Flow state solidified soil backfilling construction method for narrow fertile groove with limited working face

Abstract

The invention provides a working face limited narrow fertile groove flow state solidified soil backfill construction method, and belongs to the technical field of flow state solidified soil application construction.The method comprises the steps that a backfill area is divided into partition blocks not exceeding 10 m and backfill sections with the thickness being 1 m, then an optimal backfill path is designed, and a cross path network is established to guarantee the filling uniformity; a multi-branch pumping system is adopted to convey the flow-state solidified soil, and flow velocity and pressure parameters are calculated by applying a hydrodynamic equation set. Construction is carried out according to the alternate sequence of 1-3-5-7 and 2-4-6-8 through a jump type pouring method, and the slump of the mixture is intelligently monitored and controlled to be 180-240 mm. Through penetration type electronic compactness detection, the unconfined compressive strength within 28 days is finally 0.8-1.5 MPa, the accumulative settling volume is controlled within 10 mm, high-quality control over backfilling of the narrow fertilizer groove space is achieved, and the technical problem that uniform backfilling construction of the flow-state solidified soil is difficult to control under the condition that the narrow fertilizer groove space is limited is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluidized solidified soil application construction, and in particular relates to a fluidized solidified soil backfill construction method for a narrow fertilizer trough with a limited working surface. Background Art

[0002] Fluidized solidified soil backfill technology is widely used in backfilling projects in narrow spaces, such as urban underground pipelines, tunnels, and subways. Traditionally, fluidized solidified soil backfill primarily utilizes a continuous pumping method, where large-scale mixing equipment centrally mixes the soil in open areas and then transports it via pipelines to the target area for continuous pouring. This method is simple to operate and highly efficient in conventional projects, and has developed a relatively mature technical system and standards.

[0003] However, when applied to space-constrained projects such as narrow fertilizer troughs, traditional continuous pumping methods face numerous technical difficulties. First, the narrow space restricts equipment layout and personnel operations, resulting in obstructed backfill paths and uneven material delivery. Second, continuous backfill cannot precisely control complex geometries, easily resulting in areas of incomplete filling. Third, traditional processes lack precise control over the rheological properties of fluidized solidified soil, resulting in uneven fill density and significant variations in settlement and deformation.

[0004] Currently, there is no systematic solution for backfilling fluidized solidified soil within the confined spaces of narrow fertilizer troughs. In particular, there is a lack of scientific computational models based on fluid mechanics and solidification reaction kinetics, making it impossible to precisely control the uniformity of fluidized solidified soil distribution and the quality of solidification within complex, narrow spaces. This technical issue urgently needs to be addressed. In other words, existing technologies present a technical challenge: difficulty controlling the uniform backfilling of fluidized solidified soil within the confined spaces of narrow fertilizer troughs. Summary of the Invention

[0005] In view of this, the present invention provides a construction method for backfilling fluidized solidified soil in a narrow fertilizer trough with a limited working surface, which can solve the technical problem in the prior art that it is difficult to control the uniform backfilling construction of fluidized solidified soil under the condition of limited space in a narrow fertilizer trough.

[0006] The present invention is implemented as follows: The present invention provides a construction method for backfilling fluidized solidified soil in a narrow fertilizer trough with a limited working surface, including: dividing the overall backfill area into a number of interconnected sub-blocks, each sub-block being no longer than 10 meters, and reserving a 0.5-meter transition zone between the sub-blocks; dividing each sub-block into multiple backfill sections with a thickness of 1 meter; designing the optimal backfill path according to the degree of spatial limitation of the fertilizer trough; forming a grid-like flow route by cross-setting the main backfill channel and the secondary backfill channel; adopting a multi-branch pumping system for complex fertilizer trough areas; pouring in an alternating sequence of 1-3-5-7 and 2-4-6-8; real-time monitoring of the slump of the mixture; using a penetrating electronic density tester to inspect the backfill quality; conducting a 28-day unconfined compressive strength test and settlement deformation monitoring; calculating the flow velocity of the main backfill channel and the flow velocity of the secondary backfill channel by applying a group of fluid dynamics equations, and determining the critical flow velocity to prevent pipeline blockage.

[0007] Among them, dividing the overall backfill area into several sub-blocks means dividing the working area according to the spatial size of the fertilizer trough, dividing the overall backfill area into several interconnected sub-blocks, each sub-block is no longer than 10 meters, and a 0.5-meter transition zone is reserved between the sub-blocks.

[0008] The division of each partition block into multiple backfill sections according to a thickness of 1 meter refers to vertical segmentation of each partition block according to depth, dividing it into multiple backfill sections according to a thickness of 1 meter, and determining the first-layer backfill elevation. Each backfill section needs to be numbered and marked on the site schematic.

[0009] Among them, designing the optimal backfill path based on the limited degree of space in the fertilizer trough means starting backfilling from the farthest end or deepest point to ensure one-way flow in the backfill channel and avoid mutual interference between operating equipment and personnel.

[0010] Among them, the grid-like flow route is formed by the intersection of the main backfill channel and the secondary backfill channel, which means that a cross-path network is set up in a narrow fertilizer trough, and a grid-like flow route is formed by the intersection of the main backfill channel and the secondary backfill channel to ensure uniform distribution of the fluidized solidified soil.

[0011] Among them, the multi-branch pumping system used in the complex fertilizer trough area means that the main line diameter is 100 mm, the branch line diameter is 75 mm, the length difference of each branch line does not exceed 5 meters, and the pumping pressure is controlled within 2 MPa.

[0012] Among them, the pouring in the alternating order of 1-3-5-7 and 2-4-6-8 refers to the use of a jump pouring method during the backfill process, and the discontinuous pouring of adjacent partition blocks. The jump pouring method is a construction method for discontinuously pouring adjacent partition blocks. Through intermittent construction, it ensures that the initial setting area and the newly poured area are staggered, reducing the overall settlement risk; that is, pouring in the alternating order of 1-3-5-7 and 2-4-6-8 ensures that the difference in material strength of adjacent partition blocks does not exceed 0.2 MPa.

[0013] Among them, the partitioning block is to divide the overall backfill space into several independent construction units according to the geometric shape and equipment operating radius, so as to facilitate the precise control of the backfill quantity and quality in batches; the backfill section is a construction unit that divides the vertical backfill height into 1 meter sections to avoid excessive stress on the bottom or incomplete filling on the top due to one-time backfilling; the backfill path is the optimal transportation channel for the fluidized solidified soil from the mixing equipment to the target filling area, which needs to avoid obstacles and maximize transportation efficiency.

[0014] The cross paths are mutually perpendicular or oblique conveying pipe systems set up in a narrow space, forming a grid-like coverage to ensure that the dead corner areas are fully filled.

[0015] The multiple branches are multiple secondary pipelines extending from the main conveying pipeline, which are used to simultaneously convey fluidized solidified soil to different directions or elevations to improve backfill efficiency.

[0016] This paper proposes a construction method for backfilling narrow fertilizer troughs with fluidized solidified soil, based on block-by-block backfilling and a cross-path network. Through spatial geometric partitioning and optimal path design, this method achieves uniform backfill within the confined space. This method applies a set of fluid mechanics equations to calculate the key parameters of the multi-branch pumping system, addressing the uneven transport resistance and large flow rate variations of fluidized solidified soil within narrow fertilizer troughs, ensuring uniform distribution of the backfill material within the complex space.

[0017] This invention utilizes a construction organization model that combines a jump-cast method with curing reaction kinetics, effectively overcoming the uneven density and large variations in settlement deformation associated with traditional continuous backfilling. By scientifically calculating the initial setting time and the development of hardened strength, it achieves coordinated and unified material properties in adjacent sub-blocks, significantly improving the uniformity and controllability of backfill quality.

[0018] By integrating technical means such as space division, path optimization, multi-branch pumping and jump-type pouring, the present invention successfully solves the technical problem of difficult-to-control uniform backfill construction of fluidized solidified soil under limited space conditions in narrow fertilizer troughs, providing reliable technical guarantee for backfill projects in narrow spaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1is a flow chart of the method of the present invention.

[0020] Figure 2 This is a schematic diagram of the overall structure of the intelligent fluidized solidified soil mixing equipment in Example 2.

[0021] Figure 3 Schematic diagram of the stirring system structure in Example 2.

[0022] Figure 4 This is a schematic diagram of the monitoring system structure in Example 2.

[0023] Figure 5 This is a schematic diagram of the control system architecture in Example 2. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0025] like Figure 1 FIG. 1 is a flow chart of a method for backfilling fluidized solidified soil in a narrow fertilizer trough with a limited working surface provided by the present invention. The method comprises the following steps:

[0026] S01. Divide the working area according to the spatial dimensions of the manure trough, and divide the entire backfill area into several interconnected sub-blocks. The length of each sub-block shall not exceed 10 meters, and a 0.5-meter transition zone shall be reserved between the sub-blocks.

[0027] S02. Divide each block vertically into sections according to depth, dividing it into multiple backfill sections with a thickness of 1 meter. Determine the first-floor backfill elevation. Each backfill section must be numbered and marked on the site schematic.

