Hole slag back pressure backfilling and roadbed structure integrated construction process

Abstract

The invention discloses a hole slag back pressure backfilling and roadbed structure integrated construction technology, and belongs to the technical field of road construction. Comprising the following steps: grading and screening the tunnel hole slag into large / medium / fine three-level aggregate, and then crushing and recombining to form graded improved aggregate; constructing a multi-layer backfill structure of a base layer, a transition layer and a reinforcing layer; interface shear strength is achieved through the gravel-geogrid composite transition layer; adopting a vibratory roller to implement a static pressure and vibratory rolling combined process with adaptive levels; a coarse / fine-particle-size two-stage cement stabilized macadam layer is laid on the top to form a permeation drainage channel, and a transverse drainage blind pipe system is arranged to achieve three-dimensional drainage. According to the technology, the problems that in traditional hole slag backfilling, aggregate grading discreteness is large, shear failure is likely to be caused by sudden change of interlayer modulus, interlayer combination weakening is caused by uneven layered rolling energy transfer, and structure instability is caused by pore water pressure accumulation are solved, and hole slag resource utilization and roadbed structure performance collaborative improvement are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of road engineering waste recycling and roadbed structure construction, and specifically relates to a tunnel slag backpressure backfilling and roadbed structure integrated construction process. Background Art

[0002] In the field of road engineering, the traditional backfilling method of tunnel slag has significant technical defects. First, as a natural broken rock mass, the particle size distribution of tunnel slag is highly discrete. When directly backfilled, the proportion of coarse aggregate is too high and the grading continuity is poor, resulting in a large number of overhead pores inside the backfill body. After compaction, there is still local density unevenness. When the particle size of the coarse aggregate is too large, such as exceeding 200mm, conventional rolling equipment cannot effectively eliminate the contact gaps between the aggregates, which reduces the overall compression modulus of the backfill body and is prone to uneven settlement under the dynamic load of the vehicle. Although attempts have been made to adjust the particle size through mechanical crushing in the project, it is difficult to accurately control the aggregate grading curve with the existing crushing process. There are still problems of overlapping or discontinuities in the particle size range after crushing, which makes it difficult for the improved aggregate to form an effective skeleton dense structure.

[0003] Secondly, in traditional layered backfill construction, there is a lack of gradual transition design for the modulus differences between different material layers. When the backfill layer laid with a single-size modified aggregate is in direct contact with the upper roadbed structure layer, the stiffness difference at the interface is too large, and shear slip bands are easily generated under long-term traffic loads. The shear stress concentration phenomenon at the interface of this type of structure can increase the local deformation, and in severe cases, cause interlayer peeling damage. Although attempts were made to lay geotechnical materials between layers during construction, unidirectional geogrids are difficult to adapt to the three-dimensional stress state, and the bite effect with the crushed stone layer is insufficient, resulting in the interface shear strength failing to meet the design requirements.

[0004] In addition, conventional rolling technology lacks targeted regulation of the compaction characteristics of materials at different levels. Fixed rolling times and combinations are commonly used in construction, resulting in low compaction of the coarse aggregate layer due to insufficient vibration energy, and particle crushing of the fine aggregate layer due to excessive rolling. This difference directly weakens the mechanical continuity of the interlayer interface.

[0005] Finally, the existing drainage system design is difficult to effectively relieve the pore water pressure inside the backfill. Traditional horizontal blind pipes mostly use single-size filter media. During long-term use, the migration of fine particles will cause the filter layer to clog, and the permeability coefficient will decay over time. At the same time, the gradation of the anti-filter layer at the contact surface between the drainage pipe and the backfill is unreasonable, which is prone to contact scouring, resulting in the loss of soil around the pipe and the formation of cavities. More seriously, the closed layer at the top of the backfill lacks a gradient drainage structure. After precipitation infiltration, it is easy to form a stagnant water zone at the interface between the layers, resulting in high pore water pressure and significantly reducing the shear strength of the structure.

[0006] These problems jointly restrict the long-term stability of the tunnel slag backfill roadbed and become the key technical bottleneck restricting the resource utilization of tunnel slag. Summary of the invention

[0007] In order to solve the problems of large aggregate grading discreteness, sudden change of interlayer modulus easily leading to shear failure, uneven energy transfer of layered rolling leading to weakened interlayer bonding, and structural instability caused by accumulation of pore water pressure in the above-mentioned traditional tunnel slag backfill, the present invention provides an integrated construction process of tunnel slag backpressure backfill and roadbed structure, so as to achieve the synergy of tunnel slag resource utilization and improvement of roadbed structure performance.

[0008] In order to achieve these purposes and other advantages of the present invention, the present invention provides a tunnel slag backfill and roadbed structure integrated construction process, comprising the following steps: Step 1: Classify and screen the tunnel slag to separate large-size aggregate, medium-size aggregate and fine-size aggregate, and crush the large-size aggregate into a medium-size range and mix it with the medium-size aggregate to form a graded improved aggregate; Step 2: construct a multi-layer backfill structure on the roadbed base section, which includes, from bottom to top, a base layer of a mixture of improved aggregate and fine aggregate, a transition layer of pure improved aggregate, and a reinforcement layer of fine aggregate and cement, with a continuously changing modulus gradient formed between the layers; Step 3: before constructing the base layer, a crushed stone-geogrid composite transition layer is set at the contact surface between the base section and the backfill structure, and the interface shear reinforcement is achieved by alternately laying graded crushed stone layers and geogrids; Step 4: Use a vibratory roller to implement a differentiated rolling process for each layer of backfill structure, matching the combination of static pressure and vibration rolling and the number of rolling passes according to the layer material characteristics; Step 5: Lay a double-layer cement-stabilized gravel structure layer on the top of the backfill body, with the lower layer using a coarse-grained gravel cement mixture and the upper layer using a fine-grained gravel cement mixture to form a top-down infiltration drainage channel; Step 6: Set up a transverse drainage blind pipe system at intervals along the longitudinal direction of the roadbed, including a perforated pipe body, a permeable geotextile wrapping layer and a crushed stone filter layer at the bottom of the pipe to connect the drainage paths inside and outside the backfill body.

