Section 3 Types of mooring and tethering arrangements

3.1.1 Mooring systems generally consist of one of the following arrangements:

1. Mooring lines and chains retaining the linkspan against a quayside or series of dolphins.

2. A system of mooring booms keeping the linkspan at a fixed distance from the quayside.

3.2.1 Tethering arrangements will generally consist of:

1. Two or more guidepiles attached to the linkspan by a yoke (or yokes) permitting vertical movement of the linkspan but restraining horizontal movement.

2. A single guidepile and yoke at one end of the linkspan allowing vertical tidal movement, and a bankseat arrangement allowing rotation but providing suitable translational restraint.

3.3.1 Other types of mooring or tethering arrangements will be considered.

3.3.2 Where the means of securing the installation is provided by frictional support from the sea bed, the pontoons are to have a factor of safety of at least 2,0 against sliding or bearing capacity failures under all loading conditions occurring at the operating location.

The available unit friction between pontoon and soil (or along any other potential failure surface, for example, between a fabric drainage mat and soil) may be required to be verified by tests. Attention is to be paid to the need to ensure good and complete contact between pontoon and soil, and to guard against possible scour from current and underbase erosion due to sub-surface erosion caused by water pressure under the base. In general, this type of securing is to be considered only for well protected locations, but each submission will be considered with respect to calculations and test data supplied by the designer.