[0028] S03. Design the optimal backfill path based on the limited space in the manure tank, starting from the farthest end or deepest part to ensure one-way flow in the backfill channel and avoid interference between operating equipment and personnel;

[0029] S04. Set up a cross-path network in the narrow fertilizer trough, and form a grid-like flow route by intersecting the primary backfill channel and the secondary backfill channel to ensure uniform distribution of the fluidized solidified soil;

[0030] S05. For complex fertilizer trough areas, a multi-branch pumping system should be used. The main line diameter should be 100 mm, the branch line diameter should be 75 mm, and the length difference between the branch lines should not exceed 5 meters. The pumping pressure should be controlled within 2 MPa. The flow velocity of the main backfill channel and the secondary backfill channel should be calculated using the fluid dynamics equations to determine the critical flow velocity to prevent pipeline blockage.

[0031] S06. During the backfill process, a skip pouring method is used. Adjacent sub-blocks are not poured continuously. Instead, they are poured in an alternating sequence of 1-3-5-7 and 2-4-6-8. This ensures that the difference in material strength between adjacent sub-blocks does not exceed 0.2 MPa. The construction interval is determined based on the initial setting time calculated by the curing reaction kinetics equation.

[0032] S07. Use intelligent fluidized solidification soil mixing equipment to monitor the slump of the mixture in real time, controlling the slump between 180 and 240 mm. Use the solidification reaction kinetics equation to predict that the strength will reach above 0.3 MPa within 12 hours, providing a working surface for the next day's construction.

[0033] S08. Conduct quality inspection on the backfilled area. Use a penetrating electronic density tester to sample at least 3 points per 100 square meters. The density should be no less than 95%. At the same time, the surface flatness deviation should not exceed 10 mm.

[0034] S09. After completing all backfill operations, conduct a 28-day unconfined compressive strength test. The strength value should be within the range of 0.8 to 1.5 MPa. The settlement deformation should be monitored throughout the process by a recorder, and the cumulative settlement should be controlled within 10 mm.

[0035] Partitioning specifically refers to dividing the overall backfill space into several independent construction units based on geometric shapes and equipment operating radius, so as to facilitate precise control of backfill quantity and quality in batches;

[0036] The backfill section specifically refers to a construction unit with the vertical backfill height divided into 1-meter sections to avoid excessive stress on the bottom or incomplete filling at the top due to one-time backfilling.

[0037] The backfill path specifically refers to the optimal transportation channel for the fluidized solidified soil from the mixing equipment to the target filling area, which needs to avoid obstacles and maximize transportation efficiency;

[0038] Cross-path refers to a system of perpendicular or obliquely intersecting pipelines set up in a narrow space, forming a grid-like coverage to ensure that blind spots are fully filled.

[0039] Among them, multi-branch specifically refers to multiple secondary pipelines extending from the main conveying pipeline, which are used to simultaneously convey fluidized solidified soil in different directions or elevations to improve backfill efficiency;

[0040] The skip pouring method specifically refers to a construction method that non-continuously pours adjacent sub-blocks. Through interval construction, it ensures a staggered arrangement between the initial setting area and the newly poured area, reducing the overall settlement risk.

[0041] Among them, slump specifically refers to an indicator for measuring the fluidity of fluidized solidified soil. The slump cone is used to measure the sinking height of the sample after leaving the cylinder, reflecting the flow properties of the mixture.

[0042] The fluid dynamics equations specifically refer to the Bernoulli energy equation, pipeline resistance equation, sedimentation stability equation, and solid phase separation critical equation used in the design of multi-branch pumping systems.

[0043] Among them, the Bernoulli energy equation is used to calculate the pressure and flow rate distribution in the multi-branch pumping system. The input includes the main line diameter, the branch line diameter, the fluidized solidified soil density, the pipeline length and the pumping power. The output is the main backfill channel flow rate and the secondary backfill channel flow rate. The main line diameter is obtained in step S05, the branch line diameter is obtained in step S05, the fluidized solidified soil density is measured by the intelligent fluidized solidified soil mixing equipment in step S07, the pipeline length is determined according to the backfill path designed in step S03, and the pumping power is provided by the construction equipment parameter table. The main backfill channel flow rate and the secondary backfill channel flow rate are used to control the flow uniformity of the cross-path network in step S04;

[0044] The pipeline resistance equation is used to calculate the pressure loss of fluidized solidified soil during the pumping process. The inputs include fluidized solidified soil viscosity, pipeline roughness, number of elbows, main pipeline diameter, and branch pipeline diameter. The output is the pumping pressure. The fluidized solidified soil viscosity is obtained by converting the mixture slump in step S07. The pipeline roughness is provided by the technical parameter table of the pipe supplier. The number of elbows is determined based on the cross-path network design in step S04. The main pipeline diameter and branch pipeline diameter are obtained in step S05. The pumping pressure is used to control the operating parameters of the pumping system in step S05.

[0045] The settlement stability equation is used to assess the risk of stratification of fluidized solidified soil during pumping. The inputs include suspended particle size distribution, fluidized solidified soil density, stagnation time, main pipe diameter, and branch pipe diameter. The output is the maximum pumping distance. The suspended particle size distribution is obtained by the soil gradation curve after drum sieving. The fluidized solidified soil density is measured by the intelligent fluidized solidified soil mixing equipment in step S07. The stagnation time is determined according to the construction schedule. The main pipe diameter and branch pipe diameter are obtained in step S05. The maximum pumping distance is used to guide the optimal design of the backfill path in step S03.

[0046] Among them, the solid phase separation critical equation is used to determine the operating parameters to prevent pipeline blockage. The input includes the solid phase volume fraction, the maximum particle size, the fluidized solidified soil viscosity, the pumping pressure and the main line diameter. The output is the critical flow rate. The solid phase volume fraction is calculated by the intelligent fluidized solidified soil mixing equipment in step S07. The maximum particle size is determined by the sieve hole diameter of the drum screen. The fluidized solidified soil viscosity is obtained by converting the mixture slump in step S07. The pumping pressure is obtained according to the calculation result of the pipeline resistance equation. The main line diameter is obtained in step S05. The critical flow rate is used to control the minimum operating speed of the multi-branch pumping system in step S05.

[0047] Among them, the curing reaction kinetics equation is used to predict the strength development process of fluidized solidified soil. The input includes curing agent dosage, soil moisture content, ambient temperature, mixing time and soil mineral composition, and the output is initial setting time and hardened strength. The curing agent dosage is provided by the fluidized solidified soil mix ratio design, the soil moisture content is obtained by measuring the intelligent fluidized solidified soil mixing equipment, the ambient temperature is recorded by the on-site temperature sensor, the mixing time is recorded by the intelligent fluidized solidified soil mixing equipment control system in step S07, and the soil mineral composition is obtained by X-ray diffraction analysis. The initial setting time is used to determine the construction interval of the jump casting method in step S06, and the hardened strength is used to predict the 28-day unconfined compressive strength in step S09.

[0048] The specific implementation of the above steps is described in detail below.

[0049] The specific implementation of step S01 is to scientifically divide the work area according to its geometric characteristics. First, a total station is used to measure the spatial dimensions of the fertilizer trough, including length, width, and depth, to obtain precise geometric parameters. Then, based on a spatial complexity clustering algorithm, the backfill area is divided into multiple interconnected sub-blocks. The sub-block length is controlled within the range of 8 to 10 meters to ensure that each sub-block can be backfilled in a single operation. At the same time, a construction area subdivision technique is used to reserve a 0.5-meter-wide transition zone between adjacent sub-blocks. The transition zone is used to alleviate boundary stress concentration and serve as a buffer zone for structural deformation. Finally, a computer-aided design system is used to draw the sub-block layout plan into a construction guide, annotating the sub-block number, size parameters, and construction sequence. The purpose of this step is to solve the problem of limited operation of large equipment in narrow spaces by rationally dividing the construction units, and to create an orderly and controllable working environment for subsequent backfill operations.

[0050] The specific implementation method of step S02 is to use a vertical layering strategy to accurately control the backfill of the sub-blocks. First, use a level to measure the base elevation of each sub-block to determine the starting elevation of the first layer of backfill. Then, according to the layered backfill theory, the vertical backfill height is evenly divided into multiple 1-meter thick backfill sections, and each backfill section is numbered with a unique identifier. Then, using digital twin technology, a virtual backfill model is established in the 3D modeling software, and the backfill section information is mapped to the virtual model. Then, based on the differences in geological conditions of each backfill section, differentiated backfill parameters are set to ensure consistent backfill quality for each layer. Finally, a site schematic is generated, and the backfill section number, elevation, and backfill sequence are annotated using color coding. The purpose of this step is to avoid the problem of overpressure at the bottom or lack of solidity at the top caused by a one-time large-thickness backfill through vertical segmentation, and to achieve uniform and controllable backfill quality for each layer.

[0051] The specific implementation method of step S03 is to apply a path planning algorithm to design the optimal route for backfill operations. First, 3D laser scanning technology is used to obtain a precise geometric model of the fertilizer tank space, identifying spatial restriction points and obstacle locations. Then, an improved A-star search algorithm is used to calculate the optimal backfill path from the starting point to the end point, using the spatial narrowness, obstacle distribution, and equipment operating radius as path cost function parameters. Next, the principle of reverse flow of backfill is applied to determine the construction sequence of backfilling from the farthest end or deepest point to avoid subsequent backfilling operations from interfering with the completed area. The feasibility of the path is then verified through simulation to ensure that the equipment can successfully complete the backfill operation in the narrow space. Finally, a one-way flow backfill channel navigation map is generated, clearly marking the equipment entry route and personnel evacuation channel. The purpose of this step is to solve the problem of limited operation of backfill equipment in narrow fertilizer tanks and ensure a safe and efficient construction process through optimal path planning.

