A fluidified solidified soil material suitable for repairing a historic site soil and a method for preparing the same

Abstract

The present application relates to a kind of flow state solidified soil material suitable for site soil repair and its preparation method, material is based on 100 parts of dry soil by weight, including 100 parts of solidified native soil to be, calcium lignosulfonate 1~3 parts, EICP composite cementing fluid 10~25 parts, xanthan gum 0.5~3 parts, pregelatinized starch 2 parts, lime 1 part.The present application changes the ramming repair strategy of traditional site soil disease, constructs ternary synergistic solidification system, based on the characteristics of flow state solidified soil, such as flowable, self-compacting, green, it solves the dilemma that traditional cement-based material and cultural relics body are poor in compatibility, cause damage to ecological environment;Solidified body and original rammed earth material properties are highly matched, meet the requirements of minimum intervention, reversible compatibility of cultural relic protection, and ecological environmental friendliness is excellent, can be adapted to various construction scenes, such as in-situ repair of site soil crack and gully disease, realize long-acting green repair of site soil disease.

Description

Technical Field

[0001] This invention relates to the field of historical and cultural heritage protection technology, and in particular to a fluidized solidified soil material suitable for the restoration of archaeological sites and its preparation method. Background Technology

[0002] Earthen sites (such as Jiaohe Ancient City and the Great Wall) are important cultural heritage sites in my country. These sites are mostly made of rammed earth, and are highly susceptible to damage from long-term exposure to rainwater erosion, wet-dry cycles, freeze-thaw weathering, and salt migration. This makes them prone to surface weathering and peeling, crack expansion, and localized collapse, resulting in continuous loss of the integrity and structural stability of the artifacts. Since the soil of these sites is a non-renewable cultural relic, restoration must strictly adhere to the principles of minimal intervention, preservation of the original appearance, avoidance of secondary damage, and environmental friendliness.

[0003] Existing methods for the restoration of earthen sites mainly employ traditional techniques such as grouting reinforcement, surface spraying of organic reinforcing agents, and localized ramming. These methods are insufficient for the green restoration of rammed earth site defects and have problems such as insufficient compatibility with the original soil, easy cracking at the interface, and difficulty in uniformly controlling the density, making it difficult to achieve overall synergistic stability.

[0004] While conventional engineering fluidized bed technology boasts advantages such as high fluidity, self-compacting, vibration-free operation, and good overall consolidation, and has been applied in geotechnical engineering fields such as roadbed backfilling and site leveling, existing fluidized bed formulations and construction processes are designed for ordinary soils and have not been adapted to the mineral composition, pore structure, strength matching, and special requirements of cultural relic protection of archaeological site soils. This results in problems such as uncontrollable solidification rate, strength mismatch, excessive shrinkage deformation, and poor compatibility with the original appearance. There is currently no dedicated fluidized bed formulation or complete set of restoration processes specifically for the treatment of archaeological site soil diseases and structural repair, which cannot meet the actual engineering needs for minimally invasive, reversible, and long-term restoration of earthen archaeological sites. Summary of the Invention

[0005] To address the aforementioned issues, the present invention aims to provide a fluidized solidified soil material suitable for the restoration of archaeological sites and its preparation method. The material uses EICP, modified lignin, and xanthan gum as bio-based solidifying agents. All components of the material are free of high-pollution substances such as cement and slag. It also possesses excellent fluidized construction performance, controllable solidification strength, high compatibility with native rammed earth, and long-term durability, fully complying with the core principles of the protection of earthen archaeological sites such as the rammed earth Great Wall.

[0006] The technical solution adopted in this invention is as follows:

[0007] The fluidized solidified soil material proposed in this invention is suitable for the restoration of archaeological sites. Based on the dry soil quality, it is composed of the following raw materials in parts by weight: 100 parts of the original rammed soil to be solidified, 10-25 parts of EICP cementitious liquid, 1-3 parts of calcium lignosulfonate, 0.5-3 parts of xanthan gum, 2 parts of pregelatinized starch, and 1 part of lime. The initial moisture content of the original rammed soil to be solidified is 30%~60%, corresponding to a soil liquid limit of 1.5 times, which is a fluid-state soil with high moisture content.

[0008] Furthermore, the EICP composite cementing solution includes a urea-calcium source buffer solution and a urease solution, with a volume ratio of 1:1.

