Abstract
In order to calculate the bearing capacity and settlement deformation of composite pile foundations with long and short piles in collapsible loess areas, the theoretical approximate solution was used to obtain the location of the neutral point of single piles. Additionally, based on the equation to calculate the bearing capacity of multielement composite foundations, a method considering the negative frictional resistance was proposed for calculating the bearing capacity of composite pile foundations with long and short piles. Based on the shear displacement method and the principle of deformation control, an equation to calculate the displacement and deformation of a composite pile foundation was presented. A model test with different operating conditions, i.e., a single pile, four piles, and eight piles, was designed to verify the proposed calculation methods. The results show that the location of the neutral point has a significant influence on the single-pile negative frictional resistance, and the neutral point ratio of the calculation meets the value range of the practical project. When the load at the top of the pile is relatively small, the experimental curve is consistent with the theoretical calculation curve, whereas when the load is comparatively large, the theoretically calculated displacement increase at the top of the pile is greater than the measured one. Under the premise that the theoretical calculation is in good agreement with the results, the theoretical value is larger than the actual value. And it contributes to strengthening engineering safety.
Highlights
With superior force transmission performance, pile foundations have good applicability in improving the bearing capacity of foundations and controlling the settlement deformation of buildings [1]. e stress performance of largediameter cast-in-place concrete pile is good, which leads to more and more common application in pile foundation [2]
With deformation control as the design principle, a composite pile foundation with long and short piles [4, 5] was proposed as applicable in loess areas based on the analysis principle of settlement reducing piles. e design principle is that when there are two or more bearing layers in the foundation soil, all the long piles will be located in the deep bearing layer to control the settlement deformation of the buildings, whereas the short piles will be located in the Advances in Civil Engineering shallow bearing layers to provide the bearing capacity
Li et al [17] presented a semianalytical approach to predict the time-dependent bearing performance of an axially loaded jacked pile in saturated clay strata and provided an incremental algorithm and a corresponding computational code to assess the time-dependent load-settlement response of a jacked pile. ere currently are many studies on the bearing capacity of composite pile foundations with long and short piles, but few in-depth studies have been conducted on their applicability in collapsible loess areas, and almost no theoretical analysis can be found regarding the location of the neutral point and calculation of the reduction effect of the bearing capacity of negative frictional resistance
Summary
With superior force transmission performance, pile foundations have good applicability in improving the bearing capacity of foundations and controlling the settlement deformation of buildings [1]. e stress performance of largediameter cast-in-place concrete pile is good, which leads to more and more common application in pile foundation [2]. E location of the neutral point was determined through theoretical analysis, a method considering the negative frictional resistance was proposed to calculate the bearing capacity of the composite pile foundation, and the corresponding equation to calculate the displacement deformation was presented. Based on the principle of deformation control, Equation (11) was introduced to obtain a method that considers negative frictional resistance when calculating the settlement deformation of composite pile foundations in collapsible loess areas. Erefore, based on the method for calculating the bearing capacity of composite foundations with long and short piles in collapsible loess areas proposed in this study, the following equation was obtained: fspk P. erefore, with considering the pile-group negative frictional resistance, the method for calculating the settlement deformation of composite foundation with long and short piles in loess areas was established. Erefore, with considering the pile-group negative frictional resistance, the method for calculating the settlement deformation of composite foundation with long and short piles in loess areas was established. e theoretical method to calculate the settlement of composite foundations with long and short piles based on deformation control was thereby presented
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