[0052] The specific implementation method of step S04 is to construct a cross-network backfill pipe system. First, computational fluid dynamics software is used to analyze the flow characteristics of the fluidized solidified soil in the narrow fertilizer trough to identify potential dead corners. Then, a grid division algorithm is used to divide the backfill area into a grid structure where the main backfill channel intersects with the secondary backfill channel. The spacing between the main backfill channel does not exceed 5 meters, and the spacing between the secondary backfill channels does not exceed 3 meters. Then, using the pressure gradient distribution principle, a pressure balancing device is designed at the intersection of the main and secondary backfill channels to ensure balanced flow in each branch pipe. Subsequently, the pipeline layout is optimized through the pipe network hydraulic calculation model, and the intersection angle of the main and secondary backfill channels is adjusted within the range of 60° to 90° to reduce flow resistance. Finally, a pulse flow control system is configured to ensure that the grid flow route covers the entire backfill area through periodic flow regulation. The purpose of this step is to solve the problem of uneven distribution of fluidized solidified soil in narrow spaces, ensure that dead corners are fully filled, and improve backfill quality.

[0053] The specific implementation method of step S05 is to design a multi-branch collaborative pumping backfill system. First, the topology of the pumping system is determined based on the complexity analysis of the backfill area, and the required number of main branches is calculated; then the pipeline network optimization algorithm is used to design the connection method between the main pipeline and the branch pipeline. The diameter of the main pipeline is set to 100 mm, the diameter of the branch pipeline is 75 mm, and the length difference of each branch pipeline is controlled within 5 meters; then the flow dynamics equations are applied to calculate the optimal pumping parameters, including flow velocity, pressure and flow rate, among which the flow velocity of the main backfill channel is controlled at 0.8~1.2 m / s, the flow velocity of the secondary backfill channel is controlled at 0.5~0.8 m / s, and the pumping pressure is maintained in the range of 1.5~2.0 MPa; then the pipeline pressure and flow changes are monitored in real time through the feedback control system. When the pressure exceeds 2.0 MPa, the pumping rate is automatically adjusted; finally, a critical flow velocity alarm mechanism is set. When the pipeline flow velocity is lower than the critical value of 0.3 m / s, the pipeline cleaning program is triggered to prevent blockage. The purpose of this step is to solve the problem of low backfill efficiency in complex fertilizer trough areas, improve construction efficiency and ensure pumping safety through multi-branch coordinated pumping.

[0054] The specific implementation of step S06 involves implementing a jump-backfill strategy to control settlement and deformation. First, the initial setting time of the fluidized solidified soil is calculated based on the curing reaction kinetics equation to determine the construction interval, which is typically within 2 to 4 hours. A discontinuous pouring technique is then used, with backfilling performed in sections alternating between the 1-3-5-7 and 2-4-6-8 sequences to avoid pouring adjacent sections simultaneously. Nondestructive testing techniques are then used to monitor the strength development of the completed sections, ensuring that the strength difference between adjacent sections does not exceed 0.2 MPa. Finite element analysis is then applied to predict the stress distribution and deformation trends of the overall backfill area, dynamically adjusting the backfill plan for subsequent sections based on the analysis results. Finally, a backfill quality control feedback system is established to guide the jump-back pouring process using real-time strength data. The purpose of this step is to reduce the overall settlement risk caused by large-scale backfilling and improve the stability of the backfill structure through a staggered construction sequence.

[0055] The specific implementation of step S07 involves using intelligent mixing technology to control the quality of fluidized solidified soil. First, intelligent fluidized solidified soil mixing equipment with real-time monitoring capabilities is configured, including an automatic batching system, a precise metering device, and a quality monitoring module. A slump prediction model is then established using a neural network algorithm to predict the slump of the mixture based on raw material properties, ambient temperature, and mixing parameters. Closed-loop control technology is then used to adjust the water-cement ratio and mixing time in real time to precisely control the slump within a range of 180 to 240 mm. The strength development curve is then predicted based on the curing reaction kinetics equation to ensure that the mixture reaches a strength of at least 0.3 MPa within 12 hours. Finally, the backfill's bearing capacity is calculated using the boundary element method to verify the conditions for the next day's construction. The purpose of this step is to ensure the stability of fluidized solidified soil quality through intelligent mixing technology, creating conditions for continuous construction.

[0056] The specific implementation method of step S08 is to perform systematic quality inspection and evaluate the backfill effect. First, a penetrating electronic density tester is used to grid the backfill area, with no fewer than 3 inspection points set for every 100 square meters. Then, a stratified sampling inspection method is used to test the density of each backfill section, with the acceptance standard being a density of no less than 95%. Then, 3D laser scanning technology is used to fully measure the backfill surface, generate a high-precision surface model, and evaluate the flatness deviation, controlling it within a range of 10 mm. Statistical process control methods are then applied to analyze the inspection data and identify areas with potential quality risks. Finally, a quality inspection database is established to record the density and flatness data of each area to provide a reference for subsequent construction. The purpose of this step is to ensure that the backfill quality meets the design requirements through scientific inspection methods and to promptly detect and address quality defects.

[0057] The specific implementation method of step S09 is to conduct long-term performance monitoring to ensure the stability of the backfill. First, after the backfill is completed, standard samples are collected and subjected to a 28-day unconfined compressive strength test under standard curing conditions. The strength value should be controlled within the range of 0.8 to 1.5 MPa. Then, an automated settlement monitoring system is installed, including precision leveling points, displacement sensors, and data collectors, to continuously monitor the backfill area. Then, time series analysis methods are used to process the monitoring data and establish a settlement deformation prediction model to warn areas with cumulative settlement approaching 10 mm. Finite element regression analysis techniques are then used to study the correlation between settlement and strength to verify the rationality of the backfill design. Finally, a complete performance evaluation report is generated, including strength distribution maps, settlement contour maps, and stability evaluation results. The purpose of this step is to verify the backfill effect through long-term monitoring, ensure the long-term stability of the structure, and accumulate empirical data for similar projects.

[0058] Overall, this method for backfilling narrow fertilizer troughs with limited working surfaces using fluidized solidified soil solves key technical challenges in narrow space backfill construction through a systematic approach involving zoning, vertical segmentation, path optimization, cross-networking, multi-branch pumping, jump-casting, intelligent mixing, quality inspection, and long-term monitoring, ensuring backfill quality and structural stability. This method is particularly suitable for backfilling narrow spaces with limited working surfaces, such as underground pipeline corridors, tunnel reinforcement, and foundation pit support, offering significant advantages such as high construction efficiency, good backfill quality, and minimal settlement and deformation.

[0059] The intelligent fluidized solidified soil mixing equipment involved in this invention primarily consists of four major components: a metering system, a mixing system, a monitoring system, and a control system. The metering system utilizes a high-precision electronic scale and electromagnetic flowmeter to precisely measure solid raw materials (soil, curing agent) and liquids (water, admixtures), with an error control range of ±0.5%. The mixing system utilizes a dual-shaft forced mixing device with built-in variable-angle mixing blades. The speed ranges from 0 to 60 rpm, and a programmable logic controller automatically adjusts the speed and mixing time at different stages to ensure mixing uniformity. The monitoring system includes a real-time slump measurement device, a temperature sensor, a moisture content detector, and a viscometer. The real-time slump measurement device uses image recognition technology, capturing the sinking process of fluidized soil with a high-definition camera. Combined with a deep learning algorithm, it automatically calculates the slump height with an accuracy of ±3 mm. The temperature sensor uses a PT100 platinum resistance thermometer with a measurement range of -50°C to 150°C and an accuracy of ±0.1°C. The moisture content detector uses a capacitive principle and has a measurement range of 5% to 40% with an accuracy of ±0.5%. The viscometer uses a rotary design and has a measurement range of 0.1 to 100 Pa·s. The control system consists of an industrial computer and a human-computer interface. It features a built-in fluidized soil performance prediction model, including curing reaction kinetics equations and a rheological properties calculation module. Based on input material parameters and environmental conditions, it automatically calculates the optimal mix ratio, mixing parameters, and pumping parameters, and predicts the initial setting time and hardened strength development curve. The device is also equipped with a wireless data transmission module for data interconnection with on-site testing equipment, automatically adjusting the mix design based on backfill quality inspection results, forming a closed-loop control system. The entire set of equipment is installed on a crawler-type mobile platform to meet the flexible movement requirements of narrow spaces. The control system adopts a three-level safety protection design to ensure stable operation in harsh environments.

[0060] The mathematical model or calculation process involved in the present invention is described in detail below.

[0061] The improved A-star search algorithm involved in step S03 is used for backfill path planning, which is specifically expressed as follows:

[0062] f(n)=g(n)+h(n)+α·c(n);

[0063] Where f(n) is the total evaluation function value of node n; g(n) is the actual cost from the starting point to node n; h(n) is the estimated cost from node n to the end point; c(n) is the spatial constraint metric function at node n; α is the spatial constraint weight coefficient, which ranges from 0.5 to 2.0.

[0064] The parameter acquisition method is:

[0065] g(n) is calculated by accumulating the distances between adjacent nodes on the path, that is, Where d(n i-1 , n i ) represents node n i-1 To node n i The Euclidean distance of h(n) is calculated using the Euclidean distance, that is, Where (x n ,y n , z n ) is the three-dimensional coordinate of node n, (x t ,y t , z t ) is the three-dimensional coordinate of the end point; c(n) is calculated through three-dimensional space analysis, Where V free (n) is the volume of free space where the device can operate at node n, V total (n) is the volume of operating space required for the equipment under ideal conditions.

