• Journal of the Korean Geotechnical Society
• /
• v.16 no.2
• /
• pp.31-39
• /
• 2000

Hansbo는 인공 배수재에 대한 압밀 이론에서 스미어죤의 교란부분에 대한 불교란부분의 투수곗의 비(kh/ks)가 일정하다고 가정하였다. 그러나 실험결과에 의하면 투수계수비는 배수재로부터의 거리 및 압밀 진행에 따라서 변한다. 본 논문에서는 정규압밀조건에서 압밀진행동안의 스미어죤내 투수계수변화에 대한 경험공식을 유도하고 이를 고려할 수 있는 압밀해석방법을 제안하였다. 실제 압밀시험과 투수시험자료를 이용하여 제안한 해석방법으로 해석된 결과와 Hansbo의 이론을 비교하였다. 배수재 주위의 흙과 교란이 크거나 필터가 막혀서 투수계수가 원래의 값보다 현저히 저하되는 경우에는 실제의 압밀은 Hansbo의 이론으로 계산한 것보다 훨씬 지연된다는 사실을 알게 되었다.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.26 no.1
• /
• pp.79-89
• /
• 2024

Excessive inflow of groundwater during tunnel excavation not only affects the stability and constructability of the tunnel, but is also one of the main causes of ground settlement due to groundwater level drawdown. The most commonly applied measure against excessive groundwater inflow during tunnel excavation in soil or fractured zone is to reduce the ground permeability coefficient by injecting grout material. Generally, the grouting area is assumed to be same as the plastic zone that occurs during tunnel excavation, but injecting grout material in the area of plastic zone is appropriate only for reinforcement grouting. In order to determine the thickness of cutoff grouting, the amount of reduction in the water permeability coefficient due to the application of cutoff grouting must be considered. In this study, a method for estimating the range of cutoff grouting considering the reduction in permeability coefficient was mathematically derived and evaluated through computer numerical analysis.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.03a
• /
• pp.946-950
• /
• 2010

급속한 산업화와 도시화는 도시지역 불투수 지표면적의 대부분을 차지하고 있는 도로포장면의 증가를 가져왔으며, 이것은 강우의 급속한 배수를 유발하여 도시홍수를 발생시키고 우수의 지표면 침투 저하로 인한 지하수위의 저하와 용수의 고갈 등 생태계의 불균형과 도시지역의 열섬현상과 같은 환경문제의 주요인으로 지목되고 있다. 불투수층 포장체로 인하여 왜곡되어 있는 국내 물순환 시스템의 개선 방안으로 실험에 의한 투수성 포장체의 처짐량 및 투수계수를 측정하였다. 투수성 포장을 모의하도록 수정 개발된 SWMM을 이용하여 대상지구 내 우수저감효과를 분석하였다. 투수성 포장 설치가 건기 하천유출량과 우수유출에 어떤 영향을 미치는지 연속유출모의를 수행하였다. 1997년부터 2007년까지 투수성 포장 설치 전 후의 물순환 분석결과 유출률 및 침투율은 각각 81.38 %, 74.35 %와 8.32 %, 15.13 %로 산정되었다. 대상지구의 투수성 포장의 설치로 유출량은 감소, 침투량은 증가하는 것으로 나타났다.

• Resources Recycling
• /
• v.19 no.4
• /
• pp.35-40
• /
• 2010

Existing porous concrete has problems with reduction of strength due to freezing and thawing and exfoliation of aggregate at joints. In this study, a method for increasing strength and durability of porous concrete by using fine aggregate, silica-fume and high-range water-reducing agent was proposed by laboratory tests. Mixing ratio between silica-fume (10%) and fine aggregate (0%, 7%, 15%) was selected as a major test factor, and laboratory tests for compressive strength, flexural strength, permeability coefficient, porosity, freezing and thawing were conducted. Compressive strength and flexural strength were increased as the mixing ratio of fine aggregate was increased. However, permeability and freezing-thawing resistance were decreased due to reduction of porosity. Therefore, the ratio of fine aggregate should be limited to increase strength and durability of the porous concrete, while the mixing ratio of silica-fume should be over 10%.

• Journal of the Korea Concrete Institute
• /
• v.14 no.1
• /
• pp.41-48
• /
• 2002

In this paper, permeable polymer concretes with unsaturated polyester or vinylester resin content from 5 to 8 weight ％, resin-filler ratio of 1 : 1, sand content from 0 to 15 weight ％ and crushed stone of size 2.5∼10 mm were prepared, and tested for compressive strength, flexural strength and water permeability. The effects of the resin and sand contents on the properties of permeable polymer concrete were discussed. It is concluded from the test results that increase in the strength and decrease in the coefficient of permeability of the permeable polymer concrete arc clearly observed with increasing the resin and sand contents. The permeable polymer concrete showed compressive strength in the range of 170 to 350 kgf/$\textrm{cm}^2$ and flexural strength in the range of 40 to 90 kgf/$\textrm{cm}^2$ at coefficient of permeability from 0.1 to 1.0 cm/sec in this experiment.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.31 no.3D
• /
• pp.413-420
• /
• 2011

