Geotechnical characterisation of Busan clay

2013

The purpose of this study is to investigate effects of sedimentary environment (freshwater and marine deposits) on geotechnical properties for Kanto lowland clays. Freshwater and marine sediments were used to perform standard consolidation tests, undrained triaxial compression tests, and unconfined compression test. Pore-water compositions were also measured for the sediments. As results, higher compression index, higher sensitivity, and lower shear strength ratio were observed for the marine sediments as compared to those for the freshwater sediments. In addition, the measurements of pore-water compositions revealed that the sensitivity values were well related to the proportion of monovalent cations, especially for the sediments with plastic index of less than 30.

Despite a number of geotechnical investigations that have been carried out on soft clay deposits at Pusan,South Korea, the local practicing engineers have been unable to deduce successfully the geotechnical properties of the clays due to their spatial variation and influence from geological depositional environments. In the area, clay deposits, so-called Pusan clays, are unusually thick, varying from 20m to 70 m in thickness. For this study, reclaimed land along the Nakdong river deltaic plain, which is called as “Hwajeon site” has been considered and an attempt has been made to characterize the Pusan clay in terms of both geotechnical and geological, furthermore dependency of geotechnical properties on geological depositional environment was also studied. In this study, a comprehensive geotechnical investigation was carried out with sophisticated sampling techniques, in situ and laboratory tests as well as geological analyses at an additional three locations. As a result of the investigations, it was found that depositional environments are closely related to the relative changes in sea level and have different features depending on location and depth. The clays consist of soft and stiff clays in the upper and the lower layers, respectively, which are classified as normally consolidated and cemented clay. Moreover, most of the geotechnical properties undergo changes due to their depositional environment. Keywords: Pusan Clays, reclamation land, Characterization, geological depositional environment, geotechnical properties.

Soils and Foundations, 2015

An engineering geological study was undertaken to determine the geotechnical properties and mineralogy of Singapore marine clay at Changi in the Republic of Singapore. This soft soil is a quartenary deposit that lies within submarine valleys cut in an old alluvium formation. The marine clay comprises a soft upper marine clay layer overlying a stiffer lower marine clay layer. An intermediate stiff clay layer is sandwiched between these two marine clay layers; it is believed to be the dessicated crust of the lower marine clay layer. In the present study, morphological and mineralogical observations of Singapore clay were taken by scanning electron microscopy, X-ray diffraction and photographic identification. The geotechnical investigation included physical, compression, permeability and field vane shear tests. The upper marine clay was found to be soft with undrained shear strength values ranging from 10 to 30 kPa, while the lower marine clay was found to have undrained shear strength values from 30 to 60 kPa. The sensitivity of the marine clay at Changi varied from 3 to 8 and is described as highly sensitive marine clay. The upper clay layer had a coefficient of consolidation of 0.47-0.6 m 2 /year due to the vertical flow (c v ) and a coefficient of consolidation of 2-3 m 2 /year due to the horizontal flow (c h ). The lower marine clay had a c v of 0.8-1.5 m 2 /year and a c h of 3-5 m 2 /year, while the intermediate stiff clay had a c v of 1-4.5 m 2 /year and a c h of 5-10 m 2 /year. The primary clay mineral was kaolinite, followed by smectite and mica. With this high kaolinite content, the activity of the Singapore marine clay was found to be low at approximately 0.5-1.3 and classified as inactive to active clay. With reference to the intrinsic state line, natural Singapore clay (upper, intermediate and lower layers) has been classified as structured clay and is in a meta-stable state. The compression behaviour can be modelled by the Intrinsic State Line and the destructuring framework. The predicted and the measured compression curves were comparable for various depths. The successful modelling of compression curves will be useful for settlement calculations and for further research on the development of a constitutive model for Singapore marine clay.

