Deformation properties of diaphragm wall due to deep foundation pit of subway station in Ningbo soft soil
According to the field measured data of a deep foundation pit of subway station of Ningbo rail transit, the paper studies the varieties of deformation rate and cumulative deformation along with excavation time, and estimates the proportion of deformation under different construction phases based on 450 monitoring data of 4 deep foundation pits. The result shows that the main deformation of diaphragm wall due to deep foundation pit of subway station in Ningbo soft soil happens in the third and the forth phases, and these two conditions should be the key point of hierarchical control.
Characteristics of ground surface settlement during excavation
The objective of this paper is to study the characteristics of ground surface settlement during excavation. Ten excavation cases in Taipei with good-quality construction and field observation data are selected to study the characteristics of excavation behavior. The location of maximum lateral wall deflection, magnitude of maximum lateral wall deflection, relationship of maximum lateral wall deflection and maximum ground surface settlement, location of maximum ground surface settlement, and apparent influence range are thus established based on the actual excavation cases. Finally, an empirical formula is proposed to predict the ground surface settlement profile at the center section of an excavation, where the behavior may be characterized by plane-strain conditions. Key words : excavation, surfac settlement, wall deflection, plane strain, empirical formula.
PREDICTION OF MOVEMENTS FOR BRACED CUTS IN CLAY
A simplified method is presented for the prediction of wall and soil movements for braced excavations in soft to medium clay deposits. The method is developed by combining the results of field data performance and finite element analyses. A careful review of 130 published and unpublished case histories was carried out to select well-documented projects with similar support systems and free of unusual construction effects. The finite element analyses were directed toward the evaluation of effects of variation of soil shear strength, soil stiffness, support stiffness and system geometry. Both the field data and the finite element results show that a strong correlation exists between system movements and the factor of safety against basal heave. Based on the established behavior trends, nondimensional plots are developed for predicting maximum magnitudes and distributions of wall deflections and ground settlements as a function of the factor of safety against basal heave and the other important parameters of the soil and structural system.