Method of application of MICP to improve the life and strength of natural fiber-reinforced soils

Abstract

The present disclosure relates to a method (300) for enhancing life and strength of natural fiber-reinforced earth structure by utilizing carbon present in natural fiber as a carbon source for Microbially Induced Calcite Precipitation (MICP), the method includes preparing (302) a bacterial solution in a container, substituting (304) urea with natural fiber as the carbon source in the MICP, treating (306) the natural fiber with the bacterial solution to facilitate microbial activity, adding (308) calcium chloride solution to the treated natural fiber to initiate precipitation of calcium carbonate and depositing (310) the formed calcium carbonate on surface of the natural fiber, wherein the calcium carbonate strengthens the natural fiber and enhances reinforcement properties when incorporated into soil.

Description

METHOD OF APPLICATION OF MICP TO IMPROVE THE LIFE AND STRENGTH OF NATURAL FIBER-REINFORCED SOILSTECHNICAL FIELD

[0001] The present disclosure relates, in general, to reinforcing soil, and more specifically, relates to a method of application of Microbially Induced Calcite Precipitation (MICP) to improve the life and strength of natural fiber and natural fiber-based reinforced soils.BACKGROUND

[0002] The application of natural fibers to improve the shear strength and liquefaction resistance of soil is studied by various researchers. However, extensive use of these methods is found to be very limited because of the natural biodegradation of natural fibers. Apart from reinforcing techniques, Microbially Induced Calcite Precipitation (MICP) is also adopted these days to increase the shear strength of soil as discussed below along with its limitations. Currently, existing methods known in the art do not help to improve the life of natural fiber- reinforced soil with MICP, by treating natural fibers with MICP.

[0003] Sustainable and environment-friendly solutions for engineering problems are expected to be critical to meet the increasing global challenges in the future. One of the most adopted environmentally friendly solutions is the application of natural fibers as reinforcements in soil. With the presence of huge agricultural cover, a large amount of agricultural products and a substantial amount of agricultural residues are produced globally. Most of these agricultural residues are in the form of fibers e.g., rice husk, bagasse, coir etc., and can be in fact used as reinforcement of soils. However, using natural fibers as soil reinforcement cannot be considered a long-term solution as they degrade with time. This inspired the invention of a sustainable solution to improve the durability of naturally reinforced soil.

[0004] An example is recited in a patent CN201810690066A, the invention uses a microbial induced calcium carbonate precipitation method for solidifying sand soil by using an alternative calcium source. However, the invention explores the potential of kitchen waste, which is produced in small quantities. On the other hand, the proposed patent mainly explores how to retain soil strength improved by natural reinforcement with time.

[0005] Another example is recited in a patent CN201910617579A, the method of microbial induced calcium carbonate precipitation reinforcing soil is discussed in thisdisclosure. This patent uses a combined application of synthetic carbon fibers and MICP for soil reinforcement. Though the method helps in improving the strength of soil, the use of synthetic carbon fiber is not an environmentally friendly solution when it comes to massive soil enhancement or slope stability.

[0006] Another example is recited in a patent CN201811572106A. The patent reports microbial curing - steel fibers reinforced technique for soil enhancement. Even though this process leads to the reduction of the brittleness of soil and increases the strength of MICP- cured soil, the production of streel fibers in massive quantities is not sustainable. In contrast, the proposed patent may study the applicability of natural fiber, produced in huge quantities as a waste by-product, in combined reinforcement - MICP mechanism.

[0007] Another example is recited in a patent CN201910865458A that shows a soil improvement method using a basalt fiber-reinforced microorganism solidification technique. The procedure involves passing the microbial solution through the reinforced soil sample, which can lead to uneven distribution of nutrient solution in the sample. Another example is recited in a patent CN202011629983A that demonstrates a basalt fiber reinforced microorganism solidified sludge preparation. This patent studies the usability of polypropylene fiber, a synthetic fiber with MICP to enhance the expansive soils. Even though synthetic fibers can give good strength the environmental-economic effects of synthetic fibers are high. Yet another example is recited in a patent CN201910891383A that demonstrates a basalt fiber reinforced microorganism solidified sludge and preparation. However, the economical availability of a huge quantity of basalt fibers is very much limited.

