• Proceedings of the Korean Geotechical Society Conference
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• 2007.09a
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• pp.363-372
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• 2007

The residual settlement due to difference between predicted and observed settlement is one of the social problems during reclaiming construction in the soft ground having a deep depth such as Busan and Gwangyang province. Prediction error for the secondary compression settlement makes the construction much harder. To examine characteristics of the secondary compression settlement, the secondary compression index is the most important factor. In this study, various empirical methods for determining the secondary compression index are evaluated. And errors applied to the design case practically are also explained. The pre loading method is the only way to reduce the secondary compression settlement and reduction ratio of the secondary compression should be investigated correctly. Hence, research results on the reduction ratio of the secondary compression are analyzed in this paper. Moreover, decrement of the secondary compression index due to over consolidation ratio is examined closely by laboratory consolidation test using clay in the Gwangyang area.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.4
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• pp.282-289
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• 2001

This study analyzed the relationship between the physical properties of soil and the compression index of the soft clay in Gyungnam coastal region. Tests of physical and mechanical properties of soil have been carried out under the undisturbed condition at 82 Gimhae, 18 Jinhae and 27 Geojespecimens. The result showed that Terzaghi & Peck's empirical equation of the compression index were not applicable. The compression index of soft clay in Gyungnam coastal region was correlated with the water contents, the liquid limit and the initial void ratio. Among these, the initial void ratio showed the highest correlation with the compression index of soft clay in Gyungnam coastal region and the relationship is shown in the following. (1) The compression index of soft clay in Gyungnam coastal region is represented as follows: $C_c=0.74(e_o-0.7$ (2) The relationship between compression index and the swelling index in Gyungnam coastal region is represented as follows: $C_s=(1/8-1/15)C_c$.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.1200-1205
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• 2010

The compression index is one of the geotechnical properties which represent the compressibility of clay. The compression index are generally obtained from consolidation tests, otherwise it has been predicted by soil properties due to the efficiency time and cost. In this study, consolidation tests result for Busan and Inchon clays are analyzed to suggest the correlations between the compression index and soil properties. It is found that the compression index is well correlated with the void ratio and natural water contents. The prediction errors, which is difference of compression indices between measured from consolidation test and predicted by liquid limits, decrease with ${\Delta}e_0/e_L$.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1998.10a
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• pp.376-381
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• 1998

The large scaled field test by prefabricated vertical drains was performed to evaluate the superiority of vertical discharge capacity for drain materials through compare and analyze the time-settlement behavior with drain spacing and the compression index and consolidation coefficient obtained by laboratory experiments and field monitoring system 1. The relation of measurement settlement( $S_{m}$) versus design settlement( $S_{t}$) and measurement consolidation ratio( $U_{m}$) versus design consolidation ratio( $U_{t}$) were shown $S_{m}$=(1.0~l.1) $S_{t}$, $U_{m}$=(1.13~l.17) $U_{t}$, at 1.0m drain spacing and $S_{m}$=(0.7~0.8) $S_{t}$, $U_{m}$=(0.92~0.99) $U_{t}$ at 1.5m drain spacing, respectively. 2. The relation of field compression index( $C_{cfield}$) and virgin compression index( $V_{cclab}$) was shown $C_{cfield}$=(1.0~1.2) $V_{cclab}$, But it was nearly same value when considered the error with determination method of virgin compression index and prediction method of total settlement. 3. field consolidation coefficient was larger than laboratory consolidation coefficient, and the consolidation coefficient ratio( $C_{h}$/ $C_{v}$) were $C_{h}$=(2.4 ~ 3.0) $C_{v}$. $C_{h}$=(3.5 ~ 4.3) $C_{v}$ at 1.0m and 1.5m drain spacing and increased with increasing of drain spacingngasing of drain spacingng spacingng

• Geomechanics and Engineering
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• v.16 no.2
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• pp.125-140
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• 2018

Tianjin, which is located on the west shore of the Bohai Sea, is part of China's Circum-Bohai-Sea Region, where very weak clay is deposited. From the 1970s to the early $21^{st}$ century, Tianjin marine clay deposits have been the subject of numerous geotechnical investigations. Because of these deposits' geological complexity, great depositional thickness, high water content, large void ratio, excessive settlement, and low shear strength, the geotechnical properties of Tianjin marine clay need to be summarized and evaluated based on various in situ and laboratory tests so that Tianjin can safely and economically sustain more infrastructure in the coming decades. In this study, the properties of Tianjin marine clay, especially its consolidation properties, are summarized, evaluated and discussed. The focus is on establishing correlations between the geotechnical property indexes and mechanical parameters of Tianjin marine clay. These correlations include the correlations between the water content and the void ratio, the depth and the undrained shear strength, the liquid limit and the compression index, the tip resistance and the constrained modulus, the plasticity index and the ratio of undrained shear strength and the preconsolidation pressure. In addition, the primary consolidation properties of Tianjin marine clay, such as the intrinsic compression line (ICL), sedimentation compression line (SCL), compression index, $C_c$, coefficient of consolidation, $C_v$, and hydraulic conductivity change index, $C_{kv}$, are evaluated and discussed. A secondary consolidation property, i.e., the secondary compression index, $C_a$, is also investigated, and the results show that the ratio of $C_a/C_c$ for Tianjin marine clay can be used to calculate $C_a$ in secondary consolidation settlement predictions.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09b
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• pp.76-80
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• 2010

