Hydrostatics in swelling soils and soil suspensions: unification of concepts

TLDR: In this article, the authors examined the effect of different conditions on the performance of a VERTICAL in SWELLING SOIL (or SOIL PASTE) and found that, in SUCH systems, the MOISTURE POTENTIAL is MINUS the COLLOID OSMOTIC PRESSURE.

Abstract: THE TOTAL POTENTIAL GOVERNING VERTICAL EQUILIBRIUM AND MOVEMENT OF WATER IN A SWELLING SOIL (OR SOIL PASTE) IS MADE UP OF THREE COMPONENTS: (1) THE MOISTURE POTENTIAL, (2) THE GRAVITATIONAL POTENTIAL, (3) THE OVERBURDEN POTENTIAL, IN SATURATED SYSTEMS THE MOISTURE IS THE CONSEQUENCE OF THE LOCAL JUXTAPOSITION OF WATER AND SOIL PARTICLES AND IS A FUNCTION OF THE MOISTURE RATIO. THE OVERBURDEN POTENTIAL IS GLOBAL IN CHARACTER, ITS VALUE DEPENDING ON THE TOTAL WEIGHT OF SOIL AND WATER ABOVE THE POINT CONSIDERED AND ON ANY SURFACE LOAD. THE QUESTION IS EXAMINED AS TO WHETHER THESE VARIOUS CONCEPTS CARRY OVER TO DILUTE SOIL SUSPENSIONS SUBJECT TO GRAVITY AND BROWNIAN MOTION (DOUBLE LAYER EFFECTS BEING NEGLIGIBLE). IT IS SHOWN THAT THEY DO, AND THAT, IN SUCH SYSTEMS, THE MOISTURE POTENTIAL IS MINUS THE COLLOID OSMOTIC PRESSURE. THE MOISTURE POTENTIAL IS A UNIQUE FUNTION OF THE MOISTURE RATIO FOR: (1) ANY SUSPENSION UNDER EQUILIBRIUM CONDITIONS, AND (2) A SUSPENSION OF UNIFORM PARTICLES UNDER EITHER NON-EQUILIBRIUM OR EQUILIBRIUM CONDITIONS. THE EQUILIBRIUM OF A SYSTEM CONSISTING OF A SWELLING SOIL AND A SOIL SUSPENSION IS AMENABLE TO UNIFIED TREATMENT ALONG LINES PREVIOUSLY DEVELOPED FOR THE ANALYSIS OF EQUILIBRIUM IN THE VERTICAL IN SWELLING SOILS. THIS UNIFICATION OF CONCEPTS ILLUMINATES THE DISTINCTION BETWEEN THE BEHAVIOR OF NON-SWELLING SOILS AND SWELLING SOILS IN THE LIMIT AS THE MOISTURE APPROACHES 0. PONDING OF WATER OVER A SATURATED NON-SWELLING SOIL (NO UNDERDRAINAGE) PRRODUCES NO CHANGE IN THE MOISTURE RATIO, BUT CAUSES AN INCREASE OF THE TOTAL POTENTIAL BY INCREASING THE PRESSURE POTENTIAL. THE ADDITION OF WATER TO A SATURATED SWELLING SOIL (NO UNDERDRAINAGE) INCREASES THE MOISTURE RATIO AND MOISTURE POTENTIAL EVERYWHERE IN THE SOIL. THE MOISTURE POTENTIAL REMAINS NEGATIVE BOTH IN THE SOIL AND IN THE SUSPENSION OVER IT, HOWEVER, SO THAT MOST OF THE INCREASE OF TOTAL POTENTIAL OCCURS AS AN INCREASE IN THE OVERBURDEN POTENTIAL.