[0009] Preferably, in step 1, the tunnel slag is screened by a vibrating screen into coarse aggregate with a particle size greater than 200 mm, medium aggregate with a particle size of 80-200 mm, and fine aggregate with a particle size less than 80 mm; the coarse aggregate is crushed to a particle size of 80-200 mm by a jaw crusher and then mixed with the medium aggregate to form improved aggregate.

[0010] Preferably, the base layer of step 2 is made of improved aggregate and fine aggregate mixed in a volume ratio of 3:1, and the paving thickness is 500mm; the transition layer is made of improved aggregate alone and the paving thickness is 400mm; the reinforcement layer is made of fine aggregate and silicate cement mixed in a mass ratio of 15:1, and the paving thickness is 300mm.

[0011] Preferably, when the improved aggregate of the base layer is mixed with the fine aggregate, the proportion of particles with a particle size of 0.075-5 mm in the fine aggregate is controlled to be ≥ 65%, and a double-shaft forced mixer is used to stir at a speed of 45-50 r / min for 90-120 seconds, and the fluctuation range of the moisture content of the aggregate is controlled within ±0.3% during the stirring process; When paving the transition layer, a vibrating screen with an aperture of 80 mm is set in the hopper of the paver to screen out oversized particles with a particle size of >100 mm in real time. The travel speed of the paver and the speed of the spiral distributor are synchronously adjusted at a ratio of 1:2.5 to ensure that the aggregate packing density deviation is ≤5%; The fine aggregate and cement of the reinforcement layer are mixed by delayed graded feeding process, firstly 70% of the total amount of fine aggregate is added and dry mixed with cement for 20-30 seconds, then the remaining 30% of fine aggregate is added and atomized and sprayed with mixing water for 40-60 seconds, and the discharge temperature of the mixture is controlled within the range of 25-35°C; The paving thickness of each structural layer is dynamically controlled. The base layer uses an infrared elevation scanner to detect thickness deviation every 5m section. The transition layer uses a hydraulic sensor on the paver scraper to adjust the paving height in real time. The reinforcement layer uses an inserted density meter to back-calculate the compaction thickness. The allowable thickness error is ≤±3%.

[0012] Preferably, the crushed stone-geogrid composite transition layer of step 3 comprises: a crushed stone transition layer, which is alternately paved with graded crushed stone with a particle size of 5-10 mm and biaxially oriented polypropylene geogrid, and a layer of geogrid is laid after each 50 mm thick crushed stone layer, with a total thickness of 100 mm.

[0013] Preferably, the rolling process of step 4 includes: layered compaction using a vibratory roller with a deadweight ≥ 18t, the base layer is subjected to one static compaction followed by four vibration compactions, the transition layer is subjected to two static compactions followed by three vibration compactions, the reinforcement layer is subjected to three static compactions followed by two vibration compactions, and adjacent wheel tracks maintain an overlapping width of 300mm.

[0014] Preferably, the operating parameters of the vibratory roller are dynamically controlled according to the layers, the base layer adopts a strong vibration mode with an amplitude of 2.0-2.5 mm and a vibration frequency of 28-32 Hz, the transition layer adopts a medium vibration mode with an amplitude of 1.5-2.0 mm and a vibration frequency of 25-28 Hz, and the reinforcement layer adopts a weak vibration mode with an amplitude of 0.8-1.2 mm and a vibration frequency of 20-25 Hz; When rolling each layer, the roller speed is controlled at 2.0-2.5km / h for the base layer, 2.5-3.0km / h for the transition layer, and 3.0-3.5km / h for the reinforcement layer. The interval between rolling operations of adjacent layers is controlled at ≤30min for the base layer, ≤20min for the transition layer, and ≤10min for the reinforcement layer. The overlapping width of the wheel tracks is adjusted according to the maximum particle size of the layered aggregates. The overlapping width of the base layer is set at 1.5 times the maximum particle size of the aggregates, the overlapping width of the transition layer is set at 1.2 times the maximum particle size of the aggregates, and the overlapping width of the reinforcement layer is set at 0.8 times the maximum particle size of the aggregates.

[0015] Preferably, in the double-layer cement-stabilized gravel layer of step 5, the lower layer is paved with gravel of 20-30 mm in diameter and cement mixture with a thickness of 120 mm, and the upper layer is paved with gravel of 5-10 mm in diameter and cement mixture with a thickness of 80 mm.

[0016] Preferably, in the lateral drainage blind pipe system described in step 6, lateral drainage blind pipes are buried every 20m along the longitudinal direction of the roadbed. The blind pipes are made of 100 mm diameter PVC perforated pipes, covered with 300g / m² permeable geotextile, and a 50mm thick crushed stone filter layer with a particle size of 10-20mm is filled between the bottom of the pipe and the backfill body.

[0017] Preferably, the buried inclination angle of the transverse drainage blind pipe is controlled at 3-5°, the axial center line of the pipe body forms an angle of 15-20° with the transverse slope direction of the roadbed, the perforation rate of the pipe is 8-10 holes / m² and the hole diameter is 5-8mm; The crushed stone filter layer adopts a double-layer graded structure, the lower layer is filled with 30mm thick coarse crushed stone with a particle size of 15-20mm, the upper layer is filled with 20mm thick fine crushed stone with a particle size of 10-15mm, and 200g / m² polyester needle-punched geotextile is laid between the layers as an anti-filtration isolation layer; The wrapping overlap width of the permeable geotextile is ≥150mm, the overlap seam is processed by hot-melt welding process, the welding temperature is set to 280-300°C, and U-shaped stainless steel nails are set at intervals of 500mm on the top of the pipe body to fix the geotextile; A three-way joint is set at the connection between the two ends of the drainage blind pipe and the longitudinal drainage ditch, a stainless steel filter with a pore size of 2mm is pre-embedded in the inner wall of the joint, and a double-layer permeable geotextile is wrapped on the outer wall of the joint to form a 20mm thick anti-seepage buffer layer; After the blind pipe is installed, an air tightness test is carried out. The pressure drop does not exceed 5% after maintaining the air pressure of 0.15MPa for 10 minutes, and the permeability coefficient attenuation rate of the permeable geotextile is controlled at ≤15% during the construction period.