[0009] A method for preparing a fluidized solidified soil material suitable for the restoration of archaeological sites, the method comprising the following steps: Step 1, Soil Pretreatment: Take the original soil, remove impurities and pass it through a 2mm sieve, then add lime and pregelatinized starch according to the ratio, and adjust the moisture content to 30%~60% according to the target flow requirements; Step 2: Preparation of modified lignin premix; Step 3, Premixing of fluid soil matrix: Add the modified lignin premix liquid obtained in step 2 and xanthan gum to the soil material in step 1, stir evenly, so that the biopolymer and soil particles can be fully contacted and pre-bonded to obtain fluid soil matrix. Step 4: Preparation of urea-calcium source buffer solution and urease solution; Step 5, on-site mixing and construction: Add the urea-calcium source buffer solution to the fluidized soil matrix, stir evenly, then add the urease solution, stir at low speed until uniform, and obtain the fluidized solidified soil mixture.

[0010] Further, step 2 includes: taking calcium lignin sulfonate according to the ratio, adding it to warm water at 30~40℃, stirring at 300~500r / min for 15~20min to obtain a uniformly dispersed lignin premix, adjusting the pH value to 7.0~7.5 with sodium citrate, and setting it aside for later use.

[0011] Furthermore, in step 4, the preparation of the urease solution includes: putting dried soybeans into a grinder to grind them, then mixing the uniform small-particle soybean powder with water in a ratio of 1:2, stirring thoroughly on a magnetic stirrer, and finally centrifuging the soybean powder solution at a speed of 5800~6200 r / min on a centrifuge for 25~35 min, and extracting the upper yellow clear liquid after separation, which is the urease solution.

[0012] Furthermore, in step 4, the preparation of the urea-calcium source buffer solution includes: weighing urea and calcium chloride according to the ratio and dissolving them in water and stirring evenly, with the volume ratio of the three being 1:1:1, to obtain the urea-calcium source buffer solution.

[0013] Furthermore, in step 3, the parameters for uniform stirring are as follows: rotation speed of 600~800 r / min and stirring time of 5~10 min.

[0014] Furthermore, step 5 includes: adding the urea-calcium source buffer solution obtained in step 4 to the fluidized soil matrix obtained in step 3, stirring evenly, then adding urease solution, stirring at low speed for 2-3 minutes to obtain the fluidized solidified soil mixture.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. All components of this invention are bio-based materials, free of highly alkaline and polluting cementitious components such as cement and slag, and release no toxic or harmful substances. They will not cause irreversible damage to the soil, microbial community and environment of the site.

[0016] 2. The high water content mud-like soil of the present invention can achieve a stable flowability of 180~220mm for the mixture, with no bleeding or segregation, and can meet various construction requirements such as pumping, low-pressure grouting, and in-situ casting. The construction process does not require large equipment and causes minimal disturbance to the site itself.

[0017] 3. The present invention has reliable curing performance and is highly compatible with the original rammed earth: the strength of the solidified body can be precisely controlled by adjusting the component dosage, which fully meets the strength requirements of the site soil restoration; at the same time, the porosity, air permeability and thermal expansion coefficient of the solidified body match the original rammed earth by ≥90%, there is no volume shrinkage after curing, and there will be no common diseases of traditional materials such as interface debonding, secondary cracking, salt migration and alkali efflorescence.

[0018] 4. The raw materials of this invention are widely available and the cost is controllable, making it suitable for large-scale promotion. The core raw material, modified lignin, is a bulk industrial by-product of the papermaking industry and biomass refining. Urease is a low-cost plant-derived crude extract, and xanthan gum is a biopolymer that does not require expensive purification processes. It is suitable for large-scale protection and application of large-scale earthen sites such as the rammed earth Great Wall. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the original rammed earth structure before solidification. Figure 2 This is a schematic diagram of the microstructure of the original rammed earth after it has been fluidized and solidified by the material of this invention. Detailed Implementation

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] It should be noted that in the description of this invention, the terms "upper", "lower", "top", "bottom", "one side", "the other side", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not mean that the device or element must have a specific orientation, or be constructed and operated in a specific orientation.

[0022] The fluidized solidified soil material proposed in this invention is suitable for the restoration of archaeological sites. Based on the dry soil quality, it is composed of the following raw materials in parts by weight: 100 parts of the original rammed soil to be solidified, 10-25 parts of EICP cementitious liquid, 1-3 parts of calcium lignosulfonate, 0.5-3 parts of xanthan gum, 2 parts of pregelatinized starch, and 1 part of lime.

