• 터널과지하공간
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• 제4권2호
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• pp.144-155
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• 1994

This research is designed to assess current achievement levels for mechanized excavation systems in Korea adn suggest the model predictive of TBM performance using statistical approaches. A test section in the TBM construction sites is selected to measure and analyze TBM performance. The field records including operating data, time allocation into downtime catagories, and machine design are analyzed on a shift basis. There are a total of 240 shifts, with most days operating two shifts per day. Examples of the probability density functions produced from the test section are presented and discussed. Relationships between TBM penetration rate and rock physical properties are investigated and the empirical equations for TBM performance prediction are also assessed with the field data.

• 한국산업융합학회 논문집
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• 제22권6호
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• pp.599-606
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• 2019

In this study, it was aimed to find the optimal cutting conditions by measuring and analyzing the dimensional accuracy of SNCM 616 alloy steel, which is commonly used in industry, by precision hole machining using Ø25 mm and 8-blade reamer in CNC-HBM to be. As a result of the roundness and dimensional accuracy, it was found that the spindle speed had a significant effect on the dimensional tolerance value. Optimum cutting conditions are spindle speed 25 rpm and feed rate 20 mm / min.

• 한국산업융합학회 논문집
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• 제22권6호
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• pp.607-613
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• 2019

In this study, we investigate the effect of SNCM616 alloy steel, which is commonly used in industry, such as rotors and crank-shafts, on the surface roughness of CNC HBM with Ø25 mm, 8-blade reamer to objective is to analyze and present optimal cutting conditions. The higher the feedrate for the spindle speed, the rougher the surface roughness. The surface roughness was found to be better when the feed rate was lower. The resultant value of the most accurate surface roughness is Ra 0.756 ㎛, and the optimal cutting conditions are 25 rpm at spindle speed and 20 mm/min at transfer speed.

• Geomechanics and Engineering
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• 제29권3호
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• pp.249-258
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• 2022

A disc cutter is an excavation tool on a tunnel boring machine (TBM) cutterhead; it crushes and cuts rock mass while the machine excavates using the cutterhead's rotational movement. Disc cutter wear occurs naturally. Thus, along with the management of downtime and excavation efficiency, abrasioned disc cutters need to be replaced at the proper time; otherwise, the construction period could be delayed and the cost could increase. The most common prediction models for TBM performance and for the disc cutter lifetime have been proposed by the Colorado School of Mines and Norwegian University of Science and Technology. However, design parameters of existing models do not well correspond to the field values when a TBM encounters complex and difficult ground conditions in the field. Thus, this study proposes a series of machine learning models to predict the disc cutter lifetime of a shield TBM using the excavation (machine) data during operation which is response to the rock mass. This study utilizes five different machine learning techniques: four types of classification models (i.e., K-Nearest Neighbors (KNN), Support Vector Machine, Decision Tree, and Staking Ensemble Model) and one artificial neural network (ANN) model. The KNN model was found to be the best model among the four classification models, affording the highest recall of 81%. The ANN model also predicted the wear rate of disc cutters reasonably well.

• KEPCO Journal on Electric Power and Energy
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• 제6권3호
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• pp.305-313
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• 2020

전력송전을 위한 터널식 전력구는 점차 시공실적이 증가하고 있는 추세이며, 해저 및 대심도 등 시공환경이 어려운 구간의 건설도 증가하고 있다. 이에 소단면 쉴드TBM의 효율적 운영을 위해 굴진율 및 설계모델이 필요하다. 그러나, 제한된 지반조사 회수 및 굴착면 맵핑으로 인하여 암반특성과 굴진데이터를 정확히 매칭시켜 상호간 상관관계 및 굴진율 모델을 도출하는데 어려움이 있다. 이에 소단면 쉴드TBM에 적합한 굴진율 및 설계모델을 제시하기 위하여 커터헤드의 직경이 3.56 m인 실험용 EPB 쉴드TBM을 제작하고, 총 부피 87.5 ㎥인 인공암반 내에서 총 19번의 실대형 굴진실험을 수행하였다. 본 실험은 70MPa의 균질한 암반강도에서 수행되었기 때문에 운전변수인 추력과 커터헤드의 RPM에 따른 굴진율과 기계데이터간 상관관계를 효율적으로 분석할 수 있으며, 실제 굴착메커니즘과 동일하기 때문에 도출된 압입깊이와 토크값은 활용성이 높다. 본 연구를 통해 디스크커터 당 연직력과 압입깊이의 상관관계 및 연직력과 회전력의 상관관계를 도출하였다. 이러한 상관관계들을 이용하여 70 MPa급 암반에 대해 굴진율 예측과 TBM 설계가 가능할 것으로 판단한다. 또한, 인공암반의 RQD가 100%로 현장적용에 대한 한계점에 대해 FPI의 개념을 도입하여 굴진율 모델의 활용성을 증대시키고자 하였다.

