Construction method for filling roadbed with bagged broken solidified soil

Abstract

The invention discloses a construction method for filling a roadbed with bagged broken solidified soil, and relates to the technical field of road engineering and dredged sludge solidification resource utilization. According to the construction method, through the technological process of solidification, crushing, screening, bagging and layered filling, the overall solidified soil which is large in size, prone to cracking and poor in gradation is converted into gradation artificial aggregate with the controllable particle size and the good compaction degree, and the gradation artificial aggregate is used for roadbed filling in a bagged unit mode. Compared with a traditional in-situ overall curing or fluid curing method, the method has the advantages that the grading and compaction performance of the cured soil can be remarkably improved, and the roadbed filler structure is more uniform and controllable; the stability and durability of the curing material are improved through lateral restraint and water control and air permeability of the bag body, and the risks of cracking and water damage are reduced. The method is simple and convenient in construction process, can be combined with field machinery to realize continuous operation, and is beneficial to in-situ resource utilization of a large amount of dredged sludge and popularization and application of road foundation engineering.

Description

A construction method for roadbed filling with bagged crushed and solidified soil Technical Field

[0001] This invention relates to the field of road engineering and the resource utilization technology of dredged sludge solidification, and in particular to a construction method for filling roadbeds with bagged crushed and solidified soil. Background Technology

[0002] With the continuous advancement of urban water environment management, river dredging, and coastal land reclamation projects, the output of dredged silt is showing a rapid upward trend. This type of soil generally possesses engineering properties such as high water content, loose structure, low strength, high compressibility, and poor particle size distribution. If used directly in road foundation engineering without treatment, it often leads to problems such as insufficient bearing capacity, difficulty in compaction, long consolidation time, and difficulty in controlling subsequent settlement. Currently, traditional disposal methods such as off-site transportation and landfill are commonly used in projects. However, this method not only incurs high transportation costs but also occupies a large amount of land resources, imposes a heavy environmental burden, and is inconsistent with the concepts of "dual carbon" and green construction.

[0003] Silt solidification technology has received widespread attention as an important approach to resource utilization. Currently, the common practice is fluidized bed solidification, but this still has significant limitations: fluidized bed solidified soil has a large volume, high overall block rigidity, and poor on-site mobility, making it difficult to meet the requirements of roadbed fill for compaction and deformation coordination; solidified blocks are prone to developing through cracks during later water loss, leading to decreased mechanical properties and insufficient durability, making them unreliable as road filling materials; and it is difficult to achieve controllable gradation, making it unsuitable for roadbed projects with high load-bearing requirements.

[0004] In summary, current technologies still lack a comprehensive system that can simultaneously address multiple requirements, including improved sludge solidification strength, controllable aggregate gradation, convenient filling and construction, and good roadbed integrity. Therefore, there is an urgent need to develop a construction method suitable for large-volume dredged sludge to achieve efficient resource utilization of dredged sludge and meet the dual requirements of road engineering for mechanical and construction performance. Summary of the Invention

[0005] The purpose of this invention is to provide a construction method for filling roadbeds with bagged, crushed, and solidified soil, thereby solving the problems existing in the prior art. This invention utilizes dredged sludge, which is solidified, crushed, screened, and bagged for roadbed filling. This method is particularly suitable for large-scale sludge disposal projects and road infrastructure construction in areas with dense water systems, enabling large-scale, efficient, and engineered resource utilization of dredged sludge, while meeting the dual requirements of road engineering for mechanical and construction performance.

[0006] To achieve the above objectives, the present invention provides the following solution: The technical solution of the present invention is a construction method for filling roadbeds with bagged crushed and solidified soil, comprising the following steps: adding flocculant to dredged sludge for flocculation and dewatering; adding multi-source solid waste-based solidifying agent and chopped solid waste fibers to the flocculated and dewatered sludge, stirring evenly, and then solidifying and curing to obtain solidified soil; crushing and multi-stage screening of the solidified soil to obtain graded artificial aggregate; filling the graded artificial aggregate into water-controlling and breathable composite woven bags, compacting them by vibration, and then sealing them to obtain bagged crushed and solidified soil; laying the bagged crushed and solidified soil in layers on the roadbed base, leaving gaps between adjacent bags of crushed and solidified soil during each layer, filling the gaps with artificial aggregate with a particle size of 2-5 mm as filler, and compacting the bagged crushed and solidified soil and filler (to form a dense whole), laying layer by layer until the roadbed design elevation is reached.

[0007] The construction method of this invention, through a process of "solidification—crushing—screening—bagging—layered filling," transforms the originally bulky, crack-prone, and poorly graded monolithic solidified soil into graded artificial aggregate with controllable particle size and good compaction, which is then used in bagged units for roadbed filling. Compared with traditional fluidized solidification methods, this invention significantly improves the gradation and compaction of the solidified soil, making the roadbed fill structure more uniform and controllable. The lateral constraint and water-controlling permeability of the bags enhance the stability and durability of the solidified material, reducing the risk of cracking and water damage. This method is simple to construct and can be combined with on-site machinery for continuous operation, facilitating the on-site resource utilization of large volumes of dredged silt and its widespread application in road foundation engineering.

