EXPERIMENTAL STUDY ON HYDRAULIC CHARACTERISTICS OF ASSEMBLY MANHOLE WITH SPIRAL CHANNEL

Abstract

In this study, we present a new assembly manhole to connect drainage pipes with a large hydraulic head difference. The manhole consists of spiral channel along the sidewall and spiral stairway around the center axis for maintenance. To investigate hydraulic characteristics of this manhole, we have performed laboratory experiments using hydraulic models of 1/15, 1/10 and 1/7.5 scales. We have measured velocity and surface elevation in the spiral channel and air pressure inside the manhole. A simple prediction model for the flow velocity was also developed by utilizing the Manning formula. The velocity and the water level along the spiral channel were reasonably estimated by the present model. The positive and negative air pressures were observed when the connecting pipes of upstream and downstream were in full depth. With the aid of the Froude similarity, we have confirmed that the velocity and pressure are allowable for the design of the prototype structures.