Application of Air-solid Two-phase Flows to an Underground Digging System

Abstract

Underground water/gas transporting pipelines or cable-defective pipelines are important facilities of modern cities.Installation of such underground pipeline systems may be carried out by using underground digging machines with some trenchless techniques that can meet the requirements of minimum impact on the environment.In this paper, an underground digging method is introduced and discussed for transportation characteristics of dug soil.A distinct feature of the air transportation is that a special device is used for controlling the dug soil when it is sucked into a transportation pipeline by a vacuum pump.This transportation method is tested with sand, and the air-sand two-phase flow is measured by using visualization and pressure measurement.Visual observation with a video camera shows that air-sand plug flow is a flow pattern in the present transportation conditions.The pressure drop is discussed based on the visualization measurement.