[0008] The use of natural fibers is a sustainable solution to various engineering problems, particularly in geotechnical engineering. Construction of embankments, slopes, backfills and the like are large-scale earthworks, which require a huge quantity of earth materials with appropriate strength characteristics. Unfortunately, the availability of earth materials with proper strength is rare, which leads to the application of soil-strengthening methods like reinforcing. Numerous synthetic and natural reinforcements are used these days to meet these needs. However, the application of synthetic reinforcements on large scale is not capable of meeting the required substantial quantity of reinforcements and leads to environmental pollution. This point towards the use of natural fibers. Though natural fibers like bagasse, coir, and jute are available in huge quantities, the application of natural fibers in the soil is limited due to their short life on account of the biodegradation of fibers. Degradation of natural fibers can lead to an early failure of the natural fibre-reinforcedembankments and slopes. The proposed patent addresses this drawback of natural reinforcements.

[0009] Natural fibers possess significant potential for various applications, particularly within the geotechnical field. Previous efforts to study the strength of natural fiber-reinforced soil structures have demonstrated favorable strength outcomes; however, the durability of natural materials in soil for long-term applications has hindered their practical utilization, limiting the application of natural materials primarily to research contexts with minimal practical implementation. A substantial quantity of natural materials is produced as agricultural waste, which remains unused, leading to environmental, economic, and health issues. Microbially Induced Calcium Precipitation (MICP) is a process wherein specific bacteria convert urea into calcium carbonate in the presence of calcium chloride and water, although a major drawback of this method is the reliance on industry-based chemicals. Certain publications have suggested the use of calcium-rich eggshells as a calcium source for this process; however, no study has yet attempted to modify the carbon source. In this disclosure, natural fibers, which are rich in carbon, are utilized to replace urea as the carbon source in MICP. This approach seeks to overcome the drawbacks, shortcomings, and limitations associated with the application of natural fibers in soil applications, whether as random fibers, sheets, mats, fillings, or other forms, while also enhancing strength and durability. Furthermore, this development aims to effectively utilize natural fibers in substantial quantities as a medium to improve the strength and durability of soils and other applications where durability has been a concern.

[0010] Therefore, it is desired to overcome the drawbacks, shortcomings, and limitations associated with existing solutions, and develop a process to improve the life and strength of natural fiber-reinforced soil with MICP.OBJECTS OF THE PRESENT DISCLOSURE

[0011] An object of the present disclosure relates, in general, to reinforcing soil, and more specifically, relates to a method of application of Microbially Induced Calcite Precipitation (MICP) to improve the life and strength of natural fiber and natural fiber-based reinforced soils.

[0012] Another object of the present disclosure is to provide a method that provides effective utilization of highly generated natural fibers like bagasse, coir, jute, etc., ensuring high durability to the reinforced soil.

[0013] Another object of the present disclosure is to provide a method that explores the usability of natural fibers like bagasse, coir, jute, etc., highly generated wastes, in the MICP process as a carbon source.

[0014] Another object of the present disclosure is to provide a method that effects the biodegradability of natural fibers is also being compensated using MICP.

[0015] Another object of the present disclosure is to provide a method that uses natural fiber with MICP to account for strength as well as biodegradation.

[0016] Another object of the present disclosure is to provide a method that uses agricultural waste fiber in the process of soil reinforcement combined with MICP.

[0017] Another object of the present disclosure is to provide a method that suggests the use of heavily generated natural waste fibers with MICP to mix with soil to improve the mechanical properties of the soil mix.

[0018] Another object of the present disclosure is to avoid the use of industrial urea for the MICP process, which makes the MICP more feasible and applicable in large area.

[0019] Another object of the present disclosure is to provide a method that concentrates on the massive utilization of natural fibers with enhanced life of the structure.

