An earthwork storage and allocation method based on return transportation requirements

Abstract

The present invention discloses a method for stockpiling and allocating earth and stone based on the demand for return transportation, including: introducing decision variables, representing the type of stockpile, the type of earth and stone stored in the stockpile, and the various earth and stone volumes between each excavation site and each stockpile through the decision variables; establishing associated constraints on the decision variables based on the stockpile type, the demand for excavation and return transportation, the stockpile capacity, and the actual value range of each decision variable; determining the first measurement target and the second measurement target by minimizing the total transportation distance and minimizing the amount of earth and stone excavated and returned from the mixed stockpile, introducing a trade-off coefficient, and constructing a mixed integer linear programming model in combination with the associated constraints; substituting numerical values ​​to solve the mixed integer linear programming model, and determining the optimized earth and stone stockpile allocation plan. The present invention establishes a classified stockpiling strategy, comprehensively considers the transportation distance and the amount of return excavation under constraints, and rationally utilizes limited resources to provide a more efficient and low-cost solution.

Description

Technical Field

[0001] The present invention belongs to the technical field of optimizing the storage and allocation of earthwork in earthwork projects. Specifically, it relates to an earthwork storage and allocation method based on the backhaul demand. Background Art

[0002] Earthwork balance is an important task in earthwork projects. Its main purpose is to scientifically and reasonably allocate excavated soil and fill to meet the requirements of the overall economy, environmental protection, and construction efficiency of the project. During project construction, the excavated materials (earthwork) usually need to be stored in a dedicated site. The specific quantity, type, and storage time of the stored earthwork are affected by various factors such as geological conditions, engineering design, and construction progress. In some engineering projects, due to construction requirements or design changes, etc., it may be necessary to transport some of the already stored earthwork back to the excavation site. For example, in a major canal project, the topsoil excavated from the excavation site needs to be reclaimed at the excavation site in the later stage. Therefore, during construction, the topsoil of the excavation site is usually transported to the storage site for storage and then transported back to the excavation site when reclamation is needed.

[0003] However, most traditional earthwork storage and allocation methods ignore the diversity of earthwork types. The earthwork that needs to be backhauled (such as topsoil) is mixed with other types of earthwork for storage. When reclamation is carried out, it is necessary to excavate the earthwork that needs to be backhauled (such as topsoil) from the mixed stored earthwork, which increases unnecessary excavation costs and delays the construction progress, and fails to maximize the engineering value and utilization efficiency of different types of earthwork. In addition, due to the differences in the particle size, shape, and texture of various earthwork, mixed storage will make the earthwork more vulnerable to erosion by water and wind, resulting in the loss of earthwork.

[0004] Therefore, based on the backhaul demand in the project, how to reasonably plan and formulate a plan to store and allocate the excavated earthwork to minimize the excavation cost of excavating earthwork from the storage site and the transportation costs during the transportation out and back is an urgent problem to be solved currently. Summary of the Invention

[0005] The present invention is made to solve the above problems, and its purpose is to provide an earthwork storage and allocation method based on the backhaul demand.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] An earthwork storage and allocation method based on the backhaul demand, comprising:

[0008] Step S1: Given the number and locations of the excavation sites, the number and locations of the stockpiling sites, the capacity of each stockpiling site, the types of earthwork, and the excavation and backhaul requirements for each type of earthwork, introduce multiple decision variables. Represent the type of stockpiling site, the type of earthwork stored in the corresponding stockpiling site, and the quantity of the corresponding type of earthwork transported between each excavation site and each stockpiling site through the decision variables. Among them, the types of stockpiling sites include classified stockpiling sites and mixed stockpiling sites;

[0009] Step S2: Based on the type of stockpiling site, the excavation and backhaul requirements of the earthwork, the capacity of the stockpiling site, and the actual value ranges of each decision variable, establish the associated constraints regarding the decision variables;

