The invention discloses a water-rich sand layer shield
tunnel construction method. A constructed tunnel is a double-hole tunnel and is a subsurface tunnel with a hole body located in a water-rich sandlayer, the constructed tunnel comprises an underneath pass tunnel section passing through an existing viaduct and three non-underneath pass tunnel sections, shield construction is performed after theunderneath pass tunnel section is isolated and reinforced, and
precipitation is not needed. The shield construction is conducted after
precipitation of the non-underneath pass tunnel sections. The method is reasonable in design, easy and convenient to construct and good in using effect, a shield tunnel is divided into the underneath pass tunnel section and the non-underneath pass tunnel sectionsaccording to whether the viaduct is underneath pass or not, and construction is directly conducted after the non-underneath pass tunnel sections are subjected to
precipitation. The underneath pass tunnel section is isolated and reinforced to form a
slurry consolidated body, so that a
shield tunneling machine performs tunneling construction in the
slurry consolidated body, and soil disturbance andformation pressure caused by tunneling of the
shield tunneling machine during construction are resisted through the
slurry consolidated body. Separation walls are arranged on the two sides of the slurry consolidated body respectively, the formation pressure can be completely blocked, and safety and zero settlement of the viaduct on the upper side of the underneath pass tunnel section are guaranteed.