EFFECT OF BASE REINFORCEMENT ON THE BEHAVIOR OF EMBANKMENT OVER SOFT SUBSOIL

Abstract

A case history  of both  reinforced and unreinforced embankments on soft subsoil  built to  failure  is described. The  results  of a laboratory model  test  about  the behavior   of embankment on  soft  soil  are  referred  during  discussions. The  effect  of geotextile reinforcement on embankment behavior is discussed by comparing the field data  of with   and  without  reinforcement  cases.   The  field   data  as  well   as  analysis indicate  that  the reinforcement had a certain  effect  on embankment stability.  However, at working  state  (normally  with  a factor  of safety  of  1.2 to 1.3),  the reinforcement did not   have   an   obvious   effect  on   subsoil   response.  Only   under   the   condition  that unreinforced embankment approached to failure,  the effect of reinforcement on subsoil could  be noticed. The  laboratory model  test results  indicated  that  if the reinforcement is  strong   enough,   the  effect   of  reinforcement  is  considerable.  It  is  suggested  that although   the  geotextile  certainly   has  a  beneficial  effect  on  embankment  over  soft subsoil,   due  to  the  relative  lower   stiffness  of  geotextile,  to  achieve   a  substantial improvement  on  embankment behavior,  the  multi-layer  geotextile  reinforcements or high strength  geogrid  may be needed.  This  case history  also demonstrated that the rate of lateral  displacement and excess  pore  pressure  development are sensitive indexes  for the stability  of embankment on soft subsoil.