Abstract:
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.

Description:
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; and   introduction 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. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages and characteristic features of the present invention will appear evident from the following detailed description of some preferred embodiments of same, made as non-limiting example with reference to the annexed sheets of drawings, in which: 
       FIG. 1  is a perspective view of a first embodiment of the apparatus for carrying out the method according to the invention, during its positioning in proximity of a submerged structure to be cut; 
       FIGS. 2 to 4  show in succession the operative steps of the method according to the present invention; 
       FIG. 5  is a side elevation view with parts in section of a second embodiment of the apparatus according to the invention; 
       FIG. 6  is a transverse section view along line VI—VI of  FIG. 5 ; 
       FIG. 7  shows the positioning in proximity of the structure to be cut of a third embodiment of the apparatus according to the invention; 
       FIG. 8  shows the operation of the apparatus shown in  FIG. 7 ; 
       FIG. 9  is a section view along line IX—IX of  FIG. 8 ; 
       FIG. 10  shows the operation of a further embodiment of the apparatus according to the present invention; and 
       FIG. 11  is a perspective view of the means for supporting the apparatus according to the invention shown in  FIG. 10 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In  FIG. 1  there is shown the apparatus intended to perform the method according to the present invention. Reference numeral  1  designates 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 lugs  101  to which there are secured the lifting rods or cables  11  which connect the base  1  to the haulage cable  10 . The base  1  is further provided with means for anchoring to the bottom  20  in proximity of the structure  30  to be cut. The anchoring means comprise claws  201  which are swingable with respect to the ears  301  projecting out of the base  1  and connected to pairs of hydraulic jacks  401 , provided with opposed stems  411 . 
   To the base  1 , there is connected the plate  2 , to the lugs  112  of which there are hinged, at one of their ends, the two guides  302 , by means of the flaps  322  projecting out of same. In proximity of the other end the guides  302  are instead connected through the flaps  312  to the articulated arm  202 ,  212 , hinged on its turn to the lugs  222  of the plate  2 . The two ends of the branches  202 ,  212  of the articulated arm which are connected between each other, are connected to the stem  122  of the jack  102  which by its other end is swingably connected to the lug  112 . The two guides  302  are united between each other by means of the traverse bar  402 . 
   Onto the guides  302  there are arranged two tubular members  3  which are longitudinally slidable thanks to the slides  403  integral to said members  3 , mounted in overhanging manner in the same slides  403 . At the end of said tubular members  3  directed towards the end of the guides  302  directly hinged to the plate  2  there are arranged the means for boring the bottom, comprising the boring or cutting heads  303  while at the opposite end of said tubular members  3  there are arranged two ducts  203  for discharging the material removed during the boring of the bottom. On each one of the tubular members  3  there is obtained, facing the other tubular member, a longitudinal slot  103 ; between the two slots, of which only one is visible in the Figure, there is arranged the cutting tool, comprising the diamond cable  4 , movable within the said tubular members  3  by means of devices which will be after illustrated and described. 
   In  FIG. 2  the apparatus according to the invention has been placed on the bottom  20  next to the structure to be cut  30 , and the claws  201 , under the action of the jacks  401 , have been driven into the bottom itself, thus anchoring the base  1  and setting the apparatus ready for subsequent operations. 
   In  FIG. 3  the jacks  102  have been actuated so as to lift the articulated arms  202 ,  212  which act on the guides  302 . Consequently the said guides  302  and also the tubular members  3  arranged 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 structure  30 , 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 slides  403  along the guides  302 , and the boring heads  303  penetrate into the bottom  20  thus forming two perforations  21 . Said perforations are obtained parallely to the ideal cutting direction of the cutting tool  4 , and in such a manner that the structure is comprised between the said perforations. The material removed by the boring heads  303 , is suitably conveyed along the tubular members  3  and discharged onto the bottom thanks to the discharge ducts  203 . 
   In  FIG. 4  the 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 tool  4 , that is the diamond cable, is caused to interfere firstly with the portion of bottom comprised between the two perforations  21  and after with the structure  30 , thus originating the cut  31 . The cutting means can thereafter be retracted up to the position shown in  FIG. 3  and the boring heads are extracted out of the respective perforations  21 , by causing the slides  403  to slide in opposite direction on the guides  302 ; the portion of the submerged structure  30  which is located above the cut  31 , 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. 
   In  FIG. 5  there is shown a second embodiment of the apparatus according to the invention; identical reference numerals designate identical parts. In this case the base  1  is mounted on sliding shoes  5 , provided with propellers  105  transversely oriented with respect to said sliding shoes and with propellers  205  axially oriented. The propellers  105 ,  205  are mounted on respective supports  115 ,  215 . 
   As it can be noted from the Figure, the boring head  303  at the end of the tubular member  3  is keyed onto the shaft  323  of a speed reducer  313 ; its side wall which has a substantially conical development, according to this embodiment is formed by the blades  343  which are angularly equispaced. In the portion of the tubular member immediately downstream of said speed reducer  313 , the wall  503  subdivides the interior of said member  3  into the duct  523  for the discharge of the material removed by the boring head  303  and into the portion  513  inside which there are arranged the cutting means, which communicates with the exterior through the slot  103  in which there slides the cutting tool  4 . At the opposite end of the tubular member  3 , on the discharge duct  523  there is positioned an aspirator  213 , which discharges the debris into the discharge duct  203 . 
