In much the same manner as Increment 1, Increment 2 needs a survey element.
In practice, it would also use much the same equipment and personnel.
The exception to this is the understanding of seabed conditions at the proposed location.
There is a common misconception that large offshore jack-up platforms simply turn up for work and jack down, this is not the case. Leg push through is a dangerous condition where one of the legs pushes through an unexpectedly soft layer of the seabed and in some cases the rig can be put at risk of collapse. Because jack up platforms are likely to feature in Increment 2 solutions this is a concern.
This potential need for seabed soil survey also poses a particularly difficult challenge for two reasons.
It is likely that potential operational locations for Increment 2 do not fall within the ‘friendly nation’ category and so unlikely to allow an overt survey using jack-up platforms or survey vessels of their nearshore areas. This would also provide an alert that a pre-surveyed is an area of interest and counter-productive to mission success.
And so the first difficult challenge for Increment 2 that the seabed survey has to be conducted covertly, underwater.
Although given time the number of pre-surveyed locations could be a sizeable database the time available for conducting the pre-build survey may be compressed by contingent operations. The second challenge is that the survey must be conducted and data analysed quickly. In speeds favour is that the actual physical area to be surveyed is likely to be quite small.
Put the two together and the problems are amplified.
Conducting a rapid and covert subsea soil survey is not a trivial task.
The survey task would actually start in the UK by analysing existing data and data that may be obtained from other sources. This initial desktop survey would be used to support additional capture and analysis planning.
Follow up hydrographic surveys, metals/debris detection and sub bottom profiling could be carried out using vessels of opportunity or under the cover of routine hydrographic surveys carried out by NATO survey vessels. Standoff AUV’s and even handheld devices could also be used.
But this only gets us so far, there is no substitute for physical sampling.
Existing special-forces have quite capable covert beach survey capabilities (including manual core sampling) and when combined with stand-off systems deployed from conventional survey vessels the majority of the survey task can be covered. However, the aspect of the survey requirement that is not covered by existing capabilities is sea bed load bearing capacity.
This requires penetrometers and possibly, core sampling.
At its simplest form, cone penetrometer testing involves inserting a rod into the seabed and measuring tip resistance and sleeve friction. The data collected is then analysed using specialist software. The traditional method of conducting a near shore soil load bearing survey is to use a jackup platform and a cone penetrometer test using an integrated drill derrick or a standalone system deployed over the side or through a moon pool. The penetrometer is inserted through a hollow casing that provides lateral stability and buckling resistance. In very soft soils an additional device called a piezecone penetrometer may also be used.
Core samples may be taken to verify predicted data taken from penetrometers.
These are established techniques, but hardly covert.
There are however, alternatives.
For deeper water surveys, typically used for offshore energy installations and requiring significant load bearing, underwater penetrometers are available from a number of manufacturers including AP Van Den Berg in the Netherlands and Datem in the UK. Both have developed compact coiled rod units that can be lowered to the seabed and remotely operated from a ship.[tabs] [tab title=”Underwater CPT”]
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Although mostly used for deeper water they have also seen some use when mounted on a tracked underwater ROV for intertidal applications.[tabs] [tab title=”ROV 1″]
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If they can be mounted on a tracked ROV or lowered from a surface vessel, they can be deployed from submarines or simply ‘driven in’ from a safe offshore distance.
Any equipment will need to fit within the Project Chalfont dry shelters that can be fitted to the Astute class submarines, and other similar shelters or torpedo/missile launch tubes used by allies, this may require some design engineering but the systems are available and well understood, the task would be repackaging not starting from scratch.
A number of parameters will need to be analysed; Soil density, soil strength, friction angle, consolidation and permeability for example. This should also include analysis of the strata to the desired penetration.
Finally, a scour potential survey should be carried out, analysing wave and current in addition to soil conditions.
Whilst sampling would in most cases be conducted covertly, analysis can be carried out away from the target site aboard one of the survey vessels supporting the operation, or in the UK via reach back.
The output from a survey would be a decision on site suitability.
If Increment 2 were taken forward it would also be desirable to pre-survey potential locations in ‘peacetime’. This could be a standing and regular task shared between allies, although of course, there is some element of risk if those locations on not in the ‘friendly nation category’!
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