Slide 12
As I’ve told you, the concrete collar is attached along the pipeline with 6 m span. It was combined by upper and lower parts of precast concrete collar.
The concrete is designed to 35 MPa of the compressive concrete strength and 2.55 ton/m3 of dry density.
To prohibit that the pipe is rotating when floating on the water surface, the bottom part of the collar designed to be heavier than the upper part. The blocks are attached on the pipes with 4 bolts which designed enough to combine each parts.
Bolt forces are controlled by means of measuring the compression of the rubber compensators on each bolt.
In order to secure that the block will not slide on the pipe during the submersion of the pipes, a sliding test was performed.
A minimum bolt force at the assembly of collars on the pipes should be more than 8 ton. But, based on 0.5 friction coefficient between rubber pad and HDPE pipe, considering more than 4 times safety factor for uncertainty during bolt tightening & sinking pipe and etc., a maximum bolt force at the assembly of blocks on the pipes is designed to be around 33.5 ton (335kN). As a result M33 size of bolt is used.

Slide 12

As I’ve told you, the concrete collar is attached along the pipeline with 6 m span. It is combined by the upper and lower parts of the precast concrete collar.
The concrete is designed to 35 MPa of the compressive concrete strength and 2.55 ton/m3 of dry density.
To prohibit that the pipe is rotating when floating on the water surface, the bottom part of the collar is designed to be heavier than the upper part. The blocks are attached on the pipes with 4 bolts which are designed enough to combine each parts.
Bolt forces are controlled by means of measuring the compression of the rubber compensators on each bolt.
In order to secure that the block will not slide on the pipe during the submersion of the pipes, a sliding test is performed.
A minimum bolt force at the assembly of collars on the pipes should be more than 8 ton. But, based on 0.5 friction coefficient between rubber pad and HDPE pipe, considering more than 4 times safety factor for uncertainty during bolt tightening & sinking pipe and etc., a maximum bolt force at the assembly of blocks on the pipes is designed to be around 33.5 ton (335kN). As a result M33 size of bolt is used.