[0008] Furthermore, the flocculant includes inorganic polymeric flocculants and / or organic polymeric flocculants.

[0009] Preferably, the flocculant comprises polyaluminum chloride and / or polyacrylamide.

[0010] Furthermore, the mass of the flocculant is 1.0% of the mass of the dredged sludge.

[0011] Preferably, continuous stirring is maintained during the addition of the flocculant to ensure uniform dehydration.

[0012] Furthermore, the moisture content of the dredged silt is greater than 100%.

[0013] Preferably, the water content of the sludge after flocculation and dewatering is 75-85%.

[0014] The natural moisture content of dredged sludge generally exceeds 100% during excavation and mechanical transportation. By adding flocculants for flocculation and dewatering treatment, the moisture content is reduced and controlled within the range of 75-85% to meet the requirements of subsequent solidification treatment.

[0015] Further, by mass percentage, the raw materials of the multi-source solid waste-based solidifying agent include: blast furnace slag powder: 40-60%; steel slag powder: 20-35%; desulfurized gypsum: 8-15%; auxiliary solid waste: 5-15%; activator: 0.5-3%; wherein, the auxiliary solid waste includes one or more of fly ash, tailings powder and red mud.

[0016] Blast furnace slag powder provides the main potential hydraulic activity, steel slag powder continuously replenishes the calcium source and maintains the alkaline environment, desulfurized gypsum promotes the formation of ettringite to improve early strength and volume stability, auxiliary solid waste improves structural density through volcanic ash reaction and filling effect, activator synergistically stimulates the activity of various solid wastes and accelerates the formation of cementitious products. The above components work together to construct a stable and dense cementitious structure and achieve good solidification effect.

[0017] Furthermore, the activator includes an alkaline activator and / or a sulfate activator.

[0018] Preferably, the alkaline activator includes one or more of sodium hydroxide, calcium hydroxide, potassium hydroxide, and water glass; the sulfate activator includes one or more of sodium sulfate, calcium sulfate, and aluminum sulfate.

[0019] Furthermore, the preparation steps of the multi-source solid waste-based solidifying agent include: weighing each raw material according to the mass ratio, mixing them, and then grinding them to a specific surface area of ​​not less than 400 m². 2 / kg, to obtain the multi-source solid waste-based solidifying agent.

[0020] This multi-source solid waste-based solidifier can significantly increase the contact area between slag powder, steel slag powder, desulfurization gypsum and auxiliary solid waste and activator by increasing the specific surface area of ​​particles, thereby enhancing their dissolution rate and reactivity, accelerating the formation rate of hydration products such as CSH, CASH and AFt, and improving particle size distribution and filling effect, thus improving the early strength development, density and long-term stability of the system.

[0021] Furthermore, the amount of the multi-source solid waste-based solidifying agent added is 3-15% of the dry mass of the flocculated and dewatered sludge, preferably 5-10%.

[0022] Furthermore, the chopped solid waste fibers include one or more of lignin fibers, waste polypropylene fibers, recycled polyester fibers, and waste fishing net fibers, preferably lignin fibers.

[0023] Furthermore, the length of the chopped solid waste fibers is less than 3 mm.

[0024] Furthermore, the amount of the chopped solid waste fiber added is 2% of the sum of the mass of the flocculated and dewatered sludge and the multi-source solid waste-based solidifying agent (i.e., (dry mass of the flocculated and dewatered sludge + mass of the multi-source solid waste-based solidifying agent) × 2%).

[0025] Preferably, the curing process specifically involves curing at room temperature for 72 hours.

[0026] Furthermore, the maximum particle size of the graded artificial aggregate does not exceed 1 / 6 of the short side dimension of the water-controlling and breathable composite woven bag, the gradation fractal dimension is 2.0 to 2.5, and the California Load-Bearing Ratio (CBR) is not less than 10%.

[0027] Furthermore, the water-controlling and breathable composite woven bag has a double-layer structure, with an outer polypropylene woven layer and an inner polyethylene microporous water-controlling and breathable membrane.

[0028] Furthermore, the water permeability coefficient of the water-controlling and breathable composite woven bag is no greater than 1×10⁻⁶. -9 cm / s, air permeability not less than 100 kg / (m²) 2 (24h), ultimate tensile strength not less than 20 kN / m, ultimate elongation not greater than 20%.

[0029] Furthermore, the filling rate of the water-controlling and breathable composite woven bag is not less than 90%, and the filling rate is calculated according to formula (1): (1) Where: m1 is the mass of graded artificial aggregate filled in the water-control and breathable composite woven bag, in kg; m max The maximum mass of graded artificial aggregate that can be filled into a water-controlled and breathable composite woven bag is determined through a bagging test. When the filling mass exceeds this value, the bag opening cannot be sealed smoothly. The unit is kg.

[0030] Furthermore, the sealing is achieved through heat pressing and sewing, specifically by first heat pressing the seal and then reinforcing the seal edge with double-line sewing.

