Fiber EPS light soil roadbed backfill soil suitable for cold regions and preparation method of fiber EPS light soil roadbed backfill soil

Abstract

The invention discloses fiber EPS light soil roadbed backfill soil suitable for a cold region and a preparation method thereof, belongs to the field of roadbed filling materials in geotechnical engineering, and particularly relates to the fiber EPS light soil roadbed backfill soil suitable for the cold region and the preparation method of the fiber EPS light soil roadbed backfill soil. The foundation pit soil is composed of foundation pit raw material soil, a curing agent, EPS particles and fibers. The polypropylene fibers are filled in cracks between the EPS particles and the soil body to form a layer of net-shaped bonding, and the polypropylene fibers and the EPS particles interact with each other to form the EPS particle light soil. The method is suitable for highway subgrade filling in cold regions, can effectively prevent the problems of highway subgrade settlement, abutment bumping and the like, can also be used for widening a road side slope, and has the advantages of simple construction method and low engineering cost.

Description

Technical Field

[0001] The present invention belongs to the field of subgrade filling materials in geotechnical engineering, and particularly relates to a fiber EPS lightweight soil subgrade backfill soil applicable to cold regions and a preparation method thereof. Background Art

[0002] At present, with the continuous progress of highway engineering technology, traditional subgrade fillers such as lime soil have exposed many intractable problems in practical applications, especially in the scenario of highway construction in cold regions, where a series of engineering problems frequently occur.

[0003] Due to the special climate and geological conditions in cold regions, situations such as excessive filling load, insufficient foundation bearing capacity, or foundation frost heave are extremely likely to occur, thereby causing serious problems that affect the service performance and safety of highways, such as subgrade settlement and differential settlement of road widening. When carrying out subgrade construction in a low-temperature environment, the external temperature is often too low, and icing may occur on some road subgrades. Once the water in the soil pores freezes, the volume of the soil will expand, which seriously interferes with the normal performance of the original subgrade and is one of the key causes of many diseases in cold-region subgrades. When the weather warms up and the temperature rises, the frozen subgrade changes from a frozen state to a semi-wet and semi-frozen state. After the ice melts, the volume shrinks, and the subgrade settles accordingly. This process not only causes the subgrade strength to decrease again but also is very likely to cause problems such as subgrade frost heave and mud pumping. In severe cases, it may even cause the subgrade to collapse, greatly threatening the traffic safety and durability of the highway.

[0004] In the face of these subgrade construction problems in cold regions, there have been various traditional countermeasures in the past. For example, the drainage open ditch method is adopted during construction, attempting to relieve problems such as frost heave by diverting water flow and reducing the accumulation of water in the subgrade; a lateral drainage ditch is set on the side of the subgrade, also to drain surface water in a timely manner and reduce the risk of the subgrade being damaged by water; the slush soil in the road subgrade is replaced with crushed stones, hoping to improve the subgrade condition by utilizing the good water permeability and stability of the crushed stones; and the compaction degree is strictly controlled to ensure the density of the subgrade and improve its bearing capacity. However, these traditional methods have obvious shortcomings in practical applications. They are often costly, requiring a large amount of manpower, material resources, and financial resources; the treatment process is extremely complex, involving multiple construction links and technical key points, and demanding high professional qualities of construction personnel and construction management levels; moreover, during the construction process, it will affect the normal use of the highway to varying degrees, bringing many inconveniences to traffic travel, and even may cause traffic interruption, resulting in economic losses and social impacts.

[0005] In view of the various drawbacks of traditional subgrade fillers and countermeasures, it is urgent to develop a new, efficient, and economical subgrade construction plan. Summary of the Invention

[0006] In view of the problems existing in the above content, the present invention provides a fiber EPS lightweight soil subgrade backfill soil suitable for cold regions and a preparation method thereof.

[0007] A fiber EPS lightweight soil subgrade backfill soil suitable for cold regions is composed of foundation pit raw soil, a curing agent, EPS particles and fibers; wherein the mass of the curing agent is 9% of the foundation pit raw soil, the mass of the EPS particles is 0.2 - 0.8% of the foundation pit raw soil, and the mass of the fibers is 0.5 - 2% of the foundation pit raw soil.

[0008] A preparation method of a fiber EPS lightweight soil subgrade backfill soil suitable for cold regions is completed according to the following steps:

[0009] First, dry the foundation pit raw soil at 100 °C, and then grind it through a 2 mm sieve using a grinder to obtain dried raw soil.

