Scale model investigation of the effect of vertical load on the lateral response of micropiles in sand

Kershaw, Kyle; Luna, Ronaldo

doi:10.1080/19375247.2018.1462040

Cited by 13 publications

(5 citation statements)

References 8 publications

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“…In the study of micropile groups, it is customary to take into account factors such as pile spacing, arrangement patterns, and the influence of pile group effects to ensure the stability and uniformity of micropile foundations [20]. Researchers have investigated the load-bearing performance of micropile groups under both vertical and horizontal loads, as well as the group effects, through a combination of field and model tests [21][22][23][24]. However, the test results have exhibited contradictions, showing variations in the load-bearing performance of micropile groups.…”

Section: Introductionmentioning

confidence: 99%

Horizontal and Uplift Bearing Characteristics of a Cast-In-Place Micropile Group Foundation in a Plateau Mountainous Area

Li,

Ren

2023

Sustainability

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Micropile groups have been progressively more frequently adopted in the construction of transmission tower bases due to their compact size and flexible construction advantages. However, the load-bearing characteristics and deformation mechanisms of micropile groups are complex, and the study of their coupling effects under combined loads remains unclear. Consequently, this paper presents a field static load test of micropile groups in a highland mountainous area. The analysis encompasses the axial force distribution and load-sharing ratio of micropiles. With a focus on micropile groups subjected to both uplift and horizontal combined loads, the coupled effects under different load combination ratios are examined using numerical simulation methods. The key findings are as follows: During the uplift loading process, the load distribution among individual piles is relatively uniform, with lower side friction resistance gradually coming into play to counterbalance the top load. The load–uplift displacement curve exhibits a steep characteristic, making it susceptible to sudden failure in practical engineering applications. Under the simultaneous action of uplift (V) and horizontal (H) loads, the unbalanced lateral frictional resistance on both sides of the pile segment induces additional bending moments, which is an important part affecting the load-coupling mechanisms. The uplift resistance capacity of micropile groups decreases with an increase in horizontal load, while the horizontal load-carrying capacity initially decreases and then increases with an increase in uplift load. The space enclosed by the yield envelope under combined load, and the vertical line of the ultimate load, is divided into a ‘failure zone’ and a ‘safety zone.’ In the design of the pile foundation, the uplift bearing capacity reduced by the ‘failure zone’ should be taken into account.

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Section: Introductionmentioning

confidence: 99%

Horizontal and Uplift Bearing Characteristics of a Cast-In-Place Micropile Group Foundation in a Plateau Mountainous Area

Li,

Ren

2023

Sustainability

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“…The design guidelines for micropiles are often used for projecting the practical performance of minipiles, due to the similar characteristics of the two. There is extensive literature on static lateral [45,48] and static and cyclic compressive and pull-out behaviour of micropiles [17,29,59,57]. However, there is only limited literature on the behaviour of micropiles under cyclic lateral loading.…”

Section: Introductionmentioning

confidence: 99%

Battered minipile response to low-frequency cyclic lateral loading in very dense sand

Mondal

Disfani

2022

Acta Geotech.

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This experimental study investigates the response of vertical and battered minipiles to two-way symmetrical low-frequency (0.1 Hz) cyclic lateral loading. Laboratory (1-g) tests were performed on scaled-down minipiles in very dense cohesionless soil, for batter angles of 0°, 25° and 45°. The cyclic loading is classified into two categories: multi-amplitude and long-term single amplitude, where force-controlled load was applied at a constant frequency. The minipiles were instrumented with optic fibres, and strain profiles were obtained at each loading stage, in both compression and tension stroke. The results are presented in terms of hysteresis loops, variation of normalised stiffness, minipile strain and bending moments under cyclic loading. In the multi-amplitude loading category, backbone curves show a stiffer force–displacement response in tension stroke than in compression stroke. For the single-amplitude category, the area of the hysteresis loop is largest for 45° battered minipiles with the lowest accumulated deformation. The normalised stiffness at the end of 50 cycles is highest for 25° minipiles with a value slightly greater than one. The strain profiles along the minipiles show stabilisation of measured strain before the number of cycle reaches 50, for all three battered conditions. A multi-surface hardening constitutive model is used to explain the effect of shearing and cyclic loading, with increasing loading amplitude on 25° battered minipiles. These test results are indicative of better performance capability of 25° battered minipiles, in terms of secant stiffness, compared to the vertical and 45° battered cases.

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“…However, it mainly plays a role of presupport in moderately weathered rock formations and strongly weathered rock formations. Kershaw and Luna [21] conducted comparative experiments on micropiles subjected to horizontal loads in loose and dense sand, respectively. It is found that the influence of sand density on the load deflection behavior of laterally loaded piles is much greater than the lateral stiffness (casing thickness) of micropiles.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Lateral Bearing Mechanical Characteristics and Damage Numerical Simulation of Micropile

Liu

Huang

et al. 2021

Advances in Civil Engineering

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The construction site of the foundation pit support project in the urban area is narrow. Micropile has the advantages of flexible pile position layout, strong site adaptability, and fast construction speed, which can effectively control the horizontal displacement of the foundation pit and ensure the safety of surrounding buildings. However, the lateral bearing capacity of micropile is weak. In order to study the lateral force characteristics and failure characteristics of micropile, laboratory tests on the flexural and tensile strength of reinforced concrete micropiles with different diameters and with or without external steel pipes were performed. The authors studied the lateral force characteristics and failure characteristics of various types of micropiles. Based on numerical simulation software ABAQUS, the measured yield strength of the specimen was used as the loading force. And taking the occurrence and development of concrete damage into consideration, the loading process was simulated. The result shows the following: (1) the micropile specimens with external steel pipe had better flexural performance than the bare micropiles and the mechanical characteristics of the specimens changed from brittleness to plasticity; (2) the degree of concrete damage is greatly reduced after the external steel pipe is attached, and the bearing capacity of the micropile specimen of the same diameter is increased by 70% after the external steel pipe is added; and (3) the specimens were mainly damaged due to tensile damage. The calculation formula for the lateral bearing capacity of the concrete-filled steel tube micropile considering the damage is proposed through fitting analysis. The calculation formula, the finite element calculation value, and the calculation formula proposed by other scholars are compared with the authors' test and the test data of other scholars. The meta-calculation results, experimental results, and formula calculation results proposed by the authors have high accuracy.

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Scale model investigation of the effect of vertical load on the lateral response of micropiles in sand

Cited by 13 publications

References 8 publications

Horizontal and Uplift Bearing Characteristics of a Cast-In-Place Micropile Group Foundation in a Plateau Mountainous Area

Horizontal and Uplift Bearing Characteristics of a Cast-In-Place Micropile Group Foundation in a Plateau Mountainous Area

Battered minipile response to low-frequency cyclic lateral loading in very dense sand

Experimental Study on Lateral Bearing Mechanical Characteristics and Damage Numerical Simulation of Micropile

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