[0018] The present invention has at least the following beneficial effects: 1. The present invention uses a vibrating screen to divide tunnel slag into three particle sizes (>200mm / 80-200mm / <80mm) and crush and reassemble, establishes a material gradation control mechanism, and effectively solves the problem of aggregate gradation out of control caused by the large discreteness of tunnel slag particle size.

[0019] 2. The present invention forms a variable modulus system through a base layer (improved aggregate + fine aggregate), a transition layer (pure improved aggregate), and a reinforcement layer (fine aggregate + cement), and combines the interface treatment of a crushed stone transition layer (graded crushed stone + geogrid) to effectively solve the problem of shear failure at the interface between traditional backfill and roadbed and sudden change in interlayer modulus.

[0020] 3. The present invention adopts a ≥18t roller for layered compaction for different layers. The base layer is subjected to one static compaction followed by four vibration rollings, the transition layer is subjected to two static compactions followed by three vibration rollings, the reinforcement layer is subjected to three static compactions followed by two vibration rollings, and the adjacent wheel tracks maintain an overlapping width of 300mm, which effectively solves the problem of weakened interlayer bonding caused by mismatched compaction energy when the mixture is layered rolled.

[0021] 4. The present invention forms a coordinated drainage channel through a lateral drainage blind pipe (PVC perforated pipe + permeable geotextile + crushed stone filter layer) and a cement-stabilized crushed stone layer (different particle sizes in the upper and lower layers), effectively solving the stability degradation problem caused by the accumulation of pore water pressure inside the backpressure backfill body.

[0022] 5. The above-mentioned means of the present invention work together to break through the three technical obstacles of grading imbalance, weak interface and uneven compaction in traditional tunnel slag backfilling. Through the three-level protection of material filtration, pipeline drainage and structural drainage, the impact of hydrological environment is eliminated, and the coordinated improvement of tunnel slag resource utilization and roadbed structure performance is jointly achieved.

[0023] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a process framework diagram of the integrated construction process of the slag backfilling and roadbed structure of the present invention; Figure 2 It is a schematic diagram of the roadbed cross-section structure of the present invention.

[0025] Among them, there are original soil roadbed 10, crushed stone geogrid composite transition layer 20, base layer 30, transition layer 40, reinforcement layer 50, cement stabilized crushed stone structure layer 60, and drainage blind pipe 70. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with embodiments so that those skilled in the art can implement the invention with reference to the description.

[0027] As shown in Figures 1 and 2, a construction process for integrating slag backfilling and roadbed structure includes the following steps: The tunnel slag is screened through a vibrating screen into coarse aggregate (large-size aggregate) with a particle size greater than 200mm, medium aggregate (medium-size aggregate) with a particle size of 80-200mm, and fine aggregate (fine-size aggregate) with a particle size less than 80mm; the coarse aggregate is crushed into a particle size of 80-200mm by a jaw crusher and then mixed with the medium aggregate to form improved aggregate; The base section of the original soil roadbed is backfilled layer by layer from bottom to top. The base layer is made of improved aggregate and fine aggregate mixed in a volume ratio of 3:1, with a paving thickness of 500mm; the transition layer is made of improved aggregate alone with a paving thickness of 400mm; the reinforcement layer is made of fine aggregate and silicate cement mixed in a mass ratio of 15:1, with a paving thickness of 300mm, so that a continuously changing modulus gradient is formed between the layers; Before constructing the base layer, a gravel geogrid composite transition layer is laid on the surface of the original soil roadbed base section (the contact surface with the backfill structure), which is alternately laid with graded gravel with a particle size of 5-10mm and biaxially stretched polypropylene geogrid. After each 50mm thick gravel layer is laid, a layer of geogrid is laid, with a total thickness of 100mm. Use a 18t vibratory roller to compact the layers in layers. The base layer is compacted once and then vibrated four times. The transition layer is compacted twice and then vibrated three times. The reinforcement layer is compacted three times and then vibrated twice. The adjacent wheel tracks are overlapped by 300mm. The cement-stabilized crushed stone layer is paved in two layers on the top surface of the compacted backfill body. The lower layer is paved with 20-30mm crushed stone and cement mixture with a thickness of 120mm, and the upper layer is paved with 5-10mm crushed stone and cement mixture with a thickness of 80mm. Transverse drainage blind pipes are buried every 20m along the longitudinal direction of the roadbed. The blind pipes are made of 100mm diameter PVC perforated pipes, covered with 300g / m² permeable geotextile, and a 50mm thick 10-20mm crushed stone filter layer is filled between the bottom of the pipe and the backfill body.

[0028] Specifically, for the slag classification and improved aggregate preparation, a double-layer vibrating screen can be used for particle size classification, with the first layer of screen aperture set to 200mm and the second layer of screen aperture set to 80mm. When the coarse aggregate is crushed by a jaw crusher, the crusher discharge port is adjusted to 80mm, and the crushed aggregate is sent to the mixing bin through a conveyor belt to mix with the medium aggregate. The mixing ratio of the improved aggregate is measured by volume, and a volumetric batching machine can be used to control the feeding amount of coarse aggregate and medium aggregate. The vibrating screen can use the circular vibrating screen model 2YK2460 with a processing capacity of 200-300t / h. The jaw crusher can use the PE-600×900 type, with a feed port size of 600×900mm and a discharge port adjustment range of 75-200mm.

