Titanium gypsum modified subgrade soil as well as preparation method and application thereof

Abstract

The invention provides titanium gypsum modified subgrade soil as well as a preparation method and application thereof. The invention relates to titanium gypsum modified subgrade soil, which is prepared from the following raw materials in percentage by mass: 5 to 10 percent of titanium gypsum, 60 to 75 percent of natural subgrade soil, 5 to 15 percent of modifier and 8 to 20 percent of water. The industrial solid waste titanium gypsum is utilized, and the purchase cost is far lower than that of a natural base material; the modifier adopts an industrial by-product to replace part of cement / lime, so that the engineering investment is remarkably saved. According to the titanium gypsum modified roadbed soil, effective utilization of titanium gypsum industrial solid waste is achieved, high-valued and large-scale resource utilization of titanium gypsum is achieved, meanwhile, use of natural roadbed soil is reduced due to use of titanium gypsum, the road engineering construction cost is reduced, and the roadbed engineering performance is improved.

Description

Technical Field

[0001] This disclosure relates to the field of roadbed material technology, and in particular to a titanium gypsum modified roadbed soil, its preparation method and application. Background Technology

[0002] Titanium gypsum is an industrial solid waste generated during the sulfuric acid process in titanium dioxide production. Its main component is calcium sulfate dihydrate (CaSO4·2H2O), and it also contains small amounts of Fe2O3, Al2O3, SiO2, and unreacted calcium carbonate, ferrous sulfate, and other impurities. Currently, the main method of disposal for titanium gypsum is stockpiling, which not only occupies a large amount of land resources but also poses environmental risks such as dust and leachate pollution of soil and groundwater. The resource utilization rate is less than 10%, which has become a key bottleneck restricting the green development of the titanium dioxide industry.

[0003] The roadbed is the core load-bearing structure of road engineering, and it has strict requirements on the physical and mechanical properties of the fill material (such as compaction degree, CBR value, compressive strength, and water stability). Traditional roadbed fill materials mostly use natural sand and gravel, clay, etc. Over-exploitation of natural aggregates not only damages the ecological environment, but also faces the problems of resource depletion and increased transportation costs. In some areas, the natural roadbed soil has poor properties (such as high liquid limit clay with high water content and low strength, and sand with poor cohesion and easy permeability), which requires the addition of cementitious materials such as cement and lime for modification, increasing engineering costs, and the production process of cementitious materials has high carbon emissions.

[0004] Therefore, applying titanium gypsum resources to roadbed engineering is undoubtedly a green development path that can reduce titanium gypsum stockpiling, protect the environment, and reduce costs. However, research on its application in roadbed soil is limited and has significant shortcomings: 1. When unmodified titanium gypsum is used directly as roadbed filler, it suffers from problems such as difficulty in compaction, slow strength growth, and poor water stability, failing to meet the technical indicators of roadbed engineering; 2. Existing modification technologies mostly involve the simple addition of cement, resulting in high modification costs, and the modification formula is not optimized for the compositional characteristics of titanium gypsum, failing to fully utilize its cementing potential; 3. There is a lack of systematic titanium gypsum roadbed soil preparation processes and construction technical specifications, making it difficult to achieve engineering applications. Summary of the Invention

[0005] This disclosure provides a titanium gypsum-modified subgrade soil, its preparation method, and its application, in order to at least solve one of the technical problems existing in the prior art.

[0006] In a first aspect, this application provides a titanium gypsum modified subgrade soil, which comprises the following raw materials by mass percentage: 5%~10% titanium gypsum, 60%~75% natural subgrade soil, 5%~15% modifier, and 8%~20% water.

[0007] In one embodiment, the modifier is a compound of an activator, a stabilizer, and a reinforcing agent in a mass ratio of 4-5:3:1-2.

[0008] In one embodiment, the activator is quicklime and / or carbide slag, the stabilizer is fly ash and / or slag powder, and the reinforcing agent is metakaolin and / or silica fume.

