Study On Shape And Structure Design Of Buried Flat-Bottomed Equal Section Of Bifurcation

Bifurcation should be installed when central or grouping water supply is employed in diversion system for hydropower station. However, the axises of all pipes sections are located at the same level, making bifurcation gravity drainage in the process of construction and inspection impossible, so the overhauled empty pipes can drainage with the help of pumps or setting up the drain hole. However, pumps are inefficient and the problems of concentration stress and brittle fracture should be caused by opening a hole in the bottom of the bifurcation. In order to solve the problem, Jinzhu Fu come up with the conception of design plan for flat-bottomed and equal section of bifurcation(FBESB), and on the basis of it, our research cooperation with Jinzhu Fu for developing further research of shape and structure aiming at FBESB on the research basis:(1) An efficient method is proposed for shape design of FBESB. Combining with spatial geometry theory which include the establishment of local coordinate system and global coordinate system, the derivation of analytical calculated method of shape design of FBESB is determined, which include outside diameter (D1) of bifurcation in round cake section, shrinking angle (γ)in elliptical tapered section,gradient section shrinking angle (α), net space of adjacent branch pipes (ls), semimajor axis length (b) of ellipse and bifurcation angle (ω). And the equation of intersecting curve of the main pipe and the branch pipe. By using programming languages software can make shape design of bifurcation procedural, and the method can significantly improve the efficiency of shape design of bifurcation.(2) The formula of pipe thickness is proposed for structure design of FBESB, which is by researching the main factors and influence of share rate of surrounding rock and structure stress in control section of bifurcation. For the control section of bifurcation namely the form of runway, developing research on the influence of share rate of surrounding rock and structure stress with elastic modlus of surrounding rock (Er), internal pressure of bifurcation (P), pipe thickness (t), gap between bifurcation with outsourcing concrete (△), buried depth, then engineering rules are revealed, namely the share rate of surrounding rock can reach more than 70% in the horizontal section of control section of bifurcation, and the preliminary formula of pipe thickness (t) is proposed, which establish the foundation of structure design.