Acquisition and Development of Equipment for Unsaturated Soil Research

University Of Oklahoma Norman Campus, Norman OK

Investigators

Abstract

The School of Civil Engineering and Environmental Science (CEES) at the University of Oklahoma (OU) will purchase and develop state-of-the-art equipment for integrated research/education in problems associated with unsaturated soil behavior. Within the civil engineering community, behavior of partially saturated near-surface soils is receiving intense research interest. Slope failures, embankment settlement, foundation heave due to expansive clays, pavement subgrade performance, chemical spills, and vadose zone remediation, are just a few examples of prevalent engineering problems whose solution depends on understanding unsaturated soil behavior. The CEES is poised to be a leader in this field due to the expertise of the faculty and the compelling research already established in unsaturated soil mechanics. Equipment obtained via NSF MRI funding will enable researchers to examine in-depth, comprehend, and define unsaturated soil behavior in ways not currently possible. Five pieces of equipment for testing unsaturated soils will be acquired and developed: 1) A direct shear test device will be purchased and a unique test cell/apparatus will be constructed for control and/or measurement of pore-air and pore-water pressure. The test cell will accommodate testing of soil-to-soil or soil-to-construction material interfaces. 2) A custom made hollow cylinder apparatus used for examining stress-strain behavior of soil will be purchased and will provide complete freedom on the stress and strain paths applied to the soil. The apparatus allows a hollow cylinder test specimen to be subjected to axial force and torque, and to different internal and external cell pressures. In addition, pore air and pore water pressures can be controlled. These forces and pressures are controlled independently from a PC. Accordingly, it is possible to control the magnitude and direction of the three principal stresses. Data acquisition will be included, and a pressure control panel will be fabricated. 3) An oedometer will be purchased and a test cell will be constructed for control and/or measurement of pore-air and pore-water pressure. Data acquisition will be acquired and a pressure control panel will be fabricated. The equipment will allow for the determination of fundamental one-dimensional compression properties of unsaturated soils. 4) A cubical device, currently owned by CEES, permits independent control of total normal stress applied in the principal stress directions during cubical triaxial testing of unsaturated soil. Modifications will allow measurement of pore air and pore water pressure, and automated application of cyclic loads, in addition to measurement of displacements. 5) A parallel miniature pressure cell system will be constructed for rapid, detailed measurement of air/water and organic-liquid/water capillary pressure-saturation relationships and relative permeabilities in soils. The system will be comprised of eight custom-built miniature pressure cells operated in parallel, and a computerized control system for automated operation and data acquisition. Equipment obtained through the MRI grant will greatly enhance current research capabilities and allow CEES to become a preeminent research institution in the area of unsaturated soil behavior. Currently, there is no unique center of this type in the United States, and thus the new facilities will have broad appeal. It is fitting that OU becomes the location of a preeminent research center for unsaturated soils, particularly in light of the numerous unsaturated soil problems that plague Oklahoma and other surrounding states such as Texas and Colorado.