The coefficient of earth pressure at rest

An investigation of the coefficient of earth pressure at rest has been conducted with the objective of developing a better understanding about the behavior of this coefficient with consolidation, aging, overconsolidation, densification, and preshearing.The literature review carried out on the subject included the evaluation of insitu devices that are used to measure insitu effective horizontal pressure, in terms of the merits and demerits of each device. The process of densification of sands was also critically reviewed with the objective of correlating the results from laboratory densified sand specimens to insitu densified sand deposits.Information existing on theoretical methods and methods that are applied to laterally constrained (LC) compression test results for evaluating the insitu coefficient of earth pressure at rest was gathered along with information on the effect of preshearing on this coefficient. This information was applied to results obtained from the LC compression tests carried out on undisturbed specimens of eleven soft clay deposits. The LC compression tests were carried out either in the triaxial apparatus using Bishop's (1958) method or in an instrumented oedometer ring. The instrumented oedometer ring was specifically designed for this study and horizontal stress during LC compression test is measured in this device. Zeevaert's method, Schmidt's equation, and Mesri and Castro's method were applied to the test results for evaluation of in situ coefficient of earth pressure at rest for the clays tested. A comparison of results from these methods was also made. Secondary compression allowed during these tests made possible the evaluation of the effect of aging on the coefficient of earth pressure at rest. Special tests were conducted where specimens were first subjected to active or passive shear condition and then LC condition was imposed. The behavior of the presheared specimen was then observed either with time or with compression loading. From the evaluation of data from these tests, formulas were derived which can predict the coefficient of earth pressure at rest in soils which have been subjected to active or passive shear in their geologic history.U of I OnlyETDs are only available to UIUC Users without author permissio