Soft roadbed solid waste backfilling and dynamic compaction reinforcing method

Abstract

The invention relates to the technical field of roadbed treatment, and discloses a soft roadbed solid waste backfilling and dynamic compaction reinforcing method which comprises the following steps: early-stage preparation: carrying out detailed geological survey on an area where a soft roadbed is located, screening and treating proper solid waste materials, and carrying out dynamic compaction on the solid waste materials; making a solid waste backfilling and dynamic compaction reinforcement construction scheme according to an engineering investigation result and solid waste characteristics; subgrade cleaning: removing soft soil, sundries and vegetation on the surface of the soft subgrade; the solid waste materials are evenly laid on the soft roadbed in a layering mode, and the thickness of each layer is usually controlled to be 30-50 cm; preliminary compaction is conducted, specifically, each layer of solid waste backfilled on the soft roadbed is compacted through a light road roller; and trial ramming: closing. According to the method, 1%-2.5% of ammonium carbonate and 1%-2.5% of ammonium bicarbonate are added into the ground steel slag, so that the steel slag can be effectively removed, and the problems that free calcium oxide and free magnesium oxide are subjected to hydration reaction when encountering water to cause volume expansion, and a roadbed possibly bulges and cracks after backfilling are solved.

Description

Technical Field

[0001] The invention relates to the technical field of roadbed treatment, in particular to a method for backfilling solid waste and dynamically compacting and reinforcing a soft roadbed. Background Art

[0002] Backfilling of soft roadbed is of great significance. It can improve the stability of the roadbed, disperse the upper load, reduce the pressure on the soft soil layer, and reduce the risk of settlement and collapse. It can improve the drainage performance of the roadbed and use permeable backfill materials to accelerate the discharge of water and reduce the erosion and softening of the roadbed by water. It can also save engineering costs and use local soil materials, industrial waste residues and other resources for backfilling. The construction is simple and the construction period can be shortened. At the same time, it is beneficial to environmental protection and realizes the recycling of solid waste resources. It has a wide range of application scenarios. In road engineering, it can solve soft soil settlement, ensure road surface flatness and driving safety; in railway engineering, it can enhance the strength and stiffness of the roadbed, reduce track deformation, and improve the stability of train operation; in airport engineering, it can ensure the flatness and stability of the runway.

[0003] Steel slag is often used as solid waste backfill material in existing soft roadbeds. However, steel slag contains free calcium oxide and free magnesium oxide components. These components will undergo hydration reaction and expand in volume when they come into contact with water. Since the steel slag may not be sufficiently aged or stabilized during use, the backfilled steel slag still contains these components, which may cause problems such as roadbed bulging and cracking. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a method for solid waste backfilling and dynamic compaction reinforcement of a soft roadbed, which solves the problem that steel slag is often used as solid waste backfill material in the existing soft roadbed. However, the steel slag contains free calcium oxide and free magnesium oxide components, which will undergo hydration reactions and produce volume expansion when encountering water. Since the steel slag may not be sufficiently aged or stabilized during use, the steel slag after backfilling will still contain these components, which may cause the problem of roadbed bulging and cracking.

[0005] To achieve the above purpose, the present invention is implemented by the following technical scheme: a method for backfilling and dynamic compaction reinforcement of soft roadbed solid waste, comprising the following steps:

[0006] S1. Preliminary preparation: Conduct detailed geological surveys of the soft roadbed area, select and process suitable solid waste materials, and formulate solid waste backfill and dynamic compaction reinforcement construction plans based on engineering survey results and solid waste characteristics;

[0007] S2. Roadbed cleaning: remove the soft soil, debris and vegetation on the surface of the weak roadbed;

[0008] S3, Layered backfill: Use layered method to evenly lay solid waste materials on the soft roadbed, and the thickness of each layer is usually controlled at 30-50 cm;

[0009] S4. Preliminary compaction: Use a light roller to compact each layer of solid waste backfilled on the soft roadbed;

[0010] S5. Test tamping: tamping key points and representative locations;

[0011] S6, dynamic compaction: ramming and compacting the entire road surface;

[0012] S7. Effect testing: Static penetration test, standard penetration test and load test are used to evaluate the effect of the reinforced soft roadbed and analyze the soil density, bearing capacity and deformation modulus;

[0013] S8. Subsequent treatment: Smooth the surface of the reinforced roadbed, improve the roadbed drainage facilities and take protective measures for the roadbed.

