Abstract:Stresses under the caps in cement-soil piles composite ground are obtained by putting earth-cell under the caps with one pile,four piles and nine piles respectively in field test. Three important factors,i.e. pile length,pile space and pile number,which influence the stress ratios are studied in detail. Under the same condition,the stress ratio distribution curve styles obtained by tests are compared with those by theoretic calculation according to Mindlin¢s stress solution and layer summation. It is demonstrated that the stress ratio curve is composed of two segments,the descending segment at lower load levels and the ascending segment at higher load level,and that the pile-soil stress ratio of the ascending segment is between 4.0 and 7.0,which provides experimental and theoretical references when the pile-soil stress ratio is constant. It is also shown that the stress concentration coefficient at the top of the pile and the soil lessening coefficient increase while the replacement reduces,but the pile function is enhanced. The stress concentration coefficient varies from 2.00 to 3.25,and the lessening coefficient varies from 0.35 to 0.70 by field test;the stress concentration coefficient varies from 2.40 to 4.50,and the lessening coefficient varies from 0.40 to 0.55 by theoretic calculation.