[0031] Furthermore, a gap of 3-5 cm is maintained between adjacent bagged crushed and solidified soil layers during each layer's installation.

[0032] Furthermore, the artificial aggregate with a particle size of 5-10 mm used to fill the gaps is obtained by crushing and screening the solidified soil.

[0033] Furthermore, adjacent layers of bagged crushed and solidified soil are arranged in a staggered cross pattern to avoid vertical through joints.

[0034] Furthermore, the compaction includes static compaction and vibratory compaction, specifically compaction until the compaction degree of the bagged crushed and solidified soil is not less than 95%.

[0035] Compaction degree (P) refers to the measured dry density (ρ) of graded artificial aggregate in bagged crushed and solidified soil. d The ratio of the maximum dry density to the maximum dry density (ρ) dmax The maximum dry density was obtained through indoor standard compaction tests on the graded artificial aggregate used in bagged crushed and solidified soil. The measured dry density was obtained on-site using the sand cone method or ring cutter method. According to formula (2), P=ρ d / ρ dmax ×100% Calculate the compaction degree.

[0036] Optionally, the flocculation and dewatering are carried out in a flocculation tank, and the solidification and curing are carried out in a mixing tank, with the flocculation tank and the mixing tank located near the dredging construction area.

[0037] Optionally, the mixing tanks are configured in two or more for batch curing to meet continuous processing requirements.

[0038] The present invention discloses the following technical effects: (1) The solidified soil is crushed and screened to form graded artificial aggregate with controllable gradation, which overcomes the problems of large volume, easy cracking and difficult construction of traditional solidified soil.

[0039] (2) The compacted and solidified soil unit after bagging has high density and good integrity, and can form a highly stable roadbed structure system after being laid.

[0040] (3) By relying on multi-source solid waste-based solidifying agents and solid waste short-cut fibers, the low-carbon utilization of dredged sludge can be realized, significantly reducing transportation and landfill costs, and achieving a double improvement in environmental and engineering benefits.

[0041] (4) The continuous and efficient treatment of large-volume dredged sludge is achieved through the “flocculation dewatering + multi-pool solidification” process, which greatly improves the resource utilization efficiency. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 is a schematic diagram of the construction method of using bagged crushed and solidified soil to fill roadbed in this invention.

[0044] Figure 2 is a schematic diagram of the flocculation tank of the present invention.

[0045] Figure 3 shows the gradation curve of the artificial aggregate of crushed and solidified soil according to the present invention.

[0046] Figure 4 is a schematic diagram of the water-controlling and breathable composite woven bag of the present invention.

[0047] Figure 5 is a schematic diagram of the bagged crushed and solidified soil of the present invention.

[0048] Figure 6 is a schematic diagram of the roadbed filling method using bagged crushed and solidified soil according to the present invention.

[0049] Figure 7 shows the results of the plate load test in this invention.

[0050] Figure 8 is a schematic diagram of the unconfined compression test in this invention.

[0051] Figure 9 shows the results of the unconfined compression test in this invention. Detailed Implementation

[0052] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0053] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0054] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0055] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0056] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0057] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0058] As an embodiment of the present invention, the present invention provides a construction method for filling roadbed with bagged crushed and solidified soil, comprising the following steps: adding flocculant to dredged sludge for flocculation and dewatering; adding multi-source solid waste-based solidifying agent and chopped solid waste fibers to the flocculated and dewatered sludge, stirring evenly, and then solidifying and curing to obtain solidified soil; crushing and multi-stage screening of the solidified soil to obtain graded artificial aggregate; filling the graded artificial aggregate into water-controlling and breathable composite woven bags, compacting them by vibration, and then sealing them to obtain bagged crushed and solidified soil; laying the bagged crushed and solidified soil in layers on the roadbed base, leaving gaps between adjacent bags of crushed and solidified soil during each layer, filling the gaps with artificial aggregate with a particle size of 2~5 mm as filler, and compacting the bagged crushed and solidified soil and filler, laying layer by layer until the roadbed design elevation is reached.

[0059] As a preferred embodiment of the present invention, the construction method for filling roadbed with bagged crushed and solidified soil includes the following steps: setting up a flocculation tank and two or more mixing tanks near the dredging construction area; the flocculation tank is used for flocculation and dewatering of large-volume dredged sludge, and the multiple mixing tanks are used for batch solidification and curing to meet continuous processing requirements; introducing the dredged sludge into the flocculation tank through a conveying pipeline; adding flocculant to the dredged sludge in the flocculation tank and stirring to cause rapid flocculation and dewatering; opening the discharge structure of the flocculation tank to allow the flocculated and dewatered sludge to fall into the excavator bucket and be transported by the excavator to the mixing tank; adding flocculant to the flocculated and dewatered sludge in the mixing tank. Multi-source solid waste-based solidifying agent is prepared according to a preset ratio, and short-cut solid waste fibers are added. The mixture is thoroughly stirred using a large mixing device, followed by solidification and curing. The cured soil is then fed into a crusher using an excavator for crushing. The crushed solidified soil undergoes multi-stage screening to obtain graded artificial aggregates that meet mechanical performance requirements. These graded artificial aggregates are packed into water-control and breathable composite woven bags, compacted by vibration, and then sealed to obtain bagged crushed solidified soil. The roadbed base is leveled, and the bagged crushed solidified soil is laid in layers on the treated base. Gaps are maintained between adjacent bags of crushed solidified soil during each layer, and these gaps are filled with artificial aggregates with a particle size of 2-5 mm. After each layer is laid, a vibratory roller is used for static and vibratory compaction to form a dense whole. The upper and lower layers of bagged crushed solidified soil are arranged in a staggered cross pattern to avoid vertical through-joints. The above steps are repeated until the roadbed design elevation is reached.

