Behaviour of micropiles in collapsible loess under tension or compression load

Qian, Zeng-zhen; Lu, Xian-long; Yang, Wenzhi; Cui, Qiang

doi:10.12989/gae.2014.7.5.477

Cited by 14 publications

(7 citation statements)

References 17 publications

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“…Even though a large database containing more than 1000 tests was assembled from various geotechnical reports and research papers, most of the tests were excluded because either the tests were conducted on disturbed samples or due to the insufficiency of reported soil properties. Habibagahi and Taherian, Basma and Tuncer, and Qian et al reported results for 339 single oedometer tests conducted on undisturbed samples of different types of collapsible soils with sufficient initial soil properties. Therefore, those 339 tests are the only tests considered in the current analysis.…”

Section: Modelingmentioning

confidence: 99%

“…Furthermore, a nomograph was suggested by Reference to predict the collapse potential based on the pressure at wetting, coefficient of uniformity, dry unit weight, and the critical water content. Qian et al conducted a series of laboratory tests on nine groups, each composed of three undisturbed collapsible soil specimens to study the hydro‐collapsibility and characteristics of loess in Northwest China. Qian et al concluded that the collapse potential decreases with increasing initial density and moisture content.…”

Section: Introductionmentioning

confidence: 99%

“…Qian et al conducted a series of laboratory tests on nine groups, each composed of three undisturbed collapsible soil specimens to study the hydro‐collapsibility and characteristics of loess in Northwest China. Qian et al concluded that the collapse potential decreases with increasing initial density and moisture content.…”

Section: Introductionmentioning

confidence: 99%

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Modelling the behavior of inundated collapsible soils

Ashour

Abbas

Altahrany

et al. 2020

Engineering Reports

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The properties of collapsible soil exhibit a lot of sensitivity toward the increase of water content, especially when the soil is close to the dry state. The inundation of collapsible soils induces a considerable drop in the void ratio (e) (ie, collapse potential, Cp, increase), which in return affects the dry unit weight ( d ), friction angle ( ), and shear strength of the soil. The presented study employs large numbers of sandy and silty specimens of collapsible soils with different initial conditions (gathered from the literature) to develop a correlation that evaluates Cp of the soil (ie, settlement) due to inundation. The developed relationship accounts for the soil's initial properties such as the void ratio (e 0 ), degree of saturation (Sr), and pressure applied to the inundated specimens. The presented model reflects the significant influence of Sr on Cp of inundated soil which considerably decreases by the increase of Sr. The determined properties of inundated collapsed soil, such as e and , are employed to construct the post-inundation stress-strain curve (ie, mobilized shear strength) of the soil based on the concepts of the conventional triaxial test. Comparisons between predicted and measured stress-strain curves of inundated collapsible soils are presented for validation. K E Y W O R D Scollapse potential, collapsible soil, constitutive model, stress-strain curve INTRODUCTIONCollapsible soils or metastable soils are unsaturated soils that undergo a significant volume reduction upon saturation with or without additional load. Generally, collapsible soils maintain an open "honeycombed" structure that could have negative pore water pressure and cementing agents that result in considerable shear strength. As a result of wetting, effective stresses are reduced due to the dissipation of the negative pore water pressure. Furthermore, the water dissolves or softens the bonds between the particles, causing a reduction in shear strength, nonetheless a denser particle packing.Collapsible soils may exist in natural deposits as well as in man-made fills and have been under investigation for many years in a broad literature. El Howayek et al 1 investigated the susceptibility of man-made fills to undergo collapse by conducting experimental investigations on two loess soil types that were compacted to a wide range of values of relative compaction (RC). El Howayek et al 1 observed that even specimens compacted to approximately 90% RC on the dry side of the optimum moisture content experienced large wetting-induced strains. In general, El Howayek et al 1 concluded that the collapse potential increases with decreasing compaction water content, RC, and degree of saturation.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

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Section: Modelingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Modelling the behavior of inundated collapsible soils

Ashour

Abbas

Altahrany

et al. 2020

Engineering Reports

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“…Loess is the dominant soil in Northwest China, accounting for 72.4% of the total loess area in China. In addition, China introduced the conception of the "New Silk Road Economic Belt" in 2013, and most of the soil in this area is loess, which brings great opportunity and challenge to the construction of pile foundation in loess area [16][17][18][19][20][21]. When cast-in-place bored piles are used in loess area, the steel casing is usually used to stabilize the borehole wall or solve the slurry leakage problem of huge caves.…”

Section: Introductionmentioning

confidence: 99%

Effect of Steel Casing on Vertical Bearing Characteristics of Steel Tube-Reinforced Concrete Piles in Loess Area

Feng

Dong

et al. 2019

Applied Sciences

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This study aims at investigating the effect of steel casing on vertical bearing characteristics of steel tube-reinforced concrete piles in loess area by centrifugal model test. Five piles were selected, one of them was a conventional reinforced concrete pile which was 35 cm in length and 2.5 cm in diameter as a contrast pile, and the length of steel casing for the remaining four steel tube-reinforced concrete piles was 8 cm, 12 cm, 16 cm, and 20 cm respectively. The results show that the axial force, unit skin friction, tip resistance, and shaft resistance of steel tube-reinforced concrete piles with different steel casing lengths were different from conventional reinforced concrete pile. Additionally, the ultimate bearing capacity of steel tube-reinforced concrete piles was compared with a conventional reinforced concrete pile. Moreover, advantages of steel casing in pile foundation engineering were summarized. The results of this study can provide reference for vertical bearing characteristics of steel tube-reinforced concrete piles in loess area.

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“…Loess has strong structural characteristics. e construction of cast-in-place piles in the loess strata will inevitably destroy the structure of loess, which will affect the mechanical properties of loess and pile-soil relationship [18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

A Full‐Scale Field Study on Bearing Characteristics of Cast‐in‐Place Piles with Different Hole‐Forming Methods in Loess Area

Zhou

Yang

Fan

2019

Advances in Civil Engineering

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This paper presents the results from a full-scale field study on the 3 different types of cast-in-place piles: rotary drilling piles (RDPs), manual digging piles (MDPs), and impact drilling piles (IDPs), for a bridge construction project of Wuqi–Dingbian Expressway, in Shaanxi. The results indicate that under the similar conditions, MDP exhibits the largest bearing capacity (11000 kN) in the loess area, followed by RDP (9000 kN) and IDP (8000 kN). And all tested values exceed the estimated value (7797.9 KN), indicating that the calculation formula of bearing capacity recommended by the Chinese standard is safe and conservative. During the load transfer process, the axial force attenuation rate of the pile body increases with pile side resistance. The average attenuation rate of MDP is the largest (24.2%), followed by RDP (19.72%) and IDP (16.69%). The bearing characteristics of these test piles are mainly pile side resistance, but the manual digging method created the least amount of disturbance to the soil around the pile, and due to its hole wall being rough, this enhances the pile-soil interactions. Hole-forming methods mainly affect the exertion of pile side resistance compared with pile end resistance. In view of pile side resistance and pile end resistance not taking effect at the same time, degree of exertion of these 2 resistances should be considered when designing cast-in-place piles in loess areas, and different partial coefficients should be used.

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Behaviour of micropiles in collapsible loess under tension or compression load

Cited by 14 publications

References 17 publications

Modelling the behavior of inundated collapsible soils

Modelling the behavior of inundated collapsible soils

Effect of Steel Casing on Vertical Bearing Characteristics of Steel Tube-Reinforced Concrete Piles in Loess Area

A Full‐Scale Field Study on Bearing Characteristics of Cast‐in‐Place Piles with Different Hole‐Forming Methods in Loess Area

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