[0014] Preferably, the solid waste materials in S1 are construction waste and industrial waste residues, wherein the construction waste includes waste concrete, brick and tile fragments and wood waste, and the industrial waste residue includes fly ash, steel slag and slag.

[0015] Preferably, the steel slag needs to be aged, ground and chemically stabilized before being backfilled in layers.

[0016] Preferably, the aging treatment includes natural aging and accelerated aging. For the natural aging, the steel slag is placed in a natural environment for 6-24 months. For the accelerated aging, the steel slag is placed in an aging bin, the internal ambient temperature of the aging bin is maintained at 50-80 degrees Celsius, and the relative humidity inside the aging bin is maintained at 60-80%, and the aging period is continued for 1-3 months.

[0017] Preferably, the grinding treatment uses a ball mill to grind the steel slag to a specific surface area of ​​400-600 square meters / kilogram. The particle size distribution of the steel slag after grinding is as follows: the content of particles below 0.075 mm accounts for 20%-30%, the content of particles between 0.075 mm and 4.75 mm accounts for 50%-60%, and the content of particles above 4.75 mm is controlled at 10%-20%.

[0018] Preferably, the chemical stabilization treatment includes carbonation treatment and chemical stabilization treatment. The carbonation treatment uses carbon dioxide gas for carbonation treatment, 50-100 cubic meters of carbon dioxide gas is introduced per ton of steel slag, 1%-2.5% of ammonium carbonate and 1%-2.5% of ammonium bicarbonate are mixed with the steel slag by a mixer for 30-50 minutes, and the chemical stabilization treatment uses a mixer to mix 1%-3% of sodium silicate with the steel slag for 25-45 minutes.

[0019] Preferably, the key points of the S5 test include the boundary area of ​​different soil types, the area of ​​groundwater level change, and the area near buildings or important facilities, and the representative positions include the central area of ​​the roadbed, the edge area of ​​the roadbed, and the area with the thickest soft soil layer.

[0020] Preferably, the number of tamping times of dynamic compaction in S6 is 8-15 times, the tamping energy is 10-30 tons, the drop distance of the tamping hammer is 5-20 meters, the distance between tamping points is 3-6 meters, and the interval time is 3-7 days.

[0021] The present invention provides a method for backfilling and dynamically compacting a soft roadbed with solid waste, which has the following beneficial effects:

[0022] 1. In the present invention, by adding 1%-2.5% of ammonium carbonate and 1%-2.5% of ammonium bicarbonate to the ground steel slag, free calcium oxide and free magnesium oxide components in the steel slag can be effectively removed. At the same time, 50-100 cubic meters of carbon dioxide gas is introduced into each ton of steel slag to further remove free calcium oxide and free magnesium oxide, thereby improving the existing steel slag commonly used for backfilling of soft roadbed solid waste, because it contains free calcium oxide and free magnesium oxide, which undergoes hydration reaction in water to cause volume expansion, and the steel slag may be aged or the stabilization treatment is insufficient, resulting in the problem of roadbed heave and cracking after backfilling.

[0023] 2. In the present invention, by tamping in the boundary area of ​​different soil types, the long-term accumulation of small uneven settlements and the bumpy feeling of the vehicle can be reduced; by tamping in the area where the groundwater level changes, it is possible to better adapt to water level fluctuations and reduce the small impact on underground pipelines and other facilities; by tamping in the area adjacent to buildings, the vibration interference to precision instruments in the buildings and the risk of small deformation of the buildings can be reduced; by tamping in the central area of ​​the roadbed, the fatigue resistance can be improved and the flatness of the road surface can be maintained; by tamping in the edge area of ​​the roadbed, the small erosion caused by natural factors and the driving discomfort can be reduced; by tamping in the thickest area of ​​the soft soil layer, long-term consolidation settlement can be resisted and the small deformation of underground facilities can be reduced, so that targeted tamping can improve the durability of the roadbed. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flow chart of the manufacturing process of the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Please refer to the attached Figure 1 The embodiment of the present invention provides a method for backfilling and dynamically compacting a soft roadbed with solid waste, which is characterized by comprising the following steps:

