• 제목/요약/키워드: in-situ compressive strength

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Friction behavior of controlled low strength material-soil interface

  • Han, WooJin;Kim, Sang Yeob;Lee, Jong-Sub;Byun, Yong-Hoon
    • Geomechanics and Engineering
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    • v.18 no.4
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    • pp.407-415
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    • 2019
  • A controlled low strength material (CLSM) is a highly flowable cementitious material used for trench backfilling. However, when applying vertical loads to backfilled trenches, shear failure or differential settlement may occur at the interface between the CLSM and natural soil. Hence, this study aims to evaluate the characteristics of the interface friction between the CLSM and soils based on curing time, gradation, and normal stress. The CLSM is composed of fly ash, calcium sulfoaluminate cement, sand, silt, water, and an accelerator. To investigate the engineering properties of the CLSM, flow and unconfined compressive strength tests are carried out. Poorly graded and well-graded sands are selected as the in-situ soil adjacent to the CLSM. The direct shear tests of the CLSM and soils are carried out under three normal stresses for four different curing times. The test results show that the shear strengths obtained within 1 day are higher than those obtained after 1 day. As the curing time increases, the maximum dilation of the poorly graded sand-CLSM specimens under lower normal stresses also generally increases. The maximum contraction increases with increasing normal stress, but it decreases with increasing curing time. The shear strengths of the well-graded sand-CLSM interface are greater than those of the poorly graded sand-CLSM interface. Moreover, the friction angle for the CLSM-soil interface decreases with increasing curing time, and the friction angles of the well-graded sand-CLSM interface are greater than those of the poorly graded sand-CLSM interface. The results suggest that the CLSM may be effectively used for trench backfilling owing to a better understanding of the interface shear strength and behavior between the CLSM and soils.

The Method of Certificating Waterproof Effect for Consecutive Column-Wall Mass in Underground (주열식 지중연속벽체의 차수효과 확인 방안)

  • Koh, Yong-IL
    • Journal of the Korean GEO-environmental Society
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    • v.18 no.9
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    • pp.5-9
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    • 2017
  • On the flow of groundwater, the effect of consecutive column-wall in underground as a hydraulic barrier could be identified by conventional geotechnical methods ((1)visualiy identification of wall mass after underground excavating, (2)uniaxial compressive strength test for core of wall mass in underground, (3)in-situ permeability test in the hole after coring wall mass). However, for the cut off the leakage or infiltration of very high concentrated leachate from the waste landfill or the contaminated groundwater, the waterproof effect of consecutive column-wall in underground should be verified more objectively, by in-situ measuring of pH, temperature and salinity. and by evaluating of their consistency and similarity throughout analyzing the characteristics of basic components and their profiles through the series of chemical experiments. Furthermore, its waterproof effect could be verified additionally throughout deciding the similarity more simply by comparing the general distribution patterns including the difference of high and low peaks from the chromatograms using GC-MS for surrounding groundwater.

Bearing Capacity of Cast-in-situ Concrete Piles Socketed in Completely Weathered Gneiss (풍화암에 근입된 현장타설말뚝의 지지거동 분석)

  • 전경수;김정환;김명모
    • Journal of the Korean Geotechnical Society
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    • v.15 no.6
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    • pp.155-165
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    • 1999
  • In completely weathered granite gneiss,8 of 40cm cast-in-situ concrete piles are constructed, and static pile load tests are executed on the piles to study the bearing behavior of rock-socketed piles. Subsurface explorations are carried out on the test site in three phases, in which 14 borehole investigations as well as the seismic investigation are performed. Rock socketd depths of the piles in the weathered rocks are varied as 3m, 6m and 9m to separate the shaft resistance from the end bearing resistance, and for a couple of piles, styrofoam of 10cm thickness is installed under the pile point to eliminate the effect of the end resistance. Strain gages are instrumented on re-bars to pick-up the transferred loads along the pile length. From the results of the pile load tests, the allowable shaft resistance and the allowable end bearing values of weathered rocks are proposed as $8.6t/m^2\;and\; 84t/m^2$, respectively. The empirical equation relating the elastic modulus of rock mass with the uniaxial compressive strength of the rock specimen is also proposed for the weathered rocks.