[0023] The initial moisture content of the original rammed soil to be solidified is 30% to 60%, corresponding to a soil liquid limit of 1.5 times, which is a fluid-state soil with high moisture content.

[0024] The EICP composite cementing solution includes a urea-calcium source buffer solution and a urease solution, with a volume ratio of 1:1.

[0025] Xanthan gum is a microbial fermentation-derived biopolymer. As a rheology modifier, it is used to solve the problems of bleeding and segregation in high-moisture-content fluid soil, and to regulate the fluidity of the mixture to 180~220mm to meet the requirements of pumping and low-pressure grouting construction. At the same time, the polymer network of xanthan gum can form an interpenetrating structure with lignin and EICP reaction products, further improving the long-term stability of the solidified body.

[0026] The EICP composite cementing solution is a plant-derived urease-based composite system, comprising a urea-calcium source buffer solution and a urease solution.

[0027] In this invention, the addition of lime and pregelatinized starch is to obtain a prepared soil with the same material composition as the soil of the in-situ site; EICP (enzyme-induced calcium carbonate precipitation) technology can generate calcium carbonate crystals in situ between soil particles; calcium lignin sulfonate provides more nucleation sites for calcium carbonate precipitation, forming a bio-cementitious agent that adheres tightly to the surface and contact points of soil particles and effectively fills the micropores between particles, promoting the particles to bond together into an integral structure, thereby effectively limiting load displacement and improving overall stability.

[0028] To address the complex irrigation problems caused by soil fissures and gullies in archaeological sites, this invention introduces multiple rheology modifiers into the formulation: Calcium lignosulfonate, as an anionic surfactant, can effectively reduce the viscosity of soil materials. In the early stages of the reaction, it enhances the fluidity of the material through electrostatic repulsion, giving the material a "fluid" characteristic. During the curing stage, its functional groups (such as hydroxyl, carboxyl, and sulfonic acid groups) can serve as active sites for crystal nucleation, adsorbing calcium ions in the solution and guiding the uniform precipitation of calcium carbonate to form a denser microstructure.

[0029] Xanthan gum acts as a thickener and stabilizer. By forming a three-dimensional network structure, it prevents the segregation of solid particles during fluid construction, ensuring that the material achieves "self-compactment" without the need for manual compaction.

[0030] Unlike the highly alkaline hydrated calcium silicate produced by traditional cement, the calcium carbonate generated by EICP is a common component in natural soil. Its physicochemical properties are highly compatible with those of the original rammed soil. Calcium lignosulfonate and xanthan gum, as biomass solidifying agents, ensure the mechanical properties of the remediated soil without causing environmental pollution.

[0031] A method for preparing a fluidized solidified soil material suitable for the restoration of archaeological sites, the method comprising the following steps: Step 1, Soil Pretreatment: Take the original soil, remove impurities and pass it through a 2mm sieve, then add lime and pregelatinized starch according to the ratio, and adjust the moisture content to 30%~60% according to the target flow requirements; Step 2: Preparation of modified lignin premix: Take calcium lignin sulfonate according to the ratio, add it to warm water at 30~40℃, stir at 300~500r / min for 15~20min to obtain a uniformly dispersed lignin premix. Adjust the pH value to 7.0~7.5 with sodium citrate and set aside.

[0032] Step 3, Premixing of fluid soil matrix: Add the modified lignin premixed liquid obtained in step 2 and xanthan gum to the soil material in step 1 according to the ratio, and stir at 600~800 r / min for 5~10 min to allow the biopolymer to fully contact and pre-bond with the soil particles to obtain a fluid soil matrix.

[0033] Step 4: Preparation of urea-calcium source buffer solution and urease solution; The preparation of urease solution includes: putting dried soybeans into a grinder to grind them, then mixing the uniform small soybean powder with water at a volume ratio of 1:2, stirring thoroughly on a magnetic stirrer, and finally centrifuging the soybean powder solution at a speed of 5800~6200 r / min on a centrifuge for 25~35 min, and extracting the upper yellow clear liquid after separation, which is the urease solution.

[0034] The preparation of urea-calcium source buffer solution includes: weighing urea and calcium chloride according to the ratio and dissolving them in water and stirring evenly. The volume ratio of the three is 1:1:1. After stirring evenly, the urea-calcium source buffer solution is obtained.

