Modelling Tunnel Lining

[dbest69er]

Hi guys,

I'm a graduate engineer and I'm looking at modelling a steel tunnel lining in Spacegass.

I have all of the information including the geotech report but I am having trouble inputting the support conditions. I know there should be springs (reflective of the soil spring stiffness) at the nodes on the circumference of the tunnel but I can only input these supports in either the X or Y directions and not RADIALLY, which would give a much more accuare refelctions. Any ideas of how one could solve this problem?

Any help from people with experience in this artea would be much appreciated!

http://s1.postimg.org/60oi6m30v/tunnel_liner.jpg

http://s3.postimg.org/vaqd0lkxv/tunnel_liner_2.jpg

 

[Trenno]

How about break each quadrant into 3 equal slices (30 deg each), then the vertical slice has springs in the vertical direction and the horizontal slice likewise.

The middle slice to have springs in both directions (each multiplied by 1/root2)?


Seems as though what you need is to manipulate each node's local axis, so it doesn't just refer to the global axis.

 

[dbest69er]

AHHH of course. I never thought about changing the global axis!

Thank you!

So you're saying I should just manipulate the axis of each node and then calculate the resultant stiffness using pytahgoras?

Regards,

Keith

 

[Trenno]

Well I have no clue how to change the global axis. But what you need is to change the reference axis of each individual node.

My slicing up the quadrants idea is based on not being able to manipulate the node's axis - thus why it's an approximation for each slice.

And yeah the middle slice based on a assumed 45 deg angle.

 

[Trenno]

 

[Trenno]

Nodes falling within each slice having springs as shown above.

 

[BUGGAR]

When we designed the stamped steel liner plates for the Westside Interceptor, we modeled them with rings cut from Styrofoam coffee cups. We supported them in various ways and poked at them in various ways. In the end, we hoped the liner plates would work in reasonably precise membrane fashion with controlled grouting. The tunnel didn't collapse.

 

[CELinOttawa]

Buggar - I love it....

 

[BUGGAR]

dbest69er (is that really your moniker? I wound up with Buggar)

What are you trying to accomplish with your analysis? What type of earth or rock are you trying to support? How are you modeling earth/rock pressures, as uniformly distributed?

Our problem was blocky rock that had large boulders coming loose from the tunneling process removing ambient rock pressure. The "goonies", what the miners called large falling rocks, couldn't be rock-bolted because of their immediate instability. We used stamped steel liner plates because we had them on hand. Everybody said we should be using cast steel or concrete liners due to the point loadings, but the Project Manager said, "Make the damned stamped plates work or you can all go to work for Kiewit!" (Kiewit paid low at the time. The liners did work and the Hudson River is now "clean".