Development of Excess Pore Water Pressure around Piles Excited by Pure Vertical Vibration

In this study,an assessment to excess pore water pressure generated around a single pile and pile group excited by two opposite rotary machines embedded in saturated sandy soil was considered experimentally. a small-scale physical model was manufactured to accomplish the experimental work in the laboratory. the physical model consists of: two small motors supplied with eccentric mass of 0.012 kg and eccentric distance (20 mm) representing the two opposite rotary machines,an aluminum shaft 20 mm in diameter as the pile,and a steel plate with dimensions of (160 × 160 × 20 mm) as a pile cap. the experimental work was achieved taking the following parameters into considerations: pile embedment depth ratio (l/d),spacing between piles (s) and operating frequency of the rotary machines. twelve tests were conducted in medium dense fine sandy soil with 60 % relative density. in all these tests,the change in excess pore water pressure was measured around the pile at two spots: at the middle of the pile and at its tip. the results revealed that the generation of excess pore water pressure was affected by the following parameters: slenderness ratio of the pile,operating frequency of the machines,and the soil permeability. however,for all cases,it was found that the pore water pressure generated during operation was not greater than 20 % of the initial hydrostatic pressure. using pile foundation reduced the amplitude of vertical vibration by about (300 %) for all operating frequencies,lengths of piles,pile spacings and number of piles. in addition,the presence of piles reduced the disturbance (fluctuation) in this amplitude by about (400 %). for single pile,and under the same operating frequency,a small decrease in the amplitude of vertical vibration resulted from increasing the length of the pile. © 2016,iran university of science and technology.