DBPapers
DOI: 10.5593/sgem2017/12/S02.092

SETTLEMENT OF BUILDING ON PILE FOUNDATION DUE TO THAWING OF FROZEN GROUND

S. Churkin, A. Nevzorov
Sunday 10 September 2017 by Libadmin2017

References: 17th International Multidisciplinary Scientific GeoConference SGEM 2017, www.sgem.org, SGEM2017 Conference Proceedings, ISBN 978-619-7105-99-5 / ISSN 1314-2704, 29 June - 5 July, 2017, Vol. 17, Issue 12, 719-726 pp, DOI: 10.5593/sgem2017/12/S02.092

ABSTRACT

Usually the frost heave of soils causes damages to low-rise buildings, road paving, and pipelines. However, a few years ago unusual deformations of a building supported by 18 meter piles were found. It was a cooling house designed for fish storage at the temperature of -22…-24°С. The building was 8,4m high; its plan dimensions were 24х42m. To protect the ground against the frost penetration a 0,9 m layer of light gravel under the concrete floor was filled and an electrical heating system under it was set up.
The building has been normally operated since 1985 but starting from the late nineties there were detected cracks occurrence on the floor. By 2012, the floor uplift reached 18 cm and the inner columns uplift - 13 cm. After that, the building was taken out of service. It was found by drilling boreholes that the ground under the centre of the building was frozen at the depth 8,1 m. Thus, the building deformation was caused by the heating system fail under the floor. The absence of ground temperature monitoring did not allow detecting the failure.
The next research step was the forecast of ground thawing time and settlement. This objective was achieved by numerical simulation using the software complexes “GeoStudio 2012” and "PLAXIS 3D". Several variants of the soil thawing were simulated. It was shown that maximum thawing rate could be reached by electrical heating. As a result, 150 electrodes buried into the ground were used.
The monitoring showed that the ground defrosting have completed in 4 months and the settlement of columns have achieved 55...60 mm. The difference between calculated and measured thawing time and settlement was not more 15...20 %.

Keywords: frozen ground, forecast of ground thawing time and settlement, numerical simulation