Experimental Studies On Shrinkage Induced Pressure Measurements Of Four Expansive Soils

Civil structures were damaged by expansive soils due to its large volumetric changes caused by moisture fluctuations. During wet and dry season, the ground heaves up and also shrinks noticeably. The significant amount of curling pressure which is induced by soil shrinkage could cause severe damages to the infrastructure. Especially in the eastern and central Texas, pavements encounter severe cracking and premature loss of serviceability. The maintenance costs, in some cases, are greater than the initial construction costs. Residential dwell structures built on problematic expansive soils often become distressed due to volume changes associated with seasonal moisture content variations. This thesis research was an attempt to develop a new technique in order to measure the shrinkage pressure inherently induced inside the matrix of expansive clays. This test is termed as Shrinkage Induced Pressure (SIP) test. Laboratory investigations were conducted on soils from different locations, Fort Worth, Dallas, and Paris. These soils are considered as highly plastic and expansive clays. Also, another soil from El Paso which is low expansive was also used. Laboratory tests were first conducted included basic soil properties, chemical test and engineering soil tests. Laboratory test results showed that soil from Paris site have more shrinkage potential related to the highest value of volumetric shrinkage strain at OMC and Wet of OMC condition. Soils from Fort Worth, Dallas, and El Paso show moderate to lower shrinkage strain potentials, respectively. Comparisons among the results at different orientation and moisture content conditions showed that SIP results especially at LL+10% and with the force sensor (FS) in horizontal orientation provided both repeatable and reliable results. Reliability of the measurement was assessed by evaluating their closeness with the Indirect Tensile Strength (IDT) test results. SIP results showed a good correlation with percents of Montmorillonite in soils which was evaluated using cationic exchange capacity (CEC) values. Volumetric shrinkage and swell behaviors showed similar patterns as SIP data. Overall, this thesis research showed the potential of the SIP measurements using FS can provide repeatable and reliable shrinkage pressure measurements of soils samples prepared at high moisture contents.