The collapse of an urban street revealed the catastrophic failure of a 19th-century brick sewer. The investigation determined that a massive fatberg, an accumulation of grease and waste, altered the hydraulic flow regime. This modification generated backwater zones where aggressive chemical compounds attacked the original lime mortar, accelerating its erosion until causing the structural rupture of the conduit.
Failure reconstruction using LiDAR SLAM and CFD 🛠️
A mobile LiDAR scanner with SLAM technology was used, processed in GeoSLAM Hub, to obtain a millimeter-scale point cloud of the collapsed sewer interior. In CloudCompare, the eroded surfaces were segmented and the material loss in the joint mortar was quantified. With this geometric data, the model was imported into Autodesk CFD to simulate the pre-collapse flow. The simulation revealed that the fatberg acted as a dam, reducing the effective cross-section and increasing fluid velocity, which concentrated the chemical attack of biogenic hydrogen sulfide on the lower joints, where the mortar lost up to 40% of its original thickness.
Lessons for material fatigue simulation in infrastructure 🧱
This case demonstrates that material fatigue depends not only on cyclic mechanical loads but also on localized chemical degradation induced by flow changes. The original mortar, designed for a stable hydraulic regime, failed when exposed to a concentrated corrosive environment. Modern alternatives, such as mortars with basalt aggregates and epoxy resins, offer greater corrosion resistance, but their application must be validated with CFD models that predict critical zones for aggressive agent accumulation.
Which finite element simulation methodology do you recommend for modeling the combined effect of hydraulic pressure from a fatberg and chemical degradation of mortar in a historic brick sewer?
(PS: Material fatigue is like yours after 10 hours of simulation.)