Ground Improvement and Construction Challenges of Massive Fine-Grained Fill Embankments to Support Settlement Sensitive Structures-Paper

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The paper describes the geotechnical design and construction of large warehouse platforms within a 124-hectare logistics complex in Costa Rica. The site’s steep, varied topography required fills up to 8 m high, while economic feasibility depended on reusing on-site volcanic clays and silts. These fine-grained materials overlay soft, compressible soils and can be sensitive to moisture changes, creating risks of swelling, settlement, and damage to settlement-sensitive warehouse floors and equipment.<br /><br />Investigations included borings, SPTs, CPTs, laboratory testing, and geophysical surveys. The improvement strategy combined removal of topsoil and unsuitable soils, carefully controlled placement and compaction of suitable on-site fill, and imported granular fill near the surface to limit moisture-related volume changes. Fill quality was monitored through frequent density and moisture testing, with CPTs and plate load tests used to confirm ground performance.<br /><br />Preloading was the primary method for reducing settlement under building floors. Surcharge heights, generally 2 m across warehouse areas and locally up to 3 m near heavily loaded footings, were selected to approximate or exceed future stresses. Settlement plates tracked ground movement during filling and surcharge, informing design refinements. At column locations, localized over-excavation and replacement with low-strength grout improved bearing conditions; footing designs also accounted for stress dissipation with depth.<br /><br />Settlement during filling and preloading reached approximately 5–9 cm, completing much of the expected consolidation before construction. Post-fill testing showed adequate stiffness and bearing performance, and monitoring after warehouse-shell construction recorded negligible column movement, within survey precision. The case study demonstrates that massive fills using fine-grained on-site soils can support high-performance structures when underpinned by thorough site characterization, tailored ground improvement, rigorous construction quality assurance, and ongoing settlement monitoring.

Keywords

geotechnical design

warehouse platforms

ground improvement

preloading

settlement monitoring

volcanic clays

compaction control

soft compressible soils

CPT testing

logistics complex