Abstract: Lots of problematical piles were discovered during inspection of loose core to cement mixing piles,and the piles were in zonal distribution through inspection of excavation.Emergence of the problematical piles was that the red clay was polluted.In this paper,a series of tests of physical and mechanical properties were done by choosing a representative red clay sample of cement mixing piles being polluted in the reinforcement areas.Combining inspection of loose core and excavation,it was discussed influences of the red clay polluted by organic matter on the mechanical property of the cement mixing piles.The research indicates that mechanical softening effects were gradually weakend and the decrease of the indexes of physical and mechanical properties were decreased with the decrease of the distance between cement mixing piles and septic tank.As a result,the problematical piles were in zonal distribution.