• Journal of the Korean GEO-environmental Society
• /
• v.11 no.3
• /
• pp.23-32
• /
• 2010

In this study, Generally sandbag was used to reinforce slope or restore levee by using the in-situ material. To increase shear strength of sandbag, the Velcro system was effective for geosynthetic interface and make up for the weakness of shear strength between sandbag to sandbag. In this study, shear properties of geosynthetic-geosynthetic and geosynthetic-soil were evaluated from large scale direct shear tests. The cohesion and the angle of internal friction of each interface was evaluated. And laboratory model tests were performed to compare strength of reinforcement with strength of none reinforcement. As a result of this study, the cohesion and the angle of internal friction of each interface was increased, especially the cohesion was increased more than the angle of internal friction. Also according to the result of model test, the bearing capacity was increased by 20%.

• Journal of the Korean Geotechnical Society
• /
• v.20 no.9
• /
• pp.17-23
• /
• 2004

Strength and deformation characteristics of oyster shell-sand mixtures were investigated to utilize waste oyster shell being treated as a waste material. Standard penetration test (SPT) is a common method to obtain in-situ strength in sand. However, in case of oyster shell-sand mixtures, there was no information between SPT N-value and internal friction angle of mixture soils. In this paper SPT experiments from several large scaled model chamber tests and large scaled direct shear tests were carried out with varying unit weight of oyster shell-sand mixtures. Appropriate correlations were in tile study observed among N-value, unit weight and internal friction angle, which make it possible to estimate in-situ strength from SPT and the coefficient of volume compressibility from the confined compression tests to compute the settlement of oyster shell-sand mixtures.

• Journal of the Korean Geosynthetics Society
• /
• v.16 no.2
• /
• pp.55-66
• /
• 2017

The standard piezocone penetration rate of 2 cm/s is proposed in specifications regardless of soil type. However, conditions of standard Piezo Cone Penetration (CPTU) Testings in silty soils with low plasticity vary from undrained to partially drained or fully drained penetration conditions. The partially drained shear strengths of Incheon, Hwaseong and Gunsan silty soils were estimated from the analysis results of the distributions of CPTU-based shear strengths. The CPTU-based shear strengths were compared between the undrained shear strength line and the fully drained shear strength line, which were determined from approximately ${\varphi}^{\prime}=3^{\circ}$ and ${\varphi}^{\prime}=15^{\circ}$, respectively. The internal friction angles obtained from the back analysis and UU-tests tended to increase with decreasing plasticity index, which range approximately from ${\varphi}^{\prime}=2^{\circ}$ to ${\varphi}^{\prime}=14^{\circ}$. The results matchs well with CPTU-based estimation results.

• Journal of the Korean Geosynthetics Society
• /
• v.21 no.3
• /
• pp.61-69
• /
• 2022

In this study, a large-scale direct shear test was performed to evaluate the shear characteristics of the pile-soil interface according to the fines content and confining pressure conditions as a reasonable evaluation method of the pullout resistance performance of pile considering the soil conditions. It was found that the shear stress was greatly generated under the conditions of high normal stress and low fines content. In addition, the maximum shear stress was found to be rather large under the conditions of the same normal stress and fines content, when pile surface had high roughness. The internal friction angle decreased at the pile-soil interface, when the fines content in the ground increased. On the other hand, the cohesion decreased under the condition of high fines content. And the internal friction angle and cohesion were large regardless of the fines content in the model ground, when the roughness of the pile surface was high.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.9 no.5
• /
• pp.677-682
• /
• 1985

극치해석적인 상계정리를 기초로 하여, 평면변형 인발에서 발생하는 내부결함(central bursting)을 예측하기 위해 중심에서 공동(voids)을 가진 금속에 대해 비례흐름(proportional flow)과 내부결 함의 흐름을 비교하여 해석하였다. 이 결함을 촉진시키는 공정조건에 대한 판정식(criterion)을 변형경화 금속에 대해 유도하였다. 공동을 가진 금속은 공동들을 축소시키기 위해 정상적인 재 료(sound material)의 흐름과 동일 방법으로 흐를 수 있으며, 경우에 따라서는 내부결함을 확장 하기 위해 흐를 수도 있다. 본 연구에서는 다이의 경사각, 단면감소율 및 마찰 등의 어떤 공정 변수 영역에서 중심축 상에 많은 공동을 가진 변형경화 금속에서도 내부결함이 발생할 수 있다는 것이다.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.29 no.2
• /
• pp.67-76
• /
• 2017

