Influence of three-bench three-step excavation method on longitudinal deformation profiles in three-centered arch tunnels

To study subway turnouts’ adaptability to steep gradients, a finite element model of a metro No. 9 simple turnout was established. The main works include: (1) The train’s most unfavourable loading condition was modelled. (2) The turnout’s longitudinal displacement and stress were analysed with different gradients under the train braking load, temperature change load and a combination of the two, to determine the structure’s safety and stability under the most unfavourable working conditions. (3) The turnout structure’s cumulative longitudinal deformation under reciprocating load was studied. Both a fastener longitudinal resistance-displacement experiment under reciprocating load and a numerical simulation of No. 9 turnout modelled by the finite element modelling software, ANSYS, were carried out to study the gradient’s influence on the turnout’s longitudinal mechanical characteristics. (1) The turnout’s longitudinal displacement and stress increase linearly with an increase in gradient and temperature change, both of which are unfavourable to the turnout structure. As the gradient increases from 0‰ to 30‰, the longitudinal stress and displacement increase by more than 10%. (2) The turnout’s rail strength and displacement on a 30‰ slope under the most unfavourable load conditions are within the specification limitations. (3) Under reciprocating load, the fastener longitudinal stiffness decreases and the maximum and residual longitudinal displacement of the switch rail increase; an increased gradient intensifies these effects on the turnout.

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A mechanism of apparent inter-sonic propagation of shear fractures

10.5194/egusphere-egu21-5803 ◽

2021 ◽

Author(s):

Elena Pasternak ◽

Arcady Dyskin

Keyword(s):

Shear Zone ◽

Wave Velocity ◽

Shear Fracture ◽

Fracture Propagation ◽

P Wave ◽

Spherical Particles ◽

Fracture Mechanisms ◽

Longitudinal Deformation ◽

Plane Shear ◽

Limiting Case

Inter-sonic (faster than the shear wave velocity) propagation of zones of shear over faults are observed both in the Earth&#8217;s crust and in specially designed laboratory experiments. This is usually interpreted as propagation of shear fractures caused by postulated special fracture mechanisms. This interpretation is however at variance with experimental facts that shear fractures in solids do not propagate in their own planes, kinking instead. Extensive (and fast) in-plane shear fracture propagation seems to only be possible over pre-existing planes considerably weaker than the surrounding material. A limiting case of fracture propagation over such a weak plane is the propagation of a sliding zone resisted by friction only. Another limiting case is shearing over a narrow elastic layer (shear Winkler layer) without rupture. The shear Winkler layer models both traditional elastic connections (positive stiffness) and rotation of non-spherical particles of the fault gouge (negative stiffness), e.g. [1, 2].In both cases propagation of sliding/shear zone also involve longitudinal deformation in the surrounding material. Using a configuration different from [3, 4] we demonstrate that the presence of the longitudinal deformation makes the sliding/shear zone propagate with p-wave velocity. Propagation of such zones create seismic signals with power spectra resembling those observed in earthquakes.Acknowledgement. &#160; AVD and EP acknowledge support from the Australian Research Council through project DP190103260.

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Numerical analyses on mechanical performance of flat buried approach slab and soil deformation

10.2749/ghent.2021.1454 ◽

2021 ◽

Author(s):

Junqing Xue ◽

Dong Xu ◽

Yufeng Tang ◽

Bruno Briseghella ◽

Fuyun Huang ◽

...

Keyword(s):

Finite Element ◽

Tensile Stress ◽

Parametric Analysis ◽

Mechanical Performance ◽

Element Model ◽

Soil Deformation ◽

Longitudinal Deformation ◽

Expansion Joints ◽

Approach Slab ◽

Jointless Bridges

The vulnerability problem of expansion joints could be fundamentally resolved using the concept of jointless bridges. The longitudinal deformation of the superstructure can be transferred to the backfill by using the approach slab. The flat buried approach slab (FBAS) has been used in many jointless bridges in European countries. In order to understand the mechanical performance of FBAS and soil deformation, a finite element model (FEM) was implemented in PLAXIS. Considering the friction between the FBAS and soil, the buried depth, the FBAS length and thickness as parameters, a parametric analysis was carried out. According to the obtained results and in order to reduce the soil deformation above the FBAS, it is suggested to increase the friction between the FBAS and sandy soil, and the buried depth of FBAS. Moreover, it should be paid attention to the vertical soil deformation and the concrete tensile stress of FBAS in pulling condition.

