CN113277813A

CN113277813A - Composite curing agent for high liquid limit soil and use method and application thereof

Info

Publication number: CN113277813A
Application number: CN202110446916.XA
Authority: CN
Inventors: 戴范; 徐海宁; 谢振翔; 黄希望; 陈家闯; 娄平; 王强
Original assignee: Cscec Zhanjiang Avenue Investment Construction Co ltd; Central South University
Current assignee: Cscec Zhanjiang Avenue Investment Construction Co ltd; Central South University
Priority date: 2021-04-25
Filing date: 2021-04-25
Publication date: 2021-08-20

Abstract

The invention provides a composite curing agent for high liquid limit soil, a using method and application thereof, wherein the composite curing agent for high liquid limit soil comprises the following raw materials in percentage by weight: 35-45% of Portland cement, 35-43% of slag powder, 8-11% of quicklime and 9-13% of lignin. By adopting the composite curing agent for the high liquid limit soil, the CBR value of the improved high liquid limit soil is obviously improved, the requirement of roadbed filling can be met, and the problem that the high liquid limit soil cannot be used for roadbed filling is solved. The curing agent reduces the cement consumption by adding the slag powder, the quicklime and the lignin, changes industrial byproducts slag and lignin into valuables, avoids resource waste, reduces the construction cost and conforms to the sustainable development concept.

Description

Composite curing agent for high liquid limit soil and use method and application thereof

Technical Field

The invention belongs to the technical field of high liquid limit soil, and particularly relates to a composite curing agent for high liquid limit soil, and a use method and application thereof.

Background

The high liquid limit soil has high liquid-plastic limit, high water content, large pore ratio, low strength and low compressibility. The technical specification of highway subgrade construction (JTGF10-2006) stipulates that high liquid limit soil with a liquid limit of more than 50% and a plasticity index of more than 26 cannot be directly used as subgrade filler, and certain measures should be taken to improve the high liquid limit soil, so that the high liquid limit soil can be used after being checked to be qualified; the minimum strength of the first-class highway subgrade filler (CBR) requirement is specified to be 8% in terms of strength.

The overall topography of the Zhanjiang river in Guangdong is flat, and the landform units comprise a sea area plain, a flood area depression, a flood area plain and a micro-hilly terrace land. In Zhanjiang areas, rainwater is abundant, the rain season is long, for a long time, most of embankment fillers or cutting soil have high liquid limit index, too large plasticity index and too high clay particle component content, and the influence on the strength and stability of highway subgrade and the durability of pavement is large.

At present, aiming at high liquid limit soil, construction units generally adopt ways of abandoning, replacing, filling or improving and the like to process so as to meet the standard requirements. The high liquid limit soil content in the Guangdong area is large, the construction cost is increased by adopting a method of abandoning and changing the filling, the difficulty of arranging the construction site is increased, and the earthwork transportation has adverse effect on the environment.

Tests show that the optimal sand-mixing proportion of high-liquid-limit soil with different performances is obtained by Chengduo et al, the optimal sand-mixing gravel ratio of high-liquid-limit soil with different properties is researched by Lifanghua, the research of lime-improved high-liquid-limit soil test is carried out by Zhao Kogyang, roadbed filling improvement measures are provided, the research on the influence of sand-mixing on the engineering properties of roadbed clay in lake regions is carried out by Longtao, the obtained fine sand has obvious effect on improving the bearing ratio, the research on the improved filling construction process of high-liquid-limit soil by Zhumei and the like is carried out by Longtao, the improvement effect and mechanism of various schemes are analyzed, the road-using characteristics of lime-improved high-liquid-limit soil are researched by Yang Hei and the like, and the road-using performance of high-liquid-limit soil and red clay is researched by Mianxi and the like.

The measures for improving the high liquid limit soil subgrade are generally to select single-doped cement, sand or lime. Because the condition is limited and the environmental protection is considered, a single material is difficult to obtain in a large amount, the price change range is large, and the engineering cost is not easy to control, therefore, the invention provides a novel composite curing agent for high liquid limit soil.

Disclosure of Invention

The invention aims to solve the technical problems that the defects and shortcomings in the background technology are overcome, the composite curing agent for the high liquid limit soil and the using method and application thereof are provided, the composite curing agent is excellent in performance, economical and reasonable, the CBR value of the improved high liquid limit soil is obviously improved, the requirement of roadbed filling can be met, and the problem that the high liquid limit soil cannot be used for roadbed filling is solved.

