Tutorial_02_Scaling_Wedges

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<p>Tutorial 2 | Scaling Wedges</p><p>Topics Covered:</p><p>• Scaling by using Persistence</p><p>and Trace Length</p><p>• Scaling Tunnel Length</p><p>• Scaling Wedge Size</p><p>• Scaling All Wedges</p><p>• Scaling Individual Wedges</p><p>• Safety factor and Scaling</p><p>Unwedge v. 4.0</p><p>Unwedge v. 4.0 Tutorial Manual Tutorial 2: Scaling Wedges</p><p>2 - 2</p><p>Unwedge always initially calculates the maximum sized wedges which can form around an</p><p>excavation.</p><p>This tutorial demonstrates how to scale down the size of the wedges, to represent the actual</p><p>size of wedges observed in the field. We will demonstrate two methods of wedge scaling in</p><p>this tutorial.</p><p>Wedge scaling is important because the assumed wedge size can have a significant effect</p><p>on support requirements (e.g. pattern spacing, positioning or orientation of bolts, and the</p><p>thickness or strength of shotcrete).</p><p>The model represents a section of an underground spiral access ramp.</p><p>For this tutorial we will start by reading in the file Tutorial 02 Scaling Wedges.weg which</p><p>you should find in the Unwedge 4.0 Examples > Tutorials folder in your Unwedge installation</p><p>folder.</p><p>Select: File > Recent Folders > Tutorials Folder, or use the drop-down arrow on the Open</p><p>toolbar button to choose the tutorials folder.</p><p>Select the Tutorial 02 Scaling Wedges.weg file.</p><p>The model should appear as follows.</p><p>As you can see, all of the Perimeter Wedges (roof, sides and floor wedges) are the maximum</p><p>possible size for the excavation cross-section.</p><p>NOTE: the Plunge of the Tunnel Axis Orientation is 15 degrees, because the model represents</p><p>a section of an inclined ramp, rather than a horizontal tunnel.</p><p>The Model</p><p>Introduction</p><p>Unwedge v. 4.0 Tutorial Manual Tutorial 2: Scaling Wedges</p><p>2 - 3</p><p>We will first scale the wedges using the options in the Input Data dialog.</p><p>Open the Input Data dialog by clicking on the button on the toolbar or through the Analysis</p><p>menu. Click on the General tab. We should note here that the length of the tunnel itself can</p><p>be scaled down in this tab. Let’s assume the length of the tunnel is 10 m. Therefore, check</p><p>off the “Tunnel Length” box and enter a length of 10 m, as shown. Click Apply to see the</p><p>changes. The length of the tunnel should now be 10 m.</p><p>Joint Structure Continuity : Persistence and Trace Length</p><p>We will now scale the wedges themselves using persistence and trace length.</p><p>Select the Joint Properties tab. In the Joint Properties 1 tab, under Joint Structure, change</p><p>the Continuity from Infinite to Persistence. We will use the default 5 m persistence. Select</p><p>OK.</p><p>All wedges should now have been scaled, as shown below.</p><p>Scaling Wedges: Input Data Dialog</p><p>Unwedge v. 4.0 Tutorial Manual Tutorial 2: Scaling Wedges</p><p>2 - 4</p><p>Click on the Filter List button on the sidebar. Select the Defaults button to ensure the default</p><p>data is displayed. Then check off “Scaled By” as well as “Joint Persistence.” Select OK.</p><p>Unwedge v. 4.0 Tutorial Manual Tutorial 2: Scaling Wedges</p><p>2 - 5</p><p>We can see in the sidebar that all wedges have been scaled by Joint 1, as defined in the</p><p>Input Data dialog. The Joint Persistence for Joint 1 of each wedge is 5 m, as expected.</p><p>We will now scale the wedges using the Joint 2 Trace Length.</p><p>Open the Input Data dialog by clicking on the button on the toolbar or through the Analysis</p><p>menu. Select the Joint Properties tab. Click on Joint Properties 3 on the left of the dialog.</p><p>Change the Joint Structure Continuity from Infinite to Trace Length and enter a trace length</p><p>of 3 m as shown. Select OK.</p><p>Unwedge v. 4.0 Tutorial Manual Tutorial 2: Scaling Wedges</p><p>2 - 6</p><p>Now click on the Filter List button again and check off “Joint Trace Lengths” as well. Select</p><p>OK.</p><p>On the sidebar, you should now see that all four wedges have been scaled by the Joint 3</p><p>trace length of 3 m. Because the trace length we entered for Joint 3 resulted in smaller</p><p>wedges than the Persistence we entered for Joint 1, Unwedge has scaled all wedges by the</p><p>Joint 3 trace length.