As-built diagram and JI for works on development of underwater trenches by HITACHI excavator from pontoon

Scope of Application

The checklist provides the organization and technology of performance of work for development of an underwater trench in group IY soil, the HITACHI excavator (with the extended handle) from a pontoon from otvozky soil in a coastal dump, when building underwater transition through river. Mustache of the BovanenkovoUhta main gas pipeline of ∅1420 mm.

The works covered by the map include:

installation of the excavator in the transition line;

development of an underwater trench;

movement of pontoon by excavator.

During development of Job Instruction the following initial positions are adopted:

underwater trench development:

water excitation is not more than 2 points;

transportation of soil by barges to coastal dumps;

maximum trench development depth - up to 14 m;

trench width along the bottom - 16 m;

trench slopes - 1.252.3;

excavator bucket capacity - 1.4 m3;

working shift duration - 8 hours;

works are performed in summer time in one shift.

Organization and procedure of works execution

Before the underwater trench is developed by the excavator from the pontoon, it is necessary to:

provide the area of the approved work with detailed documentation (working drawings and WTP);

Accept, in accordance with the established procedure, the target of transition from the general contractor (customer) with door signs and repositories;

obtain permission to carry out the work;

install a water metering post;

Perform a diving survey of the bottom of the reservoir by the width of the trench opening plus 5 m upstream and downstream to identify possible obstacles;

prepare the pontoon for operation, make sure that there are no damages of the housing and leaks;

To place and prepare in the work area the necessary devices, equipment and means for the safe conduct of work (fire extinguishers, boat, cats, lifeline, etc.);

install the excavator on the pontoon; to prevent movement of the excavator on the pontoon during operation, limiters are welded to the pontoon along the entire outer perimeter of the track support area;

The development of the underwater trench is carried out by a link consisting of 2 people and a HITACHI EX 330 excavator installed on pontoons equipped with circular piles.

Before starting work on the water metering station, the water level in the reservoir is determined.

The excavator on the pontoon is installed in the transition alignment, with the help of winches, the annular piles are lowered into the ground and hold the pontoon in place during the operation of the excavator. In this area, the excavator begins the development of an underwater trench, unloading the developed soil into shalands with subsequent transportation and unloading of soil to the coastal dump located downstream at a distance of at least 50 m. Moving from one side to the other in the process of operation, the excavator develops a trench of design section along the transition line.

After the development of the trench in this area to the design elevations, the rear piles are raised by winches and the excavator with a bucket repositions the pontoon to the next section of the developed trench, the pitch of the excavator is 4 m.

The orientation of the excavator during operation is continuously controlled by coastal shutter signs.

The signals supplied during the works shall be worked out in advance.