Polymer-reinforced sand subgrade structure and construction method thereof

Abstract

This invention discloses a polymer-reinforced silt and sand subgrade structure and its construction method. The structure comprises, from top to bottom, an asphalt pavement layer, a crushed stone layer, a waterproof layer, and a "soil-wrapped sand" subgrade structure consisting of a graded crushed stone layer, a stepped polymer-modified silt and sand layer, and a subgrade soil layer. The construction method involves uniformly injecting a penetrating polymer grout into the already formed stepped original silt and sand layer using a pressure grouting process. This grout penetrates, encapsulates, and binds sand particles within the sand layer, thereby reinforcing the original silt and sand layer as a whole into a high-strength, water-stable polymer-modified silt and sand layer. This invention creatively applies polymer grouting technology to the construction of new subgrades, effectively solving the technical problem of poor road performance of unsuitable fillers such as Yellow River silt and sand. It has the advantages of high strength, rapid construction, controllable quality, and economy.

Description

Technical Field

[0001] This invention relates to the field of roadbed technology, and more specifically, to a polymer-reinforced mud-sand roadbed structure and its construction method. Background Technology

[0002] With the deepening implementation of the national strategies of "Building a Strong Transportation Nation" and "Ecological Protection and High-Quality Development of the Yellow River Basin," the demand for high-quality, green fillers for infrastructure construction such as highways in the region is becoming increasingly urgent. The silty fine sand widely distributed in the Yellow River Plain has engineering characteristics such as low bearing capacity, poor stability, and high permeability. Although abundant in resources, it is difficult to use directly as roadbed filler for highways. An existing invention patent with publication number CN118563605A improves the road performance of silt through a "soil-wrapped sand" physical structure design, but its mechanical properties, durability, and water stability have not been significantly improved. Especially under long-term immersion or high-temperature environments, the roadbed is prone to softening or cracking. While traditional cement curing methods can improve short-term strength, the brittleness and cracking of cement materials often prevent the achievement of expected stability in practical applications, and its high cost limits large-scale application. Therefore, there is an urgent need for a new, improved method that combines high strength, low permeability, and good economic efficiency to enhance the performance of silty sand roadbeds.

[0003] On the other hand, polymer grouting technology, as an efficient foundation reinforcement method, has been applied in the maintenance of existing roads. For example, Academician Wang Fuming's patent (CN101261263B) discloses a method for identifying roadbed defects and rapidly reinforcing it with polymer grouting based on non-destructive testing. Its core is to utilize the expansibility of polymer materials to fill voids and insufficiently compacted areas in existing roadbeds, representing a "passive remedial" maintenance technique. Currently, the application of polymer grouting technology to new roadbeds as a means of actively enhancing the performance of poor fillers is relatively rare. In particular, how to combine the excellent properties of polymers (such as high permeability, early strength, and strong water stability) with a novel roadbed structure (such as a "soil-encased sand" structure) to form a high-performance new roadbed solution integrating materials and structure is a pressing technical problem that needs to be solved. Summary of the Invention

[0004] The present invention aims to overcome the shortcomings of the prior art and provide a polymer-reinforced silt and sand roadbed structure and its construction method, so as to achieve overall reinforcement of the silt and sand filling while improving its utilization rate.

[0005] To achieve the above objectives, the present invention provides a construction method for a polymer-reinforced silt subgrade structure. The method includes the following steps: S1, pre-treating the silt and controlling the moisture content of the treated silt within a preset range; S2, laying a graded crushed stone layer on the foundation, and then filling and compacting it in layers to form a stepped original silt layer. Simultaneously, filling and compacting subgrade soil layers on both sides of each original silt layer to form a lateral wrapping structure for the silt layer; S3, after the stepped original silt layer is filled and compacted, using a pressure grouting device, uniformly injecting a penetrating polymer grout into the original silt layer. Under pressure, the grout penetrates and fills the pores between the silt particles, and after in-situ consolidation, forms a polymer-modified silt layer.

[0006] S4 involves sequentially laying a waterproof layer, a crushed stone layer, and an asphalt pavement layer on top of the polymer-modified silt layer and the subgrade structure.

[0007] Optionally, in S1, the pretreatment step for the sediment includes:

[0008] The silt is loosened to remove soil clumps formed under natural sedimentation conditions, and large-diameter particles and plant roots and stems are removed from the silt using vibrating screening equipment to clear the slurry infiltration channels.

[0009] Optionally, in S1, the step of controlling the moisture content of the sediment includes:

[0010] The actual moisture content of the treated sediment was measured and compared with the optimum moisture content. If the difference exceeded ±5%, the moisture content was adjusted to the target range by drying or sprinkling water.