[0060] In a preferred embodiment of the present invention, the flocculation tank is provided with an openable side door on one side, and four support legs and a set of lifting devices at the bottom; the support legs are used to lift the flocculation tank as a whole to a preset height above the ground, and the lifting devices are used to adjust the height of one end of the flocculation tank so that the flocculation tank forms a predetermined inclination angle, so that when the side door is opened, the flocculated and dewatered sludge can flow out to the lower area by gravity; the preset height should at least meet the requirements of the excavator bucket entering the lower part of the flocculation tank to receive and transfer the dropped material.

[0061] As a preferred embodiment of the present invention, the flocculation tank and its supporting legs have sufficient structural rigidity and are preferably made of iron or other metal materials to meet the stability requirements of long-term repeated use and bearing large-volume sludge dewatering conditions.

[0062] In a preferred embodiment of the present invention, the flocculant includes inorganic polymeric flocculant and / or organic polymeric flocculant, preferably polyaluminum chloride and / or polyacrylamide; the mass of the flocculant is 1.0% of the mass of the dredged sludge, and continuous stirring is maintained during the addition of the flocculant to ensure uniform dehydration.

[0063] In a preferred embodiment of the present invention, the dredged sludge has a moisture content greater than 100%, and the sludge after flocculation and dewatering has a moisture content of 75-85%.

[0064] In a preferred embodiment of the present invention, the mixing tank is located near the flocculation tank, preferably a tank-shaped structure formed by excavation of the ground, and two or more mixing tanks are provided to adapt to the characteristic that the flocculation dewatering time is significantly shorter than the solidification and curing time, thereby realizing continuous discharge from the flocculation tank and parallel solidification and curing treatment in multiple tanks.

[0065] As a preferred embodiment of the present invention, the raw materials of the multi-source solid waste-based solidifying agent, by mass percentage, include: blast furnace slag powder: 40-60%; steel slag powder: 20-35%; desulfurized gypsum: 8-15%; auxiliary solid waste: 5-15%; activator: 0.5-3%; wherein, the auxiliary solid waste includes one or more of fly ash, tailings powder and red mud.

[0066] In a preferred embodiment of the present invention, the activator includes an alkaline activator and / or a sulfate activator.

[0067] In a preferred embodiment of the present invention, the alkaline activator includes one or more of sodium hydroxide, calcium hydroxide, potassium hydroxide, and water glass; the sulfate activator includes one or more of sodium sulfate, calcium sulfate, and aluminum sulfate.

[0068] In a preferred embodiment of the present invention, the preparation steps of the multi-source solid waste-based solidification agent include: weighing each raw material according to the mass ratio, mixing them, and then grinding them to a specific surface area of ​​not less than 400 m². 2 / kg, to obtain the multi-source solid waste-based solidifying agent.

[0069] In a preferred embodiment of the present invention, the amount of the multi-source solid waste-based solidifying agent added is 3-15% of the dry mass of the sludge after flocculation and dewatering, preferably 5-10%.

[0070] In a preferred embodiment of the present invention, the chopped solid waste fiber includes one or more of lignin fiber, waste polypropylene fiber, recycled polyester fiber and waste fishing net fiber, preferably lignin fiber.

[0071] In a preferred embodiment of the present invention, the length of the chopped solid waste fiber is less than 3 mm, and the amount added is 2% of the sum of the mass of the flocculated and dehydrated sludge and the industrial solid waste solidifying agent.

[0072] In a preferred embodiment of the present invention, the curing process specifically involves curing at room temperature for 72 hours.

[0073] In a preferred embodiment of the present invention, the maximum particle size of the graded artificial aggregate does not exceed 1 / 6 of the short side dimension of the water-controlling and breathable composite woven bag, the gradation fractal dimension is 2.0 to 2.5, and the California Load-Bearing Ratio (CBR) is not less than 10%.

[0074] In a preferred embodiment of the present invention, the water-controlling and breathable composite woven bag has a double-layer structure, with an outer polypropylene woven layer and an inner polyethylene microporous water-controlling and breathable membrane.

[0075] In a preferred embodiment of the present invention, the water permeability coefficient of the water-controlling and air-permeable composite woven bag is not greater than 1×10⁻⁶. -9 cm / s, air permeability not less than 100 kg / (m²) 2 (24h), ultimate tensile strength not less than 20 kN / m, ultimate elongation not greater than 20%.