[0066] The purpose of adding the spatial constraint metric function c(n) is to enable the algorithm to prioritize paths with ample space, avoid confined areas, and reduce the risk of equipment jams. By adjusting the weight coefficient α, the relationship between path length and spatial margin can be balanced. When α is large, the algorithm prefers wide paths, even if they are long. When α is small, the algorithm prioritizes the shortest path, which is suitable for smaller equipment.

[0067] The fluid dynamics equations involved in step S05 include the Bernoulli energy equation, the pipeline resistance equation, the sedimentation stability equation, and the solid phase separation critical equation.

[0068] The Bernoulli energy equation is specifically expressed as follows:

[0069]

[0070] Where P1 and P2 are the pressures at the pump outlet and the end of the branch pipe, respectively, in Pa; v1 and v2 are the flow velocities at the main pipe and the branch pipe, respectively, in m / s; z1 and z2 are the elevations at the pump outlet and the end of the branch pipe, respectively, in m; ρ is the density of the fluidized solidified soil, in kg / m3, usually ranging from 1800 to 2200; g is the acceleration of gravity, which is taken as 9.8 m / s2; h f is the resistance loss along the way, in meters; h m is the local resistance loss, in meters; ΔE is the energy increment per unit mass provided by the pump, in joules / kg.

[0071] The parameter acquisition method is:

[0072] P1 and P2 are obtained by real-time measurement through pressure sensors; v1 and v2 are calculated through flow meters and pipe diameters. Where Q is the volume flow rate, D is the pipe diameter; z1 and z2 are obtained by measuring with a level; ρ is obtained by measuring with the intelligent fluidized solidified soil mixing equipment in step S07; h f Calculated by the pipeline resistance equation; h m According to the local resistance coefficient table and flow velocity calculation, Where ξ is the local resistance coefficient; ΔE is provided by the pump performance curve and is related to pumping power and flow rate.

[0073] The Bernoulli energy equation considers the energy conversion relationships within a multi-branch pumping system. By balancing pressure, position, and velocity energy, it ensures stable flow within each branch pipe. The key principle of this equation is the conservation of energy, meaning that the total energy within the system remains constant, merely transforming between different forms. The inclusion of along-the-line and local resistance loss terms accounts for energy dissipation in actual piping systems, making the calculation results more realistic.

[0074] The pipeline resistance equation is specifically expressed as follows:

[0075]

[0076] Where h f is the resistance loss along the way, in meters; λ is the friction coefficient of the pipeline, dimensionless; L is the length of the pipeline, in meters; D is the inner diameter of the pipeline, in meters; v is the average flow velocity in the pipe, in meters per second; Q is the volume flow rate, in cubic meters per second; g is the acceleration due to gravity, which is taken as 9.8 meters per square second.

[0077] The friction coefficient λ is calculated using the modified Colebrook-White formula:

[0078]

[0079] Where k s is the equivalent roughness of the pipeline, in millimeters, provided by the technical parameter table of the pipe supplier; Re is the Reynolds number, Where μ is the dynamic viscosity of the fluidized solidified soil, in Pascals-seconds; τ0 is the yield stress of the fluidized solidified soil, in Pascals; β is the correction coefficient, ranging from 0.01 to 0.05.

[0080] The parameter acquisition method is:

[0081] L is determined based on the backfill path designed in step S03; D is determined in step S05, with the main pipe diameter being 100 mm and the branch pipe diameter being 75 mm; Q is measured by the pump flow meter; k s Provided by the pipe supplier's technical parameter table; μ is obtained by converting the mixture slump in step S07, and the conversion formula is μ = a·e b·S , where S is the slump value in millimeters, a and b are empirical coefficients, which are 10 and -0.01 respectively; τ0 is obtained by rheometer measurement.

[0082] The pipeline resistance equation is based on the Darcy-Weisbach formula in fluid mechanics. It considers the non-Newtonian properties of fluidized solidified soil and modifies the traditional friction coefficient calculation formula by introducing a yield stress term. This modification accounts for the rheological behavior of fluidized solidified soil at low flow rates, making the calculation results more realistic. This equation accurately calculates pressure loss during pumping, providing a basis for pumping system design.

[0083] The settlement stability equation is specifically expressed as follows:

[0084]

[0085] Where, L max is the maximum pumping distance in meters; v is the average flow velocity in the pipe in meters per second; T crit is the critical dead time, in seconds; ρ s is the solid particle density, in kg / m3; ρ l is the liquid density, in kilograms per cubic meter; d is the representative particle size of suspended particles, usually d 90 , in meters; g is the acceleration due to gravity, which is 9.8 m / s²; μ is the dynamic viscosity of the fluidized solidified soil, in Pascals-seconds; θ is the angle between the pipe and the horizontal plane, in radians.

[0086] The parameter acquisition method is:

[0087] v is calculated by the flow meter and pipe diameter; T crit Determined according to the construction schedule, usually 15 to 30 minutes;s Determined by the pycnometer method, where m s is the mass of solid particles, V s is the volume of solid particles; ρ l Obtained by density meter measurement; d 90 It is measured by a laser particle size analyzer and represents the 90% quantile on the cumulative distribution curve of particle size; μ is obtained by converting the slump of the mixture in step S07; θ is obtained by measuring with a spirit level.

[0088] The sedimentation stability equation is based on Stokes' sedimentation theory and takes into account the equilibrium relationship between the sedimentation velocity of suspended particles in a fluid and the flow velocity. The denominator on the right side of the equation represents the sedimentation velocity of the particles, taking into account the influence of factors such as particle size, density difference, fluid viscosity, and pipe inclination. The numerator v·T crit represents the distance a fluid can travel during the stagnation time. This equation can be used to calculate the maximum pumping distance for fluidized solidified soil without significant stratification under given conditions, providing constraints for backfill path design.

[0089] The critical equation for solid phase separation is specifically expressed as follows:

[0090]

[0091] Where, v crit is the critical velocity, in meters per second; τ0 is the yield stress of the fluidized solidified soil, in Pa; ρ is the density of the fluidized solidified soil, in kilograms per cubic meter; d max is the maximum particle size in meters; g is the acceleration due to gravity, which is 9.8 m / s²; ρ s is the solid particle density, in kg / m3; φ is the solid volume fraction, dimensionless; k1 and k2 are empirical coefficients, which are 1.5 and 1.2 respectively.

[0092] The parameter acquisition method is:

[0093] τ0 is obtained by rheometer measurement; ρ is obtained by intelligent fluidized solidified soil mixing equipment in step S07; d max Determined by the diameter of the screen hole of the drum sieve, usually 10 to 20 mm; ρ s It is measured by the pycnometer method; φ is calculated by the intelligent fluidized solidified soil mixing equipment in step S07, and the calculation formula is: Where V s is the solid phase volume, V total is the total volume of the mixture.

[0094] The critical solid-phase separation equation considers the minimum velocity required to prevent solid particles from settling and clogging when fluidized solidified soil flows through a pipe. The first term in the equation is related to the yield stress of the fluidized solidified soil itself and represents the minimum velocity required to overcome the static state of the fluid. The second term is related to particle settling and considers the effects of maximum particle size, density differences, and solid content on settling velocity. By introducing the 0.3 power of the solid volume fraction, the nonlinear effect of increasing solid content on the critical velocity is reflected. The innovation of this equation lies in its comprehensive consideration of the rheological and particle properties of the fluidized solidified soil, making the calculation results more realistic.

[0095] The curing reaction kinetics equation involved in step S07 is specifically expressed as follows:

[0096]

[0097] Where S(t) is the compressive strength at time t, in MPa; S ∞ is the theoretical maximum compressive strength, in MPa, usually 1.5 to 2.5; k is the reaction rate constant, dimensionless, usually 0.5 to 1.5; t is the curing time, in hours; t0 is the initial delay time, in hours, usually 2 to 4; t r is the reference time, which is 24 hours; n is the time index, dimensionless, usually 0.8 to 1.2; f(T) is the temperature influence function; g(W) is the water content influence function; h(M) is the mineral composition influence function.

[0098] The temperature influence function f(T) adopts the Arrhenius equation:

[0099]

[0100] Where, E a is the apparent activation energy, in joules per mole, usually between 20,000 and 40,000; R is the gas constant, which is 8.314 joules per (mole·Kelvin); T ref is the reference temperature, which is 293 Kelvin; T is the actual ambient temperature in Kelvin, which is recorded by the on-site temperature sensor.

[0101] The moisture content influence function g(W) is expressed as:

[0102]

[0103] Where W is the soil moisture content, dimensionless; W opt is the optimal moisture content, dimensionless, usually 0.2-0.3; α and β are fitting parameters, which are 0.5 and 2.0 respectively.

[0104] The mineral composition influence function h(M) is expressed as:

[0105]

[0106] Where C clay is the clay content, dimensionless; C silt is the silt content, dimensionless; is the calcium carbonate content, dimensionless; γ1, γ2 and γ3 are influence coefficients, which are -0.2, 0.1 and 0.3 respectively.

[0107] The parameter acquisition method is:

[0108] S ∞ Determined by long-term curing test; k and n are obtained by strength development curve fitting; t0 is determined by initial setting time test; E a Determined by the strength development curve at different temperatures; W is measured by intelligent fluidized solidified soil mixing equipment; W opt Determined by a series of strength tests at different moisture contents; C clay 、C silt and Obtained by X-ray diffraction analysis.

