for example polymers, carbon dioxide to adjust the pH or any other element that one would like to incorporate into the mixture intended to prepare the pickling sludge B2. For this purpose, the two compartments 80, 81 are provided with adjustable flow inlet and outlet lines either by gravity or by means of valves known per se. These valves allow, if necessary, to prevent any circulation in the pipe. Thus, the means 8 makes it possible to collect sludge B0 and B1 before distributing them, in a controlled manner, in a means of feeding the tunnel boring machine.

The pickling sludge B2, obtained at the outlet of the third preparation means 8, by mixing mother sludge B1 and regenerated sludge B0, is thus directed towards a fourth means 12 for supplying the tunneling machine 1 with pickling sludge B2. This fourth means 12 comprises at least one tank 120 for temporary storage of the sludge B2, the capacity of which, if necessary, ensures the supply of sludge B2 of the cutting wheel 2 of the tunnel boring machine, for the time necessary to the security of the attack front, that is to say for example when setting up a voussoir. The capacity of the tank 120 generally corresponds to at least 15 minutes of operation of the tunnel boring machine.

The tray 120 is connected by at least one pipe 121 variable flow allowing, if necessary, to isolate the tray 120 to a tank 122 supply tunneling machine. This tray 122 is also connected by a variable flow line 810 to the compartment 81. For more legibility, the valve, known per se, ensuring the variation of the flow is not illustrated. Thus, it is possible to directly send mother sludge B1 in the TBM 1 without being mixed with regenerated sludge B0.

The fourth means 12 also comprises an intermediate tray 123, connected to the pickling tank 8. The connection is double. It is carried out directly with the compartment 80 and with an outlet of the tank 8 common to the two compartments 80, 81. Thus, the tank 123 can receive the mother sludge B1 and / or the regenerated sludge B0. Advantageously, the tank 123 is fed simultaneously and adjustably sludge B0 and B1. In other words, the tank 123 homogenizes the sludge B0, B1 prior to their injection into the tank 120.

For this purpose, the tank 123 is connected, with a possibility of variation of the flow, and therefore of the insulation, to the tank 120, which makes it possible to adjust in quality and in quantity the sludge buffer stock B2 before its injection into the tunnel boring machine.

It should be noted that in this station, variations in flow rates are preferably carried out by pumps and valves. Some valves are isolation valves, all-or-nothing type.

The tray 123 is also connected, directly and in a controlled manner, to the feed tray 122 by an adjustable flow pipe 124, thus providing a bypass type connection. It is possible, thanks to the pipe 124, to inject sludge into the tunnel boring machine, without passing through the buffer tank 120.

The tank 123 is also connected to the fifth means 13 for collecting and evacuating the unused sludge B3.

This fifth means comprises a tank 13 connected to the various means 6, 8, 9 and 12. This tank 13 has a volume adapted to the quantities of sludge to be treated and their solid particles charge, so the nature of the drilled soil. Advantageously, the tank 13 is adapted to receive the unused sludge produced during the operation of the tunnel boring machine. If necessary, several tanks 13, possibly of different volumes, are cascaded or in parallel.

The tank 13 is connected to the tank 123 by a pipe 130 with an adjustable flow rate. The pipe 130 makes it possible, if necessary, to inject sludge into the intermediate tank 123. This injection via the pipe 130 is particularly usable when the tank 13 essentially comprises regenerated sludge B0. An overflow 131 makes it possible to return sludge B2 from the tank 123 into the tank 13.

A pipe 132 connects the tank 13 to means 9 and 10 for separating the sludge B3 in water and in the solid phase in the form of pressed slabs. The means 9, 10 thus ensure the final treatment of unused B3 sludge to turn it into ultimate waste.

The tank 13 is also connected to a sixth means 14 for selective distribution of the regenerated sludge B0.

This sixth means 14 is interposed in the path of the regenerated sludge B0 between the outlet of the first means of regeneration of sludge B0 and the third means 8 for preparing pickling sludge B2. It allows to adjustably direct part of the regenerated sludge B0 to the fifth means 13. In other words, once recycled, that is to say freed of solid waste, the regenerated sludge B0 is not all redirected to the third means 8 to be mixed with mother sludge B1 in view of the preparation of sludge B2 and its sending into the tunnel boring machine. Only the necessary quantity of sludge B0 is reinjected into the circuit for preparing the pickling sludge B2 at the third means 8. The unused sludge B0 is directed directly to the fifth means 13 through the same means 14 to be processed and turned into ultimate waste.