[0020] Another object of the present disclosure is to provide a method that points towards an environment-friendly solution for the disposal of natural fibers rather than burning it into ashes which causes severe damage to the environment and society.

[0021] Another object of the present disclosure is to provide a method for the construction of massive earthworks and fills using natural fiber reinforcements, eco-friendly and economical.

[0022] Another object of the present disclosure is to provide a method resulting in the conservation of natural minerals and soil resources, which leads to a sustainable construction practice.

[0023] Yet another object of the present disclosure is to provide a method that explores the applicability of coating the microbial-nutrient solution with the fiber and then mixing the treated fiber with soil to obtain a uniform pattern for the mix.SUMMARY

[0024] The present disclosure relates, in general, to a reinforcing soil, and more specifically, relates to a method of application of MICP to improve the life of natural fiber- reinforced soils. The main objective of the present disclosure is to overcome the drawbacks, limitations, and shortcomings of the existing method and solution, by providing the use ofMicrobially Induced Calcite Precipitation (MICP) in improving the life of natural fiber- reinforced soil. MICP is a technique in which bacteria with specific properties such as denitrifying or ureolytic bacteria help in forming insoluble calcium carbonate. Natural fibers, which are rich in carbon content act as a carbon source in the MICP process, which eventually converts the fiber into insoluble calcium carbonate. This may fill the voids created in the soil fiber matrix during the degradation of reinforcement. Thus, the soil may achieve an initial strength with fiber reinforcement and later during the degradation of fiber, the calcite precipitated soil maintains / enhances its strength. The formation of calcium carbonate not only restricts the loosening of geomaterial but also binds the soil particles. Thus, the degradation process of natural fibers is gainfully utilized to compensate for strength reduction. The present disclosure may result in a sustainable solution to improve the life of natural fiber- reinforced soil. Also, the present disclosure is a breakthrough which contributes to various other innovations in different fields of study.

[0025] The present disclosure improves the life and strength of structures reinforced with natural fibers and products of natural fibers, helping in its massive utilization. Utilizing natural fibers, adopting this methodology helps solve the issues of excessive deposition of natural fibrous materials and it’s burning it into ashes. This also helps in the conservation of natural resources as well. Further, the methodology can also help enhance the strength of soils, by adding a cementation effect.

[0026] The methodology suggests using carbon-rich natural fibers as a substitute for industrial urea in the MICP process. This can be applied in constructing massive structures and maintaining strength standards even after the natural degradation period of natural fibers. The calcite formed during the MICP process also acts as a cementing material to enhance the strength of earth structures and fills. The earth structures are selected from road embankments, rail embankments, slopes, earthfills and the like. The present disclosure provides a method of incorporation of natural fiber waste material in large earthworks, the method includes providing replacement or a reinforcing material of massive quantity to the soil of earth structures and earth fills using specialized equipment. The specialized equipment selected from mixers, compaction rollers and any combination thereof. The earth structures are selected from road embankments, rail embankments, slopes, earthfills and any combination thereof. In an aspect, the natural fibers are used in various applications including geotechnical applications with high durability, thereby consuming huge quantity of natural wastes, conserving natural resources.

[0027] The present disclosure provides a method for enhancing natural fiber-reinforced earth structures by utilizing the carbon present in natural fibers as a carbon source for Microbially Induced Calcite Precipitation (MICP). The method comprises preparing a bacterial solution in a container, substituting urea with natural fibers as the carbon source in the MICP process, treating the natural fibers with the bacterial solution to facilitate microbial activity, adding a calcium chloride solution to the treated natural fibers to initiate the precipitation of calcium carbonate, and depositing the formed calcium carbonate on the surface of the natural fibers. The calcium carbonate strengthens the natural fibers and enhances their reinforcement properties when incorporated into soil. Furthermore, the method applies MICP with a natural carbon source to enhance the shear strength of natural soil and increase cyclic resistance and liquefaction strength, providing an effective liquefaction mitigation measure. The natural fibers used as a carbon source material may comprise natural waste materials, including but not limited to bagasse fibers, areca, coir, jute, or any combination thereof. The natural fibers may be used in various forms, such as random discrete fibers, sheets, mats, or layers. Additionally, the method enhances the shear strength of the soil with aging and is applicable to earth structures such as road embankments, rail embankments, slopes, structural fills, or any combination thereof.

