• Title/Summary/Keyword: Soil structure interaction

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Comparison of Seismic Responses of Underground Utility Tunnels Using Simplified Analysis Methods (단순화 해석 방법에 따른 지하공동구 지진 응답 산정 비교)

  • Kim, Dae-Hwan;Lim, Youngwoo;Seo, Hyun-Jeong;Lee, Hyerin
    • Journal of the Earthquake Engineering Society of Korea
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    • v.28 no.4
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    • pp.205-213
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    • 2024
  • In the seismic evaluation of underground utility tunnels, selecting an analytical method is critical to estimating reasonable seismic responses. In simplified pseudo-static analysis methods widely applied to typical seismic design and evaluation of underground tunnels in practice, it is essential to check whether the methods provide valid results for cut-and-cover tunnels buried in shallow to medium depth. The differences between the two simplified pseudo-static methods are discussed in this study, and the analysis results are compared to those obtained from FLAC models. In addition to the analysis methods, seismic site classification, overburden soil depth, and sectional configuration are considered variables to examine their effects on the seismic response of underground utility tunnels. Based on the analysis results, the characteristics derived from the concepts and details of each simplified model are discussed. Also, general observations are made for the application of simplified analysis methods.

3D Transmitting Boundary for Water-Saturated Transversely Isotropic Soil Strata Based on the u-w Formulation (u-w 정식화에 근거한 지하수로 포화된 가로등방성 층상지반에서의 3차원 전달경계)

  • Lee, Jin-Ho;Kim, Jae-Kwan;Ryu, Jeong-Soo
    • Journal of the Earthquake Engineering Society of Korea
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    • v.13 no.6
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    • pp.67-86
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    • 2009
  • In this study, a 3D transmitting boundary in water-saturated transversely isotropic soil strata has been developed based on u-w formulation for application to general 3D analysis. Behavior in the far field region is expanded in the Fourier series, and dynamic stiffness for each term is obtained based on the u-w formulation. Transformation of the dynamic stiffness is presented to combine the transmitting boundary with the 3D finite elements for the near field region formulated in a 3D Cartesian coordinate system. The developed transmitting boundary is verified through a comparison of the dynamic behavior of a rigid circular foundation with the results from the existing numerical method. In addition, the developed transmitting boundary is applied to the analysis of the dynamic behavior of rigid foundations of diverse shapes, and the effects of the level of the groundwater table on the dynamic stiffness of a rigid rectangular foundation in the water-saturated transversely isotropic layered stratum are studied.

A Simplified Numerical Model for an Integral Abutment Bridge Considering the Restraining Effects Due to Backfill

  • Hong, Jung-Hee;Jung, Jae-Ho;You, Sung-Kun;Yoon, Soon-Jong
    • Journal of the Korea Concrete Institute
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    • v.15 no.5
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    • pp.759-767
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    • 2003
  • This paper presents the simplified but more rational analysis method for the prediction of additional internal forces induced in integral abutment bridges. These internal forces depend upon the degree of restraint provided tc the deck by the backfill soil adjacent to the abutments and piles. In addition, effect of the relative flexural stiffness ratio among pile foundations, abutment, and superstructure on the structural behavior is also an important factor. The first part of the paper develops the stiffness matrices, written in terms of the soil stiffness, for the lateral and rotational restraints provided by the backfill soil adjacent to the abutment. The finite difference analysis is conducted and it is confirmed that the results are agreed well with the predictions obtained by the proposed method. The simplified spring model is used in the parametric study on the behavior of simple span and multi-span continuous integral abutment PSC beam bridges in which the abutment height and the flexural rigidity of piles are varied. These results are compared with those obtained by loading Rankine passive earth pressure according to the conventional method. From the results of parametric study, it was shown that the abutment height, the relative flexural rigidity of superstructure and piles, and the earth pressure induced by temperature change greatly affect the overall structural response of the bridge system. It may be possible to obtain more rational and economical designs for integral abutment bridges by the proposed method.

