A method for treating the foundation of a strip coal yard with a portal stacker-reclaimer in soft soil areas.

Abstract

This invention relates to the field of civil engineering technology for power plants, and particularly to a method for treating the foundation of a strip coal yard with a portal reclaimer in soft soil areas. The method includes the following steps: vacuum combined with surcharge preloading of the surface silt and soft soil of the coal yard; construction of external retaining structure piles and central reclaimer piles; installation of steel cage pressure relief holes at the pile foundations; measurement of the parameters of the treated foundation soil; design and implementation of coal stockpiling according to the parameters in stages, while simultaneously deploying a monitoring system to monitor soil and structural deformation in real time; dynamic adjustment of the coal stockpiling progress based on the monitoring data; and completion of the foundation treatment after the coal has reached the designed capacity and the deformation has stabilized. By combining vacuum preloading, pile driving of site structures, installation of pressure relief holes, staged coal stockpiling, real-time monitoring, adjustment of the coal stockpiling plan, and final completion of the foundation treatment, this method is applicable to the foundation treatment of coal yards in soft soil foundations.

Description

Technical Field

[0001] This invention relates to the field of civil engineering technology for power plants, and in particular to a method for treating the foundation of a strip coalfield for a portal stacker-reclaimer in soft soil areas. Background Technology

[0002] Gantry stacker-reclaimers for strip coal yards offer advantages such as high coal stacking height, relatively small footprint, and convenient stacking and reclaiming. However, when applied in coastal soft soil areas, where the surface silt and soft soil have a bearing capacity of approximately 50 kPa, and the coal stacking height is around 22 meters, a foundation bearing capacity greater than 220 kPa is required. Since the natural foundation bearing capacity is insufficient, foundation treatment is necessary. Therefore, this issue urgently needs to be addressed. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for treating the foundation of a strip coalfield of a portal stacker-reclaimer in soft soil areas. The method is scientific and reasonable, highly flexible and easy to implement.

[0004] To achieve the aforementioned objective, the technical solution of the present invention is implemented as follows: a method for treating the foundation of a strip coalfield with a portal reclaimer in soft soil areas, characterized by comprising the following steps: 1) Vacuum combined surcharge preloading treatment is carried out on the surface silt and soft soil of the coal yard to initially improve the strength and density of the foundation soil; 2) After vacuum preloading is completed, the construction of the outer structure piles is carried out at the periphery of the coal yard, and the construction of the central reclaimer piles is carried out at the center of the coal yard. 3) After the construction of the outer structural piles and the central reclaimer piles is completed, steel cage pressure relief holes are set at the foundations of the outer structural piles and the central reclaimer piles to release the lateral pressure generated by the soil during coal stockpiling. 4) Conduct on-site measurements of soil layer parameters on the preloaded site soil to obtain accurate foundation design parameters; 5) Set up soil displacement monitoring points, external structural piles and central reclaimer pile foundation deformation monitoring points on the coal yard, and estimate the coal pile height on the coal yard based on the detected soil parameters, and design the coal pile structure in stages based on the estimated coal pile height. 6) Stack coal according to the structure of the coal pile designed in stages, and monitor the deformation of the foundation soil, the outer structural piles and the central reclaimer pile foundation in real time during the coal stacking process; 7) Adjust the coal stacking progress based on the measured deformation data at each monitoring point during the coal stacking process and the design allowable deformation data; ensure construction safety; 8) After the coal pile reaches its maximum design capacity, continuously monitor the deformation data of the outer structural piles and the central reclaimer piles of the coal yard; 9) Once the deformation is continuously monitored and meets the allowable value, the site foundation treatment is completed, and coal can be piled up freely.

[0005] Preferably, in step 1), the vacuum pre-compression process includes: 11) Level and clear the site, and lay a sand cushion layer; 12) Install plastic drainage boards on the site, and install clay mixing pile sealing walls around the perimeter of the vacuum preloading treatment area to block the permeable layer, and the clay mixing pile sealing walls should penetrate the silt layer of the site by no less than 1 meter. 13) Excavate filter pipe trenches and lay a vacuum network. The branch pipes of the network are connected to the ends of the plastic drainage boards, the main pipes are connected to the vacuum equipment, and vacuum monitoring equipment is installed. 14) Lay a layer of geotextile on the sand cushion layer, and then lay two layers of vacuum membrane on the geotextile. 15) Excavate a sealing trench around the vacuum sealing membrane and compact the silt in the trench to form a seal; 16) Perform pre-vacuuming, check the sealing system to ensure that the design vacuum pressure can be reached, and then perform stable vacuuming to make the vacuum degree at the end of the pipe reach the design standard value and maintain it for no less than 20 days; 17) Apply surcharge in stages on the site after pre-vacuuming, in the following order: first stage surcharge thickness 2.0 meters; second stage surcharge thickness 2.0 meters; third stage local surcharge thickness 2.5 meters; surcharge material is slag or other fill.

