• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2010년도 추계 학술발표회 2차
• /
• pp.68-75
• /
• 2010

Around the Nakdong River which is one part of the repairing business of 4 Grand Rivers currently being constructed, sandy ground is distributed throughout the wide area. Many civil engineering structures such as small and medium sized dams, flood control basins, and redevelopment of reservoirs and retention reservoirs are scheduled to be constructed, so the prevention measures for liquefaction are surely needed. To identify such liquefaction, a lot of factor affecting the strength of liquefaction were studied through laboratory investigation. Most of the conducted study was about clean sands, but in the case of the real ground the sand can exist not in the clean conditions but in the conditions mostly including sand of fine grained soil. The sand of fine grained soil has become a significant factor to assess liquefaction because many cases of liquefaction happened in the silty and clayer soil. In this study, un-drained tests of plasticity index of fine grained particles were conducted with the sands from Nakdong River. In result, the study shows that dynamic shear strength characteristics differ according to the plasticity index.

• International Journal of Concrete Structures and Materials
• /
• 제6권1호
• /
• pp.59-64
• /
• 2012

Sand-concrete is being researched for potential usage in construction in Saharan regions of Algeria, because of shortage in coarse aggregate resources. This research work deals with the effect of dune sand, available in huge quantities in these regions, on the properties of flowing sand-concrete (FSC) prepared with different proportions of dune and river sands. Mini-cone slump test, v-funnel flow-time test and viscosity measurements were used to characterize the behaviour of FSC in fresh state. The 28-day compressive strength was also determined. Test results show that an optimal content of dune sand, which makes satisfied fresh and hardened properties of FSC, is obtained. Moreover, the obtained flow index (constant b) calculated by the help of power-law viscosity model is successfully correlated to the experimental results of v-funnel flow time.

• 한국지형학회지
• /
• 제21권4호
• /
• pp.109-120
• /
• 2014

강의 상류부에서도 사력퇴가 잘 발달한 홍천강의 상류 유역 중 하나인 두촌천 유역을 대상으로 역과 모래를 분석하였다. 이를 통해 각 구간별 사력퇴의 발달 양상과 퇴적물의 차이를 비교해 보고 상류에서 하류로 이동되는 퇴적물의 변화양상을 살펴봄으로써 소유역 내에서도 다양하게 나타나는 하천의 지형발달 특색을 파악하고자 하였다. 역 분석 결과, 하류로 갈수록 화강암과 편마암 역이 공급되면서 원마도와 편평도가 증감을 반복하는 불규칙한 변화 경향을 보였다. 모래의 입도 변화는 전체적으로 중 조립사의 비율이 매우 높았으나, 화강암 지대를 흐르는 지류 합류점이 편마암 지대 합류점에 비해 다소 입경이 증가하는 경향을 보였다.

• 한국관개배수논문집
• /
• 제21권1호
• /
• pp.118-126
• /
• 2014

In this study, the use of the spur of riverbank technique is being investigated. The spur of the riverbank typically reduces the velocity of flow and protects the embankments by increasing friction along the water and the banks. This also has an effect in the rise of water level upstream. It is also used for the rectification of riverside line and restoration of the waterway through sedimentation near the spur of the riverbank. In this study, physical-scaled experiments are conducted to investigate the process of creating a mild meandering channel using the spur of the riverbank with varying water flows and sedimentation functions. The hydraulics observations are taken with respect to the varying heights and length of the riverbank's spurs and the distance between each spur for the formation of the mild meandering channel. It is observed that for 1.06 times of the meander length, it requires 2 times of the interval with each spur of river width. Similarly, 1.25L times of the meander length, it requires 0.5 times of the interval with each spur of river width. The sand accumulation is induced by the spur of riverbank when the spur of riverbank's heights are more than 40% of water depth and the length of the spur of riverbank needs under than 20% of river width for avoid exaggerated sand accumulation in the center of channel.

• Membrane and Water Treatment
• /
• 제9권4호
• /
• pp.233-243
• /
• 2018

In this manuscript, $35m^3/d$ NF unit was designed and applied for surface water treatment of the River Nile water. Intake of Embaba drinking water treatment plant was selected to install that unit at since; it has the lowest water quality index value through the examined 6 sites in greater Cairo area. The optimized operating conditions were feed and permeate flow, 40 and $7m^3/d$, feed pressure 2.68 bar and flux rate $37.7l/m^2h$. The permeate water was drinkable according to Egyptian Ministerial decree 458/2007 for the tested parameters (physic-chemical, heavy metals, organic, algal, bacteriological and parasitological). Single and double sand filters were used as pretreatment for NF membranes but continuous clogging for sand filters moved us to use UF membrane as pretreatment for NF membrane.

