METHOD AND APPARATUS FOR REMOVING MUD FROM BELOW AN UNDERWATER CONSTRUCTION

Abstract: The invention relates to a method and apparatus for removing mud from below an under water construction by means of a tube inserted into the mud layer and moved through the mud layer from which tube (4) air is directed through a row of openings (5) in a downward and forward direction. Said tube (5) may at its outer ends have guiding flanges (16,17) connected with drawing means (19,20,21,22,23,24) for adjusting the angular position of the air jets (5). The tube (28) may be moved in an angular position with respect to the direction of movement (6) or may be V-shaped having its point directing in the direction of movement. A second tube (10) may be moved in synchron­ ism with the first tube (4) said second tube having upwardly extending outlet openings (11) for air for creating an air screen, which generates a water flow for directing the direction of flow of the air bubbles with particles generated by the first tube (4).

Description: Method and apparatus for removing mud from below an underwater construction. The invention relates to a method for removing mud from below an under water construction. Constructions which have to be placed upon the bottom of a water are, notwithstanding whether preparation of the bottom did took place of not, mostly placed on a tempory support, after which a hard supporting layer is applied in the space below the underside of the construction and the rigid bottom, which hard layer dependent from the circumstances can comprise a gravel layer, a sand layer, a mixture of sand and grout, or bags which can be filled under pressure with grout or the like. When one has to start said operations very often a mud layer has been formed in the small intermediate space between bottom and underside of the construction, which layer has to be removed first. It is known to do this with the aid of a suction conduit and suction pump, the mouth of the sunction conduit being inserted into the narrow space to suck away in this manner the mass of mud. Said known method is very complicate and insufficiently effective, in particular there where it is difficult to cover sufficiently the narrow space with the suction mouth. Purpose of the invention is to provide a method and an apparatus as well by means of which mud can be removed relatively quick in a very simple way. According to the invention this is is in the first placed achieved in that a gaseous medium is injected into the mud by means of a device which is moved through the mud layer such that said layer is gradually fluidized. By supplying air in sufficiently amount and with sufficient pressure at the correct way over a sufficiently large area the mud layer is broken open and divided into small particles which are taken away by the current generated by the air bubbles. Said air bubbles flow along the underside of the construction towards the place where they can escape upwardly and they take with them mud particles. If this takes place in a waterfiow, such as a river, then the mud particles are moved away automatically to be settled somewhere else. If this takes place in stationary water, then the mud particles will be fed upwardly adjacent to the construction, come to rest there and will settle again in which case, however, they only settle down upon the upper surface of the construction and next to the construction and accordingly no longer in the space which has to be filled with a hard layer. An example of a construction where the problems of mud deposits can occur is formed by a tunnel section which has been lowered upon a tempory support. For removing mud from below a construction having a length larger than the width the invention provides that a tube provided with openings is inserted in a direction transverse to the longitudinal axis of the construction through the mud layer, said tube having outlet openings for air over a portion which is substantially equal to the width of the construction, to which tube air is supplied while the tube is moved in the direction of the longitudinal axis. Such a tube easily can be inserted below a construction e.g. formed by a tunnel section and subsequently can be dragged through the mud layer in the direction of the longitudinal axis whilst simultaneously air under pressure is supplied. In this way it is possible to free the space from mud during one single passage. If so desired the tube can extend at an angle with the longitudinal axis of the construction, which has the result that the air bubbles generate a flow towards one side. Preferably the air jets are directed obliquely forwardly and downwardly seen in the direction of advancement. The angular position preferably is between 13 to 180 with respect to the vertical. Very good results are obtained with an angular position of 450. Preferably the angular position is adjustable to enable adaptation to the composition of the mud. According to the invention it further can be useful if, seen in the direction of movement, a second tube is provided behind the tube operating on the mud layer with air jets, which second tube is moved synchroneously with the first tube and by means of which second tube a screen of air bubbles is generated. This screen takes care that the mud fluidized by the desintegrating air jets, escapes laterally and not rearwardly. As far as it tries to escape rearwardly the flow generated by the air screen will take away the particles. Forwardly an escape is prevented by the mud layer which has not yet been desintegrated by the air jets. The invention also deals with an apparatus for applying a method according to the invention and said apparatus may comprise a tube having a row of outlet openings and having a connecting hose for pressurized air, which tube at the outer ends has circular guiding flanges to which drawing members are connected by means of which the angular position of the outlet openings is adjustable. The circular guiding flanges form slitches which by the drawing members connected to them are prevented from rolling so that the one adjusted annular position of the air outflow openings is guaranteed. It is possible as well to make the apparatus such that the tube is bent V-shaped with the point of the V directed into the direction of movement. At the location of the point of the V preferably a slide shoe has been provided. If a second tube is applied for generating an air screen, then said tube preferably is connected to the first tube and has upwardly directed outflow openings. It is observed that it is well known in the art of the maintenance of lakes or rivers to lower a tube onto the bottom of the water which tube has been provided with air outlet openings and into which air under pressure is supplied and which tube can be moved over the bottom by means such as a vessel. Examples are found in French patent specification 23 031 23 and U.S. patent specification 3,698,193. Said prior publications deal with the situation in an open environment in which there are no problems with respect to the accessibility of the mud layer. It might be astonishing that experts knowing how to remove mud layers in rivers and ponds by means of aeriation or suction never considered the possibility how to act in a more efficient way and design a more effective apparatus for removing mud layers hidden below an under water construction. The invention now will be further elucidated with reference to the drawings. Figure 1 is a schematic view of the principle of the invention. Figure 2 in the same way as figure 1 shows an alternative of the method according to the invention. Figure 3 is a top view showing the use of the apparatus according to the invention at a tunnel section. Figure 4 is a side view of figure 3. Figure 5 schematically shows the coupling of adjustable drawing members for the apparatus shown in figures 3 and 4. Figure 6 is a top view of another embodiment of the apparatus according to the invention and figure 7 shows a third embodiment. Figure 1 shows a sand layer 1 which may form the bottom of a river or other water, whilst with 2 the lower side has been indicated of a construction e.g. a tunnel section. In the shape between 1 and 2 a mud mass 3 is present. According to the invention a tube 4 is inserted into said mud mass said tube being provided with a row of outflow openings 5 directed obliquely forwardly and downwardly as seen in the direction of movement 6. The air leaving the outflow openings 5 desintegrates the mud layer and whirls it, whilst the air bubbles 7 which rise take with them the loosened particles. Said air bubbles generate an upwardly directed flow which impinges against the lower side 2 of the construction and then escapes laterally as indicated with the arrows 8 and 9. This escape of course also takes place in the longitudinal direction of the tube and accordingly transverse to the plane of the drawing and transverse to the direction of movement. Figure 2 shows the same device as figure 1 with however added to tube 4 a second tube 10 placed behind it as seen in the direction of movement and having outflow openings 11 at the top from which also an air flow can escape. Said air flow generates an air bubble screen 12 which also impinges against the lower side of the construction 2 and spreads in all directions. This flow has a portion 13 which is directed forwardly and meets the flow generated by the air bubbles 7 leaving tube 4. Due to this a flow is generated transverse to the plane of the drawing and to a restricted degree in forward direction. Figures 3 and 4 show a tunnel section 13 placed upon a tempory support 14 and 15. In the space 3 between the sand layer 1 and the lower side 2 of the tunnel section there is mud. The apparatus by means of which said mud now is removed according to the invention comprises a tube 4 which at the ends extending outside the width of the tunnel section 13 has been provided with circular flanges 16 and 17 and which within the width of the lower side of the tunnel section 13 has been provided with outflow openings 5. The tube is closed at one end and at the other end connected to a hose 18 for air under pressure. If said tube is moved in the direction of the longitudinal axis which means in the direction of the arrow 6, then the mud layer 3 gradually will be fluidized and therewith removed. Figure 5 shows an end view of the tube 4 with flange 16 and openings 5. Two rods 19 and 20 are pivotably connected to the flange at 21 and 22 the rod 20 by means of a pin at 23 being secured in one of the holds 24 of the rod 19. By the choice of one of the holes the direction of flow of the openings 5 is brought into a certain angular position which is not changed when the rod 19 is dragged in horizontal direction so that it can slide over the sand layer with the flanges 16 and 17 respectively. The tube as shown in figure 6 also can be made V-shaped having at both outer ends slide shoes 25, 26 as well as a central slide shoe 27. The width of the tunnel section has been indicated in figure 6 with the lines 13. Figure 7 shows an embodiment in which the tube 28 extends at an angle to the direction of movement 6 having slide shoes 29, 30 at the outer ends. It is observed that the tube can be moved with the speed of e.g. 0.20 meter per minute or less. A higher speed is possible as well, however, e.g. of the magnitude of 0,35 meter per minute. The escaping quantity of air can change and can be adjusted between a quantity of 1000 to 4000 liters per minute.

