BIM-based shallow goaf backfill tamping method

Abstract

This invention relates to the fields of mining engineering and geotechnical engineering, specifically a BIM-based method for backfilling and compacting shallow goaf areas. The method includes: acquiring geometric data of the goaf area using an acoustic scanner and a 3D laser scanner; constructing a BIM 3D model with geological attributes; and dividing risk zones according to cohesion. Drilling points are arranged according to the low-risk zones marked in the BIM model; a softening layer is formed using high-pressure water jetting; and drilling is advanced using micro-vibration. Prefabricated earthwork modules are used for layered backfilling, with grout of different viscosities injected in two stages. After each layer of backfill is compacted, the scanned data is obtained using an acoustic scanner and compared with the BIM model. Based on the test results, the construction parameters for the next layer are adjusted until the backfill reaches the design elevation. This invention achieves precise drilling point layout, low-disturbance construction of the strata, and dynamic controllable backfill quality, significantly improving the accuracy, efficiency, and safety of shallow goaf backfilling.

Description

Technical Field

[0001] This invention relates to the fields of mining engineering and geotechnical engineering technology, specifically a BIM-based method for backfilling and compacting shallow goaf areas. Background Technology

[0002] Shallow goaf refers to underground cavities formed after the extraction of mineral resources at a depth of ≤50m. According to the national standard "Code for Geotechnical Investigation of Coal Mine Goaf" (GB51044-2014), goafs with a mining depth of less than 50 meters, or a mining depth of 50-200 meters with a mining depth-to-thickness ratio of less than 30, are all classified as shallow goafs. These goafs are close to the surface, have poor stability, and are prone to ground subsidence or collapse, posing a serious threat to surface buildings, roads, other infrastructure, and the safety of people's lives and property.

[0003] Currently, the backfilling and remediation of shallow goaf areas mainly employs traditional methods such as borehole grouting and mechanical compaction. However, existing technologies have the following shortcomings: First, traditional methods mainly rely on manual experience and static survey data, making it difficult to accurately identify hidden cavities, fracture zones, and weak strata within the goaf. This results in unreasonable borehole location layout, uneven distribution of backfill material, and substandard compaction in some areas.

[0004] Secondly, traditional mechanical compaction equipment is difficult to adapt to the irregular spatial shape of the goaf, and the compaction path depends on manual judgment, which often requires repeated repairs, resulting in long construction cycles and serious waste of resources.

[0005] Third, during traditional drilling operations, the vibration of the drilling rig may disturb the roof and surrounding strata of the goaf. In particular, for shallow goaf areas with poor stability, the vibration may induce local collapses, increasing the risk to construction safety.

[0006] Fourth, traditional methods are mostly one-time constructions, lacking the ability to monitor and dynamically adjust the backfill quality in real time. They cannot optimize construction parameters in a timely manner according to the actual situation during the construction process, resulting in poor overall uniformity of the backfill and difficulty in controlling settlement in the later stages.

[0007] Therefore, how to provide a method for backfilling and compacting shallow goaf areas that can improve backfilling accuracy and efficiency, reduce construction risks, and achieve dynamic quality control is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the purpose of this invention is to provide a BIM-based method for backfilling and compacting shallow goaf areas, which can improve backfilling accuracy and efficiency, reduce construction risks, and achieve dynamic quality control.

[0009] The technical solution adopted by this invention to solve its technical problem is: A BIM-based method for backfilling and compacting shallow goaf areas includes the following steps: S1: 3D modeling of the goaf area. The geometric data of the goaf area is obtained by using an acoustic scanner and a 3D laser scanner. A BIM 3D model with geological attributes is constructed, and the goaf area is divided into high-risk, medium-risk and low-risk areas according to soil cohesion. S2: High-pressure water softening and micro-vibration combined drilling. Drilling points are arranged according to the low-risk areas marked in the BIM model. High-pressure water cutting is used to form a softening layer, and micro-vibration is used to advance the drilling. S3: Modular backfilling and gradient grouting, using prefabricated earthwork modules for layered backfilling, and injecting grout of different viscosities in two stages after each layer of earthwork modules is stacked. S4: Layered compaction and dynamic adjustment. After each layer of backfill and grouting, the compactor is operated to compact the layer according to the walking path planned in the BIM model. After compaction, the scanning data of the current backfill layer is obtained through an acoustic scanner. The scanning data is compared with the BIM 3D model to calculate the density or settlement rate of the current layer. If the density is lower than the preset value or the settlement rate exceeds the preset threshold, the excess area of ​​the current layer is compacted. At the same time, the construction parameters of the next layer are adjusted according to the test results of the current layer. The above process is repeated until the backfill reaches the design elevation.