[0010] Step S3: Determine the first measurement objective by minimizing the total transportation distance of the earthwork and the second measurement objective by minimizing the quantity of the earthwork excavated and backhauled from the mixed stockpiling site. Introduce a trade-off coefficient between the first measurement objective and the second measurement objective, and further construct a mixed-integer linear programming model in combination with the associated constraints;

[0011] Step S4: Determine the trade-off coefficient according to the actual requirements, substitute the specific values of the known conditions, solve the mixed-integer linear programming model, obtain the quantity of each type of earthwork transported from each excavation site to each stockpiling site, and the quantity of each type of earthwork backhauled from each stockpiling site to each excavation site, and determine the earthwork stockpiling allocation plan.

[0012] Further, in Step S1, assume that it is known: the set of earthwork types is K, the set of excavation sites is I, the set of stockpiling sites is J, the excavation demand for type k earthwork of excavation site i is for type k earthwork is and the backhaul demand is , the designed capacity of stockpiling site j is , then the decision variables include:

[0013] Stockpiling site type variable ——Indicates whether the stockpiling site is used as a classified stockpiling site. Taking 1 means the stockpiling site is used as a classified stockpiling site, and taking 0 means the stockpiling site is used as a mixed stockpiling site;

[0014] Stockpiling earthwork type variable ——Indicates whether stockpiling site j only stores type k earthwork. Taking 1 means stockpiling site j only stores type k earthwork, and taking 0 means stockpiling site j stores not only type k earthwork;​

[0015] Mixed - field stockpiling variable —— Represents the volume of earthwork of a certain type stockpiled in a mixed manner from the excavation site to the stockpiling site;

[0016] Sorted - field stockpiling variable —— Represents the volume of earthwork of a certain type stockpiled in a sorted manner from the excavation site to the stockpiling site;

[0017] Mixed - field backhaul variable —— Represents the volume of earthwork of a certain type backhauled from the stockpiling site with mixed stockpiling to the excavation site;

[0018] Sorted - field backhaul variable —— Represents the volume of earthwork of a certain type backhauled from the stockpiling site with sorted stockpiling to the excavation site,

[0019] Among them, and are binary decision variables, , , and are all non - negative continuous decision variables.

[0020] Furthermore, in step S2, a first constraint formula is established based on the type of stockpiling site, indicating that when the stockpiling site is set as a sorted - stockpiling site, only one type of earthwork can be sorted and stockpiled; when the stockpiling site is set as a mixed - stockpiling site, a certain type of earthwork cannot be sorted and stockpiled.

[0021] Furthermore, in step S2, a second constraint formula and a third constraint formula are established respectively based on the actual value ranges of the stockpiling - site type variable and the earthwork type variable in the decision variables.

[0022] Furthermore, in step S2, a fourth constraint formula and a fifth constraint formula are established based on the earthwork stockpiling demand and the backhaul demand, which are used to ensure that the sum of the earthwork volumes transported from the excavation site to the sorted - stockpiling site and the mixed - stockpiling site meets the excavation demand, and the earthwork volumes backhauled from the sorted - stockpiling site and the mixed - stockpiling site to the excavation site meet the backhaul demand respectively.

[0023] Further, in step S2, a sixth constraint is established , which is used to ensure that the volume of earthwork transported back in the mixed storage yard does not exceed the storage volume; and a seventh constraint , which is used to ensure that the volume of earthwork transported back in the classified storage yard does not exceed the storage volume.

[0024] Further, in step S2, based on the actual value ranges of the mixed yard storage variables , the classified yard storage variables , the mixed yard transportation-back variables , and the classified yard transportation-back variables in the decision variables, an eighth constraint , a ninth constraint , a tenth constraint , and an eleventh constraint are established.

[0025] Further, in step S2, based on the storage yard capacity, a twelfth constraint is established, which is used to ensure that the total volume of earthwork transported into the mixed storage yard does not exceed its design capacity, and a thirteenth constraint , which is used to ensure that the volume of a specific type of earthwork transported into the classified storage yard does not exceed its design capacity.

