• Title/Summary/Keyword: collapse surface

Search Result 273, Processing Time 0.022 seconds

Investigation into Deformation of Three-Dimensional Microstructures via Surface Tension of a Rinsing Material During a Developing Process (현상공정에서 표면장력에 의한 극미세 3 차원 구조물의 변형거동 분석 및 저감방안에 관한 연구)

  • Park, Sang-Hu;Yang, Dong-Yol
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.32 no.4
    • /
    • pp.303-309
    • /
    • 2008
  • Dense and fine polymer patterns often collapse, as they come into contact with each other at their protruding tips. Resist pattern collapse depends on the aspect ratio of patterns and the surface tension of rinsing materials. The pattern collapse is a very serious problem in microfabrication, because it is one of the factors which limit the device dimensions. The reasons for the pattern collapse are known as the surface tension of rinse liquid, centrifugal force and rinse liquid flow produced in the developing process. In this work, we tried to evaluate the pattern collapse of three-dimensional microstructures that were fabricated by two-photon induced photopolymerization, and showed the way how to reduce the deformation of microstructures.

Collapse analysis of shallow tunnel subjected to seepage in layered soils considering joined effects of settlement and dilation

  • Yang, X.L.;Zhang, R.
    • Geomechanics and Engineering
    • /
    • v.13 no.2
    • /
    • pp.217-235
    • /
    • 2017
  • The stability prediction of shallow buried tunnels is one of the most difficult tasks in civil engineering. The aim of this work is to predict the state of collapse in shallow tunnel in layered soils by employing non-associated flow rule and nonlinear failure criterion within the framework of upper bound theorem. Particular emphasis is first given to consider the effects of dilation on the collapse mechanism of shallow tunnel. Furthermore, the seepage forces and surface settlement are considered to analyze the influence of different dilation coefficients on the collapse shape. Two different curve functions which describe two different soil layers are obtained by virtual work equations under the variational principle. The distinct characteristics of falling blocks up and down the water level are discussed in the present work. According to the numerical results, the potential collapse range decreases with the increase of the dilation coefficient. In layered soils, both of the single layer's dilation coefficient and two layers' dilation coefficients increase, the range of the potential collapse block reduces.

The Analysis of Collapse Load of Thick Pressure Cylinder under External Hydrostatic Pressure (외압을 받는 두꺼운 원통형 내압용기의 붕괴하중 해석)

  • Lee, Jae-Hwan;Park, Byoungjae
    • Journal of the Society of Naval Architects of Korea
    • /
    • v.56 no.2
    • /
    • pp.175-186
    • /
    • 2019
  • Number of studies on the buckling of thin cylindrical pressure vessels, such as submarine pressure hull and pipe with a large ratio of diameter/thickness, have been carried out in the naval and ocean engineering. However, research about thick cylinder pressure vessel has not been active except for the specific application in nuclear area. There are not many papers for the estimation of buckling and ultimate load capacity of thick cylinders for the deep sea usage. Thus, it is important to understand the theoretical bases of the buckling and collapse process and the derivation process of such loads for the proper design and structural analysis. The objective of this study is to survey the collapse behavior, to analyse and clarify the derivation procedure and to estimate the ultimate collapse load for thick cylinder by analyzing relevant books and papers. It is found that the yielding begins at the internal surface of the thick cylinder and plasticity develops from the internal surface to the external surface to generate collapse. Also the initial imperfection of cylinder develops flattening and consequently accelerates buckling and finally ultimate collapse. By comparing the collapse loads of aluminum thick cylinder by applying equations herein, it is shown that the equations analyzed are appropriate to obtain collapse load for thick cylinder.

Roof failure of shallow tunnel based on simplified stochastic medium theory

  • Huang, Xiaolin;Zhou, Zhigang;Yang, X.L.
    • Geomechanics and Engineering
    • /
    • v.14 no.6
    • /
    • pp.571-580
    • /
    • 2018
  • The failure mechanism of tunnel roof is investigated with upper bound theorem of limit analysis. The stochastic settlement and nonlinear failure criterion are considered in the present analysis. For the collapse of tunnel roof, the surface settlement is estimated by the simplified stochastic medium theory. The failure curve expressions of collapse blocks in homogeneous and in layered soils are derived, and the effects of material parameters on the potential range of failure mechanisms are discussed. The results show that the material parameters of initial cohesion, nonlinear coefficient and unit weight have significant influences on the potential range of collapse block in homogeneous media. The proportion of collapse block increases as the initial cohesion increases, while decreases as the nonlinear coefficient and the unit weight increase. The ground surface settlement increases with the tunnel radius increasing, while the possible collapse proportion decreases with increase of the tunnel radius. In layered stratum, the study is investigated to analyze the effects of material parameters of different layered media on the proportion of possible collapse block.

A Case Study on Collapse Characteristics of Slope during Construction in the Chung-Cheong Area (시공 중 비탈면의 붕괴 특성에 대한 충청지역 사례연구)

  • Lee, Jundae;Bae, Wooseok
    • Journal of the Korean GEO-environmental Society
    • /
    • v.16 no.10
    • /
    • pp.23-32
    • /
    • 2015
  • Most studies on slope collapsed have focused on collapse cases that occur on stabilized slopes in public use. Few studies have been conducted on the collapse characteristics of slopes that occur during construction before stabilization of the slope. In this study, detailed investigation was conducted for 79 sites where slope collapse occurred during or immediately after construction in the Chungcheong region, and their geometrical characteristics, collapse characteristics, design and reinforcement methods were evaluated. As a result of this analysis, it was found that the Chungbuk (CB) area was marked by plane-type collapse and surface layer collapse whereas the Chungnam (CN) area was marked by surface layer collapse or loss of sedimentary rocks. Furthermore, the major collapse factors of the Chungbuk region were joint alternations (53%) and weathering (25%), and the blocking due to multidirectional joints and foliation was also an influencing factor. In the phyllite area, too, the development of joints (55%) was a major factor, but the geological characteristics (36%) of sedimentary rocks such as faults and coaly shale also had considerable effects. Therefore, the geological, climatic, and environment characteristics were found to have affected the stability of slopes.

