Application of inclined big-diameter jet grouting for urban tunnel construction in Vietnam

Urban tunnel construction is often performed in congested areas with many buildings and historical structures nearby. With respect to developing countries, such as Vietnam, the lack of as-built drawings of existing buildings is a big challenge for urban tunnel development. There are a lot of private buildings in downtown are low rise, with many kinds of shallow foundations (from bamboo bar, brick mat, lean concrete mat, pre-casted concrete piles...) that add to the challenge of finding correct data. Consequently, one must find suitable and reasonable technology for the soil strengthening works in order to prevent the harmful impacts to the third -party properties and the tunnel structure itself. This paper introduces the inclined big-diameter jet-grouted column (iBDJ) technique that was recently applied with success in Hanoi Metro Line No3 project in Vietnam. This technique for protecting historical sensitive buildings that are in fuzzy of foundation information can be extended to urban tunnel projects in Vietnam and other countries which have similar conditions.