A LACK OF investment in geotechnical services has put 20% of Moscow at risk of collapse, Russian geotechnical experts have told GE.
Recent ground collapses in the city have resulted in mayor of Moscow, Yuri Luzhkov, ordering a review of construction work amid concerns that other major failures could follow.
Professor Vladimir Baulin, exhead of the Geocryology Research Department at the Russian Federal State Enterprise, told GE that a lack of investment in geotechnical services while a spate of underground shopping centres and car parks have been built had made much of the city's ground unstable.
'In Moscow in the last 10 to 15 years, construction companies in pursuit of profi t have minimised the expenses for geotechnical research and have therefore increased the structural risks, ' said Prof Baulin.
He added that the recent collapse of a major section of the main road into the city, the Leningradsky Prospekt road - which sparked the current review of geotechnical construction work - was the result of inadequate geotechnical testing of the ground underneath.
Arup associate Steve Macklin, who has worked on large projects in the city, said the danger was particularly acute because construction of underground structures could destabilise the many caves that are underneath Moscow.
These caves were formed by chemical erosion, known as 'Karst', of the layers of mudstone and limestone, which comprise the city's strata. Holes in the highly permeable limestone had allowed groundwater to percolate through and this had slowly opened up voids varying in depth from 10m to 100m.
Some of the newly constructed basements were in danger of adding stresses around these voids and disturbing their strength, said Macklin. 'People are doing things that could disturb the stability of these caves. A 40m deep basement will change the loads in the ground.'
Baulin added that soils with Karst voids were affecting about 20% of Moscow, particularly in the west and south west of the city around the Moscow River.
Macklin claimed that Karst hazard maps would improve the chances of detecting these caves. Existing mapping of ground conditions in Moscow is limited, he told GE.
Baulin said the city authority had started a long-term project to map ground conditions but the work was far from complete. 'Some years ago, under the order of the Moscow government, Moscow Municipal Construction Codes (MGSN) were issued laying down the requirement to map the ground conditions.'
Fast completion of these maps was crucial because Moscow's construction boom, including underground structures, would continue unabated, said Baulin.
However, Hugh Doherty, director of Russia and Central Europe at consultant Waterman, which is structural engineer on a new tower proposed in Moscow, said: 'Ground conditions in Moscow can be quite a challenge but there's no reason to get overly concerned so long as the work is done in the proper manner.'