[0026] Further, in step S3, the first measurement objective is determined by minimizing the total transportation distance during the earthwork storage and transportation-back process , where represents the transportation distance between the excavation yard and the storage yard; the second measurement objective is determined by minimizing the volume of earthwork excavated and transported back from the mixed storage yard . A trade-off coefficient is introduced between the first measurement objective and the second measurement objective, and a comprehensive measurement objective is established. Further, in combination with the associated constraints between the comprehensive measurement objective and the decision variables, a mixed-integer linear programming model is constructed.

[0027] Preferably, the value of the trade-off coefficient is 0.5.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. Under multiple constraints such as project demand volume and the designed capacity of the stockpile yard, the method for stockpiling and dispatching earthwork and stonework based on the backhaul demand of the present invention establishes a strategy for classified stockpiling in zones. By comprehensively considering the transportation distance and the backhaul excavation volume, it can rationally utilize limited resources to formulate a more efficient and low-cost solution, which helps to smoothly promote the engineering project.

[0030] 2. By reasonably setting the types of each stockpile yard, the method for stockpiling and dispatching earthwork and stonework based on the backhaul demand of the present invention enables the earthwork and stonework that needs to be backhauled to be more independently stockpiled in the classified stockpile yard, and minimizes the amount of earthwork excavated from the mixed stockpiled earthwork and stonework during backhaul. This not only avoids the additional manpower and material resources consumed by excavation, but also reduces the possible losses caused by excavating topsoil from the mixed stockpiled earthwork and stonework. Compared with the traditional method of mixing various earthwork and stonework for stockpiling, the classified stockpiling strategy in zones is also more environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a flowchart of the method for stockpiling and dispatching earthwork and stonework based on the backhaul demand;

[0032] Figure 2 is a schematic diagram of the positions of the excavation site and the stockpile yard;

[0033] Figure 3 is a schematic diagram of the earthwork and stonework transportation direction. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the following embodiments will specifically elaborate on the method for stockpiling and dispatching earthwork and stonework based on the backhaul demand of the present invention in conjunction with the accompanying drawings.

[0035] Embodiment 1

[0036] As Figure 1 shown, the present invention provides a method for stockpiling and dispatching earthwork and stonework based on the backhaul demand, including:

[0037] Step S1: Taking the number and positions of the excavation sites, the number and positions of the stockpile yards, the capacity of each stockpile yard, the types of earthwork and stonework, and the excavation demand volume and backhaul demand volume of various types of earthwork and stonework as known conditions, introducing multiple decision variables, and using the decision variables to represent the types of stockpile yards, the types of earthwork and stonework corresponding to the stockpiling in the stockpile yards, and the volume of corresponding types of earthwork and stonework flowing between each excavation site and each stockpile yard. Among them, the types of stockpile yards include classified stockpile yards and mixed stockpile yards;

[0038] Step S2: Based on conditions such as the types of stockpile yards, the excavation demand volume and backhaul demand volume of earthwork and stonework, the capacity of the stockpile yards, and the actual value ranges of each decision variable, establish associated constraints on the decision variables;

[0039] Step S3: Determine the first measurement objective and the second measurement objective by minimizing the total transportation distance of earthwork and minimizing the volume of earthwork excavated and transported back from the mixed storage yard respectively. Introduce a trade-off coefficient between the first measurement objective and the second measurement objective, and further construct a mixed-integer linear programming model by combining all relevant constraints;

[0040] Step S4: Determine the trade-off coefficient according to the actual demand, substitute the specific values of the known conditions, solve the mixed-integer linear programming model, obtain the quantities of various types of earthwork transported from each excavation site to each storage yard and the quantities of various types of earthwork transported back from each storage yard to each excavation site, and determine the earthwork storage allocation plan.

