Study On The Pumping Pressure Loss Of Vertical Elbow

Pumping pressure will be lost during the concrete pumping process,and the pumping pressure loss is related to the flow performance of the concrete,the friction force between the concrete and the pipe wall,and the internal cohesion inside the concrete.The empirical calculation of pumping pressure loss in the present code is based on the slump test of ordinary concrete,and when calculating the pressure loss of the elbow,it is simply regarded equivalent to a horizontal straight pipe,which makes the pressure loss calculated from the empirical formula of the code quite different from the actual value,therefore,it is of great theoretical and practical significance to study the pumping pressure loss of the elbow.In the thesis,the stress of the pumping elbow was monitored and analyzed,and the numerical simulation analysis of the pumping pressure loss of the elbow is carried out.The conclusions were obtained as follows:(1)In the normal pumping state,the circumferential strain at the elbow is obviously larger than the axial strain,the circumferential strain and axial strain of the outer ring are both larger than those of the inner ring,and the stress distribution law of the inner and outer ring is basically same,and the stress of the pipe wall of the elbow increases with the increase of pump pressure.(2)The pumping pressure loss of the elbow increases linearly with the increase of concrete flow velocity;and the pumping pressure loss decreases with the increase of concrete slump,it indicates that the rheological properties of concrete directly influence on the pumping pressure loss.(3)Comparing the experimental calculation value,calculation value from the empirical formula of the code and calculation value from the elbow resistance formula of the pumping pressure loss,the results show that pumping pressure loss from the elbow resistance formula is closer to that of the experimental calculation value.Moreover,the calculation formula of the pumping pressure loss of the vertical elbow is derived from the test results.(4)The discrete element model of concrete pumping is established,and the bonding parameters of concrete particles are calibrated by the virtual slump test of concrete.When the flow velocity of concrete is constant,the pressure loss increases linearly with the opening angle of the elbow;through the linear fitting,the calculation formula for the pressure loss of the vertical elbow varied with the opening angle under different flow velocity and elbow radius is obtained in the thesis.