[0076] In a preferred embodiment of the present invention, the sealing is achieved by heat pressing and sewing, specifically by first heat pressing the seal and then reinforcing the seal edge with double-line sewing.

[0077] In a preferred embodiment of the present invention, the filling rate of the water-controlling and breathable composite woven bag is not less than 90%, and the filling rate is calculated according to formula (1): (1) Where: m1 is the mass of graded artificial aggregate filled in the water-control and breathable composite woven bag, in kg; m maxThe maximum mass of graded artificial aggregate that can be filled into a water-controlled and breathable composite woven bag is determined through a bagging test. When the filling mass exceeds this value, the bag opening cannot be sealed smoothly. The unit is kg.

[0078] In a preferred embodiment of the present invention, the gap between adjacent bagged crushed and solidified soil is 3-5 cm when each layer is laid.

[0079] In a preferred embodiment of the present invention, the artificial aggregate with a particle size of 2-5 mm filling the gaps is obtained by crushing and screening the solidified soil.

[0080] In a preferred embodiment of the present invention, the compaction specifically refers to compaction until the compaction degree of the bagged crushed and solidified soil is not less than 95%.

[0081] Compaction degree (P) refers to the measured dry density (ρ) of graded artificial aggregate in bagged crushed and solidified soil. d The ratio of the maximum dry density to the maximum dry density (ρ) dmax The maximum dry density was obtained through indoor standard compaction tests on the graded artificial aggregate used in bagged crushed and solidified soil. The measured dry density was obtained on-site using the sand cone method or ring cutter method. According to formula (2), P=ρ d / ρ dmax ×100% Calculate the compaction degree.

[0082] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0083] In the following embodiments and comparative examples of the present invention, room temperature refers specifically to 20~30℃.

[0084] Unless otherwise specified, all raw materials used in the following embodiments and comparative examples of this invention are commercially available products.

[0085] Figure 1 shows a schematic flowchart of the construction method for filling roadbed with bagged crushed and solidified soil in the following embodiments of the present invention.

[0086] Example 1 A construction method for filling roadbed with bagged crushed and solidified soil (flow diagram shown in Figure 1) The steps are as follows: (1) Preparation of bagged crushed and solidified soil A flocculation tank is set up near the dredging construction area. The side wall of the flocculation tank is equipped with an openable side door, and the bottom is equipped with four metal support legs and a set of lifting devices (the schematic diagram of the flocculation tank is shown in Figure 2). The support legs can lift the flocculation tank to a height of about 1 m, so that the excavator bucket can smoothly enter below it to receive the discharge; the lifting device is used to adjust the height of one end of the flocculation tank so that the tank body forms an inclination angle, so that the dewatered sludge can flow out from the side door. The flocculation tank and the support legs are made of steel or other metal materials, with high structural rigidity, which meets the long-term load requirements of large-volume sludge dewatering conditions.

[0087] High-moisture-content dredged sludge (150% moisture content) was introduced into the flocculation tank via a conveying pipeline. Polyaluminum chloride flocculant (1.0% of the dredged sludge mass) was added, and the mixture was stirred evenly using a paddle mixer to rapidly flocculate and agglomerate. After standing for 2 hours, the sludge moisture content decreased to 80%. The flocculation tank discharge structure was then opened, allowing the flocculated and dewatered sludge to fall into the excavator bucket under its own weight. When the remaining sludge in the flocculation tank could not fall naturally, a lifting device was used to raise the end opposite the side door, allowing the sludge to be discharged smoothly along the inclined direction. The side door was then closed, and the next batch of flocculation and dewatering was circulated.

[0088] The flocculated and dewatered sludge (i.e., dewatered sludge) is transported by excavator to the first of five mixing tanks located near the flocculation tank. The mixing tank is a pool-like structure formed by excavation on-site, allowing for multi-tank rotation for solidification and improving overall treatment efficiency. 8% (by weight) of a multi-source solid waste-based solidifying agent (composed of 50 wt% blast furnace slag powder, 30 wt% steel slag powder, 10 wt% desulfurized gypsum, 8 wt% fly ash, and 2 wt% water glass mixed in a specific ratio and then ground to a specific surface area of ​​450 m²) is added to the dewatered sludge with a moisture content of 80%. 2 (The mixture is obtained at / kg), and 2 wt% lignin fiber with a length less than 3 mm is added, the amount being the sum of the dry weight of the dewatered sludge and the weight of the multi-source solid waste-based solidifying agent. The mixture is thoroughly stirred using a large mixing device to ensure uniform dispersion of the solidifying agent and fiber. The mixture is then cured at room temperature for 72 hours to form solidified soil. The remaining mixing tanks are fed and cured sequentially using the same process, achieving continuous operation of flocculation dewatering and solidification curing.

