Mielenkiintoinen ratkaisu, lainaan tuosta samasta artikkelista pari pätkää:
The Kerch Strait is known to be geologically unstable. A tectonic fault passes through the ocean floor under the strait, and the bedrock is covered in a layer of silt up to 197 feet thick that must be dug through to get a stable foundation. Further complicating matters is that the strait’s seismic activity can make mud volcanoes from the silt. Mud volcanoes are formed when water heated deep in the Earth’s crust mixes with underground mineral deposits, and the mixture is forced upward through a geological fault. As of 2010, Ukraine’s Department of Marine Geology and Sedimentary Ore Formation
reported almost 70 mud volcanoes found in the Azov-Black Sea Basin where the Kerch Strait is located.
The bridge is supported by over 7,000 piles of three different varieties: bored piles (reinforced concrete piles poured into depressions on-site), prismatic piles (blunt, wedge-shaped supports), and tubular steel piles. These piles were driven up to 300 feet below water level because of concerns about stability.
But not everyone thinks these measures will be enough to keep the bridge steady on its perilous ground. Civil engineer
Georgy Rosnovsky, who previously designed two other possible versions of the Kerch Bridge, is troubled by the current design. He believes that the bridge is necessary, but has
stated that he thinks it's being built "in the wrong place and the wrong way." He believes the pilings need to be at least 100 meters (328 feet) long, and worries that they are not sunk deep enough into the bedrock to be stable.
Rosnovsky also thinks that the bridge's spans (the distance between supports) aren't long to allow ice floes through. He planned his 1993 bridge with spans of 230-660 meters (755-2,170 feet), but said that any spans over 200 meters would be safe from ice. The current design's longest span is 227 meters, but most of the spans are much shorter than that. According to Rosnovsky, this design puts the bridge at risk of suffering the same fate as the temporary bridge that was destroyed by ice floes in 1945.
Yuri Medovar, of the Russian Academy of Sciences, is another critic of the bridge. Talking to news agency Sotavision in late 2016, Medovar expressed concern that the area hadn't been sufficiently mapped, and that the complex geology and weather conditions would make the structure risky. He warned of the costs of poorly built bridges, citing the 2013 bridge collapse in Borisoglebsk that killed two people. "You can build everything, " he concluded, "but how much it will cost, and how [long will it] stand?"
En ole siltasuunnittelija mutta tiedän että Eurokoodi 3 käytetään teräsrakenteiden (mm. teräs sillat) laskentaan. Liekö betoniperustukset sitten omassa Eurokoodissaan, muistaakseni ne on jaoteltu materiaalin perusteella, taisi muutama olla myös ns. perusteista. Rakentamisesta tiedän vain sen verran että perustusten kanssa pitää olla tarkka ja maaperä pitäisi olla hyvin tiedossa, muuten voi tulla yllätyksiä jos maaperän kerrokset ei olekaan sitä mitä luultu. Siinä mielessä tuo kriitikon huoli paalutuksen syvyydestä kuulostaa kohtuulliselta, tosin riippuu millainen geologinen selvitys merenpohjasta on tehty.
Silloissa, kuten muissakin rakenteissa on aina moninkertainen varmistus / varmuuskerroin, joten ihan pieni kumaus tai osuma ei vielä riitä. Toisaalta jos perustuksia heikentää tarpeeksi niin hajoaa oman painonsa takia. Mietin että suora isku sillan kanteen ei ole ehkä paras, jos tekee vain reiän tai irroittaa lyhyen pätkän. Jos saisi tolppia heikennettyä perustasta sopivan toispuoleisesti, niin mahtaisiko saada tuon kaatumaan sivulle. Siinä voisi mennä pidempi pätkä siltaa ja korjaaminen vaikeampaa kuin lyhyt pätkä kantta...
sofrep.com
