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Li Shuping Liu Yuqing
Abstract: In the construction of municipal construction and environmental governance projects, rainwater and sewage pipelines often account for large investment ratios. Therefore, under various technical conditions meet the specified technical conditions, it is an important topic in the design of the design. From the optimized design of the stated pipeline, the planar optimization arrangement of the pipeline and the research of the rainwater runoff model 3 discusses the methods of designing the development of drainage pipeline systems and problems that need to be solved. It can be seen from it that there is still a need to invest in a lot of effort to research and improve its design calculation. Keywords: drainage pipe system optimized design plane arrangement runoff model
0 Introduction The drainage system is an indispensable important infrastructure in modern urban, is also the backbone project of urban water pollution prevention and urban staining and flood control and flood control. Among them, rainwater and sewage pipeline system investment in living residential area and mineral enterprises generally account for about 70% of the entire drainage system [1]. Therefore, how to reduce the infrastructure costs of the pipeline system when designing various technical conditions, which are designed to meet the design work of the design work. The design calculation method of traditional drainage pipeline system is that after the designer has mastered a more complete and reliable design basic information, it is determined a more reasonable sewage pipe plane arrangement according to the principle of pipeline and planar arrangement. The design flow rate of each design pipe section is then calculated, and the hydraulic calculation of each design pipe section is sequentially carried out from upstream to downstream, and the hydraulic calculation of each segment is sequentially performed from upstream to downstream. In checking the tube solenoids and depth depths. In the calculation, it is generally only possible to properly adjust the pipe diameter and slope of the pipe section, in order to achieve the purpose of the economy, but its reasonable level is limited by the designer's personal ability; on the other hand, most calculations use repeated consideration The method of the graph and the table is carried out, the working efficiency is low, long time, is not conducive to optimization of the design. Since the 1960s, the internationally established mathematical model of various water supply and drainage engineering systems or processes has been gradually established on the basis of experience summary and mathematical analysis, thereby developing water supply and drainage projects marked with quantitative and semi-quantitative marks. " Stage of reasonable design and management. At the same time, the optimization research and practice is carried out for various types of water supply and drainage systems [2]. In order to explore the optimal design calculation method of the drainage pipe system, many research, design, teaching units and individuals at home and abroad have made a lot of work, published a lot of articles. From the study results, the design calculation of the application computer is designed, not only from the heavy labor of the designer from the selection of the chart, but accelerate the design progress, but the entire drainage pipe system has been optimized, and the design quality is improved. The determined optimal solution can reduce the engineering cost of more than 10% compared to the conventional method [3]. Drainage pipeline system is a large and complex system, from existing research results, its design calculation mainly involves 3 aspects: (1) Tube diameter is performed in the pipeline plane arrangement - buried Optimization design; (2) Optimization selection of pipeline plane arrangement; (3) Establishment of rainwater runoff model. The flow of through the drainage pipelines usually has a overflow facility to limit the amount of water delivered to the local sewage treatment plant. Since the rain from overflow is also discharged into the river, the influence drainage system is actually the same for the influence of the drainage region of the drainage region from the perspective of the water supply area [4]. 1 Pipeline system optimization design under the pipeline is set in the pipeline plane arrangement, which has been used to optimize design problems, and have made a large pioneering work at home and abroad, and have achieved fruitful results. The optimization method is generally divided into two types: indirect optimization method and direct optimization method. The indirect optimization method also refers to the optimization of analytics. It is based on the optimization mathematical model. The optimization calculation is obtained by the optimization calculation; and the direct optimization method is based on the performance index, by direct pair of various programs or The selection, calculation, and comparison of adjustable parameters, to get the best solution or satisfaction [5].
