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탄성계수 감소곡선에 근거한 철도노반의 회복탄성계수 모델 개발 및 평가
박철수(Park Chul-Soo),황선근(Hwang Seon-Keun),최찬용(Choi Chan-Yong),목영진(Mok Young-Jin) 한국철도학회 2008 한국철도학회 학술발표대회논문집 Vol.- No.-
This study focused on the resilient modulus prediction model, which is the functions of mean effective principal stress and axial strain, for three types of railroad trackbed materials such as crushed stone, weathered soil, and crushed-rock soil mixture. The model is composed with the maximum Young"s modulus and nonlinear values for higher strain in parallel with dynamic shear modulus. The maximum values is modeled by model parameters, A<SUB>E</SUB> and the power of mean effective principal stress, n<SUB>E</SUB>. The nonlinear portion is represented by modified hyperbolic model, with the model parameters of reference strain, εr and curvature coefficient, a. To assess the performance of the prediction models proposed herein, the elastic response of a test trackbed near PyeongTaek, Korea was evaluated using a 3-D nonlinear elastic computer program (GEOTRACK) and compared with measured elastic vertical displacement during the passages of freight and passenger trains. The material types of sub-ballasts are crushed stone and weathered granite soil, respectively. The calculated vertical displacements within the sub-ballasts are within the order of 0.6㎜, and agree well with measured values with the reasonable margin. The prediction models are thus concluded to work properly in the preliminary investigation.
탄성계수 감소곡선에 근거한 철도노반의 회복탄성계수 모델 개발 및 평가
박철수(Park Chul Soo),황선근(Hwang Seon Keun),최찬용(Choi Chan Yong),목영진(Mok Young Jin) 대한토목학회 2009 대한토목학회논문집 C Vol.29 No.2
본 연구에서는 국내 철도 토공노반 재료로 가장 흔히 사용되는 입도조정쇄석, 화강풍화토, 암버럭-토사 혼합 재료에 대해 평균유효주응력과 축변형률의 함수로 표현되는 회복탄성계수 예측모델을 결정하였다. 회복탄성계수 예측모델은 대표적인 동적물성치인 변형률에 따른 전단탄성계수 감소곡선의 표현과 같이 최대영탄성계수와 정규화 영탄성계수 감소곡선으로 구성된다. 평균유효주응력의 함수로 표현되는 최대영탄성계수의 모델인자는 A<SUB>E</SUB>와 n<SUB>E</SUB>이고, 비선형 영역의 정규화 영탄성계수 감소곡선은 기준변형률(ε<SUB>r</SUB>)과 곡률계수(a)를 모델인자로 하는 수정 쌍곡선 모델로 표현된다. 제안된 회복탄성계수 예측모델을 검증하기 위해 3차원 다층탄성해석 프로그램(GEOTRACK)을 이용하여 평택 시험 철도노반의 탄성거동을 평가하였고, 화물열차 및 여객열차가 시험구간을 통과할 때 계측한 노반의 수직 탄성변위와 비교하였다. 현장계측은 자갈도상 아래의 재료가 각각 입도조정쇄석과 양질의 화강풍화토인 두 개소에서 수행되었다. 자갈도상 아래에서 계산된 수직 탄성변위는 대략 0.6㎜ 이내였고 계측 결과와 잘 일치하였다. 본 연구를 통해 제안된 회복탄성계수 예측모델이 열차하중에 의한 노반의 탄성거동을 적절히 표현하고 있음을 확인하였다. This study is to develope the resilient modulus prediction model, which is the function of mean effective principal stress and axial strain, for three types of railroad trackbed materials such as crushed stone, weathered granite soil, and crushed-rock soil mixture. The model consists of the maximum Young's modulus and nonlinear values for higher strain, analogous to dynamic shear modulus. The maximum value is modeled by model parameters, A<SUB>E</SUB> and the power of mean effective principal stress, n<SUB>E</SUB>ㆍThe nonlinear portion is represented by modified hyperbolic model, with the model parameters of reference strain, ε<SUB>r</SUB> and curvature coefficient, a. To assess the performance of the prediction models proposed herein, the elastic response of a test trackbed near PyeongTaek, Korea, was evaluated using a 3-D elastic multilayer computer program (GEOTRACK). The results were compared with measured elastic vertical displacement during the passages of freight and passenger trains at two locations, whose sub-ballasts were crushed stone and weathered granite soil, respectively. The calculated vertical displacements of the sub-ballasts are within the order of 0.6㎜, and agree well with measured values. The prediction models are thus concluded to work properly in the preliminary investigation.
목영진(Mok Young-Jin),박철수(Park Chul-Soo),임정열(Lim jeong-Yeul),최충락(Choi Choong-Lak) 한국철도학회 2007 한국철도학회 학술발표대회논문집 Vol.- No.-
Reinforced roadbeds are valued from the point of view of maintenance as well as enhanced mechanical capacity. They support more train load and less transmit to the sub-layers than general roadbeds. Also, the lateral sloping surface of the reinforced roadbed and its low permeability, achieved by the controlled compaction, increase drainage capability and prevent the softening of sub-layers. In the study, a series of cross-hole tests was performed to observe the temporal changes in the stiffness of reinforced roadbeds, if any, due to the cyclic loading of trains and alternating rainy and frozen seasons at Pyeong-taek experimental site. The three types of reinforced roadbed materials are slag, crushed stones, and soils, and the thickness of all the reinforced roadbeds is 0.8m. The stiffness of the slag and soil reinforced roadbeds was not changed or slightly decreased. The stiffness of the crushed stone was somewhat increased and is inferred to being densified close to surface.