열-수리-역학 거동 해석을 위한 경계면 요소의 수식화

신호성,윤석 한국지반공학회 2022 한국지반공학회논문집 Vol.38 No.9

Because discontinuity in the rock mass and contact of soil-structure interaction exhibits coupled thermal-hydro- mechanical (THM) behavior, it is necessary to develop an interface element based on the full governing equations. In this study, we derive force equilibrium, fluid continuity, and energy equilibrium equations for the interface element. Additionally, we present a stiffness matrix of the elastoplastic mechanical model for the interface element. The developed interface element uses six nodes for displacement and four nodes for water pressure and temperature in a two-dimensional analysis. The fully coupled THM analysis for fluid injection into a fault can model the complicated evolution of injection pressure due to decreasing effective stress in the fault and thermal contraction of the surrounding rock mass. However, the result of hydromechanical analysis ignoring thermal phenomena overestimates hydromechanical variables.

한국의료패널 자료를 통해 살펴본 입원의료이용의 수도권 및 상급종합병원 집중 현상

신호성 대한의사협회 의료정책연구소 2015 의료정책포럼 Vol.13 No.1

Doping effect of Oxidized Molybdenum Ditelluride by Ultraviolet Ozone treatment

신호성,문인용,이성원,유원종 한국진공학회 2021 한국진공학회 학술발표회초록집 Vol.2021 No.2

The development of low-resistance source/drain contacts to transition-metal dichalcogenides (TMDCs) is crucial for the realization of high-performance logic components. Using a convenient and effective method, ultraviolet ozone treatment, molybdenum ditelluride (MoTe₂) can be p-type doped and become molybdenum oxide (MoOx, x<3). MoOx acts as an efficient hole injection layer, so adjacent layer of other TMDCs get p-type doped through charge carrier transfer. In this study, we performed Raman, AFM, and current-voltage characteristics to compare the properties of MoTe₂ before and after UVO treatment.

대변형을 고려한 연약지반 압밀해석

신호성,김윤태,김주용,이승래 대한토목학회 1996 대한토목학회 학술발표회 논문집 Vol.1996 No.3

탄성영역이 없는 J2-경계면 소성모델

신호성,오세붕,김재민 대한토목학회 2023 대한토목학회논문집 Vol.43 No.4

Soil plasticity models for cyclic and dynamic loads are essential in non-linear numerical analysis of geotechnical structures. While a single yield surface model shows a linear behavior for cyclic loads, J2-bounding surface plasticity model with zero elastic region can effectively simulate a nonlinearity of the ground response with the same material properties. The radius of the yield surface inside the boundary surface converged to 0 to make the elastic region disappear, and plastic hardening modulus and dilatancy define plastic strain increment. This paper presents the stress-strain incremental equation of the developed model, and derives plastic hardening modulus for the hyperbolic model. The comparative analyses of the triaxial compression test and the shallow foundation under the cyclic load can show stable numerical convergence, consistency with the theoretical solution, and hysteresis behavior. In addition, plastic hardening modulus for the modified hyperbolic function is presented, and a methodology to estimate model variables conforming 1D equivalent linear model is proposed for numerical modeling of the multi-dimensional behavior of the ground. 반복하중이나 동적하중에 대한 지반의 소성모델은 지반구조물의 비선형 수치해석에 매우 중요하다. 단일 항복면 모델은 반복하중에 대해 선형적 거동을 보이는 반면, 개발된 탄성영역이 없는 J2-경계면 소성모델은 동일한 물성치로 효과적으로 지반의 비선형성을 모사할 수 있다. 경계면 내부 항복면의 반경을 0으로 수렴시켜 탄성영역이 사라지도록 수식화하고, 소성경화 계수과 팽창률을 이용하여 소성변형 증분을 정의하였다. 개발된 모델의 응력-변형률 증분식을 제시하고, 쌍곡선 모델에 대한 소성경화 계수를 유도하였다. 삼축압축조건과 얕은기초의 반복하중에 대한 비교해석은 개발된 모델의 안정적인 수렴성, 이론식과의 일치성, 그리고 이력경로을 보여 주었다. 또한, 수정된 쌍곡선함수에 대한 소성경화 계수를 제시하여, 1차원 등가선형모델에 부합하는 모델변수 산정법을 제안하여 지반의 다차원 거동을 모델링할 수 있도록 하였다.

