It is well recognised that the severity of pipeline external corrosion is highly related to the corrosivity of the surrounding soil environment. However, in practice, the explicit effects of the soil corrosivity variables on the spatial distribution of external corrosion defects are largely unknown. This paper presents a novel modelling and predicting approach for pipeline external corrosion defect count data in terms of spatial patterns using on a multivariate Poisson-lognormal (MVPLN) model. The MVPLN model can account for the over-dispersion and unobserved heterogeneity of the defect count data, as well as consider the stochastic correlation between corrosion defects with different spatial patterns. The developed model is applied to a pipeline inspection dataset consisting in-line inspection (ILI) data and corresponding soil corrosivity measurements. Its performance is validated by using cross-validation. A comparison study shows that the MVPLN model provides superior modelling results for the spatial distribution of external corrosion defects over the commonly used univariate count data models. In addition, the obtained model coefficients of the soil corrosivity measurements are discussed, and their estimated impacts on the spatial patterns of corrosion defects are verified qualitatively. The potential application to assess the corrosion severity of non-piggable pipeline segments is further demonstrated.

众所周知，管道外部腐蚀的严重程度与周围土壤环境的腐蚀性高度相关。然而，在实践中，土壤腐蚀性变量对外部腐蚀缺陷的空间分布的显式影响在很大程度上是未知的。本文使用多元Poisson-lognormal（MVPLN）模型，根据空间模式，提出了管道外部腐蚀缺陷计数数据的新颖建模和预测方法。MVPLN模型可以解释缺陷计数数据的过度分散和未观察到的异质性，并考虑具有不同空间模式的腐蚀缺陷之间的随机相关性。将开发的模型应用于管道检测数据集，其中包括在线检测（ILI）数据和相应的土壤腐蚀性测量值。通过使用交叉验证来验证其性能。一项比较研究表明，与常用的单变量计数数据模型相比，MVPLN模型为外部腐蚀缺陷的空间分布提供了出色的建模结果。此外，讨论了获得的土壤腐蚀性测量的模型系数，并定性验证了它们对腐蚀缺陷的空间格局的估计影响。进一步证明了评估不可固定管道段腐蚀严重程度的潜在应用。一项比较研究表明，与常用的单变量计数数据模型相比，MVPLN模型为外部腐蚀缺陷的空间分布提供了出色的建模结果。此外，讨论了获得的土壤腐蚀性测量的模型系数，并定性地验证了它们对腐蚀缺陷空间模式的估计影响。进一步证明了评估不可固定管道段腐蚀严重程度的潜在应用。一项比较研究表明，与常用的单变量计数数据模型相比，MVPLN模型为外部腐蚀缺陷的空间分布提供了出色的建模结果。此外，讨论了获得的土壤腐蚀性测量的模型系数，并定性地验证了它们对腐蚀缺陷空间模式的估计影响。进一步证明了评估不可固定管道段腐蚀严重程度的潜在应用。