00234464

Component

https://onlinepubs.trb.or...bproceedings/21/21-039.pdf

THE MOISTURE RETAINING AND TRANSMITTING PROPERTIES OF UNSOLIDIFIED POROUS MATERIALS IS OF CONSIDERABLE IMPORTANCE IN DETERMINING THE PHYSICAL PROPERTIES AND SUITABILITY FOR CERTAIN ENGINEERING APPLICATIONS. SOIL MOISTURE CONDITIONS MAY BE DESCRIBED IN TERMS OF THE SECURITY WITH WHICH THE WATER IS HELD BY THE SOIL. THIS SECURITY CAN BE MEASURED IN TERMS OF THE THERMODYNAMIC FREE ENERGY OF THE WATER ITSELF. MEASUREMENTS OF THE PRESSURE, VAPOR PRESSURE, FREEZING POINT DEPRESSION, ETC., MAY BE USED TO EVALUATE THIS FREE ENERGY FUNCTION. PF CURVES RELATING THE MOISTURE CONTENT OF SOILS TO A LOGARITHMIC FUNCTION OF THE FREE ENERGY REVEAL THAT A CONTINUOUS FUNCTIONAL RELATIONSHIP EXISTS OVER A MOISTURE CONTENT RANGE EXTENDING FROM SATURATION TO OVEN DRYNESS. MOISTURE CONDITIONS IN SITU CAN BE FOLLOWED WITH A MINIMUM OF DISTURBANCE TO THE SURROUNDING SOIL BY THE USE OF A TENSIOMETER. TENSIOMETERS ARE OF USE IN FOLLOWING FLUCTUATIONS IN ELEVATION OF WATER TABLES AND IN TRACING THE ADVANCE OF A WETTING FRONT THROUGH A SOIL FOLLOWING THE ADDITIONS OF WATER BY RAINFALL OR BY IRRIGATION. THE ENERGY CONCEPT OF SOIL MOISTURE AIDS IN EXPLAINING MOISTURE FLOW PHENOMENA. FOR SATURATED FLOW DARCY'S LAW STATES THAT THE RATE OF FLOW IS PROPORTIONAL TO A POTENTIAL GRADIENT CALLED THE HYDRAULIC GRADIENT. THE PROPORTIONALITY CONSTANT IS KNOWN AS THE COEFFICIENT OF SATURATED PERMEABILITY. IN PROBLEMS INVOLVING THE FLOW OF MOISTURE THROUGH AN UNSATURATED POROUS MEDIA THE RATE OF FLOW IS PROPORTIONAL TO THE POTENTIAL GRADIENT. THE NUMERICAL VALUE OF THE PROPORTIONALITY CONSTANT HAS BEEN SHOWN TO VARY WIDELY AND TO BE A FUNCTION OF THE FREE ENERGY OF THE MOISTURE IN THE UNSATURATED SOIL. UNSATURATED MOISTURE FLOW OCCURS AS THE RESULT OF A PRESSURE GRADIENT WHICH, BECAUSE OF TEXTURAL DIFFERENCES, MAY BE QUITE INDEPENDENT OF THE MOISTURE PERCENTAGE GRADIENT. IT IS THEN EVIDENT THAT MOISTURE MOVEMENT THROUGH UNSATURATED MATERIALS IS LARGELY A FUNCTION OF THE FREE ENERGY OF THE WATER IN THE SOIL RATHER THAN OF THE ACTUAL AMOUNT OF MOISTURE PRESENT.

Vol 21, pp 435-450, 8 FIG, 2 TAB, 23 REF. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved.

01490426

1942 (approximate)

Highway Research Board Proceedings

Digital/other

Atmospheric pressure; Capillarity; Darcy's law; Engineering soils; Flow; Fluid dynamics; Free energy; Geotechnical engineering; Hydraulic gradient; Moisture content; Physical properties; Saturated soils; Soil water; Soils; Tensiometers; Texture; Thermodynamics; Unsaturated soils; Water

