Construction method for reducing shotcrete loss amount of super-long subsurface tunnel

Abstract

The invention provides a construction method for reducing the loss amount of sprayed concrete of an ultra-long subsurface tunnel, and relates to the technical field of tunnel construction of water conservancy projects. According to the technical scheme provided by the embodiment of the invention, through the drilling and blasting control optimization, spraying equipment upgrading, concrete proportion improvement and process parameter precise regulation and control four-dimensional collaborative technology, the spraying concrete loss amount of the super-long underground excavation tunnel is systematically reduced. In the embodiment of the invention, the nano anti-bounce agent is combined with a layered injection process, so that the rebound rate is obviously reduced compared with that of a traditional process; in the embodiment of the invention, the injection parameters are adjusted in real time based on the rock surface state, and complex geological conditions can be adapted. Based on the technical scheme provided by the embodiment of the invention, the material cost of tunnel concrete per kilometer can be greatly saved, and the comprehensive construction period is remarkably shortened.

Description

TECHNICAL FIELD

[0001] The embodiment of the application relates to the technical field of water conservancy tunnel construction, and particularly relates to a construction method for reducing loss of sprayed concrete of an overlong tunnel. BACKGROUND

[0002] Tunnel construction is a core link of underground engineering construction such as water conservancy and traffic tunnels, and the core support technique (sprayed concrete technology) directly affects the safety, cost and construction period of the project. In the traditional process, the high rebound rate and large overbreak of sprayed concrete have long plagued the industry, especially in soft surrounding rock strata.

[0003] In the conventional dry spraying or wet spraying process, when the concrete is sprayed to the rock surface, it is easy to rebound due to insufficient kinetic energy or poor adhesion. In the construction of tunnels in class III to V surrounding rock, the rebound of the side wall is more prominent, resulting in an increase in the actual concrete loss and an increase in material costs. In addition, during the construction of the drill and blast method, the overbreak depth is generally large due to the influence of geological conditions and blast parameter deviations. The overbreak part needs to be sprayed with additional concrete to fill, further exacerbating material waste. At the same time, overbreak leads to redistribution of surrounding rock stress, which may induce local collapse and threaten construction safety. The traditional construction relies on experience to control the spraying distance, angle and layer thickness, and lacks scientific and quantitative standards. Skill differences of operators can easily cause uneven spraying, forming a "wavy" primary support surface, which needs to be corrected by secondary supplementary spraying, reducing construction efficiency. In recent years, the industry has tried to improve the problem through material improvement, equipment upgrading and other means, but there are bottlenecks.

[0004] Therefore, based on the goal of promoting green construction and reducing the loss rate of building materials, a new construction method is urgently needed to solve the problem of loss of sprayed concrete of an overlong tunnel. SUMMARY

[0005] The embodiment of the application provides a construction method for reducing loss of sprayed concrete of an overlong tunnel, which systematically reduces the loss of sprayed concrete of an overlong tunnel through four-dimensional collaborative technology of drill and blast control optimization, spraying equipment upgrading, concrete proportioning improvement and process parameter precise control.

[0006] The first aspect of the embodiment of the application provides a construction method for reducing loss of sprayed concrete of an overlong tunnel, which comprises the following steps: Based on preset drill and blast parameters, the blasting effect is dynamically adjusted through three-dimensional modeling simulation, the rock mass crushing range under different charge amounts is simulated, the target drill and blast parameters are determined, and the preset drill and blast parameters comprise a contour line blasting hole offset, a hole distance, a single hole charge amount and a plugging length; the contour line blasting hole offset is used to offset the contour line blasting hole to the direction of the tunnel center, forming a reserved buffer layer; Determine the material ratio of the concrete based on the target concrete performance index, the material of the concrete comprising: base materials and nano elastic resistance agent; Complete drilling and blasting according to the target drilling and blasting parameters; Determine the construction parameters of the hydraulic wet spraying integrated machine based on engineering requirements, and complete concrete spraying construction based on the construction parameters and the layered spraying process; Detect the over-excavation amount and recycle the rebound material.

[0007] Optionally, the method further comprises determining the contour line blasting hole offset amount by the following steps: For Class III-V surrounding rock, calculate the contour line blasting hole offset amount according to the offset amount calculation formula: Wherein, is the offset amount, Q is the single-hole charge amount, L is the hole depth, k is the surrounding rock coefficient, 0.8 for Class III, 1.0 for Class IV, and 1.2 for Class V, and S is the safety margin.

[0008] Optionally, the concrete performance index includes slump, initial setting time and 28d compressive strength, and the base materials include cement, sand, gravel, water reducing agent, accelerator and water. Determine the material ratio of the concrete based on the target concrete performance index, comprising: Dry mix the nano elastic resistance agent with the cement at a ratio of 1:25 to obtain a mixed material; Mix and stir the mixed material and other base materials according to the candidate preset ratio of the base materials to obtain a candidate concrete; Determine the material ratio of the concrete that meets the target concrete performance index based on the slump, initial setting time and 28d compressive strength of the candidate concrete.

[0009] Determine the construction parameters of the hydraulic wet spraying integrated machine based on engineering requirements, comprising: Determine the concrete spraying amount based on engineering requirements; Determine the model, mechanical arm length and joint degrees of freedom of the hydraulic wet spraying integrated machine based on the concrete spraying amount.

