San Francisco County Municipal Code § 10.3 Settlement Analysis

Settlement calculations should account for various stages and durations of construction (i.e., estimates of the time required for each stage of dewatering and construction should be made). Stages include, but are not limited to, placement of shoring, dewatering, excavation for construction of basement and foundation, termination of dewatering, and long-term recharge of groundwater table. In some cases, and depending on soil permeability, recharging of the groundwater table may not occur until sometime after completion of construction. This delay in groundwater recharge should be accounted for when evaluating the hydrostatic uplift pressure during and after termination of dewatering (i.e., accounting for full and immediate groundwater recharge after termination of dewatering may be unconservative). The geotechnical report should state the estimated long-term groundwater conditions at the site.

Short-term and long-term (consolidation) settlement analysis should be performed using appropriate models as approved by the geotechnical members of the EDRT.

Commentary: For shallow foundations, consolidation analysis may be conducted using computer programs that perform one-dimensional settlement analyses at several locations across the building footprint and within the zone of influence based on a three-dimensional stress distribution.

For deep foundations that terminate above bedrock, short-term and long-term (consolidation) settlement analysis should be performed using appropriate models capable of modeling deep foundations as single piles or pile groups, as reviewed by the geotechnical members of the EDRT.

Commentary: Finite-element or finite-difference computer programs, which are capable of modeling single piles or pile groups, should be used to calculate consolidation settlement of structures supported on deep foundations.