• Geomechanics and Engineering
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• 제32권4호
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• pp.375-385
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• 2023

There are many joint fissures distributed in the engineering rock mass. In the process of geological history, the underground rock mass undergoes strong geological processes, and undergoes complex geological processes such as fracture breeding, expansion, recementation, and re-expansion. In this paper, the damage-stick-slip process (DSSP), an analysis model used for rock mass failure slip, was established to examine the master control and time-dependent mechanical properties of the new and primary fractures of a multi-fractured rock mass under the action of stress loading. The experimental system for the recemented multi-fractured rock mass was developed to validate the above theory. First, a rock mass failure test was conducted. Then, the failure stress state was kept constant, and the fractured rock mass was grouted and cemented. A secondary loading was applied until the grouted mass reached the intended strength to investigate the bearing capacity of the recemented multi-fractured rock mass, and an acoustic emission (AE) system was used to monitor AE events and the update of damage energy. The results show that the initial fracture angle and direction had a significant effect on the re-failure process of the cement rock mass; Compared with the monitoring results of the acoustic emission (AE) measurements, the master control surface, key blocks and other control factors in the multi-fractured rock mass were obtained; The triangular shaped block in rock mass plays an important role in the stress and displacement change of multi-fracture rock mass and the long fissure and the fractures with close fracture tip are easier to activate, and the position where the longer fractures intersect with the smaller fractures is easier to generate new fractures. The results are of great significance to a multi-block structure, which affects the safety of underground coal mining.

• 터널과지하공간
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• 제14권3호
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• pp.215-228
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• 2004

지하암반의 변형은 단층, 절리 등의 불연속면을 따라 발생하므로 불연속면의 역학적 특성과 공간적인 분포형태는 구조물의 안정성에 근 영향을 미친다. 한편 연약암반에 높은 응력이 작용하는 경우에는 불연속면뿐만 아니라 무결암에서의 변형이 구조물의 안정성에 영향을 줄 수 있다. 이 연구에서는 암반구조물의 안정성 해석을 위하여 무결암과 절리, 그리고 록볼트를 점소성(visco-plastic) 재료로 가정하고, 연속체 개념을 적용하여 유변학적 모델(Rheological model)에 기초한 2차원 점소성 유한요소 프로그램을 개발하였다. 무결암 모델, 절리암반 모델, 록볼트로 보강된 절리암반 모델의 분석을 통하여 개발된 프로그램을 검증하였고, 각각의 모델에서 무결암의 해석 조건(탄성/점소성)에 따른 변위의 차이를 알아보았다. 연약암반에 높은 응력이 작용할 때, 무결암을 탄성으로 해석한 경우보다 점소성으로 해석한 경우에서 지하구조물의 변위가 더 크게 나타났다. 따라서 연약암반 내 지하구조물의 안정성 해석을 위해서는 절리와 록볼트 뿐만 아니라 무결암에 대해서도 점소성 모델을 적용하는 것이 바람직한 것으로 판단되었다.

• Geomechanics and Engineering
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• 제25권3호
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• pp.179-194
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• 2021

In this paper, to study the stability of surrounding rock during roadway excavation in different rock mass structures, the physical model test for roadway excavation process in three types of intact rock mass, layered rock mass and massive rock mass were carried out by using the self-developed two-dimensional simulation testing system of complex underground engineering. Firstly, based on the engineering background of a deep mine in eastern China, the similar materials of the most appropriate ratio in line with the similarity theory were tested, compared and determined. Then, the physical models of four different schemes with 1000 mm (height) × 1000 mm (length) × 250 mm (width) were constructed. Finally, the roadway excavation was carried out after applying boundary conditions to the physical model by the simulation testing system. The results indicate that the supporting effect of rockbolts has a great influence on the shallow surrounding rock, and the rock mass structure can affect the overall stability of the surrounding rock. Furthermore, the failure mechanism and bearing capacity of surrounding rock were further discussed from the comparison of stress evolution characteristics, distribution of stress arch, and failure modes in different schemes.

• Geomechanics and Engineering
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• 재33권6호
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• pp.553-565
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• 2023

As the structure of broken rock mass is complex, with obvious discontinuity and anisotropy, it is generally necessary to reinforce broken rock mass using grouting in underground construction. The purpose of this study is to experimentally investigate the mechanical properties of broken rock mass after grouting reinforcement with consideration of the characteristics of broken rock mass (i.e., degree of fragmentation and shape) and a range of reinforcement methods such as relative strength ratio between the broken rock mass and cement-based grout stone body (λ), and volumetric block proportion (VBP) representing the volumetric ratio of broken rock mass and the overall cement grout-broken rock mass mixture after the reinforcement. The experimental results show that the strength and deformation of the reinforced broken rock mass is largely determined by relative strength ratio (λ) and VBP. In addition, the enhancement in compressive strength by grouting is more obvious for broken rock mass with spherical shape under a relatively high strength ratio (e.g., λ=2.0), whereas the shape of rock mass has little influence when the strength ratio is low (e.g., λ=0.1). Importantly, the results indicate that columnar splitting failure and inclined shear failure are two typical failure modes of broken rock mass with grouting reinforcement.

