Offshore Cable Burial: How deep is deep enough?

海上风能(OSW)对英国的经济和能源安全至关重要。它也是一个巨大的投资领域，例如，截至2021年底，已承诺140亿GB用于新的OSW地点-这是英国第四大建设项目。除此之外，英国目前的2030年OSW装机容量目标将需要480亿GB的投资，并为2.7万人提供直接就业。尽管OSW部门日益成熟，但已安装基础设施的某些部分仍然存在问题。主要来说，与海底电缆相关的问题目前占所有保险索赔成本的75%，故障通常需要100天以上的时间才能纠正。海底电缆将海上风力涡轮机产生的电力输送到陆上输电系统。这会导致风电场运营商的供应中断和收入损失，从长远来看，这可能会导致回收期延长，并减少其可再生能源投资组合中的其他投资。在浅水水域，必须保护这些电缆不受锚和渔具的伤害，主要保护方法是将电缆埋在海床以下。电缆埋深是经济成本(埋深需要更长时间，需要更大的船只，可能需要更复杂的作业)和电缆因锚/渔具穿透海床而损坏的风险之间的折衷。在这种情况下，锚-索相互作用目前占电力电缆故障的85%。计划中的海上风电在英国各地的快速扩张--装机容量在未来30年内增加7.5倍--将需要在世界上一些最繁忙的航运/渔业水域安装新的电缆，这些新电缆必须安装在适当的深度。然而，行业目前缺乏适当的科学工具来确定不同土壤条件下的锚杆穿透深度。相反，他们使用简单的查询表，基于对海底土壤的非常广泛的描述性分类，基本上将巨大的真实土壤条件分为两类-软的或硬的。这种方法在一些土壤中被证明是高度保守的，导致了不必要的深埋(和昂贵的)埋葬。然而，在其他情况下，这显然是非保守的，因为锚-索相互作用主导了缆索故障。这项建议将正面解决缺乏健全的锚杆渗透模型的问题，并通过物理测试和计算模型开发一个工具包，以评估不同土壤条件下的锚杆渗透。该锚杆穿透预测工具将基于布线沿线通常可用的现场勘测数据，并避免使用过于简单的查找表。它的发展将由一个工业项目指导小组指导，该小组由妇女地位办公室部门的主要各方组成。至关重要的是，这一创新的锚渗透模型将使用包含实际现场调查数据的地理数据库进行校准和验证。模型的性能将根据已证实的、可证明的地面条件进行评估，因此不会依赖于假设的地面条件，而假设的地面条件可能被当前的电缆埋设评估技术过度简化(例如，描述性的单一类型土壤不随埋深变化，而不是更复杂的多层土壤类型)。除了锚渗透预测工具外，还将创建一些空间测绘层(特定于英国大陆架)，从该工具应用到整个英国海底的已知地面条件。这些测绘层将公开提供，预计将在项目概念阶段提供给高层空间规划决策。总而言之，该项目将提供一个行业可用的锚渗透模型，使OSW部门能够回答关键的电缆埋设问题--多深是足够深？

Offshore Wind (OSW) is critical for the UK's economy and energy security. It is also an area of huge investment, for example £14bn has been committed up to the end of 2021 for new OSW sites - the 4th largest construction programme in the UK. Beyond this, the UK's current 2030 OSW installed capacity targets will require £48bn of investment and provide direct employment for 27,000 people.Despite the growing maturity of the OSW sector, certain elements of the installed infrastructure remain problematic. Principally, problems associated with subsea power cables that transport and distribute the electricity generated offshore in wind turbine generators to the onshore transmission system currently account for 75% of the cost of all insurance claims and faults typically take 100+ days to rectify. This leads to breaks in supply and loss of revenue for the wind farm operator which in the long term can lead to longer payback periods and reduced investment elsewhere in their renewables portfolio. In shallow waters these cables must be protected from anchors and fishing gear and the primary protection method is to bury the cable below the seabed. The cable burial depth is a compromise between economic cost of burial (going deeper takes longer, requires larger ships and may require more complex operations) and risk to the cable being damaged by anchors/fishing gear penetrating the seabed. Within this context, anchor-cable interactions currently account for 85% of power cable failures. The planned rapid expansion of offshore wind around the UK - installed capacity increasing 7.5 times over the next 30 years - will require new cable installations within some of the busiest shipping/fishing waters in the world and it is essential that these new cables are installed at the appropriate depth. However, the industry currently lacks appropriate scientific tools to determine anchor penetration depths in different soil conditions. Instead they use simple look-up tables based on very broad descriptive classifications of the soils on the seabed that basically split the huge spectrum of real soil conditions into two categories - soft or hard. This approach has been shown to be highly conservative in some soils leading to unnecessarily deep (and costly) burial. However, it is clearly non-conservative in other conditions as anchor-cable interactions dominate cable failures. This proposal will tackle the lack of sound anchor penetration models head on and, through physical testing and computational modelling, develop a toolkit to assess anchor penetration in different soil conditions. This anchor penetration prediction tool will be based on the site investigation data typically available along cabling routes and avoid the use of oversimplistic look-up tables. Its development will be guided by an industrial project steering group made up of key parties from the OSW sector. Crucially, this innovative anchor penetration model will be calibrated and validated using a geodatabase comprising actual site investigation data. Model performance will be assessed against proven, demonstrable ground conditions and therefore will not rely on hypothetical ground conditions which can be oversimplified using current cable burial assessment techniques (e.g. descriptive single-type soils that do not change with burial depths, as opposed to more complex, multi-layered soil types). In addition to the anchor penetration predictive tool, a number of spatial mapping layers (specific to the UK Continental Shelf) will be created, derived from the tool application to known ground conditions across the UK seafloor. These mapping layers will be made openly available, and are anticipated to feed into high-level spatial planning decisions at project concept stage.In summary, this project will provide an industry usable anchor penetration model allowing the OSW sector to answer the key cable burial question - how deep is deep enough?