• Geotechnical Engineering
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• v.12 no.4
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• pp.61-74
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• 1996

Settlement induced by low -level vibration on granular soils is too complect to predict with one or two fact ors. Factors affecting vibration induced settlement were investigated, and a settlement prediction model on granular soils was developed using multifactorial experimental design(MED). Factors such as vibration amplitude, deviatoric stress, confining pressure, soil gradation, duration of vibration, moisture content, and relative density were considered in this study. A special vibratory frame was designed to shake a soil specimen within a triaxial cell. MED allowed the authors to investigate the effect of many factors using a relatively small number of experiments. The most significant factors on settlement were vibrati on amplitued, confining pressure, and defiatoric stress. Comparable settlement was occurred even under low-level vibration ranging from 2.5 to 18mm1sec, and stress am sotropy was found to be an important factor on settlement.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.1
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• pp.133-141
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• 2020

Korea Infrastructure Safety and Technology Corporation (KISTEC) specifies that the safety inspection and precise safety diagnosis of concrete structures shall be conducted in accordance with the 'Special Law on Safety Management of Infrastructure'. The detailed safety inspection and precise safety diagnosis guidelines presented by KISTEC, however, gives only the grade of members and structures, and thus it is impossible to quantify remaining service life (RSL) of the structures and to quantitatively reflect the effect of differential settlements on the RSL. Therefore, this study aims to develop a RSL evaluation model considering the differential settlements. To this end, a simple equation was proposed based on the correlations between differential settlements and angular distortion, by which the angular distortion of structures was then reflected in nominal strengths of structural members. In addition, the effects of the differential settlements on the RSL of structures were analyzed in detail by using the safety diagnosis results of actual concrete structure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1C
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• pp.53-62
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• 2008

A constitutive model, which can simulate the effect of principal stress rotation associated with direct simple shear test, is proposed in this study. The model is based on two mobilized planes. The plastic strains occur from the two mobilized planes, and depend on stress state, and they are added. The first plane is a plane of maximum shear stress, which rotates about the horizontal axis, and the second plane is a horizontal plane which is spatially fixed. The second plane is used to consider the effect of principal stress rotation on simple shear tests under different stress states. The soil skeleton behavior observed in drained simple shear tests is captured in the model. This constitutive model is incorporated into the dynamic coupled stress-flow finite difference program FLAC. The model is first calibrated with drained simple shear tests on loose Fraser River sand. The measured shear stress and volume change are partially induced by principal stress rotation and compared with model calculations. The model is verified by comparing predicted and measured settlements due to rigid footing resting on loose sands. Settlements predicted by the proposed model were very similar to measured settlements. Mohr-Coulomb model can not consider the effect of principal stress rotation and its prediction was only 20% of measured settlements.

• Journal of the Korean GEO-environmental Society
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• v.8 no.6
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• pp.29-36
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• 2007

The control and prediction of surface settlement, gradient and ground displacement are the main factors in urban tunnel construction. This paper carried out the estimation and prediction of ground behavior around tunnel due to excavation using computational method and case study in detail for the analysis of deformation behavior in urban NATM tunnel. Computational method was performed by FLAC-2D with strain softening model and elastic plastic model. Field measurements of surface subsidence and ground displacement were adopted to monitor the ground behavior resulting from the tunneling and these values were applied to modify tunnel design parameters on construction.

• Tunnel and Underground Space
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• v.18 no.6
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• pp.436-446
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• 2008

The volumetric expansion ratio of rock mass on the subsidence occurrence area can explain why the depth of the surface subsidence is lower than the height of an opening; it is because the empty space of the gangway is filled with the broken rock. But, until now, when the surface subsidence mechanism is studied without consideration of the volumetric expansion ratio, it is usually overlooked that the amount of subsidence occurrence can be overestimated. Therefore, in this study, the authors researched the subsidence occurrence mechanism with a new theoretical approaching method. The volumetric expansion ratio obtained from this method has been applied to the numerical simulations. The authors adopted the UDEC(Universal Distinct Element Code) for their discontinuum numerical analysis, because this program has an advantage for analyzing the behavior of rock discontinuities.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.6
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• pp.914-921
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• 2010

