EXCAVATION APPARATUS AND OPERATION THEREOF

摘要

A pipeline trenching plough is towed along the seabed by a tow wire (20) connected to a ship or tractor. The course of the plough is changed or maintained by oppositely-acting forces imposed on the wire (20) and on the body (10) of the plough by a hydraulic ram (24). The offset angle between the wire (20) and the lengthwise direction (30) of the plough is monitored by a potentiometer (33, 35). The wire (20) is connected to the plough at a real hitch point (22) vertically above the center of resistance (23) of soil forces on the ploughshare (12) and landside (14). Under normal equilibrium conditions the forces from the ram are zero. The forces required to change the course are small and independent of the offset angle. Ram force can counteract a side-sloping seabed. In modifications, the wire (20) is connected to a virtual hitch point formed by an adjustable linkage; or by a carriage adjustable along a transverse beam.