[0009] In one embodiment, the natural subgrade soil is clay or sand, wherein the clay has a liquid limit of ≤50% and a plasticity index of 15~25, and the sand has a fineness modulus of 2.0~3.0 and a mud content of ≤5%.

[0010] In one embodiment, before preparing the titanium gypsum-modified subgrade soil, the titanium gypsum needs to be washed, dehydrated, dried, and sieved with deionized water to ensure that the moisture content of the treated titanium gypsum is ≤15%.

[0011] Secondly, this application provides a method for preparing titanium gypsum-modified subgrade soil, the preparation method comprising: Weigh out titanium gypsum, natural subgrade soil and modifier according to the proportion, mix them, dry mix for 2-3 minutes to obtain a mixture, then add water to the mixture and wet mix for 3-5 minutes to obtain the initial titanium gypsum modified subgrade soil. The initial titanium gypsum modified subgrade soil is left to stand at room temperature for 12-24 hours to obtain the titanium gypsum modified subgrade soil.

[0012] In one embodiment, the titanium gypsum needs to be washed, dehydrated, dried, and sieved with deionized water before mixing and dry-blending, so that the moisture content of the treated titanium gypsum is ≤15%. Before being mixed and dry-mixed, the natural subgrade soil needs to be crushed, sieved, and dried until the moisture content is ≤20%. The modifier needs to be sieved before mixing and dry-stirring.

[0013] Thirdly, this application provides an application of titanium gypsum modified subgrade soil in subgrade filling, wherein the titanium gypsum modified subgrade soil is used for non-waterlogged subgrade filling of highways below Grade 2, municipal roads, and rural roads.

[0014] In one possible implementation, the top surface of the non-submerged roadbed is ≥1.5m below the groundwater level.

[0015] In one possible embodiment, the application method of the titanium gypsum modified subgrade soil in subgrade filling includes: The titanium gypsum modified subgrade soil is filled into the subgrade surface to be paved, spread in layers, and compacted to obtain the embankment subgrade, with the compaction degree of the embankment subgrade being ≥95%; the embankment subgrade is cured in a curing environment temperature ≥5℃, so that the compressive strength after natural curing is ≥3MPa after 7 days, the compressive strength after curing is ≥5MPa after 28 days, and the CBR value is ≥8%.

[0016] Compared with the prior art, the advantages of this application are: 1) This application realizes the large-scale and resource-based utilization of titanium gypsum. Each ton of titanium gypsum modified subgrade soil can consume 0.05-0.1 tons of titanium gypsum, which greatly reduces the pollution from titanium gypsum stockpiling; it replaces 5%-10% of natural subgrade soil, reduces the mining of natural subgrade soil, and reduces carbon emissions from engineering projects.

[0017] 2) The titanium gypsum using industrial solid waste in this application has a procurement cost that is much lower than that of natural base materials; the modifier uses industrial by-products (fly ash, carbide slag) instead of traditional single modifiers (cement / lime), and the cost of each ton of titanium gypsum modified subgrade soil is reduced by 15%-25% compared with traditional cement modified soil, which significantly saves project investment.

[0018] 3) The titanium gypsum modified subgrade soil of this application not only realizes the effective utilization of titanium gypsum industrial solid waste and the high-value and large-scale resource utilization of titanium gypsum, but also reduces the use of natural subgrade soil, reduces the construction cost of road engineering, and improves the performance of subgrade engineering.

[0019] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this disclosure, nor is it intended to limit the scope of this disclosure. Other features of this disclosure will become readily apparent from the following description. Attached Figure Description

[0020] The above and other objects, features, and advantages of this disclosure will become readily apparent from the following detailed description of exemplary embodiments, taken in conjunction with the accompanying drawings. Several embodiments of this disclosure are illustrated in the drawings by way of example and not limitation, in which: In the accompanying drawings, the same or corresponding reference numerals indicate the same or corresponding parts.