[0109] The curing reaction kinetics equation, based on chemical reaction kinetics theory, considers the combined effects of time, temperature, moisture content, and mineral composition on the strength development of fluidized solidified soil. The core of the equation uses the modified Johnson-Mayer-Avrami equation to express the nonlinear growth characteristics of strength over time. The temperature influence function, based on the Arrhenius law, reflects the exponential promotion effect of increasing temperature on the reaction rate. The moisture content influence function takes into account the existence of an optimal moisture content, that is, the relationship in which strength first increases and then decreases with moisture content. The mineral composition influence function considers the positive and negative effects of different mineral components on strength. This equation innovatively integrates multiple influencing factors and can relatively accurately predict the strength development process of fluidized solidified soil, providing a theoretical basis for determining construction intervals.

[0110] Specifically, the principle of the present invention is:

[0111] The core technical principle of this invention lies in transforming the problem of backfilling narrow fertilizer troughs into a systemic solution involving spatial discretization control and precise fluid dynamics regulation. First, a block-segmented design achieves effective discretization of three-dimensional space, breaking down the complex backfill task into controllable units and facilitating the development of differentiated construction strategies tailored to the specific characteristics of each unit. This spatial discretization approach aligns with the engineering principles of complex system decomposition and integration, effectively reducing the complexity and uncertainty of the backfill process.

[0112] Secondly, the present invention applies fluid mechanics principles to design a cross-path network and multi-branch pumping system. The Bernoulli energy equation is used to calculate the flow velocity distribution in the primary and secondary backfill channels. The pipeline resistance equation determines the optimal pumping pressure, the sedimentation stability equation assesses the risk of stratification, and the solid phase separation criticality equation prevents pipeline blockage. The application of this series of fluid mechanics equations makes the flow behavior of fluidized solidified soil in complex pipe networks predictable and controllable, ensuring uniform distribution of the material in confined spaces.

[0113] Third, this invention incorporates curing reaction kinetics into construction process control. By establishing a quantitative relationship between factors such as curing agent dosage, soil moisture content, and ambient temperature, and initial setting time and hardened strength, it enables precise prediction of material property development. This principle underpins the scientific implementation of the jump-cast method, keeping material strength differences between adjacent sections within a reasonable range and avoiding the risk of overall settlement associated with traditional continuous backfilling.

[0114] Finally, this invention integrates the technical principles of spatial discretization, fluid dynamics control, and reaction kinetics prediction to form a complete control system for fluidized solidified soil backfill in narrow fertilizer troughs. This systematic solution uses theoretical calculations to guide practical operations, transforming empirical construction into a quantifiable and predictable scientific process, thereby achieving precise control of the fluidized solidified soil backfill quality within the confined conditions of narrow fertilizer troughs.

[0115] A specific embodiment 1 of the present invention is provided below. The specific implementation of each step in this embodiment 1 is described in detail as follows.

[0116] The specific implementation method of step S01 is to scientifically divide the work area according to the geometric characteristics. First, the total station is used to measure the spatial dimensions of the fertilizer trough, including length, width and depth, to obtain precise geometric parameters; then, based on the spatial complexity clustering algorithm, the backfill area is divided into multiple interconnected sub-blocks. The sub-block length is controlled within the range of 8 to 10 meters to ensure that each sub-block can complete backfilling in a single operation; at the same time, the construction area subdivision technology is used to reserve a 0.5-meter-wide transition zone between adjacent sub-blocks. The transition zone is used to alleviate boundary stress concentration and serve as a structural deformation buffer; finally, the sub-block layout plan is drawn into a construction guidance diagram through a computer-aided design system, and the sub-block number, size parameters and construction sequence are marked. The spatial complexity clustering algorithm adopts an improved K-means clustering method, taking spatial geometric features as the clustering basis, and the clustering objective function is: Where J is the clustering objective function; k is the number of partition blocks; C i is the i-th partition block; x is a point in space; μ i is the center point of the i-th partition block; λ is the weight coefficient, ranging from 0.1 to 0.5; is the spatial complexity index of the i-th partition, which is related to the spatial width variation, height difference, and obstacle distribution. The purpose of this step is to solve the problem of limited operation of large equipment in narrow spaces by rationally dividing the construction units, thus creating an orderly and controllable working environment for subsequent backfill operations.

[0117] The specific implementation method of step S02 is to use a vertical layering strategy to accurately control the backfill of the sub-blocks. First, use a level to measure the base elevation of each sub-block to determine the starting elevation of the first layer of backfill; then, according to the layered backfill theory, the vertical backfill height is evenly divided into multiple 1-meter thick backfill sections, and each backfill section is numbered with a unique identifier; then, using digital twin technology, a virtual backfill model is established in the 3D modeling software, and the backfill section information is mapped to the virtual model; then, according to the differences in geological conditions of each backfill section, differentiated backfill parameters are set to ensure consistent backfill quality for each layer; finally, a site schematic is generated, and the backfill section number, elevation, and backfill sequence are marked using color coding. The vertical layering method uses a highly uniform segmentation method, but is optimized in combination with geological conditions. The layer thickness is determined by the function H. i =H base ·(1+δ i ) is determined; where H i is the thickness of the i-th backfill section, in meters; H base is the reference thickness, which is 1 meter; δ i The thickness adjustment coefficient ranges from -0.1 to 0.1 and is determined according to geological conditions. The purpose of this step is to avoid the problem of overpressure at the bottom or lack of solidity at the top caused by a large backfill layer at one time through vertical segmentation, and to achieve uniform and controllable backfill quality in each layer.

[0118] The specific implementation method of step S03 is to apply the path planning algorithm to design the optimal route for backfilling operations. First, three-dimensional laser scanning technology is used to obtain the precise geometric model of the fertilizer tank space and identify the spatial restriction points and obstacle positions; then the improved A-star search algorithm is used to calculate the optimal backfilling path from the starting point to the end point, and the spatial narrowness, obstacle distribution and equipment operating radius are used as path cost function parameters; then the backfill reverse flow principle is applied to determine the construction sequence of backfilling from the farthest end or the deepest end to avoid subsequent backfilling operations from interfering with the completed area; then the feasibility of the path is verified through simulation to ensure that the equipment can successfully complete the backfilling operation in a narrow space; finally, a one-way flow backfill channel navigation map is generated to clearly mark the equipment entry route and personnel evacuation channel. The evaluation function of the improved A-star search algorithm is: f(n) = g(n) + h(n) + α·c(n); where f(n) is the total evaluation function value of node n; g(n) is the actual cost from the starting point to node n; h(n) is the estimated cost from node n to the end point; c(n) is the spatially restricted metric function at node n; α is the spatially restricted weight coefficient, ranging from 0.5 to 2.0. Among them, g(n) is calculated by accumulating the distances between adjacent nodes on the path, that is, Where d(n i-1 , n i ) represents node n i-1 To node n i The Euclidean distance of h(n) is calculated using the Euclidean distance, that is, Where (x n ,y n , z n ) is the three-dimensional coordinate of node n, (x t ,y t , z t ) is the three-dimensional coordinate of the end point; c(n) is calculated through three-dimensional space analysis, Where V free (n) is the volume of free space where the device can operate at node n, V total (n) is the ideal operating space required for the equipment. This step aims to address the limited operation of backfill equipment in narrow manure troughs and ensure a safe and efficient construction process through optimal path planning.

[0119] The specific implementation method of step S04 is to construct a cross-network backfill pipe system. First, computational fluid dynamics software is used to analyze the flow characteristics of the fluidized solidified soil in the narrow fertilizer trough to identify potential dead corner areas. Then, a grid division algorithm is used to divide the backfill area into a grid structure where the main backfill channel and the secondary backfill channel intersect. The spacing between the main backfill channels does not exceed 5 meters, and the spacing between the secondary backfill channels does not exceed 3 meters. Then, the pressure gradient distribution principle is used to design a pressure balancing device at the intersection node of the main and secondary backfill channels to ensure that the flow of each branch pipeline is balanced. Subsequently, the pipeline layout is optimized through the pipe network hydraulic calculation model, and the intersection angle of the main and secondary backfill channels is adjusted within the range of 60° to 90° to reduce flow resistance. Finally, a pulse flow control system is configured to ensure that the grid-like flow route covers the entire backfill area through periodic flow regulation. The grid division algorithm uses adaptive grid technology, and the grid node distribution is determined by the function D(x, y) = D0·e -β·d(x，y) Determine; where D(x, y) is the grid density at coordinate (x, y); D0 is the baseline grid density; β is the attenuation coefficient, ranging from 0.1 to 0.5; and d(x, y) is the distance from coordinate (x, y) to the nearest dead-end area. The purpose of this step is to address the uneven distribution of fluidized solidified soil in narrow spaces, ensure that dead-end areas are fully filled, and improve backfill quality.

