• Journal of the Korean GEO-environmental Society
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• v.15 no.12
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• pp.43-51
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• 2014

Organic matter in dredged soil has a lot of engineering problem in ground including a large settlement, crack propagation, low bearing capacity and low friction angle. From an agricultural point of view, however, organic matter contributes greatly soil quality and plant health. This paper investigated the relationship between engineering and germination characteristics of stabilized mixture consisting of different ratios of organic content (0 %, 10 %, 20 %, 30 %) for recycling dredged soil including organic matter. Several series of laboratory tests such as flow test, unconfined compressive test and consolidation test were performed to find out engineering characteristics. pH, percent of germination and growth of plants were also measured to investigate the germination characteristics. The experimental results indicated that, as organic content increased, unconfined compressive stress decreased and compression and swelling indices increased. However, percent of germination and plant growth increases as organic content increases.

• Journal of the Korean GEO-environmental Society
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• v.9 no.6
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• pp.5-12
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• 2008

In this research, the plate load tests on sand which is reinforced by Tirecell mat were simulated by finite element method (FEM). Tirecell mat made by waste tires has the same function and similar shape to Geocell for soil reinforcement and it can also be used for civil engineering structure. The results were compared with those of field plate load tests for evaluation of suitability of modeling method. From the comparison of both results, it can be seen that the settlements by FEM were very similar to test results with small margin under the ultimate bearing capacity. For the ultimate bearing capacities of two results, difference was very small. After the confirmation of the modelling, reinforcing effects with variation of cover depth and number of reinforcement layers by Tirecell were analyzed additionally. Reinforcing effect decreases with increasing soil cover depth, and this is similar to previous test results by soil cover depth. As the number of reinforcing layers increased, reinforcing effect increased. However at more than 2 reinforcing layers, reinforcing effect was negligible. In conclusion, the modeling method in this research might be used for analysis of reinforced structures using Tirecell mat.

• Journal of the Korean Geotechnical Society
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• v.21 no.4
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• pp.21-29
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• 2005

Lightweight Foamed Soil (LWFS) could be the substitute of normal soils used in backfill to earth structures and embankment materials far soft ground improvement in port and harbor project because of its effectiveness in settlement reduction and earth pressure decrease due to its lightness. A series of triaxial and unconfined compression tests were performed to investigate behaviors of LWFS composed of dredged soils, cement and air foam, and cured at underwater conditions. The density of LWFS will increase if LWFS is cured at underwater conditions because high water pressure makes air foam disappear or demolish during the curing compared with LWFS cured at normal air conditions. This paper is to find the mechanical behaviors of LWFS cured at seawater depth of 5.0 m and 10.0 m, respectively, which simulates underwater curing conditions by underwater pressure simulator chamber developed during this study. In addition, new normalized factor formula, which takes account of mixing design conditions determining compressive strength of LWFS, was proposed to consider mixing design factor fur LWFS.

• Structural Engineering and Mechanics
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• v.56 no.4
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• pp.507-534
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• 2015

The present work investigates the behavior of the embankment models resting on soft soil reinforced with ordinary and stone columns encased with geogrid. Model tests were performed with different spacing distances between stone columns and two lengths to diameter ratios (L/d) of the stone columns, in addition to different embankment heights. A total number of 42 model tests were carried out on a soil with undrianed shear strength $${\sim_\sim}10kPa$$. The models consist of stone columns embankment at s/d equal to 2.5, 3 and 4 with L/d ratio equal 5 and 8. Three embankment heights; 200 mm, 250 mm and 300 mm were tested for both tests of ordinary (OSC) and geogrid encased stone columns (ESC). Three earth pressure cells were used to measure directly the vertical effective stress on column at the top of the middle stone column under the center line of embankment and on the edge stone column for all models while the third cell was placed at the base of embankment between two columns to measure the vertical effective stress in soft soil directly. The performance of stone columns embankments relies upon the ability of the granular embankment material to arch over the 'gaps' between the stone columns spacing. The results showed that the ratio of the embankment height to the clear spacing between columns (h/s-d) is a key parameter. It is found that (h/s-d)<1.2 and 1.4 for OSC and ESC, respectively; (h is the embankment height, s is the spacing between columns and d is the diameter of stone columns), no effect of arching is pronounced, the settlement at the surface of the embankment is very large, and the stress acting on the subsoil is virtually unmodified from the nominal overburden stress. When $(h/s-d){\geq}2.2$ for OSC and ESC respectively, full arching will occur and minimum stress on subsoil between stone columns will act, so the range of critical embankment height will be 1.2 (h/sd) to 2.2 (h/s-d) for both OSC and ESC models.