[0041] Further, in Step S1, it is assumed that: the set of earthwork types is K, the set of excavation sites is I, the set of storage yards is J, and the excavation demand for for class earthwork is , the backhaul demand is , and the designed capacity of the storage yard is . Then the decision variables include:

[0042] Storage yard type variable —— a binary decision variable indicating whether the storage yard is used as a classified storage yard. Taking 1 means the storage yard is used as a classified storage yard, and taking 0 means the storage yard is used as a mixed storage yard;

[0043] Storage earthwork type variable —— a binary decision variable indicating whether the storage yard only stores class earthwork. Taking 1 means the storage yard only stores class earthwork, and taking 0 means the storage yard not only stores class earthwork;

[0044] Mixed yard storage variable —— a non-negative continuous decision variable indicating the quantity of class earthwork mixed-stored from the excavation site to the storage yard ;

[0045] Classified yard storage variable —— a non-negative continuous decision variable indicating the quantity of class earthwork classified-stored from the excavation site to the storage yard ;

[0046] Mixed - field backhaul variable —— A non - negative continuous decision variable representing the volume of earthwork of a certain type backhauled from the storage yard with mixed stacking to the excavation site ;

[0047] Sorted - field backhaul variable —— A non - negative continuous decision variable representing the volume of earthwork of a certain type backhauled from the storage yard with sorted stacking to the excavation site ;

[0048] Furthermore, in step S2, an association constraint is established based on the type of storage yard:

[0049] Each storage yard can only perform sorted stacking when it is set as a sorted - stacking yard, and can only stack one type of earthwork, that is, when ; when the storage yard is set as a mixed - stacking yard, it cannot stack any type of earthwork, that is, when ; when ; thus, the first constraint formula is obtained, indicating that when the storage yard is set as a sorted - stacking yard, it can and can only stack one type of earthwork; when the storage yard is set as a mixed - stacking yard, it cannot stack only a certain type of earthwork. ;

[0050] In addition, since both the storage - yard type variable and the earthwork type variable in the decision variables are binary variables, according to their actual value ranges, the second constraint formula and the third constraint formula can be established.

[0051] Furthermore, an association constraint is established based on the earthwork storage demand and the backhaul demand:

[0052] The sum of the earthwork volumes transported from the excavation site to the sorted - stacking yard and the mixed - stacking yard should meet the excavation demand, and the earthwork volumes backhauled from the sorted - stacking yard and the mixed - stacking yard to the excavation site should meet the backhaul demand. Thus, the fourth constraint formula and the fifth constraint formula are established. For the convenience of calculation, the earthwork excavation volume, storage volume, and backhaul volume can all be converted into loose volume.

[0053] Assume that all storage yards have not stored any earthwork before the current project is used, that is, the default initial storage volume is 0. Then, the earthwork volume backhauled from the storage yard should not be greater than the earthwork volume transported into the storage yard. Thus, the sixth constraint formula , ensure that the volume of earthwork transported back in the mixed storage yard is not greater than the storage volume; and the seventh constraint , ensure that the volume of earthwork transported back in the classified storage yard is not greater than the storage volume.

[0054] Furthermore, considering that the volume of earthwork actually stored and transported back is at least 0, the mixed yard storage variable in the decision variables , the classified yard storage variable , the mixed yard transportation-back variable and the classified yard transportation-back variable are all non-negative continuous variables. Based on , , , , establish the eighth constraint , the ninth constraint , the tenth constraint , the eleventh constraint .

[0055] Furthermore, due to the limited capacity of the storage yard, the total storage volume of earthwork in each storage yard shall not exceed the designed capacity of the storage yard. Thus, establish the twelfth constraint , to ensure that the total volume of earthwork transported into the mixed storage yard does not exceed its designed capacity, and the thirteenth constraint , to ensure that the volume of a specific type of earthwork transported into the classified storage yard does not exceed its designed capacity.

[0056] Furthermore, in step S3, on the one hand, determine the first measurement objective by minimizing the total transportation distance during the earthwork storage and transportation-back process , where represents the transportation distance between the excavation site and the storage yard; on the other hand, since the earthwork transported back from the classified storage yard does not need to be excavated, thus determine the second measurement objective by minimizing the volume of earthwork excavated and transported back from the mixed storage yard .