[0010] Optionally, the layered spraying process comprises: Complete the initial spraying layer within 2h after blasting, the thickness of the initial spraying layer is 3-5cm, the air pressure is 0.3MPa, and it is used to close the rock surface fissures; Complete the re-spraying layer by spraying 2-3 times to the designed thickness, the single layer thickness is 5-8cm, and the layer interval is 20-30min; Complete the finishing layer by using the spiral superposition spraying method, the nozzle spirally advances at a speed of 0.3m / s to ensure that the surface flatness is ≤3cm / m.

[0011] Optionally, complete the concrete spraying construction based on the construction parameters and the layered spraying process, comprising: In the process of jetting construction, the jetting distance is determined according to the rock surface state; The jetting angle is determined within a preset deviation, and concave and convex rock surfaces are sequentially filled in the order of concave first and convex second; The air pressure is adjusted in real time according to the jetting distance.

[0012] Optionally, the air pressure is adjusted in real time according to the jetting distance and the following formula: ; Wherein, P is the air pressure (MPa), and D is the jetting distance (m).

[0013] Optionally, the method further comprises detecting the jetting distance based on a laser range finder; detecting the jetting angle based on a sensor; uploading detection data to a cloud console.

[0014] Optionally, the overbreak amount is detected, comprising: A Trimble SX10 three-dimensional scanner is used to scan the section after each cycle of blasting, and an overbreak cloud chart is generated; The overbreak volume is calculated by PointCab software, and the overbreak position is marked, which is used to guide the supplementary jetting operation.

[0015] Optionally, the rebound material is recycled and utilized, comprising: Waterproof canvas is laid under the jetting surface, the lap joint is greater than or equal to 30 cm, the rebound material is screened to remove particles with a particle size greater than 10 mm, and then the rebound material is mixed into the freshly mixed concrete at a proportion of 10% to 15%; The amount of concrete used for each vehicle is tracked by an RFID tag, and the actual rebound rate is calculated in combination with the amount of canvas collected.

[0016] The technical scheme provided by the embodiment of the application reduces the loss amount of jetted concrete of an overlong underground excavation tunnel in a systematic manner through four-dimensional collaborative technology of drilling and blasting control optimization, jetting equipment upgrading, concrete proportioning improvement and process parameter precise regulation.

[0017] In the embodiment of the application, the nano rebound inhibitor is combined with the layered jetting process, so that the rebound rate is significantly reduced compared with the traditional process. In the embodiment of the application, the jetting parameters are adjusted in real time based on the rock surface state, so that the complex geological conditions can be adapted.

[0018] Based on the technical scheme provided by the embodiment of the application, the cost of concrete material per kilometer of tunnel can be greatly saved, and the overall construction period can be significantly shortened. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the description of the embodiments of the present application. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0020] Figure 1 is the step flow chart of the construction method for reducing the loss amount of shotcrete of the super-long tunneling tunnel provided by the embodiments of the present application; Figure 2 The structural schematic diagram of the peripheral hole optimization design of an exemplary embodiment provided by the embodiments of the present application is shown. Figure 3 The layered shotcrete process flow chart of the construction method for reducing the loss amount of shotcrete of the super-long tunneling tunnel provided by the embodiments of the present application. DETAILED DESCRIPTION

[0021] In order to make the above-mentioned purposes, features and advantages of the present application more apparent and easy to understand, the following will further specifically describe the present application with reference to the drawings and specific embodiments.

[0022] At present, in the scheme of optimizing the construction method through material improvement technology, although the steel fiber reinforced concrete can improve the tensile strength and reduce the rebound rate, the steel fiber is easy to form a group and block the spray pipe, and the cost is increased; the silicon-based nanometer material can reduce the rebound rate, but the dispersion of the nanometer particles is poor in the actual engineering, the control precision of the mixing amount is high, and the large-scale application is difficult; although the excessive addition of the accelerator can shorten the setting time, it will reduce the later strength of the concrete and increase the cracking risk.

[0023] In the scheme of optimizing the construction method through material equipment and process, the automatic shotcrete mechanical arm can accurately control the spraying track, but the equipment procurement cost is high, and the project economy is insufficient; the smooth blasting technology can control the overbreak by encrypting the peripheral hole and reducing the charging amount, but the "underbreak-supplement blasting" cycle is easy to occur in the joint development stratum, and the construction period is prolonged; although the BIM simulation can guide the construction, the model precision depends on the geological survey data, and the adaptability to the hidden fault and fissure water is insufficient.

[0024] Based on this, the embodiments of the present application provide a construction method for reducing the loss amount of shotcrete of the super-long tunneling tunnel by optimizing the drilling and blasting parameters, improving the shotcrete process and material ratio.

[0025] Specifically, as shown in Figure 1 The step flow chart of the construction method for reducing the loss amount of shotcrete of the super-long tunneling tunnel provided by the embodiments of the present application is shown, and the method comprises the following steps: S101, based on the preset drilling and blasting parameters, the blasting effect is dynamically regulated through three-dimensional modeling pre-rehearsal, the rock mass fragmentation range under different charge amounts is simulated, and the target drilling and blasting parameters are determined, the preset drilling and blasting parameters include: contour line blasting hole offset, hole distance, single hole charge and blockage length; the contour line blasting hole offset is used to offset the contour line blasting hole to the direction of the tunnel center, and a reserved buffer layer is formed.