[0029] For multi-layer backfill structure and modulus gradient construction, the volume ratio of the base layer can be controlled by using a loader and a belt scale for measurement. The amount of fine aggregate added is 0.33m³ of fine aggregate per cubic meter of improved aggregate. When paving the transition layer, the dump truck (8) unloads the material into the paver hopper. The paver model can be ABG8620, with a maximum paving width of 12m. The reinforcement layer is mixed using a forced mixer, and the cement content is added at 6.25% of the total mass. The mixing time is not less than 120 seconds. The thickness control of each structural layer: the base layer elevation is measured using a laser level, the transition layer is controlled by the automatic leveling system of the paver, and the reinforcement layer uses an inserted density meter to reversely calculate the compacted thickness.

[0030] For the layered differentiated compaction process, the roller uses an 18t double steel wheel vibratory roller, model XD142, with an exciting force of 290kN. Rolling parameter settings: static compaction speed of base layer 2.0km / h, vibration compaction speed 2.5km / h; static compaction speed of transition layer 2.5km / h, vibration compaction speed 3.0km / h; static compaction speed of reinforcement layer 3.0km / h, vibration compaction speed 3.5km / h. The overlapping control of adjacent wheel tracks uses the scale mark line on the side of the roller steel wheel to align with the edge of the previous rolling belt. The compaction degree is tested by the sand filling method, and 6 points are tested every 1000㎡.

[0031] For transverse drainage blind pipes, in the horizontal direction, several transverse drainage blind pipes are set up along the longitudinal center line of the roadbed at intervals of 20m; the horizontal projection length of the blind pipe runs through the entire roadbed width, and both ends extend 50cm into the longitudinal drainage ditch of the slope; adjacent blind pipes are arranged in parallel, and the plane position deviation is controlled within the range of ±10cm. In the vertical direction, the transverse drainage blind pipe is arranged at the bottom of the cement-stabilized gravel layer, 30cm away from the top surface of the reinforcement layer; the first blind pipe is set 1.5m away from the foot line of the roadbed slope, and the last blind pipe is ≤10m away from the end of the roadbed. When constructing the transverse drainage blind pipe, a 10cm thick seepage channel is reserved at the bottom of the cement-stabilized gravel layer (20-30mm coarse aggregate layer); a groove is opened on the top surface of the reinforcement layer (fine aggregate cement layer), the groove depth is 15cm, and a crushed stone filter layer is laid at the bottom of the groove. The two ends of the transverse drainage blind pipe are connected to the longitudinal drainage ditch through 135° elbows, and the connection is 20cm higher than the bottom of the ditch.

[0032] This implementation method achieves a continuous grade ratio of improved aggregate of more than 95% through particle size classification control, and the interlayer modulus gradient increases the interface shear strength to 150kPa. The alternating paved gravel-geogrid structure increases the interface friction coefficient to 0.65. The differentiated compaction process controls the standard deviation of the compaction degree of each structural layer within 2%, and the permeability coefficient of the drainage blind pipe system is maintained at 1×10⁻³cm / s, effectively controlling the pore water pressure below 30kPa.

[0033] Further, in another embodiment, when the modified aggregate of the base layer is mixed with the fine aggregate, the proportion of particles with a particle size of 0.075-5 mm in the fine aggregate is controlled to be ≥ 65%, and a double-shaft forced mixer is used to stir at a speed of 45-50 r / min for 90-120 seconds, and the fluctuation range of the moisture content of the aggregate is controlled within ±0.3% during the stirring process; When paving the transition layer, a vibrating screen with an aperture of 80 mm is set in the hopper of the paver to screen out oversized particles with a particle size of >100 mm in real time. The travel speed of the paver and the speed of the spiral distributor are synchronously adjusted at a ratio of 1:2.5 to ensure that the aggregate packing density deviation is ≤5%; The fine aggregate and cement of the reinforcement layer are mixed by delayed graded feeding process, firstly 70% of the total amount of fine aggregate is added and dry mixed with cement for 20-30 seconds, then the remaining 30% of fine aggregate is added and atomized and sprayed with mixing water for 40-60 seconds, and the discharge temperature of the mixture is controlled within the range of 25-35°C; The paving thickness of each structural layer is dynamically controlled. The base layer uses an infrared elevation scanner to detect thickness deviation every 5m section. The transition layer uses a hydraulic sensor on the paver scraper to adjust the paving height in real time. The reinforcement layer uses an inserted density meter to back-calculate the compaction thickness. The allowable thickness error is ≤±3%.

[0034] Specifically, for the proportioning and mixing control of the base layer mixture, a double-shaft forced mixer can be used for material mixing. The equipment is equipped with a speed sensor and a timing controller. Fine aggregates must be screened through a standard square hole sieve before entering the site. The screening ratio of particles with a particle size of 0.075-5mm is determined through a screening test, and the screen residue is controlled not to exceed 35%. When the mixer speed is set to 45 rpm, the mixing time is set to 110 seconds; when the speed is increased to 50 rpm, the mixing time is shortened to 95 seconds. The moisture content of the aggregate is tested using an inserted moisture meter. Three points are tested for each batch of mixture, and the allowable range of moisture content fluctuation is 5.2%-5.8%. A belt conveyor can be installed at the mixer outlet to transport the mixture directly to the paving surface.

[0035] During the paving of the transition layer, the ABG7820 paver can be selected. A vibrating screen with an aperture of 80 mm is installed at the entrance of the hopper. The screen inclination angle is set to 15° and the vibration frequency is adjusted to 25 Hz. The matching relationship between the spiral distributor speed and the paver travel speed is: when the paving speed is set to 1.5 m / min, the distributor speed is automatically adjusted to 3.75 rpm. The bulk density is detected using a nuclear density meter, and 2 points are detected every 10 m section. When the density deviation exceeds 5%, the paving speed adjustment program is automatically triggered. Oversized aggregate is discharged through the lateral discharge port, and the discharge port height is set to 300 mm from the paving surface.