치과 의료기기 유통기업의 규모별 창업 및 성장 전략 - 통합적 모델 연구

신호성,유재원 한국창업학회 2016 한국창업학회지 Vol.11 No.1

토석류 유동해석을 위한 유한요소 수식화

신호성 한국지반공학회 2014 한국지반공학회논문집 Vol.30 No.10

최근 토석류의 이동 메커니즘에 대한 연구와 거동 예측을 위한 해석 프로그램의 개발이 활발히 진행중이다. 하지만, 토석류를 유체이동으로 간주하는 기존의 프로그램들은 수치적인 안정성과 모델링 그리고 다양한 경계조건의적용에 대한 제약이 있다. 본 연구에서는 토석류의 유동현상에 대한 연속방정식과 힘평형 방정식에 대하여 깊이적분을 수행하였다. 토체의 두께 h,x와 y흐름방향의 평균속도 u,v를 주변수로 채택하여 흐름이 없는 해석영역에대한 수치적인 안정성을 확보하였다. DG기법에 의한 가중행렬을 산정하고 유동방향을 고려한 불연속 시험함수를이용하여 Petrov-Galerkin 수식화를 수행하였다. 그리고 토석류의 유체 및 토립자의 특성을 동시에 고려할 수 있는역학적 구성모델을 제시하였다. 단일경사 사면에서 사면경사, 토사 유발량, 저면 마찰 저항이 토석류 흐름특성에 미치는 영향을 비교 분석하였다. 그리고 수치해석을 통하여 사면 하부에 설치된 제방의 영향을 분석하였다. 개발된 해석프로그램을 활용하여 토석류 발생예상 지역의 다양한 위험인자에 대한 평가를 수행하고, 피해를 최소화하기 위한 시설물의 설계방안을 제안할 수 있을 것으로 판단된다.

동토지반에 대한 역학적 구성모델

신호성,김지민,이장근,이승래 한국지반공학회 2012 한국지반공학회논문집 Vol.28 No.5

Recently, growing interests in frozen ground have stimulated us to advance fundamental theories and systematic researches on soil behavior under freezing conditions. Unlike the well-established soil mechanics theory, temperature variation and phase change of pore-water cause water migration to cold side, ground heaving, sharp increase in earth pressure, etc., which bring about serious problems in frozen geotechnical structures. Elasto-plastic mechanical constitutive model for frozen/unfrozen soil subjected to fully coupled THM phenomena is formulated based on a new stress variable that is continuous in frozen-unfrozen transitional regions. Numerical simulations are conducted to discuss numerical reliability and applicability of the developed constitutive model: one-dimensional heaving pressure, tri-axial compression test, and one-side freezing tests. The numerical results show that developed model can efficiently describe complex THM phenomena of frozen soil, and they can be utilized to analyze and design the geotechnical structures under freezing conditions, and predict their long-term behavior

Development of Rainfall Hazard Envelope for Unsaturated Infinite Slope

신호성,김윤태,박덕근 대한토목학회 2013 KSCE JOURNAL OF CIVIL ENGINEERING Vol.17 No.2

Rainfall during summer season is one of the major causes of slope failure in Korea, especially in unsaturated weathered granite soils. The current slope design procedure for the rainy season is to just raise the ground-water level, which is not adequate for the unsaturated soil slope. Previous rainfall hazard envelopes only tend to use rainfall intensity and duration as the main variables, not considering mechanical and hydraulic characteristics of unsaturated soils. The general equation for Factor of Safety (FS) in infinite unsaturated slopes is derived to consider the rainfall infiltration. The three important factors governing the equation are as follows:rainfall characteristics such as intensity and duration to determine a wetting front depth using an infiltration model, shear strength theory for unsaturated soil, and variation of suction profile during rainfall. The minimal FS is calculated from the FS profile with depth for a given rainfall intensity and duration, and a rainfall hazard envelope considering soil infiltration characteristics is built for a given slope angle. The procedure to develop a hazard envelope for various slope angles is applied to three unsaturated weathered granite soils in Korea.

메탄 하이드레이트 생산 묘사를 위한 수치도구의 개발

신호성 한국지반공학회 2014 한국지반공학회논문집 Vol.30 No.9

Methane gas hydrate which is considered energy source for the next generation has an urgent need to develop reliable numerical simulator for coupled THM phenomena in the porous media, to minimize problems arising during the production and optimize production procedures. International collaborations to improve previous numerical codes are in progress, but they still have mismatch in the predicted value and unstable convergence. In this paper, FEM code for fully coupled THM phenomena is developed to analyze methane hydrate dissociation in the porous media. Coupled partial differential equations are derived from four mass balance equations (methane hydrate, soil, water, and hydrate gas), energy balance equation, and force equilibrium equation. Five main variables (displacement, gas saturation, fluid pressure, temperature, and hydrate saturation) are chosen to give higher numerical convergence through trial combinations of variables, and they can analyze the whole region of a phase change in hydrate bearing porous media. The kinetic model is used to predict dissociation of methane hydrate. Developed THM FEM code is applied to the comparative study on a Masuda’s laboratory experiment for the hydrate production, and verified for the stability and convergence.