Soil mixing and dewatering with artificial recharge for the construction of a mutifunctional complex-PPT Presentation

PPT Presentation

Pdf Summary

A multifunctional complex in Dendermonde, Belgium, required deep excavation in layered Quaternary soils, with no naturally impermeable base to contain groundwater. High groundwater levels behind the soil-mix retaining walls were evident from leakage through anchor holes, creating risks of water inflow and settlement.<br /><br />The dewatering system used 22 deep wells with submersible pumps inside the excavation and 22 artificial-recharge wells outside partial retaining walls. This created a largely closed water cycle, reducing discharge to the wastewater system and helping limit settlement risks. For every 100 m³/h extracted, approximately 80 m³/h was reinjected into the ground. The system preserved more than 720,000 m³ of water.<br /><br />Recharge wells are vulnerable to clogging, so design and operation focused on recharge-water quality, well development and regeneration, and minimizing aeration and changes in water temperature and pressure. The pipe system was sealed and degassed, and minimum operating pressures were maintained; high flow velocities that could create local under-pressure were avoided. Because some clogging is inevitable, well regeneration was included in the plan, alongside ongoing monitoring.<br /><br />The design process included geotechnical investigation, identification of nearby underground structures, numerical modelling and calibration, preliminary dewatering and recharge tests, and monitoring during progressive dewatering. Modelling considered the effects of clogging, the depth of partial retaining walls, and how artificial recharge could increase extraction rates. The project demonstrates how carefully designed artificial recharge can support excavation dewatering while conserving groundwater and reducing environmental and geotechnical impacts.

Keywords

multifunctional complex

Dendermonde

Belgium

deep excavation

artificial recharge

dewatering system

groundwater management

soil-mix retaining walls

quaternary soils

settlement risk