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Development of software Ground Loss and its practical use

Sequential excavation of tunnel Mrazovka Zoom

The initial impulse to develop a program allowing engineers to instantly evaluate trend of surface deformations and their effects on existing buildings came during construction of twin-tube highway tunnel Mrazovka in Prague in 2001.

The core of the program is based on information assumed from national design standards, available technical literature and a database of relationships between shape of subsidence trough and its influence on damage of buildings in the settlement zones. Analysis of data collected during monitoring in affected zone above tunnel Mrazovka led to derivation of general criteria for evaluation of damage classification of multi-storey masonry buildings located above shallow tunnels. Input parameters and properties of the geological profile formed by clay slates and quartzite were also gained from the survey.

Dobrovskeho tunnel portal in Brno Zoom

Company SG-Geotechnika began to use the software for ground settlement predictions and also for evaluating parameters and properties of real subsidence troughs above all tunnels under construction.

Driving of prospecting gallery of tunnel Dobrovskeho Zoom

Next step in development of the program was its generalization for Sequential Excavation Method and interaction among more tunnels. Such case occurred in 2003 whilst driving three prospecting galleries for a future twin-tube highway tunnel. Besides geological data, the excavation supplied authors of the program with information about parameters “Loss of Ground” describing behaviour of overconsolidated clay.

Prospecting gallery of underground line IVC2 in Prague Zoom

Since the tunnel was also driven under housing estates, the program developers’ team obtained additional data on the relationships between shape of the subsidence trough and building damage. The data obviously show that combination of maximum settlement and gradient is not always the decisive factor of building damage. Wide and relatively shallow subsidence troughs, insignificant in terms of gradient, induced large horizontal tensile deformation causing heavy damage to load bearing structures of buildings located in the affected zone. The evaluation criteria for damage classification were updated accordingly.

Tunnel of underground line IVC2 in Prague Zoom

The program was also used for ground settlement monitoring during construction of underground line IV C2 and large single-nave underground station at Kobylisy in Prague.

Construction of underground line IVC3 in Prague Zoom
In this already known geological environment the software is capable of predicting settlement magnitude with accuracy of millimetres and at determining damage of the affected buildings including prediction of main crack locations together with their static consequences.

In cooperation with company Fine, developer of civil engineering software, the original program has been considerably improved and implemented into professional geotechnical software package GEO.


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Ground loss problem

Cracks in a masonry building due to ground movements

About author

The author, Radko Bucek MSc., Ph.D., is a distinguished expert in the field of underground structures. He gained his abundant experience while working with world-known consultant companies such as Golder Associates, SG-Geotechnika and D2-Consult. Recently he works as the Chief Tunnel Engineer in Mott MacDonald Prague.

In cooperation with company Fine, developer of civil engineering software, the original program has been considerably improved and implemented into professional geotechnical software package GEO.

References

Logo Consult

The software was used by Austrian company D2-Consult during preparation of underground line „Budapest metro line 4” in Budapest to predict ground settlement and its effects on surrounding buildings.
 

Logo Ko-Ka

Since 2005 the program has been continuously used by company KO-KA for designing collectors in Prague.
 

Mott MacDonald

Recently the software has been used by company Mott MacDonald, Prague. The author of the program works there as the chief engineer in branch of underground structures.