| 摘要 |
<p>DRAINAGE STRUCTURE FORMING METHOD A new and improved method for forming a drainage structure, such as a manhole for a subterranean sewer pipe. In a first embodiment, a removable outer form is positioned in an excavation in the earth extending to the sewer pipe so that the earth surrounding the sewer may be undercut and removed through the removable outer form. Concrete is poured into the undercut area surrounding the sewer pipe to a height adjacent the lower edge of the outer form and a second cylindrical inner form is positioned within the outer form so that concrete may be poured into the space between the forms to form upwardly extending wall portions to the surface. In a second embodiment, the outer form is positioned in an excavation at a predetermined location and a concrete base portion is formed. The inner form is positioned in the outer form and predetermined quantities of sand are poured into the space between the forms for facilitating connection with sewer pipes. In both embodiments, the outer form is raised and vibrated periodically during the pouring of sections of the wall portions and the inner and outer forms are removed after the wall portions have been poured to the predetermined height with a grate support means formed at the uppermost wall portion. -I-</p> |