</p><p>Unwedge v. 4.0 Tutorial Manual Tutorial 2: Scaling Wedges</p><p>2 - 7</p><p>The Scale Wedges option from the Analysis menu provides a more advanced way of scaling</p><p>wedges</p><p>Select: Analysis > Scale Wedges</p><p>You will see the Scale Wedges dialog.</p><p>In this dialog, wedge size can be scaled according to joint trace length, joint persistence or</p><p>wedge data (e.g. volume, face area etc). Although we can enter multiple scaling parameters</p><p>at the same time, let’s enter parameters one at a time, to see the results at each step.</p><p>Select the Joint 1 (Trace Length) checkbox, and enter a Scaling Value of 4 meters. Select OK.</p><p>Scaling Wedges: Advanced</p><p>Unwedge v. 4.0 Tutorial Manual Tutorial 2: Scaling Wedges</p><p>2 - 8</p><p>You will notice that all of the Joint 1 trace lengths displayed in the sidebar have stayed</p><p>the same. This is because we have already scaled Joint 1 with a trace length of 3 m, and</p><p>Unwedge will choose the smallest wedge size when several different scaling values are</p><p>imputed. This demonstrates that the Scale Wedges dialog works in conjunction with the</p><p>scaling options in the Input Data dialog.</p><p>To indicate that scaling has been applied to a wedge, the letter “s” is displayed beside the</p><p>wedge number (e.g. the roof wedge is numbered “8s”). If you do not see the wedge numbers,</p><p>go to Display Options, select the Wedge Views tab, and make sure the Wedge Numbers</p><p>checkbox is selected.</p><p>At this point, we should note the following:</p><p>• When we use the All Wedges scaling option (in the Scale Wedges dialog), this does not</p><p>necessarily mean that all wedges will be scaled (i.e. reduced in size). It means that all</p><p>wedges will be CONSIDERED for scaling. Wedges will only be scaled if their current</p><p>dimensions are larger than one of the scaling parameters. If the parameters of a wedge</p><p>are already smaller than the scaling parameters, then the wedge will not be affected by</p><p>the scaling.</p><p>Now let’s enter one more scaling parameter.</p><p>Select: Analysis > Scale Wedges</p><p>In the Scale Wedges dialog, select the Joint 2 (Trace Length) checkbox, and enter a Scaling</p><p>Value of 2.8 meters. Select OK.</p><p>Look at the Wedge Info panel in the Sidebar. The results are now as follows:</p><p>• For the Floor Wedge and the Roof Wedge, Scaled By = Joint 2 Trace Length, and Joint 2</p><p>Trace Length = 2.8 meters.</p><p>• For the Lower Left and Lower Right wedges, Scaled By = Joint 3 Trace Length, and Joint</p><p>3 Trace Length = 3 meters.</p><p>For the Floor and Roof wedges, the Joint 2 trace length (scaling value) is now the governing</p><p>parameter.</p><p>For the Lower Left and Lower Right wedges, the Joint 3 trace length (scaling value) is still</p><p>the governing parameter, since the Joint 2 trace lengths are already less than 2.8 meters,</p><p>therefore the Joint 2 trace length scaling value does not affect these wedges.</p><p>This illustrates the following important points:</p><p>• When you enter more than one Scaling Value, a given wedge is ultimately scaled by only</p><p>one parameter – the parameter which gives the smallest wedge size.</p><p>• Furthermore, if Wedges to Scale = All Wedges (in the Scale Wedges dialog), and you have</p><p>entered multiple scaling values, the governing scaling parameter can be different for</p><p>different wedges.</p><p>Unwedge v. 4.0 Tutorial Manual Tutorial 2: Scaling Wedges</p><p>2 - 9</p><p>For perimeter wedges which span multiple segments of the Opening Section (e.g. the Roof</p><p>wedge in this example), Unwedge uses an algorithm which searches for the wedge with the</p><p>maximum volume for the given Scaling Value(s). An iterative process is required to find this</p><p>wedge. This determines the position of the scaled wedge on the perimeter.</p><p>For wedges which are formed on a single flat surface of the excavation boundary, the</p><p>searching algorithm is not applicable, and the scaled wedge position will be approximately</p><p>centered on the surface.