[0010] As a preferred embodiment, a further technical solution of the present invention is: Preferably, S1 specifically includes, S101: Data acquisition, using acoustic scanners and 3D laser scanners to obtain the location, volume and burial depth of cavities in the goaf, and analyzing the soil cohesion, fissure development and groundwater distribution through geological drilling sampling. S102: Construct a BIM model, integrate data using the Revit or Navisworks platform, generate a BIM 3D model with geological attributes, and divide the goaf into high-risk, medium-risk, and low-risk zones according to cohesion, where the shear strength of the low-risk zone is ≥85kPa.

[0011] Preferably, S2 specifically includes: S201: Drilling point layout. Based on the low-risk area marked in the BIM model, in a ring-shaped area within 0.5m to 1m inside the boundary line of the goaf, drilling points are selected at equal intervals along the circumference with the geometric center of the horizontal projection of the goaf as the center. The distance between adjacent drilling points is 2m to 3m. S202: Soil softening and drilling. Using the center line of the drill pipe as the axis, a softening area with a diameter of 30cm is formed at the selected drilling point, and then the hole is drilled to the designed depth of the goaf. S203: Real-time correction. During the drilling process, the tilt sensor built into the pipe body monitors the deviation. When the deviation exceeds the preset angle, the drilling path is corrected according to the drilling path diagram in the BIM model or the target coordinates recalculated by the BIM model.

[0012] Preferably, S3 specifically includes: S301: Modular prefabricated earthwork, earthwork modules with a compaction degree of ≥90%, earthwork modules with 45° beveled corners, the number of earthwork modules used is determined according to the backfill volume calculated by the BIM model. S302: Layered backfilling, earthwork modules are sent into the bottom of the goaf layer by layer, with each layer having a backfill thickness of ≤0.5m. Adjacent earthwork modules and layers are stacked in a staggered manner with gaps of ≤5cm. S303: Venting treatment, drilling vent holes with a diameter of 5cm to 10cm in non-drilling areas to allow the gas generated during backfilling and grouting to be discharged; S304: Gradient grouting, which involves injecting grout of different viscosities in two stages after each layer of earthwork modules is stacked.

[0013] Preferably, the two-stage grouting specifically includes: the first stage of injecting low-viscosity cement grout to fill the gaps between earthwork modules; and the second stage of injecting high-viscosity composite grout to cover the surface and form a hardened shell.

[0014] Preferably, the water-cement ratio of the low-viscosity cement slurry is 0.5:1; the high-viscosity composite slurry contains fly ash and has a compressive strength ≥5MPa.

[0015] Preferably, S4 specifically includes: S401: Layered compaction. After each layer of earthwork is backfilled and grouted, the walking path of the compactor is planned according to the boundary of the goaf and the risk zone division in the BIM 3D model. Then, the compactor is operated according to the path to compact the earthwork. S402: Quality verification. After compaction, the backfill scan data is obtained by using an acoustic scanner. The scan data is compared with the BIM 3D model to calculate the density or settlement rate of the current layer. S403: Supplement compaction. If the density is lower than the preset value or the settlement rate exceeds the preset threshold, then supplement compaction should be carried out on the excess area of ​​the current layer. S404: Model update. After each layer of backfilling and compaction is completed, the BIM 3D model is updated by scanning with an acoustic scanner to adjust the construction parameters for the next layer. S405: Cyclic construction, repeating S401 to S404 until backfilling reaches the design elevation.

[0016] Preferably, the specific parameters for the layered compaction in S401 are as follows: each layer is compacted 3 times, the first time is static pressure with a static pressure of 50 kPa, and the second and third times are vibratory compaction with a vibration frequency of 25 Hz and an amplitude of 1.5 mm.

[0017] Preferably, the preset value of density in S403 is 90%, and the preset threshold of settlement rate is 2%.

[0018] Preferably, adjusting the construction parameters of the next layer in S404 specifically includes adjusting the grouting pressure and compaction times of the next layer based on the density test results of the current layer; increasing the grouting pressure or the number of compaction times of the next layer when the density of the current layer is less than 90%; and keeping the grouting pressure and number of compaction times of the next layer unchanged when the density of the current layer reaches or exceeds 90%.