[0057] During the earthwork balance process, if only considering minimizing the total transportation distance or minimizing the excavation volume for transportation-back, it may lead to the other item being too high. Therefore, introduce a trade-off coefficient between the first measurement objective and the second measurement objective, and establish a comprehensive measurement objective . The value of the trade-off coefficient can be determined by weighing according to the actual needs of specific engineering projects. Considering both indicators can not only ensure the convenience of transportation and the efficiency of construction, but also minimize the waste of resources, time, economic costs, etc. caused by excavating earthwork from the mixed storage yard.

[0058] Furthermore, by combining all the associated constraints that comprehensively measure the objectives and decision variables, a mixed-integer linear programming model is constructed: .

[0059] Furthermore, in step S4, the complexity of the model mainly depends on the number of excavation sites and stockpiling sites, as well as the types of earthwork and stonework. Determine the trade-off coefficient according to the actual project requirements, substitute the specific values of the known conditions, solve the mixed-integer linear programming model, obtain the quantities of various types of earthwork and stonework stockpiled from each excavation site to each stockpiling site, and the quantities of various types of earthwork and stonework transported back from each stockpiling site to each excavation site, and determine the earthwork stockpiling and allocation plan that meets the earthwork balance. Since the constraint conditions are all linear constraints, commonly used optimization solution software can be used to solve the model of general scale, so as to obtain the system-optimal earthwork stockpiling and allocation plan.

[0060] Embodiment 2

[0061] For a certain canal project, in order to meet the predetermined channel requirements of the project, a large amount of earthwork and stonework will be excavated from the designed river channel. The excavated earthwork and stonework need to be disposed of. The earthwork and stonework excavated on-site are transported to the stockpiling site for temporary storage, and later the topsoil is transported back from the stockpiling site to the excavation site for reclamation operations. Therefore, before the formal construction starts, it is necessary to pre-plan and formulate an earthwork stockpiling and allocation method, and on the basis of the traditional earthwork balance method, seek a more efficient and low-cost solution.

[0062] First of all, the known conditions include:

[0063] (1) The number of excavation sites is 4, which are respectively denoted as I1, I2, I3, and I4, and their distribution locations are as Figure 2 shown.

[0064] (2) The number of stockpiling sites is 10, which are respectively denoted as J1, J2, J3, J4, J5, J6, J7, J8, J9, and J10, and their distribution locations are as Figure 2 shown.

[0065] (3) The excavated earthwork and stonework are mainly divided into three categories, namely topsoil, other earthwork, and stonework. Among them, the topsoil needs to be transported back.

[0066] (4) According to the engineering design and the survey of the earthwork and stonework, the excavation requirements and the backhaul requirements of various types of earthwork and stonework in each excavation site can be estimated, and the results are shown in Table 1:

[0067] Table 1 Engineering requirements (unit: 10,000 cubic meters)

[0068]

[0069] For the convenience of subsequent calculations, the quantities of earthwork and stonework involved are all loose volumes. The earthwork and stonework in each excavation site are actually solid volumes before being excavated, and are converted into loose volumes through the loose-solid coefficient.

[0070] (5) The designed capacity of each storage yard is shown in Table 2 as follows:

[0071] Table 2 Designed Capacity of Storage Yard (unit: 10,000 cubic meters)

[0072]

[0073] (6) The transportation distances between each excavation site and storage yard are shown in Table 3 as follows:

[0074] Table 3 Transportation Distance (unit: km)

[0075]

[0076] (7) Considering comprehensively the total transportation distance of earthwork storage and backhaul and the amount of earthwork excavated from the mixed storage yard, the weighing coefficient is taken as 0.5.

