الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Micropiles are small-diameter reinforced grouted piles that are commonly not higher than 30 cm in diameter. Nowadays, micropiles have been used widely in situ reinforcement and for structural support purposes because of their suitability to be used in congested areas and almost in all soil types, and their flexibility in seismic conditions. Micropiles are widely used for slope stabilization, for controlling structural settlement, and in some cases as retaining structures. They are also used for resisting uplift dynamic loads, seismic retrofit mainly in restrictive and low headroom areas, retrofitting historical monuments.
The lack of studies on the prediction of micropiles’ seismic response makes it an essential topic to be studied more. This thesis attempts to study the effect of lateral dynamic loads on a structure’s response with different foundation type cases. A representative soil model is conducted to represent the soil-structure interaction system under seismic excitation supported with proper boundary conditions in PLAXIS 2D for dynamic analysis based on previous recommendations. The choice of boundary conditions is verified according to the amplification factor’s theoretical solution on a model with a simple material and harmonic motion. The behavior of piles is studied and verified from previous results under static and dynamic loading states. A free-field site response analysis of the main soil model is then performed at different structure cases and compared to evaluate the structure’s behavior during different earthquakes. An extensive parametric study, considering earthquake magnitude, foundation type, pile diameter, pile length, and the number of piles, has been carried out to investigate the behavior of micropiles. The results of this study showed that the structure’s seismic response is highly affected by the properties of the sub-surface soil layer. The main conclusion of this study showed that underpinning using micropiles is an efficient technique for controlling the seismic response of existing structures.