A method of increasing the height and distance of shotcrete delivery

Abstract

This disclosure provides a method for increasing the conveying height and distance of shotcrete, comprising the following steps: activating the vibrator in the wet shotcrete machine's hopper to expel concrete slurry and enhance lubricity; controlling the quality of the aggregate raw materials, including washing and sieving, to reduce stone powder content and increase the amount of large-diameter aggregate; installing a reducing pipe so that all diameter changes are completed at the wet shotcrete machine outlet, and installing a through pipe such that the steel pipe accounts for more than 80% of the total pipe length, the rubber hose length does not exceed 30m, and using 135° or 150° bends with a bending diameter at least 10 times the pipe diameter at bends; adjusting the air content of the concrete to increase it to more than 10% before conveying and reduce it to 3% to 5% after spraying. Through the solution of this disclosure, efficient long-distance conveying of shotcrete can be achieved under conditions of low slump and small pipe diameter, avoiding sudden pressure increases and pipe blockage.

Description

Technical Field

[0001] This application relates to the field of civil engineering technology, and specifically to a method for increasing the delivery height and distance of shotcrete. Background Technology

[0002] Shotcrete construction technology is widely used in many fields such as building construction, tunnel construction, and mining. It can quickly form a concrete layer with a certain strength and thickness on the base surface, serving multiple functions such as support, waterproofing, and repair. However, in actual construction, when encountering conditions with low slump (60mm~140mm) and small pipe diameter (DN50), and simultaneously requiring efficient long-distance (over 100m) delivery of shotcrete, many challenging problems often arise.

[0003] Low-slump concrete has relatively poor fluidity, and the frictional resistance between its internal aggregates and cementitious materials is relatively high, making it difficult for the concrete to flow smoothly during pipeline transportation. Small-diameter pipelines further restrict the flow space of the concrete, exacerbating the flow resistance. When the transportation distance exceeds 100m, the combined resistance that the concrete needs to overcome within the pipeline, including frictional resistance, gravity, and inertial forces, increases significantly. These factors combine to cause a sharp increase in pressure during transportation. Once the pressure exceeds the pipeline's withstand limit or local changes occur in the internal structure of the concrete, pipe blockage is highly likely.

[0004] Pipe blockage not only interrupts construction, wasting manpower, resources, and time, but can also damage the pipeline, increasing construction costs and safety risks. While some progress has been made in shotcrete delivery technology, there is still no particularly effective solution for the special conditions of low slump, small pipe diameter, and long-distance delivery. Therefore, there is an urgent need for a new technology or method to effectively address the problems of rapid pressure increase and pipe blockage during efficient long-distance (over 100m) delivery of shotcrete under low slump (60mm–140mm) and small pipe diameter (DN50) conditions. This would improve construction efficiency, ensure construction quality and safety, and promote the application and development of shotcrete construction technology in more complex conditions. Summary of the Invention

[0005] In view of this, the present disclosure provides a method for increasing the delivery height and distance of shotcrete, which at least partially solves the problems existing in the prior art.

[0006] A method for increasing the height and distance of shotcrete delivery, comprising the following steps during the concrete delivery process:

[0007] Turn on the vibrator in the wet shotcrete machine hopper to allow concrete slurry to seep out and enhance lubricity;

[0008] Controlling the quality of raw stone materials, including washing and sieving, to reduce stone powder content and increase the number of large-diameter stones;

[0009] Install reducers so that all diameter changes are completed at the outlet of the wet spraying machine in one go. Install through pipes so that steel pipes account for more than 80% of the total pipe length. Rubber hoses should not exceed 30m in length. Use 135° or 150° bends with a bend diameter of at least 10 times the pipe diameter at bends.

[0010] Adjust the air content of the concrete to increase it to over 10% before transportation and reduce it to 3%–5% after spraying; and

[0011] The air content before delivery is adjusted in real time based on the target concrete delivery height H and target delivery distance L.

[0012] According to one embodiment, the step of adjusting the air content before delivery in real time based on the target concrete delivery height H and the target delivery distance L further includes:

[0013] Calculate the initial gas content reference value A_ref based on the target conveying height H and the target conveying distance L;

[0014] The air content is adjusted according to the concrete slump S, where S is in the range of 60mm to 140mm.

[0015] If the target conveying distance L is greater than L_min, the gas content A before conveying is increased to avoid pipe blockage, where L_min represents the reference distance threshold for long-distance conveying;

[0016] The gas content is dynamically adjusted based on the pressure monitoring value P inside the pipeline to maintain pressure stability.

[0017] According to one embodiment, the step of calculating the initial gas content reference value A_ref based on the target conveying height H and the target conveying distance L further includes:

[0018] The basic value of gas content A_base is calculated based on H and L, where A_base is proportional to H and L.

[0019] A_base is corrected based on pipe diameter D and slump S;

[0020] If the slump S is less than S_ref, then the gas content compensation value ΔA_s is increased, where S_ref represents the slump reference value and ΔA_s represents the slump compensation amount.

