# Tunnel Ground Settlement & Damage Calculator

## Calculate ground settelement and subsidence and building damage using the Burland method.

##### Tunnel Geometry
Tunnel axis depth m
Tunnel axis depth > radius and < max soil depth.
Tunnel external dia m
Enter number between 1 and 18.
Building height m
Enter number between 0 & 200.
Building start m
Enter number between -40 and +40.
Building end m
Enter number between -40 and +40.
##### Volume loss
VL (%)
Enter number between 1 and 13.
Estimated value
Soil name
Thickness (m)
K
For deepest strata measure to tunnel axis. List geology shallowest to deepest. K is typically ​~0.5 in clay and ​~0.25 in granular.

### 2. Damage assessment results:

Settlement under building:
-mm (max)
First stage assessment:
-
Second stage assessment:
-
Critical strain:
-
What's this calculator used for?
This tool can be used by Tunnel Engineers and Geotechnical Engineers to predict maximum short term and long term tunnel settlement and potential building damage. This tool uses the method put forward in the paper "Prediction of ground movements and assessment of risk of building damage due to bored tunnelling" by Burland et al (1977).

## What causes ground settlement?

• Two of the main causes of soil settlement are soil consolidation due to a reduction in voids between soil particles due to applied loads or changes in soil moisture content

## What causes tunnel settlement?

• Tunnelling causes settlement as there is always a volume loss which occurs around the profile of the tunnel. A tunnel boring machine or a mechanical excavator will not cut a perfect profile of the tunnel and voids will exist between the structural lining and the cut profile. Under the pressure of the ground above the tunnel the earth will relax and fill these open voids. The collapsing of these voids will then cause settlement to propogate to the ground surface level and result in a settlement trough. Applying a pressurised grout into these voids will fill these gaps and limit settlement.

## How to calculate tunnel settlement?

• Tunnel settlement can be predicted using empirical methods such as Burland et al (1977). This Burland settlement calculator uses this approach in calculating the differential settlement of structures and settement prediction. This is especially important in calculating foundation movement resulting from tunnel construction and calculation of building damage category and damage criteria.

## How to calculate damage class for buildings using the Burland approach?

• The tunnel settlement should first be calculated and the slope of the settlement trough in the location of the building determined, the relative deflection should then be calculated for the building and a final average settlement under the building calculated. Allowable structural settlements should be based on assessing the global stiffness of a structure and then estimating the relative deflections that will result from its interaction with the ground. The relative deflections are then comapred with the damage criteria given in the paper.