</p><p>So far in this tutorial, we have considered all wedges for scaling, using the same set of</p><p>scaling values.</p><p>It is also possible to consider individual wedges for scaling. This allows you to enter</p><p>independent scaling values for any desired wedge(s). To select individual</p><p>wedges for</p><p>scaling:</p><p>• You can select the desired wedge from the Wedge to Scale drop-list in the Scale Wedges</p><p>dialog.</p><p>• You can also right-click directly on a wedge, and select Scale Wedge for that particular</p><p>wedge from the popup menu, as shown in the following figure. This will display the Scale</p><p>Wedges dialog with the wedge already selected in the dialog.</p><p>Position of a Scaled Wedge</p><p>Scaling Individual Wedges</p><p>Unwedge v. 4.0 Tutorial Manual Tutorial 2: Scaling Wedges</p><p>2 - 10</p><p>For example:</p><p>1. Right-click on the Roof Wedge, and select Scale Wedge: 8 Roof from the popup menu, as</p><p>shown in the following figure.</p><p>2. In the Scale Wedges dialog, select the Joint 2 Trace Length checkbox and enter a scaling</p><p>value of 2 meters. Select OK.</p><p>3. Now look at the Wedge Info panel. The Roof wedge is now scaled by the Joint 2 Trace</p><p>Length = 2 meters. All other wedges are still scaled as before.</p><p>You can scale any or all wedges individually, in this manner. When you select individual</p><p>wedges to scale, the Scaling Value parameters are entered independently for each wedge,</p><p>and the dialog will “remember” the Scaling Values you have entered for each wedge.</p><p>NOTE: if you specify Scaling Values for All Wedges, AND for individual wedges, at the same</p><p>time in the Scale Wedges dialog, the program will use the Scaling Value which gives the</p><p>smallest wedge, for any given wedge.</p><p>Resetting the Maximum Wedge Size</p><p>To reset all wedges to the maximum size, select the Maximize button in the Scale Wedges</p><p>dialog. This will clear all of the Scaling Values, for All Wedges and also for any individual</p><p>wedge Scaling Values you have entered. However, it will NOT clear the Persistence and</p><p>Trace Length values entered in the Input Data dialog.</p><p>Unwedge v. 4.0 Tutorial Manual Tutorial 2: Scaling Wedges</p><p>2 - 11</p><p>We will now briefly discuss the effect of scaling the wedge size on the wedge safety factor</p><p>and support requirements.</p><p>Effect of Joint Strength</p><p>• Frictional Strength Only – if the shear strength of the joint planes is purely frictional</p><p>(cohesion = 0), then changing the size of an unsupported wedge will NOT change the</p><p>safety factor. You can verify this for the current example (the Joint Shear Strength of all</p><p>joints is given by Phi = 30 degrees, cohesion = 0).</p><p>• Friction and Cohesion – if the shear strength of the joint planes includes a non-zero</p><p>cohesion, then the safety factor of a wedge will, in general, depend on the size of the</p><p>wedge.</p><p>• Other parameters – water pressure, field stress and other parameters can also influence</p><p>the dependence of wedge size and safety factor.</p><p>Support</p><p>If support has been applied to a wedge (e.g. bolts or shotcrete), then in general, changing</p><p>the size of a wedge will affect the safety factor. This can be due to several factors:</p><p>• The wedge size may affect the number of bolts which intersect a wedge (pattern</p><p>bolting).</p><p>• The wedge size will affect the relative embedded lengths of a bolt. For a bonded bolt, the</p><p>length which passes through the wedge, and the length embedded in the rock mass will</p><p>determine the support force applied to the wedge.</p><p>• If shotcrete has been applied, then the wedge size will have a direct effect on the</p><p>exposed perimeter length of the wedge face. This has a direct effect on the support</p><p>force which is applied by the shotcrete.</p><p>In conclusion, wedge scaling is of particular importance during support design, since the</p><p>assumed wedge size can have a significant effect on the pattern spacing, positioning or</p><p>orientation of bolts, and the thickness or strength of shotcrete.</p><p>Wedge support is discussed in the next tutorial.</p><p>This concludes the tutorial on scaling wedge size in Unwedge.</p><p>Safety Factor and Scaling</p>