[0021] The gas content A before transportation is set based on the corrected gas content.

[0022] According to one embodiment, the step of calculating the basic gas content value A_base based on H and L further includes:

[0023] Calculate the pipe resistance coefficient R based on H and L;

[0024] The gas content adjustment factor k is determined based on the drag coefficient R;

[0025] If the drag coefficient R is greater than R_th, then A_base = A_min + k × (R-R_th), where R_th represents the drag coefficient threshold, A_min represents the minimum gas content value, and k represents the gas content adjustment factor.

[0026] A_base is further optimized based on the collapse degree S.

[0027] According to one embodiment, the step of calculating the pipe resistance coefficient R based on H and L further includes:

[0028] The equivalent transport length L_eq is calculated based on H and L, where L_eq = L + c × H, and c represents the height conversion factor.

[0029] The resistance factor f is determined based on the pipe diameter D and the slump S.

[0030] If the equivalent conveying length L_eq is greater than L_eq_max, then R = f × L_eq, where L_eq_max represents the maximum equivalent conveying length threshold.

[0031] The R-value was verified based on real-time monitoring of the pressure gradient.

[0032] According to one embodiment, the step of calculating the equivalent transport length L_eq based on H and L further includes:

[0033] The slope factor m is calculated based on H and L, where m = H / L;

[0034] The weight w of the height effect is adjusted according to the slope factor m;

[0035] If the slope factor m is greater than m_th, then L_eq = L × (1 + w × m), where m_th represents the slope factor threshold and w represents the height influence weight.

[0036] L_eq is calibrated based on concrete rheological parameters.

[0037] According to one embodiment, the method further includes a step of dynamically fine-tuning the gas content based on the pipeline pressure monitoring value P, comprising:

[0038] The pressure change rate dP / dt is calculated based on the pressure monitoring value P.

[0039] Adjust the gas content fine-tuning amount ΔA_p based on dP / dt and distance L;

[0040] If the pressure change rate dP / dt is greater than dP_th, then ΔA_p = k_p × (dP / dt-dP_th), where dP_th represents the pressure change rate threshold and k_p represents the pressure adjustment coefficient.

[0041] The maximum value of ΔA_p is limited by the target distance L.

[0042] According to one embodiment, the step of calculating the pressure change rate dP / dt based on the pressure monitoring value P further includes:

[0043] Fit a pressure trend line based on time-series pressure data;

[0044] Determine dP / dt based on the slope of the trend line;

[0045] If the absolute value of the slope of the pressure trend line is greater than slope_max, then dP / dt = |slope|, where slope_max represents the maximum allowable slope threshold.

[0046] The accuracy of dP / dt calculation is calibrated based on the conveying distance L.

[0047] This disclosure provides a method for increasing the conveying height and distance of shotcrete. During the concrete conveying process, the method includes the following steps: activating the vibrator in the wet shotcrete machine's hopper to expel concrete slurry and enhance lubricity; controlling the quality of the raw aggregate, including washing and sieving, to reduce stone powder content and increase the amount of large-diameter aggregate; setting up a reducing pipe so that all diameter changes are completed at the wet shotcrete machine outlet in one go, setting a through pipe such that the steel pipe accounts for more than 80% of the total pipe length, the rubber hose length does not exceed 30m, and using 135° or 150° bends with a bending diameter at least 10 times the pipe diameter at bends; adjusting the air content of the concrete to increase the air content before conveying to more than 10% and reduce it to 3%–5% after spraying; and adjusting the air content before conveying in real time based on the target concrete conveying height H and target conveying distance L. The solution provided by this disclosure can solve the problem of how to adjust the air content according to the target concrete delivery height H and target delivery distance L to achieve efficient long-distance (over 100m) delivery of shotcrete under low slump (60mm~140mm) and small pipe diameter (DN50) conditions, avoiding sudden pressure increase and pipe blockage. Attached Figure Description

[0048] To more clearly illustrate the technical solutions of the exemplary embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1 A flowchart illustrating a method for increasing the delivery height and distance of shotcrete;

[0050] Figure 2 This is a flowchart showing how to adjust the air content before concrete conveying in real time based on the target conveying height H and target conveying distance L.

[0051] Figure 3 This is a flowchart for calculating the initial gas content reference value A_ref based on the target conveying height H and the target conveying distance L;

[0052] Figure 4 This is a flowchart for calculating the basic gas content value A_base based on H and L;

[0053] Figure 5 This is a flowchart for calculating the pipe resistance coefficient R based on H and L;

[0054] Figure 6 This is a flowchart for calculating the equivalent transport length L_eq based on H and L;

[0055] Figure 7 This is a flowchart for dynamically fine-tuning the gas content based on the pipeline pressure monitoring value P.

[0056] Figure 8 This is a flowchart for calculating the pressure change rate dP / dt based on the pressure monitoring value P. Detailed Implementation

[0057] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0058] The following specific examples illustrate the implementation of this disclosure. Those skilled in the art can easily understand other advantages and effects of this disclosure from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. This disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this disclosure. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0059] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0060] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this disclosure. The drawings only show the components related to this disclosure and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0061] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0062] Next, refer to Figure 1 The present invention describes the specific steps of a method for increasing the delivery height and distance of shotcrete.