[0021] Figure 1 A schematic diagram of the preparation process according to an embodiment of this disclosure is shown. Detailed Implementation

[0022] To make the objectives, features, and advantages of this disclosure more apparent and understandable, the technical solutions in the embodiments of this disclosure 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 this disclosure, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0023] The purpose of this application is to solve the problems of difficult disposal of titanium gypsum, shortage of natural roadbed filler resources, and high cost of roadbed soil modification. It provides a titanium gypsum-modified roadbed soil, its preparation method and application, so as to realize the high-value and large-scale resource utilization of titanium gypsum, while reducing the construction cost of road engineering and improving the performance of roadbed engineering.

[0024] In a first aspect, this application provides a titanium gypsum modified subgrade soil, which is prepared from the following raw materials in the indicated mass percentages: 5%~10% titanium gypsum, 60%~75% natural subgrade soil, 5%~15% modifier, and 8%~20% water.

[0025] This application achieves large-scale resource utilization of titanium gypsum. Each ton of titanium gypsum-modified subgrade soil consumes 0.05-0.1 tons of titanium gypsum, significantly reducing pollution from titanium gypsum stockpiling; it replaces 5%-10% of natural subgrade soil, reducing natural subgrade soil extraction and lowering carbon emissions from engineering projects. In this application, the titanium gypsum, derived from industrial solid waste, has a procurement cost far lower than that of natural materials; the modifier uses industrial byproducts (fly ash, carbide slag) to replace part of the traditional single modifier (such as cement / lime), reducing the cost of each ton of titanium gypsum-modified subgrade soil by 15%-25% compared to traditional cement-modified soil, significantly saving on engineering investment. Therefore, the titanium gypsum-modified subgrade soil of this application not only achieves effective utilization of titanium gypsum industrial solid waste, realizing high-value and large-scale resource utilization of titanium gypsum, but also reduces the use of natural subgrade soil, lowering road construction costs, and improving subgrade engineering performance.

[0026] For example, the mass percentage of the titanium plaster is 5%, 6%, 7%, 8%, 9%, 10%, and any value between two adjacent values. The mass percentage of the natural subgrade soil is 60%, 65%, 70%, 75%, and any value between two adjacent values. The mass percentage of the modifier is 5%, 8%, 10%, 13%, 15%, and any value between two adjacent values. The mass percentage of water is 8%, 10%, 15%, 20%, and any value between two adjacent values. The mass percentage of water can be adjusted according to the initial moisture content of the natural subgrade soil.

[0027] The modifier is composed of an activator, a stabilizer, and a reinforcing agent in a mass ratio of 4-5:3:1-2. For example, the modifier is composed of an activator, a stabilizer, and a reinforcing agent in a mass ratio of 4:3:1 or 5:3:2.

[0028] For example, the activator is quicklime and / or carbide slag, the stabilizer is fly ash and / or slag powder, and the reinforcing agent is metakaolin and / or silica fume. When carbide slag is used instead of quicklime as the activator in the modifier, costs can be reduced. The carbide slag needs to be slaked (moisture content ≤10%).

[0029] For example, the natural subgrade soil is clay or sand, with the clay having a liquid limit ≤50% and a plasticity index of 15~25, and the sand having a fineness modulus of 2.0~3.0 and a mud content ≤5%.

[0030] For example, before preparing titanium gypsum-modified subgrade soil, the titanium gypsum needs to be washed, dehydrated, dried, and sieved with deionized water to ensure that the moisture content of the treated titanium gypsum is ≤15%. Washing with deionized water removes easily soluble salts (such as soluble sulfates) from the titanium gypsum, reducing the SO4²⁻ content after washing. - The content is ≤0.5%. This dehydration includes, but is not limited to, physical dehydration and dehydration with dehydrating agents to remove free water from the titanium gypsum. The drying includes, but is not limited to, direct sun-drying. The sieving can use a 20mm sieve to remove large impurities. For example, the number of deionization washes of the titanium gypsum can be adjusted according to the content of readily soluble salts in the original titanium gypsum; if the original titanium gypsum contains SO4²⁻… - If the content is ≤1%, it can be washed only once.

