• 한국암반공학회:학술대회논문집
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• 한국암반공학회 2001년도 추계공동학술발표회 논문집
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• pp.115-120
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• 2001

In No. 1 tunnel for Kwnagju urban subway construction, net penetration rate of the shield TBM was analyzed. This tunnel of 540 m length is located in soil layers at starting and in hard rocks such as amphibolite and granitic gneiss at ending with 84 m length. The net penetration rate was dropped down to 2∼11 cm/hr in rock while 50∼80 cm/hr in soil. Theoretical penetration rate is analyzed in conditions of machine and rock in order to compare the actual net penetration rate. The relationships between net penetration rate and thrust force is also investigated in this report.

• Geomechanics and Engineering
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• 제34권1호
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• pp.103-113
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• 2023

This study focused on understanding the relationship between the design of a tunnel boring machine disc cutter ring and its rock-breaking efficiency, as well as the applicable conditions of different cutter ring types. The discrete element method was used to establish a numerical model of the rock-breaking process using disc cutters with different ring types to reveal the development of rock damage cracks and variation in cutter penetration load. The calculation results indicate that a sharp-edged (V-shaped) disc cutter penetrates a rock mass to a given depth with the lowest load, resulting in more intermediate cracks and few lateral cracks, which leads to difficulty in crack combination. Furthermore, the poor wear resistance of a conventional V-shaped cutter can lead to an exponential increase in the penetration load after cutter ring wear. In contrast, constant-cross-section (CCS) disc cutters have the highest quantity of crack extensions after penetrating rock, but also require the highest penetration loads. An arch-edged (U-shaped) disc cutter is more moderate than the aforementioned types with sufficient intermediate and lateral crack propagation after cutting into rock under a suitable penetration load. Additionally, we found that the cutter ring wedge angle and edge width heavily influence cutter rock-breaking efficiency and that a disc cutter with a 16 to 22 mm edge width and 20° to 30° wedge angle exhibits high performance. Compared to V-shaped and U-shaped cutters, the CCS cutter is more suitable for soft or medium-strength rocks, where the penetration load is relatively small. Additionally, two typical case studies were selected to verify that replacing a CCS cutter with a U-shaped or optimized V-shaped disc cutter can increase cutting efficiency when encountering hard rocks.

• Advances in concrete construction
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• 제16권2호
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• pp.119-126
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• 2023

Steel fiber reinforced self-compacting concrete (SFRSCC) has good workability such as high flowability and good cohesiveness. The workability, compressive strength, splitting tensile strength, and anti-penetration characteristics of three kinds of SFRSCC were investigated in this paper. The fraction of steel fibers of the SFRSCC is 0.5%, 1.5% and 2.0% respectively. The results of the static tests show that the splitting tensile strength increases with the increase of fraction of steel fibers, while the compressive strength of 1.5% SFRSCC is lowest. It is demonstrated that the anti-penetration ability of 1.5% SFRSCC subjected to a velocity projectile (200-500 m/s) is better than 0.5% and 2.0% SFRSCC according to the experimental results. Considering the steel fiber effects, the existing formula is revised to predict penetration depth, and it is revealed that the revised predicted depth of penetration is in good agreement with the experimental results. The conclusion of this paper is helpful to the experimental investigations and engineering application.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.633-636
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• 2006

Impact damage modeling of concrete under high strain rate loading conditions is investigated. A phenomenological penetration model that can account for complicated impact and penetration process such as the rate and loading history response of concrete, the microstructure-penetration interaction etc. is discussed. Constitutive law compatible with Second Law of thermodynamics and coupled damage and plasticity modelling based on continuum damage mechanics are also examined. The purpose of this paper is preliminarily to study with respect to impact and penetration models for concrete before the development of that model.

• Structural Engineering and Mechanics
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• 제13권6호
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• pp.639-652
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• 2002

The present study aims to improve an existing model for the prediction of deceleration time history, penetration depth and forces on ogive and conical nose shaped missiles under normal impact into geo-material targets. The actual ogive nose shaped missile has been considered in the analysis and the results thus obtained have been compared with the existing model and significant improvements are found. A close proximity in the results has also been observed with the experimental values. The results of ogive nose shaped missile have also been compared with equivalent conical nose shaped missile. Variation of radial stresses along nose length and radial direction has been studied. Effect of CRH on missile penetrating performance has been investigated.