The mineralogy, geochemistry and geotechnical properties of clay samples in Lianyungang, China are presented. The correlations of depositional history, depositional environmental and geotechnical properties are discussed. A series of X-ray diffraction tests show that the principal clay minerals of the soil are illitesmectite mixed-layer mineral and illite. The geochemistry investigation results indicate that the pore water of the Lianyungang marine clay is dominant by sodium. The pH of the soils varies in the range of 7.8 to 8.9. The depositional environment is oxidation condition. The correlations of the geochemistry with the geotechnical properties are examined by the statistic analysis.

Engineering Geology, 2011

The aim of the study was to characterize a variety of sedimentary facies from the Mekong River delta (MRD) and to determine their geotechnical properties. The paper furthermore discusses the influences of sedimentary environment and conditions on geotechnical properties of the sedimentary facies. A core at the Vinhlong province, MRD, sufficiently presented the sedimentary facies of the area. Eight successive facies were identified based upon sedimentary properties. Characteristics of the unit showed development of sedimentary facies. Each sedimentary facies was formed under a different environment and revealed typical geotechnical properties. Estuarine channel, estuarine marine, delta front-mouth bar, and sub-to inter-tidal flat facies were formed under strong hydrodynamic conditions. The sediments are from clay to coarse sand and even pebbles, and the sedimentary structures are plentiful, such as intercalated clay, silt beddings and fine to coarse sand beddings with very different thicknesses. Strengths of these sedimentary facies vary significantly, which can be observed by cone penetration test (CPTU) results, but not by standard penetration test (SPT). The normalized values from CPTU show saw-tooth graphs with large variations, especially delta front-mouth bar and sub-to inter-tidal flat facies at shallower depth. The soil-behavior-types determined from the normalized values are plentiful from cohesionless to cohesive soils. As an example, an estuarine channel facies experiencing a large consolidation pressure, in relatively long-time (over 9920 yr BP) has geotechnical properties with heavily overconsolidated conditions and high strength. On the other hand, marsh, open bay, pro-delta and March/flood plain facies, which formed under relatively low hydrodynamic conditions, have simple and homogenous sedimentary properties. The sediments are commonly silt and clay, and sedimentary structures are very faint interbedded clay and silt laminae, and rarely very fine sand laminae. Strengths of these sedimentary facies increase linearly with depth, the normalized values are all rather constant with depth, and their soil behavior-type is only normally consolidated clays from CPTU results. It could be said that the particular sedimentary conditions in the late Pleistocene-Holocene deposits of MRD can be reasonably estimated by the CPTU test.

Egyptian Journal of Pure and Applied Science, 2022

Establishment of any engineering structure on a compressible clay leads to settlement and/or failure through this clay. The amount of this settlement is controlled mainly by the compressibility parameters, while the failure by the undrained strength. The measuring of compressibility parameters and undrained strength are expensive, cumbersome, and time-consuming; therefore several attempts have been made to predict these geotechnical parameters by using simple, cheap, and time-saving index properties of the soil. In this study, the performance of applying empirical equations for the estimation of these critical geotechnical parameters was assessed by using a database including 551 undisturbed samples of the Nile Delta clay. The regression analysis results depict statistically moderate to strong correlations exist between both compression index and recompression index and the bulk density, Atterberg limits, initial void ratio, and effective overburden pressure. The precompression stress, overconsolidation ratio, and undrained shear strength parameters have no remarkable correlations with these index properties, except the effective overburden pressure parameter that has moderate to strong correlations with these properties. The compressibility and strength parameters depend on the in-situ effective stress, stress during geological history, diagenesis and cementation process, mineralogy, microstructure, and texture of clay, therefore they provide meaningful relationships. The developed empirical equations in this study, which derived from various linear and multi-variables regression models, are reliable and capable to predict the geotechnical design parameters with high prediction performance.

