Identifying late Quaternary coastal deposits in Kyonggi Bay, Korea, by their geotechnical properties |
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| Authors: | Kyungsik Choi Ju Hyong Kim |
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| Institution: | (1) New Ventures Department, Overseas E&P, Korea National Oil Corporation, 1588-14 Gwanyang-dong, Dongan-gu, 431-711 Anyang, South Korea;(2) Geotechnical Engineering Research Department, Korea Institute of Construction Technology, 411-712 Goyang, South Korea |
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| Abstract: | Based on cone penetration tests with pore pressure measurements (CPTUs) and standard penetration tests (SPTs), the geotechnical properties of five lithostratigraphic units were determined during the construction of Incheon international airport on reclaimed macrotidal flats in Kyonggi Bay, Korea. Two late Pleistocene non-marine units (unit V and unit IV) display largest N values (cf. number of blows required to achieve a standard penetration), reflecting coarse-grained and overconsolidated sediments. Tidal channel and tidal flat facies (unit IIIb) consist of unweathered late Pleistocene tidal sand and mud. The tidal channel facies is characterized by upward-decreasing cone resistance (q
t) and sleeve friction (f
s) with negative pore pressures (u
bt), reflecting a fining-upward textural trend. The tidal flat facies, by contrast, is represented by uniformly low q
t and f
s values with high friction ratios (FRs), suggesting homogeneous muddy deposits. Two overconsolidated units, a weathered late Pleistocene tidal mud (unit IIIa) and an early Holocene organic-rich non-marine mud (unit II), are characterized by high q
t, f
s, FRs and N values, unit IIIa being much more consolidated than unit II. Holocene tidal sands and muds (unit I) show the smallest q
t and f
s values with positive u
bt. These are slightly more consolidated than the tidal flat facies of unit IIIb. Two unconformable boundaries (a sequence boundary and a transgressive surface) have also been identified on some CPTU and SPT profiles. The boundaries are indicated by gradual but sharp increases in q
t, f
s and N values with an abrupt drop of u
bt, which indicates the contact between two units showing contrasting rigidity. The regional pattern produced by the unconformable boundaries indicates the presence of late Pleistocene valleys which pass through the middle of study area. The location of the valleys seems to be controlled by the antecedent basement morphology. |
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