[0026] In the embodiment of the application, based on the contour line blasting hole offset design, for class III-V surrounding rock, the peripheral hole (i.e. contour line blasting hole) is offset to the direction of the tunnel center according to the offset calculation formula, forming a "reserved buffer layer".

[0027] The "reserved buffer layer" can reduce the impact of blasting vibration: during tunnel blasting construction, the energy generated by the explosion spreads to the surrounding in the form of vibration waves, causing disturbance to the surrounding rock. The reserved buffer layer can weaken the intensity of the blasting vibration wave and reduce the degree of disturbance to the surrounding rock. For example, in hard rock tunnel blasting, without a buffer layer, blasting vibration may cause micro-cracks in the surrounding rock and expansion, and after the reserved buffer layer, when the vibration wave propagates to the buffer layer, part of the energy is absorbed and dissipated by the buffer layer, reducing the energy transmitted to the surrounding rock, thereby effectively controlling the generation and expansion of micro-cracks in the surrounding rock and maintaining the integrity and stability of the surrounding rock.

[0028] The "reserved buffer layer" can also prevent overbreak and collapse of the surrounding rock: if the peripheral hole is drilled and blasted according to the designed contour line, in actual operation, due to the uncontrollability of blasting, overbreak is prone to occur, which will increase the free surface of the surrounding rock, redistribute the stress, increase the risk of instability of the surrounding rock, and even cause local collapse. After the reserved buffer layer, even if there is a certain deviation in blasting, excessive overbreak can be avoided, ensuring the stability of the surrounding rock. For example, in soft surrounding rock tunnels, overbreak can easily cause problems such as spalling and collapse, and the buffer layer can provide some protection, giving time and conditions for subsequent support work.

[0029] In subsequent concrete spraying operations, the reserved buffer layer provides a more reasonable space for the sprayed concrete construction, enabling the sprayed concrete to more evenly cover the surrounding rock surface and ensure that the thickness of the sprayed concrete meets the design requirements. Without the buffer layer, the unevenness of the surrounding rock surface caused by blasting may result in local over-thickness or under-thickness of the sprayed concrete, and the under-thickness areas may not meet the support strength requirements, while the over-thickness may cause material waste. For example, during the initial concrete spraying operation, the buffer layer can enable the sprayed concrete to better fill the unevenness of the surrounding rock surface, forming a support layer with uniform thickness. The buffer layer can provide a better adhesion basis for the sprayed concrete during spraying, reducing the impact of factors such as unevenness of the surrounding rock surface and loose rock blocks on the bonding effect. During the spraying of concrete, the concrete can be closely combined with the buffer layer and the surrounding rock, forming a unified support structure and improving the reliability of the support. For example, the continuous and effective bonding between the sprayed concrete and the surrounding rock can better transfer stress and jointly resist external loads.

[0030] The reserved buffer layer reduces the adverse effects of blasting on the surrounding rock, reduces the probability of safety accidents such as surrounding rock collapse and rockfall, and provides a safer working environment for subsequent construction personnel and equipment. For example, before the sprayed concrete support is performed after tunnel excavation, the surrounding rock is in a relatively unstable state, and the buffer layer can ensure the safety of construction personnel to some extent during this stage. In the long run, the reserved buffer layer reduces additional work such as overbreak backfill, avoids the cost of secondary treatment due to surrounding rock instability, ensures the construction quality of sprayed concrete, reduces the reinforcement cost due to insufficient support in the later stage, and effectively controls the overall cost of the project.

[0031] Specifically, in the embodiment of the present application, the following steps can be used to determine the contour line blasting hole offset: For Class III~V surrounding rock, the contour line blasting offset is calculated according to the offset calculation formula: ; wherein, is the offset, Q is the single-hole charge, L is the hole depth, k is the surrounding rock coefficient, 0.8 for Class III, 1.0 for Class IV, and 1.2 for Class V, and S is the safety margin.

[0032] In the embodiment of the present application, through investigation of prior overbreak data, it is found that the overbreak depth is between 14.7cm and 43.8cm, and the average overbreak depth is 33.8cm. At the same time, according to the stratum conditions and investigation data, it is finally decided to offset the peripheral eye blasting hole (i.e. contour line blasting hole) towards the center of the tunnel, forming a "reserved buffer layer".

[0033] In the embodiment of the present application, the offset calculation formula is finally determined in combination with the theoretical technology for the representative geological conditions of the study area and the case of overlong underground excavation tunnel.

[0034] Specifically, the engineering profile of the research area involved in the embodiments of the present application is: The Gaotian Tunnel of the Beibuwan Guangdong Water Resources Allocation Project Construction B3 Section is constructed by the drill and blast method, has a total length of 6.51 km, a longitudinal slope of 0.38 ‰, is provided with two work zones and three working faces, has a circular cross section with an inner diameter of 7.1 m and a reinforced concrete lining, and is mainly constructed by the drill and blast method and supplemented by open excavation. The water passing cross section of the open excavation section is circular with an inner diameter of 7.1 m and adopts a reinforced concrete box culvert structure. The open excavation section is used as a construction period residue discharge and material transportation passage via the import and export of the Gaotian Tunnel first and last ends. The drill and blast tunnel of the Gaotian Tunnel has a circular excavation cross section with a size of φ8.1 m, a total length of 3330 m, and an occupancy ratio of 51.15%. The excavation cross sections of the Class IV and Class V surrounding rocks have a horseshoe shape, the excavation size is φ8.5 m, the Class IV surrounding rock has a length of 1742.175 m and an occupancy ratio of 26.76%, and the Class V surrounding rock has a length of 1336.5 m and an occupancy ratio of 20.53%.

