• Geomechanics and Engineering
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• 제30권1호
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• pp.11-26
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• 2022

One of the most important issues in tunneling, is the squeezing phenomenon. Squeezing can occur during excavation or after the construction of tunnels, which in both cases could lead to significant damages. Therefore, it is important to predict the squeezing and consider it in the early design stage of tunnel construction. Different empirical, semi-empirical and theoretical-analytical methods have been presented to determine the squeezing. Therefore, it is necessary to examine the ability of each of these methods and identify the best method among them. In this study, squeezing in a part of the Alborz service tunnel in Iran was estimated through a number of empirical, semi- empirical and theoretical-analytical methods. Among these methods, the most robust model was used to obtain a database including 300 data for training and 33 data for testing in order to develop a machine learning (ML) method. To this end, three ML models of Gaussian process regression (GPR), artificial neural network (ANN) and support vector regression (SVR) were trained and tested to propose a robust model to predict the squeezing phenomenon. A comparative analysis between the conventional and the ML methods utilized in this study showed that, the GPR model is the most robust model in the prediction of squeezing phenomenon. The sensitivity analysis of the input parameters using the mutual information test (MIT) method showed that, the most sensitive parameter on the squeezing phenomenon is the tangential strain (ε_θ^α) parameter with a sensitivity score of 2.18. Finally, the GPR model was recommended to predict the squeezing phenomenon in tunneling projects. This work's significance is that it can provide a good estimation of the squeezing phenomenon in tunneling projects, based on which geotechnical engineers can take the necessary actions to deal with it in the pre-construction designs.

• 한국치위생학회지
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• 제10권4호
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• pp.577-584
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• 2010

Objectives : The purpose of this study was to examine the relationship of toothpaste-squeezing methods to the amount of toothpaste used among adults. Methods : The subjects in this study were 227 freshmen in a local college. After the intent of a survey was explained by this researcher, how much dentifrice they used was checked to ensure statistical objectivity, and then a survey was conducted. The collected data were analyzed with a SPSS WIN 13.0 program. Results : The findings of the study were as follows:1. As for connections between the way of squeezing and the amount used, the usual amount used, the amount used by horizontal squeezing and the amount used by pea-sized squeezing were respectively 1.12g, 0.66g and 0.46g. The amount used by horizontal squeezing and pea-sized squeezing was less than the usual amount used by 0.46g(41%) and 0.66g(59%) respectively.2. Gender, residential area, educational experiences and daily mean toothbrushing frequency made no differences to the amount of toothpaste used.3. The students who normally used a larger amount of toothpaste used a greater amount of toothpaste as well when they utilized horizontal squeezing and pea-sized squeezing, and the larger amount used by horizontal squeezing led to the greater amount used by pea-sized squeezing. Conclusions : As there were large disparities in the amount of toothpaste used according to the squeezing methods, systematic research efforts should be directed into setting the standard for the recommended amount of toothpaste used for adults and into squeezing method so that they could brush their teeth in an effective manner by using the minimum amount of toothpaste.

• Geomechanics and Engineering
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• 제18권2호
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• pp.215-224
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• 2019

Excavation of long tunnels by shielded TBMs is a safe, fast, and efficient method of tunneling that mitigates many risks related to ground conditions. However, long-distance tunneling in great depth through adverse geological conditions brings about limitations in the application of TBMs. Among various harsh geological conditions, squeezing ground as a consequence of tunnel wall and face convergence could lead to cluttered blocking, shield jamming and in some cases failure in the support system. These issues or a combination of them could seriously hinder the performance of TBMs. The technique of excavation has a strong influence on the tunnel response when it is excavated under squeezing conditions. The Golab water conveyance tunnel was excavated by a double-shield TBM. This tunnel passes mainly through metamorphic weak rocks with up to 650 m overburden. These metamorphic rocks (Shales, Slates, Phyllites and Schists) together with some fault zones are incapable of sustaining high tangential stresses. Prediction of the convergence, estimation of the creeping effects and presenting strategies to overcome the squeezing ground are regarded as challenging tasks for the tunneling engineer. In this paper, the squeezing potential of the rock mass is investigated in specific regions by dint of numerical and analytical methods. Subsequently, several operational solutions which were conducted to counteract the challenges are explained in detail.

