(1) During the sinking of an open caisson, there shall be no high-voltage power poles, underground pipelines, fixed machinery and equipment, or permanent structures within the surrounding affected area; otherwise, safety measures shall be taken.
(2) The construction height of the open caisson should not be so great as to raise its center of gravity too high above the ground; it is advisable not to exceed the length of the short side or the diameter of the caisson. Generally, it should not exceed 12 m. When an increase in height is required under special circumstances, reliable calculation data must be available and necessary technical measures must be taken.
(3) When withdrawing the bearing timbers, a dedicated person shall be assigned to give unified direction, and the work shall be carried out zone by zone in the specified sequence. During the withdrawal of the bearing timbers and the sinking, personnel are strictly prohibited from passing beneath the cutting edge, bottom beams, and partition walls.
(4) If the internal and external scaffolding of the open caisson cannot sink together with the caisson, it shall be separated from the caisson formwork and reinforcement. Facilities such as the gin pole frame and ladders shall not be fixed to the shaft wall, so as to prevent accidents caused by their being pulled down when the caisson suddenly sinks.
(5) Protective railings shall be installed around the top of the open caisson. Facilities such as water pumps and hydraulic machinery pipelines inside the shaft must be firmly erected to prevent falling and injuring people.
(6) The air receiver of the air compressor shall be equipped with a safety valve; the gas transmission pipelines shall be numbered; and a dedicated person shall be responsible for the gas supply control. When divers are working, filters shall be provided, and the air intake shall be located where clean air can be obtained.
(7) Before the open caisson is sunk, the tie-rod bolts and round nails on the shaft wall shall be cut off. Especially during sinking without dewatering, all obstacles and protruding rebars in the shaft shall be completely removed to prevent the diver's diving suit from being cut.
(8) When the open caisson has a large area and is sunk without dewatering, passage openings for divers shall be provided in the partition walls inside the shaft. A floating operating platform dedicated for divers shall be erected inside the shaft.
(9) The height of the waterproof enclosing wall of a floating open caisson above the water surface shall under no circumstances be less than 1 m.
(10) When a grab bucket is used for soil excavation, personnel and equipment in the shaft opening shall be evacuated in advance; if they are not evacuated, effective safety measures shall be taken for proper protection.
(11) When manual excavation and mechanical transport are adopted, the soil bucket may be lifted only after it is fully loaded, the workers down the shaft have moved to safety, and a signal has been given.
(12) When hydraulic machinery is adopted, communication shall be established between the working face inside the shaft and the pump station. The water gun and the mud suction machine of the hydraulic machinery shall be test-run, and all connections shall be tight without water leakage.
(13) When the open caisson is sunk in mucky clay or silty clay, the working platform inside the shaft shall be a movable platform and shall be strictly prohibited from being fixed to the shaft wall, partition walls, and bottom beams. In the event of sudden sinking of the caisson, the platform shall be able to rise with the soil surging in the shaft.
(14) The rules for the compression and decompression of divers and the prevention and treatment of related occupational diseases shall be carried out in accordance with the relevant regulations.
(15) When forced sinking is carried out by pumping water from inside the shaft, personnel above the shaft shall leave the open caisson; if they cannot leave, safety measures shall be taken.
(16) If the open caisson is converted from sinking without dewatering to sinking with dewatering, observation shall be carried out after pumping, and only after the caisson is confirmed to be stable may operations down the shaft be permitted.
(17) When the sleeve-well and thixotropic mud method is used for construction, protective facilities shall be installed around the sleeve well.
(18) When loading is used to assist the sinking of the open caisson, the loading platform shall be calculated, and other operations shall be stopped within the loading or unloading range.
(19) When underwater concrete is used for sealing the bottom of the open caisson, the working platform shall be firmly erected, and railings shall be provided around the tremie pipe. Railings shall be provided around the platform. In addition to the weight of personnel and machinery, the platform load shall also take into account the suspended weight of the hopper and tremie pipe filled with concrete in the event of blockage.