[0010] Second, mix the dried raw soil with the curing agent, add water for stirring after mixing evenly; after stirring evenly, add fibers and EPS particles in sequence, and continue to stir to form a uniform flocculent fiber EPS particle lightweight soil.

[0011] Advantages of the present invention:

[0012] On the basis of traditional subgrade materials, the present invention improves its mechanical properties and practical performance and applies it to subgrade construction tasks in cold regions. The main features are as follows: 1) By analyzing real subgrade construction cases and accident cases, EPS particles (polyethylene propylene) are added to replace the original soil to improve the frost heaving resistance of the soil and prevent problems such as subgrade frost heaving and mud pumping; at the same time, the density of the soil will also decrease with the incorporation of EPS particles, which can effectively reduce the load caused by self-weight and control the harm caused by foundation settlement; EPS particles, also called expandable polystyrene, inherently have characteristics such as aging resistance and corrosion resistance, and have been called "white pollution" in recent years. Utilizing EPS particles in subgrade filling can effectively achieve "turning waste into treasure and making use of waste". 2) As an inorganic fiber, polypropylene fiber itself has advantages such as light weight, high strength, and good elasticity. When polypropylene fiber is added to the EPS particle lightweight soil, the polypropylene fiber forms a network bond in the soil, firmly connecting the EPS particles and lime soil tightly. Compared with the specimens without adding polypropylene fiber, the fiber EPS particle lightweight soil has obvious ductility after failure, and the specimens do not show the phenomenon of "breaking into slag" after unloading. Therefore, the addition of polypropylene fiber can effectively enhance the strength and integrity of the lightweight soil. 3) The new type of subgrade material provided by the present invention suitable for cold regions has the advantages of simple mixing, convenient transportation, and convenient construction. Its characteristics provide a new idea for studying the prevention of subgrade settlement in cold regions and have practical significance. Description of the Drawings

[0013] Figure 1 It is a physical diagram of a Marshall electric compactor;

[0014] Figure 2 It is a secondary curve graph of water content - dry density in the compaction experiment;

[0015] Figure 3 It is a physical diagram of a microcomputer - controlled electronic universal testing machine;

[0016] Figure 4 It is a flow chart of specimen failure in the unconfined compressive strength test;

[0017] Figure 5 It is a comparison diagram in the freeze - thaw cycle test; on the right is the addition of EPS particles, and on the left is without the addition of EPS particles. Specific embodiments

[0018] The technical solution of the present invention is not limited to the specific embodiments listed below, and also includes any combination between specific embodiments.

[0019] Specific embodiment one: A kind of fiber - EPS lightweight soil subgrade backfill soil applicable to cold regions in this embodiment is composed of foundation pit raw soil, curing agent, EPS particles and fibers; among them, the mass of the curing agent is 9% of the foundation pit raw soil, the mass of the EPS particles is 0.2 - 0.8% of the foundation pit raw soil, and the mass of the fibers is 0.5 - 2% of the foundation pit raw soil.

[0020] The new subgrade filler of this embodiment can not only effectively reduce the construction cost and relieve the economic pressure brought by traditional methods, but also significantly improve the frost heave resistance of the subgrade, effectively guarantee the stability of the subgrade under the complex climate conditions in cold regions; at the same time, it greatly enhances the strength of the subgrade and extends its service life, which has inestimable significance for subgrade construction in cold regions and injects new vitality and solutions into the field of cold - region highway construction.

[0021] In this embodiment, EPS particles are added to the subgrade filler to reduce the load brought by the self - weight of the subgrade and enhance the frost heave resistance of the subgrade soil. Polypropylene fibers are added to improve the strength and toughness of the EPS lightweight soil. The well - mixed polypropylene fibers act between the EPS particles and the lime soil to form a high - strength bond, which can not only improve the ductility of the subgrade but also effectively resist the load transmitted from the upper part.

[0022] Specific embodiment two: The difference between this embodiment and specific embodiment one is that: the mass of the curing agent is 9% of the foundation pit raw soil, the mass of the EPS particles is 0.2% of the foundation pit raw soil, and the mass of the fibers is 1% of the foundation pit raw soil. Others are the same as specific embodiment one.

[0023] Embodiment 3: The difference between this embodiment and Embodiment 1 is that the physical property parameters of the raw soil in the foundation pit are as follows: water content is 17.5%, liquid limit is 42.4%, plastic limit is 29.35%, and plasticity index is 13.1%. Others are the same as those in Embodiment 1.