[0019] The present invention, which adopts the above technical solution, has the following prominent features compared with the prior art: 1. Existing technologies rely on manual experience and static survey data to determine borehole locations, making it difficult to identify hidden cavities and weak strata within the goaf. This invention uses a fusion model of acoustic and 3D laser scanners to divide the goaf into high, medium, and low-risk zones based on soil cohesion. Based on the low-risk zones, borehole locations are arranged in a ring at equal intervals along the goaf boundary, achieving precise planning of borehole locations and effectively avoiding the risk of borehole collapse.

[0020] 2. Traditional layered backfilling involves directly dumping loose soil and then compacting it, which makes it difficult to control the density and results in uneven material distribution. This invention uses prefabricated high-density earthwork modules for layered, staggered stacking, combined with two-stage grouting, to ensure the overall uniformity and structural strength of the backfill.

[0021] 3. Existing technologies rely on manual judgment for compaction paths, lacking real-time quality feedback. This invention plans the compaction machine's path based on the goaf boundaries and risk zone distribution in the BIM model. Simultaneously, after each layer is compacted, scanning data is obtained via an acoustic scanner and compared with the BIM model. Based on the density test results, the grouting pressure and compaction frequency of the next layer are dynamically adjusted, forming a closed-loop control mechanism of detection-feedback-adjustment, ensuring that the backfill quality is controllable and traceable throughout the entire process. Attached Figure Description

[0022] Figure 1 This is a flowchart of the BIM-based shallow goaf backfilling and compaction method in this invention. Detailed Implementation

[0023] The present invention will be further illustrated below with reference to specific embodiments. The purpose of this illustration is solely to provide a better understanding of the invention. Therefore, the examples given do not limit the scope of protection of the present invention.

[0024] like Figure 1 As shown in the figure, this embodiment presents a BIM-based method for backfilling and compacting shallow goaf areas, including the following steps: S1: 3D modeling of the goaf. The geometric data of the goaf are obtained by using an acoustic scanner and a 3D laser scanner. A BIM 3D model with geological attributes is constructed, and the goaf is divided into high-risk, medium-risk and low-risk areas according to soil cohesion.

[0025] S1 specifically includes, S101: Data Acquisition. Acoustic scanners and 3D laser scanners are used to obtain the location, volume, and depth (≤50m) of cavities in the goaf. Geological drilling and sampling are used to analyze soil cohesion, fissure development, and groundwater distribution. The acoustic scanner can be a SonoScape X5 or S40 color Doppler ultrasonic scanner, or a LANNXuRason series or Kaixin KX5600 ultrasonic detector. The 3D laser scanner can be a mobile SLAM color 3D laser scanner (accuracy ≤3cm), a Shining 3D industrial-grade blue light scanner (accuracy 0.01mm), a Revopoint MetroXPro blue light scanner, or a Rushi 3D LiDAR scanner (error ±10mm). Those skilled in the art can select the appropriate equipment model based on the goaf size, accuracy requirements, and budget.

[0026] During scanning, the acoustic scanner lays out survey lines along the surface of the goaf according to a grid, with a survey line spacing of ≤2m, an excitation point spacing of ≤1m, and a receiver point spacing of ≤1m; the 3D laser scanner is erected on stable ground above the goaf, with at least 3 control points set, and the scanning resolution is set to 1 point / cm. 2 The scanning coverage angle is 360°×120%, and the scanning error is ≤3cm. After scanning, the point cloud data is registered with the acoustic velocity model using the ICP algorithm.

[0027] S102: Construct a BIM model, integrate data using a Revit or Navisworks platform, and generate a BIM 3D model with geological attributes. Divide the goaf into high-risk, medium-risk, and low-risk zones based on cohesion, with the low-risk zone having a shear strength ≥85kPa. Based on the BIM 3D model, calculate borehole locations, prioritizing low-risk zones and avoiding high- and medium-risk zones, and generate a borehole path map and material transport route.

[0028] S2: High-pressure water softening and micro-vibration combined drilling. Drilling points are arranged according to the low-risk areas marked in the BIM model. High-pressure water cutting is used to form a softening layer, and micro-vibration is used to advance the drilling.

[0029] S2 specifically includes: S201: Drilling point layout. Based on the low-risk area marked in the BIM model, in a ring-shaped area within 0.5m to 1m inside the boundary line of the goaf, drilling points are selected at equal intervals along the circumference with the geometric center of the horizontal projection of the goaf as the center. The distance between adjacent drilling points is 2m to 3m.

