Beneficial use of Pressuremeter Tests for accurate the Slab foundation design of a Biogas Plant in Germany

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4. Beneficial use of Pressuremeter Tests for accurate the Slab foundation design of a Biogas Plant in Germany

This paper presents a case study of a biogas plant in Germany. Based on the original soils report, the ground was considered marginal based on DPM and later CPT. With the estimated soil parameters, a shallow foundation design for the tanks was not feasible. The settlement prediction for the high loaded tanks was in the intolerable range of 40 to 50 cm. Thus, the typical solution was an expensive thick reinforced slab supported by deep piles.

To optimize the foundation design, the Menard pressuremeter (PMT) was carried out with the aim of using a direct design procedure for predicting the bearing capacity and settlements of the tanks. Based on the PMT results a shallow foundation on Controlled Modulus Columns (CMC), a rigid inclusion network (RI) with load transfer platform, could be designed to reduce the settlement on an acceptable limit. The additional benefits of the shallow foundation approach were an optimised slab thickness of 25 cm and lower costs for the foundation works. Shallow foundations provide adequate support for steel tanks, and they are cost effective compared with conventional deep foundations using piles. However, to realise that kind of optimization, appropriate and reliable soil parameters for the design are needed. The RI design in this case was done with load transfer curves to model the rigid inclusion behaviour, as suggested by the Frank and Zhao (1982). The input parameters for this model are determined from Menard pressuremeter tests. The prediction of settlements considering the RI treatment shows good agreement with measured settlements obtained during hydrostatic (full scale) load tests after completion of the works.

8th International Symposium on Pressuremeters (ISP2025)

Applications in Foundation Engineering