Wall-slip Mechanism During Pipeline Transportation Of High-concentration Cement Paste Backfill Slurry

Cemented paste backfill(CPB)is an environmentally friendly technology which reduces surface tailing stock as well as enhances the stability of country rock.The transportability of the slurry determines whether the filling system can operate efficiently for a long time.And the existence of wall-slip will seriously affect the transportability of slurry,but current development of CPB slurry slip theory is lagging.Therefore,a small visual pipeline transportation platform was established to directly obtain the wall slip velocity.At the same time,numerical simulation experiment was used to explore the wall-slip mechanism of CPB.The main research contents include the follows:1)The evolution law of slurry rheological parameters was explored.The unclassified tailing of a mine was selected as the filling and determine the physical and chemical properties of the tailing.A HAKKE rheometer with water bath heating device was used to test the rheological characteristics of CPB,and the rheological parameters of the CPB was obtained,which provides a basis for subsequent experiments.2)Detection of the regular of slip velocity.Based on PIV technology,a small test platform was designed to carry out relevant tests on slip behavior.It is found that concent and temperature have promoting effect on slip velocity and the increase of pipe diameter leads to the decrease of slip velocity.When the conveying flow increases,the slip velocity increases first and then decreases.Under the experimental conditions,when mud flow rate is 1.01m³·h^-1,the slip velocity reaches the maximum value of 0.0556m·s^-1.The empirical formula of slip velocity,and the drag equation considering the slip was derived.3)Analysis of slip drag reduction effect.A numerical model considering the slip effect was constructed,and the influence of concentration,diameter,and temperature on transportation resistance under the condition of slip was analyzed.The slip behavior of CPB was evaluated by friction drag coefficient and slip drag reduction rate.The research results will provide a basis for reducing transportation resistance and extending distance.Figure 33;Table 10;Reference 84...