[0035] The Gaotian Tunnel is mainly constructed by the drill and blast method and supplemented by open excavation. The drill and blast method requires a large amount of initial support spraying concrete, and the stratum is weak. When the traditional spraying concrete construction is performed, the rebound rate is large and the loss rate is high, and there are risks in construction cost, construction period, quality and the like. Reducing the spraying concrete loss amount in the construction process is of great significance to the cost, construction period, quality and the like of the project.

[0036] The 6.51 km (pile number GH38+260-GH44+770) section of the Gaotian Tunnel of the Beibuwan Guangdong Water Resources Allocation Project Construction B3 Section is a key and difficult point control of the project, and the construction quality directly affects the project cost. According to the collected relevant data, it is found that due to the complex geological conditions, limited construction space and other factors, the drill and blast overbreakage is averagely 30 cm, and the spraying concrete loss amount is averagely 33.77%, which affects the project quality and cost control.

[0037] In the embodiments of the present application, the hole spacing, single hole charge amount and plugging length and the like hole network parameters also need to be determined, wherein the hole spacing is determined according to the surrounding rock grade, the charge type adopts a φ25 mm emulsified blasting material roll, the charge amount adopts an empirical value, the blast hole plugging length is greater than or equal to 20 cm, and clay stemming is mechanically compacted.

[0038] In the embodiments of the present application, after the preset drill and blast parameters are determined, the blasting effect dynamic regulation and control can be performed through three-dimensional modeling pre-performance. The Rhino+BlastCAD software is used to establish a tunnel geology-blasting model, simulate the rock mass fragmentation range under different charge amounts, and finally screen out a scheme with an overbreakage amount less than 15 cm.

[0039] In the embodiments of the present application, based on the three-dimensional modeling pre-performance, the blasting effect dynamic regulation and control is performed, the most suitable drill and blast parameters are finally screened out, and are used for actual engineering drill and blast.

[0040] Figure 2 The structure diagram of the peripheral hole optimization design of an example embodiment provided by the embodiment of the application is shown. According to the offset calculation formula, the following is obtained: Class V surrounding rock: K = 1.2, Δ = 1.2 x 0.25 / 3 + 3 = 3.1 cm, and the integer is 3 cm. Further, according to the surrounding rock grade, the hole spacing, the charge amount, the plugging length and other hole network parameters are determined: the peripheral hole spacing is 40 cm for Class III surrounding rock, 35 cm for Class IV surrounding rock, and 30 cm for Class V surrounding rock; the charge structure is continuous uncoupled charge (charge density 0.25 kg / m); and the plugging length is ≥20 cm (clay stemming is used for mechanical compaction).

[0041] In the dynamic regulation process of the blasting effect, overbreak monitoring is performed, a Trimble SX10 three-dimensional scanner is used to scan the section after blasting, an overbreak cloud chart is generated, then the average overbreak depth is calculated according to the number of detection points and the overbreak amount corresponding to each detection point, and the construction target is met when the average overbreak depth is less than or equal to 15 cm.

[0042] In S102, the material ratio of the concrete is determined based on the target concrete performance index, and the materials of the concrete include: basic materials and nano anti-elastic agents.

[0043] The nano anti-elastic agent has a very small particle size and can be uniformly dispersed in the micro-pores of the concrete. These nano particles can fill the tiny pores formed during the cement hydration process, optimize the microstructure inside the concrete, and make the concrete inside more dense. For example, between the cement hydration products, the nano anti-elastic agent particles act as tiny “wedges”, enhancing the inter-particle interaction force, thereby effectively improving the compressive strength of the concrete, allowing the tunnel lining to withstand greater pressure from the surrounding rock.

[0044] Ordinary concrete has a large brittleness and is prone to cracking when subjected to impact or dynamic load. The nano anti-elastic agent can form an interface transition zone with a certain flexibility by chemically reacting with the cement hydration products. When the concrete is subjected to external forces, these flexible zones can absorb energy and prevent the rapid expansion of cracks, making the concrete exhibit better toughness. For example, when subjected to sudden dynamic loads such as earthquakes, the concrete with added nano anti-elastic agents can effectively delay the extension of cracks and maintain the integrity of the tunnel structure.

[0045] The nano-ballistic-resistant agent usually contains multiple components. Common ones are nanometer microspheres, zeolite powder, nano calcium silicate, etc. Some formulations also contain nano silicon dioxide, which can react with calcium ions in the cement matrix to generate more calcium silicate hydrate, thereby improving the strength of the concrete. In addition, magnesium fluorosilicate may also be one of its components, which can react with free calcium in the concrete to form calcium silicate and calcium fluoride, filling the capillary pores and enhancing the surface structure strength and wear resistance. It improves the adhesion and adhesion of concrete, reduces the rebound phenomenon during the construction process of shotcrete, and improves the construction efficiency and material utilization.

