EFFECT OF VIBRATION ON SKIN FRICTION OF SOILS-PULLING RESISTANCE OF PILE IN SAND

Abstract

In the present investigation, the behaviour of a single friction pile subjected• to vertical vibration has been studied. Though the dynamic resistance of a friction pile depends upon many factors but the effect of only frequency, acceleration, and number of revolutions have been studied. Experimental investigations carried out by Barkan have revealed that the vertical vibrations of the driven element leads to marked decrease-in the skin resistance of the soil.. No one has, so far, given an analytical approach to the problem. Based on experimental data, an analytical approach to the problem has been suggested. -stn expression for dynamic soil resistance has been established. It agrees well with the observed values. Suggestions and procedure have also been given to establish the expression if all the factors effecting the dynamic resistance of the friction pile are studied. + The results show that the dynamic resistance increases with increase in frequency, decreases with increase in the acce-leration. The variation of the dynamic resistance with acceler-ation is not linear. It also shows that the dynamic resistance decreases with increase in number of revolutions of the pile. The coefficient of lateral earth pressure ''K" has been calculated and compared with'the Rankine's values. It is found that the value of "K' is about 2/5th of the Rankine's passive value and is 4 to 6.5 times as compared to Rankin's active case. This shows that the soil mass around the pile is in a state -between active and passive case. This further shows that before 4 the full s'.,e~rinc resistonce of the soil coul,' be 'evelooer' aroun-' t'he )ile, a sun occurer' between son:' anr +pile. The stit'_c resistance of the oil e after f~i'_ure in c'vnamic condition h,s also been found out. It is observes-' h 't this re- sist?nce,is almost in ever" c?se,less than the or_ic,inal static resist,nc of the 'i1e. the re-.son for this is attributed t' t 'c f pct th-t no incre 'se in the dens .ty of the san-' mass was observer'. after the dynamic test. The limit-tions of the testinc; ' rogra..mme hav: been riven an' succ;estiins for further research h ve been ma''e.