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This paper summarizes results of laboratory investigations performed to quantify the influence of diagenesis (or aging processes) on the peak shear strength and dilatancy of an uncemented Pleistocene age sand sampled near Charleston, South Carolina. Drained triaxial compression tests were performed on high-quality intact specimens retrieved using the in situ freezing and sampling method, and on remolded specimens prepared with matching densities. The stress-strain behavior of intact specimens is accompanied by dilation and a peak shear value, whereas remolded specimens generally contracted throughout shearing. An age-dilatancy term is added to a dilatancy index equation to account for the difference between intact and remolded peak friction angles. The resulting equation suggests that dilatancies due to age and density are suppressed with increasing confining pressure. A profile of peak friction angle with depth is established from the results and compared with estimates from empirical relationships. [ABSTRACT FROM AUTHOR]

Liquefaction potential of four Pleistocene beach sand deposits in the Greater Charleston area, South Carolina, is assessed. The assessment is based on a review of 51 sites of conspicuous craterlets and horizontal ground displacement that occurred in beach sand deposits during the 1886 Charleston earthquake and an analysis of 82 seismic cone penetration tests with pore-pressure measurements. Of the 51 ground failure sites, 23 are associated with the Ten Mile Hill beds; 13 with the Wando Formation; 13 with the Silver Bluff terrace and younger deposits that lie adjacent to the harbor, rivers, and creeks; and two with the Ladson Formation. Liquefaction potential is analyzed using the seismic cone data with and without correction for age-related processes (diagenesis) and then expressed in terms of the liquefaction potential index (LPI). Probability curves are developed from the LPI calculations for different earthquake ground-shaking parameters. The probability curves for the Wando Formation overpredict liquefaction potential when no corrections for diagenesis are made. When corrections for diagenesis are made, the probability curves for all four sands generally agree with the observed field behavior. [ABSTRACT FROM AUTHOR]

Abstract: Liquefaction potential of aged soil deposits in Mount Pleasant, South Carolina, based on the 1886 Charleston earthquake is characterized in this paper. The characterization involves reviewing available first-hand accounts of 1886 ground behavior, analyzing cone penetration test (CPT) and shear wave velocity data, and correlating the results with geology. Careful review of the first-hand accounts reveals that nearly all cases of surface effects of liquefaction can be associated with the younger sand deposits that lie adjacent to the harbor, rivers, and creeks. Only one documented case of minimal surface effect of liquefaction can be definitely associated with the older sand deposits of the 100,000-year-old Wando Formation. Ratios of measured-to-estimated shear wave velocity indicate that the younger sand deposits and the older sand deposits have measured velocities that are 9% and 38%, respectively, greater than 6-year-old sand deposits with the same CPT tip resistance. Liquefaction potential is expressed in terms of the liquefaction potential index (LPI) proposed by Iwasaki and others. LPI values for the Wando sands computed from the CPT profiles are incorrectly high, if no age corrections are applied. If age corrections are applied, computed LPI values match well the observed field behavior in both the younger sands and the older sands. The results are combined with a 1:24,000 scale geologic map to produce a liquefaction potential map of Mount Pleasant. The findings of this study agree remarkably well with a previous liquefaction potential study of aged soil deposits on Charleston peninsula. [Copyright &y& Elsevier]

Data from over 30 sites in 5 countries are analyzed to develop updated factors for correcting liquefaction resistance for aged sand deposits. Results of cyclic laboratory tests on relatively undisturbed and reconstituted specimens suggest an increase in the correction factors of 0.12 per log cycle of time and an average reference age of 2 days for the reconstitute specimens. Laboratory and field test results combined with cyclic resistance ratio (CRR) charts suggest an increase in the correction factors of 0.13 per log cycle of time and an average reference age of 23 years. A reference age of 23 years seems appropriate for the commonly used CRR charts derived from field liquefaction and no liquefaction case history data. Because age of natural deposits is often difficult to accurately determine, a relationship between measured to estimated shear-wave velocity ratio (MEVR) and liquefaction resistance correction factor is also derived directly from the compiled data. This new MEVR-liquefaction resistance correction factor relationship is not as sensitive to MEVR as in the relationship derived indirectly in a previous paper. [ABSTRACT FROM AUTHOR]

Factors for correcting liquefaction resistance for aged sands using ratios of measured to estimated shear-wave velocity (MEVR) are derived in this paper. Estimated values of shear-wave velocity (VS) are computed for 91 penetration resistance-VS data pairs using previously published relationships. Linear regression is performed on values of MEVR and corresponding average age. Age of the sand layer is taken as the time between VS measurements and initial deposition or last critical disturbance. It is found that MEVR increases by a factor of about 0.08 per log cycle of time, and time equals about 6 years on average when MEVR equals 1 for the recommended penetration resistance-VS relationships. The resulting regression equation is combined with the strength gain equation reported by Hayati et al. 2008 in “Proc., Geotechnical Earthquake Engineering and Soil Dynamics IV,” to produce a MEVR versus deposit resistance correction relationship. This new corrective relationship is applied to create liquefaction resistance curves based on VS, standard penetration test blow count, and cone tip resistance for sands of various ages (or MEVRs). Because age of natural soil deposits is usually difficult to accurately determine, MEVR appears to be a promising alternative. [ABSTRACT FROM AUTHOR]

A review of the current state of the art in the assessment of aging effects on soil liquefaction is presented in this paper. The review includes a summary of several field case histories indicating greater resistance to liquefaction in aged soils than in young uncemented soils during earthquakes, a discussion of the mechanisms that increase liquefaction resistance with time, an evaluation of proposed methods for quantifying the influence of aging processes (or diagenesis) on liquefaction resistance (K DR), and an evaluation of proposed predictor variables for K DR. The published literature indicates physical diagenetic processes tend to dominate the nature of interactions at the grain-to-grain contacts of sand deposits in the absence of sufficient cementing agents, while chemical processes tend to dominate where sufficient cementing agents are present. Variables proposed for predicting K DR include: the time since deposition or last critical disturbance; the ratio of measured to estimated small-strain shear wave velocity (MEVR); the ratio of small-strain shear modulus to cone tip resistance (G max /q c); the adjusted G max /q c (K G); and the ratio of measured to estimated adjusted G max /q c (MEK G). It is shown that MEVR , G max /q c , K G and MEK G are all ratios of measured to estimated or reference shear wave velocity. MEVR and G max /q c are slightly more robust predictors (i.e., regression equations with higher coefficient of regression and lower root mean square error) of K DR than K G and MEK G. Time is the least robust predictor of K DR. • Aging changes the soil's structure and liquefaction resistance with time. • Aging can be predicted using time, MEVR , G max /q c , K G or MEK G. • MEVR , G max /q c , K G or MEK G are ratios of measured to estimated or reference velocity. • MEVR and G max /q c are slightly more robust predictors of aging. • Time is the least robust predictor of aging. [ABSTRACT FROM AUTHOR]