[0036] The reinforcement layer mixing operation uses a JS750 forced mixer equipped with a material metering bin and an atomizing spray system. The first feeding amount is measured at 70% of the total amount of fine aggregate, and the dry mixing stage time is set to 25 seconds. After the second feeding, the mixing water is sprayed through a 0.3mm aperture atomizing nozzle, and the water pressure is controlled at 0.4-0.6MPa. The temperature of the mixture is monitored by an infrared thermometer. When the discharge temperature is lower than 25℃, the heating device is automatically started, and when it is higher than 35℃, the spray cooling system is started. Before loading the transport vehicle, a 2mm thick plastic insulation film can be pre-paved inside the carriage.

[0037] In the structural layer thickness control system, the base layer detection can use the Trimble SPS986 infrared height scanner, the scanning frequency is set to 10Hz, and three-dimensional point cloud data is generated every 5 meters. The transition layer paver scraper hydraulic sensor range is set to 0-500mm, and the signal sampling interval is 0.5 seconds. The reinforcement layer density detection uses the MC-3 insertion density meter, the probe penetration speed is controlled to 20mm / s, and the density value is recorded every 50mm penetration. After the thickness exceeds the standard area, a small tamping machine is used for local pressure treatment, and the number of pressure replenishment shall not exceed 3 times.

[0038] This implementation method eliminates the risk of mixture segregation by limiting the proportion of key particle size ranges of fine aggregate and accurately controlling the moisture content, ensuring the stability of the volume ratio of 3:1; a vibrating screen is set in conjunction with a speed-rotation speed linkage mechanism to eliminate the density unevenness caused by the blockage of oversized aggregate during traditional paving; staged feeding is combined with atomized water spraying to solve the problem of early agglomeration of fine aggregate and cement, and temperature control ensures the uniformity of the hydration reaction rate; the infrared scanning-hydraulic sensing-density back-calculation combination technology realizes full-layer thickness closed-loop control to solve the lag problem of traditional single detection methods.

[0039] This implementation method makes the uniformity index of the base layer mixture reach above 0.85, and the residual amount of oversized aggregate in the transition layer is reduced to below 0.3%. The cement coverage rate of the reinforcement layer is increased to 93%-95%, and the temperature control shortens the initial setting time deviation to less than 8 minutes. The thickness dynamic monitoring system improves the paving accuracy to 98.5% and reduces the rework rate to below 1.2%. The interface bonding strength of each structural layer is increased to 1.5MPa, and the standard deviation of the 28-day compressive strength is controlled within 0.3MPa.

[0040] Further, in another embodiment, the operating parameters of the vibratory roller in step 4 are dynamically controlled by layer, the base layer adopts a strong vibration mode with an amplitude of 2.0-2.5 mm and a vibration frequency of 28-32 Hz, the transition layer adopts a medium vibration mode with an amplitude of 1.5-2.0 mm and a vibration frequency of 25-28 Hz, and the reinforcement layer adopts a weak vibration mode with an amplitude of 0.8-1.2 mm and a vibration frequency of 20-25 Hz; When rolling each layer, the roller speed is controlled at 2.0-2.5km / h for the base layer, 2.5-3.0km / h for the transition layer, and 3.0-3.5km / h for the reinforcement layer. The interval between rolling operations of adjacent layers is controlled at ≤30min for the base layer, ≤20min for the transition layer, and ≤10min for the reinforcement layer. The overlapping width of the wheel tracks is adjusted according to the maximum particle size of the layered aggregates. The overlapping width of the base layer is set at 1.5 times the maximum particle size of the aggregates, the overlapping width of the transition layer is set at 1.2 times the maximum particle size of the aggregates, and the overlapping width of the reinforcement layer is set at 0.8 times the maximum particle size of the aggregates.

[0041] Specifically, the vibratory roller can use the XCMG XD142 double-steel-wheel roller, which is equipped with a stepless amplitude adjustment device and a variable frequency vibration system. When the vibration parameters of the base layer are set to an amplitude of 2.3mm and a frequency of 30Hz, the steel wheel ground pressure reaches 580kPa; the transition layer is adjusted to an amplitude of 1.8mm and a frequency of 26Hz, and the pressure drops to 450kPa; the reinforcement layer uses an amplitude of 1.0mm and a frequency of 22Hz, and the pressure is controlled at 300kPa. The roller operation panel sets the parameter storage module, which can preset three sets of vibration mode parameters, and the mode switching response time does not exceed 5 seconds. A temperature sensor is installed at the bearing seat of the vibration shaft, and the cooling system is automatically started when the temperature exceeds 85°C.

[0042] During rolling operation, the base layer speed is set at 2.2km / h, the transition layer speed is increased to 2.8km / h, and the reinforcement layer is maintained at 3.2km / h. Time control uses GPS timing module and construction management software linkage, and the layer conversion interval is set as: 25 minutes for base layer, 18 minutes for transition layer, and 8 minutes for reinforcement layer. The roller is equipped with a speed sensor to feed back vehicle speed data to the control terminal in real time. When the speed deviation exceeds ±0.3km / h, an audible and visual alarm is triggered. The hot joint process is used for the connection of adjacent layer operations, and the number of times of filling the joint is increased by 1.

[0043] Wheel track overlap control uses the aggregate maximum particle size detection data for dynamic adjustment. When the maximum particle size of the base layer aggregate is 100mm, the overlap width is set to 150mm; when the maximum particle size of the transition layer aggregate is 80mm, the overlap is 96mm; when the maximum particle size of the reinforcement layer aggregate is 50mm, the overlap is 40mm. A laser rangefinder sensor is installed on the edge of the steel wheel to monitor the distance from the previous rolling belt in real time, with a control accuracy of ±10mm. The roller is equipped with a GNSS positioning system to record the rolling track and generate a coverage cloud map. Areas with a coverage rate below 95% are automatically marked for re-rolling positions.

[0044] In this implementation method, a functional relationship is established between the amplitude / frequency combination and the aggregate particle size of each layer (base layer>80mm, transition layer 80-200mm, reinforcement layer<80mm). The coarse aggregate layer uses high-frequency strong vibration to eliminate pores, and the fine aggregate layer uses low-frequency weak vibration to prevent crushing. The contradiction between the rolling energy transfer efficiency and the interlayer bonding timeliness is resolved through the coordinated control of the velocity gradient (the slow enhancement time of the bottom layer) and the interval time (based on the material stress relaxation characteristics). A linear proportional relationship between the overlap width and the aggregate particle size is established (1.5 / 1.2 / 0.8 times), achieving a balance between full coverage rolling of the coarse aggregate layer and efficient operation of the fine aggregate layer.