[0089] The cured and stabilized soil is fed into a crusher by an excavator for crushing and then subjected to multi-stage screening to obtain graded artificial aggregate. The graded artificial aggregate must meet the following indicators: the maximum particle size does not exceed 1 / 6 of the short side dimension of the water-control and breathable composite woven bag (the bagged crushed and stabilized soil is handled manually, so the weight of a single bag needs to be controlled within 30-50 kg for easy handling; water-control and breathable composite woven bags with a size of 60 cm × 80 cm are selected, and the overall size of the filled bagged crushed and stabilized soil is 40 cm × 40 cm × 12 cm to achieve the above single bag weight requirement); the gradation fractal dimension is 2.0~2.5; and the California Bearing Ratio (CBR) is ≥10%. In this embodiment, the particle size range of the graded artificial aggregate is 2~25 mm, the gradation fractal dimension is 2.5, and the CBR value is 12% (obtained from the artificial aggregate gradation curve shown in Figure 3).

[0090] After the graded artificial aggregate is loaded into a water-controllable and breathable composite woven bag (a schematic diagram of the water-controllable and breathable composite woven bag is shown in Figure 4), it is vibrated to compact it. The bag opening is then sealed by heat pressing and sewing. Specifically, the bag is first heat-pressed and then double-stitched to reinforce the sealing edge, forming bagged crushed and solidified soil (a schematic diagram of bagged crushed and solidified soil is shown in Figure 5). The water-controllable and breathable composite woven bag used in this embodiment has the following structure and properties: the outer layer is a polypropylene woven layer with an equivalent pore size of O 95 The inner layer is a polyethylene microporous water-controlling and breathable membrane with a diameter of 0.30 mm and an average pore size of 0.50 μm, resulting in a porosity of 50%. The bag has an ultimate tensile strength of 25 kN / m, an ultimate tensile rate of 18%, and a permeability coefficient of 1.0 × 10⁻⁶. -10 cm / s, air permeability is 150 kg / (m²) 2 •24h).

[0091] The filling rate (η) of graded artificial aggregate in the water-controlled and breathable composite woven bag is 90%, which is calculated according to formula (1): (1) Where: m1 is the mass of graded artificial aggregate filled in the water-control and breathable composite woven bag, in this embodiment m1=482.5kg; m max To determine the maximum mass of graded artificial aggregate that can be filled into a water-controlled and breathable composite woven bag, a bagging test was conducted. When the filling mass exceeds this value, the bag opening cannot be sealed smoothly. In this embodiment, m... max =490.0 kg.

[0092] (2) The roadbed is cleaned, leveled and compacted in the construction site, and the flatness is controlled to be ≤10 mm. The steps of laying the bag body (i.e. bagged crushed solidified soil) are as follows: the first layer of bag body is laid in the transverse direction of the roadbed, so that the long side is parallel to the cross section of the road, and a gap of 3~5cm is maintained between adjacent bags; the second layer and above bags are arranged in a cross-stitch manner, as shown in Figure 6. The upper layer of bag body crosses the center line of the lower layer of bag body to avoid the appearance of a through vertical weak surface; after each layer of bag body is laid, artificial aggregate with a particle size range of 2~5 mm (obtained by crushing and screening the solidified soil cured in step (1)) is filled into the gap and compacted in layers by a small vibratory rammer so that the bag body and the filling material form a dense whole; specifically, a 10 t vibratory roller is used for static pressure + vibration pressure until the compaction degree is 96%. The compaction degree (P) is calculated according to formula (2), i.e. P=ρ d / ρ dmax Calculate by multiplying by 100%, where ρ dmax The maximum dry density, specifically 1.68 g / cm³, was obtained through indoor standard compaction tests on continuously graded artificial aggregate used in bagged crushed and solidified soil. 3 , ρ dThe measured dry density was obtained at the construction site using the sand cone method, specifically 1.62 g / cm³. 3 .

[0093] In this embodiment, six layers are laid with a thickness of 12 cm each, ultimately achieving a designed roadbed height of 0.72 m. A 0.2 m thick gravel cushion layer is placed on top to improve the flatness and load-bearing capacity of the construction surface.

[0094] Comparative Example 1: This comparative example uses the same dredged silt source as Example 1 and prepares graded artificial aggregates using the same preparation process, except that it does not use water-controlled and breathable composite woven bags to bag and constrain the graded artificial aggregates.

[0095] Specifically, the construction steps of Comparative Example 1 are as follows: After the dredged sludge is treated with polyaluminum chloride flocculation and dewatering, the moisture content is adjusted to 80%. 8% of the dry weight of the dewatered sludge (using a multi-source solid waste-based solidifying agent) and 2 wt% of the sum of the dry weights of the dewatered sludge and the multi-source solid waste-based solidifying agent (using lignin fiber) are added to the dewatered sludge. After mixing evenly, the mixture is cured at room temperature for 72 hours to form solidified soil blocks. The solidified soil is then crushed and screened through multiple stages to obtain continuously graded artificial aggregate with a particle size range of 5–25 mm, a fractal dimension of 2.5, and a CBR of 12%. The obtained continuously graded artificial aggregate is then directly layered onto the roadbed without bagging, with each layer being 12 cm thick. A 10-ton vibratory roller is used for static and vibratory compaction until the compaction degree reaches 96%. A total of 6 layers are filled, ultimately forming a roadbed structure layer with the same height (0.72 m) as in Example 1. Finally, a 0.2 m thick gravel cushion layer is placed on top to improve the flatness and load-bearing capacity of the construction surface.