[0031] Secondly, this application also provides a method for preparing the titanium gypsum-modified subgrade soil, the method comprising: Step 1): Weigh out titanium gypsum, natural subgrade soil and modifier according to the proportion of each raw material in the above titanium gypsum modified subgrade soil, mix them and dry mix for 2-3 minutes to obtain a uniformly mixed mixture. Then add water to the mixture and wet mix for 3-5 minutes to ensure uniform moisture content of the material and obtain the initial titanium gypsum modified subgrade soil. Step 2) The initial titanium gypsum modified subgrade soil is piled up at room temperature for 12-24 hours to obtain titanium gypsum modified subgrade soil. During the pile-up process at room temperature, the modifier fully reacts with titanium gypsum and natural subgrade soil to form a preliminary gel structure, i.e., titanium gypsum modified subgrade soil.

[0032] The preparation process of this application is simple, and existing road construction equipment can be used without the need for additional special equipment. The maintenance cycle is short, and the subgrade strength requirement can be met in 7 days, thus accelerating the construction progress.

[0033] For example, in step 1), both dry mixing and wet mixing are achieved using a forced mixer.

[0034] For example, in step 1), the titanium gypsum needs to be washed, dehydrated, dried, and sieved with deionized water before mixing and dry-mixing, so that the moisture content of the treated titanium gypsum is ≤15%.

[0035] For example, in step 1), the natural subgrade soil needs to be crushed, sieved, and dried until the moisture content is ≤20% before mixing. For example, the natural subgrade soil is crushed and sieved through a 40mm sieve, and then dried to reduce the moisture content as much as possible (for example, dried until the moisture content is 18±2%).

[0036] For example, in step 1), the modifier needs to be sieved before mixing. Exemplarily, the activator, stabilizer, and reinforcing agent are each sieved through a 100-mesh sieve and then mixed evenly in proportion for later use.

[0037] Thirdly, this application also provides the application of titanium gypsum modified subgrade soil in subgrade filling, which is used for non-waterlogged subgrade filling of highways below Class 2.

[0038] For example, the application method of this titanium gypsum modified subgrade soil in subgrade filling includes: filling the subgrade surface to be paved with titanium gypsum modified subgrade soil, spreading it in layers, compacting it to obtain the embankment subgrade, so that the compaction degree of the embankment subgrade is ≥95%; curing the embankment subgrade at a curing environment temperature ≥5℃, so that the compressive strength after natural curing for 7 days is ≥3MPa, the compressive strength after curing for 28 days is ≥5MPa, and the CBR value is ≥8%.

[0039] When the titanium gypsum-modified subgrade soil prepared in this application is used for subgrade filling, the resulting subgrade has good compaction performance (compaction degree ≥95%), compressive strength ≥5MPa after 28 days of curing, CBR value ≥8%, water stability (strength loss rate ≤15% after 7 days of water saturation) and frost resistance (strength loss rate ≤20% after 15 freeze-thaw cycles) all meet the requirements of the subgrade engineering technical specifications. It can reduce the plasticity index for clay subgrade soil and increase the bond strength for sandy subgrade soil.

[0040] For example, the top surface of a non-submerged roadbed should be at least 1.5m below the groundwater level.

[0041] For example, the titanium gypsum modified subgrade soil of this application can be used for subgrade filling (including upper subgrade, lower subgrade, and lower embankment) of Class II and below highways, and can also be used for subgrade filling projects of municipal roads and rural roads. The applicable environment is non-waterlogged subgrade (the top surface of the subgrade is ≥1.5m from the groundwater level).

