Vertical load-carrying behavior and design models for micropiles considering foundation configuration conditions

Abstract

In the present study, the vertical load-carrying behavior of micropile foundations with various configuration conditions was investigated based on results from model load tests. Considered configuration conditions included micropile inclination angle, spacing of micropiles, and types of micropile foundations. The ultimate load capacity of micropiles varied with installation angle, showing an initial increase and peak followed by a gradual decrease with further increase in installation angle. The ultimate load capacity of micropiled rafts was affected by both installation angle and micropile spacing. The load-carrying mechanism of micropiles for the inclined condition was proposed based on the decomposed axial and lateral load and resistance components. Using the proposed load-carrying mechanism and test results obtained in this study, the load capacity ratio for an inclined micropile was proposed. The group effect and interaction effect factors for group micropiles and micropiled rafts were proposed, respectively, all of which can be used to estimate the load-carrying capacity of micropile foundations. Field load tests were conducted and it was seen that estimated results using the proposed method were in good agreement with measured results. Additional comparison with case examples from the literature also confirmed the validity of the proposed method.

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

“…The micropile was expected to satisfy the technical requirements for construction of artificial ground. However, since the construction cost of micropiles using steel rebar has increased compared to other foundation types, several studies have been conducted to improve the bearing capacity and economic efficiency of micropiles through the development of a new micropile method (Choi and Cho 2010;Kim et al 2016;Kyung et al 2017) The waveform micropile was developed in order to provide additional shaft resistance by forming the grout into a waveform shape by jet grouting method. The bearing capacity enhancement by the waveform micropile has been verified though 2D numerical analysis and model tests Jang and Han 2015).…”

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

“…This is because the current design method considers only the socketed pile length into a hard layer (e.g., weathered soil and weak rock) as a bearing stratum while ignoring the shaft resistance at the upper soil layer, which has a relatively weak strength. Accordingly, efforts have been made to increase the relative capabilities of the micropile by improving the installation method and structural design to enhance the bearing capacity of state-of-theart methods [5,18,20].…”

Assessment of micropiled rafts performance under pure lateral loading

“…The 3D model used to carry out the analysis was developed using the computer code PLAXIS 3D. The validity of the FEA was checked by using the results of full-scale field loading tests that were obtained from (Kyung et al 2017;Kyung and Lee 2018) and comparing them with those obtained from the FE analyses. A half of the micropiled raft foundation was modeled due to the symmetry to decrease the computation time.…”