Operation system and operation method for underwater jet trenching and cable laying

An operation system for underwater jet trenching and cable laying, comprising:

• a main body (1);
• a underwater walking device (2) provided at a lower end of the main body (1);
• a jetting soil-breaking device (3) comprising two jetting arms (34), the two jetting arms (34) being located at a front end of the main body (1) and are each provided with a front nozzle (3411) for spraying a jet to trench on seabed;
• and
• a jetting suction device (4) arranged at a rear end of the main body (1) and comprising a suction pipeline (42) and a second jetting pipe (43), the suction pipeline (42) is provided with a discharge port (422) and a suction port (423), and the suction port (423) is configured to be towards a bottom of a trench, and a position of the discharge port (422) is higher than a position of the suction port (423) and the discharge port (422) is transversely arranged relative to the suction port (423), and the suction pipeline (42) is configured to suck sediment in the trench through the suction port (423) before a cable settles to the bottom of the trench, and to discharge the sediment to outside of the trench through the discharge port (423);
• wherein
• the second jetting pipe (43) is located at a rear side of the suction pipeline (42), and is provided with a jetting port (432), a jetting direction of jetting port (432) is horizontally arranged in a direction away from the suction pipeline (42), and the second jetting pipe (43) is configured to spray a horizontal jet through the jetting port (432) to scour an inner side wall and the bottom of the trench along the length direction of the trench after the sediment in the trench is sucked by the suction pipeline (42), so as to maintain a shape of the trench when the cable settles to the bottom of the trench.