[0027] S1. Preliminary preparation: Conduct detailed geological surveys of the soft roadbed area, select and process suitable solid waste materials, and formulate solid waste backfill and dynamic compaction reinforcement construction plans based on engineering survey results and solid waste characteristics;

[0028] S2. Roadbed cleaning: remove the soft soil, debris and vegetation on the surface of the weak roadbed;

[0029] S3, Layered backfill: Use layered method to evenly lay solid waste materials on the soft roadbed, and the thickness of each layer is usually controlled at 30-50 cm;

[0030] S4. Preliminary compaction: Use a light roller to compact each layer of solid waste backfilled on the soft roadbed;

[0031] S5. Test tamping: tamping key points and representative locations;

[0032] S6, dynamic compaction: ramming and compacting the entire road surface;

[0033] S7. Effect testing: Static penetration test, standard penetration test and load test are used to evaluate the effect of the reinforced soft roadbed and analyze the soil density, bearing capacity and deformation modulus;

[0034] S8. Subsequent treatment: Smooth the surface of the reinforced roadbed, improve the roadbed drainage facilities and take protective measures for the roadbed.

[0035] The solid waste materials in S1 are construction waste and industrial waste residue. The construction waste includes waste concrete, brick and tile fragments and wood waste. The industrial waste residue includes fly ash, steel slag and slag.

[0036] Steel slag needs to be aged, ground and chemically stabilized before layered backfilling.

[0037] Specifically, aging treatment can make the unstable components in steel slag fully react and decompose, reduce the risk of its later expansion, and improve the stability after backfilling; grinding treatment can increase the specific surface area of ​​steel slag, improve its bonding performance with other materials, and increase the density and strength of the backfill body; chemical stabilization treatment can add chemical reagents to react with harmful substances in steel slag, reduce its activity, reduce potential pollution to the environment, and enhance the corrosion resistance and durability of steel slag; thereby effectively improving the engineering quality and environmental safety of steel slag in layered backfilling, and realizing rational utilization of resources and sustainable development.

[0038] The aging treatment includes natural aging and accelerated aging. In natural aging, the steel slag is placed in a natural environment for 6-24 months. In accelerated aging, the steel slag is placed in an aging bin, the internal ambient temperature of the aging bin is maintained at 50-80 degrees Celsius, and the relative humidity inside the aging bin is maintained at 60-80%, and it lasts for 1-3 months.

[0039] Specifically, natural aging places the steel slag in a natural environment for 6-24 months, which allows the unstable components in the steel slag to react slowly under natural conditions and gradually stabilize, reducing the risk of expansion and other problems caused by unstable components in the later layered backfilling. Accelerated aging places the steel slag in an aging bin in a specific environment, maintaining the temperature at 50-80 degrees Celsius and the relative humidity at 60-80% for 1-3 months, which can significantly accelerate the reaction rate of unstable substances in the steel slag, achieve a stabilization effect similar to natural aging in a shorter period of time, improve the stability and engineering applicability of the steel slag, and provide guarantees for the safe and reliable application of steel slag in layered backfilling. It also helps to improve resource utilization efficiency and reduce potential adverse effects on the environment.

[0040] Grinding treatment: use a ball mill to grind the steel slag to a specific surface area of ​​400-600 square meters / kilogram. The particle size distribution of the steel slag after grinding is as follows: the content of particles below 0.075 mm accounts for 20%-30%, the content of particles between 0.075 mm and 4.75 mm accounts for 50%-60%, and the content of particles above 4.75 mm is controlled at 10%-20%.