[0030] S202: Soil softening and drilling. At the selected drilling points, high-pressure water cutting is performed using a nozzle. The nozzle has several water outlets evenly distributed along the circumference and radial direction of the drill pipe. High-pressure water is sprayed simultaneously from all the outlets, collectively covering the entire circular cross-section, forming a cylindrical softening area with a diameter of 30cm around the center line of the drill pipe, thus uniformly softening the soil in front of the drill pipe. Simultaneously, a vibrator at the bottom of the pipe, with a frequency ≤30Hz and a vibration amplitude ≤2mm, pushes the pipe deeper, while a auger conveyor removes the broken soil.

[0031] The water pressure for high-pressure water cutting is set at 20MPa to 35MPa, the water consumption per hole is controlled at 50L to 80L / min, and the softening time lasts for 30s to 60s to ensure the formation of a cylindrical softened zone with a diameter of 30cm and a depth consistent with the designed borehole depth. The high-pressure water used is clean water or a drag-reducing slurry containing 1% to 3% bentonite.

[0032] S203: Real-time correction. During the drilling process, the tilt sensor built into the pipe body monitors the deviation. When the deviation exceeds the preset angle, the drilling path is corrected according to the drilling path diagram in the BIM model or the target coordinates recalculated by the BIM model.

[0033] S3: Modular backfilling and gradient grouting, using prefabricated earthwork modules for layered backfilling, and injecting grout of different viscosities in two stages after each layer of earthwork modules is stacked.

[0034] S3 specifically includes: S301: Modular prefabrication of earthwork, earthwork modules with a compaction degree of ≥90%, and earthwork modules with 45° beveled corners. The number of earthwork modules used is determined based on the backfill volume calculated from the BIM model.

[0035] Earthwork modules are made from locally sourced soil or transported clay, with a moisture content controlled between 15% and 18%. 3% to 5% cement or lime is added by weight as a curing agent. The modules are pressed using a static pressure molding machine at a pressure ≥10MPa. The standard module dimensions are 600mm × 300mm × 200mm, with a 45° × 5mm chamfer on each side. The module curing time is ≥72 hours, and the unconfined compressive strength is tested to ≥1.5MPa before leaving the factory.

[0036] S302: Layered backfilling. Earthwork modules are successively introduced at the bottom of the goaf, with each layer ≤0.5m thick. Adjacent earthwork modules and layers are staggered, with gaps ≤5cm. During staggered stacking, the offset between the centerlines of upper and lower modules is not less than 1 / 3 of the module length. Gaps between adjacent modules are filled with fine sand or cement mortar with a particle size ≤5mm. After each layer is stacked, the flatness is checked with a 2m straightedge, with an error ≤1cm.

[0037] S303: Venting treatment, drilling vent holes with a diameter of 5cm to 10cm in non-drilling areas to allow the gas generated during backfilling and grouting to be discharged.

[0038] S304: Gradient grouting. After each layer of earthwork modules is stacked, grouts of different viscosities are injected in two stages. Specifically, the two-stage grouting includes: the first stage injecting low-viscosity cement grout to fill the gaps between the earthwork modules; the second stage injecting high-viscosity composite grout to cover the surface and form a hardened shell. In this embodiment, the water-cement ratio of the low-viscosity cement grout is 0.5:1, used to fill the gaps between the earthwork modules; the high-viscosity composite grout contains fly ash and has a compressive strength ≥5MPa, used to cover the surface and form a hardened shell.

[0039] S4: Layered compaction and dynamic adjustment. After each layer of backfill and grouting, the compactor is operated to compact the layer according to the walking path planned in the BIM model. After compaction, the scanning data of the current backfill layer is obtained through an acoustic scanner. The scanning data is compared with the BIM 3D model to calculate the density or settlement rate of the current layer. If the density is lower than the preset value or the settlement rate exceeds the preset threshold, the excess area of ​​the current layer is compacted. At the same time, the construction parameters of the next layer are adjusted according to the test results of the current layer. The above process is repeated until the backfill reaches the design elevation.

[0040] S4 specifically includes: S401: Layered compaction. After each layer of backfilled soil and grouting, the compactor's path is planned according to the boundary of the goaf and the risk zone division in the BIM 3D model. Then, the compactor is operated according to the path for compaction. In this embodiment, the specific parameters for layered compaction are: each layer is compacted 3 times. The first time is static pressure with a static pressure of 50 kPa. The second and third times are vibratory compaction with a vibration frequency of 25 Hz and an amplitude of 1.5 mm.

[0041] The compactor is a vibratory plate compactor. The BIM model is based on the boundary of the goaf and the risk zone division. The Dijkstra algorithm is used to automatically generate a walking path that covers the entire backfill area and has a path repetition rate of ≤10%. The path prioritizes passing through low-risk areas.