In order to solve the technical problems, the technical scheme provided by the invention is as follows:

the composite curing agent for the high liquid limit soil comprises the following raw materials in percentage by weight: 35-45% of Portland cement, 35-43% of slag powder, 8-11% of quicklime and 9-13% of lignin.

In the curing agent, cement is a hydraulic inorganic gel material and is usually used for treating soft soil roadbed, the curing mechanism is that the cement and water generate hydration reaction to generate gel hydrates such as hydrated calcium silicate and hydrated calcium aluminate, and the hydrates react with active ingredients in soil to generate flaky, fibrous or needle crystals, so that the connection among soil particles is increased, a stable network structure is formed in the soil, and the strength of the soil is improved.

The slag powder is a powder material obtained by drying and grinding granulated blast furnace waste slag generated in the smelting process of a steel plant, is an industrial waste with potential activity, is cheap and easy to obtain, is doped with slag when cement is used for improving high liquid limit soil, can save the using amount of cement and reduce the cost; the slag can fill gaps among the soil particles, the soil body is more compact after rolling, and the early strength is improved. Meanwhile, the soil absorbs water to separate out a large amount of ions which react with minerals in the soil to generate gel, so that the cohesive force of the soil is enhanced, the calcium ions can also react with carbon dioxide in the air to generate calcium carbonate, the soil strength is further improved, the later strength is obviously improved by adding slag powder, and the soil body has good seawater erosion resistance and corrosion resistance and better working performance.

In addition, the slag is used for improving high liquid limit soil, can realize the reutilization of waste materials and is beneficial to environmental protection; the slag is cheaper than cement, so that a large amount of cement can be saved in the improvement, and the strength of the improved slag can meet the requirement.

The quicklime in the curing agent is a product formed by calcining calcium carbonate at high temperature, is low in price and easy to obtain, calcium ions and hydroxyl ions are dissociated under the action of water, and the soil is exchanged with the ions to agglomerate fine granular soil, so that the integrity of the soil body is increased; clay minerals and SiO in soil₂And Al₂O₃The lime-silica gel is chemically reacted with lime to generate lime silicate hydrate and lime aluminate hydrate, so that soil particles are cemented; CO in soil and air₂The calcium carbonate reacts with lime directly in a humid environment to generate hard calcium carbonate, and the strength of the soil body is increased.

The lignin is a three-dimensional polymer compound which is formed by connecting phenylpropane structural units through carbon-carbon bonds and ether bonds and contains various active functional groups. The lignin has the following effects on the improvement of high liquid limit soil: hydrolyzing lignin in soil pore water to obtain low-valence cations Na of lignin⁺With higher valence cations Ga in the counter-ion layer²⁺Ion exchange occurs; ② secondary hydroxyl in lignin is broken and H in water⁺Sharing a pair of electrons, carrying out protonation reaction, and releasing water molecules from the protonated lignin to form a lignin polymer with positive electricity; thirdly, under the action of static electricity, the lignin polymer with positive electricity is adsorbed on the surface of the soil bodyAnd negative charges in the soil body, so that the distance between soil particles is reduced; the lignin polymer has gel property and can fill gaps among soil particles, so that external moisture cannot permeate into the soil, the water stability of the soil is improved, and meanwhile, adjacent soil particles are tightly connected together, so that the bending tensile strength of a soil stabilization layer is improved; fifthly, after compaction by a large machine, the soil body is more compact, and the strength is greatly improved.

According to the curing agent, lignin serving as a high-molecular organic substance is hydrolyzed in water to form cations and form a lignin polymer with positive charges, negative charges in a soil body are neutralized, the space between soil particles is reduced, and the lignin polymer has a gel property, so that external water cannot permeate into the soil body, and the water stability of the soil body is improved; the cement, the slag powder and the quicklime are used as inorganic compounds to carry out chemical reaction under the action of water to generate gelatinous hydrate to solidify soil, so that the soil strength is further improved. The organic compound and the inorganic compound are compounded for use, so that the defect of a single curing agent is overcome, and the engineering property of the high liquid limit soil is greatly improved.

Preferably, the curing agent is composed of the following raw materials in percentage by weight: 40% of Portland cement, 40% of slag powder, 10% of quicklime and 10% of lignin. The raw materials in the formula are reasonably matched, and the formula has an excellent improvement effect on high liquid limit soil.