• Ecology and Resilient Infrastructure
• /
• 제1권2호
• /
• pp.82-93
• /
• 2014

최근 들어 하천의 치수와 이수 그리고 환경적 측면을 고려한 '생태하천복원'이 활발히 이루어지고 있다. 그러나 개별적 특성이 뚜렷한 각각의 하천에서 그 하천을 기반으로 생활하는 생물들의 서식조건을 충분히 고려하였다고 보기는 어려운 상황이며, 제한된 공법의 사용으로 획일화된 인공하천 조성 및 관행적 하도정비에 그쳐 하도서식처가 빈번하게 교란되고 있는 것이 현실이다. 본 연구는 하천을 서식기반으로 살아가는 생물들의 서식공간에 대하여 검토한 기초적 연구로서, 국내하천을 하천특성에 따라 모래하천과 자갈하천으로 구분하고, 각 하천의 구간을 도심구간과 자연하천구간으로 나누어 각각의 서식유형을 비교 검토하였다. 그 결과, 모래하천보다는 자갈하천에서 보다 다양한 형태의 생물서식처 유형이 검토되었으며, 하천복원사업을 이미 시행한 도심하천구간에서도 생물서식처 유형이 자연하천구간에서 나타나는 생물서식처유형의 약 56.3 %정도에 머무르고 있는 것으로 나타났다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
• /
• pp.459-462
• /
• 2005

Recently, interest grew on the quality of aggregates following the diminution of primary resources from river and the growing construction demand which exhausted high-quality sand sources around large cities and incited the use of low grade aggregates like shore sand and sea sand that can be supplied in natural state. Moreover, the most sensitive aspect highlighted by the unstability of aggregate supply is the quality. The extreme insufficiency of quality criteria about the materials currently used as substitute aggregates and about concrete mixed with such materials is also critical. This study investigated influence of qualities of concrete which is using mixed crushed sand and natural sand

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
• /
• pp.352-355
• /
• 2004

Crushed sand is made by crushing the rocks artificially. With a wide shortage of natural river sand all over the region in Korea, demand for crushed sand are becoming increased. However, Informations as to crushed sand are insufficient. In this paper, the actual conditions of crushed sand related to producing and quality variation are investigated. 29 manufacturing company of crushed sand are reviewed. According to results, density of most crushed sand tested exceeded 2.5g/cm3, and absorption ratio meet the requirement of KS except one sample. For grain properties, passing amount of 0.08mm sieve satisfied the requirement of KS except one sample. Grain distribution of most crushed sand is estimated $54.26\%$. But 6 crushed sand sample did not meet the requirement of KS. Fineness modulus and grading are varied from manufacturing region. 18 samples of crushed sand among 29 samples deviated the minimum level of standard grading range by KS. Therefore, improvement of grain properties of crushed sand is urgently needed to manufacture better crushed sand.

• 한국해양공학회지
• /
• 제22권2호
• /
• pp.28-33
• /
• 2008

From the 1997 to January, 2004, a groin 156m long was constructed at the mouth of the Heoya river-mouth as a protection and barrier. To understand the changes to Jinha beach from the blockade of the river mouth, several aerial photographs, etc., were compared, which showed that the changes were significant. Comparing these results to the state of the area before construction of the groin, the blockade of the river was relaxed, but the formation of the tombolo, in the middle groin area was accelerated and the total Jinha beach erosion and especially the erosion of the southern part of Jinha beach was developed. But according to statements by residents and some current documents, the blockade of the Heoya-river mouth is still underway at the surrounding areas of the groin and chronic dredged sand has been used for littoral nourishment at the northern part of the middle groin and on Jinha beach. The result of numerical simulation based on the present state shows that if this sort of dredging is stopped, the sand accumulation will progress near the river mouth groin and the existing tombolo at the middle groin will progress to the north and severe erosion will occur at the southern coastline near the middle groin and the farthest southern part of Jinha beach, and Jinha beach itself will experience a gradual erosion. The main reason for these erosions should be the typhoons that are happening during the summer season. To provide protection from these kinds of undesirable erosions, a total of 23 numerical simulations have been done. It has been shown that submerged breakwaters at the front area of the beach will be efficient to protect from main beach erosion, but there should be alternative proposals for the influence of the river mouth blockade.

• Structural Engineering and Mechanics
• /
• 제69권6호
• /
• pp.627-635
• /
• 2019

In order to study the axial compression performance of sand-lightweight concrete-filled steel tube (SLCFST) stub columns, three circular SLCFST (C-SLCFST) stub column specimens and three SLCFST square (S-SLCFST) stub column specimens were fabricated and static monotonic axial compression performance testing was carried out, using the volume ratio between river sand and ceramic sand in sand-lightweight concrete (SLC) as a varying parameter. The stress process and failure mode of the specimens were observed, stress-strain curves were obtained and analysed for the specimens, and the ultimate bearing capacity of SLCFST stub column specimens was calculated based on unified strength theory, limit equilibrium theory and superposition theory. The results show that the outer steel tubes of SLCFST stub columns buckled outward, core SLC was crushed, and the damage to the upper parts of the S-SLCFST stub columns was more serious than for C-SLCFST stub columns. Three stages can be identified in the stress-strain curves of SLCFST stub columns: an elastic stage, an elastic-plastic stage and a plastic stage. It is suggested that AIJ-1997, CECS 159:2004 or AIJ-1997, based on superposition theory, can be used to design the ultimate bearing capacity under axial compression for C-SLCFST and S-SLCFST stub columns; for varying replacement ratios of natural river sand, the calculated stress-strain curves for SLCFST stub columns under axial compression show good fitting to the test measure curves.