[0042] S402: Quality verification. After the compaction is completed, scan data of the backfill is obtained by an acoustic scanner, the scan data is compared with a BIM three-dimensional model, and the compactness or settlement rate of the current layer is calculated.

[0043] Quality verification: After the compaction is completed, the P-wave velocity and S-wave velocity of the current backfill layer are collected by an acoustic scanner, the wave velocities are converted into density by using an empirical formula obtained through on-site calibration, then the compactness is calculated according to the ratio of the measured density to the maximum dry density obtained by a laboratory compaction test, expressed as a percentage. A voxel model is constructed from the measured compactness data, and a gridded comparison is performed with the ideal compactness distribution in the BIM three-dimensional model, with a grid size of 0.2m×0.2m×0.2m. If the proportion of the number of grids with compactness reaching or exceeding 90% in the current layer to the total number of grids of the layer is not less than 90%, the current layer is determined to be qualified; otherwise, supplementary compaction is performed on the non-compliant areas.

[0044] S403: Supplementary compaction. If the compactness is lower than 90% or the settlement rate is greater than 2%, supplementary compaction is performed on the out-of-standard areas of the current layer until the compactness is ≥90% and the settlement rate is ≤2%.

[0045] S404: Model updating and parameter adjustment. After each layer of backfill compaction is completed, the BIM three-dimensional model is updated through scanning by the acoustic scanner, which is used to adjust the construction parameters of the next layer. The specific adjustment strategy is: adjusting the grouting pressure and compaction times of the next layer according to the compactness detection result of the current layer; when the compactness of the current layer is lower than 90%, increasing the grouting pressure of the next layer or increasing the compaction times of the next layer; when the compactness of the current layer reaches or exceeds 90%, keeping the grouting pressure and compaction times of the next layer unchanged.

[0046] S405: Cyclic construction. Repeat steps S401 to S404 until backfilling is completed to the design elevation.

[0047] In addition, a settlement sensor (accuracy: ±1mm) is buried in the backfill, which is used to monitor the daily settlement of the backfill in real time, and issue an early warning when the daily settlement is ≥3mm. Example

[0048] This example takes a stable goaf with a depth of no more than 30 meters and a relatively regular shape in a certain mining area as the object, and the goal is to complete backfilling quickly and economically to provide a stable foundation for subsequent land development.

[0049] S1: Three-dimensional modeling of the goaf; a combination of an acoustic scanner (accuracy: ±0.1m), a three-dimensional laser scanner and a small amount of drilling sampling is used to efficiently obtain the spatial geometric dimensions and boundary information of the goaf, and drilling sampling focuses on verifying the thickness and integrity of the roof rock stratum. The cohesion of soil is analyzed through geological drilling sampling, and areas with shear strength ≥85kPa are marked as low-risk areas.

[0050] A 3D model of the goaf is built in the BIM platform (Revit) and integrated with engineering geological zoning information. The model attributes include the goaf volume, roof lithology, and initial stability assessment set based on the exploration data.

[0051] S2: Drilling point layout and drilling; The BIM model automatically plans 8 optimal drilling points based on the goaf morphology. These points are all located in the low-risk area determined by the model, and the optimal mechanical travel path is generated to reduce the equipment movement distance.

[0052] The model is used to accurately calculate the amount of backfill material and guide the pre-construction of approximately 5,000 standard earthwork modules. Each module measures 1m × 0.5m × 0.3m, with a compaction degree ≥90% and 45° chamfered corners. The model also allows for visualized construction simulation of the backfilling process, enabling early detection of potential problems.

[0053] S3: Modular backfilling and gradient grouting; High-pressure water softening and micro-vibration were used in conjunction with drilling. Water pressure ≥20MPa was used to flush the soil and form a softened layer with a diameter of 30cm. A vibrator was used to advance the drill pipe at a frequency ≤30Hz and a vibration amplitude ≤2mm, while a auger conveyor was activated simultaneously to remove loose soil. During the drilling process, tilt sensors were used to monitor the deviation and correct it in real time.

[0054] Precast earthwork modules are transported to the goaf through boreholes according to the sequence and layer thickness (0.5 meters per layer) set in the BIM model. Modular backfilling and gradient grouting processes are used. After each layer of earthwork modules is stacked, low-viscosity cement grout with a water-cement ratio of 0.5:1 is first injected to fill the gaps, followed by high-viscosity composite grout with fly ash and a compressive strength ≥5MPa to form a hardened shell. At the same time, vent holes with a diameter of 5-10cm are drilled in non-drilling areas to release gas.

