• Journal of Korean Society of Environmental Engineers
• /
• v.37 no.7
• /
• pp.412-417
• /
• 2015

This study investigated to recycle geobond and ash produced in thesewage sludge incinerator using reduction/stabilization. Nonsintering process was performed by binding cement (High Early Strength Portland cement, Micro cement), geobond and sand mixed with sewage sludge ash (SSA). Chemical ingradients of the sewage sludge ash was mainly composed of $SiO_2$, $Al_2O_3$, $Fe_2O_3$, CaO and others, which were similar to those of the each binders consisting High Early Strength Portland cement, Micro cement and geobond. Results showed that unconfined the long term compressive strength could be obtained components of sewage sludge ash. It exceeded more than double score 64.6 MPa of the Korean standard ($22.54MPa=229.7kg/cm^2$). Microstructure of solidified block for the different admixture was related to the compressive strength according to SEM analysis. Optimum mixing range of the sewage sludge ash to each binders were found to be 10~40% which can widly safely regulate the confined a long term compressive strength. The best binder of long term compressive strengh was revealed Geobond more than High Early Strength Portland cement and Micro cement. This study revealed the sewage sludge ash can be partial replacement of the inorganic binder & application block for recycling.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.03a
• /
• pp.1332-1343
• /
• 2008

The purpose of this study was to investigate the feasibility of using sedimentation calcium carbonate production based on microorganism activities in the strength manifestation of various soil conditions including ground. For analysis and comparison of microbial cementation soil's strength, unconfined compression test was executed by each content of soil(S), water(W), microorganism(B), microorganism and deposit (BF), microorganism, admixture and deposit(BCF) at specimen. The result, the strength of SB(soil+microorganism) and SBF(soil+microorganism+deposit) increased about 8%, 15% than SW(soil+water). Also, initial strength increased. But the strength of SBC(soil+microorganism+admixture) and SBCF(soil+microorganism+deposit+admixture) increased about 71%, 115% than SW(soil+water). The results of the SEM analysis, leading to the formation of an adhesive substance layers at the surface and resulting in firm particle configuration. The XRD examination of the sediment resulting from the reaction between the microorganism and the deposit control agent confirmed the presence of a type of calcium carbonate ($CaCo_3$) vaterite, which affects soil strength formation, as well as sodium silicate, silicides and so forth. This indicates that microorganism plays an important role in the production of carbonate ($CaCo_3$), sodium silicate and silicides. It affects to revelation of ground strength.

• Journal of the Korean Geosynthetics Society
• /
• v.6 no.3
• /
• pp.1-7
• /
• 2007

The property of weathered soil cannot but have a possibility of having a limit when its precise approaching due to the various weathering environment, and the peculiarity of its conduct affected by the weathering degree and effect factors. Especially most domestic or international researches are concentrated on the sedimentary soil, trying to analyze the mechanical behavior of weathered soil from the viewpoint of sedimentary soil. Therefore, it's difficult to judge if those results meet the actual conduct of weathered soil. This study suggested a way of weathering degree changing experiment as an early stage in an experiment of artificially changing weathering degree. In order to find out the property of strength change by the change of weathering degree, indoor mechanical experiment was made using soil sample after freezing and thawing. Under the weathering degree, characteristic change is watched by country rock and region of weathered granite soil.

• Geomechanics and Engineering
• /
• v.12 no.5
• /
• pp.803-813
• /
• 2017

This study discussed the possible optimization of enzyme-mediated calcite precipitation (EMCP) as a soil-improvement technique. Magnesium chloride was added to the injection solution to delay the reaction rate and to improve the homogenous distribution of precipitated minerals within soil sample. Soil specimens were prepared in 1-m PVC cylinders and treated with the obtained solutions composed of urease, urea, calcium, and magnesium chloride, and the mineral distribution within the sand specimens was examined. The effects of the precipitated minerals on the mechanical and hydraulic properties were evaluated by unconfined compressive strength (UCS) and permeability tests, respectively. The addition of magnesium was found to be effective in delaying the reaction rate by more than one hour. The uniform distribution of the precipitated minerals within a 1-m sand column was obtained when 0.1 mol/L and 0.4 mol/L of magnesium and calcium, respectively, were injected. The strength increased gradually as the mineral content was further increased. The permeability test results showed that the hydraulic conductivity was approximately constant in the presence of a 6% mineral mass. Thus, it was revealed that it is possible to control the strength of treated sand by adjusting the amount of precipitated minerals.

