Journal of the Korean GEO-environmental Society (한국지반환경공학회 논문집)

Korean Geo-Environmental Society (한국지반환경공학회)
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Effect of Rock Discontinuities on Dynamic Shear Stress Wave

암반 불연속면이 동적 전단응력파에 미치는 영향

  • Son, Moorak (Department of Civil Engineering, Daegu University)
  • Received : 2018.09.07
  • Accepted : 2018.11.14
  • Published : 2018.12.01
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Abstract

This paper investigates the effect of rock discontinuities on a shear stress wave that is induced by earthquake or blasting and provides the result of numerical parametric studies. The numerical tests of different conditions of rock and discontinuity have been carried out after confirming that the numerical approach is valid throughout a verification analysis from which the test results were compared with a theoretical solution. In-situ stress condition was considered as a rock condition and internal friction angle and cohesive value, which are the shear strength parameters, were considered as discontinuities condition. The joint inclination angle was also taken into account as a parameter. With the various conditions of different parameters, the test results showed that a shear stress wave propagating through a mass is highly influenced by the shear strength of discontinuities and the condition of joint inclination angle as well as in-situ stress. The study results indicate that when earthquake or blasting-induced dynamic loading propagates through a jointed rock mass or a stratified soil ground the effect of in-situ stress and discontinuities including a stratum boundary should be taken into account when evaluating the dynamic effect on nearby facilities and structures.

본 논문은 암반에 형성되어 있는 불연속면이 지진 또는 발파에 의해 유발되어 암반을 통해 전달되는 동적 전단응력파에 미치는 영향에 대해서 수치해석적 매개변수 연구를 통해 조사하고 그 결과를 제시하는 것이다. 수치해석적 매개변수 연구를 수행하기 위해서 먼저 이론적 해를 얻을 수 있는 조건에 대해서 타당성해석을 수행하고 그 결과를 이론해와 비교한 후 암반조건 및 불연속면 조건을 달리한 경우에 대해서 매개변수해석을 수행하였다. 암반조건으로는 암반 초기 현장응력 상태가 고려되었으며 불연속면조건으로서는 불연속면의 전단강도 정수인 마찰각과 점착력이 고려되었다. 또한 불연속면의 경사각 또한 매개변수로서 고려되었다. 이와 같은 다양한 조건의 매개변수연구를 통해 전단응력파의 변화를 파악한 결과, 매질을 통해 전달되는 동적 전단응력파는 암반의 초기 현장응력조건 뿐만 아니라 불연속면의 전단강도 및 경사각 조건에 크게 영향을 받는 것으로 나타났다. 이를 통해 지진 또는 발파유발 동적하중이 절리형성 암반지층이나 서로 다른 지층으로 이루어진 토사지층을 통과할 때, 지층의 초기응력 상태와 더불어 불연속면 또는 지층경계면의 특성 등을 반드시 고려하여 주변시설물 및 구조물에 대한 동적영향을 파악해야 할 것으로 판단된다.

Keywords

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Fig. 1. Model of wave propagation in a mass containing a planar joint

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Fig. 2. Comparison of Miller’s analytical solutions and numerical tests

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Fig. 3. Effect of in-situ stress (𝜙 = 0, c = 0.1 MPa, σt = 0)

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Fig. 4. Effect of friction angle at joint (In-situ stress = 1.0 MPa, c = 0.1 MPa, σt = 0)

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Fig. 5. Effect of friction angle at joint (In-situ stress = 1.0 MPa, 𝜙 = 30°, σt = 0)

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Fig. 6. Effect of joint inclination angle (In-situ stress = 1.0 MPa, 𝜙 = 30°, c = 0.1 MPa, σt = 0)

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Fig. 7. Change of transmission, reflection, and absorption coefficients with joint inclination

Table 1. Properties and conditions in the numerical simulations

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