Analysis of the Load Sharing Behaviour and Cushion Failure Mode for a Disconnected Piled Raft

Zhu, Xiaojun

doi:10.1155/2017/3856864

Cited by 18 publications

(4 citation statements)

References 15 publications

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“…Similarly, many numerical studies have examined the settlement and bearing behavior of these types of foundation systems [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. Other studies have investigated the load sharing behavior of piled rafts, which is considered an important component in designing the piled raft foundation system [31][32][33][34][35][36][37][38][39].…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of the Carrying Capacity of a Piled Raft Foundation in Soft Clayey Soils

et al. 2022

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Piled raft foundations are a common type of foundation for high-rise buildings. Unlike shallow foundations, deep foundations (piles) pass through weak or soft soil deposits and can reach stiff soil or bedrock to support the weight of the structure. In this paper, the performance of a medium embedment depth piled raft foundation in soft soil is presented. A numerical model was developed and a parametric study was conducted in order to simulate the case of such a foundation system and to investigate its performance in soft clay. This parametric study investigated the effect of the geometry of a piled raft foundation and the stiffness ratio between the pile material and clay on the performance of the foundation system in soft soil. Additionally, the failure mechanism of such a foundation system under load was examined. An analytical model was developed to predict the ultimate carrying capacity based on the observed failure mechanism. A semi-empirical model is proposed for determining the Improvement Factor (IF) of a given soil, pile, and geometric condition. Findings of the study indicate that the performance of piled raft foundations on soft soils is significantly affected by the piles’ spacing. As the ratio S/D increases, the ultimate carrying capacity of a piled raft foundation decreases. However, when this ratio exceeds 10 (S/D> 10), piles have little or no effect on the ultimate carrying capacity of this foundation system. A piled raft foundation system fails by bearing at the base of the piles and also by shear at the side of the pile group on hyperbolic plans. Doi: 10.28991/CEJ-2022-08-04-01 Full Text: PDF

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Section: Introductionmentioning

confidence: 99%

Numerical Analysis of the Carrying Capacity of a Piled Raft Foundation in Soft Clayey Soils

et al. 2022

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“…At present, literature is rich with information regarding pilesoil stress ratio, capability of cushion to evenly transmit upcoming vertical load to pile head and soil, relative pilesoil displacement and its associated negative skin friction (NSF) development on the upper 15 ~ 50% of the length of pile, bearing and settlement characteristics, and utilization of different kinds of pile types. Even though the NSF on the upper pile section is one of the common features in disconnected piled rafts (Jiang and Liu, 2018;Miao et al, 2018;Saeedi Azizkandi et al, 2019;Wu et al, 2016;Zhu, 2017), it is considered as unfavorably imposed action in traditional pile design. Nonetheless, equilibrium is achieved with necessary pile/soil relative movement for positive shaft friction (PSF) and/or sufficient pile settlement to mobilize tip resistance by the so called "natural self-balancing process" (Tan and Fellenius, 2016).…”

Section: Introductionmentioning

confidence: 99%

Experimental study on load sharing characteristics of long-short CFG pile composite foundation adjacent to rigid retaining wall rotating about its base

Uge

Guo

2021

JER is an international, peer-reviewed journal that publishes f

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Practicing geoengineers and researchers generally consider the load sharing behavior in multi-type pile composite foundation as an important design aspect. On the other hand, due to urbanization, such foundation system in cities will inevitably appear next to supported excavation. This paper discusses the result from relatively large-scale indoor experiment conducted to investigate the load sharing behavior of loaded long-short CFG pile composite foundation behind a neighboring rigid retaining wall undergoing rotation around the bottom. It was found that with progression of wall movement, the hidden load from soil displacement was borne by the piles with marked reduction in soil load sharing. At the end of wall rotation, the percentage of long piles’ head load increment needed to arrive at a new static equilibrium was about 12.57~32.22% while the end bearing increased by more than 97%. The consequences on the short piles, however, were manifested with an increasing pile head (13.42%) and toe (28.9%) load for the pile far from the wall whereas the closest one experienced a certain increment up to 15×10-4rad wall rotation and finally the head load and end bearing decreased to 8.28% and 12.63%, respectively. The 3D numerical back analysis conducted using FE software ABAQUS yielded the pile – soil stress ratio lower than the value obtained from the experiment but provided great insight into pile settlement characteristics during wall rotation.

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“…Many researchers studied the performance of connected and disconnected piled rafts in sand using centrifugal model tests [8][9][10][11][12][13]. Cao et al [8] and Sawwaf [9] carried out extensive static load tests to study the behavior of connected and disconnected piled rafts under vertical and eccentric loads.…”

Section: Introductionmentioning

confidence: 99%

“…Fioravante and Giretti [10], Fioravante [11], and Rasouli et al [12] studied the mechanical and settlement-related characteristics of connected and disconnected piled rafts through a series of centrifugal model tests. Based on the transfer mechanism of load in the case of disconnected pile (DP) rafts, a simplified failure mode involving a cushion and the corresponding theoretical analysis were proposed by Zhu [13]. Moreover, Liu et al [14] and Zhang et al [15] highlighted the importance of the cushion layer in adjusting the ratio of load sharing of the pile to that of the soil, based on field static load tests.…”

Section: Introductionmentioning

confidence: 99%

3D Numerical Analysis of Synergetic Interaction between High-Rise Building Basement and CFG Piles Foundation

et al. 2018

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A strong bearing capacity and the satisfaction of strict settlement requirements are necessary for high-rise buildings. A single-raft foundation cannot meet certain settlement requirements, in which case CFG (cement/fly ash/gravel, an emerging and sustainable construction material) piles can be used in the foundation to set up a cushion between the top of the pile and the raft slab, where the piles act as settlement reducers. The rafts of disconnected piles (DPs) exhibit complex synergetic interactions involving the raft, cushion, pile, and soil under the load of the superstructure. Multiple piles in particular lead to an increase in the number of degrees of freedom of the problem, resulting in difficulty in solving it. However, when the number of piles is very large and the structure is complex-for example, many buildings are placed on the same raft with basement structures-even if the embedded pile element is used during numerical calculations, either the method remains prone to non-convergence or the time needed for numerical calculations is too long. It is, thus, difficult to satisfy the requirement of an efficient scheme of evaluation in practice. To solve this problem, a method that uses a simulation of the integral equivalent of the CFG pile reinforcement zone is proposed in this paper. In the CFG pile reinforcement zone, the effect of the pile is reflected in the enhancement of parameters of the soil in the strengthened zone, and the reinforcement zone (including the soil and the pile) is regarded as an anisotropic elastoplastic material. As the structure of the pile is no longer needed in the model, its elimination significantly reduces the complexity of the model and improves its calculation efficiency. An example of a numerical calculation is provided to verify the viability and accuracy of the integral equivalent simulation method in comparison with the embedded pile element simulation method. Finally, the proposed method is applied to the three-dimensional numerical analysis of a scheme for the treatment of foundations of high-and low-rise buildings with basements, and its effectiveness is further verified through comparison with theoretical results.

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Analysis of the Load Sharing Behaviour and Cushion Failure Mode for a Disconnected Piled Raft

Cited by 18 publications

References 15 publications

Numerical Analysis of the Carrying Capacity of a Piled Raft Foundation in Soft Clayey Soils

Numerical Analysis of the Carrying Capacity of a Piled Raft Foundation in Soft Clayey Soils

Experimental study on load sharing characteristics of long-short CFG pile composite foundation adjacent to rigid retaining wall rotating about its base

3D Numerical Analysis of Synergetic Interaction between High-Rise Building Basement and CFG Piles Foundation

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