Method and apparatus for cutting underwater structures

A method for the cutting of underwater structures below the level of the sea bottom on which they are installed, comprises determining an ideal plane of cutting, having considered the characteristic features of the structure i.e. its morphology and its positioning on the bottom, the shape and consistency of the bottom itself, and the depth below the level of the bottom at which the cut must be effected; positioning and anchoring of a cutter in proximity of the cutting area; obtainment of at least one perforation or boring in proximity of the structure through the bottom at least up to the predetermined level for the cutting of the structure, along a direction parallel to the cutting direction and preferably lying on the cutting plane; and introduction of the cutter inside the perforation or boring and cutting of the structure. An apparatus for carrying out the method is also provided.

FIELD OF THE INVENTION

The present invention relates to a method and an apparatus for cutting underwater structures.

The cutting of submerged structures, with the purpose of removal and/or substitution of same, is presently effected by adopting different methods and by utilising apparatus of different nature.

BACKGROUND OF THE INVENTION

There are known devices for the cutting of submerged structures which operate with fixed blades, such as the one described for example in the document U.S. Pat. No. 3,056,267, or provided with several rotary blades co-ordinated in their action as in the document U.S. Pat. No. 4,180,047. Both apparatus however present the disadvantage of operating only on the emerging and free end of the submerged structure.

In the document EP-B-0 540 834, owned by the same applicant, there is described a method and a device for cutting underwater structures which make use of a diamond cable as cutting means; the device permits the cutting of the underwater structure at any level comprised between the bottom end and the surface.

Presently, the new provisions which are in force practically everywhere, and which are extremely more severe as for what concerns the environmental impact, require that the cutting of the submerged structures cannot be effected by leaving the residual stump of the structure emerging from the (sea) bottom, but instead by effecting the cut below the level of the bottom itself. Under these conditions, by utilising the presently available means, it results necessary to remove a relevant quantity of sea bottom around the base of the structure to be cut. This further operation, besides being costly, is frequently damaging as for what concerns the environment, which on the contrary this type of “underground” cutting would tend to safeguard.

SUMMARY OF THE INVENTION

An object of the present invention is therefore to provide for a method for cutting the underwater structures which permits the cutting below the level of the bottom and with a minimum expenditure of means and of energies, and with an impact with respect to the marine environment which is as limited as possible, obtained with a minimum removal of material from the bottom.

A further object of the present invention Is to provide an apparatus adapted for carrying out the thus conceived cutting method.

One object of the present invention is therefore a method for the cutting of underwater structures below the level of the sea bottom on which they are installed, comprising the following phases:determination of the ideal plane of cutting, having considered the characteristic features of the structure i.e. its morphology and its positioning on the bottom, the shape and consistency of the bottom itself, and the depth below the level of the bottom at which the cut must be effected;positioning and anchoring of the cutting means in proximity of the cutting area;obtainment of at least one perforation or boring in proximity of the structure through the bottom at least up to the predetermined level for the cutting of the structure, along a direction parallel to the cutting direction and preferably lying on the cutting plane; andintroduction of the cutting means inside said perforation or boring and cutting of the structure.

According to a preferred embodiment of the method according to the invention, there are obtained preferably two perforations or borings having parallel axes, and arranged in such a manner that the structure to be cut is placed between the said perforations or borings.

The positioning and the anchoring of the cutting means is effected both on the bottom in proximity of the structure to be cut, and onto the structure itself.

A further object of the invention is an apparatus for carrying out the method according to the invention, comprising means for perforation or boring, means for cutting which comprise a cutting frame and a movable cutting unit, means for positioning said perforation means and said cutting means, and anchoring means. Advantageously said perforation means and said cutting frame are associated, and the means for the positioning and anchoring of the perforation means and of the cutting means are the same.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

InFIG. 1there is shown the apparatus intended to perform the method according to the present invention. Reference numeral1designates the supporting base of the apparatus, having a substantially rectangular shape, which is provided in proximity of each of its corners on the upper face with four lugs101to which there are secured the lifting rods or cables11which connect the base1to the haulage cable10. The base1is further provided with means for anchoring to the bottom20in proximity of the structure30to be cut. The anchoring means comprise claws201which are swingable with respect to the ears301projecting out of the base1and connected to pairs of hydraulic jacks401, provided with opposed stems411.

To the base1, there is connected the plate2, to the lugs112of which there are hinged, at one of their ends, the two guides302, by means of the flaps322projecting out of same. In proximity of the other end the guides302are instead connected through the flaps312to the articulated arm202,212, hinged on its turn to the lugs222of the plate2. The two ends of the branches202,212of the articulated arm which are connected between each other, are connected to the stem122of the jack102which by its other end is swingably connected to the lug112. The two guides302are united between each other by means of the traverse bar402.