Claims: CLAIMS 1. Method for removing mud from below an underwater construction, characterized in that a gaseous medium is injected into the mud by means of an apparatus which is moved through the mud layer such that said layer is gradually fluidized. 2. Method according to claim 1 for removing mud from below a construction having a length larger than the width, characterized in that a tube provided with openings is extended through a mud layer in a direction transverse to the longitudinal axis of the construction, said tube being provided with outflow openings for air over a portion which is almost equal to the width of the construction, air under pressure being supplied to said tube whilst the tube is moved in the direction of the longitudinal axis. 3. Method according to claim 2, characterized in that the tube extends at an angle with the longitudinal axis of the construction. 4. Method according to claim 2 or 3, characterized in that the air jets are directed obliquely forwardly and downwardly as seen in the direction of movement. 5. Method according to claim 4, characterized in that the outflow opening lies between an angle of 30 - 80" with respect to the vertical. 6. Method according to one or more of the preceding claims 2 to 5 inslusive, characterized in that seen in the direction of movement a second tube is placed behind the tube which operates upon the mud layer with air jets which second tube is moved synchroneously with the first tube and by means of said second tube a screen of air bubbles is generated. 7. Apparatus for applying the method according to one or more of the preceding claims 1 to 6 inclusive, characterized in that it comprises a tube having a row of outflow openings and a connection hose for pressurized air, which tube at the outer ends has circular guiding flanges to which drawing members are connected by means of which the angular position of the outflow openings is adjustable. 8. Apparatus for applying the method according to one or more of the preceding claims 1 to 6 inclusive, characterized in that the tube is bent V-shaped with the point of the V directed in the direction of movement. 9. Apparatus for applying the method according to claim 6, in particular apparatus according to claim 7 or 8, characterized in that behind the tube a second tube is placed having upwardly directed outflow openings.

Inventors: KNOOK, THEODORUS WILHELMUS THOMAS
Applicants: VAN HATTUM EN BLANKEVOORT B.V., VOLKER STEVIN CIVIL ENGINEERING B.V.
Application year: 1983
Main classification: E02D17
IPC codes: E02F5, E02B1, E02D17, E02B3