• Geomechanics and Engineering
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• v.27 no.5
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• pp.447-463
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• 2021

Caisson-type structures are widely used as quay walls in coastal areas. In Korea, for a long time, many caisson-type quay walls have been constructed with a low front water depth. These facilities can no longer meet the requirements of current development. This study developed a new technology for deepening existing caisson-type quay walls using grouting and rubble mound excavation to economically reuse them. With this technology, quay walls could be renovated by injecting grout into the rubble mound beneath the front toe of the caisson to secure its structure. Subsequently, a portion of the rubble mound was excavated to increase the front water depth. This paper reports the results of an investigation of the seismic behavior of a renovated quay wall in comparison to that of an existing quay wall using centrifuge tests and numerical simulations. Two centrifuge model tests at a scale of 1/120 were conducted on the quay walls before and after renovation. During the experiments, the displacements, accelerations, and earth pressures were measured under five consecutive earthquake input motions with increasing magnitudes. In addition, systematic numerical analyses of the centrifuge model tests were also conducted with the PLAXIS 2D finite element (FE) program using a nonlinear elastoplastic constitutive model. The displacements of the caisson, response accelerations, deformed shape of the quay wall, and earth pressures were investigated in detail based on a comparison of the numerical and experimental results. The results demonstrated that the motion of the caisson changed after renovation, and its displacement decreased significantly. The comparison between the FE models and centrifuge test results showed good agreement. This indicated that renovation was technically feasible, and it could be considered to study further by testbed before applying in practice.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.169-177
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• 2017

Recently, as the size of transportation vessels has increased, there is a growing need for securing the front-water depths of existing port facilities. The method of deepening front-water depth is securing the depth of the port facility, and it is reinforced by grouting after excavating the rubble-mound to the required depth. The purpose of this study is to investigate the reinforcing performance and filling performance of thixotropic grout as a grouting material for reinforcing rubble-mound. Compressive strength tests were carried out for two types of thixotropic grout, and 5 specimens with a diameter of 400 mm and a height of 530 mm were manufactured and evaluated for filling performance. The required strength of reinforced rubble-mound required to ensure the safety of the structure is 6 MPa. All the thixotropic grouts used in this study were found to satisfy the required strength over 9 MPa at 7 days of age. As a result of visual observation of filling state of the filling performance test specimens, it was confirmed that the thixotropic grout was well filled up to the desired fillet height.

• Journal of the Korean Geotechnical Society
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• v.26 no.11
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• pp.75-87
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• 2010

Incessant rainfalls in unsaturated soil raises pore water pressure and drops shear stress. Controlling pore water pressure in unsaturated soil prevents pressure increase and leads to slope stability. Laboratory experiment of pore water absorption in soil tank has been conducted for pore pressure decrease in soil slope under artifical rainfall supplied in varying rainfall indensities. Soil slope failure triggers the deepening of the wetting front to critical depth accompanied by decrease in matric suction induced by water infilteration. This paper addresses an experimental design for absorption pipe to prevent pore pressure increase in unsaturated soil slope from heavy rain. It is expected that absorption pipe will be widely used in unsaturated soil slope to strengthen slope stability.

• Journal of the Korean Geotechnical Society
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• v.20 no.7
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• pp.159-169
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• 2004

Surface failures of slopes in weathered soil are caused by infiltration due to prolonged rainfall. These failures are mainly triggered by the deepening of the wetting band accompanied by a decrease in suction induced by the infiltrating water. This paper reports trends of rainfall-induced wetting band depth in two types of weathered soils that are commonly found in Korea. Both theoretical and numerical analyses are presented based on the soil-water characteristic curve (SWCC) obtained using filter paper as well as tensiometer tests. It is found that the magnitude of wetting front suction plays a key role in the stability of slopes in weathered soils. Theoretical analysis based on modified Green and Ampt model tends to underestimate the wetting band depth for typical Korean weathered soils. It was also deduced that for Korean weathered soils, the factor of safety drops rapidly once the wetting band depth of 1.2 m is reached.