ACCELERATION OF THE CONSOLIDATION PROCESS UNDER ROAD EMBANKMENTS BY MEANS OF SAND DRAINS

DIE BESCHLEUNIGUNG DES KONSOLIDIERUNGSVORGANGES UNTER STRASSENDAEMMEN MIT HILFE VON SANDDRAINS

TESTS ALREADY CARRIED OUT ON SAND DRAINS IN SOFT SOILS (CLAY) AND NON-DESTRUCTIVE DEFORMATION MEASUREMENTS DURING CONSOLIDATION HAVE SHOWN THAT DEFORMATION OCCURS IN THE AXIAL AND RADIAL DIRECTION, SO THAT TOGETHER WITH COMPRESSION SHEAR DEFORMATIONS ALSO OCCUR IN THE SOIL. THESE INFLUENCE THE PROCESS IN SUCH A WAY THAT IT CANNOT BE DETERMINED BY MEANS OF A LINEAR, UNI-DIMENSIONAL THEORY. THE TESTS ALSO SHOWED THAT SAND DRAINS, BECAUSE OF THE CHANGES OF VOLUME IN THE SOIL AND THE RUNNING DOWN OF THE CONSOLIDATION PROCESS, BUCKLE OUTWARDS AND MAY EVEN SHEAR OFF IF THERE ARE LARGE SETTLEMENTS, THUS BECOMING PARTIALLY INEFFECTIVE. ON THE BASIS OF RESULTS OBTAINED HITHERTO AND THE PRESENT STATE OF KNOWLEDGE THE FOLLOWING POINTS ARE TO BE EXAMINED: (1) THE CHANGES IN SHEAR STRENGTH WHICH MIGHT BE CAUSED BY THE INCORPORATION OF THE SAND DRAINS, DEPENDING ON PLACE AND TIME; (2) THE SOIL TYPES IN WHICH SAND DRAINS ARE USEFUL AND ECONOMICAL, AND THE UNDRAINED SHEAR STRENGTH OF THESE SOILS; (3) THE POSSIBLE EFFECT OF THE DIMENSIONS OF THE DRAIN ON THE DRAINAGE PROCESS; (4) POSSIBLE EFFECT OF THE TYPE OF DRAIN AND TYPE OF MANUFACTURE ON THE CONSOLIDATION PROCESS. IT IS ANTICIPATED THAT A COMPUTER PROGRAM BASED ON THE FINITE ELEMENT METHOD, WHICH IS ALREADY BEING WRITTEN, WILL UNDERGO FURTHER DEVELOPMENT, SO THAT VALID DATA CAN BE OBTAINED ON THE USEFULNESS OF THE DRAINS.