GROUP PILE LOADS IN PLASTIC SOILS

EXPERIMENTAL TESTS WERE MADE TO DETERMINE THE RELATIONSHIP BETWEEN THE LOAD CARRIED BY A SINGLE PILE AND THAT CARRIED BY A GROUP OF PILES DRIVEN INTO PLASTIC SOILS. IT ALSO PRESENTS THE LOAD DISTRIBUTION, WITH RESPECT TO DEPTH, AND THE LOAD TRANSFER FROM THE PILES TO THE SURROUNDING SOIL AND DESCRIBES THE INSTRUMENTATION AND THE METHOD OF LOADING AND ESTABLISHES A RELATIONSHIP BETWEEN THE CAPACITY, AT FAILURE, OF A SINGLE PILE AND THE PILE WHEN ACTING AS A MEMBER OF A GROUP OF PILES. THIS SERIES OF TESTS WAS PROMPTED BY A DESIRE TO OBTAIN EXPERIMENTAL DATA WHICH COULD BE USED AS A BASIS FOR JUDGING THE ADEQUACY OF EXISTING PILE-GROUP FORMULAS AND DESIGN ASSUMPTIONS, AND TO CORRELATE, IF POSSIBLE, SOIL CONSTANTS DERIVED FROM LABORATORY ANALYSIS OF SOIL SAMPLES WITH SOIL STRESSES CALCULATED FROM FIELD-TEST DATA. THE DATA OBTAINED FROM THESE TESTS INDICATE: (1) THAT THE SINGLE PILE CARRIED ITS LOAD BY FRICTION BETWEEN THE PILE AND THE SURROUNDING SOIL WITH THE GREATER PART OF THE PILE LOAD TRANSFERRED FROM THE PILE TO THE SOIL IN THE UPPER HALF OF THE PILE AND WITH RELATIVELY HIGH SHEAR VALUES EXISTING IN THE SOIL FOR A SHORT LENGTH OF THE PILE, (2) THAT THE LOAD DISTRIBUTION TO THE PILES IN THE GROUP WAS FAIRLY UNIFORM, EACH PILE INCLUDING THE CENTER PILE, CARRYING A SHARE OF THE LOAD, (3) THAT THE EFFECT OF THE PILE SPACING WAS REFLECTED BY THE DROP IN THE SHEAR VALUES BETWEEN THE CORNER PILES, SIDE-CENTER PILES AND THE CENTER-PILE OF THE GROUP, AND (4) THAT THE LOAD ON THE INDIVIDUAL PILES WITHIN THE GROUP WAS TRANSFERRED TO THE SOIL BY SHEAR, WITH THE MAXIMUM VALUES OCCURRING AT SLIGHTLY HIGHER LEVELS THAN FOR THE SINGLE PILE AND THESE MAXIMUM VALUES OCCURRED OVER A MUCH LONGER LENGTH OF THE PILE. /AUTHOR/