PAVEMENTS AND INFLUENCES AFFECTING OR DETERMINING THEIR PERFORMANCE

A SURVEY WAS CONDUCTED OF 3000 MILES OF PAVEMENT IN WISCONSIN TO ATTEMPT TO ASSOCIATE SPECIFIC PAVEMENT CONDITION TO THE CIRCUMSTANCES OF ITS EXPOSURE. AGRICULTURAL SOIL MAPS WERE USED AS A BASE, AND THE SOILS AS SHOWN BY THEM WERE CORRELATED TO THE GEOLOGY OF THIER FORMATION AND DEPOSITION, AND THE CHARACTER AND PROXIMITY OF BEDROCK AND OTHER SUBSURFACE CONFIGURATIONS. LONGITUDINAL CRACKING OCCURS IN SOILS OF DIFFERENT CHARACTERISTICS AND NOT IN OTHERS. IT IS FOUND ONLY WHERE THE PAVEMENTS, REGARDLESS OF TYPE OF AGGREGATE, WERE FOUNDED IN SOILS OF THE CALCEROUS GLACIAL DRIFT. FAULTING OCCURS AT JOINTS WITH OR WITHOUT LOAD TRANSFER DOWELS AND IS A FUNCTION OF THE SOILS. RHYTHMIC WAVINESS AND BLOWUPS OF RIGID PAVEMENTS ARE RELATABLE TO THE SOIL-MOISTURE CONDITIONS OF THE SUBGRADE SOILS RATHER THAN TO TEMPERATURE STRESSES WITHIN THE SLAB. THE STUDY OF PUMPING AND THE CHARACTERISTICS OF THE SUBSEQUENT FAILURE OF SLABS IS INDICATIVE OF PAVEMENT ACTION AND STRESSES OTHER THAN COMMONLY ASSUMED, AND A DISCUSSION IS PRESENTED. AGGREGATE BASE COURSES CONSTRUCTED TO HIGH DENSITIES AND SUPPORTING IMPERVIOUS BITUMINOUS PAVEMENTS WERE FOUND TO SUFFER A COMPLETE LOSS OF DENSITY AND WERE WATERLOGGED IN THEIR LOWER ZONES, WITH THE UNDERLYING PERVIOUS MATERIAL BEING ONLY SLIGHTLY DAMP. THE GREATER INCIDENCE OF HEAVY LOADS COINCIDING WITH A REVERSAL OF THE METEOROLOGICAL CYCLE FROM THE GENERAL DROUGHT CONDITIONS OF THE PRECEDING DECADE AND A HALF CAUSED THE EXTRAORDINARY DESTRUCTION OF PAVEMENTS DURING THE LAST DECADE. DUE TO THE PRESENCE OF AN IMPERVIOUS PAVEMENT AND THE ENERGY OF MOVING LOADS TRANSMITTED THROUGH THE PAVEMENTS, THE MOISTURE CONDITIONS IN THE SUBGRADE SOILS ARE NOT COMPARABLE TO THOSE IN SOILS FREELY EXPOSED TO THE ATMOSPHERE. OBSERVATIONS OF THE POSITION OF MOISTURE IN THE SOILS AND OTHER PHENOMENA OF MOISTURE MOVEMENT, TOGETHER WITH A STUDY OF LITERATURE ON THE SUBJECT, INCLUDING FROST ACTION, LEAD TO THE DEVELOPMENT OF AN EXPLANATION OF THESE PHENOMENA MORE COMPATIBLE WITH OBSERVED MANIFESTATIONS THAN THE POPULAR THEORY OF CAPILLARITY. A DISCUSSION IS PRESENTED OF SUB-BASE COURSES, WITH PARTICULAR REFERENCE TO THE OPERATION AND FUNCTIONING OF FREELY DRAINING PERMEABLE SAND OR SAND-GRAVEL LIFT OR BALLAST COURSES. /AUTHOR/