In this study, the effect of caisson heel on the active earth pressure is investigated. Using limit analysis method, inclinations of slip surface developed above the heel with different lengths are analyzed. The shorter the heel length, the larger those of inside slip surface, however those of outside slip surface are not changed. According to the relative heel length, relationships of internal friction angle of backfill material - wall friction angle between caisson structure and backfill - friction angle acting on virtual section at the end of heel are presented. Earth pressures acting against caisson structure with relatively short heel are smaller than Rankine earth pressure but always greater than Coulomb earth pressure which does not consider the heel length.

• Journal of Korean Society of Steel Construction
• /
• v.10 no.1 s.34
• /
• pp.101-113
• /
• 1998

In this study, we research the influence of butt-welded joints in high tension bolted joints on the static and fatigue strength. As a results, if it's located inside or outside of the friction surface, the fatigue strength decrease, and the decrease of fatigue strength is greater in cases that the butt-welded joints exist outside of the friction surface. But the influence of butt-welded joint on the fatigue strength satisfies category B of the Specifications.

• Journal of the Korean GEO-environmental Society
• /
• v.18 no.2
• /
• pp.29-37
• /
• 2017

As the behavior of the debris flow due to the torrential rains in mountain is affected by shear strength and rheological properties of the fine fraction in the ground, the evaluation of both properties is necessary to estimate the behavior of the debris flow. The objective of this study is to evaluate the shear strength and rheological properties using the direct shear apparatus. The direct shear tests are conducted for two kinds of fine-grained soil specimens, which are in dry state and liquid limit state. From the direct shear tests, shear strengths are measured according to the normal stresses applied on the specimens to evaluate the cohesion and internal friction angle. In addition, reversal shear tests are performed for the fine-grained soil specimens in liquid limit state according to the shear rate to evaluate the residual shear strength. The results of direct shear tests show that the specimen at the liquid limit state has lower internal friction angle and higher cohesion compared to the dry stated, and the residual friction angle and cohesion at the residual state are lower than those at the peak state. In the result of reversal shear test, the residual shear strength is directly proportional to the shear rate and viscosity is calculated as $73.60Pa{\cdot}s$. This study demonstrates that the direct shear apparatus can be effectively used for the evaluation of the shear strength and rheological properties of the fine-grained soils related with the debris flow.

• Journal of the Korean Geosynthetics Society
• /
• v.15 no.3
• /
• pp.67-76
• /
• 2016

The railway bridge abutment subjected to the lateral earth pressure is a sensitive structure that is affected by backfill materials, installation methods, compaction, and drainage system and so on. The several design loads for the bridge abutment design consist of traffic loading on bridges and vertical & lateral force due to surcharge load at backfill. Especially, the lateral earth pressure of design load components is important and considered in the design of geotechnical engineering structure such as bridge abutment wall. The determination of cross section for abutment is finally determined with calculating external stability and member force of abutment wall structures. In this study, the abutment wall height is 12m and the optimal cross section of abutment wall has been determined that satisfies an external stability for abutment structure through friction angles of 35, 40, and 45 degrees of backfill materials. The external stability and member force of abutment wall with friction angle of backfill materials and were calculated and construction cost of each abutment wall structures was compared. It found that the construction cost was reduced from 2.2 to 8.4% with friction angle of backfill materials.

• Journal of the Korean Geosynthetics Society
• /
• v.5 no.1
• /
• pp.33-38
• /
• 2006

Large-scale direct shear tests were conducted in order to evaluate both the shear strength of crushed stone itself and the interface shear strength between crushed stone and geotextile. Total three types of geotextile (i.e. one woven geotextile and two nonwoven geotextiles) were used in the experimental program, considering two different values for the unit weight of crushed stone. Total fifteen tests were conducted in this study. It has been found from the experimental results that the friction angles of crushed stone itself were $47^{\circ}$ and $57^{\circ}$ under the unit weights of crushed stone being $1.4t/m^3$ and $1.5t/m^3$, respectively. Interface friction angle between nonwoven geotextile and crushed stone showed $39^{\circ}$ for type A indicating an efficiency of 83% and $42^{\circ}$ for type B indicating an efficiency of 89%. Similarly, interface friction angle between woven geotextile and crushed stone showed $39^{\circ}$ indicating an efficiency of 83%.