• 한국터널지하공간학회 논문집
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• 제19권4호
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• pp.611-634
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• 2017

도시의 발전에 따라 전력선, 통신선, 상하수도배관 등을 공동으로 수용하는 공동구의 수요는 점점 증가할 것으로 예상되고 있으며 따라서 앞으로 TBM을 이용한 터널시공이 증가할 것으로 예상된다. TBM을 이용한 터널 건설시 굴진율 예측은 공기와 공사비 책정의 중요한 요소이다. 현재, NTNU model, CSM model 등의 TBM 굴진율 예측방법이 있지만, 이 방법들은 많은 입력 인자들을 필요로 한다. 본 논문은 문헌조사를 통해 다양한 여러 지반 물성인자들 중, 경암의 취성지수 (Brittleness index)와 TBM 순굴진율간의 관계를 도출하고자 하였다. 특히, 인장강도와 압축강도의 함수인 취성지수는 그 정의에 따라 순굴진율과 관계가 다르고 매우 큰 분산을 가지는 것으로 나타났다. 본 연구는 TBM 순굴진율 예측에서 암반물성 중 취성도가 지니는 의미를 제시하고 있다.

• Geomechanics and Engineering
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• 제37권3호
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• pp.223-241
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• 2024

Evaluating the performance of Tunnel Boring Machines (TBMs) stands as a pivotal juncture in the domain of hard rock mechanized tunneling, essential for achieving both a dependable construction timeline and utilization rate. In this investigation, three advanced artificial neural networks namely, gated recurrent unit (GRU), back propagation neural network (BPNN), and simple recurrent neural network (SRNN) were crafted to prognosticate TBM-rate of penetration (ROP). Drawing from a dataset comprising 1125 data points amassed during the construction of the Alborze Service Tunnel, the study commenced. Initially, five geomechanical parameters were scrutinized for their impact on TBM-ROP efficiency. Subsequent statistical analyses narrowed down the effective parameters to three, including uniaxial compressive strength (UCS), peak slope index (PSI), and Brazilian tensile strength (BTS). Among the methodologies employed, GRU emerged as the most robust model, demonstrating exceptional predictive prowess for TBM-ROP with staggering accuracy metrics on the testing subset (R² = 0.87, NRMSE = 6.76E-04, MAD = 2.85E-05). The proposed models present viable solutions for analogous ground and TBM tunneling scenarios, particularly beneficial in routes predominantly composed of volcanic and sedimentary rock formations. Leveraging forecasted parameters holds the promise of enhancing both machine efficiency and construction safety within TBM tunneling endeavors.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.203-210
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• 2004

Consolidation properties were analysed by means of depositional environments. Depositional environments including geochemical properties, porewater chemistry, sediment structures, particle size distributions and carbon age dating were analysed using undisturbed samples retrieved successively from a boring hole in the study area. Laboratory oedometer tests and anisotropic consolidated triaxial tests(CKoUC) were performed to examine the overconsolidation phenomenons. Based on the carbon age dating results and profiles of geochemical properties, porewater chemistry, salinity and pH, it was founded that the upper silt/clay complex layer was deposited under marine condition while sand and clay layers were deposited under fluvial condition. Planar laminated structures of silts and clays were dominant in marine deposits. Although there was no clear evidences that geological erosion had been occurred in marine deposits, overconsolidation ratio obtained from oedometer tests were greater than unity. Stress paths of samples behaved similar to those of normally consolidated clays. Data plotted in stress state charts proposed by Burland(1990) and Chandler(2000) showed that the marine deposits were geologically normally consolidated. These apparent overconsolidations can be explained by the fabric and chemical bonding due to the difference of the rate of deposition.

• Computers and Concrete
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• 제20권4호
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• pp.429-437
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• 2017

In this study, the effect of the tensile strength and ratio of disc spacing to penetration depth on the efficiency of tunnel boring machine (TBM) is investigated using Particle flow code (PFC) in two dimensions. Models with dimensions of $150{\times}70mm$ made of rocks with four different tensile strength values of 5 MPa, 10 MPa, 15 MPa and 20 MPa were separately analyzed and two "U" shape cutters with width of 10 mm were penetrated into the rock model by velocity rate of 0.1 mm/s. The spacing between cutters was also varied in this study. Failure patterns for 5 different penetration depths of 3 mm, 4 mm, 5 mm, 6 mm, and 7 mm were registered. Totally 100 indentation test were performed to study the optimal tool-rock interaction. An equation relating mechanical rock properties with geometric characteristics for the optimal TBM performance is proposed. The results of numerical simulations show that the effective rock-cutting condition corresponding to the minimum specific energy can be estimated by an optimized disc spacing to penetration depth, which, in fact, is found to be proportional to the rock's tensile strength.

• Geomechanics and Engineering
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• 제18권1호
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• pp.59-69
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• 2019

Grout injection is mainly used for permeability reduction and/or improvement of the ground by injecting grout material into pores, cracks, and joints in the ground. The oscillatory grout injection method was developed to enhance the grout penetration. In order to verify the level of enhancement of the grout, field grout injection tests, both static and oscillatory tests, were performed at three job sites. The enhancement in the permeability reduction and ground improvement effect was verified by performing a core boring, borehole image processing analysis, phenolphthalein test, scanning electron microscopy analysis, variable heat test, Lugeon test, standard penetration test, and an elastic wave test. The oscillatory grout injection increased the joint filling rate by 80% more and decreased the permeability coefficient by 33-68%, more compared to the static grout injection method. The constrained modulus of the jointed rock mass was increased by 50% more with oscillatory grout injection compared to the static grout injection, indicating that the oscillatory injection was more effective in enhancing the stiffness of the rock mass.