[0063] S101: Turn on the vibrator in the wet shotcrete machine hopper to allow concrete slurry to seep out and enhance lubricity;

[0064] S102: Control the quality of raw stone materials, including washing and sieving, to reduce stone powder content and increase the number of large-diameter stones;

[0065] S103: Install a reducing pipe system. All diameter changes are completed at the outlet of the wet spraying machine in one go. Ensure that the main pipe (steel pipe) accounts for more than 80% of the total pipe length, the length of the rubber hose does not exceed 30m, and use 135° or 150° bends with a bending diameter of at least 10 times the pipe diameter at bends.

[0066] S104: Adjust the air content of concrete, increasing it to over 10% before transportation and reducing it to 3%–5% after spraying;

[0067] S105: Adjusts the air content before delivery in real time based on the target concrete delivery height H and target delivery distance L.

[0068] These steps work together to address the challenge of achieving efficient long-distance (over 100m) delivery under conditions of low slump (60mm–140mm) and small pipe diameter (DN50), avoiding sudden pressure increases and pipe blockage. The key is to reduce pipe friction resistance by optimizing air content, thereby ensuring stable concrete fluidity.

[0069] For step S101, the vibrator is turned on in the wet shotcrete machine's hopper to allow concrete slurry to seep out, thus enhancing lubricity. Specifically, before starting the wet shotcrete machine, the operator needs to turn on the vibrator installed at the bottom of the hopper, setting the frequency to medium-high frequency (e.g., 30-50Hz), and vibrate continuously to separate the cement paste and fine aggregate in the concrete and allow them to seep to the surface, forming a lubricating film. This film coats the coarse aggregate during transport, reducing the coefficient of friction with the pipe wall and thus reducing resistance. This step directly addresses the problem of poor concrete fluidity under low slump by enhancing lubricity to prevent pipe blockage. For example, during vibration, the operator needs to monitor the amount of slurry seeping out to ensure uniform slurry coverage and avoid localized drying that could cause blockage.

[0070] More specifically, the vibrator should be turned on throughout the entire process, and the vibration amplitude should be controlled within a small range to avoid concrete segregation. Typically, the amplitude is set to 0.5-1.0 mm and the frequency is 30-50 Hz. This can promote the exudation of slurry inside the concrete, prevent concrete precipitation, and prevent concrete segregation. It also forms a lubricating layer to coat the aggregate and reduce the frictional resistance of the pipeline.

[0071] Step S102 involves controlling the quality of the raw aggregate, including washing and sieving, to reduce stone powder content and increase the proportion of large-diameter aggregate. Specifically, the raw aggregate can be pre-treated before concrete preparation. First, it is washed with a high-pressure water gun to remove surface dust and impurities, then sieved through a vibrating screen (5-10mm mesh size) to increase the proportion of aggregates with a diameter of 8-10mm to over 70%, while controlling the stone powder content to below 3%. This reduces the accumulation of fine powder in the pipes, enhances the porosity between aggregates, and improves the overall fluidity of the concrete. This step is particularly important in the narrow environment of small-diameter DN50 pipes, reducing frictional resistance caused by fine powder and preventing sudden pressure increases. Furthermore, regular checks of screen wear are necessary to ensure that the aggregate particle size distribution meets standards and maintains conveying efficiency.

[0072] More specifically, in this step, the stones need to be washed with water to remove mud and impurities, and then sieved and graded. The sieve mesh size is selected as 5-10mm, with a maximum of 12mm. Priority is given to increasing the proportion of stones with a particle size in the 8-10mm range to over 70%, and the stone powder content is controlled within 3% to reduce the specific surface area of ​​the aggregate, reduce the paste requirement, and thus improve the overall lubricity of the concrete. For example, in a project with an irregular roof structure, after washing the stones, a double-layer sieve (10mm upper layer and 5mm lower layer) is used for filtration. The proportion of large-diameter stones is increased to 75%, and the stone powder content is reduced to 2%. After the concrete viscosity is reduced, the pressure stabilizes at 22-24MPa when transported 150m in a DN50 pipeline, avoiding a sharp increase in pressure at a slump of 80mm.

[0073] Step S103 involves setting up a reducing pipe system. All diameter changes are completed at the outlet of the wet spraying machine in one go. The main pipe is set so that the steel pipe accounts for more than 80% of the total pipe length, and the rubber hose length does not exceed 30m. At bends, 135° or 150° bends with a bending radius of at least 10 times the pipe diameter are used. Specifically, during pipe installation, a reducing joint can be directly connected to the outlet of the wet spraying machine to adjust the initial pipe diameter (e.g., DN80) to the smaller pipe diameter DN50 in one go, ensuring that all diameter changes are concentrated here. Then, the pipe system is laid, in which the steel pipe (smooth inner wall) accounts for more than 80% of the length, and the rubber hose is only used for end connection, with a length limited to within 30m. At the bends, large-radius bends (bending radius of 500mm, calculated based on DN50 pipe diameter) are used, with the angle set to 135° or 150° to reduce energy loss caused by sharp bends. This step optimizes the pipeline layout, reduces local resistance, and avoids pressure accumulation and blockage caused by friction at bends during long-distance transportation. For example, the length of the pipe section needs to be measured during installation to ensure that the steel pipe is the main component and the rubber hose is only used to absorb vibration.