[0006] Preferably, the outer structural piles and the central material reclaimer piles are selected as cast-in-place piles or precast pipe piles based on the detection information of the geological bearing layer.

[0007] Preferably, in step 3), the construction process of the pressure relief hole for the steel reinforcement cage includes: 31) Drill holes inside the pile foundation to remove soil and form pile holes; 32) Insert the reinforcing cage wrapped with geotextile into the pile hole; 33) Cover the top of the steel cage with steel mesh and geotextile, then backfill with soil and compact it.

[0008] Preferably, in step 4), the actual measurement of soil parameters includes: testing the bearing capacity of the surface foundation using a shallow plate load test; testing the bearing capacity of the soil at different depths using a static cone penetration test; and obtaining the physical and mechanical parameters of the soil using indoor geotechnical tests.

[0009] Preferably, in step 5), the monitoring information obtained by the monitoring point includes: horizontal displacement of deep soil, surface settlement, settlement and deformation of the feeder track foundation and the foundation of the outer retaining structure, and excess pore water pressure of the coalfield foundation.

[0010] Preferably, when designing the graded coal pile structure, the finite element method is used to simulate and calculate the strength and deformation of the foundation soil under the load of each grade of coal pile, so as to estimate and determine the thickness and range of each grade of coal pile.

[0011] Preferably, in step 8), the monitoring alarm indicators for the deformation data include: daily surface settlement of the backfill area exceeding 15 mm; and maximum daily lateral deformation of the soil exceeding 5 mm.

[0012] Preferably, in steps 8) and 9), the frequency of continuous monitoring is: once a month in the first year after production starts, and once a quarter in the second and third years; the allowable value standard for termination of monitoring is: the settlement increment of the foundation soil in the coal yard area for two consecutive six-month periods does not exceed 2mm.

[0013] The beneficial effects of this invention are reflected in: This invention systematically solves the foundation treatment challenges of high-load strip coal yards in soft soil areas through a comprehensive technical approach of "pre-loading reinforcement, pile foundation support, pressure relief protection, and full-process monitoring and adjustment." Vacuum combined with surcharge preloading rapidly increases the foundation bearing capacity; pile foundations provide support for the main structure; the pressure relief holes in the steel cages effectively release soil pressure, protecting the pile foundation safety; and a graded coal stacking and real-time monitoring system based on measured parameters enables information-based construction and dynamic risk control, ensuring a safe, controllable, and efficient foundation treatment process. This method is particularly suitable for the construction of large strip coal yards in soft soil areas sensitive to settlement and lateral deformation. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the monitoring point layout during the vacuum combined loading preloading stage of the present invention; Figure 2 This is a schematic diagram of the construction progress of the vacuum combined surcharge preloading of the present invention; Figure 3 This is a schematic diagram of the planar arrangement of the pressure relief holes in the steel cage of the present invention; Figure 4 This is a diagram showing the layout of monitoring points during the coal preloading stage of this invention. Figure 5 This is a schematic diagram of the graded coal stacking scheme of the present invention. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Example like Figure 1-5 As shown, this invention provides a method for treating the foundation of a strip coal yard for a gantry stacker-reclaimer in soft soil areas; this method is applied in a power plant strip coal yard project in a coastal soft soil area, and specifically includes the following steps: Step 1: Vacuum-combined surcharge preloading treatment First, vacuum combined loading preloading was carried out on the surface silt in the coal yard area. The specific steps are as follows: 1. Level the site and remove obstacles.

[0017] 2. Lay a 500mm thick sand cushion layer.

[0018] 3. Install plastic drainage boards in an equilateral triangle arrangement with a spacing of 1.1m and a depth of 20m.

[0019] 4. Construct a clay mixing pile sealing wall along the treatment boundary, with the bottom of the wall extending at least 1m into the silt layer to form a closed vacuum cavity.

[0020] 5. Excavate filter pipe trenches, lay vacuum pipe networks (branch pipes and main pipes), connect branch pipes to drainage boards, and connect main pipes to vacuum equipment. Install monitoring equipment such as vacuum gauges.

[0021] 6. Lay a layer of 300g / m² non-woven geotextile (overlap width ≥ 500mm).

[0022] 7. Lay two layers of polyvinyl chloride (PVC) vacuum sealing film. The film material is required to be anti-aging, tough, and puncture resistant. Its performance indicators are as described in the instruction manual.

[0023] 8. Dig a sealing trench around the sealing membrane and compact the silt in the trench to seal it.

[0024] 9. Begin pre-vacuuming and check the sealing performance of the entire system (sealing wall, membrane, membrane outlet) to ensure that the design vacuum pressure of 86.7 kPa can be achieved.

