Abstract
Negative skin friction (NSF) has been one of the important factors in the design of pile foundation; especially, the influence of water level on the pile negative skin friction should be paid attention. In this paper, a series of model tests were carried out to analyze the bearing characteristic of the pile group influenced by groundwater level. The pile axial force and negative skin friction, settlement, and soil pore pressure were investigated. The results showed that both the water level rising and lowering cycle could increase the axial force of the pile along the upper part of the pile, yet reducing it along the lower part of the pile; both the axial force and the negative skin friction of the pile presented a feature of time effect; the value of negative skin friction was positively correlated with that of the pile head load, and the neutral plane ranged from 0.57 L to 0.64 L as the water level changed; the soil featured settling in layers, and the change of pore water pressure was accordant with the water level changing regulation.
Highlights
Negative skin friction (NSF), regarded as an unfavorable load on the pile, develops where the settlement of the surrounding soil exceeds that of the pile, which may well induce force in the pile, resulting in ambiguous design in the pile bearing capacity and even some engineering failures like pile damage, uneven settlement of the structure, and foundation failure [1,2,3]
A series of model tests were conducted to study how the bearing characteristics of the pile group, especially the axial force and the negative skin friction, were influenced by groundwater level rising and lowering. e pore water pressure as well as settlement of pile and surrounding soil was investigated. e results are beneficial to properly understand how piles behave in varying water level, which might help provide some guidance for the pile design in reservoir areas, and will lay out groundwork for future research in more systematic and specific analysis of pile bearing characteristics under varying water level condition
Axial Force Distribution. e average axial force distribution of this 2 × 2 pile group was calculated based on the measured strain data
Summary
Negative skin friction (NSF), regarded as an unfavorable load on the pile, develops where the settlement of the surrounding soil exceeds that of the pile, which may well induce force in the pile, resulting in ambiguous design in the pile bearing capacity and even some engineering failures like pile damage, uneven settlement of the structure, and foundation failure [1,2,3]. A few studies can be found on how negative skin friction factored down the behavior of piles in lowering water level. Lee and Chen [15] performed centrifuge model tests to study the influence of lowering of groundwater level on pile negative skin friction. E research work on NSF caused by water level is still lacking in attention and systematic study, especially the factor that the rising and lowering cycle of water level, which is encountered commonly in engineering sites, remains blank in specific mechanisms and principles on how the variation of groundwater level affects pile foundation. A series of model tests were conducted to study how the bearing characteristics of the pile group, especially the axial force and the negative skin friction, were influenced by groundwater level rising and lowering. A series of model tests were conducted to study how the bearing characteristics of the pile group, especially the axial force and the negative skin friction, were influenced by groundwater level rising and lowering. e pore water pressure as well as settlement of pile and surrounding soil was investigated. e results are beneficial to properly understand how piles behave in varying water level, which might help provide some guidance for the pile design in reservoir areas, and will lay out groundwork for future research in more systematic and specific analysis of pile bearing characteristics under varying water level condition
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