Fluid flow

Geotechnology; Highways

TRIS, TRB

Aug 19 1994 12:00AM

• A NEW PORTABLE SPEED RECORDER AND A COMBINATION TRAFFIC COUNTER AND SPEED RECORDER
• A STUDY OF CHANGES IN PHYSICAL PROPERTIES OF PUTNAM SOIL INDUCED BY IONIC SUBSTITUTION
• ACCELERATED TESTING OF TRAFFIC ZONE PAINTS
• AN AUTOMATIC TRAFFIC SPEED RECORDER
• ANTICIPATED FUTURE DEVELOPMENT OF THE PRIMARY STATE ROAD SYSTEM IN WEST VIRGINIA
• APPLICATION OF DRIVER BEHAVIOR AND VEHICLE PERFORMANCE STUDIES
• CHECKING COFFERDAMS FOR BRIDGE PIERS
• CHEMICAL DETERMINATION OF CEMENT CONTENT OF SOIL-CEMENT MIXTURES FROM CEMENT-HARDENED BASES
• CONDITION SURVEY OF SOIL-CEMENT ROADS
• DISCUSSION ON SOIL WATER PHENOMENA
• DRIVING PRACTICE AND ITS RELATION TO HIGHWAY CAPACITY: A SYMPOSIUM
• EFFECT OF CALCIUM CHLORIDE ON READINGS OF A VOLUMETER INCLOSING PORTLAND CEMENT PASTES ON ON LINEAR CHANGES OF CONCRETES
• EFFECT OF CALCIUM CHLORIDE ON THE STRENGTH DEVELOPMENT OF CONCRETE STORED AT LOW TEMPERATURES
• FIELD AND LABORATORY INVESTIGATION ON TRAFFIC PAINTS
• FIELD INVESTIGATION FOR FLEXIBLE PAVEMENT DESIGN
• FIELD OBSERVATIONS ON EFFECTS OF JOINTS ON CRACKING AND OTHER DETERIORATION IN CONCRETE PAVEMENTS
• Highway Capacity
• HILL-CLIMBING ABILITY OF MOTOR TRUCKS
• IMPROVEMENT OF METHODS USED IN THE HIGHWAY PLANNING SURVEYS
• INFLUENCE OF BRIDGE WIDTHS ON TRANSVERSE POSITIONS OF VEHICLES
• INVESTIGATIONAL CONCRETE PAVEMENT IN MISSOURI
• INVESTIGATIONAL CONCRETE PAVEMENT IN OREGON
• KANSAS HIGHWAY PROPERTY ACCOUNTING PROCEDURES
• LOAD TESTS ON FLEXIBLE SURFACES
• MEASUREMENT OF AMPLITUDES IN PAVING CONCRETE BEING COMPACTED BY VIBRATION
• MEASURING THE LOAD SUPPORTING VALUE OF FLEXIBLE PAVEMENTS
• PASSING PRACTICES ON RURAL HIGHWAYS
• PLANNING A TRANSPORTATION SYSTEM FOR THE NATIONAL FORESTS
• PSYCHOLOGICAL FACTORS IN HIGHWAY DESIGN AND TRAFFIC CONTROL PROBLEMS: EVALUATION OF DESIGN DATA FOR CROSSOVER DISTANCES
• RELATION OF HIGHWAY DEVELOPMENT TO NATIONAL ECONOMY
• REPORT OF COMMITTEE ON HIGHWAY GUARD: TESTS AND STUDIES, 1924-1941
• REPORT OF COMMITTEE ON PERMITS FOR OVERSIZE AND OVERWEIGHT VEHICLES
• REPORT OF COMMITTEE ON ROADSIDE DEVELOPMENT
• REPORT OF SUBCOMMITTEE ON DESIGN OF NATURAL SOIL MIXTURES AND EFFECT OF ADMIXTURES OF COMMERCIAL PRODUCTS SUCH AS CRUSHED STONE, GRAVEL AND SLAG
• REPORT ON THE COMMITTEE ON TRAFFIC CONTROL AND PROTECTION AT URBAN AND RURAL SCHOOL ZONES
• SIGNIFICANCE OF SOUNDNESS TESTS OF AGGREGATES
• SOIL CONTROL IN CONSOLIDATED MAINTENANCE
• SOIL-EMULSIFIED ASPHALT AND SAND EMULSIFIED ASPHALT PAVEMENT
• STABILIZATION CONTROL ON THE WASHINGTON NATIONAL AIRPORT
• STAGGERED HOURS FOR WARTIME
• STUDY OF STRESS DISTRIBUTION IN SOILS FROM 1920-1940
• TEMPERATURE AND MOISTURE VARIATIONS IN CONCRETE PAVEMENTS
• THE ECONOMICS OF HIGHWAY ALIGNMENT DESIGN
• THE FUTURE DEVELOPMENT OF HIGHWAY TRANSPORTATION
• THE UNCONFINED COMPRESSIVE STRENGTH OF SOIL-CEMENT MIXTURES
• VIBRATION IN PLACEMENT OF CONCRETE
• WHEEL LOAD STRESS DISTRIBUTION THROUGH FLEXIBLE TYPE PAVEMENTS