[0120] The specific implementation method of step S05 is to design a multi-branch coordinated pumping backfill system. First, the topology of the pumping system is determined based on the complexity analysis of the backfill area, and the number of main branches required is calculated. Then, the pipe network optimization algorithm is used to design the connection method between the main pipe and the branch pipe. The diameter of the main pipe is set to 100 mm, the diameter of the branch pipe is 75 mm, and the length difference of each branch pipe is controlled within 5 meters. Then, the fluid dynamics equation group is applied to calculate the optimal pumping parameters, including flow rate, pressure and flow rate, where the flow rate of the main backfill channel is controlled at 0.8-1.2 m / s, the flow rate of the secondary backfill channel is controlled at 0.5-0.8 m / s, and the pumping pressure is maintained in the range of 1.5-2.0 MPa. Subsequently, the feedback control system is used to monitor the changes in pipeline pressure and flow rate in real time. When the pressure exceeds 2.0 MPa, the pumping rate is automatically adjusted. Finally, a critical flow rate alarm mechanism is set. When the pipeline flow rate is lower than the critical value of 0.3 m / s, the pipeline cleaning program is triggered to prevent blockage. The fluid dynamics equation group includes the Bernoulli energy equation: Where P1 and P2 are the pressures at the pump outlet and the end of the branch pipe, respectively, in Pa; v1 and v2 are the flow velocities at the main pipe and the branch pipe, respectively, in m / s; z1 and z2 are the elevations at the pump outlet and the end of the branch pipe, respectively, in m; ρ is the density of the fluidized solidified soil, in kg / m3, usually ranging from 1800 to 2200; g is the acceleration of gravity, which is taken as 9.8 m / s2; h f is the resistance loss along the way, in meters; h mis the local resistance loss, in meters; ΔE is the energy increment per unit mass provided by the pump, in joules / kilogram. Pipeline resistance equation: Where h f is the resistance loss along the way, in meters; λ is the friction coefficient of the pipeline, dimensionless; L is the length of the pipeline, in meters; D is the inner diameter of the pipeline, in meters; v is the average flow velocity in the pipeline, in meters per second; Q is the volume flow rate, in cubic meters per second; g is the acceleration due to gravity, which is taken as 9.8 meters per square second. The friction coefficient λ is calculated using the modified Colebrook-White formula: Where k s is the equivalent roughness of the pipeline, in millimeters, provided by the technical parameter table of the pipe supplier; Re is the Reynolds number, Where μ is the dynamic viscosity of the fluidized solidified soil, in Pa·s; τ0 is the yield stress of the fluidized solidified soil, in Pa; β is the correction coefficient, ranging from 0.01 to 0.05. Settlement stability equation: Where, L max is the maximum pumping distance in meters; v is the average flow velocity in the pipe in meters per second; T crit is the critical dead time, in seconds; ρ s is the solid particle density, in kg / m3; ρ l is the liquid density, in kilograms per cubic meter; d is the representative particle size of suspended particles, usually d 90 , in meters; g is the acceleration due to gravity, which is 9.8 m / s²; μ is the dynamic viscosity of the fluidized solidified soil, in Pa·s; θ is the angle between the pipe and the horizontal plane, in radians. The critical equation for solid phase separation is: Where, v crit is the critical velocity, in meters per second; τ0 is the yield stress of the fluidized solidified soil, in Pa; ρ is the density of the fluidized solidified soil, in kilograms per cubic meter; d max is the maximum particle size in meters; g is the acceleration due to gravity, which is 9.8 m / s²; ρ s is the solid particle density, in kilograms per cubic meter; φ is the dimensionless solid volume fraction; k1 and k2 are empirical coefficients, taking values of 1.5 and 1.2, respectively. This step aims to address the issue of low backfill efficiency in complex fertilizer tank areas by improving construction efficiency and ensuring pumping safety through multi-branch coordinated pumping.

[0121] The specific implementation method of step S06 is to implement a jump-type backfill strategy to control settlement and deformation. First, the initial setting time of the fluidized solidified soil is calculated based on the solidification reaction kinetic equation to determine the construction interval, which is usually within the range of 2 to 4 hours; then, a non-continuous pouring technology is used to backfill the blocks in an alternating order of 1-3-5-7 and 2-4-6-8 to avoid pouring adjacent areas at the same time; then, non-destructive testing technology is used to monitor the strength development of the completed blocks to ensure that the strength difference of the materials in adjacent blocks does not exceed 0.2 MPa; then, the finite element analysis method is applied to predict the stress distribution and deformation trend of the overall backfill area, and the backfill plan of the subsequent blocks is dynamically adjusted according to the analysis results; finally, a backfill quality control feedback system is established to guide the jump-type pouring process through real-time strength data. The order arrangement of the jump-type pouring is based on the stress distribution optimization algorithm, using a two-dimensional array S ij Indicates the pouring order of the partition block in row i and column j, satisfying the condition |S ij -S i，j±1 |≥N gap And|S ij -S i±1，j |≥N gap Where S ij N is the casting sequence number of the partition block; gap is the sequence interval threshold, ranging from 2 to 4. The finite element analysis uses the elastic-plastic constitutive model to calculate the settlement deformation, and the displacement field u(x, y, z) and the stress field σ(x, y, z) satisfy the equilibrium equation Where, is the divergence operator; σ is the stress tensor; and f is the volume force vector. The purpose of this step is to reduce the overall settlement risk caused by large-scale backfilling and improve the stability of the backfill structure by staggering the construction sequence.

[0122] The specific implementation method of step S07 is to use intelligent mixing technology to control the quality of fluidized solidified soil. First, configure intelligent fluidized solidified soil mixing equipment with real-time monitoring function, including automatic batching system, precise metering device and quality monitoring module; then establish slump prediction model through neural network algorithm, and predict slump of mixture according to raw material characteristics, ambient temperature and mixing parameters; then use closed-loop control technology to adjust water-cement ratio and mixing time in real time, and accurately control slump within the range of 180-240 mm; then predict strength development curve based on curing reaction kinetic equation to ensure that the strength of mixture can reach 0.3 MPa or above within 12 hours; finally, calculate the bearing capacity of backfill by boundary element method to verify the construction conditions of the next day. Curing reaction kinetic equation: Where S(t) is the compressive strength at time t, in MPa; S ∞is the theoretical maximum compressive strength, in MPa, usually 1.5 to 2.5; k is the reaction rate constant, dimensionless, usually 0.5 to 1.5; t is the curing time, in hours; t0 is the initial delay time, in hours, usually 2 to 4; t r is the reference time, which is 24 hours; n is the time index, dimensionless, usually 0.8 to 1.2; f(T) is the temperature influence function; g(W) is the water content influence function; h(M) is the mineral composition influence function. Temperature influence function: Where, E a is the apparent activation energy, in joules per mole, usually between 20,000 and 40,000; R is the gas constant, which is 8.314 joules per (mole·Kelvin); T ref The reference temperature is 293 Kelvin; T is the actual ambient temperature in Kelvin, recorded by the on-site temperature sensor. Moisture content influence function: Where W is the soil moisture content, dimensionless; W opt is the optimal moisture content, dimensionless, usually 0.2-0.3; α and β are fitting parameters, 0.5 and 2.0 respectively. Mineral composition influence function: Where C clay is the clay content, dimensionless; C silt is the silt content, dimensionless; is the calcium carbonate content, dimensionless; γ1, γ2, and γ3 are influence coefficients, -0.2, 0.1, and 0.3, respectively. The purpose of this step is to ensure the stability of the fluidized solidified soil quality through intelligent mixing technology, creating conditions for continuous construction.

[0123] The specific implementation method of step S08 is to perform systematic quality inspection and evaluate the backfill effect. First, a penetrating electronic density detector is used to grid the backfill area, with no less than 3 inspection points set for every 100 square meters; then a stratified sampling inspection method is used to conduct a density test on each backfill section, and the qualified standard is a density of not less than 95%; then a three-dimensional laser scanning technology is used to fully cover the backfill surface to generate a high-precision surface model, evaluate the flatness deviation, and control it within 10 mm; then the statistical process control method is applied to analyze the inspection data and identify potential quality risk areas; finally, a quality inspection database is established to record the density and flatness data of each area to provide a reference for subsequent construction. The statistical process control method uses control chart technology to monitor quality data, and the control limit calculation formula is: UCL = μ + kσ, LCL = μ - kσ; where UCL is the upper control limit; LCL is the lower control limit; μ is the mean of the quality characteristic; σ is the standard deviation of the quality characteristic; k is the control coefficient, which is 3. Flatness evaluation is calculated using the root mean square deviation: Where RMSD is the root mean square deviation, in millimeters; Z i is the measured elevation of point i; Z design is the design elevation; n is the number of measurement points. The purpose of this step is to ensure that the backfill quality meets the design requirements through scientific testing methods and to promptly detect and address quality defects.

[0124] The specific implementation of step S09 involves conducting long-term performance monitoring to ensure backfill stability. First, after backfilling is completed, standard samples are collected and subjected to a 28-day unconfined compressive strength test under standard curing conditions. The strength value should be controlled within the range of 0.8 to 1.5 MPa. An automated settlement monitoring system, including precision leveling points, displacement sensors, and data collectors, is then installed to continuously monitor the backfill area. Time series analysis is then used to process the monitoring data and establish a settlement deformation prediction model to provide early warning for areas with cumulative settlement approaching 10 mm. Finite element regression analysis is then used to study the correlation between settlement and strength to verify the rationality of the backfill design. Finally, a complete performance evaluation report is generated, including a strength distribution diagram, settlement contour maps, and stability evaluation results. The time series analysis method uses the autoregressive moving average (ARMA) model, and the settlement prediction function is: S(t) = φ1S(t-1) + φ2S(t-2) + ... + φ p S(tp)+ε t +θ1ε t-1 +θ2ε t-2 +...+θ q ε t-q ; where S(t) is the settlement at time t; φ1, φ2, ..., φ p are the autoregressive coefficients; θ1, θ2, ..., θ q is the moving average coefficient; ε t is the random error term; p is the autoregressive order; q is the moving average order. The strength and settlement relationship model uses the nonlinear regression equation: S max =a·(S strength ) b +c; where S max is the maximum settlement, in millimeters; S strength is the 28-day unconfined compressive strength in MPa; a, b, and c are regression coefficients obtained by fitting experimental data. The purpose of this step is to verify the backfill effect through long-term monitoring, ensure the long-term stability of the structure, and accumulate empirical data for similar projects.

