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Abstract

Apparatus and method for constructing an impervious underground wall in which an initial excavation, filled with an excavating slurry, is made having a length L.sub.1. A milling excavator is lowered to the bottom of the initial excavation in a collapsed condition and then expanded outwardly by a linkage mechanism in the direction of the trench portion, transmitting a reaction or bearing force to a wall of the initial excavation to excavate from the bottom upwardly. The cuttings fall to the bottom of the trench and are removed by suction or an air lift. The initial excavation is thus expanded laterally from the bottom up with the excavation forces from the excavation being transmitted to the opposing wall surface. Precast concrete panels having convave sides, one concave and one convex end, are inserted into the excavation and have formations on the end to interlock with one another and serve as an excavating guide for the excavating tool. Plastic concrete fills the spaces between the excavation walls and the concave side faces of the precast elements. The apparatus includes a milling drum having a horizontal axis and mounted on an extendable linkage which, in turn, is carried by a main frame. The apparatus is lowered by cable to the bottom of the trench and one or more hydraulic rams are actuated to extend the milling drum which the rock mill is rotated by a preferably hydraulic drive motor. The main frame is guided by the precast panel and at the same time, the reaction forces from the excavation are horizontally transmitted to the adjacent previousy formed panel section.

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First Claim