Application of geodetic measurements to verify the effectiveness of biogas plant foundation

This study presents the application of high-precision geodetic levelling to verify foundation performance of a biogas digester in Slovakia. The foundation consists of 49 driven concrete piles (4 m length), 250 mm compacted gravel layer, and 500 mm reinforced concrete slab supporting an 18-meter diameter digester. Settlement monitoring using a Leica LS15 digital level (±0.20 mm precision) was conducted across five loading steps (0–100% capacity) over 26 days. Four observation points were anchored to the foundation slab, with four reference points on adjacent stable structures. At full operational capacity (55 kPa surface pressure plus 7.8 kN/m perimeter loading), measured settlements ranged from 4.8 to 5.6 mm, averaging 4.5 mm. PLAXIS 3D finite element analysis using Mohr-Coulomb and Hardening Soil models predicted 7.8 mm and 9.9 mm respectively, meaning actual settlements were 58% and 45% of predictions. Maximum differential settlement was 0.8 mm (s/D = 0.00025), well below the 0.002 critical threshold. Settlement stabilized within 6 hours per loading increment, with creep under 0.15 mm over 9 days, confirming elastic soil behaviour. The conservative predictions suggest beneficial pile driving effects on ground densification. Results validate the composite foundation system effectiveness and demonstrate optimization opportunities for future biogas infrastructure while maintaining safety margins.