[0074] Step S104 involves adjusting the air content of the concrete to increase it to over 10% before transport and reduce it to 3%–5% after spraying. Specifically, during the concrete mixing stage, an air-entraining agent (such as rosin resin) is added at a dosage controlled at 0.01%–0.03% (by weight). The concrete is then mixed at high speed (100–150 rpm) for 5–8 minutes to raise the air content to 10%–12%. After spraying, a pressure-reducing device (such as a diffuser) at the nozzle of the wet spraying machine is used to release some of the gas as the concrete is sprayed, causing the air content to drop back to the 3%–5% range. This step effectively solves the transportation challenges under low slump and small pipe diameter conditions: the high air content creates an air cushion effect during transport, reducing the adhesion between the concrete and the pipe wall and decreasing frictional resistance, thus supporting efficient long-distance transport exceeding 100m; the reduced air content after spraying ensures the hardening strength of the concrete and avoids structural defects. For example, operators need to use an air content meter to monitor the air content in real time to ensure accurate adjustment.

[0075] In a more specific embodiment, an air-entraining agent, such as an alkyl sulfonate, can be added during the concrete mixing stage at a rate of 0.02%-0.05% of the cement weight to increase the air content to 10%-12%. After being transported, the air content is naturally reduced to 3%-5% after being atomized at high speed by an injector. This ensures pumping lubrication without affecting the final structural strength.

[0076] Step S105 involves adjusting the air content before concrete conveying in real time based on the target conveying height H and target conveying distance L. Specifically, the H and L parameters (e.g., H=50m, L=120m) can be obtained through a control system (such as PLC programming), and the algorithm calculates the optimal air content value (e.g., the formula can be: air content = 10% + k*(H+L) / 100, where k is a correction coefficient, taken as 0.05-0.1). Then, the amount of air-entraining agent added is automatically adjusted to ensure that the air content is dynamically optimized within the range of 10%-15%. This step directly addresses the situation where the conveying position may change during concrete conveying, thereby changing the values ​​of H and L. The dynamic air content adjustment balances lubrication requirements and pressure control, avoiding sudden pressure increases and pipe blockages; for example, when H or L increases, the system automatically increases the air content to compensate for the resistance caused by gravity or distance.

[0077] In one embodiment, a tunnel project required shotcrete to be delivered to a height H=40m and a distance L=110m, with a slump controlled at 80mm and a pipe diameter of DN50. First, the operator activated the vibrator in the wet shotcrete machine's hopper to allow slurry to seep out and cover the aggregate. Next, the aggregate was washed and sieved, with 75% of the particles being 8-10mm in diameter and the stone powder content reduced to 2%. During pipeline installation, the outlet diameter was changed to DN50 in one go, with a steel pipe length of 90m (82% of the total length) and a 25m rubber hose. A 135° bend with a diameter of 500mm was used at bends. An air-entraining agent was added during mixing, adjusting the air content to 12%, which was reduced to 4% after spraying. Based on H=40m and L=110m, the system calculated an air content of 11.5% in real time and automatically adjusted accordingly. As a result, the concrete was efficiently transported 110m, with the pressure stabilized below 15MPa, and no pipe blockage occurred, successfully solving the long-distance transport problem.

[0078] Next, refer to Figure 2 The present invention describes the steps of adjusting the air content before conveying concrete in real time based on the target conveying height H and the target conveying distance L.

[0079] S201: Calculate the initial air content reference value A_ref based on the target conveying height H and target conveying distance L. This step determines the basic air content to meet pumping requirements. H and L represent the required vertical height and conveying distance of the concrete, respectively, in meters. H typically ranges from 0 to 100 meters, and L also ranges from 0 to 100 meters. A_ref is the air content percentage, with an optimal value between 10% and 15%. For example, in one embodiment, when H = 50 meters and L = 100 meters, A_ref = 11% is calculated using the empirical formula A_ref = 0.1*H + 0.06*L. This setting balances the impact of height and distance on pumping resistance, avoiding conveying failures due to improper initial settings. It is understood that calculating A_ref using A_ref = 0.1*H + 0.06*L is merely an example; other methods can also be used to calculate A_ref based on H and L.

[0080] S202: Adjust the air content based on the concrete slump S, where S is in the range of 60mm to 140mm. This step means fine-tuning the air content according to fluidity; higher slumps require higher air content to improve pumpability. Specifically, when S=100mm, the air content increases by 0.5%. For example, in a shotcrete scenario, if S is 120mm, the adjusted air content rises to 11.5% to compensate for the risk of segregation caused by excessively high slumps. It is understandable that other methods can also be used to adjust the air content based on the concrete slump S.