For this, the sixth means 14 advantageously comprises at least one butterfly valve 140 or any other type of valve allowing a controlled and therefore variable opening of the regenerated sludge feed B0 of the third means 8.

This manages the level of sludge present in the different bins 120, 122 and 123, in order to maintain a given level in the bins. For this, at least one level sensor, not shown, is installed in at least one of the bins 120, 122, 123. Advantageously, sensors are installed in the bins 120 and 123.

In another embodiment not illustrated, all the tanks 120, 122, 123 are provided with a level sensor.

Advantageously, at least one safety valve 141, of all or nothing type, is provided upstream of the valve 140 in the direction of flow of the sludge B0.

The presence of a butterfly valve 140 makes it possible to control the instantaneous and cumulative flow rates of the sludge B0 coming from the first means 6. It is possible to dispose otherwise the constituent members of the first means 6. In particular, the hydrocyclones 61, 62 are not more necessarily arranged in height to feed by gravity means 14.

Thus, the fifth means 13 collects only the amount of regenerated sludge B0 that will not be reused. In other words, the tank 13 is fed, in normal operation, only by regenerated sludge B0 and not by mother sludge B1. However, a large quantity of high quality sludge B1, so with a content of strong bentonite, in B0 sludge directed towards the tank 13 and then to the means 9, 10 of treatment, induces difficulties of preparation, clogging apparatus. The presence of pickling sludge B2 in the tank 13 is exceptional and only occurs by overflow of the tank 123 into the tank 13, by the overflow 131. Similarly, if the compartment 81 is the only one to supply the tank 123, it can, by overflow via the overflow 131, feed sludge B2, the tank 13. In this case, it is possible to reinject it into the circuit, that is to say in the tray 123 by driving 130. The pipe 130 is used to feed the tank 123 connected directly via the pipe 124 to the tank 122 when the tank 120, is isolated. Thus, by the pipe 130, from the tank 13 and through the tank 123, it ensures the supply of the sludge B2 of the feed tray 122. Such a circuit is used, for example, when the ground is contaminated with concrete and that it is desired to protect the tank 120 containing pickling sludge B2.

The pipe 130 thus allows, in a controlled manner, by gravity, to supply the tank 123 with regenerated sludge B0, in order to adapt the characteristics of the pickling sludge B2 injected into the tunnel boring machine.

Such a configuration and the presence of the sixth means 14 does not pollute the feed bins 120, 122, 123 containing pickling sludge B2, that is to say any plant potentially containing mother sludge B1, therefore bentonite in large proportions.

The position of the sixth means 14, upstream of the compartments 80, 81 and the tank 123, thus on the only circuit of the regenerated sludge B0, induces that the sludge B1 can no longer be discarded before its first use.

All the tanks 13 and the tanks 80, 81, 120, 122, 123 in which the sludges B0, B1, B2, B3 are stored for a longer or shorter duration are provided with mixing means known per se, as well as with other instruments and sensors such as flowmeter, sampler, density, turbidity, pH, temperature or other parameters.

This processing station equipped with the sixth means 14 optimizes the management of sludge B, B0, B1, B2 and B3, including mastering the costs associated with the production of mother sludge B1. This optimization is carried out on the basis of a process which is now described with reference to the figure 2 .

The station is adapted to, if necessary, operate even when the tunnel boring machine is at a standstill, for example to reconstitute the sludge reserves B1, B2 or to treat the sludge B3 in order to empty the tank 13. It is thus possible, when the tunnel boring machine is stopped, treat the sludge B and B3, redo the levels in the different tanks and / or prepare mother sludge B1.

Furthermore, it is possible to modify an existing sludge treatment station to incorporate the various means of treating the sludge evoked, in particular the means 14 for distributing the sludge B0. The other facilities concern, in addition to the number, the dimensioning and connecting lines between the various tanks and tanks, the establishment of an automatic management of the operation of the station.

An example of a method for managing the characteristics of sludge in the station is now described.

From sensors, not illustrated and known per se, located at the level of the leading edge, the geological nature of the soil to be drilled is known and thus, in a first step, the flow rate Q2 and the density d2 are defined, that is that is, the rheology, of the sludge B2 to be injected at the level of the cutting wheel 2.

Taking into account the characteristics of this sludge B2 and the sludge B coming from the tunneling machine, the parameters of the first regeneration means 6 are adapted in a second step, in order to obtain a regenerated sludge B0 of known characteristics, therefore with a flow rate Q0 and a density d0 given.