[0024] Embodiment 4: The difference between this embodiment and Embodiment 1 is that the curing agent is lime. Others are the same as those in Embodiment 1.

[0025] Embodiment 5: The difference between this embodiment and Embodiment 1 is that the particle diameter of the EPS particles is 2 - 3 mm, and the particle bulk density is 0.013 g / cm 3 . Others are the same as those in Embodiment 1.

[0026] Embodiment 6: The difference between this embodiment and Embodiment 1 is that the fiber is polypropylene fiber. Others are the same as those in Embodiment 1.

[0027] Embodiment 7: The difference between this embodiment and Embodiment 1 is that the physical property parameters of the polypropylene fiber are as follows: fiber length is 6 mm, fiber diameter is 32.7 μm, density is 0.91 g / cm 3 , tensile strength is 469 Mpa, ultimate elongation is 28.4%, and elastic modulus is 28.4 Mpa. Others are the same as those in Embodiment 1.

[0028] Embodiment 8: A preparation method of fiber - EPS lightweight soil subgrade backfill soil applicable to cold regions in this embodiment is completed according to the following steps:

[0029] 1. Dry the raw soil in the foundation pit at 100 °C, and then grind it with a grinder through a 2 - mm sieve to obtain dried raw soil.

[0030] 2. Mix the dried raw soil with the curing agent, add water for stirring after mixing evenly; after stirring evenly, add fiber and EPS particles in sequence and continue to stir to form a uniform flocculent fiber - EPS particle lightweight soil.

[0031] Embodiment 9: The difference between this embodiment and Embodiment 8 is that the mass of the curing agent is 9% of the raw soil in the foundation pit, the mass of the EPS particles is 0.2 - 0.8% of the raw soil in the foundation pit, and the mass of the fiber is 0.5 - 2% of the raw soil in the foundation pit; the optimum water content is 27% - 31%. Others are the same as those in Embodiment 8.

[0032] Embodiment 10: The difference between this embodiment and Embodiment 9 is as follows: the mass of the curing agent is 9% of the raw soil of the foundation pit, the mass of the EPS particles is 0.2% of the raw soil of the foundation pit, and the mass of the fibers is 1% of the raw soil of the foundation pit; the optimum water content is 29%. Others are the same as Embodiment 9.

[0033] In this embodiment, the polypropylene fibers have a relatively high tensile strength and play a role in reinforcing the fiber EPS particle lightweight soil, just like constructing a stable skeleton network in the soil mass. The EPS particles are light in texture and have a certain elasticity. When subjected to external forces, the EPS particles can transfer the stress they receive to the surrounding polypropylene fibers. The polypropylene fibers then evenly disperse the stress to a larger range of the soil mass, avoiding stress concentration and effectively enhancing the soil's ability to resist deformation, thus solving the problem of subgrade settlement caused by excessive filling load and insufficient foundation bearing capacity. The network structure formed by the interweaving of polypropylene fibers can wrap the EPS particles and soil particles, tightly binding them together to form a more stable and compact overall structure of the entire soil mass. When bearing loads, this structure can work together to jointly bear the external forces, greatly improving the overall strength and stability of the subgrade and reducing settlements or deformations caused by uneven local stress.

[0034] In this embodiment, the presence of polypropylene fibers makes the pore distribution in the soil mass more uniform, forming many small and interconnected pore channels. The EPS particles occupy a certain space in the soil mass, forming some larger pores. This multi-level pore structure is beneficial in two aspects. On the one hand, it is conducive to the migration and drainage of water in the soil mass, enabling the soil mass to minimize the content of free water before freezing. On the other hand, in a low-temperature environment, even if some water freezes into ice, these pores can provide a certain space for the expansion of ice, alleviating the damage pressure caused by the expansion of ice volume to the soil structure and reducing the possibility of subgrade frost heave. The good heat insulation performance of the EPS particles can slow down the rate of soil temperature change and reduce the degree of influence of the external low temperature on the soil mass. Although the polypropylene fibers themselves have limited heat insulation performance, they work together with the EPS particles to form a relatively stable temperature environment inside the soil mass. When the external temperature drops suddenly, the EPS particles reduce the heat loss of the soil mass, and the polypropylene fibers help to maintain the uniformity of the internal temperature of the soil mass, avoiding excessive freezing of water due to too low local temperature, thereby improving the frost resistance of the subgrade and reducing the occurrence of problems such as frost heave and mud pumping.