[0081] S203: If the target conveying distance L is greater than L_min, the gas content A before conveying is increased to avoid pipe blockage, where L_min represents a reference distance threshold for long-distance conveying (e.g., 70 meters). This step means that long-distance pumping requires additional gas content to reduce frictional resistance. For example, if L_min = 70 meters, and L = 120 meters, the gas content is increased by 1% to 12%. Specifically, in tunnel spraying operations, this prevents pipe blockage. In this application, when the target conveying distance L is greater than L_min, the specific increase in the gas content A before conveying can be set to a fixed value, such as 1.5%, or other methods can be used to calculate the increase.

[0082] S204: Dynamically fine-tune the gas content based on the pipeline pressure monitoring value P to maintain pressure stability. This step means optimizing the gas content in real time in response to pressure changes. For example, in one embodiment, if P exceeds the 2MPa threshold, the gas content is increased by 0.2% to ensure that pressure fluctuations during delivery are less than 10%, avoiding uneven injection caused by sudden pressure increases. It is understood that the specific increase in gas content can be fixed or determined in other ways.

[0083] Next, refer to Figure 3The present invention describes the steps of calculating the initial gas content reference value A_ref based on the target conveying height H and the target conveying distance L.

[0084] S301: Calculate the basic air content value A_base based on the target conveying height H and the target conveying distance L, where A_base is proportional to H and L, using the formula A_base = 0.1*H + 0.06*L, where H represents the vertical height (range 0-100 meters) and L represents the distance (range 0-100 meters). This formula is set because higher H and L increase pumping resistance, and the proportional relationship ensures improved flowability through a higher basic air content. For example, in one embodiment, H = 50 meters and L = 100 meters, then A_base = 11 (unit: percentage, representing the air volume percentage). It is understood that A_base can also be calculated using other formulas.

[0085] S302: Adjust A_base based on pipe diameter D (fixed at DN50, i.e., 50 mm) and slump S (range 60-140 mm). The adjustment method includes multiplying by the pipe diameter factor f(D) and the slump factor g(S), where f(D) is set to 1.0 based on DN50 (because the standard pipe diameter has little impact), and g(S) increases as S decreases (e.g., g(S) = 100 / S). This adjustment adapts to actual working conditions. For small slump or non-standard pipe diameters, the air content needs to be adjusted to optimize delivery. Specifically, for example, if S = 110 mm, then g(S) = 100 / 110 ≈ 0.9, and after adjustment, A_base becomes 11 × 1.0 × 0.9 = 9.9.

[0086] S303: If the slump S is less than the slump reference value S_ref (set to 120 mm), then increase the air content compensation value ΔA_s (range 1-5%, optimal value 2%). This means that low slump concrete has high viscosity, and compensating ΔA_s can reduce friction loss. For example, if S=110 mm is less than S_ref=120 mm, then increase ΔA_s=2%, and the air content after compensation is 9.9 + 2=11.9.

[0087] S304: The pre-conveying air content A is set based on the corrected air content and directly used for shotcrete preparation to ensure improved conveying efficiency under high H and L conditions. In one embodiment, the final A in the above example is 11.9%, which is applied to shotcrete scenarios with a conveying height of 50 meters and a distance of 100 meters, effectively reducing the risk of pipe blockage.

[0088] Next, refer to Figure 4 This describes the steps of the present invention for calculating the basic gas content value A_base based on H and L.

[0089] S401: Calculate the pipeline resistance coefficient R based on height H and distance L. H represents the vertical height of concrete delivery (range: 0-100 meters), and L represents the delivery distance (range: 0-100 meters). In one embodiment, R is calculated using the formula R = 0.1 × H + 0.05 × L, which represents the resistance to concrete flow within the pipeline. This formula increases with increasing H and L. This formula is used because height and distance directly affect pumping resistance; higher resistance necessitates adjustments to the air content to improve flowability. For example, in one embodiment, when H is 50 meters and L is 100 meters, R = 0.1 × 50 + 0.05 × 100 = 5 + 5 = 10.

[0090] S402: Determine the gas content adjustment factor k based on the drag coefficient R. k represents the scaling factor that varies with R (range: 0.1-1.0, optimal value 0.5), calculated by k = 0.1×R. This means that the larger R is, the higher k is, to amplify the gas content adjustment range. This relationship is set to compensate for the flow loss under high drag. For example, specifically, when R is 10, k = 0.1×10 = 1.0.

[0091] S403: If the resistance coefficient R is greater than the threshold R_th, then A_base = A_min + k × (R - R_th). Where R_th is the resistance threshold (range: 10-15, optimal value 12.5), A_min is the minimum air content (range: 10-14%, optimal value 12%), and k is the aforementioned adjustment factor. The formula means that when R exceeds R_th, the base air content increases linearly to ensure the concrete remains pumpable under high resistance; this setting is because the threshold mechanism avoids unnecessary adjustments, and the k × (R - R_th) term precisely matches the resistance increment. For example, in one embodiment, R_th is 12.5, A_min is 12%, if R = 10 and k = 1.0, then A_base = 12% + 1.0 × (10-12.5) % = 9.5%.