[0046] In the embodiment of the present application, the concrete performance indicators include slump, initial setting time and 28d compressive strength, and the basic materials include cement, sand, gravel, water reducing agent, accelerator and water. The step S102 comprises: The nano-ballistic-resistant agent is dry mixed with cement at a ratio of 1:25 to obtain a mixed material.

[0047] The mixed material and other basic materials are mixed and stirred according to the candidate preset proportion of the basic materials to obtain a candidate concrete.

[0048] In the embodiment of the present application, the candidate preset proportion of the basic materials is preliminarily determined according to the engineering specifications and requirements.

[0049] Based on the slump, initial setting time and 28d compressive strength of the candidate concrete, the material ratio of the concrete meeting the target concrete performance indicators is determined.

[0050] In the embodiment of the present application, the nano silicon dioxide (particle size 50-80 nm, specific surface area ≥200 m² / g) is modified using a silane coupling agent.

[0051] In the embodiment of the present application, the related parameters of the basic materials, nano-ballistic-resistant agent and steel fiber are analyzed and extracted, and then performance testing is performed to finally determine that the nano-ballistic-resistant agent is dry mixed with cement at a ratio of 1:25 to obtain a mixed material.

[0052] Specifically, the addition of the nano-ballistic-resistant agent in the concrete increases the toughness of the material and improves the ballistic and blast resistance performance. It forms a dense structure, improves the overall tensile strength and prolongs the service life of the concrete. It greatly reduces the permeability and enhances the waterproof effect. It makes the concrete more dense, improves the wear resistance and corrosion resistance.

[0053] The use of steel fiber in concrete can reduce the slump loss and improve the fluidity of the concrete. The addition of steel fiber can significantly improve the tensile, bending and shear strength of the concrete, so that the concrete is less likely to crack and break when subjected to complex external forces.

[0054] In the comparative test, the dosage of the nano elastic resistance agent is 32 kg / m3, the dosage of the steel fiber is 40 kg / m3, the compressive strength of the obtained concrete is 31.6 MPa and 30 MPa respectively, and the rebound rates are 7.2% and 12% respectively.

[0055] Therefore, in the embodiment of the application, the nano elastic resistance agent is finally selected to prepare the improved concrete.

[0056] In the embodiment of the application, the preliminary determination of the weight ratio of the concrete material per cubic meter is as follows according to the specification and requirements: Cement: water: gravel: water reducing agent: air entraining agent: accelerator sand = 429 kg: 193 kg: 912 kg: 774 kg: 858 kg: 2.574 kg: 30.03 kg = 1:0.45:2.12:1.80:0.020:0.0060:0.07.

[0057] In the embodiment of the application, the preliminary mixing ratio of the concrete mixture is determined, and the results meet the requirements: good fluidity, cohesiveness and water retention; the wet apparent density is 2300 kg / m3, the slump is 193 mm, and the workability does not need to be adjusted after trial mixing. The trial mixing C25 mixing ratio is preliminarily selected as shown in the following table:

[0058] The performance results of the concrete mixed according to the mixing ratio in the above table are as follows:

[0059] After seven days of maintenance, the mechanical performance results are as follows:

[0060] The final mixing ratio is as follows:

[0061] In the embodiment of the application, the mixing materials (nano elastic resistance agent and cement) and other basic materials (aggregate and admixture) can be synchronously added to a mixer according to the candidate preset ratio of the basic materials to be mixed and stirred, and the aggregate and admixture are obtained to obtain the candidate concrete. That is, the candidate concrete can be obtained by trial, and the optimal material ratio is determined based on the slump, initial setting time and 28d compressive strength of the candidate concrete, so as to obtain the concrete material ratio for the final actual engineering application.

[0062] In the embodiment of the application, the preliminary mixing ratio of the concrete mixture can be determined, and the results meet the requirements of good fluidity, cohesiveness and water retention, etc. After seven days of maintenance, the mechanical performance of the concrete is determined, and the final mixing ratio is selected after meeting the requirements.

[0063] In the embodiment of the present application, the selected final concrete material ratio can be used for test in actual engineering research to further analyze the performance of the concrete.

[0064] In the embodiment of the present application, in order to test whether the method of adding nano elastic resistance agent meets the standard, different areas in the tunnel are selected to perform 5 cycles of test, wherein the first 3 cycles are added with nano elastic resistance agent, and the last 2 cycles are added with nano elastic resistance agent, and the average rebound rate is compared actually.

[0065] For example, in the embodiment of the present application, based on the selection of the above mixing ratio, a region with a length of 14 meters from GH39+260 to GH39+274 in the upper step of the Gaotian tunnel is selected to perform 5 cycles of test, wherein the first 3 cycles are not added with nano elastic resistance agent, and the last 2 cycles are added with nano elastic resistance agent.

[0066] After actual comparison, the average rebound rate without adding nano elastic resistance agent is 33.77%, the average rebound rate with adding nano elastic resistance agent is 13.97%, and the difference is 19.8%. The specific data is shown in the following table:

[0067] S103, drilling and blasting is completed according to the target drilling and blasting parameters.

