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Soils and foundations
Japanese Geotechnical Society
Soils and foundations

Japanese Geotechnical Society

双月刊

0038-0806

Soils and foundations/Journal Soils and foundationsEISCIISTP
正式出版
收录年代

    Base resistance of drilled shafts in soft rock using in situ load tests: A limit state approach

    Asem, Pouyan
    1639-1658页
    查看更多>>摘要：This paper presents a probabilistic limit state framework for the evaluation of the base resistance of drilled shafts in soft rock. In situ load tests and the Griffith fracture theory are used to evaluate the mode of failure for the rock mass under the drilled shaft base. The base resistance or the limit state in the context of this paper is defined by the contact pressure at which load induced vertical to subvertical cracks form and the contact pressure-displacement relationship passes into a steep and fairly straight tangent. The parameters affecting the base resistance are evaluated using an in situ load test database. A statistical approach using the maximum likelihood method is utilized for the development of the design model for the base resistance. Reliability analysis is used to calibrate the corresponding resistance factors. The in situ load tests and the Griffith fracture theory suggest that the soft rock mass underlying the drilled shaft base primarily fails by the formation of vertical to subvertical cracks. Field observations indicate that the displacements in the underlying rock mass are largely in the vertical direction and that the base displacements required to mobilize the proposed base resistance are generally less than 30 mm. Load test data show that the base resistance is chiefly related to the unconfined compressive strength of soft rock. The calculated resistance factors are found to slightly decrease with increase in the span length of the structure and increase with the increase in the foundation redundancy. (C) 2019 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society.
      原文链接:
    • NETL
    • NSTL
    • Japanese Geotechnical Soc

    Hybrid numerical tool for nonlinear analysis of piled rafts

    Bernardes, Heitor CardosoCarvalho, Sofia LeaoSales, Mauricio MartinesMesquita de Almeida, Sylvia Regina...
    1659-1674页
    查看更多>>摘要：This paper presents a hybrid numerical tool for nonlinear piled rafts analysis. The nonlinear pile behavior is represented by a hyperbolic function, which intends to simulate the variation in pile stiffness during loading. As the nonlinear behavior of piles is restricted to a very thin zone next to the pile interface, only the linear elastic effects are considered in the interaction factors between foundation elements. The influence of using Kirchhoff or Mindlin plate finite elements to model the raft is discussed. The code was compared to other well tested numerical tools, three model tests on piled raft foundation carried out at the Nagoya Institute of Technology (NIT) and also a well-known case of piled raft foundation (Hyde Park Cavalry Barracks in London). The code showed a very good agreement, proving its consistency and potential for use in piled raft analysis and design. (C) 2019 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society.
      原文链接:
    • NETL
    • NSTL
    • Japanese Geotechnical Soc

    Sand-concrete interface response: The role of surface texture and confinement conditions

    Nardelli, AndreiCacciari, Pedro PazzotoFutai, Marcos Massao
    1675-1694页
    查看更多>>摘要：Sand-concrete interface direct shear tests were used to investigate the effects of surface roughness, surface waviness, mean sand diameter and relative density on interface strength and behavior under different confinement conditions. Extreme concrete surface textures, including smooth, rough and rough-wavy textures, were reproduced. Surface plowing was assessed via image analysis, laser scanning and extended multifocal micrographs. The experimental results showed that smooth concrete surfaces exhibited high values of interfacial-to-internal friction angle ratios, ranging 88-90%, due to the angular shape of sand particles. The rough concrete surfaces generated higher interface strength than smooth concrete surfaces; however, the interface strength was still inferior to the surrounding sand strength. Surface plowing, which identified a mixed shear plane at the sand-concrete interface, was developed as particles were detached from the surface, thus inhibiting the interface friction angle from reaching the sand friction angle. Higher sand-concrete interface strength was achieved as surface waviness increased, and interface friction angles greater than the surrounding sand friction angle were reached. Under a constant normal stiffness condition, significantly high interface strength is achieved due to the increase of the current normal stress, which was directly influenced by the initial normal stress, stiffness, surface roughness, mean sand diameter and relative density; surface waviness did not have a marked effect on the normal stress variation. Based on these results, multiple regressions were proposed to estimate the sand-concrete interface strength by the interfacial-to-internal friction angle ratio and the effect of the constant normal stiffness condition. (C) 2019 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society.
      原文链接:
    • NETL
    • NSTL
    • Japanese Geotechnical Soc

    Interface load-displacement behaviour of sand grains coated with clayey powder: Experimental and analytical studies