[0045] This implementation method increases the vibration energy transfer efficiency of the base layer to 75%, reduces the standard deviation of the compaction degree of the transition layer to 2.1%, and controls the aggregate crushing rate of the reinforcement layer to below 3%. The speed coordination control reduces the permeability coefficient of the interlayer interface to 5×10⁻ 6cm / s, and interval time management increased the interlayer bonding strength by 18%-22%. The dynamic overlapping algorithm increased rolling efficiency by 25%, reduced energy consumption by 12%, and stabilized the track coverage rate at more than 97.5%. The compaction uniformity index of each layer reached 0.88-0.92, and the 28-day rebound modulus deviation did not exceed 5%.

[0046] Further, in another embodiment, during the rolling process of the base layer, when it is detected that the proportion of particles with a particle size of >100 mm in the modified aggregate exceeds 35%, the amplitude compensation mechanism is automatically triggered to increase the amplitude to 1.2-1.5 times the standard value; When rolling the reinforcement layer, the moisture content of fine aggregate and cement mixture is monitored in real time. When the moisture content fluctuates beyond the set value ±1.5%, the vibration frequency is adjusted to decrease by 10-15% and the static pressing time is extended by 20-30%. The dynamic adjustment of the wheel track overlap width is achieved through the GNSS positioning system, and the distance control error between the edge of the rear wheel of the roller and the edge of the previous rolling belt is ≤20mm.

[0047] Specifically, in the base layer rolling operation, a laser particle size analyzer installed at the front end of the roller can be used to detect the aggregate particle size distribution in real time, with a detection frequency of once every 5-meter section scan. When the proportion of particles with a particle size greater than 100mm in the improved aggregate reaches 36%, the roller control unit automatically increases the amplitude from the standard value of 2.3mm to 2.8mm, and the corresponding exciting force increases from 290kN to 348kN. The particle size detection data is sent to the construction monitoring center through the wireless transmission module, and the compensation action response time does not exceed 3 seconds. The amplitude adjustment mechanism is installed at the eccentric block of the vibration shaft and is driven by a servo motor with an adjustment stroke accuracy of ±0.1mm.

[0048] When rolling the reinforcement layer, an insertable moisture sensor can be used to monitor the moisture content of the mixture. The sensor probe is 150mm long and buried 100mm deep. When the moisture content is detected to fluctuate from the design value of 5.0% to 6.6%, the vibration frequency is automatically adjusted from 22Hz to 19Hz, and the static pressure time is extended from 30 seconds to 39 seconds. The parameter adjustment command is transmitted to the hydraulic control system of the roller through the CAN bus, and the actuator response delay is less than 1 second. The mixing water addition record is linked to the moisture content detection data in real time, and abnormal fluctuation data automatically triggers the mixing station adjustment program.

[0049] The wheel track overlap control uses the Trimble SPS986 GNSS positioning system. The receiver is installed on the top bracket of the roller, and the positioning accuracy is ±10mm in the horizontal direction. Ultrasonic distance sensors are installed on the edge of the rear wheel of the roller to measure the actual distance from the previous rolling belt. When the distance deviation is detected to reach 22mm, the steering hydraulic cylinder automatically fine-tunes the angle by 0.5°, and the correction process is completed within 2 seconds. The rolling track data is stored in the on-board industrial computer, and the plane position error of each wheel track can be traced when generating the construction electronic file.

[0050] This implementation method controls the amplitude in real time through the proportion of aggregate particle size to solve the problem of under-compaction in areas where coarse aggregate is concentrated; establishes an inverse adjustment relationship between moisture content and vibration energy to prevent spring phenomenon caused by over-wet mixture; and uses GNSS high-precision positioning to ensure the execution accuracy of overlapping width and eliminate manual operation deviations.

[0051] This implementation method reduces the compaction standard deviation of the coarse aggregate concentrated area of ​​the base layer from 8.2% to 3.5%, and increases the compaction energy utilization rate under amplitude compensation conditions by 18%-22%. The linkage control of moisture content reduces the incidence of surface cracks in the reinforcement layer from 15% to 4%, and the adjustment of vibration frequency controls the crushing rate of fine aggregate within 2%. The GNSS positioning system increases the pass rate of wheel track overlap width from 82% to 98%, reduces the area of ​​leaking pressure to 0.5㎡ / km, and shortens the time to generate the rolling coverage cloud map to 10 minutes / km.

[0052] Further, in another embodiment, the buried inclination angle of the transverse drainage blind pipe in step 6 is controlled at 3-5°, the axial center line of the pipe body forms an angle of 15-20° with the transverse slope direction of the roadbed, the perforation rate of the pipe is 8-10 holes / m² and the hole diameter is 5-8 mm; The crushed stone filter layer adopts a double-layer graded structure, the lower layer is filled with 30mm thick coarse crushed stone with a particle size of 15-20mm, the upper layer is filled with 20mm thick fine crushed stone with a particle size of 10-15mm, and 200g / m² polyester needle-punched geotextile is laid between the layers as an anti-filtration isolation layer; The wrapping overlap width of the permeable geotextile is ≥150mm, the overlap seam is processed by hot-melt welding process, the welding temperature is set to 280-300°C, and U-shaped stainless steel nails are set at intervals of 500mm on the top of the pipe body to fix the geotextile; A three-way joint is set at the connection between the two ends of the drainage blind pipe and the longitudinal drainage ditch, a stainless steel filter with a pore size of 2mm is pre-embedded in the inner wall of the joint, and a double-layer permeable geotextile is wrapped on the outer wall of the joint to form a 20mm thick anti-seepage buffer layer; After the blind pipe is installed, an air tightness test is carried out. The pressure drop does not exceed 5% after maintaining the air pressure of 0.15MPa for 10 minutes, and the permeability coefficient attenuation rate of the permeable geotextile is controlled at ≤15% during the construction period.

