• Title/Summary/Keyword: ground relaxation

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Development of Removable-Strand Compression Anchor (압축형 제거 앵커의 개발 및 성능 평가)

  • 김낙경;김성규
    • Proceedings of the Korean Geotechical Society Conference
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    • 2001.03a
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    • pp.339-346
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    • 2001
  • For temporary excavation support in private land area, the strand of ground anchor should be removed In order to get permission to install anchors. The extractable or removable-strand compression anchor system was developed and evaluated by a series of pull-out load tests. Anchor pull-out tests were performed on seven instrumented full-scale low-pressure grouted anchors installed in weathered soil at the Geotechnical Experimentation Site at Sungkyunkwan University, Four anchors are the compression type anchors and three are the tension anchors. Performance test, creep test, and long term relaxation test were performed and presented. Load distributor was developed in order to distribute large compressive stresses in grout.

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Diagnostic of Cast Resin Using Active Infrared Thermal Testing Method (능동열시험법을 이용한 몰드변압기 진단)

  • Lim, Young-Bae;Jeong, Seung-Cheon
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.07a
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    • pp.481-484
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    • 2004
  • A form of measured temperature distribution to estimate condition of a electrical apparatus is a absolute reference for condition of the apparatus, time rate of transition, and difference between reference and currently temperature. Because passive thermography which has not injection of external thermal stimulation shows difference of temperature being on surface of a structure and temperature difference between the structure and back ground, the result could apply only to estimation or monitor for condition of terminal relaxation and overload related with temperature rising. However, a thermal flow in active thermography is differently generated by structure and condition of surface and subsurface. This paper presents the nondestructive testing using the properties and includes the results by heat injection and cooling to the apparatus. The buried discontinuity of subsurface could be detected by these techniques.

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Thermal Annealing Effect on the Machining Damage for the Single Crystalline Silicon (단결정 실리콘의 기계적 손상에 대한 열처리 효과)

  • 정상훈;정성민;오한석;이홍림
    • Journal of the Korean Ceramic Society
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    • v.40 no.8
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    • pp.770-776
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    • 2003
  • #140 mesh and #600 mesh wheels were adopted to grind (111) and (100) oriented single crystalline silicon wafer and the grinding induced change of the surface integrity was investigated. For this purpose, microroughness, residual stress and phase transformation were analyzed for the ground surface. Microroughness was analyzed using AFM (Atomic Force Microscope) and crystal structure was analyzed using micro-Raman spectroscopy. The residual stress and phase transformation were also analyzed after thermal annealing in the air. As a result, microroughness of (111) wafer was larger than that of (100) wafer after grinding. It was observed using Raman spectrum that the silicon was transformed from diamond cubic Si-I to Si-III(body centered tetragonal) or Si-XII(rhombohedral). Residual stress relaxation was also shown in cavities which were produced after grinding. The thermal annealing was effective for the recovery of the silicon phase to the original phase and the residual stress relaxation.

Evaluation on Cavity Expansion under Pavement based on Groundwater Injection test (지하수 주입실험을 통한 도로노면 하부의 공동 확장 평가)

  • Park, Jeong-Jun;You, Seung-Kyong;Hong, Gigwon
    • Journal of the Korean Geosynthetics Society
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    • v.18 no.3
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    • pp.79-88
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    • 2019
  • This study described a results of groundwater injection test in cavity, in order to evaluate characteristics of cavity expansion under pavement. That is, groundwater amount proportional to the cavity volume was injected into the generated cavity step by step, and then the cavity with the changed size was monitored as the injected groundwater was drained. The test result showed that the cavity volume by groundwater injection increased, and then it converged or decreased. This means that some of the relaxation soil around the cavity collapsed, and the fine-grained soils in some soils filled the void in the surrounding soils when the cavity is expanded by groundwater injection. The volume change and expansion characteristics of the cavity according to the groundwater injection step were analyzed. The result showed that the cavity extended laterally. Therefore, it was found that the cavity expansion is caused by the repetition of the relaxation soil collapse due to the groundwater flow and the loss of the collapsed soil below the cavity.

Mechanical and Rheological Properties of Rice Plant (수도(水稻)의 역학적(力學的) 및 리올러지 특성(特性)에 관(關)한 연구(硏究))