[0092] S404: Further optimize A_base based on slump S. S represents the concrete slump (range: 60-140 mm). Optimization is achieved by A_base_optimized = A_base × (100 / S), meaning that a higher S indicates better fluidity and can moderately reduce air content. This optimization is set to balance workability and air content, avoiding excessive air entrainment that leads to strength loss. For example, specifically, if S is 120 mm and A_base is 9.5%, then after optimization, A_base_optimized = 9.5% × (100 / 120) ≈ 7.9%.

[0093] Next, refer to Figure 5The present invention describes the steps for calculating the pipeline resistance coefficient R based on H and L.

[0094] S501: Calculate the equivalent conveying length L_eq based on the conveying height H and the conveying distance L, where L_eq = L + c ×H, and c represents the height conversion coefficient;

[0095] S502: Determine the resistance factor f based on the pipe diameter D and slump S;

[0096] S503: If L_eq is greater than the maximum equivalent transport length threshold L_eq_max, then R = f × L_eq;

[0097] S504: Verify the R value based on real-time monitoring of pressure gradient.

[0098] In step S501, L_eq is calculated to convert the vertical resistance into an equivalent conveying distance, simplifying resistance assessment. In the formula L_eq = L + c × H, H is the vertical height of the concrete conveying (range: 1-100 meters), L is the length of the conveying pipe (range: 0-100 meters), and c is the height conversion factor (range: 0.5-2, with an optimal value of approximately 1.5, depending on the pipe material). This formula is set based on the fact that vertical height increases frictional resistance, and c converts H into an equivalent conveying length, ensuring more accurate resistance calculation. For example, in one embodiment, H = 15 meters, L = 60 meters, and c is taken as 1.5 (optimal value), then L_eq = 60 + 1.5 × 15 = 82.5 meters.

[0099] In step S502, the resistance factor f is determined based on the pipe diameter D (fixed at DN50) and slump S (a measure of concrete fluidity, ranging from 60 to 140 mm), and the value of f is obtained by looking up a table or empirical formula. This reflects the influence of pipe size and concrete properties on resistance. Specifically, for example, when S = 150 mm, f may be 0.1 (based on experimental data).

[0100] In step S503, it is determined whether L_eq is greater than L_eq_max. If so, then R = f × L_eq. This avoids calculation errors caused by excessively long equivalent distances. For example, if L_eq_max is set to 100 meters, in the previous example, L_eq = 82.5 meters, which is less than 100 meters, so this calculation is skipped; however, if L_eq = 120 meters, then R = 0.1 × 120 = 12.

[0101] Finally, the R-value is verified based on real-time monitored pressure gradients (such as pressure changes per meter of pipeline) to ensure consistency with actual operating conditions. For example, in one embodiment, when shotcrete is transported to a height of 30 meters and a distance of 80 meters, the monitored pressure gradient is 0.05 MPa / m, and the calculated R-value is adjusted accordingly. The entire process optimizes the calculation of the resistance coefficient and improves the efficiency of shotcrete delivery.

[0102] Next, refer to Figure 6 The present invention describes the steps for calculating the equivalent transport length L_eq based on H and L.

[0103] S601: Calculate the slope factor m based on the height H and the conveying distance L, where m = H / L; this formula represents the steepness of the conveying path, with H being the concrete conveying height and L being the conveying distance. A smaller m value indicates a gentler path. This formula is set to quantify the effect of slope, as steep paths increase conveying resistance. For example, in one embodiment, when H = 40 meters and L = 200 meters in shotcrete construction, m = 0.2, reflecting a moderate slope.

[0104] S602: Adjust the height influence weight w based on the slope factor m; w quantifies the contribution of height to the equivalent length, and its range is typically 0.1-1.0. w increases with increasing m to ensure a higher weight on steep slopes. This step is set because concrete is easily affected by gravity during vertical transport, requiring dynamic adjustment of the weight. Specifically, if m=0.3, w can be adjusted to 0.6, indicating a significant height influence.

[0105] S603: If the slope factor m is greater than the threshold m_th (e.g., m_th = 0.15), then calculate L_eq = L × (1 + w × m); this formula extends the equivalent length to simulate slope resistance, with parameter w being the adjusted weight and m being the slope factor. The formula means that when the slope exceeds the threshold, L_eq amplifies L through a factor of (1 + w × m) to reflect the additional conveying difficulty. This formula is designed to optimize pumping parameters and avoid concrete blockage. For example, in a scenario where the height of shotcrete delivery is increased, if H = 50 meters, L = 100 meters, m = 0.5 (greater than m_th = 0.2), and w = 0.7, then L_eq = 100 × (1 + 0.7 × 0.5) = 135 meters.