[0042] For example, titanium gypsum-modified subgrade soil is filled into the surface of the subgrade to be paved, and then spread and compacted in layers (e.g., using a road roller for two static passes and three to four vibratory passes) to obtain an embankment subgrade. The compaction degree of this embankment subgrade is ≥95%; under curing conditions with an ambient temperature ≥5℃, the compressive strength is ≥3MPa after 7 days of natural curing, and ≥5MPa after 28 days of curing, with a CBR value ≥8%. This fully meets the subgrade technical requirements. For example, geotextile can be used for moisture retention during curing to accelerate strength development.

[0043] The present application will be further described in detail below with reference to embodiments: Unless otherwise specified, all materials used in this application are commercially available.

[0044] Example 1 A titanium gypsum-modified subgrade soil comprises the following raw materials by mass percentage: 10% titanium gypsum, 72% clay, 10% modifier, and 8% water. The modifier is composed of quicklime, fly ash, and metakaolin mixed in a mass ratio of 4:3:1. The clay has a liquid limit of 45%, a plasticity index of 20, and an initial moisture content of 22%.

[0045] The preparation method of this titanium gypsum modified subgrade soil adopts the following steps: Step 1), Preparation of raw materials: Titanium plaster preparation: Wash the titanium plaster three times with deionized water (SO4²⁻). - The content was reduced to 0.4%, dehydrated, dried until the moisture content was 12%, and passed through a 20mm sieve to obtain pretreated titanium gypsum.

[0046] Clay preparation: Crush the clay and pass it through a 40mm sieve, then dry it until the moisture content is 20%.

[0047] Modifier preparation: Quicklime, fly ash, and metakaolin are passed through a 100-mesh sieve and mixed in a ratio of quicklime:fly ash:metakaolin = 4:3:1 to obtain the modifier.

[0048] Step 2), mix all ingredients: Weigh the pretreated titanium gypsum, clay and modifier obtained in step 1) according to the proportion, put them into a forced mixer and dry mix for 3 minutes until the raw materials are evenly mixed to obtain a mixture; then add water to the mixture and wet mix for 4 minutes to ensure that the moisture content of the raw materials is uniform, and obtain the initial titanium gypsum modified subgrade soil.

[0049] Step 3), curing and maturation: The initial titanium gypsum modified subgrade soil obtained in step 2) is left to stand at room temperature for 24 hours to obtain titanium gypsum modified subgrade soil.

[0050] Application of the titanium gypsum-modified subgrade soil prepared in Example 1: The titanium gypsum modified subgrade soil prepared in Example 1 was used for subgrade filling. Specifically, the titanium gypsum modified subgrade soil was filled into the subgrade surface to be paved, spread and compacted in layers, and subjected to two static compaction passes and four vibratory compaction passes (compaction degree of 96%) to obtain the embankment subgrade. The embankment subgrade was then cured in an environment with a temperature ≥5℃. The compressive strength after 7 days of natural curing was 3.5MPa, the compressive strength after 28 days was 5.8MPa, the CBR value was 9.2%, and the strength loss rate after 7 days of water saturation was 12%.

[0051] Example 2 A titanium gypsum-modified subgrade soil comprises the following raw materials in weight percentages: 10% titanium gypsum, 60% sand, 15% modifier, and 15% water. The modifier is composed of quicklime, slag powder, and silica fume mixed in a weight ratio of 5:3:2. The sand has a fineness modulus of 2.5, a mud content of 3%, and an initial moisture content of 8%. The preparation method of the titanium gypsum-modified subgrade soil includes the following steps: Step 1), Preparation of raw materials: Titanium plaster preparation: Wash the titanium plaster three times with deionized water (SO4²⁻). - The content was reduced to 0.4%, dehydrated, dried until the moisture content was 12%, and passed through a 20mm sieve to obtain pretreated titanium gypsum.

[0052] Sand preparation: Pass the sand through a 40mm sieve and set aside.

[0053] Modifier preparation: Quicklime, slag powder and silica fume are passed through a 100-mesh sieve, and then the quicklime, slag powder and silica fume are mixed evenly in a mass ratio of 5:3:2 to obtain the modifier.