• Geomechanics and Engineering
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• v.12 no.3
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• pp.417-439
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• 2017

The stone columns are increasingly being used as a soil improvement method for supporting a wide variety of structures (such as road embankment, buildings, storage tanks etc.) especially built on soft soil. Soil improvement by the stone column method overcomes the settlement problem and low stability. Nevertheless, stone column in very soft soils may not be functional due to insufficient lateral confinement. The required lateral confinement can be overcome by encasing the stone column with a suitable geosynthetic. Encasement of stone columns with geogrid is one of the ideal forms of improving the performance of stone columns. This paper presents the results of a series of experimental tests and numerical analysis to investigate the behavior of stone columns with and without geogrid encasement in soft clay deposits. A total of six small scale laboratory tests were carried out using circular footing with diameters of 0.05 m and 0.1 m. In addition, a well-known available software program called PLAXIS was used to numerical analysis, which was validated by the experimental tests. After good validation, detailed of parametric studies were performed. Different parameters such as bearing capacity of stone columns with and without geogrid encasement, stiffness of geogrid encasement, depth of encasement from ground level, diameter of stone columns, internal friction angle of crushed stone and lateral bulging of stone columns were analyzed. As a result of this study, stone column method can be used in the improvement of soft ground and clear development in the bearing capacity of the stone column occurs due to geogrid encasement. Moreover, the bearing capacity is effected from the diameter of the stone column, the angle of internal friction, rigidity of the encasement, and depth of encasement. Lateral bulging is minimized by geogrid encasement and effected from geogrid rigidity, depth of encasement and diameter of the stone column.

• The Journal of Engineering Geology
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• v.21 no.2
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• pp.117-124
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• 2011

Soil deformations such as settlement, heaving and lateral flow have frequently happened on marine reclaimed soft grounds due to embankment filling or banking. The electrical resistivity survey was applied to investigate on ground surface such soil deformation without disturbance of ground. A test embankment was performed to assess soil deformation in marine reclaimed soft grounds, where was located at Sihwa area in western coast of Korean peninsula. The soft ground was composed of clayey sediments. After embankment filling, the boundary of soil deformation affected by the filling could be investigated with application of the electrical resistivity survey. The result of electric resistivity survey shows that the extent of deformation is about 5 m laterally to the southern direction of embankment and about 5~6 m vertically in depth, which is about 1-1.2 times of embankment height. This shows that the electric resistivity survey can be applied to interpret the ground deformation in a soft ground region.

• Journal of the Korean Geotechnical Society
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• v.15 no.2
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• pp.129-138
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• 1999

This study is performed for the development of a field monitoring and test technique both of self-weight and hydraulic consolidation by which the soil parameters of dredge-reclaimed clay can be obtained effectively. The field monitoring development and tests mentioned above make it possible to reproduce the process of the self-weight consolidation from settling to reclaimed soft ground. The experimental research is mainly focussed on the characteristics of self-weight consolidation of dredged clayey soil. And theoretical study has pointed out the limits in the application of Terzaghi's one dimensional consolidation theory in interpreting reclaimed clayey ground. Furthermore, a finite difference analysis has been made on the basis of Mikasa s self-weight consolidation theory which takes the problems of Terzaghi's theory into consideration. The relationships between specific volume, effective stress, and the coefficient of permeability of Kunsan reclaimed clayey soil have been obtained by laboratory tests. On the other hand, through the field monitoring, pore pressure, total pressure, and water levels have been measured after pouring. The results of these experiments have been analyzed, and compared with those from Terzaghi's method and the finite difference analysis of Mikasa's self-weight consolidation theory. In conclusion, the measured settlements is comparatively consistent with Mikasa's self-weight consolidation theory rather than Terzaghi's consolidation theory.