In a third step, depending on these characteristics of sludge B0 and B2, mother sludge B1 is produced with given rheological characteristics, namely with a given flow rate Q1 and density d1, in particular by varying the concentration of bentonite.

In a fourth step, at the outlet of the first means 6, at the sixth means 14, it directs to the preparation tank 8 only the necessary amount of regenerated sludge B0 for, with the mother sludge B1, to obtain the quality and quantity wanted the B2 pickling sludge. If necessary, additives will be incorporated during the preparation of pickling sludge B2. The surplus, unused, sludge B0 is then discharged into the tank 13.

If it is necessary, at the level of the leading edge, high-quality reaming slurry B2 to secure the tunnel walls, for example in the event of intervention, it is possible to inject only the mother sludge B1, passing directly from the compartment 81, to the feed tank 122, bycircuiting the buffer tank 120, through the pipe 810. The sludge passes primarily by the pump because the level of the sludge B2 in the tray 122 is lower than that B2 sludge in the trays 120, the latter bringing the necessary complement of sludge directly from the compartment 80 to the tanks 123 and 122.

Conversely, if sludge of low rheological quality is required, for example to drill in polluted soil, practically only regenerated sludge B0 can be used. For this, by closing the valve 140, the flow of sludge B0 is directed in the compartment 80 and as via the tank 123, to the tray 122 in short circuit the tray 120 which contains pickling sludge B2 ready for use during a next cycle.

In a variant, by opening the valve 140, provided that its dimensions are adapted if necessary to fill the tank 13, and by isolating the tank 8 from the tank 123, the sludge B0 of the tank 13 is injected through line 130 into the tray 123 and then directly into the tray 122, as before.

The management of the characteristics of the sludge B2 to be injected is carried out, by a PLC, based on calculations based on data collected at different locations of the station, among other things from measurements of flow, level in the tanks, density. This involves, among other things, defining the characteristics of the mother sludge B1 that must be prepared and the amount of regenerated B0 sludge to be incorporated according to the desired characteristics of the sludge B2 to be injected at the tunnel boring machine.

Flow and density measurements are made, by known means, at the inlet and outlet of the various sludge treatment means 6, 7, 8, 13, it being understood that all the connecting pipes between the various means are equipped with valves to adjust the sludge transfer rate, this setting also allows for a maximum or no flow.

Some mathematical formulas allowing the calculation of the different pre-established characteristics of mother sludge B1 and B2 marrying are now described using references Q0 to Q3 which represent the flow rates of sludge B0 to B3, expressed in m3 / h and the references d0 to d3 which represent the densities of these sludges.

For example, from the density d1 of the mother sludge B1, the formula (D-1) x1000 × K, with K which is a coefficient given by the relation K = γ _s / γ _s -1 with γ _s designating the The actual specific density of a soil particle makes it possible to obtain a solids concentration expressed in kg / m3. This formula applied to sludge B0 to B2 makes it possible to know the concentration in dry matter of these sludges.

It is thus easy to calculate the dry matter concentration of sludge B1, either to be prepared or prepared. In such a configuration, the flow rate Q1 of the mother sludge B1 is equal to the flow rate Q2 of the sludge B2 multiplied by the density difference between the recycled sludge B0 and the pickling sludge B2 that divides the density difference between the recycled sludge B0. and mother B1. This relationship satisfies the following equation: $$\mathrm{Q}\mathrm{1}\mathrm{=}\mathrm{Q}\mathrm{2}\mathrm{x}\left(\mathrm{d}\mathrm{0}\mathrm{-}\mathrm{d}\mathrm{2}\mathrm{/}\mathrm{d}\mathrm{0}\mathrm{-}\mathrm{d}\mathrm{1}\right)\mathrm{.}$$

The flow rate of sludge discharged to be treated as ultimate waste, that is to say the flow rate Q3 of spent sludge B3 is equal to the flow rate Q0 of regenerated sludge B0 plus the flow rate Q1 of mother sludge B1 minus the flow rate Q2 of sludge. B2 marinage reinjected into the TBM. In other words, the flow rate Q3 of sludge B3 intended for the ultimate treatment is obtained by difference between the flow rates Q0, Q1 of the sludges B0, B1 entering the treatment station and the flow rate Q2 of the sludge B2 on leaving. This relation satisfies the following equation: Q3 = (Q0 + Q1) -Q2.

The other flow rates and concentrations of sludge are also deduced from these equations.

From the flow and density measurements, it is therefore possible to calculate and adapt the flow rates Q0, Q1, Q2 of the sludges B0, B1, B2 as well as the mother sludge concentration B1 to be prepared.

