For the efficient hydraulic transportation of solids in pipelines, mud and sand with water through pipes it is necessary for us to observe and analyse the state of flow of them according to each velocity of flow.
　So we experimented in the laboratory on the sliding limit velocity and floating limit velocity of mud and sand in the horizontal pipe.
　The experimental equipment we used is made of pipes, diameter of which is 100 mm and length 70m, and exchangeable observation pipes made of acrylic resin or steel, each inside diameter of which is 50mm, 75mm, 100mm, are set on the pipe route.
　And we used sand as model materials, avarage diameter of which is 0.25mm, 0.81mm, 1.28mm and gravel, diameter of which is 7mm. For the measurement, we used following measuring apparatus.
　Pressure was measured by the strain-gauge type pressure gauge, flux by electro-magnetic flux meter, densimetry by density meter.
　The states of flow of snad and mud were observed with eyes and also photographed by 8mm motion picture camera and analysed.
　Through the analysis of experimental results, we concluded the limit velocity of flow (Vcd) for the sliding transportation of sand, diamter of which is more than 2mm, can be expressed as follow
　Vcd=ξ{g・(σ-1)・D}0.5・xd0.345
　where　ξ: experimental coefficient
　　　　　　g : gravitational acceleration
　　　　　　σ: specific gravity of sand
　　　　　　D : diameter of pipe
　　　　　　xd: real densty of discharged sand and mud mixed water
　Floating limit velocity (Vcf) ws also found to be expressed as follow
　Vcf=K2・D0.14・( σ-1)0.5・d0.36・xd0.089
　where K2: experimental coefficient
　　　　　　d: diameter of mud and sand
　By use of these results, we can presume the velocity and state of flow for the transportation of sand and mud mixed water through horizontal pipe.