[0077] Based on the above known conditions, a model framework is constructed by the earthwork storage and allocation method of Example 1, and the model is solved using optimization software. After 0.08 seconds of calculation, the quantities of various earthworks stored from each excavation site to each storage yard and the quantities of various earthworks backhauled from each storage yard to each excavation site are obtained, as shown in Table 4, so as to determine the earthwork storage and allocation plan.

[0078] Table 4 Model Solving Results (unit: 10,000 cubic meters)

[0079]

[0080] In Table 4, the values outside and inside the brackets respectively represent the quantity of earthwork transported from the excavation site to the storage yard and the quantity of earthwork backhauled from the storage yard to the excavation site. Figure 3 The arrow in it indicates the earthwork transportation direction. From Table 4 and Figure 3 it can be seen that: Storage yards J2, J3, J6 and J9 are set as classified storage yards, while other storage yards are used as mixed storage yards. Among the classified storage yards, J2 and J9 storage yards are used for classified storage of topsoil, J3 storage yard is used for classified storage of rockfill, and J6 storage yard is used for classified storage of other earthwork. According to the statistical calculation of the values in Table 4, it can be verified that the solution results not only achieve the cut-fill balance during the excavation process, but also achieve the cut-fill balance during the backhaul process, and while meeting the excavation requirements and backhaul requirements, do not exceed the capacity limits of each storage yard. In the finally obtained plan, the topsoil that needs to be backhauled is classified and stored, and there is no need to excavate topsoil from the mixed earthwork during backhaul, which not only avoids the additional human and material resources consumed by excavation, but also reduces the possible losses caused by excavating topsoil from the mixed earthwork.

[0081] In summary, the method for earth-rock storage and allocation based on the demand for backhaul under multiple constraints such as project demand and the designed capacity of the storage yard establishes a zoning and classification storage strategy, comprehensively considers the transportation distance and the backhaul excavation volume, can rationally utilize limited resources, and formulate a more efficient and low-cost solution on the basis of earth-rock balance, which helps to smoothly promote the engineering project.

[0082] The above embodiments are preferred cases of the present invention and are not used to limit the protection scope of the present invention.

Claims

1. A method for stockpiling and allocating earth and stone based on return transportation demand, characterized in that: include: Step S1: Taking the number and location of excavation sites, the number and location of stockpiles, the capacity of each stockpile, the types of earthwork, and the excavation demand and return demand of each type of earthwork as known conditions, multiple decision variables are introduced, and the stockpile type, the type of earthwork stored in the stockpile, and the corresponding type of earthwork volume between each excavation site and each stockpile are represented by the decision variables, wherein the stockpile type includes classified stockpile and mixed stockpile, and the decision variables include stockpile type variable, stockpile earthwork type variable, mixed stockpile variable, classified stockpile variable, mixed stockpile return variable, and classified stockpile return variable; Step S2: establishing association constraints on the decision variables based on the stockpile type, earthwork excavation demand and return demand, stockpile capacity, and actual value ranges of the decision variables; Step S3: determining the first measurement target and the second measurement target by minimizing the total transportation distance of earth and stone and minimizing the amount of earth and stone excavated and transported back from the mixed stockpile, respectively, introducing a trade-off coefficient between the first measurement target and the second measurement target, and further constructing a mixed integer linear programming model in combination with the association constraint; Step S4: Determine the trade-off coefficient according to actual needs, substitute the specific values ​​of the known conditions, solve the mixed integer linear programming model, obtain the quantity of each type of earth and stone transported from each excavation site to each stockpile site, and the quantity of each type of earth and stone transported back from each stockpile site to each excavation site, and determine the earth and stone stockpile allocation plan.