[0035] In this embodiment, polypropylene fibers can, to a certain extent, prevent the intrusion of moisture and play a certain waterproofing role. At the same time, the pore structure jointly optimized by EPS particles and polypropylene fibers is conducive to the drainage of moisture, enabling the soil mass to quickly drain excess moisture even in a saturated state, and avoiding the reduction of soil strength caused by long-term waterlogging. This synergistic effect of waterproofing and drainage improves the water stability of the fiber EPS particle lightweight soil, ensuring that the subgrade can still maintain good performance in a humid or freeze-thaw alternating environment. In the presence of moisture, the synergistic effect of polypropylene fibers and EPS particles can inhibit the disordered migration and aggregation of moisture in the soil mass. The network structure of polypropylene fibers can restrict the flow path of moisture, while EPS particles reduce the local accumulation of moisture through their own characteristics. This reduces the differences in soil strength and uneven deformation caused by uneven moisture distribution, further enhancing the stability of the subgrade and preventing various subgrade diseases caused by the action of water.

[0036] In summary, through various aspects of synergistic effects, polypropylene fibers and EPS particles in the fiber EPS particle lightweight soil solve many problems faced by subgrades in cold regions from multiple angles such as mechanical properties, frost resistance, and water stability, effectively improving the quality and service life of the subgrade.

[0037] The following examples are used to verify the beneficial effects of the present invention:

[0038] Example 1:

[0039] A preparation method for the backfill soil of a fiber EPS lightweight soil subgrade applicable to cold regions is completed according to the following steps:

[0040] 1. Dry 2000 g of foundation pit raw soil at 100 °C, and then grind it through a 2-mm sieve using a grinder to obtain dried raw soil;

[0041] 2. Mix the dried raw soil with 180 g of lime, add 580 g of water for stirring after mixing evenly; after stirring evenly, add 20 g of polypropylene fibers and 4 g of EPS particles in sequence, and continue to stir to form a uniform flocculent fiber EPS particle lightweight soil;

[0042] The foundation pit raw soil is selected from the construction site of the Lingui Expressway and is the soil excavated from the foundation pit; the particle diameter of the EPS particles is 2 - 3 mm, and the particle bulk density is 0.013 g / cm 3 .

[0043] The physical property indexes of the soil samples used are shown in Table 1.

[0044] Table 1 Physical property parameters of the soil mass

[0045]

[0046] The parameters of the fibers used are shown in Table 2.

[0047] Table 2 Physical Property Parameters of Polypropylene Fibers

[0048]

[0049] The preparation method of fiber EPS lightweight soil subgrade backfill suitable for cold regions is completed according to the following steps:

[0050] 1. Dry the raw soil in the foundation pit at 100 °C, and then grind it through a 2 mm sieve using a grinder to obtain dried raw soil.

[0051] 2. Mix the dried raw soil with a curing agent, and after mixing evenly, add water and stir; after stirring evenly, add fibers and EPS particles in sequence, and continue to stir to form a uniform flocculent fiber EPS particle lightweight soil.

[0052] Compaction test:

[0053] The preparation method of fiber EPS lightweight soil subgrade backfill suitable for cold regions is completed according to the following steps:

[0054] 1. Dry the raw soil in the foundation pit at 100 °C, and then grind it through a 2 mm sieve using a grinder to obtain dried raw soil.

[0055] 2. Mix the dried raw soil with a curing agent, and after mixing evenly, add water and stir; after stirring evenly, add fibers and EPS particles in sequence, and continue to stir to form a uniform flocculent fiber EPS particle lightweight soil.

[0056] The instrument used in this compaction test is a Marshall electric compactor, as Figure 1 shown; 5 different water contents need to be determined in advance for the compaction test. In this experiment, water contents of 27%, 28%, 29%, 30%, and 31% are used for the experiment. The raw soil in the foundation pit is 2000 g, the curing agent lime is 9%, the EPS particles are 0.2%, and the polypropylene fibers are 1%; the flocculent fiber EPS particle lightweight soil after mixing is filled into a sealed bag and soaked for standby, and the soaking time is 24 h.