When industrial structures are constructed on soft ground, ground subsidence is occurred by problems of bearing capacity. To protect ground subsidence have to improve soft ground, and have to predict settlement estimation for reasonable construction. Artificial Neural Networks(ANN) is adopted for prediction of settlement of construction during the initial design. In the study, Artificial Neural Networks are applied to predict the settlement estimation of initial condition ground and ground improved by D.C.M method. Also, this study compares results of Artificial Neural Networks and results of continuum analysis using Mohr-Coulomb models. In result, settlements of initial condition ground decreased over 0.7 times. Also, by comparing ANN and continuum analysis, coefficient of determination was comparatively high value 0.79. Thought this study, it was confirmed that settlements of improvement ground is predicted using laboratory experiment data.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.512-515
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• 2011

터널 해석은 주로 지표침하와 터널 라이닝 내 단면력 산정에 초점이 맞춰지며 이는 시공단계를 고려한 3차원 수치해석 모델을 이용해 결정할 수 있다. 수치해석 시 shield는 응력 제어, shell element로 모델링하는 방법 등으로 모사될 수 있다. 한편 변위 제어를 통한 쉴드 모사는 shield를 적절한 경계조건으로 처리함으로서, 다른 shield 모사 방법에 비해 모델링 작업을 간소화하고 해석의 효율성을 높일 수 있다. 본 연구에서는 변위 제어에 의한 shield 모사를 위한 적정 경계조건을 제안한다. 이를 위해 시공단계가 고려된 유한요소해석을 사용하여, 쉴드 및 굴착면에서의 경계조건 변화와 이에 따른 지표침하 관측 수행하였다. 제안된 shield 변위 제어로부터 얻어진 해석결과를 이론적인 해와 비교함으로서, 제시된 shield 모델링 방법의 적정성과 지반 거동 변화를 평가하고자 한다. 해석 결과는 지반 모델의 지표침하를 기준으로 관찰되었으며, 변위제어에 의한 결과와 요소에 의한 모델링 결과가 유사하게 얻어짐을 보여준다. 또한 변위제어의 쉴드 모사에서 회전 구속보다 변위 구속 조건에 지배적으로 영향을 받음을 확인하였다.

• International Journal of Highway Engineering
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• v.13 no.3
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• pp.7-14
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• 2011

The numerical analyses were performed to investigate the curling behavior of the post-tensioned prestressed concrete approach slab (PTAS) under environmental loads. A technique to include properly the boundary conditions of one end of PTAS that was connected to the bridge abutment using hinges was proposed for the numerical model. The applicability of a simplified model not having hunches was also investigated. By using the developed models, the curling behavior of PTAS was analyzed when the foundation settlement occurred. The analysis results showed that the maximum tensile stress obtained from the simplified model involving a simplified hinge connection was very closed to that obtained from a rigorous model. When the slab curled up, the maximum tensile stress occurred in the model including no foundation settlement, but when the slab curled down, the maximum stress occurred in the model including partial settlement of the foundation. Therefore, the design of PTAS should be performed considering those maximum tensile stresses.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.3
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• pp.305-317
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• 2015

This paper is to perform 3-dimensional numerical analysis considering face pressure, backfill pressure, excavation length, soil model and element size for selecting key factors of ground surface settlement due to shield TBM advancement. According to the numerical analysis results, backfill pressure and soil model are governing factors inducing ground surface settlement. To complement this study, the ground conditions and characteristics of the boring machine will be considered using numerical analysis.

• Korean Journal of Agricultural Science
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• v.25 no.2
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• pp.235-246
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• 1998

This study was performed to find the effect of parameters of numerical analysis model. To find the parameters of numerical analysis model, triaxial test and consolidation test were conducted and the results were compared and analyzed with various methods. Preloaded ground was analyzed with Hyperbolic and Modified Cam-Clay models. Hyperbolic model analysis result was good agreement with measured lateral displacement, and Modified Cam-Clay model agreed more than Hyperbolic model with settlement. When the parameters of models were changed, change of settlement on center of embankment and of maximum lateral displacement on distance 5m from end of embankment were compared. On Hyperbolic model the parameter K has large influence on settlement and lateral displacement. On Modified Cam-Clay model the parameters ${\Gamma}$ and M have large influence on settlement and lateral displacement, respectively.