[0068] In the embodiment of the present application, drilling and blasting of the super-long underground tunnel is completed according to the optimal target drilling and blasting parameters determined in step S101.

[0069] S104, construction parameters of the hydraulic wet spraying integrated machine are determined based on engineering requirements, and concrete spraying construction is completed based on the construction parameters and the layer-by-layer spraying process.

[0070] The most important thing for selecting the tunnel concrete spraying equipment is that the design spraying amount (m³ / h) must meet or exceed the average spraying amount required by the project, and the utilization rate of the equipment is considered. On this basis, the size of the equipment and the size and length of the mechanical arm are determined according to the cross-sectional size of the construction site, and finally the durability and economy of the equipment are considered. In the embodiment of the present application, the hydraulic wet spraying integrated machine is selected. First, the average spraying amount is calculated to be 23-24 m³ / h. Considering that the perfect construction condition of the design spraying amount cannot be met during the construction process, the design spraying amount of 30 m³ / h is selected. Secondly, the cross-sectional bottom width of the tunnel is 5 m, and the height is 8 m. The mechanical arm needs to meet the requirements of spraying concrete to the working surface at 90°-70° (full 90° is the best) in the cross section. The length and joint freedom of the mechanical arm need to meet the requirements.

[0071] Specifically, the construction parameters of the hydraulic wet spraying integrated machine are determined based on engineering requirements, including: The concrete spraying amount is determined based on engineering requirements. Determine the model, mechanical arm length and joint freedom of the hydraulic wet spraying integrated machine based on the concrete spraying amount.

[0072] In the embodiment of the application, the concrete spraying amount can be determined according to actual engineering requirements, and then the model, mechanical arm length and joint freedom of the hydraulic wet spraying integrated machine are determined.

[0073] In the embodiment of the application, the spraying equipment and process parameters need to be optimized to ensure that the rebound loss is controlled within 15%.

[0074] Specifically, the concrete spraying construction efficiency is required to be greater than 25 m3 / h, and the YL3016 type automatic feeding hydraulic wet spraying machine is selected according to the actual requirements of the site construction.

[0075] Specifically, the layered spraying process comprises: The initial spraying layer is completed within 2 hours after blasting, the thickness of the initial spraying layer is 3-5 cm, the air pressure is 0.3 MPa, and the initial spraying layer is used to close the rock surface cracks; The re-spraying layer is completed by spraying 2-3 times to the designed thickness, the single layer thickness is 5-8 cm, and the layer interval is 20-30 min; The finishing layer is completed by using the spiral superposition spraying method, the nozzle is spirally advanced at a speed of 0.3 m / s, and the surface flatness is ensured to be less than or equal to 3 cm / m.

[0076] In the embodiment of the application, the initial spraying layer process is designed to be completed within 2 hours after blasting, and is used to close the rock surface cracks; the re-spraying layer process is designed to be completed by spraying 2-3 times to the designed thickness, the single layer thickness is 5-8 cm, and the layer interval is 20-30 min (determined by the concrete surface “sweating”); the finishing layer process is designed to be completed by using the spiral superposition spraying method, and the nozzle is spirally advanced at a certain speed, and the surface flatness is ensured to be less than or equal to 3 cm / m.

[0077] Specifically, the nozzle is spirally advanced at a speed of 0.3 m / s.

[0078] Figure 3 A layered spraying process flowchart of the construction method for reducing the loss amount of sprayed concrete of an overlong underground excavation tunnel is shown, and in the embodiment of the application, the layered spraying process is carried out according to the following flow: Preparation: first complete the construction preparation, process the sprayed surface, bury the spraying layer thickness marker, carry out the raw material site inspection, select the concrete mix ratio, place the machine and connect the water, electricity and gas, test the machine, and prepare the spraying operation conditions.

[0079] Initial spraying operation: carry out the initial spraying concrete operation by automatically metering and mixing the concrete and transporting the spraying material by the mixer truck, and this link is to establish the concrete layer on the sprayed surface for the first time.

[0080] Intermediate process: After the initial spraying, the steel bar mesh is buried to provide a structural reinforcement basis for subsequent respraying.

[0081] Respraying and related adjustment: Respraying concrete operation is carried out, if supplement spraying or adjustment of mix ratio is needed during the process, corresponding operation is carried out to ensure the spraying effect, and then the finishing layer operation is carried out to perfect the concrete surface.

[0082] Final inspection: After the quality inspection is carried out finally, the process is ended after confirming that the quality of each link meets the standard, each link is connected, the construction quality control of the tunnel sprayed concrete is realized through layered spraying and timely adjustment.

[0083] In the embodiment of the application, the layered spraying process is adopted, and the thickness of each layer of concrete is relatively thin during layered spraying, and the sprayed concrete can better fill the uneven places of the sprayed surface and the tiny pores of the previous layer of concrete. For example, after the initial spraying, the resprayed concrete can penetrate into the fine gaps of the initial spraying layer, so that the whole concrete is more compact, thereby effectively improving the mechanical properties such as compressive strength and shear strength of the concrete, and better bearing the surrounding rock pressure.

