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As the most important feature of jacked open-ended concrete pipe piles, shear zone has fluence of crucial importance during installing and after penetration. This study conducted a field test in silt deposit to observe the physical phenomenon of shear zone after installation and investigated soil parameter differences from undisturbed soil through laboratory tests. Direct observation on shear zone reveals that the boundary between shear zone and in situ soil is evident. The average soil thickness in the shear zone falls between 6 and 30 mm, which are closely related to natural water content and void ratio in different layers. Laboratory tests on the shear zone show evident compaction during installation, and the soil parameters in the shear zone are sensitive to the jacking installation procedure. Some soil parameters decrease, whereas others increase because of excess pore water dissipating after installation. The extent of the shear zone is helpful in understanding interface friction on pretensioned high-strength concrete (PHC) piles in clay. [ABSTRACT FROM AUTHOR]