Dynamic Periods and Building Damage at Charleston, South Carolina during the 1886 Earthquake

2008 ◽  
Vol 24 (4) ◽  
pp. 867-888 ◽  
Author(s):  
Cedric D. Fairbanks ◽  
Ronald D. Andrus ◽  
William M. Camp ◽  
William B. Wright
Keyword(s):  
South Carolina ◽  
Shear Wave Velocity ◽  
Response Spectra ◽  
Small Strain ◽  
Spectral Ratios ◽  
Quaternary Sediments ◽  
Quaternary Deposits ◽  
Geologic Map ◽  
Velocity Information ◽  
Isopach Map

Fundamental dynamic periods of Quaternary deposits beneath the peninsula of Charleston, South Carolina, are characterized spatially using an updated isopach map of Quaternary thickness, characteristic small-strain shear wave velocity information, a 1:24,000 geologic map, and a simple approximating equation. The updated isopach map is developed from subsurface information from 266 investigation sites. Estimates of fundamental periods for the Quaternary sediments primarily range between 0.3 and 0.7 s. These periods are lower end estimates of actual ground periods, based on a comparison with modeled response-spectra ratios. Estimates of fundamental periods range from 0.1 to 0.4 s for over 95% of the buildings present in 1886. Thus, the overlap between the range of building periods and the range in periods corresponding to high spectral ratios is not great. This finding agrees with the observation of Marciano and Elton that damage was independent (or only slightly dependent) of building height.

Recovery of Small-Strain Stiffness Following Blast-Induced Liquefaction Based on Shear Wave Velocity Measurements

2020 ◽  
Author(s):  
Siavash Mahvelati ◽  
Joseph Thomas Coe ◽  
Armin W. Stuedlein ◽  
Philip Asabere ◽  
Tygh Gianella ◽  
...  
Keyword(s):  
South Carolina ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Small Strain ◽  
Rate Variation ◽  
Time Rate ◽  
Small Strain Stiffness ◽  
Soil Fabric

Changes in soil fabric following liquefaction have been studied using various in-situ methods, and often return inconclusive or conflicting observations. The time-rate variation of stiffness, when observed, is usually not evaluated over significant periods of time, limiting investigations about aging in post-liquefaction regain of stiffness. Even more uncommon is the application of geophysical techniques to evaluate changes in shear wave velocity (VS) as a proxy for small-strain stiffness. This study uses controlled blasting to examine long-term post-liquefaction regain of stiffness following multiple blast events. The Multichannel Analysis of Surface Waves (MASW) technique was used to observe changes in VS of aged deposits at a test site in South Carolina. Blast-induced liquefaction of the target liquefiable layer resulted in significant reduction to its initial small-strain stiffness owing to the destruction of the aged soil fabric. The time-rate variation in VS indicated that the initial small-strain stiffness was not re-established over many months following liquefaction. Following a second blast event, the small-strain stiffness reduced again, but recovered more quickly, similar to previously reported observations of young sand deposits. This study provides a significant basis for interpreting in-situ body and surface wave measurements of aged and young sand deposits densified using blast liquefaction.

Generalized geologic map of the Charleston, South Carolina, area

1982 ◽  
Author(s):  
Lucy McCartan ◽  
E.M. Lemon ◽  
R.E. Weems
Keyword(s):  
South Carolina ◽  
Geologic Map

Measurement of small-strain shear modulus Gmax of dry and saturated sands by bender element, resonant column, and torsional shear tests

2008 ◽  
Vol 45 (10) ◽  
pp. 1426-1438 ◽  
Author(s):  
Jun-Ung Youn ◽  
Yun-Wook Choo ◽  
Dong-Soo Kim
Keyword(s):  
Shear Modulus ◽  
Shear Wave ◽  
Shear Wave Velocity ◽  
Small Strain ◽  
Resonant Column ◽  
Test Results ◽  
Bender Element ◽  
Small Strain Shear Modulus ◽  
Torsional Shear ◽  
Saturated Sands

The bender element method is an experimental technique used to determine the small-strain shear modulus (Gmax) of a soil by measuring the velocity of shear wave propagation through a sample. Bender elements have been applied as versatile transducers to measure the Gmax of wet and dry soils in various laboratory apparatuses. However, certain aspects of the bender element method have yet to be clearly specified because of uncertainties in determining travel time. In this paper, the bender element (BE), resonant column (RC), and torsional shear (TS) tests were performed on the same specimens using the modified Stokoe-type RC and TS testing equipment. Two clean sands, Toyoura and silica sands, were tested at various densities and mean effective stresses under dry and saturated conditions. Based on the test results, methods of determining travel time in BE tests were evaluated by comparing the results of RC, TS, and BE tests. Also, methods to evaluate Gmax of saturated sands from the shear-wave velocity (Vs) obtained by RC and BE tests were investigated by comparing the three sets of test results. Biot’s theory on frequency dependence of shear-wave velocity was adopted to consider dispersion of a shear wave in saturated conditions. The results of this study suggest that the total mass density, which is commonly used to convert Gmax from the measured Vs in saturated soils, should not be used to convert Vs to Gmax when the frequency of excitation is 10% greater than the characteristic frequency (fc) of the soil.

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