• 치위생과학회지
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• 제10권6호
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• pp.439-443
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• 2010

본 연구는 과량의 불소세치제 사용을 예방하기 위하여 만3~6세 아동의 불소세치제 사용량을 비교 평가하고자 충남 홍성군에 위치한 어린이집 5곳의 84명을 대상으로 칫솔두부크기와 세치제 짜는 방법에 따른 세치제량을 비교하였고, 실제적으로 어린이를 대상으로 구강보건교육을 시행하고 있는 구강보건교육자인 치위생과 학생 141명을 대상으로 콩알크기(pea-size)로 짜는 방법과, 소량의 세치제를 묻히는(smear) 방법으로 짠 세치제 양을 비교하여 다음과 같은 결과를 얻었다. 1. 어린이용 칫솔에 짠 불소세치제의 양은 0.29 g이었고, 성인용 칫솔에 짠 불소세치제의 양 은 0.34 g으로 유의한 차이가 나타나 작은 크기의 칫솔로 짰을 때 더 적은양의 세치제를 사용하는 것으로 조사되었다(p<0.05). 2. 3-6세 아동이 평소 통상적으로 짜는 방법대로 짠 양이 0.31 g이었고, 콩알크기(pea-size)로 짠 양이 0.21 g이었으며, 소량의 세치제를 묻히는(smear) 방법을 이용하여 짠 양은 0.26 g으로 조사되어, 평소 통상적으로 짜는 방법보다 콩알크기(pea-size)로 짜는 방법이나 소량의 세치제를 묻히는(smear) 방법을 이용하면 더 적은양의 불소세치제를 사용할 수 있는 것으로 조사되었다(p<0.05). 3. 치위생과 학생들을 조사한 결과 콩알크기(pea-size)로 짰을 때의 양은 0.23 g이었고, smear 방법을 이용했을 때는 0.15 g으로 조사되어, 소량의 세치제를 묻히는(smear) 방법을 이용했을 때 더 적은 양의 불소세치제를 사용하는 것으로 조사되었다(p<0.05). 4. 아동과 치위생과 학생들의 세치제 짜는 방법에 따라 차이가 있는지 조사한 결과 콩알크기(pea-size)로 짰을 때는 두 집단 간의 차이가 없었으나(p>0.05), 소량의 세치제를 묻히는(smear)방법으로 짰을 때는 치위생과 학생들이 더 적은양의 불소세치제를 사용하는 것으로 조사되었다(p<0.05) 5. 두부가 작은 칫솔을 사용하면 불소세치제 사용량을 감소시킬 수 있으며, 콩알크기(pea-size)로 짜는 방법과 소량의 세치제를 묻히는(smear) 방법은 불소세치제 사용량의 감소로 부주의한 불소 섭취를 최소화할 수 있어 어린이에게 추천할 수 있다.

• 대한조선학회 특별논문집
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• 대한조선학회 2005년도 특별논문집
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• pp.144-150
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• 2005

The size of ship is being larger than the past in the shipping industry thanks to the increased quantity of goods transported by ship. Therefore, HHIC (Hanjin Heavy industries & Construction co., LTD) invented innovative construction method, so called 'DAM', to build a ship which is longer than the length of the HHIC's dry dock. On Erection at the sea by the application of DAM Method, Squeezing & Detachment of A/F film may occur as a result of the wave and the constriction between A/F film pre-applied on the side shell and DAM's Rubber Packing. Thus, the test for finding the minimum curing time of A/F film was performed to protect Squeezing & Detachment of A/F film on the hull. To verify the soundness of paint and to find the optimum condition during the erection period of the DAM, laboratory test was carried out under no immersion condition through the application of various coatings on the Rubber Packing. And two methods were selected from the results of laboratory test for actual MOCK-UP Test. In addition, the test for the film profile per temperature of silicone A/F coat and the film Squeezing was performed.

• Geomechanics and Engineering
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• 제22권6호
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• pp.509-518
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• 2020

Multi-layered primary linings have been proved to be highly effective for tunneling in severe squeezing grounds. But there still has not existed well-established design method for it. Basically, there are two main critical problems in this method, including determinations of allowable deformation and distribution of support stiffness. In order to address such problems, an attempt to investigate the mechanical response of a circular tunnel with double primary linings is performed in this paper. Analytical solutions in closed form for stresses and displacements around tunnels are derived. In addition, the effectiveness and reliability of theoretical formulas provided are well validated by using the numerical method. Finally, based on the analytical solutions, a parametric investigation on the effects of allowable deformation and distribution of support stiffness on tunnel performance is conducted. Results show that the rock pressure and displacement are significantly affected by these two design parameters. It can be found that rock pressure decreases as either allowable deformation increases or stiffness of the first primary lining decreases, but rock displacement shows an opposite trend. This paper can provide a useful guidance for the design of multi-layered primary linings.