[0057] After soaking, specimen preparation is carried out. The specimen preparation adopts the layered filling method, and it is filled in three layers. After each filling, it is leveled and slightly compacted, and then the compaction cylinder is installed on the compaction table for compaction. Each layer is compacted 27 times. After each compaction, check whether the height is appropriate. "Roughening" should be carried out between each layer before compaction. Repeat such operations until the compaction is completed, weigh it, and record it as m 1 , and finally, according to the specifications, the height of the specimen exceeding the top of the compaction cylinder shall not be greater than 6 mm, otherwise the specimen shall be invalidated.

[0058] After the specimen compaction is completed, use an electric hydraulic demolding machine to demold it. Then, take two representative samples inside the specimen for weighing and measure their water content. According to the specification requirements, the difference in water content between the two specimens shall not be greater than 1%. Weigh the mass of the compaction cylinder and record it as m 2 。

[0059] To obtain the relationship between the maximum dry density and the optimum water content of the specimen, the following calculations are introduced:

[0060] The wet density of the specimen after each compaction:

[0061]

[0062] where ρ 湿 is the wet density of the specimen (g / m 3 ), m 总 is the mass of the specimen and the compaction cylinder (g), m 筒 is the mass of the compaction cylinder (g), and v is the volume of the compaction cylinder (cm 3 ).

[0063] The dry density of the specimen after each compaction:

[0064]

[0065] where ρ 干 is the dry density of the specimen (g / m 3 ), and α is the water content of the specimen (%).

[0066] After calculating the dry density of each group, plot the water content-dry density curve with the dry density as the vertical axis and the water content as the horizontal axis. This curve should be a convex curve opening downward. The abscissa of the vertex of the curve is the optimum water content, and the ordinate is the maximum dry density.

[0067] The optimum water content of this compaction experiment is 29%, and the maximum dry density is 1.71 g / cm 3 。Draw the image as Figure 2 shown.

[0068] Unconfined compressive strength test:

[0069] The preparation method of the fiber EPS lightweight soil subgrade backfill soil applicable to cold regions is completed according to the following steps:

[0070] 1. Dry the raw soil in the foundation pit at 100 °C, and then use a grinder to grind it through a 2 mm sieve to obtain the dried raw soil;

[0071] 2. Mix the dried raw soil with the curing agent, and after mixing evenly, add water for stirring; after stirring evenly, add fibers and EPS particles in turn and continue stirring to form a uniform flocculent fiber EPS particle lightweight soil.

[0072] In the mixing ratio scheme of this experiment, the EPS particle contents are 0, 0.2%, 0.5%, and 0.8% in sequence; the polypropylene fiber contents are 0, 0.5%, 1%, and 2% in sequence, the lime is 9%, and the water is 29%; among them, the EPS particles, polypropylene fibers, water, and lime are all percentages of the raw soil.

[0073] The flocculent fiber EPS particle lightweight soil is filled into a cast iron mold with a diameter of 5 cm and a height of 5 cm in three times. After filling, use a jack to compact the mold. After standing for 4 hours, use an electric hydraulic demolding machine to demold. 9 specimens are made for each group. After the specimens are made, put them into transparent plastic bags for curing. Cure them to the ages of 7 d and 28 d respectively. The curing conditions are a relative humidity of 95% and a temperature of 20 ± 2 °C.

[0074] The instrument used in this experiment is a microcomputer-controlled electronic universal testing machine, model WDW-100E, as Figure 3 shown. During the test, the load loading rate is 1 mm / min, and the test time is controlled within 10 min; through the unconfined compressive strength test, it can be obtained that compared with traditional lime soil, the strength of fiber EPS lightweight soil is much higher than that of ordinary lime soil. When the curing time is 28 d, its maximum strength can reach 1.73 Mpa, which is greater than 1.6 Mpa of ordinary lime soil; at the time of failure, the specimens with added EPS particles and polypropylene fibers have obvious ductility and do not undergo brittle failure. The fibers play a very good bonding role in the specimens. While reducing the density, the strength and toughness are significantly improved. The schematic diagram of specimen failure is as Figure 4 shown; on the contrary, for ordinary lime soil, the specimens undergo significant failure when reaching the maximum compressive strength, and the failure occurs relatively violently. After the specimens fail, the residual stress also drops rapidly, and the specimens quickly lose their integrity.

