Byoung-Il Kim

Comparison of bearing capacity characteristics of sand and gravel compaction pile treated ground

Sand compaction piles which are constructed as compacted sand piles in the weak soils are used frequently in Korea as one of the soil improvement techniques. But it is necessary to find a new technique which can replace sand compaction piles because of decrease of sand resources and increase of sand cost. In this study, load tests of model composite ground which is composed ofgravel compaction piles and clays are executed in order to find out bearing capacity characteristics and the same load tests of sand compaction piles are executed to compare the results of both load tests. Area replacement ratios of gravel compaction piles and those of sand compaction piles are 30%, 40%, and 50%, respectively and a model composite ground is preconsolidated by centrifugal consolidation apparatus before the load test. And the bearing capacities from test results are compared with those predicted by existing formulas.

Comparison of the Lateral Earth Pressure on the Retaining Wall with the Relieving Platform by Model test and Numerical Analysis

Abstract The retaining wall with the relieving platform can be constructed as an alternative to the concrete retaining wall in which the economic and stability are decreased as height increases. The relieving platform has the advantage of decreasing the total lateral earth pressure on the retaining wall and increasing the overall stability of the structure. In this study, model tests were performed to determine the distribution of the earth pressure on the retaining wall with and without the relieving platform which located at a depth of 0.4H from the ground surface. And model tests results were compared with analyzed results by 2-D finite element method and values driven from theoretical equation. As the result of this study, comparing model test results with those of numerical analysis and theoretical equation show that the reduction of the lateral earth pressure on wall was indicated clearly on the retaining wall with a relieving platform. Key Words : retaining wall, relieving platform, lateral earth pressure, model test, finite element method, theoretical equation

Numerical Analysis for Lateral Earth Pressure on Retaining Wall with Relieving Platform backfilled with Jumoonjin Sand

Abstract Generally, the retaining wall is becoming unstable as the height is higher. On the other hand, the retainingwall with the relieving platform is more stable and more economical than any other type of retaining wall, becausethe relieving platform the reduce the lateral earth pressure. In this study, numerical analyses were carried out for 15cases varying with the type of retaining wall, length and location of the relieving platform and the backfill type. Fromthe numerical analyses, the reduction of the lateral earth pressure was checked and the results of numerical analyseswere compared with that of model tests and theoretical equations. As the results of this study, the lateral earth pressure of the retaining wall with the relieving platform is considerably less than that of cantilever wall. And theof magnitude of the lateral earth pressure is affected by the length and location of relieving platform and the backfilltype. Key Words : Lateral earth pressure, model test, numerical analysis, relieving platform, retaining wall

Model Tests for Measurement of Lateral Earth Pressure on Retaining Wall with the Relieving Platform Using Jumoonjin Sand

Recently, the retaining wall with the relieving platform has received increasing interests also in Korea in that it can reduce the lateral earth pressure and provide more stability than conventional retaining wall. Previous studies with model tests studies covered only a limited test conditions. In this study, total 15 model tests were performed for various conditions with improved model test apparatus to confirm the effect of decreasing the lateral earth pressure on the retaining wall with the relieving platform. Jumoonjin sand was used for model soil and 2 load cells were used for each 15 layers to measure the lateral earth pressure. Based on the experimental results, the lateral earth pressure of the retaining wall with the relieving platform is less than the that of cantilever wall. The length of the platform and the location of the platform are the key factors influencing the lateral earth pressure.

Analytical Study on Characteristics of von Mises Yield Criterion under Plane Strain Condition

In order to investigate characteristics of the von Mises yield criterion under 2 dimensional stress condition, two cases of plane strain were studied. One of which was for zero elastic strain and the other was for zero plastic strain increment. Yield functions for the plane strain condition for zero elastic strain and for the plane stress condition were represented as ellipse and the two yield functions were compared by ratios of major axis, minor axis and eccentricity and it was seen that the ratio of minor axis was the same between the two cases and the ratios of major axis and eccentricity were functions of Poissons ratio. Region of elastic behavior obtained from considering plane strain condition of zero elastic strain increases as the Poissons ratio increases. Yield function for plane strain obtained from considering zero plastic increment and associate flow rule was displayed as straight line and the region of elastic behavior was greater than that for the case of plane stress.

Study on the Effect of Base Projecting Walls of Shallow Footing on Bearing Capacity

In order to find out the effect of base projecting walls of footing supporting soft ground on increase of bearing capacity, numerical analyses were conducted with varying the number and length of the base projecting walls and the results of the numerical analyses were compared with those of the model tests. It can be seen from the results of numerical analyses and the model tests that the bear- ing capacity of the footing supporting soft ground increases due to the existence of the base projecting walls and the bearing capacity increases with increase of the length of the base projecting walls. According to the results of the model tests, it can be seen that bear- ing capacity increases with the number of the base projecting walls of 2 to 4 and it decreases when the number of the base projecting walls of 5 whereas results of the numerical analyses show that bearing capacity was little affected by the number of the base pro- jecting walls. It can be said from the results of the model tests and the numerical analyses that economical design of the footing with base projecting walls be accomplished for the value of unity of the ratio of the length to the spacing of the base projecting walls.