Preferably, the portland cement is p.c32.5 composite portland cement; the P.C32.5 composite portland cement is adopted, and the fly ash and the coal gangue are adopted as a mixture, so that the cement has the characteristics of stable early and later strength, low hydration heat, strong corrosion resistance, economic price and the like;

the slag powder is S95 slag powder, and the surface area of the slag powder is not less than 400m²Perkg, 28-day activity index is not less than 95 percent;

the mass content of calcium oxide in the quicklime is more than or equal to 90 percent, and the fineness is more than or equal to 200 meshes; the quick lime is a product generated by calcining and decomposing calcium carbonate natural rock at high temperature;

the purity of the lignin is more than or equal to 70 percent; the lignin is a byproduct from a paper mill, is powdery solid and has certain fragrance, and the main components of the lignin are lignin and derivatives thereof and a small amount of inorganic salts.

As a general inventive concept, the invention also provides a use method of the composite curing agent for the high liquid limit soil, which comprises the following steps:

1) determining the mixing amount of the curing agent in the high liquid limit soil;

2) the curing agent and the high liquid limit soil are uniformly mixed.

Preferably, the high liquid limit soil is high liquid limit soil with liquid limit of 50-100%. The method is not economically applicable to high liquid limit soil with the liquid limit exceeding 100 percent.

Preferably, in the step 1), when the liquid limit of the high liquid limit soil is 50-70%, the doping amount of the curing agent is 3-5% of the mass of the high liquid limit soil; when the liquid limit of the high liquid limit soil is 70-100%, the doping amount of the curing agent is 5-7% of the mass of the high liquid limit soil. After the high liquid limit soil is improved, the liquid limit and plasticity index are reduced, the strength is greatly improved, and the filling requirement in the specification is met.

Preferably, the use method further comprises the following steps: and uniformly mixing the curing agent and the high liquid limit soil to obtain a material, wherein the compacted water content of the material is controlled within a reasonable range, and the difference between the compacted water content and the optimal water content is not more than 5%.

As a general inventive concept, the invention also provides an application, in particular to the application of the composite curing agent for the high liquid limit soil and the application method in the field of roadbed filling.

Preferably, the method comprises the following steps of:

1) preparing soil application: taking high liquid limit soil as roadbed filling, and determining that the loose paving thickness is controlled within 30 cm;

2) spreading and leveling: dividing a paving grid, unloading high liquid limit soil filler into the grid, and leveling by a bulldozer and finely leveling by a leveler after the rolling requirement is met so as to ensure that the filler is paved to be leveled and uniform; if the water content of the high liquid limit soil does not meet the requirement, fully airing the high liquid limit soil until the water content is reduced to be within a target range, and constructing the high liquid limit soil;

3) mixing a curing agent: drawing a curing agent-doped grid net on the surface of the filler by using lime, unloading the curing agent into the curing agent-doped grid net, and controlling the spreading uniformity of the curing agent by adopting a grid method so as to ensure that the curing agent and soil can be uniformly mixed;

4) blending and leveling: fully mixing by using a stirrer to keep the color of the obtained mixed soil consistent; after the mixed soil meets the rolling requirement, leveling construction is carried out, and the loose paving thickness of the mixed soil is controlled in the process;

5) and (3) rolling compaction: during rolling construction, static pressure is adopted firstly, vibration compaction is adopted, and the static pressure is adopted for the last time, so that the rolling times of all parts are the same.

Preferably, in the step (4), the fully mixing comprises the following steps: firstly, turning and stirring the paved curing agent and the filler twice by adopting a stirring machine mode so as to prevent the curing agent from falling to the bottom and not turning and stirring to the bottom; then, turning and stirring twice, turning and stirring to the end, and enabling the turning and stirring depth to enter the lower layer soil (soil below the loose paving thickness) by 0.5-1.0 cm, so that the curing agent is uniformly distributed in the filler; in the mixing construction process, checking the stirring depth to ensure that the filling layer is uniformly mixed;

in the step (5), the rolling speed of static pressure is 2-5 Km/h, the rolling speed of vibration compaction is 3-6 Km/h, and rolling is carried out until the top surface of the filling layer is stable, does not sink, and has a flat surface without wheel tracks.

Compared with the prior art, the invention has the beneficial effects that:

1. by adopting the composite curing agent for high liquid limit soil, the CBR value of the high liquid limit soil is obviously improved, the strength of a constructed roadbed meets the specified standard, the high liquid limit soil along the line can be fully utilized, and the influence of a large amount of abandoned parties on the ecological environment is avoided.

2. In the curing agent, the consumption of cement is reduced by adding the slag powder, the quicklime and the lignin, so that industrial byproducts of slag and lignin are changed into valuable, the waste of resources is avoided, the construction cost is reduced, and the curing agent conforms to the sustainable development concept.

