The improving of the pile surrounding soil still insufficiently studied. Many researchers treated with the surrounding soil to improve the pile capacity for resisting the lateral loads or liquefaction. Many methods of improvement are adopted to increase pile capacity .Compaction and replacing surrounding soil are adopted in this study as improvement method. Experimental work was executed on pile model using a compression machine. At first tests, were performed on soil to determine soil properties. The bored and driven methods of installation are performed in two different ways. Steel bar model were used with two different embedded lengths (10,15) cm. This model was tested at first stage without improvement for both method of installation (bored, driven) and for two lengths for each one for studying the behavior of pile model in natural case. The next stage was to replace and compact the surrounding soil ,different diameter were used for compacting surrounding soil , and with length equal to embedded length of pile model without extending under pile model tip. For each diameter of improvement around pile model ,the model tested for two method of installation and for two embedded length. The load-settlement curve are plotted and the value of pile capacity was extracted. These results give indication for the effect of improvement surrounding soil on pile capacity. HANSEN equation was adopted to estimate the pile capacity and compare it with the results obtained from experimental work with respect to the expected behavior of pile and improved soil block surrounded pile .The discussion of results are summarized. Clear observation are formed , that is the best choice for improvement are located at tight limits around pile, because the high apparent cohesion of soil particles that appear due to compaction ,which makes compacted soil and pile behave as one block and that will rise the value of tip load resistance. In this study the best choice for improvement was (43 mm) this which approximately equal to distance of (D) from face of pile with respect to pile model diameter (D=13mm)and with ((D improvment/D pile)equal to3.3)) . This improvement achieve best result by increasing both tip load and skin friction, by which pile capacity will increase for driven pile case 1-from (0.015kN) of natural case to (0.047 kN) for (15 cm) embedded length which is mean two times increment in pile load capacity . 2-(0.0095kN) of natural case to (0.033kN) for (10 cm) embedded length one and half time increment in pile load capacity And for bored pile case 1- (0.0058kN) of natural case to (0.114kN) for (15 cm) embedded length increment in pile load capacity 2-(0.0038kN) of natural case to (0.075kN) for (10 cm) embedded length which is mean (13) times increment in pile load capacity. Any increasing in diameter of improvement will not give increasing in tip load resistance and the increment will occur just in skin friction of compacted soil block and around soil for the case of bored pile. Conclusion of this study are summarized about the effect of compaction and replacement on properties of surrounding soil properties and it effect on pile load capacity.
