Excavation and Installation of pipe using micro tunneling procedure near existing MSE wall.

[sworddark90]

Hello, I have been given a task to conduct a review on impact assessment of irrigation pipeline construction on existing bridge (pipelines will be constructed 2.0 meter far from existing railway bridge wall on sandy soil and depth of 6 meter below existing ground level). What are the key things to check and consider when excavating near existing bridges? (I have noticed from the report, that volume loss due to the tunneling process, has significant effects on the supporting piles if volume loss were greater than certain limits.)

 

[EireChch]

how large is your pipe?

I am very surprised that you are allowed to go that close.

This is a case for 3D finite element modelling using Plaxis or similar.

You would likely need to check the magnitude of settlement and the change in stress in the soil.

The criteria for both needs to be developed with the structural and geotechnical working together.

If change in stress or settlement is too much they you may need to underpin the bridge foundations or install a retaining wall along the bridge foundation base.

 

[sworddark90]

800mm Diameter pipe and length is 50 meters. vertical Settlement of soil after excavation is very minor according to the results, however considering volume loss of 0.5%, abutment piles were having high bending moments (600kn.m) and soil lateral displacement was around 18mm due to the excavation and pile installation, near the MSE wall. Some parts of the project are open excavation trenches (cost reduction purposes) where other parts they are using micro tunneling procedure.

 

[EireChch]

why the reference to pile installation? are you constructing new piles?

 

[sworddark90]

Yes

 

[EireChch]

What are the new piles for?

Can you upload a section with all relevatn works?