[0055] S4: Layered compaction and dynamic adjustment; after each layer of backfill is completed, compaction is carried out using a compactor according to the walking path planned in the BIM model. Each layer is compacted 3 times: the first time with static pressure of 50 kPa, and the second and third times with vibratory compaction (frequency 25 Hz, amplitude 1.5 mm). After compaction, the scan data is obtained by an acoustic scanner and compared with the BIM model. If the density is lower than 90% or the settlement rate is greater than 2%, additional compaction is required. The grouting pressure or number of compactions for the next layer is adjusted based on the test results of the current layer. Settlement sensors (accuracy ±1 mm) are embedded in the backfill to monitor the daily settlement, with a warning value of 3 mm.

[0056] After the backfilling was completed, by comparing the later scanning data with the BIM model, it was confirmed that the average surface settlement was less than 2 cm and the overall compaction of the backfill reached 94%, which fully met the design requirements. Example

[0057] This embodiment addresses a multi-layered, irregularly intersecting goaf formed by historical mining, with a maximum depth of approximately 60 meters, posing a risk of localized collapse. The goal of the remediation is to ensure that the deep areas are fully filled and to eliminate safety hazards.

[0058] S1: 3D modeling of the goaf; using an acoustic scanner (accuracy ±0.1m) to accurately detect the spatial distribution of multi-layered goafs, the thickness of rock pillars between layers, and existing fracture development zones. Soil cohesion is analyzed through geological drilling sampling, and risk zones are divided according to shear strength: ≥85kPa is a low-risk zone, 60-85kPa is a medium-risk zone, and <60kPa is a high-risk zone.

[0059] By integrating multi-source detection data into the BIM model, a three-dimensional geological model is constructed that can clearly reflect the relationship between goaf areas and weak areas in each layer. The model highlights stress concentration areas and potential breakthrough risk points.

[0060] S2: Drilling point layout and drilling; Based on the analysis of the BIM model, the goaf is divided into key reinforcement areas (such as coal pillar stress concentration areas) and general backfill areas.

[0061] For key reinforcement areas, the design adopts high-pressure jet grouting technology, using BIM model to accurately locate the drilling position and depth, ensuring that the grout can be effectively injected into the key weak points.

[0062] For general backfill areas, the economical backfill scheme of Example 1 is adopted, but the grouting pressure and time are adjusted according to the layer depth.

[0063] S3: Modular backfilling and gradient grouting; The drilling process employs a combination of high-pressure water softening and micro-vibration (water pressure ≥ 20 MPa, vibration frequency ≤ 30 Hz, amplitude ≤ 2 mm) to minimize disturbance to the unstable roof.

[0064] In general backfill areas, precast earthwork modules (compactness ≥90%, 45° chamfered edges) are transported to the goaf area via boreholes according to the sequence and layer thickness (0.5 meters per layer) set in the BIM model. They are stacked with staggered joints, with gaps ≤5cm. After each layer is stacked, grouting is performed in two stages: first, low-viscosity cement grout with a water-cement ratio of 0.5:1 is injected to fill the gaps; then, high-viscosity composite grout with fly ash and a compressive strength ≥5MPa is injected to form a hardened shell. Simultaneously, vent holes with a diameter of 5-10cm are drilled in non-drilling areas to release gas.

[0065] For key reinforcement areas (such as areas of concentrated stress in coal pillars), based on the above-mentioned modular backfilling and gradient grouting process, the location of the additional boreholes is accurately located using the BIM model, and the grouting pressure is appropriately increased to ensure that the grout can be effectively injected into the key weak parts.

[0066] S4: Layered compaction and dynamic adjustment; During construction, data is collected in real time using borehole cameras and grouting pressure sensors, and the BIM model is dynamically updated. For example, when the grouting volume in a certain area far exceeds the design value, the model will immediately adjust the grouting parameters for subsequent areas, achieving information-based construction and precise control. After each layer is compacted, the model is updated by scanning with an acoustic scanner, and the grouting pressure and compaction times for the next layer are adjusted based on the density test results.

[0067] Ultimately, through comparison and verification of model data, it was found that the deep goaf was fully filled, effectively controlling the movement of rock strata, and the surface subsidence rate was stably controlled within 1.5%. Example

[0068] This example focuses on a mining subsidence remediation project located near a town, which has extremely high requirements for environmental protection and ecological restoration. The project aims to achieve harmony with the surrounding natural environment while safely backfilling the area.