1.1 Direct Optimization Method In Drainage Pipeline Optimization Design, the application direct optimization method is considered [6 ~ 8]: Although the hydraulic calculation formula used by the drain pipeline is simple, because the selectable size of the pipe diameter is not continuous, it cannot be arbitrary Select the pipe diameter; the maximum fullness limit is related to the size of the pipe diameter; regarding the minimum design flow rate, the flow rate change (increasing the design flow rate) and its constraints between the relationship between the pipe diameter are complex, and cannot Describe with mathematical formulas. Therefore, it is difficult to establish a complete math model for solving optimization problems to solve with an indirect optimization method. Relatively, use the direct optimization method to solve this problem with direct, intuitive and easy verification. 1.2 Indirect optimization method Application Indirect optimization method is considered: With the development of optimization technology, although there is an intricate constraint condition in the design calculation of drainage pipeline system, as long as some of these conditions are properly targeted, the mathematical tool is applied. It can simplify it, abstract as a mathematical model that is easy to solve, by calculating the optimal solution. According to the mathematical method of the time and use, the indirect optimization method is mainly divided into the following categories: 1.2.1 Linear planning method Linear planning method is the most common algorithm in the optimization method, which can solve many problems in drainage pipe design Also, you can also perform sensitivity analysis of the built drainage pipes. Its disadvantage is to handle the pipe diameter as a continuous variable, which has a problem of comparing the complar of the calculation of the tube and commercially available specification [9]. Moreover, all target functions and constraints are homogeneous to linear functions, and their pre-treatment workload is large, and it is difficult to guarantee. 1.2.2 Nonlinear Planning Method In order to adapt to the nonlinear characteristics of target functions and constraints in the optimization design of drainage pipeline systems, 1972 DAJANI and GEMMELL have established nonlinear planning models [10]. This method is based on the principle of guidance, that is, the derivative of the target function is a point, which is the best solution. It can handle the commercial specification pipe diameter, but when the drainage pipe fee function is not possible, the resulting calculation results may be partial best solution, not the global optimal solution. 1.2.3 Dynamic Planning Law In 1975, Mays and Yen first introduced dynamic planning methods into drainage pipeline system optimization design [11], the method is currently widely used at home and abroad. It is divided into two: one is a full-scale search with the various nodes to be used as a state variable. It has the advantage that the advantage is to directly utilize standard pipe diameters, optimized constraints and initial solutions, but can control calculation accuracy. However, the buried depth of state points is small, which makes the storage amount and calculation time increase [12]. In order to save operations, in 1976, the Dynamic Planning Law was introduced by Mays and Yen. Dynamic planning method is an iterative process of narrowing the scope based on dynamic planning law, which can significantly reduce calculation time and storage, but it is possible to miss the optimal solution during iteration, and processed under complex terrain conditions Limitable, the situation is limited [13 ~ 14]. The other is to search by a state variable in a pipe diameter, search through flow rate and fullness decision [15]. Since the number of standard pipe diameters is limited, there is a significant advantage in computer storage and computing time with a node burial as a decision variable method. The initial dynamic plan is not necessarily a feasible pipe diameter in a set of standard pipes selected for each pipe diameter. Therefore, a feasible pipe diameter method is developed. The method is analyzed by mathematical analysis, and the tube diameter of each tube is used to satisfy the maximum and minimum tube diameters between the constraint conditions, and constitute a feasible pipe diameter set, and the dynamic planning is applied. Calculate. The feasible pipe diameter method enables optimization calculation accuracy and significantly reduces the calculation workload and computer memory storage [16].
The dynamic planning method is an effective method for solving the optimization of multi-stage decision-making issues. Whether it is using a node buried or uses a pipe diameter as a state variable, there is no sufficient evidence to prove the "no-effect" of the stage state ("" There is no effect "means that when the state is given, the travel progression of each stage will not be affected by the previous stage state. Therefore, the sewage pipeline system optimized design scheme obtained by dynamic planning method is not necessarily true. 1.2.4 Genetic Algorithm Genetic Algorithm is an optimization technology that has developed rapidly in recent years. It is a random optimization algorithm proposed by natural genetic in the simulation of biology [17]. It still uses a specification pipe diameter as a state variable, which can search for many points in the feasible solution space, and finally seek satisfaction by selection, hybridization, and variation. Generally, the optimal design can be obtained when solving the optimization design of the small and medium-sized pipeline system; although the search method has certain randomness, when solving large piping system problems, the genetic algorithm can still seek a feasible approach to the best solution. Program [18]. In summary, indirect optimization methods and direct optimization methods are also applied and improved during the development of drainage pipeline system optimization design technology. The commonality of these two methods is to be constrained by design specifications and pipe diameters, flow rate, slope, and fullness of hydraulic relationships to achieve a minimum of costs. 2 Pipeline plane optimization arrangement researchers have pointed out that the optimization of different line scenarios is more applicable to optimized selection of different line scenarios. However, due to the design of the design of the pipeline is the basis of the pipeline plane arrangement, the optimization design calculation under the currently fixed line is not mature, causing the development of the system plane optimization arrangement. The earliest started this aspect is J.c.liebman (1976). In his study, the hydraulic factors were opened, assuming that each pipe diameter is the same, and the fees are preferred, and an initial arrangement scheme is selected, and then the trial algorithm is gradually adjusted. Since then, Argaman (1973) and Mays (1976) introduce the concept of draining lines in the flat arrangement, and use a drainage in the drainage region with the final water outlet node (ie, inspecting well). Line is connected. For any row of water, the upstream flow is downstream of the drainage stream [19]. Thus, the preferred problem of pipeline plane arrangement scheme is transformed into shortest circuit issues, and the dynamic planning method can be used. This model has taken into account the hydraulic factors, but due to the introduction of the drain line, the search range of the optimization process is limited in the feasible domain of the planar arrangement, even if the person with rich design experience may also put the optimal Solution is excluded. In addition, it is still unable to implement the maximum and calculation time long. In 1982, Walters improved the method, which was applied to the design of highway drainage systems. Over time, the researchers found that the urban drainage system plane arrangement can abstract the decision map composed of points and lines, so that the steering method is to find a plane optimized arrangement in the chart. In 1983, P.R.BHAVE and J.F.borlow applied to the minimum generating algorithm in the network chart to the drain pipe system planar arrangement scheme. Assuming that each of the systems in the system has the same weight, avoiding hydraulic factors, solving with a daily right method. In 1986, S.Tekel and H.Belkaya used three weight values to solve: (1) Record of ground slope of each pipe section; (2) Tascles of each pipe section; (3) Each pipe section is satisfied under the minimum soil conditions , The amount of digging when designing the minimum slope. The 3 types of weights use the shortest circuit generation of the label rules, and the optimized design of the pipe diameter, the depth and the pumping station is performed, and the minimum plan for the minimum investment is taken as the optimal design.
