Sealing the zone between soil and rock to stop water and quick clay

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Deep excavations and foundation works performed in soft clay, are known to frequently cause costly damages to neighboring buildings and structures. In 2012, the Norwegian Research Council, NGI, and 22 partners funded a research project called “BegrensSkade”. The project aimed to identify possible causes for damages due to building activity, and by increasing the knowledge about these mechanisms also reduce risks for such damages ahead. In 2016, the research project concluded that the primary factors causing the excessive settlements were 1) the sheet pile walls being supported by drilled tie-back anchors, 2) drilling for piles (e.g. casing for steel core piles) being executed from the bottom of the excavation, and 3) all excavations extending to bedrock level have a potential for causing groundwater leakages and pore pressure reduction. The most common causes for pore pressure reduction were listed and cases were studied. In 2018, “BegrensSkade II” was initiated, to continue the studies on how to execute deep excavations in a safe manner for the surroundings, also covering vibrations, risk assessment etc. The work was sup-ported by 18 partners, including Huth & Wien Engineering AS (HWE). With more than 30 years of experience of grouting in soil and rock, for example to seal leakages below sheet pile footings, HWE could also contribute to the comprehensive guideline “Byggegropveiledningen”. Grouting can be performed with cement, polyurethane, or a combination of the two. At Havnelageret in Bjørvika, Oslo, HWE used one-component polyurethane in combination with cement suspension to seal substantial water leakages below the sheet pile wall. At Fornebubanen in Oslo, polyurethane grout was used to strengthen quick clay in a gap between a sheet pile wall and the bedrock. This paper describes how the sealing capability of polyurethane can be used to stop ingress of water and quick clay.

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