Construction of South Tunnel project in Hartford, Connecticut, USA requires a launch shaft, starter and tail tunnels and a large diameter circular pump station. These structures will require excavation through 25 m of overburden soils and 25 m of bedrock. Overburden soils include approximately 10 m thick layer of soft and compressible varved clay. Lowering of groundwater above or below varved clay as a result of South Tunnel construction will cause a reduction of groundwater level and increase in the effective stress in varved clay. Given adequate time, this increase in effective stress will result in consolidation settlement. There are existing facilities in the vicinity of the launch shaft area where ground movement should be minimized. This paper discusses the method of analyses and presents the results of estimated settlements and mitigation measures.
展开▼