Onto the guides302there are arranged two tubular members3which are longitudinally slidable thanks to the slides403integral to said members3, mounted in overhanging manner in the same slides403. At the end of said tubular members3directed towards the end of the guides302directly hinged to the plate2there are arranged the means for boring the bottom, comprising the boring or cutting heads303while at the opposite end of said tubular members3there are arranged two ducts203for discharging the material removed during the boring of the bottom. On each one of the tubular members3there is obtained, facing the other tubular member, a longitudinal slot103; between the two slots, of which only one is visible in the Figure, there is arranged the cutting tool, comprising the diamond cable4, movable within the said tubular members3by means of devices which will be after illustrated and described.

InFIG. 2the apparatus according to the invention has been placed on the bottom20next to the structure to be cut30, and the claws201, under the action of the jacks401, have been driven into the bottom itself, thus anchoring the base1and setting the apparatus ready for subsequent operations.

InFIG. 3the jacks102have been actuated so as to lift the articulated arms202,212which act on the guides302. Consequently the said guides302and also the tubular members3arranged onto same, have been suitably inclined with respect to the plane of the bottom; the said inclination is selected according to the ideal cutting plane which has been established for the cutting of the structure30, and which depends substantially from the characteristic features of the structure itself, such as position, section and material, from the characteristic features of the bottom and from the depth at which the cut must be effected below the level of the bottom itself. As soon as the desired inclination has been reached, the tubular members are displaced by means of the slides403along the guides302, and the boring heads303penetrate into the bottom20thus forming two perforations21. Said perforations are obtained parallely to the ideal cutting direction of the cutting tool4, and in such a manner that the structure is comprised between the said perforations. The material removed by the boring heads303, is suitably conveyed along the tubular members3and discharged onto the bottom thanks to the discharge ducts203.

InFIG. 4the perforation phase of the bottom has been completed, and the boring heads have reached and passed beyond the level at which the cut must be effected. At this point, the cutting means are actuated and the cutting tool4, that is the diamond cable, is caused to interfere firstly with the portion of bottom comprised between the two perforations21and after with the structure30, thus originating the cut31. The cutting means can thereafter be retracted up to the position shown inFIG. 3and the boring heads are extracted out of the respective perforations21, by causing the slides403to slide in opposite direction on the guides302; the portion of the submerged structure30which is located above the cut31, can be conveniently grasped and removed.

From what above said it appears evident that the method according to the present invention obviates several inconveniences which were encountered up to the present date at the moment in which there should be effected the cutting of submerged structures below the level of the bottom on which said structures are positioned. In fact, instead of the ample excavations around the structure which are necessary up to the present date in order to reach the desired depth, the cutting means are guided inside perforations which remove a minimum portion of the bottom, thus remarkably limiting the environmental impact of the operation, and increasing remarkably the simplicity and rapidity of the action.

InFIG. 5there is shown a second embodiment of the apparatus according to the invention; identical reference numerals designate identical parts. In this case the base1is mounted on sliding shoes5, provided with propellers105transversely oriented with respect to said sliding shoes and with propellers205axially oriented. The propellers105,205are mounted on respective supports115,215.

As it can be noted from the Figure, the boring head303at the end of the tubular member3is keyed onto the shaft323of a speed reducer313; its side wall which has a substantially conical development, according to this embodiment is formed by the blades343which are angularly equispaced. In the portion of the tubular member immediately downstream of said speed reducer313, the wall503subdivides the interior of said member3into the duct523for the discharge of the material removed by the boring head303and into the portion513inside which there are arranged the cutting means, which communicates with the exterior through the slot103in which there slides the cutting tool4. At the opposite end of the tubular member3, on the discharge duct523there is positioned an aspirator213, which discharges the debris into the discharge duct203.

The tubular member3is mounted overhanging on the slide403which moves along the guide302thanks to the speed reducer423integral with said slide and which carries on its shaft423a pinion433which co-operates with the rack332arranged on the side wall of the guide302.

FIG. 6is a section view along line VI—VI ofFIG. 5; at the interior of the tubular member there are arranged the cutting means comprising the cable4preferably of the diamond type, which is arranged on the pulley104, keyed onto the shaft114which is inserted in the carriage204. One end of the shaft114is provided with a bevel pinion124which engages the bevel pinion414of the speed reducer404arranged on the carriage204. The carriage204is provided with two sliding shoes214which co-operate with the guides304connected with the wall503which divides the tubular member3into the portion513and into the duct523; to the said wall503there is also applied the pipe333which carries the feeding fluid to the speed reducer313of the boring head302(seeFIG. 5). On the carriage204there is overhangingly connected the speed reducer504on the shaft524of which there is keyed a pinion514which engages the rack533arranged on the wall503. The speed reducers404and504are fed through the pipes424and534carried by the supporting member603movable along the guide613formed on the inner wall of the tubular member3.