[0096] Comparative Example 2 uses the same dredged sludge source, flocculation and dewatering process, multi-source solid waste-based solidifying agent ratio, solid waste short fiber type and dosage, solidification and curing conditions, crushing and screening process, and graded artificial aggregate performance indicators as Example 1. The only difference is that the bag used to fill the graded artificial aggregate is an ordinary woven bag, which does not have water control and air permeability function, that is, it only has a polypropylene woven layer and no polyethylene microporous water control and air permeability membrane.

[0097] Test Example 1 evaluates the difference in bearing capacity between the subgrade structures of Example 1 and Comparative Example 1. Plate load tests were conducted on two sections of the test subgrade. A rigid square steel plate with a side length of 1.0 m and a thickness of 30 mm was used as the loading plate. Vertical loads were applied in eight stages (200 kPa, 400 kPa, 600 kPa, 800 kPa, 1000 kPa, 1200 kPa), maintaining the load until the measured settlement rate dropped below 0.5 mm / h before proceeding to the next load stage. The load-settlement relationship curves under each load stage were recorded to evaluate the difference in bearing capacity between the two subgrades. The results are shown in Figure 7. The proportional limit determined at the transition point between the linear and nonlinear parts of the curves in Figure 7 is approximately 400 kPa. The settlement without bagging is 33.2 mm, and the settlement with bagging is 27.7 mm. This indicates that bagging reinforcement improves the overall bearing capacity of the subgrade. Therefore, compared with the direct filling method without bags, the bagged crushed and solidified soil unit formed by water-controlled and breathable composite woven bags provides an effective lateral restraint effect and improves the overall bearing capacity of the fill material.

[0098] Test Example 2 was conducted to verify the performance of the bagged crushed and solidified soil of the present invention. This test example included unconfined compressive strength tests on the water-controlled and breathable composite woven bag crushed and solidified soil (40 cm × 40 cm × 12 cm) prepared in Example 1, the ordinary woven bag crushed and solidified soil (40 cm × 40 cm × 12 cm) prepared in Example 2, and an unbagged ordinary crushed and solidified soil sample (a schematic diagram of the test is shown in Figure 8). The specific preparation process of the unbagged ordinary crushed and solidified soil sample was as follows: Continuously graded artificial aggregate obtained according to the process in Example 1 was filled into a rigid steel mold in layers and compacted by vibration. The inner cavity of the steel mold had dimensions of 40 cm × 40 cm × 12 cm, consistent with the outer dimensions of the bagged crushed and solidified soil. During the filling process, three layers were filled, and each layer was compacted using a small vibratory compactor until it matched the measured dry density of the bagged crushed and solidified soil. After compaction, the steel mold was removed, resulting in a large unbagged ordinary crushed and solidified soil sample with dimensions of 40 cm × 40 cm × 12 cm. The unconfined compressive strength test results are shown in Figure 9. Ordinary fractured and solidified soil exhibits low initial stiffness, a rapid decrease after the peak value, and brittle failure. In contrast, the compression test results of the water-controlled and breathable composite woven bag-packed fractured and solidified soil prepared in Example 1 and the ordinary woven bag-packed fractured and solidified soil prepared in Example 2 show little difference; the compression curves are gentle, with no failure, demonstrating good ductility and toughness. At 6.5% strain, the unconfined compressive strength of both types of bagged fractured and solidified soil is approximately 215 kPa, while the unconfined compressive strength of ordinary fractured and solidified soil is approximately 154 kPa. These results indicate that the water-controlled and breathable composite woven bag used in this invention can effectively improve the compressive strength of fractured and solidified soil.

[0099] Based on this, to further investigate the structural stability and softening resistance of the water-controlled and breathable composite woven bag-packed crushed and solidified soil under water immersion conditions, water immersion durability tests were conducted on samples of the water-controlled and breathable composite woven bag-packed crushed and solidified soil prepared in Example 1, the ordinary woven bag-packed crushed and solidified soil prepared in Comparative Example 2, and the unpacked ordinary crushed and solidified soil. All three types of samples were simultaneously placed in a room temperature water bath and completely submerged. The water temperature was controlled at 20±2 ℃, and the soaking time was 7 days. During this period, the water level was maintained at least 50 mm above the top of the sample, and the water was changed every 24 hours to avoid external environmental influences and to prevent the accumulation of dissolved products from interfering with the test results. The test results showed that the unpacked ordinary crushed and solidified soil sample began to soften and structurally deteriorate after 3 days of immersion. Peeling and loosening occurred at the edges and surface of the sample, and significant hydrolysis and disintegration even occurred in some areas, ultimately making it difficult to maintain its intact shape. In Comparative Example 2, the crushed and solidified soil sample packaged in a regular woven bag maintained its overall morphology initially during immersion. However, as the immersion time increased, water rapidly entered the bag through the larger pores. After 4 days of immersion, the solidified aggregate inside the bag gradually absorbed water and softened, with localized loss of fine particles and loosening of the aggregate structure. After 7 days of immersion and removal of the bag, a decrease in the structural integrity of the internal solidified soil and a significant increase in apparent moisture content were observed. Localized softening and spalling remained to varying degrees. While the overall durability was better than the unbagged sample, significant water erosion and degradation were still present. In contrast, the crushed and solidified soil sample packaged in a water-controlled and breathable composite woven bag prepared in Example 1 maintained a stable overall morphology under the covering and lateral confinement of the water-controlled and breathable composite woven bag. After 7 days of immersion and removal of the bag, the internal solidified soil structure remained intact, without hydrolysis or disintegration. The material did not show significant softening, and the apparent moisture content remained essentially unchanged, with no significant water infiltration or migration. The results show that the water-controlling and breathable composite woven bag used in this invention can effectively inhibit the direct intrusion of liquid water into the solidified aggregate, avoid the loss of fine particles and damage to the structural skeleton, thereby significantly improving the durability and stability of the crushed and solidified soil in a water immersion environment.