[0075] Freeze-thaw cycle test:

[0076] The preparation work of the soil sample before the experiment refers to the compaction test. The EPS particles and polypropylene fibers are the same as those used in the unconfined compressive strength test. In the unconfined compressive strength test, when the EPS particle content is added to 0.8%, the strength of the specimens cured for 7 d or 28 d is lower than the specification requirements. Therefore, this dosage is not considered in the freeze-thaw cycle experiment; when the polypropylene fiber content is added to 2%, the strength of the specimens is roughly the same as that when the polypropylene fiber content is 1%, and the strength does not increase but instead decreases slightly, indicating that the fibers are not added infinitely. Therefore, this dosage of 2% polypropylene fiber is not considered in the freeze-thaw cycle experiment.

[0077] The mix proportions set for this freeze-thaw cycle are as follows: EPS particles are 0, 0.2%, 0.5%, polypropylene fibers are 0, 0.5%, 1%, lime is 9%, and water is 29%. The above dosages are all percentages of the raw soil. The production of specimens is the same as the above unconfined compression, and a cast iron mold of 50 cm × 50 cm is used. The curing time is 28 days. In the last day, it needs to be taken out in advance and soaked in water, and the water surface height should be greater than the specimen height by 2 cm. Considering that the winter temperature in the Northeast region is colder than that in other regions, the freeze-thaw temperature difference should be widened as much as possible. Therefore, when freezing, the specimens are placed in a freezer at -25°C for 12 hours. When thawing, the specimens are placed in a constant temperature oven at 20°C for 12 hours. This is one freeze-thaw cycle process; repeat the above operations, and conduct unconfined compression tests after 1, 2, 3, 4, and 5 cycles respectively, as Figure 5 shown.

[0078] It can be seen from the comparison of several freeze-thaw cycles that the specimens with added EPS particles have much stronger frost heave resistance than those without added EPS particles. This is because with the addition of EPS particles and lime, the same volume of soil is replaced. The EPS particles form certain pores in the soil mass, and under the solidification effect of lime, the frost heave of the soil is jointly restricted. In addition, the polypropylene fibers form a network connection in the gap between the EPS particles and the soil, improving the anti-deformation ability of the specimens; when the first freeze-thaw cycle ends, the frost heave rate of the specimens without EPS particles is greater than that of the specimens with added EPS particles. As the number of freeze-thaw cycles increases, when the third freeze-thaw cycle ends, the frost heave rate of the specimens reaches the peak. Subsequently, when the freeze-thaw cycle reaches the fifth time, the frost heave rate of the specimens with added EPS particles decreases by 40%. On the contrary, the frost heave rate of traditional lime soil is still very high. From the aspect of strength analysis, for the specimens without added EPS particles and polypropylene fibers, after 5 freeze-thaw cycles, the compressive strength drops from the initial 1.6 Mpa to 0.55 Mpa, and the strength loss is serious, and the average mass loss of the specimens reaches 2.1%; for the specimens with added EPS particles and polypropylene fibers, under the same conditions, the compressive strength drops from 1.73 Mpa to 1.02 Mpa, and the strength drops more gently than that of the plain soil. The average mass loss of the specimens is only 1.58%, and the specimens can still maintain their due toughness and integrity after failure, and the residual stress fluctuation also tends to be stable.

[0079] The construction process flow of fiber EPS lightweight soil subgrade backfill soil applicable to cold regions is as follows:

[0080] I. Measurement and lofting: Before the foundation construction, the reference points should be determined according to the road design as the lofting standard for the surveyors.

[0081] II. Subgrade Treatment: Before the rolling construction of fiber EPS lightweight soil, the rolling construction area should be inspected and cleaned to remove loose soil, dead branches and fallen leaves on the surface. According to the subgrade elevation set by the surveyors, the subgrade should be leveled. The purpose is to prevent the generation of weak areas in the original subgrade and fiber EPS granular lightweight soil, which may affect the subgrade strength.

[0082] III. Soil Sample Preparation: Load the raw soil and lime into the mixer according to the calculated filling quality, then load the proposed water content into the mixer for mixing. Finally, after the lime soil is evenly mixed, add EPS particles and polypropylene fibers for stirring.

[0083] IV. Soil Sample Transportation: During the transportation of soil samples, strict attention should be paid to controlling the speed of transport vehicles to avoid the blowing and dropping of EPS foam particles. If there are many bumps on the transport section, it is necessary to cover with cloth when necessary. When the mixing site is far from the paving site, moisture preservation work should be done during transportation and the soil should be paved in time after arriving at the site.