The operation of the apparatus adapted to carry out the method according to the invention will appear evident from the following. The positioning of the apparatus on the bottom30can be controlled from the surface, as shown inFIG. 1, by means of the haulage cable10, or the apparatus can be positioned with respect to the structure to be cut by using means placed directly on the apparatus itself, as in the case of the propellers105,205shown in the embodiment ofFIG. 5. In both cases, after the positioning and the anchorage of the apparatus, the guides302are oriented with respect to the structure to be cut thanks to the jacks102which act onto the articulated arms202,212so as to position them on the ideal plane of cutting of the said structure.

Subsequently the speed reducers413are actuated to permit the forward movement of the slides403which carry the tubular members3, at the ends of which there are mounted the boring heads303which are driven in rotation by the speed reducers313. As the boring heads penetrate into the bottom30, the produced debris are conveyed into the ducts523provided at the interior of the tubular members3and under the action of the aspirators213are expelled through the discharge ducts203.

When the boring heads have reached the suitable depth with respect to the structure to be cut, the perforation is interrupted, and there is actuated the speed reducer504which is mounted on the carriage204which carries the diamond cable4, together with the speed reducer which drives the pulley104on which there is arranged the cable4itself. The cutting means move forward along the tubular members3, until they meet first the bottom20and then the structure30, into which there is made the cut31. At this point also the cutting means can be stopped and subsequently retracted by abandoning, if the case, the cable; afterwards the tubular members3will be retracted and there will be recovered the structure30thus cut.

InFIG. 7there is shown another embodiment of the apparatus according to the present invention; identical reference numerals designate identical parts. In the illustrated case the already described plate2is connected to the support7which forms together with the movable plane407and the levers107and207, which are hinged to both, an articulated parallelogram. To the lever207there is connected in a swingable manner the stem of the jack307which by its other end is hinged to the plane407. The said plane407is hinged by one end to the lug408of the anchoring frame8, while at the other end it is coupled to the stem318of the jack308connected to the said anchoring frame8. The anchoring frame8is provided with two anchoring clamps108, intended to seize the structure30. The apparatus is connected to the haulage cable40by means of the lifting rods or cables41which are connected to the slots508and507.

InFIG. 8the apparatus according to the embodiment ofFIG. 7is shown at the end of the cutting phase of the structure, with the tubular members inside the perforations21and the cutting tool4which has traversed the structure30itself. As it can be appreciated, in this case the anchoring of the apparatus is performed directly on the structure30itself, and the positioning of the boring means and of the cutting means is obtained thanks to the three, different possibilities of adjustment consented by the articulated parallelogram of the support7, by the jack308of the movable plane407and by the articulated arm202,212which, in co-operation with the jack102, operates on the other hand in a manner analogous to what previously described with reference to the other embodiments of the apparatus according to the present invention.

InFIG. 9there is shown, in section along line IX—IX ofFIG. 8, a clamping jaw108. Onto the two fixed arms108there are mounted, swingable on the pins138, a pair of rocking levers118, each of which is provided at one end with a blocking element128, which is also swingable with respect to the lever118, and at its other end hinged to the stem158of the jack148, on its turn swingably connected to the anchoring frame8. Between the two jacks148connected to the arms there is arranged a jack208on the stem of which there is positioned a blocking element228which consents the seizing of the structure30and the centring with respect to same.

The advantages deriving from this embodiment are evident; in the first place it is not affected during its operation by any influence connected to the features of the bottom and to its regularity, since the only part which comes Into contact with the bottom is only the one which penetrates the bottom itself, that is the tubular members3, the boring heads303and the cutting tool4. In the second place the structure30, after the cutting, remains connected to the support of the apparatus, that is to its anchoring means represented by the clamping jaws108, and it can be therefore better controlled during its removal.

InFIG. 10there is shown another embodiment of the apparatus according to the present invention; the plate2is mounted onto a base409connected to the upright of a stand frame9which comprises a diagonal beam209and a traverse beam309; at the end of the diagonal beam209connected to the traverse beam309as well as at the end of the upright109connected to the traverse beam there is provided a foot219. All the feet219are provided with perforation means509and with expansion inserts609. The perforating means509generate the bores22inside which the foot219and the end of the upright are inserted, and the expansion inserts609perform the locking in place. As it can be seen inFIG. 11, the stand frame9comprises two uprights109, two diagonal beams209and two traverse beams309, facing each other and connected by the transverse bars119and319.

The support of the apparatus of the invention, conceived in this manner, considerably reduces the space required for the positioning of the apparatus in proximity of the structure to be cut, and therefore can be useful in those cases in which the bottom in its proximity presents irregularities, or a flat bottom portion of limited extension. Moreover the anchoring system appears to be particularly quick and efficacious, capable of adapting itself to extremely difficult ambient situations.

The method according to the present invention and the apparatus for carrying out said method consent therefore to reach remarkable results from the point of view of the rapidity of operation, of the effectiveness and of the environmental impact which is extremely limited.