[0041] Specifically, the ground slag increases the specific surface area and improves the bonding ability with other materials. It can better interact with the filling materials in the layered backfilling, and improve the density and strength of the backfill body. The specific particle size distribution allows the slag to ensure that particles below 0.075 mm fill the gaps during the backfilling process, while particles between 0.075 mm and 4.75 mm provide support, and particles above 4.75 mm help to enhance the structural stability. Such treatment can improve the engineering quality of slag backfilling, reduce the risk of settlement, and make full use of slag resources, reduce dependence on natural resources, and achieve sustainable development.

[0042] Chemical stabilization treatment includes carbonation treatment and chemical stabilization treatment. For carbonation treatment, carbon dioxide gas is used for carbonation treatment. 50-100 cubic meters of carbon dioxide gas is introduced into each ton of steel slag. 1%-2.5% of ammonium carbonate and 1%-2.5% of ammonium bicarbonate are mixed with the steel slag by a mixer for 30-50 minutes. For chemical stabilization treatment, 1%-3% of sodium silicate is mixed with the steel slag by a mixer for 25-45 minutes.

[0043] Specifically, 50-100 cubic meters of carbon dioxide gas is introduced into each ton of steel slag, and 1%-2.5% of ammonium carbonate and 1%-2.5% of ammonium bicarbonate are mixed with the steel slag, which can cause the alkaline components in the steel slag to react with carbon dioxide, reduce the alkalinity of the steel slag, and reduce potential harm to the environment. At the same time, the products generated by the chemical reaction can enhance the stability of the steel slag. In the chemical stabilization treatment, 1%-3% of sodium silicate is mixed with the steel slag, which can further react with the active components in the steel slag to improve the corrosion resistance and durability of the steel slag. In this way, the free calcium oxide and free magnesium oxide components in the steel slag can be effectively removed, and the engineering performance of the steel slag can be effectively improved, making it safer and more reliable in layered backfilling, reducing the problem of heave and cracking that may occur in the later stage, realizing the resource recycling of steel slag, reducing the impact on the environment, and promoting sustainable development.

[0044] The key points of S5 test tamping include the boundary area of ​​different soil types, the area of ​​groundwater level change, and the area near buildings or important facilities. Representative locations include the center area of ​​the roadbed, the edge area of ​​the roadbed, and the area with the thickest soft soil layer.

[0045] Specifically, by conducting test tamping at the interface of different soil types, we can clarify the deformation and reinforcement characteristics of different soil types under tamping, and provide targeted solutions for overall foundation treatment; by paying attention to the area where the groundwater level changes, we can understand the impact of groundwater level fluctuations on the tamping effect, thereby optimizing precipitation or drainage measures to ensure the stability of the foundation; by conducting test tamping in areas adjacent to buildings or important facilities, we can effectively evaluate the impact of tamping vibration on them, take corresponding shock absorption or protection measures, and ensure the safety of buildings and important facilities. By selecting representative locations such as the center area of ​​the roadbed, the edge area of ​​the roadbed, and the thickest area of ​​the soft soil layer for test tamping, we can fully understand the settlement law, strength changes, and uneven settlement of the entire roadbed under tamping, provide a scientific basis for determining reasonable tamping parameters and optimizing construction technology, improve the overall quality and stability of the roadbed, and ensure the safety, reliability, and long-term performance of the project.

[0046] In S6, the number of tamping times for dynamic compaction is 8-15 times, the tamping energy is 10-30 tons, the drop distance of the tamping hammer is 5-20 meters, the distance between tamping points is 3-6 meters, and the interval time is 3-7 days.

[0047] Specifically, 8-15 times of tamping can ensure that the foundation soil is fully compacted, improving the bearing capacity and stability of the foundation; 10-30 tons of tamping energy can make the tamping effect penetrate into the soil layers of different depths, effectively reinforcing the deep soil; 5-20 meters of tamping hammer drop distance can ensure the effective transmission of tamping energy and enhance the impact and compaction effect on the soil; 3-6 meters of tamping point spacing can avoid repeated or missed tamping, so that the entire treatment area is evenly reinforced; and 3-7 days of interval time can allow the soil to have enough time to dissipate pore water pressure and adjust soil structure after each tamping, reduce the accumulation of excess pore water pressure caused by tamping, avoid the rubber soil phenomenon in the soil, and promote the recovery and growth of soil strength. The reasonable setting of these parameters can significantly improve the engineering performance of the foundation, ensure the safety and stability of buildings or infrastructure, reduce the risk of foundation settlement and uneven settlement, and extend the service life of the project.