[0084] The one-time sprayed concrete is too thick, the accumulated cement hydration heat is large, and the internal and external temperature difference is easy to cause the concrete to shrink and crack. The layered spraying reduces the thickness of each layer of concrete, the cement hydration heat is evenly dissipated, and the shrinkage stress generated during the solidification process of each layer of concrete is small, and the shrinkage deformation of the previous layer can be constrained to a certain extent by the subsequent sprayed layer, thereby greatly reducing the possibility of cracks caused by shrinkage of the concrete, and ensuring the integrity of the concrete structure.

[0085] The layered spraying can make the construction personnel more conveniently control the flatness and thickness of the sprayed concrete. By setting the thickness marker before spraying each layer, the spraying thickness of each layer of concrete can be accurately controlled, thereby ensuring that the final sprayed concrete layer reaches the design requirements of flatness and thickness, and improving the construction quality of the tunnel lining.

[0086] During the layered spraying process, the construction personnel can check the spraying quality of the concrete in time after completing the spraying of each layer, such as whether there is missing spraying, excessive concrete rebound, etc., and can make timely repair and adjustment. If it is found that there is local non-compaction of the concrete in a layer, measures such as increasing the spraying amount can be taken during the construction of the subsequent sprayed layer to make up for it, so as to avoid the accumulation of problems affecting the overall construction quality.

[0087] After the initial spraying, the steel bar mesh is buried, and then the concrete is resprayed, so that the steel bar mesh can be better wrapped by the concrete, and the bonding force and gripping force between the steel bar mesh and the concrete are ensured. The steel bar mesh and the concrete work together to bear external force, thereby enhancing the overall bearing capacity and anti-deformation capacity of the tunnel lining.

[0088] For different surrounding rock conditions, the layered spraying process can flexibly adjust the spraying parameters and spraying sequence. In soft surrounding rock, the initial spraying can timely seal the surrounding rock to prevent weathering and relaxation of the surrounding rock, and then the re-spraying gradually increases the thickness of the concrete and improves the support strength; in hard rock surrounding rock, the thickness and number of layered spraying can be reasonably controlled according to the surface condition of the rock after blasting to ensure the support effect.

[0089] Specifically, in the embodiment of the present application, the construction parameters and layered spraying process are used to complete the concrete spraying construction, which comprises: In the spraying construction process, the spraying distance is determined according to the rock surface state.

[0090] Specifically, when the rock surface is dry, the spraying distance is controlled to be 1.0-1.2m, when the rock surface is wet, the spraying distance is controlled to be 0.8-1.0m, and when the rock surface is linear water, the spraying distance is controlled to be 0.6-0.8m.

[0091] The spraying angle is determined within a preset deviation, and the concave-convex rock surface is filled in the order of concave first and convex second.

[0092] Specifically, the 90° vertical spraying (allowing ±5° deviation) is maintained, and the concave-convex rock surface is filled in the order of concave first and convex second.

[0093] The wind pressure is adjusted in real time according to the spraying distance.

[0094] In the embodiment of the present application, the wind pressure is adjusted in real time according to the following formula: ; Wherein, P is the wind pressure (MPa), and D is the spraying distance (m).

[0095] In the embodiment of the present application, during the construction process, the spraying distance and the spraying angle can also be monitored and controlled in real time based on the cloud controller, which specifically comprises: The spraying distance is detected based on a laser range finder; The spraying angle is detected based on a sensor; The detection data is uploaded to a cloud control console.

[0096] In the embodiment of the present application, a laser range finder and a sensor can be added to the hydraulic wet spraying machine to complete the intelligent upgrading of the equipment and realize real-time monitoring of the construction state parameters (spraying distance and spraying angle).

[0097] S105, detecting the overbreak volume and recycling the rebound material.

[0098] In the embodiment of the present application, the overbreak volume is detected, which comprises: A Trimble SX10 three-dimensional scanner is used to scan the section after each cycle of blasting to generate an overbreak cloud chart; The overbreak volume is calculated by the PointCab software, and the overbreak position is marked to guide the supplementary spraying operation.

[0099] In the embodiment of the present application, the rebound material is recycled and utilized, comprising: Waterproof canvas is laid under the spraying surface, the lap joint is greater than or equal to 30 cm, the rebound material is screened to remove particles with a particle size greater than 10 mm, and then mixed into the freshly mixed concrete at a proportion of 10% to 15%; The amount of concrete used per vehicle is tracked by the RFID tag, and the actual rebound rate is calculated in combination with the amount of canvas collected.

[0100] The calculation formula is:

[0101] wherein, the rebound rate (%) is, the rebound material weight (kg) is, the actual sprayed concrete weight (kg) is.

[0102] Although the preferred embodiments of the present application have been described, those skilled in the art can make further changes and modifications to these embodiments once they know the basic inventive concept. Therefore, the appended claims are intended to cover all changes and modifications falling within the scope of the embodiments of the present application.

[0103] Finally, it should be noted that in this document, the terms such as first and second are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between such entities or operations. Moreover, the terms "comprises", "comprising", or any other variations thereof are intended to cover non-exclusive inclusions, so that a process, method, article, or terminal device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such a process, method, article, or terminal device. Without more limitations, the element defined by the statement "comprises a" does not exclude the presence of additional identical elements in the process, method, article, or terminal device including the element.

