Field study on axial bearing capacity and load transfer characteristic of waveform micropile

Jang, Young-Nam; Han, Jin-Tae

doi:10.1139/cgj-2017-0155

Cited by 18 publications

(16 citation statements)

References 17 publications

(13 reference statements)

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“…This finding indicates that shear keys along the pile increased its shaft resistance. This effect was more significant in the soil region with a higher confining pressure, which is in good agreement with the results of Jang and Han [36,37]. Interestingly, WMP2 provided a similar shaft resistance to CMP1 despite being only about 80% of its length.…”

Section: Axial Load Transfer Mechanism In Micropilessupporting

confidence: 90%

“…The piles' lengths, L, are related by the scale factor N. The effects of the piles' form and length, and consequently their axial stiffness, were evaluated by comparing two types of conventional micropile (CMP) and two types of waveform micropile (WMP) in foundation underpinning tests. The WMP (Figure 2a), with shear keys along the pile shaft, demonstrated a higher stiffness and load bearing capacity than the CMP [35][36][37]. Although the limitation of the soil stress effect in small-scale tests is difficult to overcome, to establish a reliable relation between the small-scale model and the prototype model requires adopting a suitable scale and satisfying the scaling law [38,39].…”

Section: Test Apparatusmentioning

confidence: 99%

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Experimental Investigation of Micropile Stiffness Affecting the Underpinning of an Existing Foundation

2019

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Underpinning in an existing foundation with piles is commonly used to improve their load-bearing capacity to allow vertical extension works. This study evaluated the effect of the piles’ stiffness on the load-sharing behavior of existing and underpinning piles during the vertical extension of existing buildings. A series of 1 g model tests, all with a scale factor of 1/20, was used to compare the underpinning performance of micropiles of varying stiffness. The performance was evaluated in terms of total settlement reduction and load sharing capacity. The results showed that the underpinning performance improved with the increase of underpinning pile stiffness. The ratio of carried loads of the underpinning pile to the existing pile increased linearly with its increasing stiffness (as expressed as a ratio relative to the stiffness of the existing pile).

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Section: Axial Load Transfer Mechanism In Micropilessupporting

confidence: 90%

Section: Test Apparatusmentioning

confidence: 99%

Experimental Investigation of Micropile Stiffness Affecting the Underpinning of an Existing Foundation

2019

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“…The high-strength steel rebar transfers the load to the surrounding ground through the grout body to develop frictional resistance. Therefore, the micropile supports the load via the shaft resistance created between the pile shaft and the ground while the load carrying capacity resulting from tip resistance is generally neglected due to small diameter of the micropile [15]. Federal Highway Administration (FHWA) micropile design guidelines specify the bond strength (a bond ) considering the frictional resistance between the grout and the ground for micropile design [10].…”

Section: Introductionmentioning

confidence: 99%

“…In previous research studies, the constructability and the increased bearing capacity of the waveform micropile were verified through both field tests and field applications. In addition, the test results showed that the waveform micropile is an effective method for reducing construction time with simplified construction steps relative to the conventional micropile [15].…”

Section: Introductionmentioning

confidence: 99%

Analysis of the shape effect on the axial performance of a waveform micropile by centrifuge model tests

Jang

Han

2018

Acta Geotech.

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A new type of micropile, the waveform micropile, has been developed to provide improved load-bearing capacity compared with that of a conventional micropile. The waveform micropile has a wave-shaped grout with a partially enlarged shear key formed by the jet grouting method on the cylindrical shaft of the micropile. Previous research has determined that the waveform micropile can be installed faster than the conventional micropile and that the bearing capacity increases as the wave-shaped grout provides additional shaft resistance between the ground and the grout. In this study, a series of centrifuge model tests were conducted on the waveform micropile model with various wave-shaped grouts to analyze the relationship between the arrangement of the shear key and the load-bearing mechanism of the waveform micropile. The load-settlement relationship and the load-transfer mechanism were analyzed based on the test results of six test micropiles, including three waveform micropiles with a single shear key at various depths, one waveform micropile with a multiple shear key along the pile depth, and two micropiles with only a cylindrical shape. The test results showed that the ultimate bearing capacity of the waveform micropile was over two times greater than that of the conventional micropile. The rate of increase in the bearing capacities of each waveform micropile differed with the shape of the shear key. Furthermore, the characteristics of the load-sharing ratio due to the shaft resistance and end bearing varied depending on the shape of the waveform micropiles.

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“…In addition, the WMP does not require casings during drilling, and therefore, can facilitate a faster installation process and cost effectiveness (Drbe and El Naggar, 2014;Abdlrahem and El Naggar, 2019). During its construction, jetgrouting methods are used to develop shear keys along the pile shafts by controlling the grouting pressure and ascent time (Jang and Han, 2018). Figure 1 depicts the construction process of an instrumented WMP: (a) drilling a hole through a water jet; (b) waveform grout formation by controlling grouting pressure and time; (c) inserting reinforcing steel bar; (d) grout curing for a month.…”

Section: Introductionmentioning

confidence: 99%

A field study on the load sharing behavior of a micropiled raft underpinned by a waveform micropile

2022

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A waveform microiple(WMP) uses jet grouting method to generate shear keys along the pile shaft for improving the shaft resistance and cost efficiency. In this study,field loading tests were performed in this study to characterize the load sharing behavior upon inclusion of a waveform micropile (WMP) in a group of four micropiled-raft. First, single-pile compressive loading tests were conducted on three WMPs and five Type A micropiles (MP). Subsequently, a group-pile loading test was performed on a piled raft comprising 2 × 2 MPs and a central WMP. The load–settlements, axial stiffnesses, and load transfer mechanisms of individual MPs were analyzed during the tests, including the short- and long-term effects of the axial stiffnesses of the MPs on the load sharing ratio of the micropiled-raft. The single-pile loading test results revealed that the shear keys along the WMPs caused its bearing capacities and axial stiffnesses to be 1.5 times and 2–5 times higher than those of MPs, respectively. In the micropiled-raft loading test, the load sharing ratios of the MPs increased with their axial stiffnesses, and the highest load sharing capacity was exhibited by the WMP, which constituted 30% of the total load and 2–3 times that of MPs. Moreover, the influence of raft on the load-sharing capacity should be considered as well.

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Field study on axial bearing capacity and load transfer characteristic of waveform micropile

Cited by 18 publications

References 17 publications

Experimental Investigation of Micropile Stiffness Affecting the Underpinning of an Existing Foundation

Experimental Investigation of Micropile Stiffness Affecting the Underpinning of an Existing Foundation

Analysis of the shape effect on the axial performance of a waveform micropile by centrifuge model tests

A field study on the load sharing behavior of a micropiled raft underpinned by a waveform micropile

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