The Ground Reinforcement on Daylight Collapsed Block of Crown Head in the Face of the Tunnel of Highway (고속도로 터널막장 천단부의 붕락구간에 대한 지반보강)

  • 천병식;정덕교;한기식;정진교
    • Proceedings of the Korean Geotechical Society Conference
    • /
    • 1999.03a
    • /
    • pp.323-330
    • /
    • 1999
  • Daylight collapse have been occurred by about 5.0m deep at ground surface and collapse of the crown head part of the tunnel have connected to the ground surface during first step of shotcrete work after blasting of upper half section of the tunnel driving at two-way double track tunnel face section on highway construction. This study is for a successful illustration case for the earth improvement method through applying such strengthening methods as cement milk grouting, S.G.R grouting,, steel pipe reinforced multi-step grouting etc. for the purpose of earth strengthening of loosened earth block occurred by tunnel collapse.

  • PDF

Surface Subsidence according to Progressive Collapse of Circular opening (원형공동의 점진적인 붕락에 따른 지표침하특성)

  • 지정배;김종우
    • Tunnel and Underground Space
    • /
    • v.10 no.1
    • /
    • pp.33-44
    • /
    • 2000
  • In order to investigate the effect of progressive collapse of underground circular opening on surface subsidence, laboratory model tests were performed. The modelling materials were sand which has been used as KS standard. Six test models which had respectively different depths of openings were produced. Surface subsidence and horizontal displacements were measured according to progressive collapse of underground opening. Some subsidence prediction method such as NCB method, profile function method and influence function method were considered to predict the subsidence of sand models. The profile function method approximated by Gaussian error function was finally suggested as the most appropriate to sand models.

  • PDF

Homogenized limit analysis of masonry structures with random input properties: polynomial Response Surface approximation and Monte Carlo simulations

  • Milani, G.;Benasciutti, D.
    • Structural Engineering and Mechanics
    • /
    • v.34 no.4
    • /
    • pp.417-447
    • /
    • 2010
  • The uncertainty often observed in experimental strengths of masonry constituents makes critical the selection of the appropriate inputs in finite element analysis of complex masonry buildings, as well as requires modelling the building ultimate load as a random variable. On the other hand, the utilization of expensive Monte Carlo simulations to estimate collapse load probability distributions may become computationally impractical when a single analysis of a complex building requires hours of computer calculations. To reduce the computational cost of Monte Carlo simulations, direct computer calculations can be replaced with inexpensive Response Surface (RS) models. This work investigates the use of RS models in Monte Carlo analysis of complex masonry buildings with random input parameters. The accuracy of the estimated RS models, as well as the good estimations of the collapse load cumulative distributions obtained via polynomial RS models, show how the proposed approach could be a useful tool in problems of technical interest.

Bund Collapse in Sloping Paddy Area by a Heavy Rainfall -Case Study for Dongrim-ri in Chungbuk Province- (집중호우에 의한 경사지논의 논둑붕괴 -충북 청원군 옥산면 동림리의 사례-)

  • 김진수
    • Magazine of the Korean Society of Agricultural Engineers
    • /
    • v.38 no.5
    • /
    • pp.55-63
    • /
    • 1996
  • The situation and cause of bund collapse in steep sloping paddy area by a heavy rainfall of Chungbuk Province were investigated by field surveys. Shapes of paddy plots are irregular and average size of them is 12.6a. Surface, groundwater and plot-to-plot irrigations are being carried out in the study plots. The type of bund collapse can be divided as follows: overflow type and inundation type. The overflow type generally occurs at the bund with slope lacking the design standard. The inundation type damages paddy plots more seriously than the overflow type. It induces continuous bund collapse from a inflow-plot to a outflow-plot and includes lots of type (inside paddy) collapse, which results in much subsoil erosion. The installation of mountain stream weir and maintenance of mountain stream are proposed to prevent the inundation type collapse.

  • PDF

Collapse mechanism for deep tunnel subjected to seepage force in layered soils

  • Yang, X.L.;Yan, R.M.
    • Geomechanics and Engineering
    • /
    • v.8 no.5
    • /
    • pp.741-756
    • /
    • 2015
  • The prediction of impending collapse of deep tunnel is one of the most difficult problems. Collapse mechanism of deep tunnel in layered soils is derived using a new curved failure mechanism within the framework of upper bound theorem, and effects of seepage forces are considered. Nonlinear failure criterion is adopted in the present analysis, and the possible collapse shape of deep tunnel in the layered soils is discussed in this paper. In the layered soils, the internal energy dissipations along velocity discontinuity are calculated, and the external work rates are produced by weight, seepage forces and supporting pressure. With upper bound theorem of limit analysis, two different curve functions are proposed for the two different soil stratums. The specific shape of collapse surface is discussed, using the proposed curve functions. Effects of nonlinear coefficient, initial cohesion, pore water pressure and unit weight on potential collapse are analyzed. According to the numerical results, with the nonlinear coefficient increase, the shape of collapse block will increase. With initial cohesion of the upper soil increase, the shape of failure block will be flat, and with the lower soil improving, the size of collapsing will be large. Furthermore, the shape of collapsing will decrease with the unit weight decrease.