Soils--Testing

A comprehensive laboratory investigation was conducted to evaluate the primary and secondary compression behavior of undisturbed organic silts and peats obtained from 11 locations along SR 15/US 98 in Palm Beach County, Florida. A total of 43 consolidation tests were performed. The primary objectives were as follows: (i) to conduct a series of standard consolidation tests to determine the Compression Index, Cc, and the Coefficient of Consolidation, cnu; (ii) to determine the Secondary Compression Index, Calpha, at stress levels (sigmanu'/sigmap') ranging from 0.30 to 1.15; and (iii) to employ the well-known Time-Stress-Compressibility concept to establish a unique relationship between C alpha and Cc. It was found that for all practical purposes, the Calpha/C c ratio at any stress level is 0.03, which is consistent with the values reported in the literature for similar soils. A constant Calpha/Cc ratio provides an approximation of Calpha once C c is determined from a standard consolidation test, and without the need of ongoing laboratory testing to predict long-term settlement.

To better characterize the accumulation of permanent deformation in a granular material, 40 Consolidated Drained (CD) triaxial tests (14 static and 26 cyclic) were performed under various stress conditions. A Digital Image Correlation (DIC) technique was utilized in some Repeated Load Triaxial (RLT) tests to measure global and localized strains visually in a non-contact manner. Additionally, the experimentally determined resilient material properties were used in a finite element based pavement modeling software called MICH-PAVE. Under cyclic loading, the permanent strain accumulation was found to obey the relationship of the form epsilonp =aNb, and the Resilient Modulus was used to develop the nonlinear K-theta model for granular materials. The observed/measured permanent strains using DIC/LVDT techniques compared favorably with the values obtained by the finite element simulation, and the evaluation of granular material by multiple methods seems promising for improved pavement design.