[0069] S1: 3D modeling of mining subsidence areas; In the BIM model, not only geological data (including high, medium and low risk zones divided according to cohesion) are input, but also ecological factors such as surface vegetation distribution, soil and water loss sensitivity, and landscape visual impact range are superimposed.

[0070] After comprehensive model analysis, the layout of access roads for backfilling construction and the location of temporary earthwork stockpiles were optimized, and a topsoil stripping and preservation scheme was proposed to minimize damage to the surface ecology.

[0071] S2: Drilling point layout and drilling; Drilling operations are strictly controlled within the low-risk area marked in the BIM model. High-pressure water softening and micro-vibration are used in combination for drilling (water pressure ≥20MPa, vibration frequency ≤30Hz, amplitude ≤2mm) to avoid disturbing surrounding residents and wildlife.

[0072] For backfill materials, priority is given to using construction waste soil and stone compacted earthwork modules (density ≥90%) generated by the project itself, and innovatively, ecological grouting materials with high fly ash content (compressive strength ≥5MPa) are used, which not only digests industrial solid waste, but also reduces material costs and environmental impact. Grouting is carried out in two stages: first, low-viscosity cement grout (water-cement ratio 0.5:1) is injected to fill the gaps, and then high-viscosity composite grout is injected to form a hardened shell.

[0073] S3: Modular backfilling and gradient grouting; When backfilling to near the ground surface, BIM model is used for micro-topography design to create undulating terrain that facilitates natural rainwater drainage and vegetation growth.

[0074] The previously preserved high-quality topsoil was backfilled, and suitable tree, shrub, and grass seeds were mixed and sprayed to quickly restore vegetation. During the backfilling and compaction process, real-time scanning was performed using an acoustic scanner, and additional compaction was required when the density was below 90%. Settlement sensors (accuracy ±1mm) were embedded in the backfill for real-time monitoring, and an alert was issued when the daily settlement was ≥3mm.

[0075] This invention not only eliminates the hidden dangers of mining subsidence areas, but also transforms the original mining area into an urban green park that blends seamlessly with the surrounding landscape, thereby maximizing the added value of land resources and ecological benefits.

[0076] In summary, compared with existing technologies, this invention achieves risk zoning and precise borehole positioning in goaf areas through BIM technology, reduces ground disturbance by using high-pressure water softening and micro-vibration combined with drilling, ensures uniform and dense backfill by utilizing prefabricated earthwork modules and two-stage gradient grouting, and forms a closed-loop quality control by combining compaction path planning and sonic scanning feedback. This effectively solves the problems of insufficient accuracy, low efficiency, and poor safety of traditional methods, and significantly improves the construction quality and safety of backfilling in shallow goaf areas.

[0077] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. All equivalent changes made based on the description and drawings of the present invention are included within the scope of the present invention.

Claims

1. A BIM-based method for backfilling and compacting shallow goaf areas, characterized in that: Includes the following steps, S1: 3D modeling of the goaf area. The geometric data of the goaf area is obtained by using an acoustic scanner and a 3D laser scanner. A BIM 3D model with geological attributes is constructed, and the goaf area is divided into high-risk, medium-risk and low-risk areas according to soil cohesion. S2: High-pressure water softening and micro-vibration combined drilling. Drilling points are arranged according to the low-risk areas marked in the BIM model. High-pressure water cutting is used to form a softening layer, and micro-vibration is used to advance the drilling. S3: Modular backfilling and gradient grouting, using prefabricated earthwork modules for layered backfilling, and injecting grout of different viscosities in two stages after each layer of earthwork modules is stacked. S4: Layered compaction and dynamic adjustment. After each layer of backfill and grouting, the compactor is operated to compact the layer according to the walking path planned in the BIM model. After compaction, the scanning data of the current backfill layer is obtained through an acoustic scanner. The scanning data is compared with the BIM 3D model to calculate the density or settlement rate of the current layer. If the density is lower than the preset value or the settlement rate exceeds the preset threshold, the excess area of ​​the current layer is compacted. At the same time, the construction parameters of the next layer are adjusted according to the test results of the current layer. Repeat the above process until backfilling reaches the design elevation.

