• Title/Summary/Keyword: Uniaxial Compression Strength

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Field Testing Methods on Early Shotcrete Strength for Tunnel Quality Control (터널의 품질관리를 위한 숏크리트 초기강도의 현장강도 시험기술)

  • Hong, Eui-Joon;Chang, Seok-Bue;Lee, Sung-Woo;Kim, Ki-Lim;Moon, Sang-Jo
    • Proceedings of the KSR Conference
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    • 2007.05a
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    • pp.468-476
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    • 2007
  • Generally, the strength of the field shotcrete is heavily dependent on the field mixing and spraying conditions so that it is different from the strength of the shotcrete mixed in laboratories. As a support member, the early strength of shotcrete unlike concrete as structural material is very important to the initial stabilization of the excavation face in tunnels. Therefore, the field methods to efficiently test the early strength of shotcrete have been highly required. This paper aimed to verify the pneumatic pin penetration test and the point load test for measuring the early strength of the field shotcrete. Through a series of uniaxial compression, pin penetration, and point load tests for the range of the early shotcrete strength, two equations to estimate reliably the uniaxial compressive strength by the pin penetration and the point load tests were derived. Field tests in working tunnel were carried out in order to estimate the economic efficiency. As a result, pin penetration method was proved to be the most effective method for testing the early strength of the field shotcrete.

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Effects of interface angles on properties of rock-cemented coal gangue-fly ash backfill bi-materials

  • Yin, Da W.;Chen, Shao J.;Sun, Xi Z.;Jiang, Ning
    • Geomechanics and Engineering
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    • v.24 no.1
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    • pp.81-89
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    • 2021
  • Uniaxial compression tests were conducted on sandstone-CGFB composite samples with different interface angles, and their strength, acoustic emission (AE), and failure characteristics were investigated. Three macro-failure patterns were identified: the splitting failure accompanied by local spalling failure in CGFB (Type-I), the mixed failure with small sliding failure along with the interface and Type-I failure (Type-II), and the sliding failure along with the interface (Type-III). With an increase of interface angle β measured horizontally, the macro-failure pattern changed from Type-I to Type-II, and then to Type-III, and the uniaxial compressive strength and elastic modulus generally decreased. Due to the small sliding failure along with the interface in the composite sample with β of 45°, AE events underwent fluctuations in peak values at the later post-peak failure stage. The composite samples with β of 60° occurred Type-III failure before the completion of initial compaction stage, and the post-peak stress-time curve initially exhibited a slow decrease, followed by a steep linear drop with peaks in AE events.

Mechanical behavior of sandstones under water-rock interactions

  • Zhou, Kunyou;Dou, Linming;Gong, Siyuan;Chai, Yanjiang;Li, Jiazhuo;Ma, Xiaotao;Song, Shikang
    • Geomechanics and Engineering
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    • v.29 no.6
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    • pp.627-643
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    • 2022
  • Water-rock interactions have a significant influence on the mechanical behavior of rocks. In this study, uniaxial compression and tension tests on different water-treated sandstone samples were conducted. Acoustic emission (AE) monitoring and micro-pore structure detection were carried out. Water-rock interactions and their effects on rock mechanical behavior were discussed. The results indicate that water content significantly weakens rock mechanical strength. The sensitivity of the mechanical parameters to water treatment, from high to low, are Poisson ratio (𝜇), uniaxial tensile strength (UTS), uniaxial compressive strength (UCS), elastic modulus (E), and peak strain (𝜀). After water treatment, AE activities and the shear crack percentage are reduced, the angles between macro fractures and loading direction are minimized, the dynamic phenomenon during loading is weakened, and the failure mode changes from a mixed tensile-shear type to a tensile one. Due to the softening, lubrication, and water wedge effects in water-rock interactions, water content increases pore size, promotes crack development, and weakens micro-pore structures. Further damage of rocks in fractured and caved zones due to the water-rock interactions leads to an extra load on the adjoining coal and rock masses, which will increase the risk of dynamic disasters.

Crack initiation mechanism and meso-crack evolution of pre-fabricated cracked sandstone specimens under uniaxial loading

  • Bing Sun;Haowei Yang;Sheng Zeng;Yu Yin;Junwei Fan
    • Geomechanics and Engineering
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    • v.33 no.6
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    • pp.597-609
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    • 2023
  • The instability and failure of engineered rock masses are influenced by crack initiation and propagation. Uniaxial compression and acoustic emission (AE) experiments were conducted on cracked sandstone. The effect of the crack's dip on the crack initiation was investigated using fracture mechanics. The crack propagation was investigated based on stress-strain curves, AE multi-parameter characteristics, and failure modes. The results show that the crack initiation occurs at the tip of the pre-fabricated crack, and the crack initiation angle increases from 0° to 70° as the dip angle increases from 0° to 90°. The fracture strength kcr is derived varies in a U-shaped pattern as β increased, and the superior crack angle βm is between 36.2 and 36.6 and is influenced by the properties of the rock and the crack surface. Low-strength, large-scale tensile cracks form during the crack initiation in the cracked sandstone, corresponding to the start of the AE energy, the first decrease in the b-value, and a low r-value. When macroscopic surface cracks form in the cracked sandstone, high-strength, large-scale shear cracks form, resulting in a rapid increase in the AE energy, a second decrease in the b-value and an abrupt increase in the r-value. This research has significant theoretical implications for rock failure mechanisms and establishment of damage indicators in underground engineering.