    Kasyap, S. S.Senetakis, K.
    1695-1710页
    查看更多>>摘要：In the present study, the micromechanical behaviour at the interfaces of sand grains coated with kaolinite powder is examined. Two different classes of coated grains were produced, one with lighter coating and one with heavier coating. The interface micromechanical experiments were conducted on pairs of grains and the emphasis was placed on the normal and tangential load-displacement relationships and the inter-particle friction of the different pairs highlighting the differences between uncoated and coated grains and also between the different classes of coating. All the experiments were conducted using a micromechanical custom-built loading apparatus and for the analysis of the data, analytical models from the literature were used, where adequate modifications were applied in specific in the tangential direction to match with the experimental results. Iteration processes, image analyses and microscopic image observations were adopted in the study of the frictional behaviour of the grains as well as the study of the damage of the surfaces. Work done and rate of work done concepts were introduced and linked to the damage of the surfaces of the grains and the role of repeating the shearing tests following the same shearing paths were particularly emphasized. The results from the study can provide some useful insights into the grain-scale behaviour of soil grains as well as input parameters in DEM studies. (C) 2019 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society.
      原文链接:
    • NETL
    • NSTL
    • Japanese Geotechnical Soc

    Simplified analytical method for evaluating the effects of overcrossing tunnelling on existing shield tunnels using the nonlinear Pasternak foundation model

    Liang, Rongzhu
    1711-1727页
    查看更多>>摘要：The excavation of a new tunnel above an existing shield tunnel at close proximity may cause a series of adverse impacts on the underlying tunnel. Thus, a reasonable assessment of the existing shield tunnel's responses to overcrossing tunnelling is crucial to ensuring the safety and serviceability of the existing shield tunnel. In this study, a simplified nonlinear analytical method is proposed to rapidly assess existing shield tunnel responses to overcrossing tunnelling. A nonlinear Pasternak foundation model (NPFM), considering the nonlinear deformation of the ground as well as the interaction between adjacent springs and upward tunnel displacement, is proposed for modelling the tunnel-soil interaction associated with unloading stress. An effective Newton's iterative computational program, combined with the finite difference method, is developed for the nonlinear responses of the existing shield tunnel. The reliability and applicability of the proposed method are subsequently validated by a comparison with the results of three-dimensional finite element analyses and two well-documented and published field measurements. The predictions are also compared with the results of six elastic simplified analytical methods based on different subgrade reaction moduli. (C) 2019 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society.
      原文链接:
    • NETL
    • NSTL
    • Japanese Geotechnical Soc

    Performances of SDCM and DCM walls under deep excavation in soft clay: Field tests and 3D simulations

    Voottipruex, PanichJamsawang, PitthayaSukontasukkul, PitiJongpradist, Pornkasem...
    1728-1739页
    查看更多>>摘要：This study presents the results of full-scale tests and three-dimensional finite element analyses of deep cement mixing (DCM) and stiffened deep cement mixing (SDCM) columns under lateral loads and DCM and SDCM walls under deep excavation in soft clay. The DCM walls used in this study comprised one, two and three rows of DCM columns, whereas the SDCM walls consisted of only one row of DCM columns with steel H-beams inserted in either all DCM columns or in alternating DCM columns. The measured and simulated results are presented in terms of profiles of lateral displacement, settlement and bending moment. (C) 2019 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society.
      原文链接:
    • NETL
    • NSTL
    • Japanese Geotechnical Soc

    Investigation for the key technologies of ultra-high asphalt concrete core rockfill dams

    Gao, JunDang, FaningMa, Zongyuan
    1740-1757页
    查看更多>>摘要：The mechanical characteristics of ultra-high asphalt concrete core rockfill dams (UACCRDs) at different periods is investigated via Rankine's earth pressure theory, and a shear safety control standard for UACCRDs is proposed. The reasonable material parameters of the asphalt concrete core (ACC) and transition material that independently and comprehensively satisfy the shear safety control standard are back-calculated. The engineering measures that reduce the stress level (shear stress) of the ACC are given. Moreover, the engineering measures (straight asphalt concrete core rockfill dams (SACCRDs) are designed as curved asphalt concrete core rockfill dams (CACCRDs)) that reduce the tensile stress of the ACC are proposed. Based on the theory of the straight beam and curved beam on Winkler elastic foundation, the simplified mechanical models of straight asphalt concrete core (SACC) and curved asphalt concrete core (CACC) are established. The improvement effect of CACC that reduces tensile stress is also investigated. The results show that the following value ranges of the internal friction angle, cohesion of ACC and the internal friction angle of transition material for the suitable construction of UACCRDs are recommended: (phi(a) >= 30.5 degrees, C-a >= 0.25 MPa and phi(t) <= 43.5 degrees (h = 200 m), with the growth gradient adjusted by 0.5%, 1.5% and -0.5%/25 m. The stress level of ACC can be obviously reduced by increasing the internal friction angle and cohesion of ACC, and reducing the internal friction angle of transition material. The simplified mechanical models of SACC and CACC can estimate the force and deformation characteristic of the ACC (SACC and CACC) well. The CACC can significantly reduce tensile stress to a level approximately 42.8% lower than that of SACC. (C) 2019 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society.
      原文链接:
    • NETL
    • NSTL
    • Japanese Geotechnical Soc

