3D Numerical Modelling of Pile Group Responses to Excavation-Induced Stress Release in Clay
Jat, Rashid Ali 16MESTR05 Supervisor - Dr. Mukhtiar Ali Soomro
3D Numerical Modelling of Pile Group Responses to Excavation-Induced Stress Release in Clay - Nawabshah: QUEST, 2020. - 44p.
ABSTRACT
It is well recognisted that superstructure load is transformed to surrounding soil through pi led foundation . Consequently, the high stress regime (stress bulb) is generated surrounding of the pile. On the other hand, the excavation in the ground
inevitably results in the ground movement due to induced-stress release. To cope wit h transportation problems in congested cities in the world like Hong Kong, Shanghai, London etc, underground transportation systems (involving tunnels for metros, excavations of metro stations and basement to facilitate inhabitants in the buildings for parking) have been developed. These excavations arc sometimes inevitable to be constructed adjacent to existing pi led foundations. This condition leads to a big challenge for a civil engineer to assess and protect the integrity of pi led foundation. Since many previous studies mainly focus on the effects of excavation on single piles, settlement and load transfer mechanism of a pile group subjected to excavation-induced stress release arc not well investigated and understood. To address these two issues, three-dimensional coupled-consolidation numerical analysis by using a hypoplastic model, which takes small-strain stiffness into account, is conducted. A non-linear pile group settlement induced . This may be attributed to reduction of shaft resistance due to excavation induced stress release, the pile had to settle substantially to further mobilize end-bearing. Compared to the Sp of the pile group, induced settlement of the single pile is larger with similar settlement characteristics. Due to the additional settlement of the pile group, factor of safety for the pile group can be regarded as. decreasing from 3.0 to l .4, based on a displacement-based failure load criterion. Owing to non-uniform stress release, pi le group tilted towards the excavation with value of 0.14%. Due to excavation-induced stress release and dragload, head load of rear piles away from the excavation was reduced and transferred to rear piles.This load transfer can increase the axial force in front piles by 94%.
R/IMS-20
3D Numerical Modelling of Pile Group Responses to Excavation-Induced Stress Release in Clay - Nawabshah: QUEST, 2020. - 44p.
ABSTRACT
It is well recognisted that superstructure load is transformed to surrounding soil through pi led foundation . Consequently, the high stress regime (stress bulb) is generated surrounding of the pile. On the other hand, the excavation in the ground
inevitably results in the ground movement due to induced-stress release. To cope wit h transportation problems in congested cities in the world like Hong Kong, Shanghai, London etc, underground transportation systems (involving tunnels for metros, excavations of metro stations and basement to facilitate inhabitants in the buildings for parking) have been developed. These excavations arc sometimes inevitable to be constructed adjacent to existing pi led foundations. This condition leads to a big challenge for a civil engineer to assess and protect the integrity of pi led foundation. Since many previous studies mainly focus on the effects of excavation on single piles, settlement and load transfer mechanism of a pile group subjected to excavation-induced stress release arc not well investigated and understood. To address these two issues, three-dimensional coupled-consolidation numerical analysis by using a hypoplastic model, which takes small-strain stiffness into account, is conducted. A non-linear pile group settlement induced . This may be attributed to reduction of shaft resistance due to excavation induced stress release, the pile had to settle substantially to further mobilize end-bearing. Compared to the Sp of the pile group, induced settlement of the single pile is larger with similar settlement characteristics. Due to the additional settlement of the pile group, factor of safety for the pile group can be regarded as. decreasing from 3.0 to l .4, based on a displacement-based failure load criterion. Owing to non-uniform stress release, pi le group tilted towards the excavation with value of 0.14%. Due to excavation-induced stress release and dragload, head load of rear piles away from the excavation was reduced and transferred to rear piles.This load transfer can increase the axial force in front piles by 94%.
R/IMS-20