[0084] V. Paving and Leveling: First, calculate the filling quantity according to the design section, filling length and laying thickness; use a grader or rammer to evenly spread and level the lightweight subgrade material; after paving and leveling are completed, the laying thickness should be checked in time, and any places that need to be filled or reduced should be rectified in time.

[0085] VI. Rolling: During the rolling construction, considering that EPS particles will undergo plastic deformation under excessive pressure, resulting in an increase in density and self-weight, therefore, a light roller should be used for static pressing first, then a medium roller for rolling, and finally a light roller for finishing. Excessive rolling will damage the road surface, so each place should be compacted 2 - 3 times; the rolling sequence should follow the rule of rolling from the slope protection to the road center in a straight section and from the inner side of the curve to the outer side in a curve section; during rolling, the layer-by-layer rolling method should be adopted between layers, and each layer should be roughened to prevent the generation of weak areas in the middle, which may affect the bearing capacity.

[0086] VII. Maintenance: According to the indoor test, the maintenance effect is the best when the maintenance time is 28 days. After rolling is completed, geotextiles or straw curtains should be covered in time, and water should be sprinkled regularly to keep it moist.

Claims

1. A fiber EPS lightweight soil roadbed backfill suitable for cold regions, characterized in that The fiber EPS lightweight soil roadbed backfill soil suitable for cold areas is composed of foundation pit raw soil, curing agent, EPS particles and fibers; the mass of the curing agent is 9% of the foundation pit raw soil, the mass of the EPS particles is 0.2-0.8% of the foundation pit raw soil, and the mass of the fiber is 0.5-2% of the foundation pit raw soil.

2. The fiber EPS lightweight soil roadbed backfill soil suitable for cold regions according to claim 1 is characterized in that The mass of the curing agent is 9% of the raw soil of the foundation pit, the mass of the EPS particles is 0.2% of the raw soil of the foundation pit, and the mass of the fiber is 1% of the raw soil of the foundation pit.

3. The fiber EPS lightweight soil roadbed backfill soil suitable for cold regions according to claim 1 is characterized in that The physical property parameters of the raw soil for the foundation pit are as follows: water content is 17.5%, liquid limit is 42.4%, plastic limit is 29.35%, and plasticity index is 13.1%.

4. The fiber EPS lightweight soil roadbed backfill soil suitable for cold regions according to claim 1, characterized in that The curing agent is lime.

5. The fiber EPS lightweight soil roadbed backfill soil suitable for cold regions according to claim 1 is characterized in that The particle diameter of the EPS particles is 2-3 mm, and the particle bulk density is 0.013 g / cm 3 .

6. The fiber EPS lightweight soil roadbed backfill soil suitable for cold regions according to claim 1, characterized in that The fibers are polypropylene fibers.

7. The fiber EPS lightweight soil roadbed backfill soil suitable for cold regions according to claim 6, characterized in that The physical performance parameters of the polypropylene fiber are: fiber length 6 mm, fiber diameter 32.7 μm, density 0.91 g / cm 3 , tensile strength is 469Mpa, ultimate elongation is 28.4%, and elastic modulus is 28.4Mpa.

8. The method for preparing fiber EPS lightweight soil roadbed backfill soil suitable for cold regions as claimed in claim 1, characterized in that The preparation method of fiber EPS lightweight soil roadbed backfill soil suitable for cold areas is completed in the following steps:

1. Dry the raw soil of the foundation pit at 100°C, and then grind it through a 2mm sieve using a grinder to obtain dried raw soil; 2. Mix the dried raw soil and curing agent, add water and stir evenly; add fiber and EPS particles in sequence after stirring evenly, and continue stirring to form a uniform flocculent fiber EPS particle lightweight soil.

9. The method for preparing fiber EPS lightweight soil roadbed backfill soil suitable for cold regions according to claim 8, characterized in that The mass of the curing agent is 9% of the raw soil of the foundation pit, the mass of the EPS particles is 0.2-0.8% of the raw soil of the foundation pit, and the mass of the fiber is 0.5-2% of the raw soil of the foundation pit; the optimum water content is 27%-31%.

10. The method for preparing fiber EPS lightweight soil roadbed backfill soil suitable for cold regions according to claim 9, characterized in that The mass of the curing agent is 9% of the raw soil of the foundation pit, the mass of the EPS particles is 0.2% of the raw soil of the foundation pit, and the mass of the fiber is 1% of the raw soil of the foundation pit; the optimal moisture content is 29%.

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