• Journal of Ocean Engineering and Technology
• /
• v.21 no.2 s.75
• /
• pp.60-66
• /
• 2007

The first Korean cold room facility for ice mechanics experiments was assembled in 2004. Since then, the $4m{\times}6m$ cold room facility has been used, extensively under various environmental and loading conditions. After reviewing published references on cold room testing methods and also by trial and error, the standard procedures for testing and preparing laboratory ice material were established for the measurement of basic ice properties. In this paper, laboratory experimental techniques with the cold room facility and standard procedures established for ice material properties are introduced. Test specimens include laboratory-grown fresh water ice and frozen soils. Tests are carried out for unconfined compressive strength. Preparation and dimension of the specimen are the most important issues arising in cold room tests. The details of specimen preparation, testing procedure and strength test results are also discussed.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.10a
• /
• pp.395-404
• /
• 2005

This study is to evaluate the physical and mechanical characteristics of flowable backfill and search for the optimal mixture contents of it used for constructing underground power utilities. flowable backfill is known as soil-cement slurry, void fill, and controlled low-strength material(CLSM). The benefits of CLSM include reduced equipment costs, faster construction, re-excavation in the future, and the ability to place material in confined spaces such as narrow parts nearly impossible for compaction or perimeter of underground power cables. The flowable slurry mixture made with 9 types of soil and 6 types of accelerated mixtures in the laboratory were evaluated for bleeding, flowability, heat resistance, and unconfined compressive strength to meet the aim values of this study.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.03a
• /
• pp.821-832
• /
• 2008

The hazard warning levels are necessary for the rational design and safety construction of underground space, as mountain and urban tunnel. Sakurai provided the hazard warning levels for assessing the stability of tunnels using the critical strain of rock mass, which is defined as a ratio between uni-axial compressive strength and the Young's modulus. The concept of critical strain guidelines is introduced in this study for the assessment of tunnel safety during excavation. Moreover, in this paper, the critical strain properties of sedimentary rock in Korea has investigated and analysed in detail by Lab. test, as the uniaxial and triaxial compression tests. Finally, critical strain properties of sedimentary rock on uniaxial and triaxial stress condition is discussed the relationship of failure strain values, uniaxial and triaxial compression strengths, confining pressure and Young's modulus.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.43 no.6
• /
• pp.127-134
• /
• 2001

In order to expand agricultural lands in the western and southern coasts of Korean Peninsula, coarse soils excavated from hillsides have been used as fill materials for reclamation. In order to tackle with the problems and to confirm availability, research on soil improvement involve mixing cement to the fine wet soils. Required undrained shear strength$(C_u)$ for fill material was analysed to be 0.34~1.2 $kgf/cm^2$. It has been known that when cement is added to high water content marine clay its unconfined compression strength increased to 2 $kgf/cm^2$. Consolidation results show that pre-consolidation pressure increased to 1.8 $kgf/cm^2$and 3.4 $kgf/cm^2$ with the addition of 3% and 5% of cement respectively. This result shows that low-height embankments could be constructed without significant compression. Since the effectiveness of improvement may be different site by site, the mix design for each site is necessary in order to optimize it. The process is first to determine aimed shear strength and then optimum mix ratio of cement after carrying out a series of tests.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.10 no.11
• /
• pp.3296-3301
• /
• 2009

The results of PCPT(Pezocone Penetration Test) are widely used for the estimation of the undrained shear strength, for which the empirical cone factors($N_{kt}$, $N_{ke}$, $N_{{\Delta}u}$) need to be obtained at each site. In this study, the cone factors were estimated, for the soils at Bookmyun area in Changwon city, using the undrained shear strengths from the unconfined and UU triaxial compression tests. The parametric studies with plastic index and pore water pressure ratio were performed as well. $N_{kt}$, $N_{ke}$ and $N_{{\Delta}u}$ were estimated in the ranges of 8~40, 7~37, and 1~26 respectively. It was observed that there is a relationship between the cone factors, specially $N_{{\Delta}u}$, and the pore pressure ratio.

• Geomechanics and Engineering
• /
• v.2 no.4
• /
• pp.321-335
• /
• 2010

This article describes a laboratory research on stabilizing tropical peat using ordinary Portland cement (OPC) as a binding agent, and polypropylene and steel fibres as chemically inert additives. California bearing ratio (CBR) and unconfined compressive strength (UCS) tests were carried out to evaluate the increase in the strength of the stabilized samples compacted at their optimum moisture contents and air cured for up to 90 days. The results show that the UCS values of stabilized peat samples increased by as high as 748.8% by using OPC (5%), polypropylene fibres (0.15%), and steel fibres (2%). The CBR values of the samples stabilized with OPC (5%), polypropylene fibres (0.15%), and steel fibres (4%) showed an increase of as high as 122.7%. The stabilized samples showed a shrinkage in volume upon air curing and this shrinkage was measured by an index called, volume shrinkage index (VSI). The highest VSI recorded was 36.19% for peat without any additives; and the minimum was 0% for the sample containing 30% OPC, 0.15% polypropylene fibres and 2% steel fibres. The technique of stabilizing peat with OPC, polypropylene and fibres, coupled with air curing, appears to be cost-effective compared with other frequently used techniques.