Piles located in consolidating soil are subjected to indirect loading resulted from the settlement of adjacent soil. Both pile and soil undergo downward movements caused by the axial pile load and surcharge loading on surrounding area. Both dragload and downdrag imposed on the pile are time dependent. The purpose of this research was to analyse and quantify the dragload and down drag imposed on single pile. Effect of pile head load was considered. Shielded and unshielded piles are analysed. Three dimensional nonlinear analyses using ABAQUS 6.12 have been utilised. The research investigates the size of the surcharge loaded area, location of the pile tip and pile head load on the dragload and down drag imposed on the pile. Based on numerical results the study revealed that sacrificing piles, which are unloaded piles, ''hang up'' the soil between the piles in the group and, thus, the vertical effective stress around the shielded pile is reduced. Numerical results proved that an average value of the shear stress mobilisation factor b mobilised along unloaded shielded central pile varies between zero at neutral plane (NP) and 0.27. The long term dragload of the shielded floating pile is about 67% of the long term dragload of unshielded floating single pile. ª 2015 Production and hosting by Elsevier B.V. on behalf of Faculty of Engineering, Alexandria University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

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Soil collapse occurs when increased moisture causes chemical or physical bonds between the soil particles to weaken, which allows the structure of the soil to collapse. Collapsible soils are generally low-density, fine-grained combinations of clay and sand left by mudflows that have dried, leaving tiny air pockets. When the soil is dry, the cemented materials are strong enough to bond the sand particles together. When natural soil becomes wet, moisture alters the cementation structure and the soil's strength is compromised, causing collapse or subsidence. Based on soil type and density, the potential for encountering collapsible soils throughout most of the project alignment is low. Conditions in arid and semi-arid climates like Borg El Arab, near Alexandria Egypt favor the formation of the most problematic collapsible soils. The behavior and performance of compacted sand replacement over treated collapsible soil by pre-wetting and compaction are investigated in the current study. Field investigation was performed in the form of plate loading tests conducted on compacted sand replacement over improved collapsible soil. Field plate load tests program was developed to explore the effect of compacted sand replacement thickness on collapsibility potential. Treated collapsible soil was replaced with imported cohesionless soil with variable thickness up to footing width. Results proved that the improvement of collapsible soils by sand/crushed stone replacement is possible to control/mitigate their risk potentials against sudden settlement when exposed to water. Replacement soil increases the rate and reduces the amount of footing settlement. For compacted collapsible soils, partial replacement by compacted sand/crushed stone layers decreases collapsibility potential risk. Results also, introduce the development of practical, economical and environmentally safe geochemical methods for collapsible soil stabilization and collapsible risk mitigation. ª 2015 Production and hosting by Elsevier B.V. on behalf of Faculty of Engineering, Alexandria University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/). ª 2015 Production and hosting by Elsevier B.V. on behalf of Faculty of Engineering, Alexandria University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Please cite this article in press as: N.A. Ali, Performance of partially replaced collapsible soil -Field study, Alexandria Eng. J. (2015), http://dx.

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