This paper describes that estimation methods for the distribution of consolidation settlements to investigate the influence of distribution characteristics of compression index on the spatial distribution of consolidation settlements. When the variation of compression index is considerable, the spatial distribution of compression index is estimated using ordinary cokriging. The spatial distribution of consolidation settlements estimated by considering both the variation of compression index and void ratio (CASE-1) is different from the conventional mean value of all soil properties (CASE-2). The settlement of CASE-1 shows the larger variation at short distances rather than that of CASE-2. Whereas the spatial settlement distribution of CASE-1 is affected by the spatial distribution of compression index and the thickness of consolidation layer, the distribution of CASE-2 is significantly influenced by the distribution of the thickness of consolidation layer.

• KCID journal
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• v.5 no.1
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• pp.75-82
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• 1998

A multivariate regression analysis for compression index and com- pressibility ratio of clayey soils in regard to some soil indices, i.e natural water content, Atterberg limits, and in-situ void ratio, was presented to estimate the primary consolidation s

• Steel and Composite Structures
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• v.13 no.5
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• pp.437-449
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• 2012

Concrete filled steel tube (CFST) structures have recently seen wide use in China, but studies of the shear problem of CFST are inadequate. This paper presents an experimental study on the shear capacity of circular concrete filled steel tube (CCFT) specimens with and without axial compression force. Shear capacity, ductility, and damage modes of CCFTs were investigated and compared. Test results revealed the following: 1) CCFTs with a small shear span ratio may fail in shear in a ductile manner; 2) Several factors including section size, material properties, shear span ratio, axial compression ratio, and confinement index affect the shear capacity of CCFTs. Based on test results and analysis, this paper proposes a design formula for the shear capacity of CCFTs.

• Geomechanics and Engineering
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• v.37 no.4
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• pp.371-382
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• 2024

Measurement or prediction of compression index (C_c) of soils is essential for assessment of total and differential settlement of structures. It is a well-known fact that this parameter is controlled by several index identifiers of soil including initial void ratio, Atterberg limits, overconsolidation ratio, specific gravity, etc. Many studies in the past proposed relationships for prediction of C_c based on different index properties. Therefore, this study aims to present a comparison of previously proposed equations for estimation of C_c. Data from literature was compiled, and a total of 90 and 623 test results on remolded and undisturbed specimens were used to question the validity of previously proposed equations. Nevertheless, the modeling ability of 7 and 12 equations for estimation of C_c of remolded and undisturbed soils were questioned by use of compiled data. Moreover, new empirical relationships based on initial void ratio and toughness limit for prediction of C_c was proposed by use of nonlinear multivariable regression and evolutionary based regression analyses. The results are promising-the performances of models established are quite acceptable, which are verified by statistical analyses.

• Magazine of the Korean Society of Agricultural Engineers
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• v.42 no.5
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• pp.133-143
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• 2000

A large scale field test of prefabricated vertical drains was performed to anayze the effect of parameters of the very soft clay at a test site. compression index and the coefficient of horizontal consolidation obtained by back-analysis of settlement data were compared with those obtained by means of laboratory tests. Hyperbolic method, Asaoka meoth and curve fitting method were used to compute final settlement of coefficient of consolidation. The relationships of settlement measurement(Sm) versus design settlement(St) and the measurement consolidation ratio(Um) versus design consolidation (Ut) were shown as Sm=(1.0~1.1) St , Um=(1.13~1.17) Ut at 1.0m spacing of drain and Sm=(0.7~0.8)St, Um= (0.92~0.99) Ut at 1.5 m spacing of drain, respectively . The relationships of the field compression index(CcField) and virgin compression index(vcc lab) were shown as Ccfield =(1.0~1.2)vcc lab . But it was nearly within the same range when considering the error factor with the determination method of virgin compression index and the prediction back-analysis of the settlement data was larger than the coefficient of vertical consolidation, and the ratio of consolidation coefficient (Ch/Cv) was Ch =(2.4~2.9) Cv , Ch=(3.4~4.2) Cv at 1.0m and 1.5m spacing of drain, respectively.