[0100] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A construction method for filling roadbeds with bagged crushed and solidified soil, characterized in that, Includes the following steps: Flocculant is added to dredged sludge for flocculation and dewatering; multi-source solid waste-based solidifying agent and chopped solid waste fibers are added to the flocculated and dewatered sludge, and after stirring evenly, solidification and curing are carried out to obtain solidified soil; the solidified soil is crushed and screened in multiple stages to obtain graded artificial aggregate; the graded artificial aggregate is packed into water-control and breathable composite woven bags, compacted by vibration, and then sealed to obtain bagged crushed solidified soil; The bagged crushed and solidified soil is laid in layers on the subgrade base. When laying each layer, gaps are left between adjacent bagged crushed and solidified soil. Artificial aggregate with a particle size of 2~5 mm is filled into the gaps as filler. The bagged crushed and solidified soil and filler are compacted. The layers are laid one by one until the subgrade design elevation is reached.

2. The construction method for roadbed filling with bagged crushed and solidified soil as described in claim 1, characterized in that, The flocculant includes inorganic polymeric flocculants and / or organic polymeric flocculants; and / or, the mass of the flocculant is 1.0% of the mass of the dredged sludge.

3. The construction method for roadbed filling with bagged crushed and solidified soil as described in claim 1, characterized in that, The raw materials of the multi-source solid waste-based solidifying agent, by mass percentage, include: blast furnace slag powder: 40-60%; steel slag powder: 20-35%; desulfurized gypsum: 8-15%; auxiliary solid waste: 5-15%; activator: 0.5-3%; wherein the auxiliary solid waste includes one or more of fly ash, tailings powder and red mud.

4. The construction method for roadbed filling with bagged crushed and solidified soil as described in claim 3, characterized in that, The preparation steps of the multi-source solid waste-based solidification agent include: weighing each raw material according to the mass ratio, mixing them, and then grinding them to a specific surface area of ​​not less than 400 m². 2 / kg, to obtain the multi-source solid waste-based solidifying agent; and / or, the amount of the multi-source solid waste-based solidifying agent added is 3 to 15% of the dry mass of the flocculated and dewatered sludge.

5. The construction method for roadbed filling with bagged crushed and solidified soil as described in claim 1, characterized in that, The chopped solid waste fibers include one or more of lignin fibers, waste polypropylene fibers, recycled polyester fibers, and waste fishing net fibers; and / or, the amount of chopped solid waste fibers added is 2% of the sum of the dry mass of the flocculated and dewatered sludge and the mass of the multi-source solid waste-based solidifying agent.

6. The construction method for roadbed filling with bagged crushed and solidified soil as described in claim 1, characterized in that, The maximum particle size of the graded artificial aggregate does not exceed 1 / 6 of the short side dimension of the water-controlling and breathable composite woven bag, the gradation fractal dimension is 2.0 to 2.5, and the California load-bearing ratio is not less than 10%.

7. The construction method for roadbed filling with bagged crushed and solidified soil as described in claim 1, characterized in that, The water-controlling and breathable composite woven bag has a double-layer structure, with an outer polypropylene woven layer and an inner polyethylene microporous water-controlling and breathable membrane.

8. The construction method for roadbed filling with bagged crushed and solidified soil as described in claim 1, characterized in that, The water permeability coefficient of the water-controlled and breathable composite woven bag is no greater than 1×10⁻⁶. -9 cm / s, air permeability not less than 100 kg / (m²) 2 (24h), ultimate tensile strength not less than 20 kN / m, ultimate elongation not greater than 20%.

9. The construction method for roadbed filling with bagged crushed and solidified soil as described in claim 1, characterized in that, The filling rate of the water-control and breathable composite woven bag is not less than 90%.

10. The construction method for roadbed filling with bagged crushed and solidified soil as described in claim 1, characterized in that, When laying each layer, the gap between adjacent bagged crushed and solidified soil is 3-5 cm; and / or, adjacent layers of bagged crushed and solidified soil are arranged in a cross-stitch pattern.

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