  • Huh, Yun Kun;Cha, Gyun Do
    • Korean Journal of Agricultural Science
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    • v.14 no.1
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    • pp.98-133
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    • 1987
  • The mechanical and rheological properties of agricultural materials are important for engineering design and analysis of their mechanical harvesting, handling, transporting and processing systems. Agricultural materials, which composed of structural members and fluids do not react in a purely elastic manner, and their response when subjected to stress and strain is a combination of elastic and viscous behavior so called viscoelastic behavior. Many researchers have conducted studies on the mechanical and rheological properties of the various agricultural products, but a few researcher has studied those properties of rice plant, and also those data are available only for foreign varieties of rice plant. This study are conducted to experimentally determine the mechanical and the rheological properties such as axial compressive strength, tensile strength, bending and shear strength, stress relaxation and creep behavior of rice stems, and grain detachment strength. The rheological models for the rice stem were developed from the test data. The shearing characteristics were examined at some different levels of portion, cross-sectional area, moisture content of rice stem and shearing angle. The results obtained from this study were summarized as follows 1. The mechanical properties of the stems of the J aponica types were greater than those of the Indica ${\times}$ Japonica hybrid in compression, tension, bendingand shearing. 2. The mean value of the compressive force was 80.5 N in the Japonica types and 55.5 N in the Indica ${\times}$ Japonica hybrid which was about 70 percent to that of the Japonica types, and then the value increased progressively at the lower portion of the stems generally. 3. The average tensile force was about 226.6 N in the Japonica types and 123.6 N in the Indica ${\times}$ Japonica hybrid which was about 55 percent to that of the Japonica types. 4. The bending moment was $0.19N{\cdot}m$ in the Japonica types and $0.13N{\cdot}m$ in the Indica ${\times}$ Japonica hybrid which was 68 percent to that of the Japonica types and the bending strength was 7.7 MPa in the Japonica types and 6.5 MPa in the Indica ${\times}$ Japonica hybrid respectively. 5. The shearing force was 141.1 N in Jinju, the Japonica type and 101.4 N in Taebaeg, the Indica ${\times}$ Japonica hybrid which was 72 percent to that of Jinju, and the shearing strength of Taebaeg was 63 percent to that of Jinju. 6. The shearing force and the shearing energy along the stem portion in Jinju increased progressively together at the lower portions, meanwhile in Taebaeg the shearing force showed the maximum value at the intermediate portion and the shearing energy was the greatest at the portion of 21 cm from the ground level, and also the shearing strength and the shearing energy per unit cross-sectional area of the stem were the greater values at the intermediate portion than at any other portions. 7. The shearing force and the shearing energy increased with increase of the cross-sectional area of the rice stem and with decrease of the shearing angie from $90^{\circ}$ to $50^{\circ}$. 8. The shearing forces showed the minimum values of 110 N at Jinju and of 60 N at Taebaeg, the shearing energy at the moisture content decreased about 15 percent point from initial moisture content showed value of 50 mJ in Jinju and of 30 mJ in Taebaeg, respectively. 9. The stress relaxation behavior could be described by the generalized Maxwell model and also the compression creep behavior by Burger's model, respectively in the rice stem. 10. With increase of loading rate, the stress relaxation intensity increased, meanwhile the relaxation time and residual stress decreased. 11. In the compression creep test, the logarithmic creep occured at the stress less than 2.0 MPa and the steady-state creep at the stress larger than 2.0 MPa. 12. The stress level had not a significant effect on the relaxation time, while the relaxation intensity and residual stress increased with increase of the stress level. 13. In the compression creep test of the rice stem, the instantaneous elastic modulus of Burger's model showed the range of 60 to 80 MPa and the viscosities of the free dashpot were very large numerical value which was well explained that the rice stem was viscoelastic material. 14. The tensile detachment forces were about 1.7 to 2.3 N in the Japonica types while about 1.0 to 1.3 N in Indica ${\times}$ Japonica hybrid corresponding to 58 percent of Japonica types, and the bending detachment forces were about 0.6 to 1.1 N corresponding to 30 to 50 percent of the tensile detachment forces, and the bending detachment of the Indica ${\times}$ Japonica hybrid was 0.1 to 0.3 N which was 7 to 21 percent of Japonica types. 15. The detachment force of the lower portion was little bigger than that of the upper portion in a penicle and was not significantly affected by the harvesting period from September 28 to October 20. 16. The tensile and bending detachment forces decreased with decrease of the moisture content from 23 to 13 percent (w.b.) by the natural drying, and the decreasing rate of detachment forces along the moisture content was the greater in the bending detachment force than the tensile detachment force.

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Influence of Facing Stiffness on Global Stability of Soil Nailing Systems (전면벽체의 강성이 Soil Nailing 시스템의 전체안정성에 미치는 영향)

  • Kim, Hong-Taek;Kang, In-Kyu;Kwon, Young-Ho
    • Journal of the Korean GEO-environmental Society
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    • v.5 no.3
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    • pp.51-60
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    • 2004
  • In Korea there are recently many attempts to expand a temporary soil nailing system into a permanent soil nailing system since the first construction in 1993. In the soil nailing system, the rigid facing walls act on restraining the deformation of the ground. These are purposed to minimize the damage of adjacent buildings or underground structures. In Korea, to minimize the relaxation of the ground, the soil nailing system in the downtown area is often used experientially together with braced cuts, sheet pile walls, soil cement walls (SCW), or jet grouting walls. However, for the conservative design, the confining effects by the stiff facing have been ignored because the proper design approach of considering the facing stiffness has not been proposed. In this study, various laboratory model tests are carried out to examining the influence the rigidity of facings on the global safety of soil nailing system. Also, the parametric studies using the numerical technique as shear-strength reduction technique are carried out. In the parametric study, the thickness of concrete facing walls is changed to identify the effects of the facing wall stiffness.