[0053] Specifically, the drainage blind pipe can use a PVC-U perforated pipe with an outer diameter of 110mm, and the openings on the pipe wall are arranged in a diamond pattern with 8 holes / m² and a hole diameter of 6mm. When burying the drainage blind pipe, a Leica TS16 total station is used to control the spatial position, and the longitudinal inclination is set to 4°, so that the water inlet end is high and the water outlet end is low, and the drainage blind pipe forms an angle of 18° with the cross slope direction of the roadbed. The construction of the gravel filter layer adopts the layered paving method, with 30mm thick basalt gravel with a particle size of 18mm on the lower layer and 20mm thick granite gravel with a particle size of 12mm on the upper layer. The polyester needle-punched geotextile laid between the layers has a gram weight of 200g / m² and a width of 2m. The surface of the lower gravel layer is covered by manual paving, and the overlap width is maintained at 200mm. The SW850 small paver can be used for gravel paving, and the paving speed is controlled at 1.2m / min.

[0054] The geotextile wrapping construction adopts hot melt welding technology. The HD-500 automatic crawling welder can be used. The welding temperature is set to 290℃ and the welding speed is adjusted to 0.8m / min. Two parallel welds are set at the lap joint with a spacing of 30mm. The U-shaped stainless steel nails are made of 304 material, with a nail foot length of 50mm and a plum blossom shape arranged at the top of the pipe with an interval of 500mm. The edge of the geotextile is treated with secondary welding with a handheld hot air gun, and the welding temperature is controlled in the range of 280-300℃. The permeability coefficient of the geotextile after construction is tested using a constant head permeameter, and the water temperature is controlled at 20±2℃.

[0055] A DN100 tee joint is installed at the connection between the drainage blind pipe and the longitudinal drainage ditch, and a 316L stainless steel filter is embedded inside the joint with a mesh size of 2mm×2mm. The outside of the joint is wrapped with two layers of 300g / m² polyester filament geotextile, with an overlap width of 300mm, and is fixed by sewing with polyester thread. For air tightness testing, a DWT-02 pipe pressure tester can be used. After pressurizing to 0.15MPa, the pressure is stabilized for 10 minutes, and the allowable pressure drop value is 7.5kPa. The permeability coefficient attenuation test is completed within 24 hours after construction. The sampling size is 300mm×300mm, and the test head difference is maintained at 1m.

[0056] This implementation method uses a composite angle setting of inclination and included angle to enable the pipe body to simultaneously receive longitudinal seepage and lateral infiltration water, thereby improving drainage efficiency by more than 40%; a double-layer crushed stone + geotextile isolation layer forms a particle size gradient filtration, effectively intercepting fine particles with a particle size of less than 0.075mm and maintaining a permeability coefficient of ≥1×10⁻³cm / s; a combination of hot-melt welding and mechanical anchoring ensures the sealing of the package, solving the problem of filter material loss caused by loosening due to the traditional binding method; the three-way joint is designed with a built-in filter screen and an outer buffer layer to eliminate the risk of contact scouring and damage to the pipe end; dual-index detection of air tightness and permeability coefficient attenuation rate enables full control of drainage performance.

[0057] This implementation method makes the drainage blind pipe water collection efficiency reach 0.8L / (s·m), and the permeability coefficient of the double-layer gravel filter layer remains ≥5×10⁻³cm / s. The hot-melt welding process makes the geotextile joint peel strength ≥1.2kN / m, and the U-nail fixing point pull-out force ≥500N. The three-way joint anti-seepage layer makes the interface leakage less than 0.01L / min, and the air tightness test pass rate is increased to 98%. The permeability coefficient attenuation rate during the construction period is controlled at 12%-14%, which is more than 50% lower than the traditional process, and the drainage system has a long service life.

[0058] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and the embodiments. They can be applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily realized.

Claims

1. A construction process integrating slag backfilling and roadbed structure, characterized in that: The following steps are involved: Step 1: Classify and screen the tunnel slag to separate large-size aggregate, medium-size aggregate and fine-size aggregate, and crush the large-size aggregate into a medium-size range and mix it with the medium-size aggregate to form a graded improved aggregate; Step 2: construct a multi-layer backfill structure on the roadbed base section, which includes, from bottom to top, a base layer of a mixture of improved aggregate and fine aggregate, a transition layer of pure improved aggregate, and a reinforcement layer of fine aggregate and cement, with a continuously changing modulus gradient formed between the layers; Step 3: before constructing the base layer, a crushed stone-geogrid composite transition layer is set at the contact surface between the base section and the backfill structure, and the interface shear reinforcement is achieved by alternately laying graded crushed stone layers and geogrids; Step 4: Use a vibratory roller to implement a differentiated rolling process for each layer of backfill structure, matching the combination of static pressure and vibration rolling and the number of rolling passes according to the layer material characteristics; Step 5: Lay a double-layer cement-stabilized gravel structure layer on the top of the backfill body, with the lower layer using a coarse-grained gravel cement mixture and the upper layer using a fine-grained gravel cement mixture to form a top-down infiltration drainage channel; Step 6: Set up a transverse drainage blind pipe system at intervals along the longitudinal direction of the roadbed, including a perforated pipe body, a permeable geotextile wrapping layer and a crushed stone filter layer at the bottom of the pipe to connect the drainage paths inside and outside the backfill body.

2. The integrated construction process of slag backfilling and roadbed structure according to claim 1 is characterized in that: In step 1, the tunnel slag is screened by a vibrating screen into coarse aggregate with a particle size greater than 200 mm, medium aggregate with a particle size of 80-200 mm, and fine aggregate with a particle size less than 80 mm; the coarse aggregate is crushed to a particle size of 80-200 mm by a jaw crusher and then mixed with the medium aggregate to form improved aggregate.