   The tubular member  3  is mounted overhanging on the slide  403  which moves along the guide  302  thanks to the speed reducer  423  integral with said slide and which carries on its shaft  423  a pinion  433  which co-operates with the rack  332  arranged on the side wall of the guide  302 . 
     FIG. 6  is a section view along line VI—VI of  FIG. 5 ; at the interior of the tubular member there are arranged the cutting means comprising the cable  4  preferably of the diamond type, which is arranged on the pulley  104 , keyed onto the shaft  114  which is inserted in the carriage  204 . One end of the shaft  114  is provided with a bevel pinion  124  which engages the bevel pinion  414  of the speed reducer  404  arranged on the carriage  204 . The carriage  204  is provided with two sliding shoes  214  which co-operate with the guides  304  connected with the wall  503  which divides the tubular member  3  into the portion  513  and into the duct  523 ; to the said wall  503  there is also applied the pipe  333  which carries the feeding fluid to the speed reducer  313  of the boring head  302  (see  FIG. 5 ). On the carriage  204  there is overhangingly connected the speed reducer  504  on the shaft  524  of which there is keyed a pinion  514  which engages the rack  533  arranged on the wall  503 . The speed reducers  404  and  504  are fed through the pipes  424  and  534  carried by the supporting member  603  movable along the guide  613  formed on the inner wall of the tubular member  3 . 
   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 bottom  30  can be controlled from the surface, as shown in  FIG. 1 , by means of the haulage cable  10 , 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 propellers  105 ,  205  shown in the embodiment of  FIG. 5 . In both cases, after the positioning and the anchorage of the apparatus, the guides  302  are oriented with respect to the structure to be cut thanks to the jacks  102  which act onto the articulated arms  202 ,  212  so as to position them on the ideal plane of cutting of the said structure. 
   Subsequently the speed reducers  413  are actuated to permit the forward movement of the slides  403  which carry the tubular members  3 , at the ends of which there are mounted the boring heads  303  which are driven in rotation by the speed reducers  313 . As the boring heads penetrate into the bottom  30 , the produced debris are conveyed into the ducts  523  provided at the interior of the tubular members  3  and under the action of the aspirators  213  are expelled through the discharge ducts  203 . 
   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 reducer  504  which is mounted on the carriage  204  which carries the diamond cable  4 , together with the speed reducer which drives the pulley  104  on which there is arranged the cable  4  itself. The cutting means move forward along the tubular members  3 , until they meet first the bottom  20  and then the structure  30 , into which there is made the cut  31 . At this point also the cutting means can be stopped and subsequently retracted by abandoning, if the case, the cable; afterwards the tubular members  3  will be retracted and there will be recovered the structure  30  thus cut. 
   In  FIG. 7  there 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 plate  2  is connected to the support  7  which forms together with the movable plane  407  and the levers  107  and  207 , which are hinged to both, an articulated parallelogram. To the lever  207  there is connected in a swingable manner the stem of the jack  307  which by its other end is hinged to the plane  407 . The said plane  407  is hinged by one end to the lug  408  of the anchoring frame  8 , while at the other end it is coupled to the stem  318  of the jack  308  connected to the said anchoring frame  8 . The anchoring frame  8  is provided with two anchoring clamps  108 , intended to seize the structure  30 . The apparatus is connected to the haulage cable  40  by means of the lifting rods or cables  41  which are connected to the slots  508  and  507 . 
   In  FIG. 8  the apparatus according to the embodiment of  FIG. 7  is shown at the end of the cutting phase of the structure, with the tubular members inside the perforations  21  and the cutting tool  4  which has traversed the structure  30  itself. As it can be appreciated, in this case the anchoring of the apparatus is performed directly on the structure  30  itself, 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 support  7 , by the jack  308  of the movable plane  407  and by the articulated arm  202 ,  212  which, in co-operation with the jack  102 , 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. 
   In  FIG. 9  there is shown, in section along line IX—IX of  FIG. 8 , a clamping jaw  108 . Onto the two fixed arms  108  there are mounted, swingable on the pins  138 , a pair of rocking levers  118 , each of which is provided at one end with a blocking element  128 , which is also swingable with respect to the lever  118 , and at its other end hinged to the stem  158  of the jack  148 , on its turn swingably connected to the anchoring frame  8 . Between the two jacks  148  connected to the arms there is arranged a jack  208  on the stem of which there is positioned a blocking element  228  which consents the seizing of the structure  30  and 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 members  3 , the boring heads  303  and the cutting tool  4 . In the second place the structure  30 , after the cutting, remains connected to the support of the apparatus, that is to its anchoring means represented by the clamping jaws  108 , and it can be therefore better controlled during its removal. 
   In  FIG. 10  there is shown another embodiment of the apparatus according to the present invention; the plate  2  is mounted onto a base  409  connected to the upright of a stand frame  9  which comprises a diagonal beam  209  and a traverse beam  309 ; at the end of the diagonal beam  209  connected to the traverse beam  309  as well as at the end of the upright  109  connected to the traverse beam there is provided a foot  219 . All the feet  219  are provided with perforation means  509  and with expansion inserts  609 . The perforating means  509  generate the bores  22  inside which the foot  219  and the end of the upright are inserted, and the expansion inserts  609  perform the locking in place. As it can be seen in  FIG. 11 , the stand frame  9  comprises two uprights  109 , two diagonal beams  209  and two traverse beams  309 , facing each other and connected by the transverse bars  119  and  319 . 
   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.