합성 전단벽에 대한 대각 압축 응력장 접근법

  • Lee, Eo-Jin;Hong, Sung-Gul
    • Proceedings of the Korea Concrete Institute Conference
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    • 2010.05a
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    • pp.5-6
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    • 2010
  • In this study, assuming that there is a diagonal uniaxial compression field in combination with triangular homogeneous stress fields in the cracked concrete wall and a tensile stress of a steel plate occurs in the perpendicular to the direction of the diagonal compression field, an ultimate shear strength of a slender composite shear wall is estimated.

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Numerical Study on Long-term Behavior of Flat Plate Subjected to In-Plane Compressive and Transverse Loads (바닥하중과 압축력을 받는 플랫 플레이트의 장기거동에 대한 해석적 연구)

  • 최경규;박홍근
    • Proceedings of the Korea Concrete Institute Conference
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    • 2000.04a
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    • pp.611-616
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    • 2000
  • Numerical studies were carried out to investigate the long-term behavior of late plates in basement, subjected to combined in-plane compressive and transverse loads. For the numerical studies, a computer program of nonlinear finite element analysis was modified by adding function of creep and shrinkage analysis. This numerical method was verified by comparison with the existing experiments. Parametric studies were performed to investigate the strength variations of flat plates with three parameters; 1) loading sequence of floor load, compression and time 2) uniaxial an biaxial compression and 3) the ratio of dead to live load.

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A Study on the Estimation of Optimal Unit Content of Binder for the Soil Stabilizer Using the Recycled Resource in DMM (심층혼합공법에서 순환자원을 활용한 지반안정재의 최적 단위결합재량 산정에 관한 연구)

  • Seo, Se-Gwan;Lee, Khang-Soo;Kim, You-Seong;Cho, Dae-sung
    • Journal of the Korean Geosynthetics Society
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    • v.18 no.2
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    • pp.37-44
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    • 2019
  • The compressive strength of the soil stabilizer in the deep mixing method (DMM) depends on kinds of soil, particle size distribution, and water content. Because of this, Laboratory test has to perform to estimate the unit weight of binder to confirm the satisfaction of the design strength. In this study, uniaxial compression strength was measured by mixing the soil stabilizers developed in the previous study with clay in Busan, Yeosu, and Incheon area. And the strength enhancement effect was evaluated comparing with blast furnace slag cement (BFSC). Also, the relationship between the unit content of binder and uniaxial compressive strength was investigated in order to easily calculate the unit weight of binder required to ensure the stability of the ground at the field. As the results of the analysis, the relationship between the unit content of binder and the uniaxial compressive strength are ${\gamma}_B=(108.93+0.0284q_u){\pm}35$ when W/B is 70%, and ${\gamma}_B=(122.93+0.0270q_u){\pm}40$ when W/B is 80%.

Compression Strength Behavior of Mixed Soil Recycling Bottom Ash for Surface Layer Hardening (매립석탄회를 재활용한 표층연약지반 개량용 혼합토의 압축강도 특성 연구)

  • Oh, Gi-dae;Kim, Kyoung Yul
    • KEPCO Journal on Electric Power and Energy
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    • v.5 no.4
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    • pp.287-293
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    • 2019
  • Domestic thermal power plant fly ash is at a situation which emissions are increasing every year. Comparing to Fly Ash, Bottom Ash is only 15 %, but it's recycling rate is low, so most of them is being buried in the ground. However, landfill site of every power plant is full, and the construction of a new landfill is difficult. To solve this problem, the best solution is to use Bottom Ash as a landfill of large-scale civil engineering projects. The purpose of this study was to investigate the compression strength behavior characteristics of weak clay and uniaxial compression test to examine the applicability of surface soil solidification method of mixed soils mixed with industrial waste coal ash and weak clay which is buried in bulk. As a result of the test, the fluidity of the Mixed soil with clay + bottom ash + cement was improved to 200 mm at the water content of 91-92 %. The uniaxial compressive strength was also good for the mixed soils (clay + bottom ash + cement) meeting the required strength of 159 kN/㎡ at 28 days. However, the other samples did not meet the required strength. In this study, the prediction equations for the compression strength behavior by cement and curing period were presented.

Weathering Characteristics of Granite by Freeze-Thaw Cyclic Test (동결-융해 시험에 의한 화강암의 풍화 특성 연구)

  • Park, Yeon-Jun;You, Kwang-Ho;Yang, Kwang-Yong;Woo, Ik;Park, Chan;Song, Won-Kyung
    • Tunnel and Underground Space
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    • v.13 no.3
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    • pp.215-224
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    • 2003
  • Weathering in nature was simulated by freeze-thaw cyclic test which represents mechanical weathering. Measured physical properties were elastic wave velocities, absorption rate, volume change and weight change. Uniaxial compression tests were also conducted before and after the weathering tests. The change in weight and volume of the specimens were not clearly related to the weathering process, but P, S wave velocities, uniaxial compression strength and Young's modulus were clearly decreased as weathering progresses. Test result can be used for the assessment of long-term stability of rock slopes.

Experiments Study on Critical Strain Properties of Sedimentary Rocks (실험적 연구를 통한 퇴적암의 한계변형률 특성에 관한 연구)

  • Lee, Jae-Ho;Kim, Young-Su;Jin, Guang-Ril;Park, Jang-Ho;Park, Si-Hyun
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.03a
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    • pp.211-219
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    • 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 compression tests. Finally, critical strain properties of sedimentary rock is discussed the relationship of failure strain values, uniaxial compression strengths and Young's modulus.

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