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Prediction of Dewatering-Induced Ground Settlements Along the LNWI Pipelines
Interceptor sewers, with diameters generally greater than 1.5 meters (5 feet), traverse long distances from their terminating sewage treatment plants as well as cross varied geologic materials and numerous physical features. Routing of portions of pipelines often positions their alignments in lowlands, flood plains which typically contain unconsolidated alluvial deposits, and adjacent to watercourses to minimize impacts on existing improvements. Invert grades can be deep when compared to other utility grades and at times pipelines must be located within local groundwater aquifers. Pipeline dewatering involving deep wells and wide excavations can induce settlement of soft and loose subsurface soils which results in potential surface settlement and distress to existing improvements within the radius of influence of dewatering drawdown. This paper presents the methodologies used for predicting the surface settlement for portions of the Lower Northwest Interceptor (LNWI) project to be constructed in West Sacramento, California. The LNWI project consists of five sections of large diameter (1.4 to 3 meters) interceptor pipes (comprised of four force main segments and one gravity sewer segment), fourteen tunneled crossings, and two pump stations. The total length of the LNWI project is approximately 31 kilometers (19 miles). The LNWI crosses numerous major streets, highways, railroad embankments and a Barge Canal. A Standard Penetration, Dilatometer and Cone Penetration Test exploration program, used to obtain constrained moduli, consolidation characteristics and soil types, permitted an assessment of potential settlements. Modeled drawdown profiles in three dimensions allowed to estimate the affected soil volumes and associated loading stresses due to dewatering. Predicted magnitudes of settlement along and laterally out from the excavation alignments are also presented.
Prediction of Dewatering-Induced Ground Settlements Along the LNWI Pipelines
Interceptor sewers, with diameters generally greater than 1.5 meters (5 feet), traverse long distances from their terminating sewage treatment plants as well as cross varied geologic materials and numerous physical features. Routing of portions of pipelines often positions their alignments in lowlands, flood plains which typically contain unconsolidated alluvial deposits, and adjacent to watercourses to minimize impacts on existing improvements. Invert grades can be deep when compared to other utility grades and at times pipelines must be located within local groundwater aquifers. Pipeline dewatering involving deep wells and wide excavations can induce settlement of soft and loose subsurface soils which results in potential surface settlement and distress to existing improvements within the radius of influence of dewatering drawdown. This paper presents the methodologies used for predicting the surface settlement for portions of the Lower Northwest Interceptor (LNWI) project to be constructed in West Sacramento, California. The LNWI project consists of five sections of large diameter (1.4 to 3 meters) interceptor pipes (comprised of four force main segments and one gravity sewer segment), fourteen tunneled crossings, and two pump stations. The total length of the LNWI project is approximately 31 kilometers (19 miles). The LNWI crosses numerous major streets, highways, railroad embankments and a Barge Canal. A Standard Penetration, Dilatometer and Cone Penetration Test exploration program, used to obtain constrained moduli, consolidation characteristics and soil types, permitted an assessment of potential settlements. Modeled drawdown profiles in three dimensions allowed to estimate the affected soil volumes and associated loading stresses due to dewatering. Predicted magnitudes of settlement along and laterally out from the excavation alignments are also presented.
Prediction of Dewatering-Induced Ground Settlements Along the LNWI Pipelines
Pirabarooban, S. (author) / España, C. (author) / Trumbull, C. D. (author) / Finney, A. (author)
Pipeline Division Specialty Conference 2005 ; 2005 ; Houston, Texas, United States
Pipelines 2005 ; 1071-1078
2005-08-19
Conference paper
Electronic Resource
English
Research , Maintenance , Pipe materials , Inspection , Intercepting sewers , Drilling , Installation , Predictions , Design , Settlement , Rehabilitation , Optimization , Dewatering , Pipelines , Tunneling
Prediction of Dewatering-Induced Ground Settlements along the LNWI Pipelines
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