Settlement of large underground rainwater tanks under time dependant storage load

As water resources become more expensive, the concept of sustainability is becoming increasingly entrenched in civil design and construction. Current practice influences the usage of rainwater tanks to capture surface runoff and redistribute for non-potable usage to reduce the demand on mains supply. Land developers employ this practice to promote sustainability and provide large rainwater tanks to service entire developments. The implementation of large subsurface water storage systems subjects the surrounding soil mass to stress variations. Short term elastic and time dependant consolidation settlement of the soil may result from the loading conditions imposed upon by the water storage system. Consequently, the settlement behaviour of the soil must be considered to ensure the intended function of the subsurface water storage system and the safety of the utilities above the system. Through a demonstrated case study, this paper considers typical geological and hydrological conditions for settlement assessment of a subsurface water storage system. The storage load variation of the system due to variable rainfall patterns, catchment characteristics and system capacity are taken into consideration for this study. The overall analysis provides predictions to the long term settlement of the rainwater storage system.