[0035] The calcium chloride used has the chemical formula CaCl2 and a molecular weight of 110.98 g / mol. It is a white powder and granules that are easily soluble in water. The urea has the chemical formula CO(NH2)2 and a relative molecular weight of 60.06 g / mol. It is a colorless crystalline granule or a white crystalline powder that is soluble in water.

[0036] Before use, weigh out the urease preparation according to the ratio and dissolve it in sterile water to obtain a urease solution; store the urease solution separately from the urea-calcium source buffer solution to avoid premature reaction.

[0037] Step 5, on-site mixing and construction: Add the urea-calcium source buffer solution to the fluidized soil matrix obtained in step 3, stir evenly, then add the urease solution, stir at low speed for 2-3 minutes to obtain the fluidized solidified soil mixture.

[0038] The present invention will be further illustrated below through specific embodiments: Example 1 This embodiment proposes a fluidized solidified soil material suitable for the restoration of archaeological sites, the composition of which is shown in the table below:

[0039] This bio-based fluidized solidified soil material was prepared according to the following steps: Step 1, Soil pretreatment: Take the original soil, remove impurities and pass it through a 2mm sieve. Add lime and pregelatinized starch according to the ratio, adjust the moisture content to 45%, and set aside. Step 2, Preparation of modified lignin premix: Weigh calcium lignin sulfonate, add it to warm water at 35℃, stir at 400r / min for 15min to obtain a uniformly dispersed lignin premix, adjust the pH value to 7.0 with sodium citrate, and set aside. Step 3, Premixing of fluid soil matrix: Add lignin premix liquid and xanthan gum to the soil material and stir at 700 r / min for 8 min to allow the biopolymer to fully contact and pre-bond with the soil particles to obtain fluid soil matrix; Step 4: Preparation of urea-calcium source buffer solution and urease solution; The preparation of urease solution includes: putting dried soybeans into a grinder to grind them, then mixing the uniform small soybean powder with water at a volume ratio of 1:2, stirring thoroughly on a magnetic stirrer, and finally centrifuging the soybean powder solution at 6000 r / min for 30 min. The upper yellow clear liquid after separation is the urease solution.

[0040] The preparation of urea-calcium source buffer solution includes: weighing urea and calcium chloride according to the ratio and dissolving them in water and stirring evenly. The volume ratio of the three is 1:1:1. After stirring evenly, the urea-calcium source buffer solution is obtained.

[0041] Step 5, on-site mixing and construction: Add the urea-calcium source buffer solution to the fluid soil matrix, stir evenly, then add the urease solution, stir at low speed for 2 minutes to obtain the fluid solidified soil mixture; pour the mixture into shape, cover it with a moisture-retaining geotextile, and cure at room temperature.

[0042] The properties of the fluidized solidified soil material prepared in this embodiment were analyzed, and the test results are shown in the following table.

[0043]

[0044] Example 2 This embodiment proposes a fluidized solidified soil material suitable for the restoration of archaeological sites, the composition of which is shown in the table below:

[0045] This bio-based fluidized solidified soil material was prepared according to the following steps: Step 1, Soil pretreatment: Take the original soil, remove impurities and pass it through a 2mm sieve. Add lime and pregelatinized starch according to the ratio, adjust the moisture content to 55%, and set aside. Step 2, Preparation of modified lignin premix: Weigh calcium lignin sulfonate, add it to warm water at 35℃, stir at 300r / min for 20min to obtain a uniformly dispersed lignin premix, adjust the pH value to 7.5 with sodium citrate, and set aside. Step 3: Premixing of fluid soil matrix: Add lignin premix liquid, xanthan gum, and starch to the soil material and stir at 600 r / min for 10 min to allow the biopolymer to fully contact and pre-bond with the soil particles to obtain fluid soil matrix; Step 4: Preparation of urea-calcium source buffer solution and urease solution; The preparation of urease solution includes: putting dried soybeans into a grinder to grind them, then mixing the uniform small soybean powder with water at a volume ratio of 1:2, stirring thoroughly on a magnetic stirrer, and finally centrifuging the soybean powder solution at a speed of 6200 r / min on a centrifuge for 25 min, and extracting the upper yellow clear liquid after separation, which is the urease solution.