[0011] Optionally, in S2, a geogrid is laid on the graded crushed stone layer before the original mud and sand layer is laid on the surface of the graded crushed stone layer.

[0012] Optionally, in S3, the grouting pressure is controlled between 0.1 MPa and 0.3 MPa to ensure effective diffusion of the grout in the mud and sand, and the grouting time is adjusted between 60 seconds and 150 seconds according to the diffusion radius requirement.

[0013] Optionally, in S3, the grouting process adopts a layered step-by-step grouting process: the original mud and sand layer is grouted layer by layer from bottom to top. When grouting each layer, a perforated self-drilling grouting pipe is used, and grout holes are reserved at the end of the grouting pipe to ensure that the grout penetrates evenly into the pores of the sand layer.

[0014] Optionally, in S3, a surface settlement monitoring method is used for real-time quality monitoring during the grouting process to achieve quantitative determination of the grouting saturation degree: settlement observation points are set up in each grouting area to record the surface elevation changes before and after grouting in real time. When the average settlement difference between the two previous observations is ≤2mm, the area is considered to be grouting saturated and grouting is stopped; grouting is carried out in areas where the settlement change does not meet the standard until the requirements are met.

[0015] Optionally, in S3, the permeable polymer slurry is a two-component material, with the volume ratio of component A to component B being 1:1, wherein component A includes a composite polyether polyol, a surfactant, and a flame retardant; and component B includes a polyisocyanate and an auxiliary catalyst.

[0016] Optionally, in S3, the polymer-modified mud and sand layer can achieve high strength within half an hour after grouting is completed, without the need for additional curing, and the next construction process can be carried out directly.

[0017] Optionally, a slope protection layer (8) is provided on the slope, wherein the slope protection layer (8) is a vegetation protection layer.

[0018] Optionally, the thickness of each original sediment layer is controlled at 25±5cm.

[0019] Furthermore, in order to achieve the above objectives, the present invention also provides a polymer-reinforced silt subgrade structure obtained by any of the above construction methods, wherein the silt subgrade structure includes a subgrade structure and a waterproof layer, a crushed stone layer, and an asphalt pavement layer sequentially laid on top of the subgrade structure; the subgrade structure includes a graded crushed stone layer at the bottom and a stepped polymer-modified silt layer and a subgrade soil layer laid on the graded crushed stone layer, wherein the subgrade soil layer is laid on both sides of the polymer-modified silt layer.

[0020] Optionally, the top of the polymer-modified silt layer and the top of the subgrade soil layer are located on the same plane and in contact with the waterproof layer.

[0021] Optionally, after the polymer-modified silt layer is treated with a permeable polymer slurry, it forms a continuous cemented structure that penetrates the pores of the silt, thereby significantly improving its mechanical strength, reducing its permeability, and exhibiting good water stability; preferably, its strength can be increased by more than 6 times, its permeability coefficient can be reduced by 3 orders of magnitude, and its strength loss rate after immersion in water for 7 days is no more than 15%.

[0022] Beneficial effects:

[0023] (1) The construction method of the present invention innovatively applies polymer grouting technology to the field of new roadbed, and improves the overall performance of mud and sand with poor road performance. It fundamentally improves the bearing capacity and water stability of mud and sand roadbed, and effectively expands the resource utilization of local poor filler.

[0024] (2) The construction sequence of “first forming the skeleton and then grouting to enhance” is adopted. A stable initial structure of “soil-wrapped sand” is formed first, and then the core mud and sand layer is improved as a whole. This not only ensures the stability of the construction process, but also ensures that the polymer grout can effectively penetrate and solidify in the target area, and the quality of the project is highly controllable.

[0025] (3) The surface settlement detection method is used to monitor the grouting improvement process in real time. This not only avoids insufficient or excessive grouting, but also allows for timely detection of areas with uneven improvement effects and timely replenishment, ensuring the uniformity and reliability of the performance of the polymer-modified mud and sand layer.

[0026] (4) The resulting roadbed structure has a high-strength, low-permeability polymer-modified mud and sand core inside and a roadbed soil protective layer with a stable slope outside. The two are closely combined through a stepped interface to form a composite roadbed system that works together, with good overall stability and durability. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating the construction method of the present invention.

