• Geotechnical Engineering
• /
• v.1 no.2
• /
• pp.17-26
• /
• 1985

This study was carried out for the purpose of comparing in reference to sand drain in the next three different cases. First, The case of drain material (sand pile) has some rigidity during embankment and consolidation. Second, In usual case of no rigidity as a paper drain without permeability during embankment and consolidation Third, Check up clay behavior when above the two cases carried out respectively. This FEM analysis is consisted with Biot's consolidation equation when it is used for Christian Boehmer's numerical technique. The main results are obtained from above the Analysis When sand drain has some rigidity, the lateral and vertical deformation of clay foundation is restrained considerable amount and .exhibited bearing capacity of load as a pile According to the foundation in drained condition and untrained condition, the results are much variable in this analysis method. Also, The behaviors of stress path and pore water pressure met our expectation during , consolidation. This analysis should be considered to put into use of sand drain and design in future.

• Journal of Industrial Technology
• /
• v.25 no.B
• /
• pp.63-71
• /
• 2005

This paper is an experimental result of investigating lateral soil movements at piled bridge abutments by using the centrifuge model facility. Three different centrifuge model experiments, changing the methods of ground improvement at bridge abutment on the soft clayey soil (no improvement, preconsolidation and plastic board drains (PBD), sand compaction pile (SCP) + PBD), were carried out to figure out which method is the most appropriate for resisting against the lateral soil movements. In the centrifuge modelling, construction process in field was reconstructed as close as possible. Displacements of abutment model, ground movement, vertical earth pressure, cone resistance after soil improvement and distribution of water content were monitored during and after centrifuge model tests. As results of centrifuge model experiments, preconsolidation method with PBD was found to be the most effective against the lateral soil movement by analyzing results about displacements of abutment model, ground movement and cone resistance. Increase of shear strength by preconsolidation method resulted in increasing the resistance against lateral soil movement effectively although SCP could mobilize the resistance against lateral soil movement. It was also found that installment with PBD beneath the backfill of bridge abutment induced effective drainage of excess pore water pressure during the consolidation by embanking at the back of the abutment and resulted in increasing the shear strength of clay soil foundation and eventually increasing the resistance of lateral soil movement against piles of bridge abutment.

• Journal of the Korean GEO-environmental Society
• /
• v.9 no.7
• /
• pp.13-23
• /
• 2008

In this study, the centrifuge tests and numerical analyses were performed to investigate the lateral flow behavior and stability of abutment when high filling was applied on the soft ground improved by SCP. The centrifuge model tests and numerical analyses were fulfilled in the case of the back of abutment filled by EPS (case 1) and soil (case 2), and the potentiometer was installed on the abutment and fill to measure the vertical and horizontal displacement at the top of abutment. As a result of the centrifugal tests, the horizontal displacement of abutment in the case 1 was 1.4cm that is almost coincide with the results of numerical and satisfy the allowable standard. On the other hand, the horizontal displacement of abutment in the case 2 was 12 cm that is 18% greater than that of numerical analysis and exceed the allowable standard. As a result of analysis, the maximum horizontal displacement of pile was 1.26 cm in case 1 that satisfies the criterion of allowable horizontal displacement (1.5 cm). In contrast, the maximum horizontal displacement of pile was 1.005 m in case 2 that greatly exceeds the allowable horizontal displacement.

• Journal of Ocean Engineering and Technology
• /
• v.11 no.1
• /
• pp.65-73
• /
• 1997

The floating body discussed in this study is a 2-D rectangular floating unit supported by four vertical piles at its corners. Structures of this type are frequently seen as floating piers for the crafts in a small harbour. The movement in some modes of motion of such a flating body is fully or partially restrincted by the piles. The authors(Kim et al. 1994) carried out a series of model tests on its wave control function, its motion and the loads on piles. The experimental results showed that a certain degree of intial constriction force which clamps the floating unit in the horizontal direction can effectively reduce the body motion and wave energy without increasing mooring forces. This may be due to the friction forces occuring between the piles and the rollers installed in the mooring equipments on the floating unit. In this paper, we develop a numerical model for the prediction of wave transformation and floating body motions, where the friction force is idealized as the Coulomb friction and linearized into a damping force using the equivalent damping cofficient. This linearization is verified by comparing the results of motions between the linear and nonlinear analysis of the ezuations of motion. We further compare the caculation results by the linear model with the experimental results and discuss the effect of the friction force or the constriction force on body motions and wave energy dissipation.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.27 no.3
• /
• pp.182-189
• /
• 2015

The Embedded Suction Anchor (ESA) is a type of permanent offshore foundation that is installed by a suction pile. To increase the loading capacity against pullout, three wings (vertical flanges) are attached along the circumference at 120 degrees apart. Analytical parametric study using the proposed analytical solution method has been conducted to identify the effects of several parameters that are thought to influence the behavior of ESAs. The analysis results show that the pullout capacity increases as the anchor depth and the soil strength increase, and decreases as the load inclination angle increases. The anchor having square projectional area and being pulled horizontally at the middle of its length provides the highest pullout capacity.