2. The BIM-based method for backfilling and compacting shallow goaf areas according to claim 1, characterized in that: S1 specifically includes, S101: Data acquisition, using acoustic scanners and 3D laser scanners to obtain the location, volume and burial depth of cavities in the goaf, and analyzing the soil cohesion, fissure development and groundwater distribution through geological drilling sampling. S102: Construct a BIM model, integrate data using the Revit or Navisworks platform, generate a BIM 3D model with geological attributes, and divide the goaf into high-risk, medium-risk, and low-risk zones according to cohesion, where the shear strength of the low-risk zone is ≥85kPa.

3. The BIM-based method for backfilling and compacting shallow goaf areas according to claim 1, characterized in that: S2 specifically includes: S201: Drilling point layout. Based on the low-risk area marked in the BIM model, in a ring-shaped area within 0.5m to 1m inside the boundary line of the goaf, drilling points are selected at equal intervals along the circumference with the geometric center of the horizontal projection of the goaf as the center. The distance between adjacent drilling points is 2m to 3m. S202: Soil softening and drilling. Using the center line of the drill pipe as the axis, a softening area with a diameter of 30cm is formed at the selected drilling point, and then the hole is drilled to the designed depth of the goaf. S203: Real-time correction. During the drilling process, the tilt sensor built into the pipe body monitors the deviation. When the deviation exceeds the preset angle, the drilling path is corrected according to the drilling path diagram in the BIM model or the target coordinates recalculated by the BIM model.

4. The BIM-based method for backfilling and compacting shallow goaf areas according to claim 1, characterized in that: S3 specifically includes: S301: Modular prefabricated earthwork, earthwork modules with a compaction degree of ≥90%, earthwork modules with 45° beveled corners, the number of earthwork modules used is determined according to the backfill volume calculated by the BIM model. S302: Layered backfilling, earthwork modules are sent into the bottom of the goaf layer by layer, with each layer having a backfill thickness of ≤0.5m. Adjacent earthwork modules and layers are stacked in a staggered manner with gaps of ≤5cm. S303: Venting treatment, drilling vent holes with a diameter of 5cm to 10cm in non-drilling areas to allow the gas generated during backfilling and grouting to be discharged; S304: Gradient grouting, which involves injecting grout of different viscosities in two stages after each layer of earthwork modules is stacked.

5. The BIM-based backfilling and compaction method for shallow goaf areas according to claim 4, characterized in that: The two-stage grouting process includes: the first stage involves injecting low-viscosity cement grout to fill the gaps between earthwork modules; the second stage involves injecting high-viscosity composite grout to cover the surface and form a hardened shell.

6. The BIM-based backfilling and compaction method for shallow goaf areas according to claim 5, characterized in that: The water-cement ratio of low-viscosity cement slurry is 0.5:1; the high-viscosity composite slurry contains fly ash and has a compressive strength ≥5MPa.

7. The BIM-based method for backfilling and compacting shallow goaf areas according to claim 1, characterized in that: S4 specifically includes: S401: Layered compaction. After each layer of earthwork is backfilled and grouted, the walking path of the compactor is planned according to the boundary of the goaf and the risk zone division in the BIM 3D model. Then, the compactor is operated according to the path to compact the earthwork. S402: Quality verification. After compaction, the backfill scan data is obtained by using an acoustic scanner. The scan data is compared with the BIM 3D model to calculate the density or settlement rate of the current layer. S403: Supplement compaction. If the density is lower than the preset value or the settlement rate exceeds the preset threshold, then supplement compaction should be carried out on the excess area of ​​the current layer. S404: Model update. After each layer of backfilling and compaction is completed, the BIM 3D model is updated by scanning with an acoustic scanner to adjust the construction parameters for the next layer. S405: Cyclic construction, repeating S401 to S404 until backfilling reaches the design elevation.

8. The BIM-based backfilling and compaction method for shallow goaf areas according to claim 7, characterized in that: The specific parameters for the layered compaction described in S401 are as follows: each layer is compacted 3 times. The first time is static compaction with a static pressure of 50 kPa. The second and third times are vibratory compaction with a vibration frequency of 25 Hz and an amplitude of 1.5 mm.

9. The BIM-based method for backfilling and compacting shallow goaf areas according to claim 7, characterized in that: The preset value for density in S403 is 90%, and the preset threshold for settlement rate is 2%.

10. The BIM-based method for backfilling and compacting shallow goaf areas according to claim 7, characterized in that: S404 adjusts the construction parameters of the next layer, specifically including adjusting the grouting pressure and compaction times of the next layer based on the density test results of the current layer; when the density of the current layer is less than 90%, increasing the grouting pressure or the number of compaction times of the next layer; when the density of the current layer reaches or exceeds 90%, keeping the grouting pressure and number of compaction times of the next layer unchanged.

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