[0106] S604: Calibrate L_eq based on concrete rheological parameters; rheological parameters such as viscosity or yield stress are used to fine-tune L_eq to compensate for differences in concrete fluidity. This step is set because the rheological properties of different concretes affect conveying efficiency, and calibration is required to improve accuracy. For example, in one embodiment, for high-viscosity concrete (viscosity 300 Pa·s), L_eq can be increased by 15% to ensure that the equivalent length accurately reflects the actual resistance.

[0107] Next, refer to Figure 7 The present invention describes the steps of dynamically fine-tuning the gas content based on the pipeline pressure monitoring value P.

[0108] S701: Calculate the pressure change rate dP / dt based on the pressure monitoring value P;

[0109] S702: Adjust the gas content fine-tuning amount ΔA_p based on dP / dt and distance L;

[0110] S703: If the rate of change of pressure dP / dt is greater than dP_th, then ΔA_p = k_p × (dP / dt - dP_th);

[0111] S704: Limit the maximum value of ΔA_p based on the target distance L.

[0112] In this embodiment, the pressure change rate dP / dt is calculated to monitor the dynamic changes in pressure within the pipeline in real time and identify abnormal fluctuations; adjusting ΔA_p combines the pressure change rate and the conveying distance L to optimize the flowability of concrete; when dP / dt exceeds the threshold dP_th, the formula ΔA_p = k_p × (dP / dt - dP_th) is used to calculate the fine-tuning amount, which aims to buffer pressure shocks by increasing the air content; finally, limiting the maximum value of ΔA_p can prevent concrete segregation caused by over-adjustment and ensure conveying stability.

[0113] Specifically, in the formula ΔA_p = k_p × (dP / dt - dP / dt_th), the parameter dP / dt represents the pressure change rate in Pa / s, typically ranging from -10 to 10 Pa / s, with an optimal value close to 0 indicating a steady state; dP_th is a preset threshold ranging from 1 to 5 Pa / s (e.g., 3 Pa / s is optimal), used to distinguish between normal and abnormal pressure changes; k_p is a pressure adjustment coefficient ranging from 0.1 to 0.5 (optimal value 0.3), serving as a proportional factor to control the adjustment range. This formula is designed to automatically increase the gas content to reduce viscosity when pressure rises rapidly (e.g., due to pipeline blockage risk), preventing delivery interruptions while avoiding unnecessary adjustments.

[0114] In one embodiment, for example, when delivering shotcrete to a high-rise building, the target distance L is 100 meters. If the pressure monitoring value P shows that dP / dt is calculated to be 4 Pa / s (greater than dP_th = 3 Pa / s), then ΔA_p = 0.3 × (4-3) = 0.3%, indicating an increase in air content of 0.3%. Subsequently, based on L = 100 meters, the maximum value of ΔA_p is limited to no more than 0.5% to ensure that the concrete remains homogeneous during long-distance delivery and to prevent segregation. This process optimizes delivery efficiency in real time.

[0115] Next, refer to Figure 8 The present invention describes the steps for calculating the pressure change rate dP / dt based on the pressure monitoring value P.

[0116] S801: Fitting a pressure trend line based on time-series pressure data. This step involves collecting sequential data of pressure monitoring values ​​P over time t and applying methods such as linear regression to fit a straight-line trend line to capture the overall direction of pressure changes. For example, in one embodiment, during the sprayed concrete pumping process, pressure values ​​(in MPa) are recorded every 0.5 seconds to form time-series data. Then, the least squares method is used to fit a straight line to eliminate noise and reflect the trend of pressure increase or decrease.

[0117] S802: Determine dP / dt based on the slope of the trend line. This step directly uses the slope of the fitted straight line as the value of the pressure change rate dP / dt, because the slope represents the rate of change of pressure with respect to time. Specifically, a positive slope of the trend line indicates an increase in pressure, while a negative slope indicates a decrease. For example, when concrete is transported to a height of 20 meters, if the fitted slope is -0.3 MPa / s, then dP / dt = -0.3 MPa / s, indicating that the pressure is gradually decreasing.

[0118] S803: If the absolute value of the slope of the pressure trend line is greater than slope_max, then dP / dt = |slope|. In this formula, slope_max represents the maximum allowable slope threshold (in MPa / s), ranging from 0.5 to 5 MPa / s, with the optimal value typically being 2 MPa / s (based on experimental determination of the delivery system's stability); slope is the fitted slope value. The formula means that when the absolute value of the slope exceeds the threshold, dP / dt is forced to take the absolute value to avoid misjudgment due to extreme changes. This setting ensures that dP / dt remains positive during drastic pressure changes (such as blockage), facilitating a rapid system response. For example, in one embodiment, slope_max is set to 1.8 MPa / s. If the slope is -2.5 MPa / s (absolute value greater than the threshold), then dP / dt = 2.5 MPa / s; otherwise, dP / dt retains the original slope value.