[0046] The preparation of urea-calcium source buffer solution includes: weighing urea and calcium chloride according to the ratio and dissolving them in water and stirring evenly. The volume ratio of the three is 1:1:1. After stirring evenly, the urea-calcium source buffer solution is obtained.

[0047] Step 5, on-site mixing and construction: Add the urea-calcium source buffer solution to the fluid soil matrix, stir evenly, then add the urease solution, stir at low speed for 3 minutes to obtain the fluid solidified soil mixture; pour the mixture into shape, cover it with a moisture-retaining geotextile, and cure at room temperature.

[0048] The properties of the fluidized solidified soil material prepared in this embodiment were analyzed, and the test results are shown in the table below.

[0049]

[0050] Experiments have shown that the bio-based fluidized solidified soil material prepared by this invention can still maintain excellent flow properties after preparation; at the same time, the solidified body has excellent strength, dry-wet cycle stability and erosion resistance, fully meeting the various requirements for the restoration of rammed earth sites.

[0051] Matters not covered in this invention are common knowledge.

[0052] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A fluidized solidified soil material suitable for the restoration of archaeological sites, characterized in that: The material, based on dry soil quality, consists of the following raw materials in parts by weight: 100 parts of original rammed soil to be solidified, 10-25 parts of EICP composite binder, 1-3 parts of calcium lignosulfonate, 0.5-3 parts of xanthan gum, 2 parts of pregelatinized starch, and 1 part of lime. The initial moisture content of the original rammed soil to be solidified is 30%~60%, corresponding to a soil liquid limit of 1.5 times, which is a fluid-state soil with high moisture content.

2. The fluidized solidified soil material suitable for the restoration of archaeological sites according to claim 1, characterized in that: The EICP composite cementing solution includes a urea-calcium source buffer solution and a urease solution, with a volume ratio of 1:

1.

3. A method for preparing a fluidized solidified soil material suitable for archaeological site restoration as described in claim 2, characterized in that, The method includes the following steps: Step 1, Soil Pretreatment: Take the original soil, remove impurities and pass it through a 2mm sieve, then add lime and pregelatinized starch according to the ratio, and adjust the moisture content to 30%~60% according to the target flow requirements; Step 2: Preparation of modified lignin premix solution; Step 3, Premixing of fluid soil matrix: Add the modified lignin premix liquid obtained in step 2 and xanthan gum to the soil material in step 1, stir evenly, so that the biopolymer and soil particles can be fully contacted and pre-bonded to obtain fluid soil matrix. Step 4: Preparation of urea-calcium source buffer solution and urease solution; Step 5, on-site mixing and construction: Add the urea-calcium source buffer solution to the fluidized soil matrix, stir evenly, then add the urease solution, stir at low speed until uniform, and obtain the fluidized solidified soil mixture.

4. The preparation method according to claim 3, characterized in that: Step 2 includes: taking calcium lignosulfonate according to the ratio, adding it to warm water at 30~40℃, stirring at 300~500r / min for 15~20min to obtain a uniformly dispersed lignin premixed solution, adjusting the pH value to 7.0~7.5 with sodium citrate, and setting it aside for later use.

5. The preparation method according to claim 3, characterized in that: In step 4, the preparation of the urease solution includes: putting dried soybeans into a grinder to grind them, then mixing the uniform small-particle soybean powder with water at a volume ratio of 1:2, stirring thoroughly on a magnetic stirrer, and finally centrifuging the soybean powder solution at a speed of 5800~6200r / min on a centrifuge for 25~35min, and extracting the upper yellow clear liquid after separation, which is the urease solution.

6. The preparation method according to claim 4, characterized in that: In step 4, the preparation of the urea-calcium source buffer solution includes: weighing urea and calcium chloride according to the ratio and dissolving them in water and stirring evenly, with the volume ratio of the three being 1:1:1, to obtain the urea-calcium source buffer solution.

7. The preparation method according to claim 3, characterized in that: In step 3, the parameters for uniform stirring are as follows: rotation speed is 600~800 r / min, and stirring time is 5~10 min.

8. The preparation method according to claim 7, characterized in that: Step 5 includes: adding the urea-calcium source buffer solution obtained in step 4 to the fluid soil matrix obtained in step 3, stirring evenly, then adding urease solution, stirring at low speed for 2-3 minutes to obtain the fluid solidified soil mixture.

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