The Seismic Behavior of Corrugated Steel Plate Lining in Cut-and-Cover Tunnel (개착식 터널에서 파형강판 라이닝의 동적 거동 특성)

  • Kim Jung-Ho;Kim Nag-Young;Lee Yong-Jun;Lee Seung-Ho;Chung Hyung-Sik
    • 한국터널공학회:학술대회논문집
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    • 2005.04a
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    • pp.233-247
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    • 2005
  • Most tunnel lining material which has been used in the domestic is a concrete. But many problems as the construction period, the cost, and the crack occurrence for the design, construction, and management were happened in the concrete lining. For this reason, many research institutes like the Korea Highway Corporation recognize the necessity of an alternate material development and grow on the interest for that. So in this study, the seismic behaviour characteristics for the application of the Corrugated Steel Plate Lining in cut-and-cover tunnel are evaluated as several conditions for the backfill height, the cutting slope, and the relative density of backfill soil are changed. The compressive stress which is calculated in the Corrugated Steel Plate Lining by the seismic load is decreased as the backfill height increases and the cut slope grows gentle. Also, the moment shows the tendency of decrease according to the increase of the backfill height. But in the case of the relative density of the backfill soil is small, the moment increases according to the increase of the backfill height and affects the dynamic behaviour characteristic. So it is considered that the relative density of the backfill soil is also the important point. As the result in analyzing the seismic response characteristics of the reinforcement spacing of the Corrugated Steel Plate, the variation in the compressive force is hardly happened, but the moment and the shear force increase on the reinforcement spacing being narrow.

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Evaluation of Dynamic p-y Curve Based on the Numerical Analysis (수치해석기반의 동적 p-y 곡선 산정)

  • Park, Jeong-Sik;Jeong, Sang-Seom
    • Journal of the Korean Geotechnical Society
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    • v.33 no.12
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    • pp.59-73
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    • 2017
  • Numerical analysis using 3D finite element program (PLAXIS 3D) evaluated the interaction of soil - pile structure under dynamic surface loading. The dynamic p-y curve of the 1-g shaking table experiment by numerical analysis was calculated, and the parametric studies were presented by considering the pile-soil condition, the pile tip condition, and the loading condition. The frequency of 1.4 Hz is almost equal to the natural frequency of the pile - soil system. The p and y values of resonance phenomenon are significantly different from the results of other frequencies. The results can be summarized by a third order polynomial function representing the trend line in the p-y curve. In the case of a single pile, the shape of the dominant curve was found to be an ellipse by mathematical proof. The elliptic equation can be used for the dynamic design or analysis of soil-pile system.

Seismic performance evaluation of Pier-Shafts system with multi-layered soil (다양한 지반층을 갖는 Pier-Shafts 시스템의 내진성능평가)

  • Jang, Sung-Hwan;Nam, Sang-Hyeok;Song, Ha-Won;Kim, Byung-Chul
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.69-72
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    • 2008
  • The so-called Pier-Shafts system which consists of the continuous column and shaft is often used to support the highway bridge structure because of advantages in easy construction and low cost. In the earthquake region, the Pier-Shafts system undergoes large displacements and represents a nonlinear behavior under the lateral seismic loading. The soil-pile interaction should be considered for more accurate analysis of the Pier-Shafts system. In this study, a transverse response of a reinforced concrete Pier-Shafts system inside multi-layered soil medium is predicted using a finite element program which adopts an elasto-plastic interface model for the interface behavior between the shaft and the soil. Then, seismic analysis is performed to evaluate the performance of Pier-Shafts system under strong ground motion and their results are verified with experimental data.

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Study on the behaviour of pre-existing single piles to adjacent shield tunnelling by considering the changes in the tunnel face pressures and the locations of the pile tips

  • Jeon, Young-Jin;Jeon, Seung-Chan;Jeon, Sang-Joon;Lee, Cheol-Ju
    • Geomechanics and Engineering
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    • v.21 no.2
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    • pp.187-200
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    • 2020
  • In the current work, a series of three-dimensional finite element analyses have been conducted to investigate the behaviour of pre-existing single piles in response to adjacent tunnelling by considering the tunnel face pressures and the relative locations of the pile tips with respect to the tunnel. Via numerical modelling, the effect of the face pressures on the pile behaviour has been analysed. In addition, the analyses have concentrated on the ground settlements, the pile head settlements and the shear stress transfer mechanism at the pile-soil interface. The settlements of the pile directly above the tunnel crown (with a vertical distance between the pile tip and the tunnel crown of 0.25D, where D is the tunnel diameter) with a face pressure of 50% of the in situ horizontal soil stress at the tunnel springline decreased by approximately 38% compared to the corresponding pile settlements with the minimum face pressure, namely, 25% of the in situ horizontal soil stress at the tunnel springline. Furthermore, the smaller the face pressure is, the larger the tunnelling-induced ground movements, the axial pile forces and the interface shear stresses. The ground settlements and the pile settlements were heavily affected by the face pressures and the positions of the pile tip with respect to the tunnel. When the piles were inside the tunnel influence zone, tensile forces were induced on piles, while compressive pile forces were expected to develop for piles that are outside the influence zone and on the boundary. In addition, the computed results have been compared with relevant previous studies that were reported in the literature. The behaviour of the piles that is triggered by adjacent tunnelling has been extensively examined and analysed by considering the several key features in substantial detail.