[0054] Step 2), mix all ingredients: Weigh the pretreated titanium gypsum, sand and modifier obtained in step 1) according to the proportion, put them into a forced mixer and dry mix for 2 minutes until the raw materials are evenly mixed to obtain a mixture; then add water to the mixture and wet mix for 5 minutes to ensure that the moisture content of the raw materials is uniform, and obtain the initial titanium gypsum modified subgrade soil.

[0055] Step 3), curing and maturation: The initial titanium gypsum modified subgrade soil obtained in step 2) is left to stand at room temperature for 18 hours to obtain titanium gypsum modified subgrade soil.

[0056] Application of the titanium gypsum-modified subgrade soil prepared in Example 2: The titanium gypsum modified subgrade soil prepared in Example 2 was used for subgrade filling. Specifically, the titanium gypsum modified subgrade soil was filled into the subgrade surface to be paved, spread and compacted in layers, and subjected to two static compaction passes and four vibratory compaction passes (compaction degree of 95%) to obtain the embankment subgrade. The embankment subgrade was then cured in an environment temperature ≥5℃. The compressive strength after 7 days of natural curing was 3.2MPa, the compressive strength after 28 days was 5.5MPa, the CBR value was 8.5%, and the strength loss rate after 15 freeze-thaw cycles was 18%.

[0057] Comparative Example 1 (Unmodified titanium gypsum was directly mixed into clay to obtain subgrade soil) A titanium gypsum subgrade soil comprises the following raw materials by mass percentage: 10% titanium gypsum, 70% clay, and 20% water. The clay has a liquid limit of 45%, a plasticity index of 20, and an initial moisture content of 22%.

[0058] The preparation method of this titanium gypsum subgrade soil adopts the following steps: Step 1), Raw material preparation: Clay preparation: Crush the clay and pass it through a 40mm sieve, then dry it until the moisture content is 20%.

[0059] Step 2), mix all ingredients: Weigh out the titanium gypsum and the clay obtained in step 1) according to the proportion, put them into a forced mixer and dry mix for 3 minutes until the raw materials are evenly mixed; then add water and wet mix for 4 minutes to ensure that the moisture content of the raw materials is uniform, and obtain the initial subgrade soil.

[0060] Step 3), curing and maturation: The initial subgrade soil obtained in step 2) is left to stand at room temperature for 24 hours to obtain titanium gypsum subgrade soil.

[0061] Application of the titanium gypsum subgrade soil prepared in Comparative Example 1: The titanium gypsum subgrade soil prepared in Comparative Example 1 was used for subgrade filling. Specifically, the titanium gypsum subgrade soil was filled into the subgrade surface to be paved, spread and compacted in layers, and subjected to two static compaction passes and four vibratory compaction passes (compaction degree of 88%) to obtain the embankment subgrade. The embankment subgrade was then cured in an environment temperature ≥5℃. The compressive strength after 7 days of natural curing was 1.2MPa, the compressive strength after 28 days was 2.0MPa, the CBR value was 3.5%, and the strength loss rate after 7 days of water saturation was 45%, which did not meet the subgrade technical requirements.

[0062] Comparative Example 2 (Titanium gypsum modified subgrade soil obtained by modifying titanium gypsum with quicklime alone) Comparative Example 2 is largely the same as Example 1, except that only quicklime is used as the modifier.

[0063] Comparative Example 2 prepared titanium gypsum modified subgrade soil.

[0064] Application of the titanium gypsum-modified subgrade soil prepared in Comparative Example 2: The titanium gypsum-modified subgrade soil prepared in Comparative Example 2 was used for subgrade filling. Specifically, the titanium gypsum-modified subgrade soil was filled into the subgrade surface to be paved, spread and compacted in layers, and subjected to two static compactions and four vibratory compactions with a road roller (compaction degree of 96%) to obtain the embankment subgrade. The embankment subgrade was then cured at an ambient temperature ≥5℃. The compressive strength after 7 days of natural curing was 2.8 MPa, the compressive strength after 28 days was 4.2 MPa, the CBR value was 6.8%, and the strength loss rate after 7 days of water saturation was 22%. The performance of the embankment subgrade prepared in Comparative Example 2 was lower than that of Example 1. This indicates that the raw materials of the modifier have a significant impact on the performance of the embankment subgrade obtained when the titanium gypsum-modified subgrade soil is used for subgrade filling. This further proves that the modifier of this application is superior to traditional modifiers, not only enabling solid waste reuse and cost savings, but also improving subgrade strength requirements and construction efficiency.

