New advances in jet-assisted plowing for the undersea cable construction industry

Abstract

Cable burial by plowing, using large sled-type cable plows towed by large powerful cable ships is the standard and most widely used commercial method of protecting submarine telephone cables from fishing activity, large ship anchors and other ocean hazards. With the world's transoceanic cable systems now rapidly expanding into a global undersea network for the new millennium-and transoceanic cables connected to regional systems, which are then connected to domestic systems-there is a market trend towards an increased percentage of short-haul and non-repeatered systems. Many of these cable segments are less than 300 kilometers in length, will be deployed in shallow water (less than 1500 meters) and will require a more cost-effective burial approach. Hence, even though the brute force passive trenching method has become established as relatively reliable, there is a growing need for a more versatile, efficient and economical cable plowing system. Jet-assisted plows are similar to passive plowing tools and have demonstrated their ability to achieve adequate burial depth at reduced tow tension and increased forward speed. These plows utilize nozzles that introduce water at the soil interface to assist the trenching tool, reducing the stresses due to localized changes in soil conditions and possibly reducing pore water effect in cohesionless sands. Caldwell Cable Ventures, Inc. (a General Dynamics Company) has been applying this technology for more than 20 years, burying power and telecommunications cables in riverbeds, lakes and marshes to depths of up to 14 meters. More recently, General Dynamics-ATS (GD-ATS) and Tyco Submarine Systems, Ltd. (TSSL) have developed new high performance cable plows based on a novel Swept Flow Jetter (SFJ) approach. Additionally, The GD-ATS plow has an on-board cable engine to provide both cable tension and slack management, and a single combination tow/umbilical cable to reduce the number of cable winches and overall number of cables in the water column. The TSSL plow has a novel, more responsive rudder type steering arrangement. These new features have been successfully tested, providing a new level of cable plow performance and an economical burial alternative for the undersea cable construction industry.