3. According to the invention, inorganic condensate (cement and lime), slag and high molecular compound lignin are mixed for use, so that adverse effects on the growth of surrounding soil bodies and plants caused by an alkaline environment formed by excessive cement consumption are avoided, the blank of improving the high liquid limit soft soil roadbed is filled, the mechanical property, the water stability and the corrosion resistance of the high liquid limit soft soil are greatly improved, and the high liquid limit treatment method has practical value on the high liquid limit treatment in coastal areas.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a graph showing the change in CBR value after improvement of high liquid limit soil in example 3 using the curing agent of example 1;

FIG. 2 is a graph showing the change in CBR value after the curing agent of example 2 is used to improve high liquid limit soil in example 3;

FIG. 3 is a flow chart of the construction process in example 4.

Detailed Description

In order to facilitate understanding of the invention, the invention will be described more fully and in detail with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.

Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

Comparative example 1:

the composite curing agent for the high liquid limit soil is prepared by mixing the following raw materials in percentage by weight: 50% of P.C32.5 composite portland cement, 40% of S95 slag powder and 10% of quick lime.

The calcium oxide in the quicklime accounts for 90% by mass, and the fineness is more than or equal to 200 meshes.

Comparative example 2:

the composite curing agent for the high liquid limit soil is prepared by mixing the following raw materials in percentage by weight: 80% of P.C32.5 composite portland cement, 10% of quicklime and 10% of lignin.

The calcium oxide in the quicklime accounts for 90% by mass, the fineness of the calcium oxide is more than or equal to 200 meshes, and the purity of the lignin is 70%.

Example 1:

the composite curing agent for the high liquid limit soil is prepared by mixing the following raw materials in percentage by weight: 40% of P.C32.5 composite portland cement, 40% of S95 slag powder, 10% of quicklime and 10% of lignin.

The calcium oxide content in the quicklime is 90%, the fineness is more than or equal to 200 meshes, and the purity of the lignin is 70%.

Example 2:

the composite curing agent for the high liquid limit soil is prepared by mixing the following raw materials in percentage by weight: 42% of P.C32.5 composite portland cement, 38% of S95 slag powder, 9% of quicklime and 11% of lignin.

Example 3:

the following examples of soils were selected from high liquid limit soils in 2 different regions of the main road of the Zhanjiang river, and in order to reduce the test error, the soils in the same region were divided into 3 groups, and the physical properties of each group of soils were obtained by conducting the test according to the specification "road geotechnical test code" (JTGE40-2007), and the average value of 3 groups was taken as the final result of the region, as shown in Table 1:

TABLE 1 physical Properties of high liquid Limited soils

As can be seen from Table 1, the liquid limits of the soil in the area 1 and the area 2 are 71.3 percent and 59.3 percent respectively, and exceed the specification limit value by 50 percent; plasticity index is 35.4, 27.8 respectively, exceeding specification limit 26; the bearing ratio CBR is 5.41 percent and 7.36 percent respectively, the minimum bearing ratio CBR value of the roadbed filling in the technical specification of highway roadbed construction is 8 percent, and the strength of the soil does not meet the requirement. Therefore, the high liquid limit soil cannot be directly used for roadbed filling, and needs to be improved.

At present, the design control index of the highway engineering subgrade is mainly the CBR value, and the aim of the embodiment is to mix curing agents with different proportions under the optimal water content and the compaction degree of 98 percent and respectively measure the CBR value.

The curing agents of examples 1 and 2 were added to the high liquid limit soils of zone 1 and zone 2 in an amount of 3%, 5% and 7% by mass, respectively, and 3 soil samples were prepared and tested in each ratio, and the CBR values of the improved soils are shown in tables 2 and 3.

TABLE 2 CBR values after improvement of high liquid limit soils with curing agent of example 1

TABLE 3 CBR value of high liquid limit soil after curing agent modification of example 2

After the high liquid limit soil is improved by being mixed with the curing agent, the change rule of the CBR average value of the soil sample along with the curing agent proportion of the example 1 and the example 2 is shown in figures 1 and 2.