[0065] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this disclosure can be achieved, and this is not limited herein.

[0066] 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 as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "a plurality of" means two or more, unless otherwise explicitly specified.

[0067] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A titanium gypsum-modified subgrade soil, characterized in that, The titanium gypsum modified subgrade soil comprises the following raw materials by mass percentage: titanium gypsum 5%~10%, natural subgrade soil 60%~75%, modifier 5%~15%, and water 8%~20%.

2. The titanium gypsum-modified subgrade soil according to claim 1, characterized in that, The modifier is a compound of activator, stabilizer and reinforcing agent in a mass ratio of 4~5:3:1~2.

3. The titanium gypsum-modified subgrade soil according to claim 2, characterized in that, The activator is quicklime and / or carbide slag, the stabilizer is fly ash and / or slag powder, and the reinforcing agent is metakaolin and / or silica fume.

4. The titanium gypsum-modified subgrade soil according to claim 1, characterized in that, The natural subgrade soil is clay or sand, wherein the liquid limit of the clay is ≤50% and the plasticity index of the clay is 15~25, and the fineness modulus of the sand is 2.0~3.0 and the mud content of the sand is ≤5%.

5. The titanium gypsum-modified subgrade soil according to claim 1, characterized in that, Before preparing the titanium gypsum-modified subgrade soil, the titanium gypsum needs to be washed, dehydrated, dried, and sieved with deionized water to ensure that the moisture content of the treated titanium gypsum is ≤15%.

6. A method for preparing titanium gypsum-modified subgrade soil as described in any one of claims 1-5, characterized in that, The preparation method includes: Weigh out titanium gypsum, natural subgrade soil and modifier according to the proportion, mix them, dry mix for 2-3 minutes to obtain a mixture, then add water to the mixture and wet mix for 3-5 minutes to obtain the initial titanium gypsum modified subgrade soil. The initial titanium gypsum modified subgrade soil is left to stand at room temperature for 12-24 hours to obtain the titanium gypsum modified subgrade soil.

7. The preparation method according to claim 6, characterized in that, Before mixing and dry blending, the titanium gypsum needs to be washed, dehydrated, dried, and sieved with deionized water to ensure that the moisture content of the treated titanium gypsum is ≤15%. Before being mixed and dry-mixed, the natural subgrade soil needs to be crushed, sieved, and dried until the moisture content is ≤20%. The modifier needs to be sieved before mixing and dry-stirring.

8. The application of titanium gypsum modified subgrade soil as described in any one of claims 1-5, or titanium gypsum modified subgrade soil prepared by the preparation method as described in claim 6 or 7, in subgrade filling, characterized in that, The titanium gypsum modified subgrade soil is used for non-waterlogged subgrade filling of highways below Grade 2, municipal roads, and rural roads.

9. The application according to claim 8, characterized in that, The top surface of the non-submerged roadbed is ≥1.5m from the groundwater level.

10. The application according to claim 8, characterized in that, The application methods of the titanium gypsum-modified subgrade soil in subgrade filling include: The titanium gypsum modified subgrade soil is filled into the subgrade surface to be paved, spread in layers, and compacted to obtain the embankment subgrade, with the compaction degree of the embankment subgrade being ≥95%; the embankment subgrade is cured in a curing environment temperature ≥5℃, so that the compressive strength after natural curing is ≥3MPa after 7 days, the compressive strength after curing is ≥5MPa after 28 days, and the CBR value is ≥8%.

Images