[0028] Figure 2 This is a cross-sectional schematic diagram of a polymer-reinforced silt subgrade structure according to an embodiment of the present invention. The numbers in the diagram are: 1-graded crushed stone layer, 2-subgrade soil layer, 3-polymer-modified silt layer, 4-waterproof layer, 5-crushed stone layer, 6-asphalt pavement layer, 7-slope protection layer. Detailed Implementation

[0029] 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. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0030] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description.

[0031] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0032] like Figure 1The diagram shows a flowchart of an embodiment of a construction method for a polymer-reinforced silt-sand roadbed structure provided by the present invention, wherein the method includes the following steps:

[0033] S1: Pre-treatment of sediment and control of moisture content.

[0034] Specifically, silt from the Yellow River Plain is selected. The silt particles are mainly fine sand, possessing low bearing capacity and stability, and high permeability, making it unsuitable for direct use as roadbed fill. First, the selected silt is transported to the construction site and stockpiled for subsequent processing. During stockpiling, it is crucial to ensure the silt surface is protected from rainwater erosion or external contamination, avoiding excessive moisture content that could affect subsequent construction. Then, mechanical loosening equipment is used to loosen the silt, eliminating clumps and dense areas formed by natural sedimentation, ensuring effective penetration of the grout between the silt particles. Next, vibrating screening equipment is used to remove particles larger than 5mm, plant roots, and other debris, ensuring the silt is free of particles that could hinder grout penetration and consolidation. Finally, the silt is uniformly mixed manually or mechanically to ensure a uniform particle size distribution, preventing large particles from obstructing the grout penetration channels.

[0035] Furthermore, a moisture meter was used to test the moisture content of the sediment. According to design requirements, the moisture content of the sediment was controlled at approximately 15%–20% to facilitate slurry penetration and particle bonding. If the moisture content of the sediment was too high, it needed to be reduced by sun-drying; if the moisture content was too low, it could be adjusted by sprinkling water.

[0036] S2: Laying of graded crushed stone layer, geogrid, silt layer and slope protection layer, specifically including the following steps:

[0037] S21 involves laying a graded crushed stone layer on the construction base. Its purpose is to enhance the stability of the roadbed and provide a solid foundation for subsequent silt and sand layers. The thickness of the graded crushed stone is controlled at 20cm, with a particle size of 10-20mm. Mechanical compaction equipment is used to ensure that the density meets design requirements. The surface of the graded crushed stone layer should be smooth and free of cracks to avoid instability in subsequent structures due to uneven thickness of the base layer.

[0038] S22, a geogrid is laid on the surface of the graded crushed stone layer. The geogrid is made of high-strength polyester fiber or polypropylene material, which can maintain its structural stability and tensile strength under long-term loads. The geogrid should be laid flat, avoiding wrinkles or air bubbles, to ensure its performance under subgrade loads;

[0039] Specifically, during the laying process, the joints of the geogrid should overlap by 30-50cm to ensure that the tensile strength at the joint is consistent with the rest. In addition, the edges of the geogrid should be properly pressed into the graded crushed stone layer to prevent displacement during construction.

[0040] S23 involves laying a stepped layer of original mud and sand on top of the graded crushed stone layer. Each layer of mud and sand is controlled to a thickness of 25±5cm, and is constructed in layers to ensure that the compaction of each layer meets design requirements. During the filling process, each layer of mud and sand is thoroughly compacted using mechanical equipment to enhance its stability.

[0041] S24, a slope protection layer is installed on the slope of the roadbed soil layer. This slope protection layer consists of vegetation and has good ecological functions and protective effects. The vegetation layer selects drought-resistant and wind-resistant plants suitable for local climate conditions to ensure that the vegetation can grow stably in the natural environment, further improving the stability and long-term durability of the roadbed.

[0042] S3: Prepare a penetrating polymer slurry and perform grouting treatment on the original mud and sand layer. The specific steps are as follows:

[0043] S31, the grouting process uses a penetrating polymer grout, which is composed of two components, A and B, mixed in a 1:1 volume ratio. Component A consists of a composite polyether polyol, surfactant, and flame retardant, while component B consists of a polyisocyanate and a catalyst. The grout density is approximately 1.1 g / cm³, and the preferred viscosity is 240–265 mPa·s to ensure good permeability. Before grouting, a pressure grouting device is used for testing to ensure stable operation and uniform grout flow rate, avoiding uneven grouting. During construction, the grouting pressure can be adjusted according to the difference in moisture content of the sediment; for example, a lower grouting pressure is used in areas with higher moisture content, while the grouting pressure is appropriately increased in dry areas. The grouting time is adjusted according to the pore structure of the sediment and the diffusion radius of the grout, generally controlled between 60 and 150 seconds to ensure that the grout can fully penetrate into every pore of the sediment.