As can be seen from fig. 1 and 2, the CBR value increases with the amount of the curing agent. After the curing agent of the example 1 is modified by adding 3%, 5% and 7% of the curing agent in the high liquid limit soil, the CBR average values of the area 1 are respectively 13.07%, 19.40% and 32.47%, and are respectively improved by 141.59%, 258.60% and 500.18% compared with the unmodified high liquid limit soil; the CBR average values of the area 2 are respectively 18.34%, 29.65% and 45.16%, which are respectively improved by 149.18%, 302.85% and 513.59% compared with the unmodified high liquid limit soil. After the curing agent of the example 2 is modified by adding 3%, 5% and 7% of the curing agent in the high liquid limit soil, the CBR average values of the area 1 are respectively 12.91%, 19.32% and 31.97%, and are respectively improved by 138.63%, 257.12% and 490.94% compared with the unmodified high liquid limit soil; the CBR average values of the area 2 are respectively 18.14%, 28.76% and 43.26%, which are respectively improved by 146.47%, 290.76% and 487.77% compared with the unmodified high liquid limit soil.

Therefore, the improvement effect of the high liquid limit soil is obvious, the strength is greatly improved, and the requirement that the minimum value of the California Bearing Ratio (CBR) of the first-level highway subgrade is 8 percent can be met after improvement.

② taking the high liquid limit soil in the area 1, respectively adding 3 percent, 5 percent and 7 percent of the curing agent in the comparative example 1 and the curing agent in the comparative example 2, preparing 3 soil samples in each proportion for testing, and the CBR value of the improved soil is shown in Table 4.

TABLE 4 CBR values of improved high liquid limit soils

As can be seen from Table 4, when the ingredients of the curing agent lack slag powder or lignin, the effect of improving the high liquid limit soil is inferior to that of the curing agent in example 1, and it can be seen that the raw materials of the curing agent used in the present invention have a synergistic effect.

Example 4:

a construction process for applying high liquid limit soil to roadbed filling is shown in a process flow diagram in figure 3, and specifically comprises the following steps:

(1) preparing soil application: taking high liquid limit soil as roadbed filling; in the process of improving the high liquid limit soil, in order to ensure that the curing agent can be fully and uniformly stirred with the soil, the loose paving thickness is controlled within 30 cm.

(2) Spreading and leveling: the method comprises the steps that high liquid limit soil filler is loaded onto a dump truck by an excavator and then is transported to a construction road section, in order to ensure the consistency of the soil filling thickness, a paved grid is divided in advance, a specially-assigned person is dispatched to direct the dump truck to a specified grid for unloading, and the high liquid limit soil filler is unloaded into the grid. And after the filler meets the rolling requirement, leveling by a bulldozer and finely leveling by a grader so that the filler is paved to keep level and uniform.

(3) Mixing a curing agent: drawing a curing agent-doped grid on the surface of the filler by using lime according to the proportion of the curing agent and the carrying capacity of the vehicle, unloading the curing agent into the curing agent-doped grid, and controlling the spreading uniformity of the curing agent by adopting a grid method.

(4) Blending and leveling: fully mixing by using a stirrer, firstly turning and stirring the paved curing agent and the filler twice to prevent the curing agent from falling to the bottom and not turning and stirring to the bottom; and then turning and stirring twice, turning and stirring to the end, enabling the turning and stirring depth to enter the lower layer soil (soil below the loose paving thickness) by 0.5-1.0 cm, enabling the curing agent to be uniformly distributed in the filler, fully bonding the upper layer soil and the lower layer soil, and checking the turning and stirring depth in the mixing construction process to ensure that the filling layer is uniformly mixed. After mixing, the color of the obtained mixed soil is kept consistent. And after the mixed soil meets the rolling requirement, leveling construction is carried out, and the loose paving thickness of the mixed material is controlled in the process.

(5) And (3) rolling compaction: the vibration road roller with more than 18 tons is adopted, and a rolling mode combining static pressure and vibration pressure is adopted. During rolling construction: firstly, adopting static pressure, then adopting vibration compaction, and finally adopting static pressure to make the rolling times of all the parts be identical. And (3) rolling construction principle: slow first and fast second, from weak vibration to strong vibration, from inside to outside (bend), from side to middle (straight line), longitudinal advance and retreat. When rolling, the overlapping of the wheel tracks of two adjacent times can reach 15-20 cm, and uniform compaction can be guaranteed. The rolling speed of static pressure is 2-5 Km/h, and the rolling speed of vibration compaction is 3-6 Km/h. And (5) rolling until the top surface of the filling layer is stable, does not sink, and has a flat surface without wheel tracks, and recording corresponding rolling modes and times.

(6) And (3) quality detection: the quality control of the high liquid limit soil mixed with the curing agent for improving the filling comprises three aspects, namely: quality control of the filler, quality control of construction and detection of construction quality. The quality control detection of the improved high liquid limit filling mainly comprises the detection of the compaction degree, the compaction water content and the strength.