• Structural Engineering and Mechanics
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• 제51권5호
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• pp.823-845
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• 2014

Success in the excavation of foundations is commonly known as being very important in asserting stability. Furthermore, when the subjected formation is rocky and the use of explores is required, the demands of successful blasting are multiplied. The quick and correct estimation of excavation's characteristics may help the design of building structures, increasing their safety. The present paper proposes a new classification system which connects blastability and rock mass quality. This new system primarily concerns poor and friable rock mass, heavily broken with mixture of angular and rounded rock pieces. However, it should concern medium and good quality rock mass. The Blastability Quality System (BQS) can be an easy and widely - used tool as it is a quick calculator for blastability index (BI) and rock mass quality. Taking into account the research calculations and the parameters of BQS, what has been at question in this paper is the effect of BI magnitude on a geological structure.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.58-63
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• 2009

Biaxial compression test was conducted on a transversely isotropic synthetic jointed rock model for the understanding of the fracture behaviors of a sedimentary or metamorphic rocks with well developed bedding or foliation in uni-direction. The joint angles employed for the model are 30, 45, and 60 degrees to the horizontal, and the synthetic rock mass was made of early strength cement. From the biaxial compression test, initiation propagation of tensile cracks at norm to the joint angle was found. The propagated tensile cracks eventually developed rock blocks, which was dislodged from the rock mass. Furthermore, the propagation process of the tensile cracks varies with joint angle: lower joint angle model shows more stable and progressive tensile crack propagation. The experiment results were validated from the simulation by using discrete element method PFC 2D. From the simulation, as has been observed from the test, a rock mass with lower joint angle produces wider damage region and rock block by tensile cracks. In addition, a rock model with lower joint angle shows a progressive tensile cracks generation around the opening from the investigation of the interacted tensile cracks.

• 한국지반공학회논문집
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• 제33권11호
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• pp.83-95
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• 2017

본 연구는 절리가 형성된 암반지층에서 암석종류, 절리경사각, 토압계수 및 지하수조건을 달리할 때 굴착벽체에 발생하는 토압의 크기 및 분포에 대해서 조사하였다. 모형실험(Son and Park, 2014)에 근거하여 확장연구를 수행하였으며, 이 때 암반-구조 상호작용과 암반의 절리특성을 고려하기 위하여 개별요소법을 이용한 수치해석을 수행하였다. 본 연구로부터 굴착벽체에 작용하는 토압은 암석종류, 절리경사각 및 토압계수 뿐만 아니라 지하수조건에 의해서 크게 영향을 받는다는 것을 파악하였다. 이와 더불어 본 연구로부터 조사된 토압을 토사지반에 적용되는 Peck의 경험토압과 비교하였으며, 이를 통해 절리형성 암반지층 굴착벽체에 발생하는 토압은 토사지반에서 발생하는 토압과 크게 다를 수 있다는 것을 확인하였다.

• Geomechanics and Engineering
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• 제30권6호
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• pp.503-515
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• 2022

The permeability coefficient is an essential parameter for the study of seepage flow in fractured rock mass. This paper discusses the feasibility and application value of using readily available RQD (rock quality index) data to estimate mine water inflow and grouting quantity. Firstly, the influence of different fracture frequencies on permeability in a unit area was explored by combining numerical simulation and experiment, and the relationship between fracture frequencies and pressure and flow velocity at the monitoring point in fractured rock mass was obtained. Then, the stochastic function generation program was used to establish the flow analysis model in fractured rock mass to explore the relationship between flow velocity, pressure and analyze the universal law between fracture frequency and permeability. The concepts of fracture width and connectivity are introduced to modify the permeability calculation formula and grouting formula. Finally, based on the on-site grouting water control example, the rock mass quality index is used to estimate the mine water inflow and the grouting quantity. The results show that it is feasible to estimate the fracture frequency and then calculate the permeability coefficient by RQD. The relationship between fracture frequency and RQD is in accordance with exponential function, and the relationship between structure surface frequency and permeability is also in accordance with exponential function. The calculation results are in good agreement with the field monitoring results, which verifies the rationality of the calculation method. The relationship between the rock mass RQD index and the rock mass permeability established in this paper can be used to invert the mechanical parameters of the rock mass or to judge the permeability and safety of the rock mass by using the mechanical parameters of the rock mass, which is of great significance to the prediction of mine water inflow and the safety evaluation of water inrush disaster management.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.1484-1489
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• 2005

An inhomogeneous and anisotropic rock has different properties at different location. Thus, this refers to any of the properties which we may be measuring. There are two concepts of rock mass, namely, CHILE(Continuous, Homogeneous, Isotropic, Linear Elastic) material and DIANE(Discontinuous, Inhomogeneous, Anisotropic, Non-linear Elastic) rock. The former is essentially the properties of intact rock, the latter is essentially the properties governed by the structure of rock. In geotechnical aspect, the most important parameter is strength of rock or rock mass. In particular, characteristics of strength of rock mass depend upon the orientation of discontinuities And this orientation of discontinuities has different properties at different direction of excavation. Therefore, it needs for characterization of different properties of discontinuity orientation against different direction of excavation.

• 한국터널지하공간학회 논문집
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• 제9권3호
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• pp.275-286
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• 2007

지하암반에서 지하구조물을 구축하는 경우, 지하구조물의 안정성 확보를 위한 굴착, 지보 및 대책공법은 현지 암반응력의 크기 및 방향에 큰 영향을 받게 된다. 따라서 터널과 같은 지하구조물의 설계와 안정성 해석에 있어서 현지 암반응력의 분포특성을 고려하는 것은 대단히 중요한 문제라고 할 수 있다. 본 연구에서는 암반응력을 고려한 터널설계 사례를 통하여 합리적이고, 안정적인 지하구조물 설계 방안에 대하여 고찰하고자 하였다 이를 위하여 Q-System에 의한 암반분류시 입력변수인 응력저감계수(SRF) 평가과정 및 표준지보패턴 설계 사례에 대하여 검토하였다. 또한 터널안정성 해석시 측압계수 크기 및 주응력 방향을 변수로 한 수치해석을 수행하여 터널 안정성 해석시 개선사항에 대하여 제안하였다.