Assessment of settlements caused by groundwater control

Abstract

Lowering of groundwater levels by pumping increases vertical effective stress in the soil around an excavation. The resulting ground settlements are normally small, but in certain circumstances may be large enough to cause damage to surrounding structures. This paper describes the mechanism of these settlements and presents a simple risk assessment methodology for initial identification of zones where buildings may be at varying degrees of risk of damage. These risk zones can help to determine the extent of preconstruction building condition surveys needed, or to assess the need for settlement mitigation or avoidance measures. Potential uncertainties in the assessments are discussed.

Vulnerability and Impact Assessment of Land Subsidence using Persistent Scatterers Interferometry (PSI) for Chennai, India.

“…The major trigger for this phenomenon is the excessive extraction of groundwater resulting in its exhaustion (Figueroa-Miranda et al, 2020). When the groundwater level is lowered due to its extraction from aquifers, it paves the way for an increment in the effective stress and consolidation of soil (Preene, 2000). This process is known as aquifer compaction, resulting in the downward displacement of land.…”

Dual‐Screened Vertical Circulation Wells for Groundwater Lowering in Unconfined Aquifers

“…However, massive withdrawal of groundwater from aquifers is not avoidable with the existing dewatering methods. Severe environmental and geotechnical problems, that is, soil consolidation, ground surface settlement, and contaminant migration, are the known consequences (Foster et al ; Preene ; Powers et al ; Roy and Robinson ). Furthermore, if the pumped water is of low quality, extra costs are induced to meet the environmental regulations for discharging (Powers et al ).…”

Test and numerical research on wall deflections induced by pre-excavation dewatering

“…If an excavation is performed below the groundwater level, dewatering is generally adopted to prevent the excavation from flooding [1]. In a congested urban environment, dewatering is typically performed inside the excavation to reduce the impact of dewatering on the adjacent structures and facilities [2,3].…”

“…As to excavations that require a drawdown exceeding 5-10 m (e.g., typical metro excavations), the deep well is often employed [4]. Deepwell dewatering for excavations typically includes two stages: (1) pre-excavation dewatering and (2) staged dewatering with the staged excavation and bracing. Stage 1 is often used to develop the well [3,4], check the completion quality of the well [4] and examine the impermeability of the retaining wall (or cut-off wall).…”