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Identification of the Causes of a Landslide in Koronowo (Polish Lowlands)

Zabuski Lesław, Kulczykowski Marek, Świdziński Waldemar

Archives of Hydro-Engineering and Environmental Mechanics

2019

Vol. 66, nr 1-2

47--56

The paper discusses difficulties of identifying the causes of a landslide. These difficulties are illustrated in the example of a catastrophic landslide on the embankment of the western bank of the Brda River, which affected a bridge abutment of a disused narrow-gauge railway line from Bydgoszcz to Koronowo (Polish Lowlands). The railway was closed in 1992, and after the removal of the track, the bridge served as a pedestrian overpass. The landslide occurred in February 2011. Investigations revealed that the first signs of the landslide were cracks and subsidence that appeared at the embankment crest. Then, an initially slow movement accelerated suddenly, resulting in an over 45 m total displacement of the soil mass. The primary passive cause of the landslide movement resulted from the geology of the mass (loose soils underlain by cohesive soils) and from the steep inclination of the embankment surface. Active causes, however, are often ambiguous. In this case, no significant apparent phenomena which could trigger the movement occurred in the days preceding its initiation. Therefore, a detailed analysis of atmospheric conditions was carried out to identify and explain the causes. It was proved that the fundamental triggering cause of the landslide was a combination of rainfall, snowfall, snow-melting and air temperature. Moreover, an important cause was a faulty construction of a ditch with a sewage pipe on the crest of the embankment.

Warunki geologiczno-inżynierskie nasypu kolejowego w aspekcie procesów osuwiskowych

Dziadowska K., Noga L.

Prace Naukowe Instytutu Geotechniki i Hydrotechniki Politechniki Wrocławskiej. Konferencje

2007

Vol. 76, nr 42

159-165

W referacie przedstawiono warunki geologiczno-inżynierskie w nasypie kolejowym linii Wrocław-Legnica, które powodują procesy osuwiskowe. Zachodzące w nim procesy osuwiskowe są spowodowane nadmiernym zawilgoceniem gruntów i luźnym zagęszczeniem gruntów nasypowych. Nadmierne zawilgocenie gruntów wynika z infiltracji opadów atmosferycznych, filtracji wód z rzeki i zboczy oraz złej budowy nasypu piaszczystego i sposobu odwadniania. Zawilgocenie glin naturalnego podłoża powoduje zmianę ich konsystencji na plastyczną. W rezultacie po tej warstwie postępuje zsuw nasypu. Stan luźny i puste miejsca w gruntach nasypu świadczą o istnieniu sufozji i upłynniania się piasków, pod wpływem ciśnienia spływowego wody gruntowej oraz złego sposobu budowy nasypu, zwłaszcza podczas likwidacji wcześniejszych osuwisk.The geological-engineering conditions in the railway embankment of the Wroclaw-Legnica line are described. The landslide processes occurring in the embankment are caused by the soil's excessive moisture content and the loose compaction of the made ground. The excessive moisture content is the result of the infiltration of precipitation water, the filtration of water from the river and the slopes and the faulty construction of the sandy embankment and its drainage system. As a result of the excessive moisture content of the virgin soil clays their consistency changes to plastic. Consequently, the embankment slides on this stratum. The looseness of the embankment soil and the voids in it are evidence of tunnelling and liquefaction of the sands under the groundwater flow pressure and due to the faulty construction of the embankment, particularly during the removal of previous landslides.