[0025] 10. Enter the stable vacuuming stage and maintain the vacuum level at the end of the tube at 86.7 kPa for about 25 days.

[0026] 11. After vacuum stabilization, apply the load in stages: Level 1: 2.0-meter-thick sludge (from bottom to top: 0.3m medium-coarse sand + 0.5m clay + 1.2m slag).

[0027] Second stage: Continue to load 2.0-meter-thick slag.

[0028] Level 3: Locally load 2.5-meter-thick slag in key areas.

[0029] This process simulates future coal pile loads and accelerates the consolidation of soft soil through the combined effect of vacuum pressure (approximately 86.7 kPa) and additional load pressure (approximately 70 kPa), significantly improving the bearing capacity of the foundation.

[0030] Step 2: Pile Foundation Construction After preloading, the stockpiled soil was removed and the site was leveled. Based on the bearing stratum selected in the detailed survey report, cast-in-place piles were used to construct the outer structural piles of the coal yard and the central reclaimer piles. In addition to considering conventional vertical loads, the pile foundation design also specifically verified the additional lateral forces on the pile body caused by the horizontal deformation of the foundation soil due to future coal stockpiling, ensuring the safety of the pile foundation.

[0031] Step 3: Install pressure relief holes for the steel cage. To mitigate the pressure on the pile foundation caused by lateral soil expansion during coal stockpiling, a reinforced cage pressure relief hole is installed on the inner side of the cast-in-place pile (the side closest to the coal yard). The procedure is as follows: a hole is drilled at a predetermined location using a drilling rig to create a cavity; a reinforced cage is fabricated and wrapped with geotextile; the cage is inserted into the hole, with the top of the cage 0.5m below the natural ground level; finally, a 600mm x 600mm steel mesh and geotextile are placed on top of the cage, and the soil is backfilled and compacted. This structure provides a pressure relief channel when the soil deforms, protecting the pile body.

[0032] Step 4: Actual measurement of foundation parameters Field and laboratory tests were conducted on the preloaded foundation soil, including: shallow plate load tests to obtain surface bearing capacity; static cone penetration tests to obtain specific penetration resistance at different depths; and drilling and sampling for laboratory geotechnical tests to obtain physical and mechanical properties. The measured data served as the basis for subsequent design.

[0033] Step 5: Deploy the monitoring system Monitoring points are systematically deployed both inside and outside the coal yard: benchmark points are set up at locations far from the coal yard (>60 meters). Monitoring content includes: Deep horizontal displacement: monitored by burying inclinometer tubes and using an inclinometer.

[0034] Surface subsidence: Set up subsidence observation points and monitor them using a level.

[0035] Structural deformation: Observation points are set on the foundation of the reclaimer track and the columns of the outer protective structure to monitor settlement and tilt.

[0036] Excess pore water pressure: Monitored by burying a steel wire pore water pressure gauge.

[0037] Protective measures such as building protective blocks and adding cover plates are taken for all monitoring elements.

[0038] Step 6: Design and Implementation of Graded Coal Stockpiling Based on measured foundation parameters, a staged coal stockpiling scheme was designed using finite element software simulation analysis. For example... Figure 5As shown, the scheme follows the principle of "from the center outward, layered symmetry, and increasing height step by step", and is divided into five levels (P1 to P5) for coal piling, with the height, range and pressure stabilization time of each level of coal piling estimated.

[0039] Step 7: Real-time monitoring and dynamic adjustment of the coal stacking process Coal is piled up according to a tiered plan, and real-time monitoring is initiated simultaneously. Alarm indicators are set: daily surface settlement >15mm or daily lateral soil deformation >5mm. Once the monitoring data approaches or exceeds the alarm value, loading is immediately suspended, and if necessary, part of the coal pile is unloaded. Construction can resume only after the deformation stabilizes, ensuring that the entire construction process is under control.