A Case Study on Collapsed Geosynthetic Reinforced Segmental Retaining Wall

This case study deal with the investigation of various causes and analyses concerning the cases of the collapse of reinforced segmental retaining walls installed for newly constructing a peripheral road within the campus of ◯◯ University located in Gyeonggi-do. As results of stability analyses and reviewing of design documents concerning collapsed reinforced segmental retaining walls, such a collapse appeared because of problems related to construction including poor-compacted backfill, the omission of the investigation on the bearing capacity, the length and space in the installation of reinforced materials, and drainage systems. Also, problems during diverse types of designing were confirmed involving the stability analysis of the entire slope stability to be considered during designing and failure in application of the proposed methods of FHWA or NCMA which are generally used for two-tier reinforced segmental retaining walls. In addition, based on these details of the stability assessment, the study proposed reinforcement solutions and construction methods for stabilizing reinforced segmental retaining walls to be reconstructed in the future.

An Experimental Study on the Behavior of Composite Ground Improved by SCP and GCP with Low Replacement Ratio

Abstract This paper presents the results of laboratory tests conducted to investigate the effectiveness of applying methodology of a sand compaction(SCP) and a gravel compaction pile(GCP) on soft ground. The test conditions involved relatively low replacement ratios (=10, 20, and 30%) of a pile to unit cell at 1g (gravity acceleration) level. Results revealed that GCP significantly enhanced bearing capacity, settlement reduction, and consolidation rate compared with SCP. Key Words : SCP, GCP, Low replacement ratio, Bearing capacity, Settlement * Corresponding Author : Wan-Kyu Yoo (Korea Institute of Construction Technology)Tel: +82-31-336-8837 email: lyu5553@hanafos.comReceived October 24, 2012 Revised February 1, 2013 Accepted February 6, 2013 1. 서론 해상 또는 해안의 연약지반에 구조물을 축조할 때 지반개량을 목적으로 모래다짐말뚝(sand compaction pile, 이하 SCP), 자갈다짐말뚝(gravel compaction pile, 이하 GCP) 또는 쇄석기둥(stone column) 등의 공법을 적용할 수 있다. 이들 공법은 연약지반에 골재를 다짐하면서 압입하여 말뚝을 조성하는 공법으로 점토지반에 적용할 때에는 주로 지반의 전단강도 및 지지력 증대, 측방변위 억제, 압밀침하 저감 등의 효과를 목적으로 한다[1, 2]. 이러한 공법들 가운데 국내에서 가장 많은 시공실적을 보이며 널리 사용된 SCP공법의 경우에는 모래 자원의 고갈, 가격상승 및 다짐말뚝 품질유지에 어려움이 있는 등 문제점이 있다[3]. 이에 따라 대체 공법으로 쇄석 또는 자갈을 말뚝의 재료로 사용하는 GCP공법에 대한 관심과 시공실적이 증가하였다. SCP와 GCP 등 골재 말뚝으로 보강된 지반은 복합지반으로 고려할 수 있으며 이러한 복합지반의 거동특성은 골재의 종류, 치환율(

Analysis on Behavior of Vertically Loaded Single Pile included in Pile Group

Abstract Static pile load tests were conducted on the two piles which comprised group pile installed in sand and the test results were compared with those obtained from load transfer method. Predicted load bearing capacity of the pile which locates center portion of the group pile was less than that from the load test and the reason is thought to be the densification of the soil due to the installation of the group pile. Predicted pile capacity of the API method, Coyle and Sulaiman method were 77%, 90% of the bearing capacity obtained from the load test, respectively. Comparing ultimate bearing capacities of the pile locating at the edge of the group pile, those predicted by the API method, Coyle and Sulaiman method were 1.1 times, 1.3 times of the bearing capacity obtained from the pile load test, respectively. Key Words : Load test, Load transfer method, API method, Coyle and Sulaiman method * Corresponding Author : Byoung-Il KimTel: +82-10-2722-6415 email: bikim@mju.ac.kr접수일 12년 07월 16일 수정일 12년 07월 27일 게재확정일 12년 10월 11일

Stability Analysis of DCM treated Ground Using Centrifuge Test

Recently, a deep mixture method as a soil improvement method of marine soft ground, which causes less noise and vibration than other methods, are widely used. In this study, for DCM(Deep Cement Mixing) method, one of the deep mixture method, optimum mixing ratio of clay-cement was suggested using uniaxial compression tests on specimens with various mixing ratio of claycement. In addition, the stability of a caisson on tangent circle-type and wall-type DCM treated ground was evaluated using centrifuge tests. As a result, optimum mixing ratio of clay-cement was 28.5% and the stability of the caisson on DCM treated ground was confirmed. However, the lateral displacement of the caisson on the wall-type DCM treated ground was 7% less and the settlement of that was 39% less than the case of the tangent-circle-type DCM method.