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The research on longitudinal deformation features of shield tunnel when considering the variation of grout viscosity: A case study

Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art ◽

10.1201/9780429424441-262 ◽

2019 ◽

pp. 2473-2481

Author(s):

Y. Liang ◽

L.C. Huang ◽

J.J. Ma

Keyword(s):

Shield Tunnel ◽

Longitudinal Deformation ◽

Deformation Features

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Experimental Study of Selected Properties of Heavyweight Concrete Based on Analysis of Chemical Composition and Radioactive Elements of its Components

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.321.113 ◽

2021 ◽

Vol 321 ◽

pp. 113-118

Author(s):

Janette Dragomirová ◽

Martin T. Palou ◽

Katalin Gméling ◽

Veronika Szilágyi ◽

Ildikó Harsányi ◽

...

Keyword(s):

Bulk Density ◽

Nuclear Power ◽

Power Plants ◽

Concrete Strength ◽

Prompt Gamma ◽

Longitudinal Deformation ◽

Heavyweight Concrete ◽

Furnace Slag ◽

Selection Of

Heavyweight concrete is mostly used for its shielding properties in the nuclear power plants. These properties can already be influenced by the selection of the input materials. In the present study, concrete samples comprised of four-component binders based on CEM I 42.5 R, blast furnace slag, metakaolin and limestone and a mixture of barite and magnetite aggregate, were investigated. Based on Energy Dispersive X-ray Fluorescence, Neutron Activation, and Prompt-Gamma Activation analyses, three concrete designs were prepared and tested. Mechanical, physical (namely cubic compressive strength, bulk density, longitudinal deformation, and dynamic modulus of elasticity) and thermal properties (thermal conductivity coefficient, specific heat capacity, and thermal diffusivity), which should be influenced by the long-term exposure to irradiation were investigated. Presented results confirmed that the prepared samples are heavyweight concrete with bulk density higher than 3400 kg.m-3 with a low level of longitudinal deformation (between 0.265 ‰ and 0.352 ‰). All the prepared samples belong to the C 35/45 concrete strength class.

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An investigation of the deforming layer/debris-rich basal-ice continuum, illustrated from three Alaskan glaciers

Journal of Glaciology ◽

10.1017/s0022143000034936 ◽

1995 ◽

Vol 41 (139) ◽

pp. 619-633 ◽

Cited By ~ 29

Author(s):

Jane K. Hart

Keyword(s):

Simple Shear ◽

Vertical Deformation ◽

Longitudinal Deformation ◽

Geological Record ◽

Basal Ice ◽

Fabric Strength ◽

Matanuska Glacier ◽

Deformation Patterns ◽

Subglacial Environments

AbstractThree small Alaskan glaciers with different bed conditions were studied: Exit Glacier had a thin deforming layer and produced subglacial and proglacial glaciotectonic land forms; Childs Glacier also had a thin deforming layer but the upper part was frozen to the ice; Matanuska Glacier had no deforming layer but had subglacial debris-rich ice. Since it has been shown that sediment at the base can account for the majority of ice movement, it is suggested that there is a deforming bed/debris-rich continuum whereby similar processes occur throughout the different subglacial environments. These include: similar longitudinal deformation patterns (compression at the margin, extension and simple shear up-glacier); similar vertical deformation patterns, increase in deformation (and fabric strength) upwards through the sequence (leading to the attenuation of stratified ice into dispersed ice); and similar and interrelated incorporation processes. The major differences were that the processes occurred at a much faster rate within the deforming layer and that probably only the deforming layer will be recorded in the geological record.

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