For a variant of all viable pipeline laying paths for drain pipe systems, the actual weight of each pipe section can only be calculated after the plan determination, so it belongs to the change in the chart direction, but it is so far that the change in the chart is There is no effective solution. In China, Li Guiyi (1986) proposed a minimalist gradient method, Chen Senfa (1988) proposed a degree optimization design method [20], which did not have satisfactory results. Recently, the emergence of genetic algorithms provides possible conditions for the drainage pipeline system planar optimization arrangement, as the genetic algorithm has no special requirements for the target functions and constraints. G.a.walters have applied genetic algorithms to study in urban water supply and drainage, farmland irrigation, cable and gas pipelines [21]. 3 Rainwater Runoff Models The design of my country's rainproof pipeline has been using the reasoning formula, and in 1974, the outdoor drainage design specification revised in 1987 was so specified. The method of reasoning the formula method is to assume that the water flow in the tuless channel is a uniform stream, and the flow of water flow in the pipe is assumed; then supplementing the water flow rate of the rain on the ground is equal to the flow rate of the water flow in the pipe, and the rain is waiting for the ground water time, The maximum design flow of the next tube segment is obtained from the rainstorm formula. A feasible pipe diameter is selected as the design tube diameter, and the desired hydraulic slope (or select a feasible hydraulic slope) is obtained by the hydraulic formula. The reasoning formula method is applied to the uniform formula of the Open or Uniform, which is simple and rapid. Due to the use of historical rainfall materials, it is possible to obtain a safe design. However, many studies have shown that the assumption of the derived formula is not reasonable in the reasoning formula method, there are some places in which not perfect, mainly in the following aspects [22]: (1) There is no spatial change in the rainfall. Since the actual heavy rain intensity is uneven in the rain area, when the exchange of water is large, the rain is long, and the design flow rate of downstream pipe segments calculated according to the formula will have a large deviation. (2) Theoretically makes excessive hypothesis, and users may use the parameters and constants published in other regions without inspection to save time. It is designed to have a certain blindness due to lack of sufficient instance. (3) Cooling flood flow can only be calculated, the complete runoff process is not possible, designing the rainwater regulating pool, the overflow drainage pipeline overflow flow calculation cannot be adapted. (4) The design reese period that is directly from the design rainstorm, which is transformed into the design render of drainage pipe, which is not fully confirmed. Marsalek (1978), Wenzel and Vooks (1978, 1979) indicate that the choice of rainfall, time course distribution, and pre-soil water content, has a great impact on flooding flow ~ frequency relationship, and some functions are there in these parameters. relationship. (5) Calculation requirements for the water row flow quality of the rain. Because the rainfall of high pollution concentration does not necessarily occur in the high floodpad process line. There is still a large amount of contaminants in the joint sewage out of the system overflow even for the flow of throughput pipes. In the past 20 years, with the increasingly prominent problems of urban runoff, the establishment of urban hydrology, hydrodynamic computing models in various precision is more important. Foreign countries have made great progress in this regard, many models have been widely used in the planning, design and management of rainwater pipeline systems. The most famous procedures in the West are [23]: the "Wallingford Procedure", the Wallingford Procedure, the National Water Resources Commission, the "Strain" model of the US Army Engineer Corps Water Literature Center (Storage, Treatment, Overflow, Runoff Mode Storm), the Rainwater Management Model of the US Environmental Protection Administration (Storm Water Management Mode SWMM).
These models can be more accurate to the entire urban rainfall, runoff process, and the simulation of the rainfall and the water quality of rainfall and the water quality of the radius and the water quality of the water body. Their development and engineering projects are closely combined. After the experience of the period, the government authorities organized coordination, and launched the design and managers for design and management of [24]. my country's research on urban runoff models is late, and there are currently some advent of the actual research results in my country. Simplified and movement wave simulation of rainwater pipe network [25] 4 Conclusion No matter how domestic or abroad, the theoretical calculation and engineering application of drainage pipeline system has been achieved, and there is still a number of expectations solved. With the development of calculation technology and system methods, it is an inevitable development trend to better research and develop drainage pipeline system design computing software.
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