• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.51-56
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• 2004

The sand compaction pile (SCP) method, which forms a composite ground by driving sand piles into clay deposit, is the most commonly used soil improvement techniques in many countries for more than 30 years. Installation of sand compaction piles reduces the amount of consolidation settlement and increases the bearing capacity of soft clay deposit. In this paper, field survey conducted to investigated the consolidation behavior of the composite ground improved by SCPs. It is suggested that the measured consolidation velocity is later than design theory, however measured consolidation settlement is higher than design theory.

• Journal of the Korean GEO-environmental Society
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• v.19 no.9
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• pp.21-28
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• 2018

In this study, a standard consolidation test (Oedometer) was performed on the relative density of sand in the south coast to evaluate long-term creep settlement characteristics. Experimental results show that the cumulative settlement at the final loading stage decreases as the relative density increases and the variation of the void ratio decreases. As a result of analyzing the settlement rate of long-term creep of sand, creep settlement of 4.7~11.0% occurred depending on relative density with respect to total settlement. The creep parameter, Beta, of Schmertmann et al. (1978) was estimated to be 0.17~0.40 (average 0.21), and it tended to converge to a certain value when the load step becomes more than a certain level. It was found that there is no significant difference in the creep parameter depending on the layer thickness, and it was confirmed that the creep parameter could be applied regardless of the field layer thickness.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1212-1217
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• 2008

In this study, in order to clarify the effect of the direction of cyclic shear on the post-earthquake settlement the multi-directional shear tests were carried out for Toyoura Japan standard sand, Genkai natural sand and the Granulated Blast Furnace Slag (GBFS). In a series of tests, number of strain cycles was changed as n=5-200 and the shear strain amplitude varied from 0.1% to 1.0%. The relative density was also changed as Dr=50, 60 and 70%. From the test results for Toyoura sand and GBFS, it is clarified that the post cyclic settlement is relatively large at the small relative density and becomes large with the shear strain amplitude. When the influence of the direction of cyclic shear is decreases, the post cyclic settlement strain for Toyoura sand is converged to a constant value, but the GBFS is increased with the number of strain cycles.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.280-285
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• 2005

At present, there are several problems related with sand mat which is used as a way to accelerate consolidation settlement, act like an underground drainage layer and increase trafficability simultaneously. First of all, the unbalance oft he demand and supply of sand is the one of the biggest problems, which makes not only price advance of sand but also delays a term of total construction work. Secondly, the damage of ecosystem and scenery is triggered by thoughtless sand dredging or mining. So, the need that the sand for sand mat should be replaced with a new environmental friendly material has been increased. Fiber mat may be one of the proper materials that suits the need. Therefore, we intended to compare the drainage properties of sand mat with those of fiber mat by experimental model tests. On the basis of the test results, fiber mat took shorter period of consolidation than sand mat and it's amount of settlement showed a little bit bigger than the other. In conclusion, the substitutability of fiber mat for sand mat could be placed highly in view of drainage efficiency. Furthermore, when Fiber mat is used, it has an advantage that spoil soil of the construction site or nearby site can be used for the purpose of increasing trafficability in addition to a role of drainage layer.

• Journal of the Korean Geotechnical Society
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• v.25 no.8
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• pp.23-32
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• 2009

In this study, the reliable and simple analysis method was proposed to predict the settlement characteristic of composite ground in stage of design and construction of sand compaction pile (SCP). Model parameters could be obtained by the optimization process based on genetic algorithm. In order to examine the proposed method, laboratory consolidation tests on the settlement characteristic of SCP composite ground were performed for various replacement ratio of sand such as 0 (no replacement), 20, 36, and 56%. The proposed model showed very good agreements with measured data in the relation of void ratio-log scaled stress and time-compression far each replacement ratio.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.5
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• pp.103-111
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• 2012

In this study, the full-scale laboratory model test on utilization of recycled aggregates and crushed stone as vertical drains to use an alternative material of sand in soft ground is performed. The settlement and pore water pressure were measured to evaluate the discharge capacity and filed application, and the results were compared and analyzed through the finite element method. The measured and estimated settlement in all vertical drain materials decreases gradually with the load increase. The measured settlement 6.55~8.63 mm, and the estimated by the Hyperbolic model was 7.45~7.92 mm. So the model used for the analysis can be applied to the settlement estimation of the actual field. The variations of pore water pressure with time showed constantly regardless of the load in all vertical drainage materials. The pore water pressure was similarity to that of sand after rapid drawdown. Therefore, it was applicable to the field because discharge capacity was enough to be an alternative material to the sand which had been being used as the vertical drains.