• Journal of Soil and Groundwater Environment
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• v.7 no.1
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• pp.41-51
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• 2002

Recently, domestic waste landfills are constructed sometimes on seashore area to provide large landfill area. In order to strengthen the foundation of landfills and to prevent the infiltration of leachate through the bottom, many cases of constructing cement hardened liners on seashore clays are found. In these cases, it is possible to have cracks in the hardened liners due to settlement with waste load since the stiffness of the hardened liner Is greater than that of clay liners. In this study, the capability of Self-Sealing and Self-Healing (SSSH) liner made with a seashore clay in the metropolitan landfill to prevent the percolation of water and leachate is examined using flexible-wall permeameter test and using uniaxial compression test. Applicability of SSSH to weathered granitic soil is also examined for self-sealing capabilities. The result of Flexible permeameter test for SSSH with the seashore clay showed that permeability obtained was lower than permeability criteria of Korean waste management law. The permeability and strength characteristics of SSSH with granitic soil and bentonite showed better results than with the seashore clay.

• Geomechanics and Engineering
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• v.18 no.4
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• pp.407-415
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• 2019

A controlled low strength material (CLSM) is a highly flowable cementitious material used for trench backfilling. However, when applying vertical loads to backfilled trenches, shear failure or differential settlement may occur at the interface between the CLSM and natural soil. Hence, this study aims to evaluate the characteristics of the interface friction between the CLSM and soils based on curing time, gradation, and normal stress. The CLSM is composed of fly ash, calcium sulfoaluminate cement, sand, silt, water, and an accelerator. To investigate the engineering properties of the CLSM, flow and unconfined compressive strength tests are carried out. Poorly graded and well-graded sands are selected as the in-situ soil adjacent to the CLSM. The direct shear tests of the CLSM and soils are carried out under three normal stresses for four different curing times. The test results show that the shear strengths obtained within 1 day are higher than those obtained after 1 day. As the curing time increases, the maximum dilation of the poorly graded sand-CLSM specimens under lower normal stresses also generally increases. The maximum contraction increases with increasing normal stress, but it decreases with increasing curing time. The shear strengths of the well-graded sand-CLSM interface are greater than those of the poorly graded sand-CLSM interface. Moreover, the friction angle for the CLSM-soil interface decreases with increasing curing time, and the friction angles of the well-graded sand-CLSM interface are greater than those of the poorly graded sand-CLSM interface. The results suggest that the CLSM may be effectively used for trench backfilling owing to a better understanding of the interface shear strength and behavior between the CLSM and soils.

• Steel and Composite Structures
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• v.41 no.6
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• pp.831-850
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• 2021

Surface subsidence caused by mining subsidence has an impact on neighboring structures and utilities. In other words, subsurface voids created by mining or tunneling activities induce soil movement, exposing buildings to physical and/or functional destruction. Soil-structure is evaluated employing probability distribution laws to account for their uncertainty and complexity to estimate structural vulnerability. In this study, to investigate the displacement field and surface settlement profile caused by mining subsidence, on the basis of a Winklersoil model, analytical equations for the moment-rotation response ofsoil during mining induced ground movements are developed. To define the full static moment-rotation response, an equation for the uplift-yield state is constructed and integrated with equations for the uplift- and yield-only conditions. The constructed model's findings reveal that the inverse of the factor of safety (x) has a considerable influence on the moment-rotation curve. The maximal moment-rotation response of the footing is defined by X = 0:6. Despite the use of Winkler model, the computed moment-rotation response results derived from the literature were analyzed through the ELM-SVM hybrid of Extreme Learning Machine (ELM) and Support Vector Machine (SVM). Also, Monte Carlo simulations are used to apply continuous random parameters to assess the transmission of ground motions to structures. Following the findings of RMSE and R2, the results show that the choice of probabilistic laws of input parameters has a substantial impact on the outcome of analysis performed.