Moment-rotational analysis of soil during mining induced ground movements by hybrid machine learning assisted quantification models of ELM-SVM

  • Dai, Bibo;Xu, Zhijun;Zeng, Jie;Zandi, Yousef;Rahimi, Abouzar;Pourkhorshidi, Sara;Khadimallah, Mohamed Amine;Zhao, Xingdong;El-Arab, Islam Ezz
    • Steel and Composite Structures
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    • v.41 no.6
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    • pp.831-850
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    • 2021
  • Surface subsidence caused by mining subsidence has an impact on neighboring structures and utilities. In other words, subsurface voids created by mining or tunneling activities induce soil movement, exposing buildings to physical and/or functional destruction. Soil-structure is evaluated employing probability distribution laws to account for their uncertainty and complexity to estimate structural vulnerability. In this study, to investigate the displacement field and surface settlement profile caused by mining subsidence, on the basis of a Winklersoil model, analytical equations for the moment-rotation response ofsoil during mining induced ground movements are developed. To define the full static moment-rotation response, an equation for the uplift-yield state is constructed and integrated with equations for the uplift- and yield-only conditions. The constructed model's findings reveal that the inverse of the factor of safety (x) has a considerable influence on the moment-rotation curve. The maximal moment-rotation response of the footing is defined by X = 0:6. Despite the use of Winkler model, the computed moment-rotation response results derived from the literature were analyzed through the ELM-SVM hybrid of Extreme Learning Machine (ELM) and Support Vector Machine (SVM). Also, Monte Carlo simulations are used to apply continuous random parameters to assess the transmission of ground motions to structures. Following the findings of RMSE and R2, the results show that the choice of probabilistic laws of input parameters has a substantial impact on the outcome of analysis performed.

A probabilistic fragility evaluation method of a RC box tunnel subjected to earthquake loadings (지진하중을 받는 RC 박스터널의 확률론적 취약도 평가기법)

  • Huh, Jungwon;Le, Thai Son;Kang, Choonghyun;Kwak, Kiseok;Park, Inn-Joon
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.19 no.2
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    • pp.143-159
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    • 2017
  • A probabilistic fragility assessment procedure is developed in this paper to predict risks of damage arising from seismic loading to the two-cell RC box tunnel. Especially, the paper focuses on establishing a simplified methodology to derive fragility curves which are an indispensable ingredient of seismic fragility assessment. In consideration of soil-structure interaction (SSI) effect, the ground response acceleration method for buried structure (GRAMBS) is used in the proposed approach to estimate the dynamic response behavior of the structures. In addition, the damage states of tunnels are identified by conducting the pushover analyses and Latin Hypercube sampling (LHS) technique is employed to consider the uncertainties associated with design variables. To illustrate the concepts described, a numerical analysis is conducted and fragility curves are developed for a large set of artificially generated ground motions satisfying a design spectrum. The seismic fragility curves are represented by two-parameter lognormal distribution function and its two parameters, namely the median and log-standard deviation, are estimated using the maximum likelihood estimates (MLE) method.

Numerical Study on Freezing and Thawing Process in Modular Road System (모듈러 도로시스템의 동결-융해에 대한 수치해석적 연구)

  • Shin, Hosung;Kim, Jinwook;Lee, Jangguen;Kim, Dong-Gyou
    • Journal of the Korean Geotechnical Society
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    • v.33 no.3
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    • pp.49-62
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    • 2017
  • In order to understand response of geo-structures to the freezing-thawing process in the ground, it is necessary to consider phase change of the pore water of the ground and also to understand soil interaction with structures. In this study, numerical analysis was carried out for freezing and thawing effect on the modular road system. Neumann's theoretical equation for freezing-thawing processes in porous media can be used to estimate frozen depth and heaving from basic soil properties and ground and surface temperature, but its application is limited to the case for the sediment with fully saturated condition and zero unfrozen water content. Numerical analysis of the modular road system was performed on various soil types and different ground water table as the varying freezing index. The amount of heaving in the silty soil was much larger than those in granite weathered soil or sandy soil, and lowering groundwater level reduced ground heaving induced by freezing. Numerical analysis for temperature history of the ground surface predicted residual heaving near the surface by the freeze-thaw process in silty soil. It ought to reduce stiffness and bearing capacity of the ground so that it will impair stability and serviceability of new road system. However, the amount of residual heaving was insignificant for the road system installed in weathered soil granite and sandy soil. Since modular road system is a pavement structure mounted on the supporting substructure unlike the prevalent road pavement system, strict criteria should be applied for uniform and differential settlement of the pavement system.