• Journal of the Korean GEO-environmental Society
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• v.11 no.7
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• pp.5-14
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• 2010

The paper processed settlement analysis using Finite Elements Method(FEM). Because Stress Distribution Ratio has to be decreased, for settlement analysis of soft clay deposit improved by sand compaction piles(SCP). Back analysis was processed comparing the measured settlements of laboratory model tests and finite element analysis where the SCP treated area was assumed as mixed ground with clay deposit rather than being a composite ground. The paper proposes a methodology which employs a compression index($C_c$) for settlement analysis of soft clay deposit improved by sand compaction piles from the back analysis. This approach is applied to a field measurement case(A revetment founded on the SCP improved clay deposit with the replacement ratio of 45%).

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.449-456
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• 2009

As soft grounds have complex engineering properties that the load bearing capacity is low and high compressibility, it needs to solve this problems prior to structures are constructed by the method of improvement of soft ground. Generally, the sand mat is used to as a horizontal drain material and loading base for soft ground improvement work. However, as the natural environment can be damaged by sand pickings of large quantity and the volume which is enormous and an amount of demanded sand is increased, it is state of short in supply. This paper presents the result of field experimental test to use Precious Slag Ball to solve these issues instead of sand mat as the replacing material. This study evaluated the performance of Precious Slag Ball as a sand mat in terms of discharge capacity, settlement, and settlement through the K-Embank program.

• Geomechanics and Engineering
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• v.12 no.4
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• pp.689-705
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• 2017

The present study deals with the Pressure-settlement behavior of square and rectangular skirted footing resting on sand and subjected to a vertical load through a laboratory experimental study. A series of load tests were conducted in the model test tank to evaluate the improvement in pressure-settlement behavior and bearing capacity of square and rectangular model footings with and without structural skirt. The footing of width 5 cm and 6 cm and length/width ratio of 1 and 2 was used. The relative density of sand was maintained at 30%, 50%, 70%, and 87% respectively. The depth of skirt was varied from 0.25 B to 1.0 B. All the tests were carried out using a strain controlled loading frame of 50 kN capacity. The strain rate for all test was kept 0.24 mm/min. The results of present study reveal that, the use of structural skirt improves the bearing capacity of footing significantly. The improvement in bearing capacity was observed almost linearly proportional to the depth of skirt. The improvement in bearing capacity of skirted footings over footing without skirt was observed in the range of 33.3% to 68.5%, 68.9% to 127% and 146.7% to 262% for a skirt depth of 0.25 B, 0.50 B and 1.0 B respectively. The skirted footings were found more effective for sand at relative density of 30% and 50% than at relative density of 70% and 87%. The bearing capacity was found to increase linearly with footing width for footings with and without skirts. This observation was found to be consistent for footings with different skirt depths and for relative density of sand i.e., 30%, 50%, 70%, and 87%. The obtained results from the study for footing with and without skirts were comparable with available solutions from literature.

• Geomechanics and Engineering
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• v.6 no.3
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• pp.249-262
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• 2014

Tire chips and tire chips-soil mixtures can be used as alternative fill material in many civil engineering applications. In this study, the potential benefits of using tire chips as lightweight material to improve the bearing capacity and the settlement behavior of sand slope was investigated experimentally. For this aim, a series of direct shear and model loading tests were conducted. In direct shear tests, the effect of contents of the tire chips on the shear strength parameters of sand was investigated. Different mixing ratios of 0, 5, 10, 15 and 20% by volume were used and the optimum mixing ratio was obtained. Then, laboratory model tests were performed on a model strip footing on sand slope reinforced with randomly distributed tire chips. The loading tests were carried out on sand slope with relative density of 65% and the slope angle of $30^{\circ}C$. In the loading tests the percentage of tire chips to sand was taken as same as in direct shear tests. The results indicated that at the same loading level the settlement of strip footing on sand-tire chips mixture was about 30% less than in the case of pure sand. Addition of tire chips to sand increases BCR (bearing capacity ratio) from 1.17 to 1.88 with respect to tire chips content. The maximum BCR is attained at tire chips content of 10%.