[0044] S32 employs a layered, stepped grouting process, starting from the bottom layer and grouting the original mud and sand layers one by one. Before grouting each layer, settlement observation points are set up to monitor surface settlement and monitor the grouting effect in real time. During grouting, a perforated self-drilling grouting pipe is used to ensure that the grout can penetrate evenly into each mud and sand layer.

[0045] After each layer of grouting is completed, surface settlement monitoring should be used to determine whether the grouting has reached saturation. If insufficient settlement is found, additional grouting should be carried out immediately until the designed settlement standard is met. Additionally, it is recommended to equip the site with emergency grouting equipment to ensure the stability of construction progress and quality in case of unforeseen construction situations.

[0046] S33 grouting forms a three-dimensional continuous cemented network structure with a certain strength within approximately 30 minutes after grouting, eliminating the need for traditional curing treatment and allowing subsequent construction to proceed. This innovative process significantly improves construction efficiency and shortens the construction cycle.

[0047] S4: A waterproof layer, a crushed stone layer, and an asphalt pavement layer are laid sequentially on top of the roadbed structure.

[0048] After the polymer-modified silt layer is grouted, a waterproof layer is laid sequentially. This 5cm thick waterproof layer, made of high-molecular polymer material, effectively prevents water penetration and protects the polymer-modified silt layer from moisture. Following the waterproof layer, a 10cm thick crushed stone layer is laid, using 5-10mm diameter crushed stone to enhance roadbed stability and distribute loads. Finally, an 8cm thick asphalt pavement layer is laid, using hot-mix asphalt. During construction, the pavement surface is ensured to be smooth and even, meeting the requirements for transportation use.

[0049] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A polymer-reinforced silt and sand roadbed structure, characterized in that, The silt and sand roadbed structure includes: The bottom graded crushed stone layer (1); A roadbed structure laid on a graded crushed stone layer (1), the roadbed structure comprising an original mud and sand layer formed by filling and compaction and a roadbed soil layer (2) laid on both sides thereof; And a waterproof layer (4), a crushed stone layer (5), and an asphalt pavement layer (6) are laid on top of the roadbed structure. In this process, after the original mud and sand layer is filled and compacted, a penetrating polymer grout is uniformly injected and penetrated and solidified by pressure grouting to form a polymer-modified mud and sand layer (3) that penetrates the pores of the mud and sand layer and is cemented together with the in-situ mud and sand particles.

2. The polymer-reinforced silt roadbed structure according to claim 1, characterized in that, A geogrid is laid between the graded crushed stone layer (1) and the bottom polymer-modified silt layer (3).

3. The polymer-reinforced silt roadbed structure according to claim 1, characterized in that, A slope protection layer (7) is provided on the side slope of the roadbed soil layer (2) away from the mud and sand layer (3), and the slope protection layer (7) is a vegetation protection layer.

4. The polymer-reinforced silt roadbed structure according to claim 1, characterized in that, The permeable polymer slurry is a two-component material with a volume ratio of 1:1 between component A and component B. Component A includes a composite polyether polyol, a surfactant, and a flame retardant; component B includes a polyisocyanate and an auxiliary catalyst.

5. The polymer-reinforced silt roadbed structure according to claim 4, characterized in that, The permeable polymer slurry has fluidity suitable for penetrating into the pores of mud and sand under pressure, and can complete gel solidification within a preset time after injection to form a stable cemented structure.

6. The polymer-reinforced silt roadbed structure according to claim 5, characterized in that, After being treated with a permeable polymer slurry, the polymer-modified silt layer exhibits significantly improved mechanical strength, markedly reduced permeability, and good water stability.

7. A construction method for a polymer-reinforced silt-sand subgrade structure as described in any one of claims 1-6, characterized in that, The construction method includes: S1. Pre-treat the silt and control its moisture content within a preset range; S2. Lay a graded crushed stone layer on the foundation, and then fill and compact it in layers to form a stepped original silt layer. At the same time, fill and compact the subgrade soil layer on both sides of each original silt layer to form a lateral wrapping structure for the silt layer; S3. After the stepped original silt layer is filled and compacted, use pressure grouting equipment to evenly inject penetrating polymer grout into the original silt layer. Under pressure, the grout penetrates and fills the pores between the silt particles, and after in-situ consolidation, forms a polymer-modified silt layer. S4 involves sequentially laying a waterproof layer, a crushed stone layer, and an asphalt pavement layer on top of the polymer-modified silt layer and the subgrade structure.

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