[0119] S804: Calibrate the calculation accuracy of dP / dt based on the conveying distance L. This step uses the conveying distance L (in meters) as the input parameter and adjusts the dP / dt value through a calibration factor to compensate for the influence of distance on pressure changes. The calibration formula can be expressed as dP / dt_cal = dP / dt × (1 + k × L), where k is a calibration coefficient (ranging from 0.001 to 0.01 m^{-1}, with an optimal value of 0.005 m^{-1}), used to scale dP / dt. The formula means that the rate of change is amplified when the distance increases to reflect the greater sensitivity to pressure fluctuations in long-distance conveying. This setting is to improve accuracy and adapt to different conveying scenarios. For example, specifically, when L=50 meters, if the original dP / dt is 1.2 MPa / s and k=0.005, then after calibration, dP / dt_cal = 1.2 × (1 + 0.005×50) = 1.5 MPa / s, ensuring more accurate monitoring of pressure changes in long-distance shotcrete operations.

[0120] The above description is the preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this invention, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method of increasing the height and distance of delivery of shotcrete, characterized by, The concrete delivery process includes the following steps: Turn on the vibrator in the wet shotcrete machine hopper to allow concrete slurry to seep out and enhance lubricity; Controlling the quality of raw stone materials, including washing and sieving, aims to keep the stone powder content below 3% and increase the proportion of stones with a particle size of 8-10mm to over 70%. Install reducers so that all diameter changes are completed at the outlet of the wet spraying machine in one go. Install through pipes so that steel pipes account for more than 80% of the total pipe length. Rubber hoses should not exceed 30m in length. Use 135° or 150° bends with a bend diameter of at least 10 times the pipe diameter at bends. Adjust the air content of the concrete to increase it to over 10% before transportation and reduce it to 3%–5% after spraying; and The air content before concrete conveying is adjusted in real time based on the target concrete conveying height H and target conveying distance L; whereby... The step of adjusting the air content before conveying in real time based on the target concrete conveying height H and target conveying distance L further includes: Calculate the initial gas content reference value A_ref based on the target conveying height H and the target conveying distance L; The air content is adjusted according to the concrete slump S, where S is in the range of 60mm to 140mm. If the target conveying distance L is greater than L_min, the gas content A before conveying is increased to avoid pipe blockage, where L_min represents the reference distance threshold for long-distance conveying; The gas content is dynamically adjusted based on the pipeline pressure monitoring value P to maintain pressure stability; The step of calculating the initial gas content reference value A_ref based on the target conveying height H and the target conveying distance L further includes: The basic value of gas content A_base is calculated based on H and L, where A_base is proportional to H and L. A_base is corrected based on pipe diameter D and slump S; If the slump S is less than S_ref, then the gas content compensation value ΔA_s is increased, where S_ref represents the slump reference value and ΔA_s represents the slump compensation amount. Set the gas content A before transportation based on the corrected gas content; The step of calculating the basic gas content value A_base based on H and L further includes: Calculate the pipe resistance coefficient R based on H and L; The gas content adjustment factor k is determined based on the drag coefficient R; If the drag coefficient R is greater than R_th, then A_base = A_min + k × (R-R_th), where R_th represents the drag coefficient threshold, A_min represents the minimum gas content value, and k represents the gas content adjustment factor. A_base is further optimized based on the collapse degree S; The step of calculating the pipe resistance coefficient R based on H and L further includes: The equivalent transport length L_eq is calculated based on H and L, where L_eq = L + c × H, and c represents the height conversion factor. The resistance factor f is determined based on the pipe diameter D and the slump S. If the equivalent conveying length L_eq is greater than L_eq_max, then R = f × L_eq, where L_eq_max represents the maximum equivalent conveying length threshold. Verify the R value based on real-time monitored pressure gradient; The step of calculating the equivalent transport length L_eq based on H and L further includes: The slope factor m is calculated based on H and L, where m = H / L; The weight w of the height effect is adjusted according to the slope factor m; If the slope factor m is greater than m_th, then L_eq = L × (1 + w × m), where m_th represents the slope factor threshold and w represents the height influence weight. L_eq is calibrated based on concrete rheological parameters.

2. A method of increasing the height and distance of delivery of shotcrete according to claim 1, wherein, The method further includes a step of dynamically fine-tuning the gas content based on the pipeline pressure monitoring value P, including: The pressure change rate dP / dt is calculated based on the pressure monitoring value P. Adjust the gas content fine-tuning amount ΔA_p based on dP / dt and distance L; If the pressure change rate dP / dt is greater than dP_th, then ΔA_p = k_p × (dP / dt-dP_th), where dP_th represents the pressure change rate threshold and k_p represents the pressure adjustment coefficient. The maximum value of ΔA_p is limited by the target distance L.

3. A method of increasing the height and distance of delivery of shotcrete according to claim 2, wherein, The step of calculating the pressure change rate dP / dt based on the pressure monitoring value P further includes: Fit a pressure trend line based on time-series pressure data; Determine dP / dt based on the slope of the trend line; If the absolute value of the slope of the pressure trend line is greater than slope_max, then dP / dt = |slope|, where slope_max represents the maximum allowable slope threshold and slope is the fitted slope value; The accuracy of dP / dt calculation is calibrated based on the conveying distance L.

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