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Liners
Liner support in Phase2 is multi-purpose, and can be used to model a wide variety of geotechnical support types:
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Simple liners (e.g. a single layer of shotcrete)
Composite Liners (e.g. liners consisting of multiple layers of material)
Pile walls (e.g. a structural beam element with a joint on both sides)
Geosynthetic support such as geogrids and geotextiles
Reinforced concrete
Cable Truss
Struts
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Liners may consist of beam elements which can resist axial, bending and shear forces, or truss elements which only possess axial properties. In all cases, the basic support properties of the liner are entered in the Define Liner Properties dialog.
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Liners: Single layer
The most basic liner consists of a single layer of material, which is fully bonded to the rock or soil (i.e. no interface slip is considered). In the following figure a single layer shotcrete liner has been applied to the boundary of a tunnel. The liner elements are displayed as thick coloured line segments on the boundary. Each liner (beam) element corresponds to the edge of a single finite element.
Liner applied to tunnel boundary
Liners are applied with the Add Liner option. Simply select the desired boundary segments with the mouse, and the liner elements will be applied to the boundary.
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Liners: Composite Liners
A Composite Liner in Phase2, is a liner which may consist of multiple layers of material (up to 4 layers). The different layers of a Composite Liner may have different material properties, and may be applied at different stages. A Composite Liner may also include a single joint between any two layers.
The support properties of each layer of a Composite Liner are defined using the Define Liners option. The overall properties of a Composite Liner (i.e. joint/liner/liner ... combination, and staging sequence) are defined with the Define Composite option.
Define Composite Properties dialog
Composite liners are added to a model in the same way as single layer liners, with the Add Liner option. In the Phase2 Interpret program, the individual layers of a composite liner can be expanded and displayed as shown in the following figure. Individual layers can be selected with the Select Support Layer option, and analysis results can be plotted and displayed for each layer.
Composite liner with two layers (blue and purple beam elements)
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Liners: Geosynthetics
Geosynthetics (e.g. geogrids or geotextiles) can be modeled as a simple liner, as shown in the figure below.
Geogrid reinforced embankment, geogrid modeled as a simple liner (no slip)
If you wish to consider the interface (slip) properties on both sides of the geosynthetic, you can model the geosynthetic as a Structural Interface. This option allows you to model a liner with a joint on both sides. See the Structural Interface page for more information.
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Liners: Pile Walls
Pile walls can be modeled as a single layer liner, as shown in the figure below.
Pile walls supporting trench
If you wish to consider the interface (slip) properties on both sides of the pile, then you can model the pile wall as a Structural Interface. This option allows you to model a liner with a joint on both sides. See the Structural Interface page for more information.
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Liners: Struts
Liners in Phase2 can represent many different types of support and installation sequencing. There are situations when you would want to define a support element which crosses an excavated space. This allows you to model support such as struts, for example, or a free-standing liner which is back-filled at a later stage.
Struts installed to support trench walls
In order to model struts using Liners, it is important to note that you must turn OFF the Automatic Liner Removal option in the Support menu. This allows you to excavate the material on both sides of the liner, and the liner will remain in place (i.e. it will not be automatically removed).
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Liners: Properties
Liner properties (e.g. strength, stiffness, thickness etc) are defined in the Liner Properties dialog. For modeling purposes, there are four different liner types defined in Phase2:
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Standard Beam
Reinforced Concrete
Geosynthetic
Cable Truss
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If Liner Type = Standard Beam or Reinforced Concrete, each liner element is a beam element which can resist bending moment, axial and shear forces. You may choose from Timoshenko or Bernoulli beam formulations.
If Liner Type = Geosynthetic or Cable Truss, only the tensile properties of the liner are considered.
Liner Properties (Liner Type = Standard Beam)
Liner Properties (Liner Type = Reinforced Concrete)
Liner Properties (Liner Type = Geosynthetic))
Liner Properties (Liner Type = Cable Truss)
Liners can behave elastically or plastically (i.e. yielding) with liners having both peak and residual (i.e. post-peak) capacities. Liner properties can be staged to model the effects of hardening over time or the addition of more support.
Staged Concrete Properties
For more information see the Define Liner Properties topic in the Phase2 Help system.
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Liners: Staging
For multi-stage models, the liner installation sequence can be specified with the Assign Properties dialog. Liner staging can also be specified when liners are initially added, or with the right-click menu after they are added. A removal stage can also be specified.
Staged installation of composite liner in power cavern
Liner material properties can also be staged, see previous section.
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Liners: Analysis Results
After the Phase2 analysis has been computed, you can examine the forces and moments in the liners, which allows you to optimize the required support system. The liner data can be:
The Show Values option allows you to display liner results directly on the model, in the form of a histogram or line graph, superimposed directly on the liners. Axial force, bending moment and shear force can be plotted. The numerical values can be displayed, and the display can be customized.
In the following figure, the liner axial force is plotted with Show Values, and liner yielding is displayed (red elements) with the Show Yield option.
Liner axial force (histogram) and yielding (red elements)
If liners have a non-zero residual strength, then failed liner elements can still carry load after yielding. As you can see in the above figure, several liner elements have yielded (red) but still carry an axial load.
Liner bending moment (histogram) and yielding (red elements)
Liner data (axial force, bending moment, shear force) can be graphed with the Graph Liner Data option.
Axial force in liner (graphed in Phase2)
Liner results can be exported to Microsoft Excel with a single mouse click, and automatically graphed in Excel.
Axial force in liner, exported to Excel with one mouse-click
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