Tae-Hyung Kim

This paper provides a detailed study of remediation work on the core zone of a damaged earth-fill dam. The relevant material includes a review of the dam surface survey data, leakage monitoring data, drilling method, grouting material, and drilling and grouting procedure. A compaction grouting method was selected as the remediation technique. In addition, the reduction and prevention of leakage and settlement were assessed. Compaction grouting was successful for filling voids, closing channels, and compacting the disturbed core soils. The loose or voided zones were properly filled, and the leakage was reduced after compaction grouting. Verification of the compaction grouting work was performed by evaluating the grouting pressures and volumes injected internally and by monitoring the dam leakage rate and tracer externally. All of these factors provide a good indication of changes inside the core of the dam, including reduction or closure of the leakage channels in the dam core.

Noise and vibration caused by pile driving may disturb surrounding areas to the extent that nearby residents and businesses may file civil complaints, which can bring construction to a halt. To overcome these issues, construction engineers have worked diligently to develop low-noise and low-vibration pile driving methods. One such method, involving noise-free and vibration-free pretensioned spun high-strength concrete (PHC) screw piles, is proposed in this paper. This pile driving method penetrates the ground by rotating and compressing the pile to minimize noise and vibration in addition to maximizing capacity. A noise-free and vibration-free PHC screw pile prototype, the first of its kind, was manufactured and subjected to two pilot tests to determine its production and construction requirements in addition to its performance. In pilot tests, the new noise-free and vibration-free PHC screw pile driving method was found to successfully reduce noise and vibration compared with pile driving involvi...

This paper introduces the Pulse Discharge Technology (PDT) piling method. The PDT piling method installs in-situ piles using electrical pulse power. The pulse power is a physical value that indicates the energy change per unit time. The power depends on how fast the energy is released. If a unit of energy is discharged in 1 sec, a watt of power will be generated. If the energy is discharged in 1 µs (10⁻⁶ sec), the power will be 1MW. Since the pulse power pushes the ground, using the pulse power enables the hole to be expanded and the ground to be improved by compaction. Therefore, the pile installed by PDT appears to be able to efficiently develop shaft and end-bearing capacity. A series of experiments and load tests were conducted in order to investigate the characteristics of expansion and bearing capacity. It was found that the coefficient of expansion increases with an increase of the number of pulse discharges and has an inverse proportion to the standard penetration test value, N. It was also examined that the piling technique using pulse power can be expected to not only increase end-bearing capacity, but also shaft resistance.

During the construction of the pneumatic caissons supporting the towers of the Youngjong Grand Bridge in South Korea, the cutting edge of the Incheon side caisson was equipped with a number of strategically positioned reaction force gauges to measure vertical cutting edge contact pressures and to assess the contact pressure distribution developed during caisson sinking through a range of ground conditions. The magnitude of the contact pressure and its distribution under a foundation varies depending principally upon the physical properties of the founding material, foundation dimensions and the rigidity of the foundation construction. This requires the designer to make an engineering judgment based on the results of the site investigation and the rigidity of the foundation.

Mode I (tensile) fracture is the most commonly observed failure in geostructures resulting from cracks in soil. Direct or indirect tensile tests have been used to evaluate the tensile strength of geomaterials. In this paper, the unconfined penetration device and experimental procedure were modified to reduce measurement errors. It was then used to determine the tensile strength of compacted soil. Factors influencing the tensile strength of the compacted soil, including the plasticity index, rate of loading, and size of specimen were discussed in detail, as well as its reliability. Experimental results indicated that the modified, unconfined penetration technique is sufficiently reliable and operator-friendly for determining the tensile strength of compacted soil.

This study was conducted to find out the characteristics of the lightweight air-mixed soil (LWS) used for a road embankment. Compressive strength, permeability, and capillary height of the LWS were studied, and to support these studies, its inside structure was analyzed in detail. Various size air pores exist in the LWS, and their distribution with a location is almost constant. Numerous tiny cracks formed by different grain sizes between in-situ soil (silty marine sediment) and solidificator exist inside the air pores so that the LWS can be affected by water. Peak strength of the LWS is found to be less dependent on the water, but the behavior of strength-strain was affected by water. Permeability is a little bit higher than clay's permeability. Capillary rise is rapid in the beginning of the test, and then slows down. The capillary rise can increase the density of the LWS, and thus requires special attention during design and maintenance of the structures, which were constructed with the LWS.

The construction of a rubble mound on soft ground, which was improved using the deep cement mixing method, was observed instrumentally and analyzed. To establish the design criteria for the rubble mound on the improved ground, two types of analyses of soil deformation behavior and slope stability were performed for various cases of rubble mounds on soft ground and backfills: the finite element method and the Bishop simplified method. Horizontal displacements and settlements at the rubble mound crests were analyzed as a function of the embankment safety factor. In addition, dimensionless displacement factors, R_x and R_y, are proposed to increase the adaptability of the analytical results in the field. The factors considered include soil displacements, such as horizontal displacement and settlement induced by a combination of rubble mound construction and improved ground. The analytical results show that soil movement increased considerably when the safety factor of rubble mounds was lower than 1.3. The suggested horizontal displacement and settlement critical values are given when the embankment safety factor is 1.3.

The behaviors of the marine sedimentary ground improved by sand compaction pile (SCP) method are analyzed. To do this, the results of upheaval characteristics of the sea floor, undrained shear strength, and horizontal consolidation coefficient (consolidation) are investigated. Due to SCP installation on ground, as thickness of a soft clay layer increases, upheaval height increases and upheaval angle decreases. Undrained shear strength of disturbed ground due to SCP construction decreases in early stage after completion of construction, but it shows a trend of recovering as months elapse. As the result of piezocone penetration dissipation tests, consolidation delay phenomenon by the disturbance due to SCP installation clearly is identified and its degree is dependent on the replacement area ratio of SCP and the location of ground.

A series of triaxial compression tests were performed on samples of compacted granite soils in a modified triaxial cell that can separately control pore air pressure (u_a) and pore water pressure (u_w) in order to examine the characteristics of pore pressure, volume change and stress-strain behavior under undrained loading condition. Unsaturated granite soil samples were prepared by compaction in a mould. These samples were tested at different suction and different confining stresses. The volume change of an unsaturated soil during shearing undrained is much sensitive to the confining pressure compared to the initial water content, and the matric suction. The volume expands during shearing, and the volumetric strain is much larger at the smaller confining pressure and at the higher matric suction. The variation of the internal frictional angle according to the initial water content and the matric suction is negligible, but the effective cohesion increases according to matric suction.