It should be noted that the parent sludge B1 may include, if necessary, not only bentonite but also incorporation at a given percentage of local clay. This makes it possible to vary the mother sludge concentration B1 of a mother sludge composed exclusively of bentonite to a mother sludge composed exclusively of local clay, this sludge preferably having characteristics close to that of the bentonite when is in aqueous solution. This incorporation of local clay is advantageously carried out at the level of the second preparation means 7.

An automaton, applying these equations from density and flow measurements, makes it possible to manage the opening and closing of the various valves arranged at various points of the circuit in order to vary the flow rate and / or the concentration and / or the density. B2 sludge preparation, including its content of bentonite, so mother sludge B1.

In particular, as a function of the quantity of mother sludge B1 necessary to produce the pickling sludge B2 and the level of the trays 120, 123, the automaton opens more or less the butterfly valve 140 in order to evacuate a given quantity of regenerated sludge B0, before being sent to the tanks 120, 123. In this way, a volume is released in the circuit corresponding to that of the mother sludge B1 to be added: there is therefore no more loss, at the level of the sixth means 14, mother sludge B1 not yet used.

This controls the leakage rate of sludge B0 as ultimate waste.

Such a station operates, preferably and if the nature of the ground so ready, using a gravity feed of different bins and tanks.

This treatment station not only makes it possible to manage the mud leaks occurring, for example, at the tunnel boring machine or the various pipes of the station but also to limit the use of mother sludge B1 based on bentonite which allows to limit the cost and to better manage the quantities injected and treated in the station and this by adapting the latter continuously if necessary in mud TBM.

Claims (9)

Sludge treatment plant associated with a tunneling machine (1) with a pressurized leading edge, comprising at least a first means (6) for regenerating the sludge (B) originating from the leading edge of the tunnel boring machine, a second means (7) ) for the preparation of a new sludge called mother sludge (B1), a third means (8) for preparing a mixture of sludge for use in the leading edge, called pickling sludge (B2), from the sludge (B0). , B1) from the first (6) and second (7) means, a fourth means (12) for feeding the slurry forehead (B2) pickling, a fifth means (13) for collection and evacuation sludge (B3) not used and non-regenerable, a sixth means (14) interposed between the first (6) and third (8) means and adapted to direct to the fifth means (13) a portion of the sludge (B0 , B1) derived from the third means (8), characterized in that the sixth means (14) is adapted to adjustably steer towards the fifth means n (13) only a portion of the regenerated sludge (B0) from the first means (6). Sludge treatment plant according to claim 1, characterized in that the sixth means (14) comprises at least one butterfly valve (140) arranged on the sludge path (B0) between the first means (6) and the third means (8). Treatment plant according to Claim 2, characterized in that at least one on-off type safety valve (141) is arranged upstream of the butterfly valve (140) in the direction of flow of the sludge (B0). . Treatment station according to one of the preceding claims, characterized in that the sixth means (14) is arranged to feed by gravity at least one tray (13) constituting the fifth means. Treatment station according to claim 4, characterized in that the tray (13) constituting the fifth means is connected by a pipe (130) to an intermediate tray (123) located at the outlet of the third means and adapted to receive the pickling sludge (B2). Treatment plant according to claim 5, characterized in that the intermediate tank (123) is connected by a pipe, on the one hand, to a temporary storage tank (120) of the pickling sludge (B2) and, on the other hand, on the other hand, by a pipe (124) to a feed tank (122) of the pickling sludge machine (B2). Treatment plant according to one of the preceding claims, characterized in that at least one connecting line (130, 131, 121, 810) between the different means is equipped with a valve (140, 141) for adjusting the sludge flow (B, B0, B1, B2, B3) transferred. Treatment station according to one of the preceding claims, characterized in that at least one tray (120, 122, 123) constituting the fourth means (12) is provided with a level sensor. Method for managing a treatment station according to one of the preceding claims, characterized in that it comprises at least steps consisting of: - a) defining the desired characteristics (Q2, d2) of the pickling sludge (2), b) according to the characteristics defined in step a), adapting the characteristics (Q0, d0) of the regenerated sludge (B0), - c) according to the characteristics defined in steps a) and b), to produce mother sludge (B1) with given characteristics (Q1, d1), d) defining the quantities of sludge (B2) present in the fourth means (12), - e) using the sixth means (14), use only the required amount of regenerated sludge (B0) to obtain, by mixing the regenerated sludge (B0) with the mother sludge (B1), the desired characteristics (Q2, d2) pickling sludge (B2).

Images