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 S_int and determines the length of subsidence trough along layers 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 after 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 excavation
	Sint	-	settlement of respective interface

Solution after 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 excavation
	Sint	-	settlement of respective interface

Solution after Peck

Peck described the horizontal displacement above excavation using the following expression:

where:	Lint	-	length of subsidence trough along interfaces above excavation
	Sint	-	settlement of respective interface
	Linf	-	distance of inflection point of subsidence trough from excavation axis at terrain surface

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Literature:

Széchy, Károly, The art of tunelling, Budapest : Akadémiai Kiadó, 1966