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Shear Load-Transfer Function of Rock-Socketed Drilled Shafts Considering Borehole Roughness (굴착면 거칠기를 고려한 암반 근입 현장타설말뚝의 주면 하중전이함수 제안)

  • Seol, Hoon-Il;Woo, Sang-Yoon;Han, Keun-Taek;Jeong, Sang-Seom
    • Journal of the Korean Geotechnical Society
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    • v.22 no.7
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    • pp.23-35
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    • 2006
  • Shear load transfer characteristics of rock-socketed drilled shafts were analyzed. The constant normal stiffness (CNS) direct shear tests were performed to identify the major influencing factors of shaft resistance, i.e., unconfined compressive strength, borehole roughness, normal stiffness, initial confining stress, and material properties. Based on the CNS tests, shear load transfer function of drilled shafts in rocks is proposed using borehole roughness and the geological strength index (GSI), which indicates discontinuity and surface condition of rock mass in Hoek-Brown criterion (1997). The proposed load-transfer function was verified by the load test results of seven rock-socketed drilled test shafts subjected to axial loads. Through comparisons of the results of load tests, it is found that the load-transfer function by the present study is in good agreement with the general trend observed by in situ measurements, and thus represents a significant improvement in the prediction of load transfer of drilled shafts.

Estimation of elastic and plastic zones near a tunnel considering in situ rock mass conditions and the damage induced by excavation (원지반의 암반조건과 시공으로 인한 손상을 고려한 터널주변 탄·소성영역의 산정)

  • Sagong, Myung;Paik, Kyuho
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.6 no.3
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    • pp.227-235
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    • 2004
  • Tunneling in rock mass produces two types of damages in the vicinity of a tunnel: structural and constructional damages. Structural damage represents the damage induced by the unbalance of geostatic stress caused by the tunneling, and constructional damage is the damage produced during the construction. In this study, formulations of tangential and radial stresses in the elastic and plastic zones near a tunnel, and the calculation of radius of plastic zone surrounding a tunnel are introduced by modifying the Hoek-Brown criterion of 2002 edition, which has capability of considering in situ rock mass characteristics and construction damage. From the parametric study, influences of rock mass quality, uniaxial compressive strength of intact rock, and the dimension of the tunnel on the plastic zone are investigated. The accuracy of the proposed approach is evaluated by comparing with results from the previous study.

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A Feasibility Study on the Polymer Solidification of Evaporator Concentrated Wastes (폐액증발기 농축폐액 폴리머고화 타당성 연구)

  • Yang, Ho-Yeon;Kim, Ju-Youl
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.5 no.4
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    • pp.297-308
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    • 2007
  • The granulation equipment of concentrated wastes is manufactured for the polymer solidification of concentrated wastes. It uses liquid sodium silicate as a granulating agent for the granulating of dried powder containing boric acid. The granulating agent is sprayed in the form of droplet and mean size of dried granules is $2{\sim}4mm$. The new technology which has been used for the polymer solidification of spent resin in U.S. and certified by Nuclear Regulatory Commission (NRC) is successfully applied to concentrated wastes. This uses in-situ solidification process within drum without mechanical mixing. Maximum loading of waste can be achieved without increasing of waste volume. Polymer waste forms were evaluated with several test such as fire test, compressive strength test, leaching test, immersion test, irradiation test, and thermal cycling test according to standard test procedures.

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The Physical Properties Variation of Grout Materials and Improvement of Grouting Effects on Application of High Performance Injection Equipment (고성능 주입장비의 적용에 따른 주입재의 물성변화 및 주입효과 증진에 관한 연구)

  • 천병식;김진춘;김백영
    • Journal of the Korean Geotechnical Society
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    • v.19 no.4
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    • pp.179-190
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    • 2003
  • The grout based on solution type makes it difficult to get the improvement of ground strength and the effefct of water curtain because it has lower strength and durability than suspension type. Nowadays, the technology of particle acceleration, that enhance the material permeability, such as grout based on solution type, and inexpensive grout, is being required. For these reasons, in this study, using wet milling system, we evaluated physical properties of manufactured factors such as water-cement ratio of particles before being milled, optimum milling capacity by controlling milling time and rpm, viscosity of materials, permeation coefficient, and unconfined compressive strength. Also, using micro wet milling apparatus which could manufacture ordinary Portland cement and high speed shear mix which could forcefully separate conglomerate particles in situ, we performed electrical resistivity investigation and falling head permeability tests to analyze differences of grouting effects. From these results, we found that the permeability of the applied equipment was much superior, and in the case of using high speed shear mixer, particles of grout material were well separated.