• Journal of the Korean Geotechnical Society
• /
• v.33 no.2
• /
• pp.5-15
• /
• 2017

PHC-W retaining wall method is one of the economical retaining wall methods. PHC-W pile used in PHC-W retaining wall method has special shape with flat surfaces so that the PHW-C retaining wall, with overlapped piles, shows outstanding vertical control and impermeability. In order to evaluate two types of retaining walls, numerical analysis were performed. The selection of cases depended on N values of the ground and ground properties, and two types of PHC-W retaining walls (defined as type A and B) were constructed. For a case that consists of inorganic clay and sand with less than 30 of N value, the maximum excavation depths for type A and B were respectively 10.5 m and 11.0 m. At the other case of which N value is above 30, the depths were 17.0 m and 19.5 m. From the results, it was found that maximum excavation depth, horizontal displacement, and safety factor for flexural strength of the wall were influenced by ground properties.

• Geotechnical Engineering
• /
• v.12 no.2
• /
• pp.71-84
• /
• 1996

In order to investigate the influence of slanting angle of reticulated root piles(RRP) on their bearing capacities, model tests of compressive and uplift loads on RRP with different slanting angles, which were installed in sandy soils with a relative density of 47%, were carried out. Each pile which is made of a steel bar of 5mm in diameter and 300mm in length, is coated with sand to be 6.5mm in diameter. One set of RRP consists of 8 piles which are installed in circular patterns forming two concentric circles, each of which has 4 piles. Slanting angles of RRP for load tests are 0$^{\circ}$, 5$^{\circ}$, 10$^{\circ}$, 15$^{\circ}$, 20$^{\circ}$, and 25$^{\circ}$. In addition, compressive load tests on circular footing whose diameter is the same as the outer circle of RRP were carried out. Test results show that maximum load bearing capacities of RRP by regression analysis are obtained at about 12$^{\circ}$ and 13$^{\circ}$ of slanting angles for compressive and uplift load tests, respectively. Maximum compressive bearing capacity is estimated to be 13oA bigger than that of the vertical RRP and 95% bigger than that of surface footing. Maximum uplift capacity is estimated to be 21% bigger than that of the vertical RRP. And it can be appreciated that increasing the slanting angle makes the load -Settlement behavior more ductile.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.11 no.3
• /
• pp.209-218
• /
• 2011

The present study proposes a new estimation relationship for the transmission rate of the steel breakwater which is expected to make up for the weakness points in existing hard solution for shore protection. The steel breakwater consists of the wave dissipator of the dual horizontal plates, the supporting columns and their foundations, and thus its respective designs should also be conducted one by one. Furthermore, the breakwater has to ensure both functions of shore protection and structure stabilization. The study produced experimental data for the stability and safety investigation of the steel breakwater. The forces acting on the steel breakwater were classified into two categories, one is vertical up and down loads for the pile resistance and the other was maximum difference of the vertical load acting on horizontally different position for the torsion. The study applied the stability force produced by the summation of maximum pressure at each point and the safety force acting on each point simultaneously. The regular wave corresponding to the significant wave was utilized for measuring wave pressure and force. The study showed the method for the proper position of submerged upper plate by considering occurrence frequency of tide level. The design process finally determined by trial and error is proposed in the present study.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.21 no.3
• /
• pp.397-418
• /
• 2019

It is very important to understand and analyze the interactive behaviour between ground and adjacent structures due to tunneling. With many technological advancement in modern society, numerous methods for analyzing the interactive behaviour are used in a wide range of civil engineering fields. Close range photogrammetry is mainly being used in the field of geotechnical engineering and research on measuring methods associated with GeoPIV has been currently increased. Originally, the close range photogrammetry using target points and aluminum rods for VMS (Vision Measurement System) program has been used. However, applying this has a problem that external errors can be occurred because the target points are artificially installed by hand, and if the grid between points is being wider or narrower, deficient data can be obtained. Therefore, in this study, MATLAB-based No-target program that can analyze displacement without using target was developed. Additionally, this study focused on comparison and verification with existing program through numerical analysis and laboratory model test. Three cases of Greenfield condition, Strip foundation, and Pile foundation were analyzed. From results of VMS program and No-target program, the error rate and reliability of the total displacement and the vertical displacement were analyzed. It was also compared and verified through the finite element numerical program, PLAXIS.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.6C
• /
• pp.395-406
• /
• 2006

Drilled shafts are a common foundation solution for large concentrated loads. Such piles are generally constructed by drilling through softer soils into rock and the section of the shaft which is drilled through rock contributes most of the load bearing capacity. Drilled shafts derive their bearing capacity from both shaft and base resistance components. The length and diameter of the rock socket must be sufficient to carry the loads imposed on the pile safely without excessive settlements. The base resistance component can contribute significantly to the ultimate capacity of the pile. However, the shaft resistance is typically mobilized at considerably smaller pile movements than that of the base. In addition, the base response can be adversely affected by any debris that is left in the bottom of the socket. The reliability of base response therefore depends on the use of a construction and inspection technique which leaves the socket free of debris. This may be difficult and costly to achieve, particularly in deep sockets, which are often drilled under water or drilling slurry. As a consequence of these factors, shaft resistance generally dominates pile performance at working loads. The efforts to improve the prediction of drilled shaft performance are therefore primarily concerned with the complex mechanisms of shaft resistance development. The shaft resistance only is concerned in this study. The nature of the interface between the concrete pile shaft and the surrounding rock is critically important to the performance of the pile, and is heavily influenced by the construction practices. In this study, the influences of asperity characteristics such as the heights and angles, the strength characteristics and elastic constants of surrounding rock masses and the depth and length of rock socket, et. al. on the shaft resistance of drilled shafts are investigated from elasto-plastic analyses( FLAC). Through the parametric studies, among the parameters, the vertical stress on the top layer of socket, the height of asperity and cohesion and poison's ratio of rock masses are major influence factors on the unit peak shaft resistance.