    Evaluation of liquefaction probability of earth-fill dam over next 50 years using geostatistical method based on CPT

    Imaide, KazunariNishimura, Shin-ichiShibata, ToshifumiShuku, Takayuki...
    1758-1771页
    查看更多>>摘要：A method for evaluating the liquefaction probability of an earth-fill dam over the next 50 years is presented through the use of a geostatistical method for the measured values from cone penetration tests (CPTs). In particular, this paper discusses a new procedure for evaluating the liquefaction probability based on CPTs. Although the fines content, F e , and the N-value are required in the Japanese standards to evaluate the liquefaction risk, the number of test data is not enough for the statistical modeling. Herein, F e and the N-value are derived directly from CPTs. The statistical modeling procedure for F-e and the N-value is the unique point of this study. Since CPTs can be conducted with short intervals, especially in the horizontal direction, the geostatistical parameters can be determined, and the geostatistical simulation method is applicable for evaluating the liquefaction probability. In addition, since the frequency of the seismic load at the studied site will affect the liquefaction probability, the seismic hazard should be evaluated properly. An illustrative example, assessing the liquefaction probability of an earth-fill dam in Japan, is presented to demonstrate the capability of the proposed method. Finally, the spatial average of the liquefaction probability of the dam over the next 50 years is calculated. The proposed procedure is confirmed to work well for actual design problems. (C) 2019 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society.
      原文链接:
    • NETL
    • NSTL
    • Japanese Geotechnical Soc

    Minimum void ratio characteristic of soils containing non-plastic fines

    Kim, JongkwanKawai, TadashiKazama, Motoki
    1772-1786页
    查看更多>>摘要：The minimum void ratio is an index widely used to indicate the contraction characteristics and the densest state of soils. The minimum void ratio obtained by the traditional test method has been utilized to represent the density of soils irrespective of their fines content despite the restriction (FC <= 5%). By considering the effect of the blow count, pore water, and their primary properties, the applicability of the minimum void ratio to soils containing fines was examined with an automatic tapping machine. It was confirmed that the blow count of the traditional method is not sufficient for soils with a high fines content. Furthermore, the presence of pore water had a significant effect on the minimum void ratio of soils containing fines. The characteristics of the cyclic minimum void ratio, which indicates the minimum void ratio obtained throughout the repetition of liquefaction and drainage, were also examined. (C) 2019 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society.
      原文链接:
    • NETL
    • NSTL
    • Japanese Geotechnical Soc

    Collapse of concrete-covered levee under composite effect of overflow and seepage

    Takahashi, HidenoriMorikawa, YoshiyukiMori, NobuhitoYasuda, Tomohiro...
    1787-1799页
    查看更多>>摘要：During the Great East Japan Earthquake and Tsunami of 2011, enormous coastal levees collapsed as a result of tsunami overflows. Concrete-covered levees, where concrete blocks are used to protect levees made of soil, showed a specific failure mode in which back slope blocks and internal soils were dislodged. Although several hydraulic experiments have been conducted in an attempt to understand the failure mechanism, the complexity of the failure requires that both hydro-dynamical and geotechnical points of view be taken into account for a deeper understanding. This study uses a centrifuge to identify the failure behavior of levees from those points of view. The centrifuge can reproduce the stress, water pressure, and overflow velocity of the prototype-scale ground. Overflowing at sufficient time periods was produced in the centrifuge by generating differences in water height for seaside and landside areas. The test results showed that the levees collapsed due to a combination of the effect of water flow on the back slope and seepage inside the levees. In addition, the effectiveness of several proposed countermeasures for preventing collapse was confirmed. (C) 2019 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society.
      原文链接:
    • NETL
    • NSTL
    • Japanese Geotechnical Soc