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A study on the reduction of concrete lining re-bar according to the tunnel design factors (터널 설계인자 평가에 따른 콘크리트 라이닝 철근량 절감에 관한 연구)

  • Kang, Si-On;Lim, Young-Duck;Shin, Jeong-Ho;Kim, Sang-Hwan
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.20 no.1
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    • pp.197-209
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    • 2018
  • This paper presents a study on the reduction of concrete lining re-bar according to the tunnel design factors. The design of the concrete lining increases the reinforcing re-bar according to the application of excessive load, and the economical efficiency is reduced. In order to improve the economical efficiency of tunnel construction, rational standards are required for the design factors of concrete lining. Therefore, this research analyzed the characteristics and problems of the design factors applied to the design of concrete lining. Also, the economical review of the concrete lining for design factor application was compared with the amount of reinforcing re-bar calculated from the section design using numerical analysis. The results show that the amount of re-bar is varied according to the design factors. That is, the required amount for re-bar in the tunnel concrete lining could be reduced in the design stage. The results of this study may be useful for economic design of concrete lining in the future.

Plan of Nature-friendly Residential Space (자연과 교우하는 주거공간 계획)

  • Kim, Bong-Soon
    • Proceedings of the Korean Institute of Interior Design Conference
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    • 2008.05a
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    • pp.32-35
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    • 2008
  • If human beings could make friends with nature, it would be a truly wellbeing. This project has selected the design concept under the supposition that human beings and the nature become friends. This residential house, which is consisted of one ground floor and two underground floors, is confronting the mountains that surround the residential complex. Residents can enjoy viewing the mountains from the living room. The garden is created by using this given environment in maximum. The walls are made up with rocks, and a small pond is formed with water from the mountain, presenting another attractive sight. Through the connection rather than the break between mountain and garden, living room and garden, and again garden and mountain, the dialogue with nature was attempted. The water of the pond in the garden flows down along the walls and creates another water space at the gate area of the house. Passing through the entrance, there are a living room, a kitchen, a bedroom for spouses, a common bathroom, and a library on the ground floor. On the second floor, there are two rooms, a bathroom, and a mini living room. The platform of living room on the 1st floor is lowered to produce the comfortable living room with the hearth. From the view of living room, the garden with full feeling of nature can give a good emotional rest for modem people who want the mental relaxation. The marble stones are used as its material to present rich texture and sophisticated image presentation. The hearth in the living room is harmonized with high-tech electronic home appliances and surrounding accessories. On the kitchen, the high-glossy materials are used to express the external appearance neatly and the depository function is more improved for housewives.

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A Study on the Self-contained Earth Retaining Wall Method Using Bracing (브레이싱을 이용한 자립식 흙막이 공법에 관한 연구)

  • Kim, Jong-Gil
    • Journal of Digital Convergence
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    • v.17 no.3
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    • pp.205-213
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    • 2019
  • In a construction site, excavation work has a close relation with temporary earth retaining structure. In order to build the underground structure most effectively in a narrow space, prevent soil relaxation of the external behind ground in excavation work, and maintain a ground water level, it is required to install a temporary earth retaining structure that secures safety. To prevent soil washoff in underground excavation work, the conventional method of temporary earth retaining structure is to make a temporary wall and build the internal support with the use of earth anchor, raker, and struct for excavation work. RSB method that improves the problem of the conventional method is to remove the internal support, make use of two-row soldier piles and bracing, and thereby to resist earth pressure independently for underground excavation. This study revealed that through the field application cases of RSB method and the measurement result, the applicability of the method for installing a temporary earth retaining structure, the assessment result, and displacement all met allowable values of measurement, and that the RSB method, compared to the conventional method, improved constructability and economy.

Numerical analysis of segmental tunnel linings - Use of the beam-spring and solid-interface methods

  • Rashiddel, Alireza;Hajihassani, Mohsen;Kharghani, Mehdi;Valizadeh, Hadi;Rahmannejad, Reza;Dias, Daniel
    • Geomechanics and Engineering
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    • v.29 no.4
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    • pp.471-486
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    • 2022
  • The effect of segmental joints is one of main importance for the segmental lining design when tunnels are excavated by a mechanized process. In this paper, segmental tunnel linings are analyzed by two numerical methods, namely the Beam-Spring Method (BSM) and the Solid-Interface Method (SIM). For this purpose, the Tehran Subway Line 6 Tunnel is considered to be the reference case. Comprehensive 2D numerical simulations are performed considering the soil's calibrated plastic hardening model (PH). Also, an advanced 3D numerical model was used to obtain the stress relaxation value. The SIM numerical model is conducted to calculate the average rotational stiffness of the longitudinal joints considering the joints bending moment distribution and joints openings. Then, based on the BSM, a sensitivity analysis was performed to investigate the influence of the ground rigidity, depth to diameter ratios, slippage between the segment and ground, segment thickness, number of segments and pattern of joints. The findings indicate that when the longitudinal joints are flexible, the soil-segment interaction effect is significant. The joint rotational stiffness effect becomes remarkable with increasing the segment thickness, segment number, and tunnel depth. The pattern of longitudinal joints, in addition to the joint stiffness ratio and number of segments, also depends on the placement of longitudinal joints of the key segment in the tunnel crown (similar to patterns B and B').