[0048] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for backfilling and dynamic compaction reinforcement of soft roadbed solid waste, characterized by: The following steps are involved: S1. Preliminary preparation: Conduct detailed geological surveys of the soft roadbed area, select and process suitable solid waste materials, and formulate solid waste backfill and dynamic compaction reinforcement construction plans based on engineering survey results and solid waste characteristics; S2. Roadbed cleaning: remove the soft soil, debris and vegetation on the surface of the weak roadbed; S3, Layered backfill: Use layered method to evenly lay solid waste materials on the soft roadbed, and the thickness of each layer is usually controlled at 30-50 cm; S4. Preliminary compaction: Use a light roller to compact each layer of solid waste backfilled on the soft roadbed; S5. Test tamping: tamping key points and representative locations; S6, dynamic compaction: ramming and compacting the entire road surface; S7. Effect testing: Static penetration test, standard penetration test and load test are used to evaluate the effect of the reinforced soft roadbed and analyze the soil density, bearing capacity and deformation modulus; S8. Subsequent treatment: Smooth the surface of the reinforced roadbed, improve the roadbed drainage facilities and take protective measures for the roadbed.

2. The method for backfilling and dynamic compaction reinforcement of soft roadbed solid waste according to claim 1 is characterized by: The solid waste materials in S1 include construction waste and industrial waste residues. The construction waste includes waste concrete, brick and tile fragments, and wood waste. The industrial waste residue includes fly ash, steel slag, and ore slag.

3. The method for backfilling and dynamic compaction reinforcement of soft roadbed solid waste according to claim 2 is characterized in that: The steel slag needs to be aged, ground and chemically stabilized before backfilling in layers.

4. The method for backfilling and dynamically compacting a soft roadbed according to claim 3 is characterized in that: The aging treatment includes natural aging and accelerated aging. In the natural aging, the steel slag is placed in a natural environment for 6-24 months. In the accelerated aging, the steel slag is placed in an aging bin, the internal ambient temperature of the aging bin is maintained at 50-80 degrees Celsius, and the relative humidity inside the aging bin is maintained at 60-80% for 1-3 months.

5. The method for backfilling and dynamically compacting a soft roadbed according to claim 3 is characterized in that: The grinding treatment uses a ball mill to grind the steel slag to a specific surface area of ​​400-600 square meters / kilogram. The particle size distribution of the steel slag after grinding is as follows: the content of particles below 0.075 mm accounts for 20%-30%, the content of particles between 0.075 mm and 4.75 mm accounts for 50%-60%, and the content of particles above 4.75 mm is controlled at 10%-20%.

6. The method for backfilling and dynamically compacting a soft roadbed according to claim 3 is characterized in that: The chemical stabilization treatment includes carbonation treatment and chemical stabilization treatment. The carbonation treatment uses carbon dioxide gas for carbonation treatment. 50-100 cubic meters of carbon dioxide gas is introduced into each ton of steel slag. A mixer is used to mix 1%-2.5% of ammonium carbonate and 1%-2.5% of ammonium bicarbonate with the steel slag for 30-50 minutes. The chemical stabilization treatment uses a mixer to mix 1%-3% of sodium silicate with the steel slag for 25-45 minutes.

7. The method for backfilling and dynamically compacting a soft roadbed according to claim 1 is characterized in that: The key points of the S5 test include the boundary area of ​​different soil types, the area of ​​groundwater level change, and the area near buildings or important facilities. The representative locations include the central area of ​​the roadbed, the edge area of ​​the roadbed, and the area with the thickest soft soil layer.

8. The method for backfilling and dynamically compacting a soft roadbed according to claim 1 is characterized in that: The number of tamping times of dynamic compaction in S6 is 8-15 times, the tamping energy is 10-30 tons, the drop distance of the tamping hammer is 5-20 meters, the distance between tamping points is 3-6 meters, and the interval time is 3-7 days.

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