Re-Supporting a Subsiding Reservoir with Targeted Resin Injection

A concrete water reservoir, supported by a ring beam foundation and concrete floor slab, began exhibiting uneven settlement across its perimeter. Approximately 30% of the ring beam had subsided by up to 50 mm due to significant voiding beneath the foundation. Ongoing erosion and natural ground settlement had created cavities under sections of the structure, resulting in loss of ground contact and uneven bearing support. This differential movement posed a risk to the reservoir’s structural integrity and long-term serviceability. The council required a fast, non-invasive remediation method to re-establish uniform foundation support without excavation or prolonged interruption to reservoir operations.

The works involved incremental injection beneath the ring beam to depths of up to 2,500 mm below ground level (BGL), allowing the expanding structural resin to penetrate and densify multiple soil layers. This process reinstated contact between the ring beam, floor slab, and subgrade while compacting and stabilising the underlying soil matrix. The internal slab was similarly treated using controlled resin injection to restore uniform support and eliminate voiding beneath the floor area. All works were performed using small-diameter injection points, enabling precise control of lift and ground improvement while maintaining reservoir operation throughout. The process was completed without excavation, noise, or contamination risk, meeting the council’s operational and environmental requirements.

Post-treatment monitoring confirmed effective ground densification, stable load transfer, and improved foundation integrity.

The works were completed efficiently, safely, and without operational downtime, delivering a durable, non-disruptive, and cost-effective solution that safeguarded the reservoir’s long-term performance.