Modelling deep mixing on the passive side of a deep excavation in soft soil - A pilot study to evaluate the effect of lime-cement columns on the passive side of excavation in soft soil
Typ
Examensarbete för masterexamen
Program
Publicerad
2020
Författare
RAHMAN, S M SHAZEEBUR
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Lime-cement (LC) columns was recently adapted to stabilize the passive side of a excavation in soft soil in Sweden within the railway project Västlänken. Inclinometers were installed on the construction site to measure the wall displacements as well as sensors to measure the forces in the struts. To further deepen the under-standing of the behavior of a LC stabilized excavation a numerical model is created using Creep-SCLAY1S model and Hardening Soil model to represent the clay and the lime-cement composite respectively. The numerical model prediction and the monitored performance of the excavation are compared and analyzed. Different stiffness parameters of the lime-cement soil block are considered to investigate the effect of stiffness changes on the model. With the adjusted stiffness parameters, the maximum outward wall displacement is approximately 40 mm after the stage LC installation and the highest inward movement is around 30 mm after dismantling the bottom strut compared to the field measurement of around 45 mm and 35 mm for the respective stages. The largest estimated forces in the top and bottom struts are 2400 kN and 2800 kN respectively where as the observed forces are approximately 2250 kN and 1700 kN. The Hardening Soil model represents the LC stabilized material in a sufficient way as the wall displacements and strut forces during the excavation is well estimated by the created model. The displacements of the retaining wall are not sensitive to LC columns stiffness during the initial construction stages but are increasingly sensitive as the excavation proceeds below level -7. The maximum bottom heave and top clay layer displacements estimated by the model are 170 mm and 115 mm upward respectively. Overall, numerical models can be a design tool for LC stabilization in the passive side of excavation in soft soil.
Beskrivning
Ämne/nyckelord
Västlänken project , Hardening Soil model , deep excavation , soft soil , lime-cement column , CREEP-SCLAY1S