[0104] The construction method for reducing the loss of sprayed concrete in overlong underground excavation tunnels provided by the present application is described in detail above, and in this document, specific examples are applied to explain the principles and implementation modes of the present application. The above description of the embodiments is only used to help understand the method of the present application and its core idea; at the same time, for those skilled in the art, according to the idea of the present application, there will be changes in the specific implementation mode and application range; in view of the above, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A construction method for reducing the loss of shotcrete in ultra-long cut-and-cover tunnels, characterized in that, The method includes: Based on preset drilling and blasting parameters, the blasting effect is dynamically controlled through three-dimensional modeling and simulation. The rock mass fracture range under different charge amounts is simulated to determine the target drilling and blasting parameters. The preset drilling and blasting parameters include: contour line blasting hole offset, hole spacing, single hole charge amount, and plugging length. The contour line blasting hole offset is used to offset the contour line blasting hole towards the tunnel center to form a reserved buffer layer. Based on the target concrete performance indicators, the material mix proportions of the concrete are determined. The concrete materials include: base materials and nano-elasticity inhibitors. Complete the drilling and blasting according to the target drilling and blasting parameters; Based on engineering requirements, the construction parameters of the hydraulic wet spraying machine are determined, and the concrete spraying construction is completed based on the construction parameters and the layered spraying process. Over-excavation is detected, and rebound material is recycled.

2. The construction method for reducing shotcrete loss in ultra-long cut-and-cover tunnels according to claim 1, characterized in that, The method further includes determining the contour line burst hole offset using the following steps: For Class III to V surrounding rock, calculate the offset of the blast hole outline according to the offset calculation formula: ； in, Q is the offset, L is the charge per hole, k is the surrounding rock coefficient (0.8 for Class III, 1.0 for Class IV, and 1.2 for Class V), and S is the safety margin.

3. The construction method for reducing shotcrete loss in ultra-long cut-and-cover tunnels according to claim 1, characterized in that, Concrete performance indicators include: slump, initial setting time, and 28-day compressive strength. Base materials include: cement, sand, crushed stone, water-reducing agent, accelerator, and water. Based on the target concrete performance indicators, the concrete mix design is determined, including: The nano-elasticity resist agent and cement were dry-mixed at a ratio of 1:25 to obtain a mixed material. The mixed material and other basic materials are mixed and stirred according to the candidate preset ratio of the basic materials to obtain candidate concrete; Based on the slump, initial setting time, and 28-day compressive strength of the candidate concrete, the material mix proportions of the concrete that meet the target concrete performance indicators are determined.

4. The construction method for reducing shotcrete loss in ultra-long cut-and-cover tunnels according to claim 1, based on engineering requirements, determines the construction parameters of the hydraulic wet shotcrete machine, including: Determine the amount of concrete to be sprayed based on project requirements; The model, robotic arm length, and joint degrees of freedom of the hydraulic wet spraying machine are determined based on the amount of concrete sprayed.

5. The construction method for reducing shotcrete loss in ultra-long cut-and-cover tunnels according to claim 1, characterized in that, The layered spraying process includes: The initial spraying layer is completed within 2 hours after the blasting. The thickness of the initial spraying layer is 3-5 cm, and the wind pressure is 0.3 MPa. It is used to seal the rock surface cracks. The re-coating layer is completed by spraying in 2 to 3 times to the designed thickness, with a single layer thickness of 5 to 8 cm and an interval of 20 to 30 minutes between layers. The finishing layer is completed using a spiral superposition spraying method, with the nozzle advancing spirally at a speed of 0.3m / s to ensure that the surface flatness is ≤3cm / m.

6. The construction method for reducing shotcrete loss in ultra-long cut-and-cover tunnels according to claim 1, characterized in that, Concrete spraying is completed based on the aforementioned construction parameters and layered spraying process, including: During the spraying process, the spraying distance is determined based on the condition of the rock surface; Determine the spraying angle within the preset deviation, and fill the uneven rock surface in a sequence of first filling the concave and then filling the convex; Adjust the air pressure in real time according to the spray distance.

7. The construction method for reducing shotcrete loss in ultra-long cut-and-cover tunnels according to claim 6, characterized in that, The method further includes: The spray distance is detected using a laser rangefinder; The spray angle is detected based on a sensor; Upload the detection data to the cloud console.

8. The construction method for reducing shotcrete loss in ultra-long cut-and-cover tunnels according to claim 6, characterized in that, Adjust the air pressure in real time according to the injection distance and the following formula: ； Where P is the wind pressure (MPa) and D is the jet distance (m).

9. The construction method for reducing shotcrete loss in ultra-long cut-and-cover tunnels according to claim 1, characterized in that, The over-excavation volume is detected, including: Using a Trimble SX10 3D scanner, the cross-section is scanned after each blasting cycle to generate an over-excavation cloud map; The over-excavation volume is calculated using PointCab software, and the over-excavated areas are marked to guide the spraying operation.

10. The construction method for reducing shotcrete loss in ultra-long cut-and-cover tunnels according to claim 1, characterized in that, Recycling of spring-loaded materials includes: A waterproof tarpaulin is laid under the sprayed surface, with an overlap of ≥30cm at the joints. The rebound material is screened to remove particles larger than 10mm, and then mixed into the fresh concrete at a ratio of 10%~15%. The amount of concrete used in each truck is tracked by RFID tags, and the actual rebound rate is calculated by combining the amount collected by the canvas.

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