3. The integrated construction process of slag backfilling and roadbed structure according to claim 1 or 2, characterized in that: The base layer of step 2 is made of improved aggregate and fine aggregate mixed in a volume ratio of 3:1, with a paving thickness of 500mm; the transition layer is made of improved aggregate alone with a paving thickness of 400mm; the reinforcement layer is made of fine aggregate and silicate cement mixed in a mass ratio of 15:1, with a paving thickness of 300mm.

4. The integrated construction process of slag backfilling and roadbed structure according to claim 3 is characterized in that: When the improved aggregate of the base layer is mixed with the fine aggregate, the proportion of particles with a particle size of 0.075-5mm in the fine aggregate is controlled to be ≥65%, and a double-shaft forced mixer is used to stir at a speed of 45-50r / min for 90-120 seconds. During the mixing process, the fluctuation range of the aggregate moisture content is controlled within ±0.3%; When paving the transition layer, a vibrating screen with an aperture of 80 mm is installed in the hopper of the paver to screen out oversized particles with a particle size of >100 mm in real time. The paver travel speed and the spiral feeder speed are synchronously adjusted at a ratio of 1:2.5 to ensure that the aggregate packing density deviation is ≤5%; The fine aggregate and cement of the reinforcement layer are mixed by delayed graded feeding process. First, 70% of the total amount of fine aggregate is added and dry mixed with cement for 20-30 seconds, and then the remaining 30% of fine aggregate is added and sprayed with atomized mixing water for 40-60 seconds. The discharge temperature of the mixture is controlled within the range of 25-35℃. An infrared height scanner is used to detect thickness deviation of the base layer every 5m section. The transition layer's paving height is controlled in real time by the hydraulic sensor of the paver scraper. An inserted density meter is used to reversely calculate the compaction thickness of the reinforcement layer. The allowable error of the thickness is ≤±3%.

5. The integrated construction process of slag backfilling and roadbed structure according to claim 1 is characterized in that: The gravel-geogrid composite transition layer in step 3 is alternately paved with graded gravel with a particle size of 5-10 mm and biaxially stretched polypropylene geogrid. A layer of geogrid is laid after each 50 mm thick gravel layer, with a total thickness of 100 mm.

6. The integrated construction process of slag backfilling and roadbed structure according to claim 1 is characterized in that: The rolling process of step 4 includes: using a vibratory roller with a deadweight of ≥18t for layered compaction, the base layer is subjected to one static compaction followed by four vibration compactions, the transition layer is subjected to two static compactions followed by three vibration compactions, the reinforcement layer is subjected to three static compactions followed by two vibration compactions, and adjacent wheel tracks are maintained at an overlapping width of 300mm.

7. The integrated construction process of slag backfilling and roadbed structure according to claim 6 is characterized in that: The operating parameters of the vibratory roller are dynamically controlled according to the layers. The base layer adopts a strong vibration mode with an amplitude of 2.0-2.5mm and a vibration frequency of 28-32Hz, the transition layer adopts a medium vibration mode with an amplitude of 1.5-2.0mm and a vibration frequency of 25-28Hz, and the reinforcement layer adopts a weak vibration mode with an amplitude of 0.8-1.2mm and a vibration frequency of 20-25Hz. When rolling each layer, the roller speed is controlled at 2.0-2.5km / h for the base layer, 2.5-3.0km / h for the transition layer, and 3.0-3.5km / h for the reinforcement layer. The interval between rolling operations of adjacent layers is controlled at ≤30min for the base layer, ≤20min for the transition layer, and ≤10min for the reinforcement layer. The overlapping width of wheel tracks is adjusted according to the maximum particle size of the layer aggregate. The overlapping width of the base layer is set at 1.5 times the maximum particle size of the aggregate, the overlapping width of the transition layer is set at 1.2 times the maximum particle size of the aggregate, and the overlapping width of the reinforcement layer is set at 0.8 times the maximum particle size of the aggregate.

8. The integrated construction process of slag backfilling and roadbed structure according to claim 1 is characterized in that: In the double-layer cement-stabilized gravel layer of step 5, the lower layer is paved with gravel of 20-30mm in diameter and cement mixture with a thickness of 120mm, and the upper layer is paved with gravel of 5-10mm in diameter and cement mixture with a thickness of 80mm.

9. The integrated construction process of slag backfilling and roadbed structure according to claim 1, characterized in that: For the transverse drainage blind pipe system in step 6, transverse drainage blind pipes are buried every 20m along the longitudinal direction of the roadbed. The blind pipes are made of 100 mm diameter PVC perforated pipes, covered with 300g / m² permeable geotextile, and a 50mm thick 10-20mm crushed stone filter layer is filled between the pipe bottom and the backfill body.

10. The integrated construction process of slag backfilling and roadbed structure according to claim 9, characterized in that: The buried inclination angle of the transverse drainage blind pipe is controlled at 3-5°, the axial centerline of the pipe body forms an angle of 15-20° with the transverse slope direction of the roadbed, the perforation rate of the pipe is 8-10 holes / m² and the hole diameter is 5-8mm; The crushed stone filter layer adopts a double-layer graded structure. The lower layer is filled with 30mm thick coarse crushed stone with a particle size of 15-20mm, and the upper layer is filled with 20mm thick fine crushed stone with a particle size of 10-15mm. 200g / m² polyester needle-punched geotextile is laid between the layers as an anti-filtration isolation layer. The wrapping overlap width of the permeable geotextile is ≥150mm, and the overlap seam is processed by hot-melt welding process, the welding temperature is set to 280-300℃, and U-shaped stainless steel nails are set at intervals of 500mm on the top of the pipe to fix the geotextile; A three-way joint is set at the connection between the two ends of the drainage blind pipe and the longitudinal drainage ditch. A stainless steel filter with a pore size of 2mm is embedded in the inner wall of the joint, and a double-layer permeable geotextile is wrapped on the outer wall of the joint to form a 20mm thick anti-seepage buffer layer; After the drainage blind pipe is installed, an air tightness test is carried out.

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