| China is a large agricultural country,and 61.4%of the country’s total annual water consumption is used for agricultural irrigation.Moreover,based on China’s basic national conditions,for a long time to come,channel water delivery will be the main form of agricultural irrigation.The channel is an important part of farmland water conservancy projects.Choosing a reasonable channel types can not only improve water delivery efficiency and reduce the frost heaving damage of channel,but also save land and reduce costs.The cross section of the parabolic channel is close to that of the natural open channel,and due to the good hydraulic performance and frost heave resistance,it has been popularized and applied in northern China.In addition,the channel adopts on-site pouring construction method,which has the problems of slow construction speed and difficult quality control etc.,while the prefabricated channel uses mechanical prefabricated concrete components in the factory,and the on-site mechanized rapid assembled installation,which has been widely used in small and medium-sized channels in recent years.However,due to its structural characteristics,the parabolic assembled channel adopts the optimum hydraulic cross section or practical economic section design,and its breadth depth ratio is too large,which is not conducive to the stable operation of the channel structure.Therefore,it is necessary to seek a cross-sectional form with a relatively small of breadth depth ratio,which is suitable for assembled.Based on the existing research on the parabolic assembled channel,this paper proposes the structural calculation method of the parabolic lap-ssembled channel,derives the structural internal force calculation formula,and optimizes the structure of the parabolic lap-assembled channel.The main research results are as follows:(1)According to the inner wall equation of the parabolic lap-assembled channel,the outer wall curve equation of the equal lining thickness is obtained by least square method;the formula for calculating the internal force of the parabolic lap-assembled channel structure is derived,and the structural calculation and reinforcement calculation methods are proposed.(2)Taking the tensile stress at the most easily damaged part of the horizontal and longitudinal direction of the prefabricated lining component of a single channel as the objective function,taking the flow velocity,the breadth depth ratio of the section,the bearing capacity of the channel structure and the structural crack resistance as the constraint conditions,the structural optimization model is established to optimize the channel.At the same time,the linear weighted sum method is used to transform the multi-objective optimization model into a single-objective model,and the MATLAB optimization function is used to solve the problem.The result shows that the width depth ratio is small,the stress performance of the structure is optimal,and the unit length cost is lower than the hydraulic optimal section and the practical economic section.(3)According to the structural characteristics and channel layout type of the parabolic lap-assembled channel,the mechanical properties of the lap structure are analyzed,the calculation formula of structure internal force is derived,and the optimization model is established with the minimum self weight of lapping structure as the objective function and the structural crack resistance as the constraint.By using the improved shuffled frog leaping algorithm to solve the optimization model,an optimal structure type of lap structure is obtained.(4)Using ANSYS-18.1 software to analyze the stress and displacement distribution of the parabolic lap-assembled concrete channel structure,the maximum error between the maximum stress value and the internal force calculation formula is 7.5%,which verifies the rationality of the structural optimization calculation method. |