Side Shear Resistance of Drilled Shafts in Rock (암반에 근입된 현장타설말뚝의 주면지지력)

  • Kwon, Oh-Sung;Kim, Byung-Chul;Kim, Myoung-Mo
    • Proceedings of the Korean Geotechical Society Conference
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    • 2005.03a
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    • pp.611-618
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    • 2005
  • In this research, the effect of rock mass weathering on the side shear resistance of drilled shaft socketed into weathered rock was investigated. For that, a database of 23 cast-in-place concrete piles with diameters varying from 400mm to 1,500mm were socketed into weathered igneous/meta-igneous rock at four different sites. The static axial load tests were performed to examine the resistant behavior of the piles, and a comprehensive field/laboratory testing program at the field test site was also performed to describe the in situ rock mass conditions quantitatively. No correlation was found between the compressive strengths of intact rock and the side shear resistance of weathered/soft rock. The ground investigation data regarding the rock mass conditions (e.g. $E_m,\;E_{ur},\;_{plm}$, RMR, RQD, j) was found to be highly correlated with the side shear resistance, showing the coefficients of correlation greater than 0.7 in most cases. Additionally, the applicability of existing methods for the side shear resistance of piles in rock was verified by comparison with the field test data. The existing empirical relations between the compressive strength of intact rock and the side shear resistance(Horvath (1982), Rowe & Armitage(1987) etc.) appeared to overestimated the side shear resistance of all piles tested in this research unless additional consideration on the effect of rock mass weathering or fracturing was applied. The existing methods which consider the effect of rock mass condition were modified and/or extended for weathered rock mass where mass factor j is lower than 0.1, and RQD is below 50%.

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An Analysis of Poisson's Ratio Behaviors by Uniaxial Compressive Loading-reloading Test - On the Sedimentary Rocks of Kyungsang Basin - (일축압축 하에서 반복재하에 따른 포아송비의 거동분석 - 경상분지 퇴적암을 대상으로 -)

  • Lee, Jong-Suok;Moon, Jong-Kyu;Choi, Woong-Eui
    • Tunnel and Underground Space
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    • v.23 no.1
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    • pp.66-77
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    • 2013
  • This paper deals with Poisson's ratio and volumetric strain behavior on loading-reloading terms under uniaxial condition targeting 404 individual rocks, which include sedimentary rocks as sandstone, shale, mudstone, conglomerate and tuff on Kyungsang basin. Poisson' ratio demonstrates increase, convergence and decrease behavior according to the increase in load, which results in preponderance of increase behavior. Volumetric strain demonstrates normal, positive and negative behavior according to the increase in load, which results in preponderance of normal behavior. On practice, Poisson's ratio can be indicative of high or low values with low values of design load. Consequently, a careful selection of results in in-situ sample experiment should be made and varying design conditions should be considered.

Mechanical Properties of Fault Rocks in Korea

  • Seo, Yong-Seok;Yun, Hyun-Seok;Ban, Jae-Doo;Lee, Chung-Ki
    • The Journal of Engineering Geology
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    • v.26 no.4
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    • pp.571-581
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    • 2016
  • To understand the mechanical properties of fault rocks, data from 584 in situ and laboratory tests on fault rocks from 33 tunnels were analyzed. The unit weights of the fault rocks range from 17.3 to $28.2kN/m^3$ and the cohesion and friction angles vary from 5 to 260 kPa and $14.7^{\circ}$ to $44.0^{\circ}$, respectively. The modulus of deformation and elasticity were generally < 200 MPa. In most cases, the uniaxial compressive strength was < 0.5 MPa, and Poisson's ratios were mainly 0.20-0.35. The mechanical properties of individual rock types were analyzed using box plots, revealing that the cohesion values and friction angles of shale and phyllite have relatively wide inter-quartile ranges and that the modulus of deformation and elasticity of shale have the lowest values of all rock types. In the analysis of mechanical properties by components of fault rocks, the largest values were shown in damage zones of individual rock types.