Vertical Load Transfer Behavior of Composite Foundation and Its Responses to Adjacent Excavation: Centrifuge Model Test

Abstract

In urban construction, more and more foundation pit excavations are adjacent to existing buildings with composite foundations. Therefore, it is necessary to study the interaction between foundation piles and supporting structures. In this article, a centrifuge model test has been carried out to study the vertical load transfer behavior of composite foundation with rigid piles and its responses to adjacent excavation. The test model was designed based on a real excavation project adjacent to an existing composite foundation. The sand pluviation method was used to build the foundation model. An in-flight excavation method and a loading device for multilevel uniform surface load were used in the test. Finally, the variations of induced axial force, pile skin friction, and pile-soil stress ratio along with the depth were investigated. Some useful conclusions can be drawn as follows: (1) the negative skin friction in the upper part of piles, induced by the overlaying load, increases first and then decreases along with the depth; (2) pile-soil stress ratio decreases along with the depth under initial loads, while it increases first and then decreases when the load is larger; (3) pile-soil stress ratio always increases with loads in the same depth, indicating that mobilized skin friction of piles is continuously developed; and (4) more significant changes of the axial force, skin friction, and pile-soil stress ratio of composite foundation piles are observed in the shallow soil and for the later excavation stage. Therefore, the deformation of the foundation pit should be strictly controlled during the later excavation stages.

Numerical study on stress paths in grounds reinforced with long and short CFG piles during adjacent rigid retaining wall movement

“…In this regard, recent years have witnessed that the synergistic mechanism influences the vertical load-bearing characteristics throughout the process of neighbouring excavation work. [18][19][20] The physical model test results of Li et al [21] on the load distribution of rigid pile composite foundation revealed the same characteristics under the condition of soil displacement from retaining wall rotation about the base.…”

Method of settlement calculation for underlying layer of soft soil composite foundation based on load transfer mechanism

“…The settlement of composite foundation includes the settlement of reinforced area (RA) and the settlement of underlying layer (UL). At present, most of the settlement studies of composite foundation focus on the RA and less on the UL [1][2][3]. The traditional methods for calculating the settlement of the UL include equivalent solid method, stress diffusion method, etc.…”

Observed Performance and FEM-Based Parametric Analysis of a Top-Down Deep Excavation in Soil-Rock Composite Stratum

“…In the past several decades, extensive studies have been conducted to investigate the performance of deep excavations in terms of excavation-induced deformation and internal force characteristics of retaining walls and bracing structures [9][10][11], ground movements [12][13][14], and response of preexisting structures that are adjacent to the excavations [15][16][17]. These studies are based mainly on numerical simulations [18,19], empirical or semiempirical methods [20,21], analytical solutions [22,23], in situ monitoring data analysis [24,25], centrifuge or scaled model testing [26,27], and machine learning [28,29]. Among the commonly adopted methods, numerical simulations usually predict better results for excavation-induced wall displacements than for ground movements and can consider the effects of excavation stages and nonlinearity of soil behavior [30,31].…”