Dynamic Analysis of Embankments Reinforced with Micro-Piles

In facing with problematic soils such as loose soil with low bearing capacity, high permeability, and soil with liquefaction potential,  two approaches are common: the use of bearing elements, and modification  mechanical-physical properties of the soil. Each of the above approaches has its own characteristics. Some innovative technics have combined the two approaches containing the advantages of both. Among these techniques, one can refer to the application of micro piles accompanied by grouting. In addition to functioning as a bearing element, this technique also improves mechanical properties of the soil due to grouting [1].

Micro pile is a replacement pile being accompanied by boring and grouting. Micro piles are often reinforced using steel components. They are commonly used to increase the foundations' strength against static and seismic loading, reinforcing the slopes, and stabilizing the walls of excavated areas [1]. At first, using micro piles was solely considered to improve the weak foundation of buildings. By developing this technique, the application was extended to other geotechnical areas such as stabilizing the slopes and reducing the potential of liquefaction. Presently, the instruction recommended by US.FHWA is widely accepted reference by designers and contractors in this field [2].

Recent seismic tests have shown that micro pile systems can be used in seismic areas. However, engineering data on the seismic performance of micro pile systems is limited and more research is needed to create and assess seismic designing techniques and engineering guidelines. Before applying micro piles as a measure to reinforce the embankments, experimental and numerical studies are required to confirm the efficiency of this method. Numerical studies conducted by engineers in recent years show the efficiency of micro piles in this application. In this regard, one can refer to the two-dimensional study of seismic behavior of micro pile groups in sandy soil conducted by Maghsoodi et al. [3] and three-dimensional elastoplastic study of the seismic performance of inclined micro piles by Sharour et al. [4]. Furthermore, employing micro pile networks in rapid excavation of a railway project by Bruce and Janes [5], investigating the stability of the slopes reinforced with micro piles by Sun et al. [6] could be mentioned in this field. Dynamic and static analysis of micro piles to reinforce high embankments of railway on loose foundation by Esmaili et al. [7], and comprehensive parametric study to achieve better perception of seismic behavior of micro piles in slopes by Elahi et al. [8] have been carried out to get better understanding of this subject.