[0125] Optional, such as Figure 2The intelligent fluidized solidified soil mixing equipment shown in this embodiment was developed for narrow fertilizer trough construction environments with limited working surfaces. Its compact overall structure, high functional integration, and high degree of automation enable intelligent preparation and quality control of fluidized solidified soil throughout the entire process. The equipment primarily consists of five major components: a metering system, a mixing system, a monitoring system, a control system, and a mobile platform. These systems share information and collaborate via a data bus.

[0126] The metering system consists of multiple high-precision metering devices, including solid and liquid metering units. The solid metering unit utilizes a tension-type electronic scale with a maximum capacity of 2,000 kg and a minimum scale resolution of 0.1 kg. It meets OIML Class III accuracy and features an automatic compensation algorithm to eliminate vibration interference. The liquid metering unit utilizes a dual metering system combining a Coriolis mass flowmeter and an electromagnetic flowmeter. The former is used for high-precision additive metering with an accuracy of ±0.1%, while the latter is used for high-flow moisture metering with an accuracy of ±0.5%. The metering system is dust- and moisture-resistant to withstand the complex environment of the project site, and incorporates self-diagnosis to ensure metering reliability.

[0127] like Figure 3 As shown, the mixing system uses a dual-shaft forced mixing device with a mixing drum volume of 1.5 cubic meters. It is equipped with variable-angle mixing blades made of special alloy. The blade angle can be automatically adjusted within the range of 0 to 45 degrees according to the viscosity of the mixture to optimize mixing efficiency. The mixing motor uses variable frequency speed regulation technology, with a power of 22 kilowatts, a speed range of 0 to 60 rpm, and a torque of 1200 Nm, which can adapt to the mixing needs of fluidized solidified soils with different viscosities. The mixing system is designed with a multi-stage mixing program, including a dry mixing stage (low speed, high torque), a wet mixing stage (medium speed, medium torque), and a homogenization stage (high speed, low torque). The time and speed parameters of each stage can be automatically optimized according to the material properties through the control system. The inner wall of the mixing drum uses a nano-level polyurethane anti-stick coating to reduce material adhesion and mixing dead corners, thereby improving mixing uniformity and equipment cleaning efficiency.

[0128] like Figure 4As shown, the monitoring system is the core sensing unit of the equipment and includes multiple real-time monitoring devices. The real-time slump measurement device, based on machine vision technology, consists of a high-definition industrial camera (resolution 2400×1800 pixels), an LED ring light source, and an image processing unit. By capturing the sinking process of a fluidized solidified soil sample in a standard slump cone and integrating a deep learning algorithm, it automatically calculates the slump height. The measurement range is 50–300 mm, with an accuracy of ±3 mm and a measurement cycle of less than 30 seconds. Temperature monitoring utilizes an array of PT100 platinum resistance sensors, with eight measurement points positioned at different locations within the mixing drum. The measurement range is -50–150°C with an accuracy of ±0.1°C, enabling real-time monitoring of the temperature distribution during the mixing process. The moisture content detector, based on the microwave capacitance method, has a measurement range of 5%–40% and an accuracy of ±0.5%, enabling continuous monitoring of moisture content changes during the fluidized solidified soil preparation process. Viscosity measurement utilizes a rotational rheometer with a measurement range of 0.1–100 Pa·s and temperature compensation, enabling the generation of viscosity-temperature curves for fluidized solidified soils. In addition, the monitoring system also includes a pH sensor (measuring range 2 to 14, accuracy ±0.05) and a conductivity sensor (measuring range 0 to 100 millisiemens / cm) to monitor the activity of the curing agent and the ion concentration.

[0129] like Figure 5 As shown, the control system consists of an industrial computer, a field programmable controller (PLC), and a human-machine interface, utilizing a hierarchical distributed control architecture. The bottom layer is the real-time control layer, responsible for precise control of each actuator and process data collection; the middle layer is the process management layer, responsible for process flow control and exception handling; and the top layer is the decision-making optimization layer, which runs algorithms for predicting fluidized solidified soil properties and optimizing process parameters. The control system incorporates multiple expert system models, including a curing reaction kinetics model, a rheological property prediction model, and a mix ratio optimization model. The curing reaction kinetics model uses the existing Arrhenius equation, taking as input parameters such as curing agent type, dosage, and ambient temperature, and outputs initial setting time and strength development curves. The rheological property prediction model, based on the existing Bingham fluid theory and combined with measured slump data, predicts the flow characteristics of fluidized solidified soil under different temperature and pressure conditions. The mix ratio optimization model utilizes the existing response surface methodology to automatically calculate the optimal mix parameters based on target performance indicators. The equipment is equipped with a 10.4-inch explosion-proof touchscreen, supporting intuitive human-computer interaction and providing a remote wireless monitoring interface, enabling remote monitoring and data sharing via the Industrial Internet of Things (IIoT) platform. The control system adopts a three-level redundancy design and a fail-safe mechanism to ensure stable and reliable operation in complex environments.

[0130] The entire equipment is mounted on a crawler-type mobile platform, weighing less than 5 tons and measuring 3.5 meters x 1.8 meters x 2.1 meters. It can be flexibly moved in narrow manure troughs. The platform is driven by electric tracks, with a maximum speed of 5 km / h and a gradeability of at least 20 degrees. It is equipped with an adaptive hydraulic outrigger system to ensure stable operation on uneven surfaces. The equipment can be powered by either a three-phase 380V power supply or a 48V DC battery, adapting to different construction environments. The entire machine has an IP65 protection rating, making it suitable for harsh working conditions such as high humidity and high dust levels.

[0131] The equipment also features data logging and analysis capabilities, automatically recording the mix ratio parameters, preparation process parameters, and quality inspection data for each batch of fluidized solidified soil, establishing a comprehensive quality traceability system. Through wireless data transmission, it communicates with on-site testing equipment, receiving quality inspection results such as backfill area density and surface smoothness, enabling closed-loop quality control. The mix ratio and process parameters of subsequent batches are automatically adjusted based on the backfill results, continuously optimizing the performance of the fluidized solidified soil.

[0132] Overall, the method for backfilling narrow fertilizer troughs with limited working surfaces in this embodiment addresses key technical challenges in narrow space backfill construction, ensuring backfill quality and structural stability, through systematic steps such as zoning and block division, vertical segmentation, path optimization, cross-networking, multi-branch pumping, jump pouring, intelligent mixing, quality inspection, and long-term monitoring. From the perspective of algorithms and principles, this method integrates clustering algorithms, search algorithms, fluid mechanics equations, curing reaction kinetics, finite element analysis, statistical process control, and time series analysis to construct a complete narrow space backfill technology system. The parameters and thresholds in this method are determined based on engineering practice and theoretical analysis. These include block lengths of 8 to 10 meters, pipe diameters of 100 mm and 75 mm, flow rates between 0.8 and 1.2 m / s, pumping pressures between 1.5 and 2.0 MPa, slump between 180 and 240 mm, compaction of no less than 95%, surface flatness deviations of no more than 10 mm, and strength values between 0.8 and 1.5 MPa. These parameters and thresholds are designed to balance construction operability and backfill quality, making this method widely applicable and reliable for backfilling in narrow spaces with limited access, such as underground pipeline corridors, tunnel reinforcement, and foundation pit support.

[0133] To better understand and implement the present invention, Example 2 of a specific application scenario of the present invention is provided below: A certain tunnel is a single-track tunnel with an inner width of only 3.2 meters and a clear height of 4.5 meters. There are obstacles such as pipelines and support beams in some areas. Backfilling requires the use of fluidized solidified soil, but due to the severe limitation of the working surface and the difficulty of equipment access and operation, conventional backfilling methods are difficult to meet the requirements. The researchers decided to adopt a construction method of backfilling fluidized solidified soil in a narrow fertilizer trough with a limited working surface.

[0134] First, based on the measured data, the entire tunnel backfill area was divided into nine blocks. Each block was approximately 9.2 meters long, with a 0.5-meter transition zone reserved between adjacent blocks. Spatial characteristics were analyzed using a spatial complexity clustering algorithm, with a weight coefficient λ of 0.35, as shown in Table 1:

[0135] Table 1 Backfill area partition table

[0136]

[0137]

[0138] Then, according to the vertical stratification strategy, each sub-block is divided vertically into multiple backfill sections, with a base thickness of 1 meter and an adjustment coefficient ranging from -0.05 to 0.08 based on geological conditions. Taking sub-block 1 as an example, the vertical stratification is shown in Table 2:

[0139] Table 2 Vertical hierarchical division table of partition block 1

[0140] Backfill segment number Starting elevation (m) End elevation (m) Thickness (m) Adjustment factor 1-1 0.0 1.05 1.05 0.05 1-2 1.05 2.08 1.03 0.03 1-3 2.08 3.05 0.97 -0.03 1-4 3.05 4.02 0.97 -0.03 1-5 4.02 5.02 1.00 0.00

[0141] Next, we used the improved A-star search algorithm to design the optimal backfill path. We selected a spatially restricted weight coefficient α of 1.8, taking into account both path length and spatial openness. The optimized path parameters are shown in Table 3:

[0142] Table 3 Backfill path optimization results

[0143]

[0144] A cross-network backfill pipe system was constructed in a narrow tunnel, with primary backfill channels spaced 4.5 meters apart, secondary backfill channels spaced 2.8 meters apart, and a 75° intersection angle. The grid density was adaptively adjusted, with a baseline grid density D0 of 0.25 and an attenuation coefficient β of 0.3.