Since a large range of high liquid limit soil exists on the primary road of Zhanjiang Daojie, for example, the high liquid limit soil in the following area 1 and area 2, the construction process of this embodiment is applied to the primary road engineering of Zhanjiang Daojie, wherein the curing agent in step (3) is the composite curing agent for high liquid limit soil in example 1, and the mixing amount of the curing agent in the high liquid limit soil filler is 3% to 7%.

The curing agents of example 1 were added to the high liquid limit soils in amounts of 3%, 5% and 7% by mass, respectively, and the physical properties of the modified soils are shown in Table 5.

TABLE 5 physical Properties of the improved high liquid Limited soil

As can be seen from Table 5, as the amount of the curing agent is increased, the liquid limit is decreased and the plastic limit is increased, the plastic limit index is decreased to be within the standard limit value, the 28-day unconfined compressive strength is gradually increased, and the improved soil body has good engineering properties.

By adopting the construction process in the embodiment, the high liquid limit soil along the engineering line is fully utilized, a large amount of abandoned sides are avoided, the ecological environment is protected, and the construction cost is reduced. The scheme of the invention also has important theoretical value and practical significance for the application of domestic high liquid limit soil.

Claims

1. The composite curing agent for the high liquid limit soil is characterized by comprising the following raw materials in percentage by weight: 35-45% of Portland cement, 35-43% of slag powder, 8-11% of quicklime and 9-13% of lignin.

2. The composite curing agent for the high liquid limit soil according to claim 1, wherein the curing agent is prepared from the following raw materials in percentage by weight: 40% of Portland cement, 40% of slag powder, 10% of quicklime and 10% of lignin.

3. The composite curing agent for high liquid limit soil according to claim 1 or 2, wherein the portland cement is p.c32.5 composite portland cement;

the slag powder is S95 slag powder;

the mass content of calcium oxide in the quicklime is more than or equal to 90 percent, and the fineness is more than or equal to 200 meshes;

the purity of the lignin is more than or equal to 70 percent.

4. The use method of the composite curing agent for the high liquid limit soil as defined in any one of claims 1 to 3, characterized by comprising the following steps:

2) the curing agent and the high liquid limit soil are uniformly mixed.

5. The use method according to claim 4, wherein the high liquid limit soil is a high liquid limit soil with a liquid limit of 50-100%.

6. The use method of claim 5, wherein in the step 1), when the liquid limit of the high liquid limit soil is 50-70%, the mixing amount of the curing agent is 3-5% of the mass of the high liquid limit soil; when the liquid limit of the high liquid limit soil is 70-100%, the doping amount of the curing agent is 5-7% of the mass of the high liquid limit soil.

7. Use according to any one of claims 4 to 6, further comprising the steps of: and uniformly mixing the curing agent and the high liquid limit soil to obtain a material, wherein the compacted water content of the material is controlled within a reasonable range, and the difference between the compacted water content and the optimal water content is not more than 5%.

8. The application of the composite curing agent for high liquid limit soil as defined in any one of claims 1 to 3 or the use method of any one of claims 4 to 7 in the field of roadbed filling.

9. Use according to claim 8, characterized in that it comprises the following steps:

2) spreading and leveling: dividing a paving grid, unloading high liquid limit soil filler into the grid, and leveling by a bulldozer and finely leveling by a leveler after the rolling requirement is met so as to ensure that the filler is paved to be leveled and uniform;

3) mixing a curing agent: drawing a curing agent-doped grid net on the surface of the filler by using lime, and unloading the curing agent into the curing agent-doped grid net;

10. Use according to claim 9, wherein in step (4) said thorough mixing comprises the steps of: firstly, turning and stirring the paved curing agent and the filler twice by adopting a stirring machine mode so as to prevent the curing agent from falling to the bottom and not turning and stirring to the bottom; then, turning and stirring twice, turning and stirring to the end, and enabling the turning and stirring depth to enter the lower-layer soil to be 0.5-1.0 cm, so that the curing agent is uniformly distributed in the filler; in the mixing construction process, checking the stirring depth to ensure that the filling layer is uniformly mixed;

and (5) adopting a vibrating road roller with the rolling speed of more than 18 tons, wherein the static pressure rolling speed is 2-5 Km/h, the vibration compaction rolling speed is 3-6 Km/h, and the rolling is carried out until the top surface of the filling layer is stable, does not sink, and has a flat surface without wheel tracks.