[0040] Steps 8 and 9: Long-term monitoring and post-work assessment After the coal yard reaches its designed capacity and is put into operation, it enters the long-term post-construction monitoring phase: monthly observations in the first year, and quarterly observations in the second and third years. When the annual settlement increment (every six months is an assessment period) does not exceed 2mm for two consecutive times, the foundation deformation is considered to have basically stabilized, the system monitoring can be terminated, and the site can be used freely and safely.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for treating the foundation of a strip coal yard with a portal stacker-reclaimer in soft soil areas, characterized in that, Includes the following steps: 1) Vacuum combined surcharge preloading treatment was carried out on the surface silt and soft soil of the coal yard; 2) After vacuum preloading is completed, unload the load, level the site, carry out the construction of the outer structure piles at the periphery of the coal yard, and carry out the construction of the central reclaimer piles at the center of the coal yard. 3) After the construction of the outer structure piles and the central material reclaimer piles is completed, steel reinforcement cage pressure relief holes shall be set in the area around the piles of the outer structure piles and the central material reclaimer piles. In step 3), the construction process of the pressure relief hole for the steel reinforcement cage includes: 31) Drill holes inside the pile foundation to remove soil and form pile holes; 32) Insert the reinforcing cage wrapped with geotextile into the pile hole; 33) Cover the top of the steel cage with a steel mesh and geotextile, then backfill with soil and compact it; 4) Conduct on-site measurements of soil layer parameters on the foundation soil of the coalfield after the treatment in step 1); 5) After the construction of the coal yard enclosure structure is completed, set up soil displacement monitoring points, outer structure piles and central material reclaimer pile foundation deformation monitoring points on the coal yard, and estimate the coal pile height on the coal yard based on the detected soil parameters, and design the coal pile structure in stages based on the estimated coal pile height. 6) Stack coal according to the structure of the coal pile designed in stages, and monitor the deformation of the foundation soil, the outer structural piles and the central reclaimer pile foundation in real time during the coal stacking process; 7) Adjust the coal stacking progress based on the measured deformation data at each monitoring point during the coal stacking process and the design allowable deformation data; 8) After the coal pile reaches its maximum design capacity, continuously monitor the deformation data of the outer structural piles and the central reclaimer piles of the coal yard; 9) Once the continuously observed deformation data all meet the allowable values, the site foundation treatment is complete, and coal can be freely piled up.

2. The method for treating the foundation of a strip coalfield with a portal stacker-reclaimer in soft soil areas according to claim 1, characterized in that... In step 1), the vacuum pre-compression process includes: 11) Level and clear the site, and lay a sand cushion layer; 12) Install plastic drainage boards on the site, and install clay mixing pile sealing walls around the perimeter of the vacuum preloading treatment area to block the permeable layer, and the clay mixing pile sealing walls should penetrate the silt layer of the site by no less than 1 meter. 13) Excavate filter pipe trenches and lay a vacuum network. The branch pipes of the network are connected to the ends of the plastic drainage boards, the main pipes are connected to the vacuum equipment, and vacuum monitoring equipment is installed. 14) Lay a layer of geotextile on the sand cushion layer, and then lay two layers of vacuum membrane on the geotextile. 15) Excavate a sealing trench around the vacuum sealing membrane and compact the silt in the trench to form a seal; 16) Perform pre-vacuuming, check the sealing system to ensure that the design vacuum pressure can be reached, and then perform stable vacuuming to make the vacuum degree at the end of the pipe reach the design standard value and maintain it for no less than 20 days; 17) Apply surcharge in stages on the site after pre-vacuuming, in the following order: first stage surcharge thickness 2.0 meters; second stage surcharge thickness 2.0 meters; third stage local surcharge thickness 2.5 meters; surcharge material is slag or other fill.

3. The method for treating the foundation of a strip coalfield with a portal stacker-reclaimer in soft soil areas according to claim 1, characterized in that... The outer structural piles and the central material reclaimer piles are selected as cast-in-place piles or precast pipe piles based on the detection information of the geological bearing layer.

4. The method for treating the foundation of a strip coalfield with a portal stacker-reclaimer in soft soil area according to claim 3, characterized in that... In step 4), the actual measurement of soil parameters includes: testing the bearing capacity of the surface foundation using shallow plate load test; testing the bearing capacity of soil at different depths using static cone penetration test; and obtaining the physical and mechanical parameters of the soil by means of indoor geotechnical tests.

5. A method for treating the foundation of a strip coalfield with a portal stacker-reclaimer in soft soil areas according to claim 4, characterized in that... In step 5), the monitoring information obtained by the monitoring points includes: horizontal displacement of deep soil, surface settlement, settlement and deformation of the feeder track foundation and the foundation of the outer protective structure, and excess pore water pressure of the coalfield foundation.

6. The method for treating the foundation of a strip coalfield with a portal stacker-reclaimer in soft soil area according to claim 5, characterized in that... When designing the graded coal pile structure, the finite element method is used to simulate and calculate the strength and deformation of the foundation soil under the load of each grade of coal pile, so as to estimate and determine the thickness and range of each grade of coal pile.

7. A method for treating the foundation of a strip coalfield with a portal stacker-reclaimer in soft soil areas, as described in claim 2, is characterized in that... In step 8), the monitoring and alarm indicators for the deformation data include: daily surface settlement of the backfill area exceeding 15 mm; and maximum daily lateral deformation of the soil exceeding 5 mm.

8. A method for treating the foundation of a strip coalfield with a portal stacker-reclaimer in soft soil areas according to claim 2, characterized in that, In steps 8) and 9), the frequency of continuous monitoring is as follows: once a month in the first year after production starts, and once a quarter in the second and third years; the allowable value standard for termination of monitoring is: the settlement increment of the foundation soil in the coal yard area for two consecutive six-month periods does not exceed 2mm.

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