Publication Date:
2015-08-01
Description:
We develop empirical predictive equations for shear-wave velocity ( V S ) conditional on standard penetration test resistance ( N -value) and other explanatory variables using data sets from Japan. The V S and N data sets are from the Kyoshin network (K-NET), which include 16,845 collocated measurements of V S and N at 1102 sites. We begin with baseline equations considering soil type and overburden pressure in addition to N . For coarse-grained soils, V S is more sensitive to overburden pressure than to N , whereas for fine-grained soils, V S is more sensitive to N . We find that residuals (difference between data and model) for a given borehole tend to be correlated (e.g., samples within a boring are consistently high or low); hence, we use mixed-effects regression to compute a quantity akin to an average borehole residual referred to as the between-boring residual. Sites associated with older (pre-Holocene, 〉10,000 yrs) geology tend to have null to slightly positive between-boring residuals, whereas these residuals are negative for more recent materials. Accordingly, we provide adjustments to the baseline equations conditional on geologic condition. Between-boring residuals exhibit spatial correlations; however, due to lack of knowledge as to the cause of these correlations, we do not recommend such effects for inclusion in the model. When applied to predict the time-averaged V S in the upper 30 m ( V S 30 ) in the absence of direct measurement, the proposed equations provide significantly better accuracy than widely used local geomorphology-based proxies (0.26 versus 0.42 of standard deviation of the natural log of residuals). This suggests that penetration resistance data can improve predictions of V S 30 compared with geomorphology-based proxies alone, when site-specific V S measurements are unavailable.
Print ISSN:
0037-1106
Electronic ISSN:
1943-3573
Topics:
Geosciences
,
Physics
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