Abstract
Capped piles are efficient in settlement control and have been widely used in the reinforcement of soft soil foundations for high‐speed railways and highways. In this study, scenarios involving both capped piles and ordinary piles without caps are numerically studied using the finite element software (ABAQUS). The settlement characteristics of capped piles composite foundation considering the effects of both the pile spacing and the ratio of pile cap to pile diameter are achieved. Based on the numerical results, assuming that the capped pile and the soil under the cap jointly bear load and settle together, a settlement calculation model for capped piles composite foundation is established. By both replacing the compression modulus with the deformation modulus obtained from the field static load test and calculating the area replacement ratio, the formula for calculating the total settlement of the capped piles composite foundation is derived using the layer‐wise summation method. In addition, a real embankment engineering with capped piles composite foundation is adopted to validate the accuracy of this method; by comparing with other methods, the results show that this method is in better agreement with the field monitoring data. Therefore, the proposed method is recommended in the relevant engineering design.
Highlights
Capped pile is usually made up of a rigid pile body and a pile cap. e rigid pile body is mostly PHC or PTC in practice. e pile cap is usually a round or a square concrete slab, and the diameter or side length to pile diameter is 2∼4 [1]
(1) if the load acting on the soil between the piles has been determined, the settlement can be calculated as the deformation of the soil between the piles [27] (Es method); (2) if the load acting on the top of a pile has been determined, the settlement can be calculated as the deformation of the pile [28, 29] (Ep method); (3) if the capped piles and foundation soils have been considered to be a whole, a composite module method can be used [30, 31] (Ec method); and (4) if the pile cap and the pile body are regarded as a single pile foundation, the settlement can be calculated using a composite foundation with the settlement-reducing pile method [32, 33]
In the Advances in Civil Engineering process of settlement, the soil under the pile cap always shares a part of the load [34], and the stress ratio of pile to soil varies with the load level [35, 36]. us, it is difficult to calculate the settlement using Es or e compressive modulus (Ep) methods in practical project. e composite module method is accurate for flexible pile composite foundations [37] and whether it is suitable for rigid pile composite foundation needs to be verified
Summary
Capped pile is usually made up of a rigid pile body and a pile cap. e rigid pile body is mostly PHC or PTC in practice. e pile cap is usually a round or a square concrete slab, and the diameter or side length to pile diameter is 2∼4 [1]. The settlement calculation method does not provide any convenient options for capped piles composite foundations, especially rigid piles using PHC or PTC. The settlement characteristics and the influencing factors of the capped piles composite foundation were analyzed using finite element software (ABAQUS). Both the capped pile and the soil under the cap were treated as a composite pile within a reinforcement area. Taking a practical embankment reinforced by capped plies composite foundation as an example, the calculated settlement was compared with both that calculated by other methods and field monitoring data to validate this proposed method
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