KSCE Journal of Civil Engineering, 2012

The current paper presents an estimation of the undrained shear strength (s u) of Busan clay through a comparison of the results of field vane and laboratory shear test results at two sites in the Nakdong River Delta. The results indicate that because of fabric effects in the clay, determining the effective overburden stress (σ v0 ') and the field vane strength (s u,FV) based on the corrected cone resistance (q t) is effective. The ratio s u,FV /σ v0 ' varied with the depositional units, independent of the plasticity index (I p). In comparison to s u,FV , combined shear strengths obtained from the consolidated-undrained compression and extension triaxial tests were slightly smaller and occasionally scattered because of the effects of sample disturbance. The laboratory shear strengths rely on the strain rate, regardless of the I p. The correction factors using two different approaches were larger than those of the existing methods. For practical applications, the q t-based corrected vane strengths with the correction factor (µ) are thus recommended as the mobilized undrained shear strength of the clay (i.e., µs u,FV /σ v0 ' of 0.23), which is similar to the corrected value of the combined shear strengths for all depths.

IOP Conference Series: Earth and Environmental Science, 2019

Northern Jakarta coastal area is formed by some marine clay layers which has high compression as sedimentary soil. Land subsidence can occur due to several factors, such as load of building, excessive groundwater exploitation and normally consolidation process. Consolidation is a process of soil compacting due to the compression. The compression process of the soil occurs when soil receives the load from its above structure which makes a reduction of pore water pressure. Then, the dissipation of groundwater is followed by compaction of the volume of soil. A significant level of land subsidence in the coastal areas of Jakarta especially in Kamal Muara can lead to failure of building structures built on sedimentary clay soils. Therefore, research on the level of compression of sedimentary soils in the coastal areas of Jakarta needs to be done. This research is conducting by laboratory tests on UDS (undisturbed) soil samples taken by drilling a depth 50 meter point. The method used is the conso compression index lidation test for further analysis of the parameters of Pc, Cr, and OCR. Testing result shows the level of marine clay soil of coastal sediment clay in Kamal Muara North Jakarta is under consolidation.

Engineering Geology, 2011

The geotechnical characteristics of Ulleung Basin sediments are explored using depressurized samples obtained at 2100 m water depth and 110 m below the sea floor. Geotechnical index tests, X-ray diffraction, and SEM images were obtained to identify the governing sediment parameters, chemical composition and mineralogy. We use an instrumented multi-sensor oedometer cell to determine the small-strain stiffness, zero-lateral strain compressibility and electromagnetic properties, and a triaxial device to measure shear strength. SEM images show a sediment structure dominated by microfossils, with some clay minerals that include kaolinite, illite, and chlorite. The preponderant presence of microfossils determines the high porosity of these sediments, defines their microstructure, and governs all macroscale properties. The shear wave velocity increases as the vertical effective stress increases; on the other hand, porosity, permittivity, electrical conductivity, and hydraulic conductivity decrease with increasing confinement. All these parameters exhibit a bi-linear response with effective vertical stress due to the crushable nature of microfossils. Well-established empirical correlations used to evaluate engineering parameters do not apply for these diatomaceous sediments which exhibit higher compressibility than anticipated based on correlations with index properties. Settlements will be particularly important if gas production is attempted using depressurization because this approach will cause both hydrate dissociation and increase in effective stress.

Geotechnical and Geological Engineering, 2008

Singapore marine clay at Changi is a quartenary deposit that lies within valleys cut in the Old Alluvium. It is locally known as Kallang formation. The pre-reclamation site characterization and laboratory testing was carried out by conducting marine sampling boreholes, in situ dissipation tests and field vane test. In situ dissipation tests were conducted with the piezocone, flat dilatometer, selfboring pressuremeter and BAT permeameter. The purpose of the site characterization was to determine the consolidation characteristics, strength characteristics, stratigraphy, and mineralogy of Singapore marine clay. The consolidation properties of marine clay are required prior to land reclamation activities in order to predict the magnitude and rates of settlement with the expected fill load and future service load as well as for the design of soil improvement works. The shear strength properties are required for slope stability analyses during reclamation and for the stability analyses of shore protection works. Clay mineralogy tests and photographic identification of the marine clay was carried out to determine the mineralogical properties and to visually record the marine clay colour and texture.