2. The earthwork storage and allocation method based on return transportation demand according to claim 1 is characterized in that: In step S1, it is assumed that: the set of earthwork types is K, the set of excavation sites is I, the set of storage sites is J, and the excavation demand of excavation site i (i∈I) for type k earthwork (k∈K) is O ik , the return demand is R ik , the design capacity of storage yard j (j∈J) is D j ,but: Storage yard type variable z j ——Indicates whether the stockpile is used as a classified stockpile. The value of 1 indicates that the stockpile j is used as a classified stockpile, and the value of 0 indicates that the stockpile j is used as a mixed stockpile; Variable y for the type of stockpiled earth and stone jk ——Indicates whether the stockpile j only stores Class k earth and stone. The value of 1 indicates that the stockpile j only stores Class k earth and stone. The value of 0 indicates that the stockpile j stores not only Class k earth and stone. Mixed field stockpile variables ——represents the volume of earth and stone of type k mixedly stored from excavation site i to stockpile site j; Classification field stockpile variables ——represents the volume of earth and stone of category k stored from excavation site i to storage site j; Mixed field return variable ——represents the volume of earth and stone of type k transported back from mixed stockpile j to excavation site i; Classification field return variables ——represents the volume of earth and stone of category k transported back from classified stockpile j to excavation site i, Among them, z j and jk is a binary decision variable, as well as are all non-negative continuous decision variables.

3. The method for stockpiling and allocating earth and stone based on return transportation demand according to claim 2 is characterized in that: In step S2, a first constraint formula is established based on the storage yard type. It means that when the storage yard is set as a classified storage yard, it can and only can store one type of earth and stone by classification; when the storage yard is set as a mixed storage yard, it cannot only store a certain type of earth and stone by classification.

4. The earthwork storage and allocation method based on return transportation demand according to claim 2 is characterized in that: In step S2, based on the storage yard type variable z in the decision variables j and stockpile type variable y jk The actual value range of the second constraint is established and the third constraint 5. The method for stockpiling and allocating earth and stone based on return transportation demand according to claim 2 is characterized in that: In step S2, the fourth constraint formula is established based on the earthwork storage demand and the return demand. and the fifth constraint They are used to ensure that the sum of the earth and stone volumes transported from the excavation site to the classified stockpile and the mixed stockpile meets the excavation demand, and that the sum of the earth and stone volumes transported back from the classified stockpile and the mixed stockpile to the excavation site meets the return demand.

6. The method for stockpiling and allocating earth and stone based on return transportation demand according to claim 2 is characterized in that: In step S2, the sixth constraint is established It is used to ensure that the return volume of various types of earth and stone in the mixed stockpile is not greater than the stockpile volume; and the seventh constraint Used to ensure that the amount of earth and stone returned from the classified stockpile is not greater than the stockpile amount.

7. The method for stockpiling and allocating earth and stone based on return transportation demand according to claim 2 is characterized in that: In step S2, based on the mixed field stockpile variable in the decision variable Classification field stockpile variables Mixed field return variable and the classification field return variables The actual value range of the eighth constraint is established Ninth Constraint The tenth constraint Eleventh Constraint 8. The method for stockpiling and allocating earth and stone based on return transportation demand according to claim 2 is characterized in that: In step S2, based on the storage yard capacity, the twelfth constraint formula is established To ensure that the total volume of earth and rock transported into the mixed stockpile does not exceed its design capacity, and the thirteenth constraint Used to ensure that the amount of a specific type of earth and rock transported into a classification stockpile does not exceed its designed capacity.

9. The method for stockpiling and allocating earth and stone based on return transportation demand according to claim 2 is characterized in that: In step S3, the first measurement objective is to minimize the total transportation distance during the earthwork storage and return transportation process. Among them, d ij represents the transportation distance between excavation site i and stockpile site j; the second measurement objective is to minimize the amount of earth and stone excavated and transported back from the mixed stockpile site A trade-off coefficient λ is introduced between the first measurement objective and the second measurement objective, and a comprehensive measurement objective min f=λf1+(1-λ)f2, λ∈(0,1) is established. The mixed integer linear programming model is further constructed by combining the association constraints between the comprehensive measurement objective and the decision variables.

10. The earthwork storage and allocation method based on return transportation demand according to claim 9 is characterized in that: in, The value of the trade-off coefficient λ is 0.5.

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