[0145] A multi-branch coordinated pumping backfill system was designed, with a main pipe diameter of 100 mm and a branch pipe diameter of 75 mm. The length difference of each branch pipe was controlled within 3.8 meters. The pumping parameters were calculated based on the fluid dynamics equations. The fluidized solidified soil parameters are shown in Table 4:

[0146] Table 4 Parameters of fluidized solidified soil

[0147] Parameter name Parameter value Parameter name Parameter value <![CDATA[Density (kg / m 3 )]]> 1950 Viscosity (Pa·s) 1.85 Yield stress (Pa) 95 Solid phase volume fraction 0.32 <![CDATA[Solid density (kg / m 3 )]]> 2650 <![CDATA[Liquid density (kg / m 3 )]]> 1050 <![CDATA[d 90 (mm)]]> 3.5 <![CDATA[d max (mm)]]> 15 Critical flow velocity (m / s) 0.38 Critical stagnation time (min) 22

[0148] Calculation results show that the flow rate in the primary backfill channel should be controlled between 0.95 and 1.15 m / s, and the flow rate in the secondary backfill channel should be controlled between 0.62 and 0.75 m / s, with a pumping pressure of 1.75 MPa. The maximum pumping distance is 42 meters, requiring the installation of a booster pump in between.

[0149] A skip-casting strategy was used to control settlement and deformation, with backfill being placed in alternating sequences of 1-3-5-7-9 and 2-4-6-8. The gap threshold N (gap) was set to 3 to ensure sufficient time between pours of adjacent blocks. Finite element analysis was used to predict stress distribution, and the maximum predicted settlement was 7.2 mm.

[0150] The fluidized solidified soil uses intelligent mixing technology to control quality. The values of the parameters of the solidification reaction kinetic equation are shown in Table 5:

[0151] Table 5 Parameters of curing reaction kinetic equation

[0152]

[0153] The calculation results show that the initial setting time is 3.2 hours, the 12-hour strength is 0.42 MPa, and the 28-day strength prediction value is 1.25 MPa.

[0154] Quality control of the completed backfill area revealed an average density of 97.3% and a root mean square deviation of 6.8 mm for surface flatness. A quality control chart was established using a control factor k of 3 and an upper control limit of three times the standard deviation.

[0155] Long-term performance monitoring employed a time series ARMA(2,1) model with autoregressive coefficients φ1 = 0.82, φ2 = 0.15, and a moving average coefficient θ1 = 0.25. The regression coefficients for the strength-settlement relationship model were a = 12.5, b = -0.75, and c = 2.8. The final cumulative settlement was 8.3 mm, and the 28-day unconfined compressive strength was 1.32 MPa.

[0156] Traditional narrow space backfill construction mainly adopts segmented filling method or grouting method, which has problems such as uneven backfill, difficult to control quality, and large settlement differences. The segmented filling method requires multiple entries and exits of the narrow space, which has low construction efficiency and high safety risks; the grouting method easily creates gaps and dead corners, and the density is difficult to ensure. The present invention adopts a fluidized solidified soil backfill construction method for narrow fertilizer troughs with limited working surfaces. Compared with traditional means, it has the following improvements: First, through block division and spatial complexity clustering algorithm, the construction units are scientifically divided, which improves the efficiency of narrow space construction organization; second, by optimizing the backfill path through the improved A-star algorithm, the problem of limited equipment operation is solved; third, a cross-network backfill pipeline system and a multi-branch pumping system are used to ensure uniform distribution of fluidized solidified soil and reduce dead corners; fourth, the jump-type pouring method and the curing reaction kinetic equation are applied to control the strength difference between adjacent areas and reduce the risk of settlement; fifth, the intelligent mixing technology and systematic quality detection method are used to significantly improve the stability and uniformity of backfill quality. Verified in actual projects, this method improves construction efficiency by 35%, reduces settlement by 42%, increases compaction by 5.2%, and improves strength uniformity by 28% compared to traditional methods. These advances significantly address the technical challenges of backfilling fluidized solidified soil in narrow fertilizer troughs, providing reliable technical support for similar projects.

[0157] It should be noted that the variables involved in the present invention are explained in detail as shown in Tables 6 and 7 below.

[0158] Table 6 Variable Explanation Table (Part 1)

[0159]

[0160]

[0161] Table 7 Variable Explanation Table (Part 2)

[0162]

[0163] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be covered by the scope of protection of the present invention.

Claims

1. A construction method for backfilling fluidized solidified soil in a narrow fertilizer trough with a limited working surface, characterized in that: include: The overall backfill area is divided into several interconnected sub-blocks, each of which is no longer than 10 meters, and a 0.5-meter transition zone is reserved between the sub-blocks; each sub-block is divided into multiple backfill sections with a thickness of 1 meter; the optimal backfill path is designed according to the degree of space limitation of the fertilizer trough; a grid-like flow route is formed by the intersection of the main backfill channel and the secondary backfill channel; a multi-branch pumping system is used for complex fertilizer trough areas; pouring is carried out in an alternating sequence of 1-3-5-7 and 2-4-6-8; the slump of the mixture is monitored in real time; the backfill quality is tested with a penetrating electronic density tester; a 28-day unconfined compressive strength test and settlement deformation monitoring are carried out; the flow velocity of the main backfill channel and the secondary backfill channel is calculated by applying a group of fluid dynamics equations, and the critical flow velocity is determined to prevent pipeline blockage.

2. The narrow fertilizer trough fluidized solidified soil backfill construction method according to claim 1 is characterized in that: The said dividing the whole backfill area into several sub-blocks means dividing the working area according to the spatial size of the fertilizer trough, dividing the whole backfill area into several interconnected sub-blocks, each sub-block is no longer than 10 meters, and a 0.5-meter transition zone is reserved between the sub-blocks.

3. The narrow fertilizer trough fluidized solidified soil backfill construction method according to claim 2 is characterized in that: The said dividing each partition block into multiple backfill sections according to the thickness of 1 meter means vertically segmenting each partition block according to the depth, dividing it into multiple backfill sections according to the thickness of 1 meter, and determining the first layer backfill elevation. Each backfill section needs to be numbered and marked on the site schematic.

4. The narrow fertilizer trough fluidized solidified soil backfill construction method according to claim 3 is characterized in that: The design of the optimal backfill path based on the limited degree of space in the fertilizer tank means starting backfilling from the farthest end or deepest point to ensure unidirectional flow in the backfill channel and avoid interference between operating equipment and personnel.

5. The narrow fertilizer trough fluidized solidified soil backfill construction method according to claim 4 is characterized in that: The grid-like flow route formed by the intersection of the main backfill channel and the secondary backfill channel refers to setting up a cross-path network in a narrow fertilizer trough, and forming a grid-like flow route by the intersection of the main backfill channel and the secondary backfill channel to ensure uniform distribution of the fluidized solidified soil.

6. The narrow fertilizer trough fluidized solidified soil backfill construction method according to claim 5 is characterized in that: The multi-branch pumping system used in complex fertilizer trough areas means that the main line has a diameter of 100 mm, the branch line has a diameter of 75 mm, the length difference between each branch line does not exceed 5 meters, and the pumping pressure is controlled within 2 MPa.

7. The narrow fertilizer trough fluidized solidified soil backfill construction method according to claim 6 is characterized in that: The pouring in the alternating order of 1-3-5-7 and 2-4-6-8 refers to the use of a jump pouring method during the backfill process, and the discontinuous pouring of adjacent partition blocks. The jump pouring method is a construction method for discontinuously pouring adjacent partition blocks. Through intermittent construction, it is ensured that the initial setting area and the newly poured area are staggered, thereby reducing the overall settlement risk; that is, pouring in the alternating order of 1-3-5-7 and 2-4-6-8 ensures that the difference in material strength of adjacent partition blocks does not exceed 0.2 MPa.

8. The narrow fertilizer trough fluidized solidified soil backfill construction method according to claim 7 is characterized in that: The zoning blocks divide the overall backfill space into several independent construction units according to the geometric shape and equipment operating radius, so as to facilitate the precise control of the backfill quantity and quality in batches; the backfill sections divide the vertical backfill height into construction units of 1 meter each, so as to avoid excessive stress on the bottom or incomplete filling on the top due to one-time backfilling; the backfill path is the optimal transportation channel for the fluidized solidified soil from the mixing equipment to the target filling area, which needs to avoid obstacles and maximize transportation efficiency.

9. The narrow fertilizer trough fluidized solidified soil backfill construction method according to claim 8, characterized in that: The cross paths are mutually perpendicular or oblique delivery pipe systems arranged in a narrow space, forming a grid-like coverage to ensure that dead corner areas are fully filled.

10. The narrow fertilizer trough backfill construction method according to claim 9, characterized in that: The multiple branches are multiple secondary pipelines extending from the main conveying pipeline, which are used to simultaneously convey fluidized solidified soil to different directions or elevations, thereby improving backfill efficiency.

Images