An experiment was conducted to suggest the road pavement material combining wooden chip crushed from little useful roots and branches from logging sites or wood waste from construction sites with urethane resin. For the specimen, the mass ratio of urethane resin to construction wood waste chip/lumber waster chip was set to three different levels of 0.5, 0.75, and 1.0, which was measured, mixed with mixer, and molded; 7 days after, tensile strength test, elasticity test using golf balls and steel balls, permeability coefficient measurement, and flammability test were executed. As the result, the tensile strength of the specimen at the dry state in the air exhibited the range of 0.2-1.1MPa, and there was no change after 7 days of aging. When submerged in water, however, the strength was partially diminished; the diminishing rate was greater for less urethane resin usage, and therefore it appears desirable to set the mass ratio of resin to the wood waste chip over 0.75 to consider the moisture intrusion by precipitation and such. As the result of elasticity test, the GB and SB coefficients of the specimen using wood waste chips and urethane resin were measured to be low at below 20%, exhibiting excellent elasticity as road pavement material. Also, the permeability coefficient was over 0.5mm/sec for specimens of all combinations, exceeding the standard value required after construction for permeable pavement material, and the flammability of wood-type pavement material was evaluated to have no practical issues.

• Journal of the Korean Geotechnical Society
• /
• v.26 no.4
• /
• pp.15-26
• /
• 2010

To determine the frost heave suppressing mechanism of soil mixed with tire powder, we conducted three kinds of laboratory experiments: measurement of unfrozen water, evaluation of thermal conductivity, and a frost heave. In this research, we focused on changes in the coefficient of permeability of the mixed soil, and first found that of the unsaturated soil. Next, in the case of the presence of ice, we took the ice-impeding factor into consideration to derive the coefficient of permeability of the frozen fringe from the area ratio of the soil and tire powder in mixed soil. The results show a positive correlation between the water intake rate and the coefficient of permeability. Moreover, we found that the frost heave decreased thanks to a reduction in the permeability and a fall in the unfrozen water content of the soil mixed with tire powder. We also calculated the weight of the water content of the soil and tire powder void quantitatively using the result of the volumetric ratio of mixed soil.

• Journal of the Korean GEO-environmental Society
• /
• v.13 no.8
• /
• pp.85-94
• /
• 2012

Evaluation of the smear effect caused by mandrel penetration into soft ground for a vertical drain installation is very important to predict the consolidation time of soft ground improvement. 30 kinds of laboratory model tests considering in situ conditions were conducted to investigate the formation of a smear zone and the decrease of coefficient of permeability in the disturbed zone. Three types(C(clay):M(silt)=1:1, 0.5:0.5, and 0:1) of reconstituted samples were used for 3 dimensional smear zone test. An experimental study was performed focusing on length of mandrel penetration, mandrel shape and size, earth pressure, and ground condition(unit weight and grain size distributions). Laboratory test results show that the length of mandrel penetration is the most critical factor for the formation of smear zone. As a result, the ratio between diameter of the smear zone($d_s$) and that of mandrel($d_m$) at field using long mandrel becomes larger than conventional $d_s/d_m$. The ratio between $d_s$ and $d_m$ ranges from 1.89 and 2.48 with the sample at C:M=1:0. It was also found that the $d_s/d_m$ value with the round shape of the mandrel is smaller than that of diamond one. The value of $d_s/d_m$ decreased with larger mandrel size, lower unit weight, and higher earth pressure. However, higher silt content led to increase of $d_s/d_m$. The ratio between coefficient of horizontal permeability in the smear zone($k_{hs}$) and that of undisturbed zone($k_{ho}$) ranged from 0.70 to 0.85. The test results imply that factors and values affecting $k_{hs}/k_{ho}$ show similar tendency with $d_s/d_m$.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.11 no.2
• /
• pp.87-92
• /
• 2011

This paper describes a study on the permeability reduction of the riverbed ground during urban railway tunnel construction. The research is mainly concentrated on the study of the grouting or injection methods among permeability reduction methods which can be adapted in the riverbed ground. The design technology of grouting methods considering the long term hydro-geological behaviour in the riverbed, was suggested. Two injection methods namely, Natural Durable Stabilizer (N.D.S) and Space-Multi Injection Grouting (S.M.I) methods, were introduced as new approach methods which could be adapted to modify the riverbed ground. In order to evaluate the performance of the improved ground by the N.D.S and S.M.I method, a series of pilot tests including the field and laboratory permeability tests, were carried out in the river crossing tunnel construction sites. The results obtained from pilot test program, were also reviewed. The results, the grouting efficiency of the S.M.I method using the non-alkalimeter silica sol is better than that of N.D.S method using cement. In addition, it is anticipated that the current research results are contributed to develop the grouting design technology.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.9 no.3
• /
• pp.87-92
• /
• 2005

The permeability of concrete affects largely on the durability of concrete, therefore it is required that the correct assessment and improvement of permeability. Therefore it is rational method that the permeability of concrete structures is estimated in the common use states under loading than in the early sound conditions. In this study, to improve the permeable efficiency of concrete, some kinds of fiber and resin are mixed in making of concrete specimens. And also, for the reasonable assessment of permeability, after 50% and 70% pre-loadings of its compressive strength were acted on the specimens, the tests were executed. From the results of this study, in the case of 50% pre-loading coefficients of permeability were increased about 1.4times against the nonpre-loading specimens and in the case of 70% pre-loading they were increased about 17.8times. And it turned out that hybrid steel fiber reinforcement is most effective for the improvement of permeable efficiency of concrete.