• 한국터널지하공간학회 논문집
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• 제18권6호
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• pp.557-568
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• 2016

심부 터널을 굴착하는 동안 발생할 수 있는 현상인 압출은 큰 소성 변형과 터널 축소 그리고 지보 붕괴를 일으킬 수 있다. 따라서 압출 현상의 발생 가능성과 변형량, 응력 변화의 정량적 예측은 합리적인 시공 방안을 수립하기 위하여 매우 중요하다. 본 연구는 변형률 연화 구성모델을 이용한 3차원 수치해석을 수행하여 압출 거동을 합리적으로 모사하고 변형량과 소성 범위 등을 정량적으로 예측하고자 하였다. 다양한 범위의 응력 조건과 강도 조건의 42가지 경우에 대한 해석을 수행한 결과 최대접선응력과 암반강도비가 소성 변형량과 소성 깊이를 합리적으로 예측할 수 있었으며 이들의 관계식을 제안하였다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.123-124
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• 2002

A press shoe is an element of a machine for squeezing water from wood pulp in the field of manufacturing paper. This is used to compress the pulp enveloped by felt sheet with a large roller. The squeezing force is made by hydraulic pressure. The press shoe has a mechanism similar to a partial hydrostatic bearing. The pressure profile between press shoe and roller affects their squeezing ability, and partial peak pressure can tear the wet pulp. The curvature of the surface of press shoe varies to reduce the peak pressure and increase the mean pressure simultaneously. Therefore, the prediction of pressure distribution considering partially changed curvature of hydrostatic bearing is very important for designing the press shoe. In this study, the difference formulation of Reynolds' equation for partial hydrostatic bearing is by direct numerical method and a computer program to calculate the pressure distribution is developed. We investigate the effect of partially changed curvature of bearing surface on the pressure distribution. Other design parameter for hydrostatic bearing such as depth of pocket and relative velocity are also studied.

• KSTLE International Journal
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• 제3권2호
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• pp.90-94
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• 2002

A press shoe is an element of a machine for squeezing water from wood pulp in the field of manufacturing paper. This is used to compress the pulp enveloped by felt sheet with a large roller. The squeezing farce is made by hydraulic pressure. The press shoe has a mechanism similar to a partial hydrostatic bearing. The pressure profile between press shoe and roller affects their squeezing ability, and partial peak pressure can tear the wet pulp. The curvature of the surface of press shoe varies to reduce the peak pressure and increase the mean pressure simultaneously, Therefore, the prediction of pressure distribution considering partially changed curvature of hydrostatic bearing is very important far designing the press shoe. In this study, the difference formulation of Reynolds equation far partial hydrostatic bearing is derived by direct numerical method and a computer program to calculate the pressure distribution is developed. We investigate the effect of partially changed curvature of bearing surface on the pressure distribution. Other design parameter far hydrostatic bearing such as depth of pocket and relative velocity are also studied.

• 한국음향학회지
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• 제29권2호
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• pp.91-96
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• 2010

본 연구에서는 식물의 씨로부터 착유하는 기존의 착유방법에 있어서 착유 효율의 한계를 개선하기 위하여 초음파를 이용한 부가 에너지의 적용 가능성을 실험적으로 확인 하였다.그 결과, 기존의 압착방식에 의한 착유 방식에 란주반형 트랜스듀서로부터 방사되는 초음파 진동에 의한 압력을 부가함으로써 기존의 단순압착 방식의 착유효율이 15 %인 경우 25 %로 증가하여 적지 않은 효율의 증가를 보였다. 초음파에 의한 부가 압력을 해석하기 위하여 착유시료의 음향임피던스 및 초음파 트랜스듀서의 전통속도를 측정하여 방사되는초음파의 음압진폭을 구한 결과 단순압착 정압의 약 2.8 %에 불과했으나 초음파 주기에 따른 양력의 변회는 착유효율증가에 매우 효율적임을 확인할 수 있었다.