Analysis for Layered Subsoil
When determining a settlement of layered subsoil the program first calculates the settlement at the interface between the first layer above excavation and other layers of overburden Sint and determines the length of subsidence trough along the layer interfaces. In this case, the approach complies with the one used for a homogeneous soil.
Next (as shown in Figure) the program determines the length of subsidence trough L at the terrain surface.
Analysis of settlement for layered subsoil
The next computation differs depending on the selected analysis theory:
Solution according to Limanov
Limanov described the horizontal displacement above excavation with the help of lost area F:
where: | L | - | length of subsidence trough |
F | - | volume loss of soil per 1m run determined from: |
where: | Lint | - | length of subsidence trough along interfaces above the excavation |
Sint | - | settlement of respective interface |
Solution according to Fazekas
Fazekas described the horizontal displacement above excavation using the following expression:
where: | L | - | length of subsidence trough |
Lint | - | length of subsidence trough along interfaces above the excavation | |
Sint | - | settlement of respective interface |
Solution according to Peck
Peck described the horizontal displacement above excavation using the following expression:
where: | Lint | - | length of subsidence trough along interfaces above the excavation |
Sint | - | settlement of respective interface | |
Linf | - | distance of inflection point of subsidence trough from excavation axis at terrain surface |
Literature:
Széchy, Károly, The art of tunelling, Budapest : Akadémiai Kiadó, 1966.