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Yoon, Jeoung Seok,Stephansson, Ove,Zang, Arno,Min, Ki-Bok,Lanaro, Flavio Elsevier 2017 International journal of rock mechanics and mining Vol.98 No.-
<P><B>Highlights</B></P> <P> <UL> <LI> A work flow is developed for modelling fault rupture using discrete bonded particle modelling. </LI> <LI> Fault ruptures under various stress condition including future glaciation cycles simulated. </LI> <LI> Fault rupture properties are compared with scaling relations of natural tectonic earthquakes and show good agreement. </LI> </UL> </P>
FRACOD를 이용한 취성 암석의 손상 및 파괴에 대한 경계요소 해석
이희석(Hee-Suk Lee),Baotang Shen,Ove Stephansson 한국암반공학회 2004 터널과지하공간 Vol.14 No.4
응력 증가에 의한 취성 암석의 손상은 미세균열의 개시로부터 시작하여 각 개별 균열들의 전파 및 결합에 의해 거시적인 파괴면을 발생시킨다. 전통적으로 암반의 손상 및 파괴현상을 설명하기위해 거시적인 파괴 기준이나 탄소성 모델과 같은 연속체적인 접근법이 주류를 이루어왔다. 하지만 개별적인 균열들의 개시와 전파 과정을 명시적으로 고려할 수 있다면 현상론적인 관점에서 보다 실제에 가까운 암석 손상 및 파괴 과정을 재현할수 있을 것이다. 본 연구에서는 암석의 균열 진전 모델링을 위해 개발된 경계요소 코드인 FRACOD를 이용하여 암석의 손상 및 파괴 과정을 모사한 결과를 제시한다. 수치일축압축시험을 통해 개발된 모델의 적정성을 검증하고 암반의 치수효과를 고려한 현실적인 암석 파괴 과정을 재현하였다. 또한 이러한 접근법의 적용 사례로서, 실제 굴착이 진행중인 심부 수갱 암반 주변에서 심도와 암반 특성에 따라 균열 진전과 이에 따른 암반 손상의 범위를 예측한 결과를 제시하였다. 이 접근법은 취성도가 큰 암반에서 발생하는 안정성 문제에 대한 공학적인 해법을 찾는데 기여를 할 수 있을 것으로 기대된다. Damage in brittle rock due to stress increase starts from initiation of microcracks, and then results in failure by forming macro failure planes due to propagation and coalescence of these discrete cracks. Conventionally, continuum approaches using macro-failure criteria or a number of elasto-plastic models have been major solution to implement rock damage and failure. However, actual brittle failure processes can be better described in phenomenological approach if initiation and propagation of discrete fractures are explicitly considered. This study presents damage and failure process of rock using a boundary element code, FRACOD, which has been developed to model fracturing process of rocks. Through a series of numerical uniaxial compressive tests, the feasibility of the developed model was verified, and realistic rock failure process was reproduced considering scale effects in rocks. In addition, the fracturing process and the corresponding rock damage in the vicinity of deep shaft in rock mass were presented as an application of this approach. This approach will be expected to contribute to finding better engineering solutions for the analysis of stability problems in brittle rock masses.
Discrete element modeling of fluid injection-induced seismicity and activation of nearby fault
Yoon, Jeoung Seok,Zimmermann, Gü,nter,Zang, Arno,Stephansson, Ove Canadian Science Publishing 2015 Canadian geotechnical journal: Revue canadienne de Vol.52 No.10
<P> Enhanced geothermal systems, shale gas, and geological carbon sequestration all require underground fluid injection in high-pressure conditions. Fluid injection creates fractures, induces seismicity, and has the potential to reactivate nearby faults that can generate a large magnitude earthquake. Mechanisms of fluid injection-induced seismicity and fault reactivation should be better understood to be able to mitigate larger events triggered by fluid injection. This study investigates fluid injection, induced seismicity, and triggering of fault rupture using hydromechanical-coupled discrete element models. Results show that a small amount of fluid pressure perturbation can trigger fault ruptures that are critically oriented and stressed. Induced seismicity by rock failure shows in general higher b-values (slope of magnitude-frequency relation) compared to seismicity triggered by the fault fracture slip. Numerical results closely resemble observations from geothermal and shale-gas fields and demonstrate that discrete element modeling has the potential to be applied in the field as a tool for predicting induced seismicity prior to in situ injection. </P>