• 터널과지하공간
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• 제2권1호
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• pp.177-189
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• 1992

As tunnel becomes longer and larger, TBM has become one of the most popular methods of excavatio in rock. This paper describes the degree of operation the degree of availability and penetration rate of TBM and TBE applied in Namsan roadway tunnelling site. Net penetration rate was 1.62m/hr for TBM and 0.72m/hr for TBE. Net penetration rate showed no direct relation to daily advance or penetration time, but the lower bound of penetration rate could be obtained from the relation with daily advance. For both of TBM and TBE, the degree of operation and the degree of availability were 33.8% and 68.6% respectively. Life time of normal cutter was $310m^3$ for TBM and $194m^3$ for TBE, while that of center and gauge cutter was about $50m^3$. When the two machines were compared, TBM showed 80% higher penetration rate, and 40% shorter life time of cutter.

• Structural Engineering and Mechanics
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• 제13권2호
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• pp.171-186
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• 2002

Static and dynamic penetration tests of reinforced concrete (RC) slab specimens are described and discussed. The experimental study was aimed at a better understanding of mechanisms that are involved in dynamic penetration, through their identification in static tests, and by establishing their relative influence in similar dynamic cases. The RC specimens were $80{\times}80-cm$ square plates, and they were made of 30 MPa concrete. The non-deforming steel penetrator was a 50-mm diameter steel rod with a conical nose of 1.5 aspect ratio. Impact penetration tests were carried out with an air gun, which launched the projectiles at velocities of up to 300 m/sec. The static tests were conducted using a closed loop displacement control actuator, where the penetrator was pushed at a constant rate of displacement into the specimen. The static tests reveal important mechanisms that govern the penetration process and therefore contribute to a better understanding of RC barriers resistance to non-deforming projectiles impact.

• 한국군사과학기술학회지
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• 제4권2호
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• pp.189-201
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• 2001

For a design of multi-layer armor, the extensive full scale or sub-scale penetration test data are required. In generally, the collection of penetration data is in need of time-consuming and expensive processes. However, the application of numerical or analytical method is very limited due to poor understanding about penetration mechanics. In this paper, we have developed a neural network analyzer which can be used as a design tool for a new armor. Calculation results show that the developed neural network analyzer can predict relatively exact penetration depth of a new armor through the effective analysis of the pre-existing penetration database.

• Computers and Concrete
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• 제7권2호
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• pp.87-102
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• 2010

This paper discusses new capabilities developed for the Virtual Penetration Laboratory (VPL) software package to address the challenges of determining Penetration Resistance (PR) equations for concrete materials. Specifically, the paper introduces a three-invariant concrete constitutive model recently developed by the authors. The Advanced Fundamental Concrete (AFC) model was developed to provide a fast-running predictive model to simulate the behavior of concrete and other high-strength geologic materials. The Continuous Evolutionary Algorithms (CEA) automatic fitting algorithms used to fit the new model are discussed, and then examples are presented to demonstrate the effectiveness of the new AFC model. Finally, the AFC model in conjunction with the VPL software package is used to develop a PR equation for a concrete material.

• 터널과지하공간
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• 제12권2호
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• pp.115-119
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• 2002

광주도시철도 1호선 건설공사에서 4개의 도심터널은 대구경 쉴드 TBM에 의한 굴착이 계획되었으며, 그 중에 No.1 터널 구간은 13개월 동안 굴착되었다. 본 연구에서는 이 기간동안의 순굴착속도 및 이의 추력과의 관계를 분석하였다. 낮은 심도에 굴착된 536 m 길이의 이 터널은 시 작부에는 토사층이며, 종점부 84 m 구간은 암반층이다. 주간 평균 순굴착속도는 토사층에서 400∼800 mm/hr 였는데 암반층에서 20∼110 mm/hr로 급격히 낮아졌다. 이러한 순굴착속도의 크기는 장비 및 암반의 특성을 고려한 이론적 속도와 비슷한 크기이다. 그리고, 순굴착속도는 추력이 증가할수록 비례하는 것으로 분석된다.