[0028] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The following drawings form part of the present specification and are included to further illustrate aspects of the present disclosure. The disclosure may be better understood by reference to the drawings in combination with the detailed description of the specific embodiments presented herein.

[0030] FIG. 1 illustrates an exemplary application of Microbially induced Calcite Precipitation (MICP) to improve the life of natural fiber-reinforced soil, in accordance with an embodiment of the present disclosure.

[0031] FIG. 2 illustrates an exemplary application of Microbially induced Calcite Precipitation (MICP) to improve the life of natural fiber-reinforced soil using the natural fiber and urea as the carbon source, in accordance with an embodiment of the present disclosure.

[0032] FIG. 3 illustrates an exemplary method of application of MICP to improve the life of natural fiber-reinforced soils, in accordance with an embodiment of the present disclosure.

[0033] FIG. 4 illustrates an exemplary method of application of MICP with natural fiber using the natural fiber and urea as the carbon source, in accordance with an embodiment of the present disclosure.

[0034] FIG. 5A to 5C illustrate images of failures in earth structures and fills, in accordance with an embodiment of the present disclosure.

[0035] FIG. 6 shows the visual inspection of different natural fibers treated with MICP using the natural fiber as carbon source, in accordance with an embodiment of the present disclosure.

[0036] FIG. 7A illustrates the SEM and EDAX mapping of areca fiber, in accordance with an embodiment of the present disclosure.

[0037] FIG. 7B illustrates the SEM and EDAX mapping of bagasse fiber, in accordance with an embodiment of the present disclosure.

[0038] FIG. 7C illustrates the SEM and EDAX mapping of coir fiber, in accordance with an embodiment of the present disclosure.

[0039] FIG. 7D illustrates the SEM and EDAX mapping of jute fiber, in accordance with an embodiment of the present disclosure.

[0040] FIG. 8 illustrates the behaviour of reinforced soil specimens with different natural fibers with and without MICP after 7 days, in accordance with an embodiment of the present disclosure: (a) stress-strain plots and (b) volumetric-strain plots.

[0041] FIG. 9 illustrate the response of bagasse reinforced soil specimens with and without MICP after 7, 14, 21, 28 days, in accordance with an embodiment of the present disclosure: (a) stress-strain plots and (b) volumetric-strain plots.

[0042] FIG. 10 illustrate peak strength for different fibers with and without MICP, in accordance with an embodiment of the present disclosure.

[0043] FIG. 11 illustrate variation of peak strength of bagasse fiber reinforced soil tested after 7, 14, 21, 28 days with and without MICP, in accordance with an embodiment of the present disclosure.DETAILED DESCRIPTION

[0044] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearlycommunicate the disclosure. If the specification states a component or feature “may”, “can”, “could”, or “might” be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.

[0045] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.

[0046] The present disclosure relates, in general, to reinforcing soil, and more specifically, relates to a method of application of MICP to improve the life of bagasse- reinforced and other natural fiber-reinforced soil The present disclosure provides a method for enhancing natural fiber-reinforced earth structures by utilizing the carbon present in natural fibers as a carbon source for Microbially Induced Calcite Precipitation (MICP). The method comprises preparing a bacterial solution in a container, substituting urea with natural fibers as the carbon source in the MICP process, treating the natural fibers with the bacterial solution to facilitate microbial activity, adding a calcium chloride solution to the treated natural fibers to initiate the precipitation of calcium carbonate, and depositing the formed calcium carbonate on the surface of the natural fibers. The calcium carbonate strengthens the natural fibers and enhances their reinforcement properties when incorporated into soil. Furthermore, the method applies MICP with a natural carbon source to enhance the shear strength of natural soil and increase cyclic resistance and liquefaction strength, providing an effective liquefaction mitigation measure. The natural fibers used as a carbon source material may comprise natural waste materials, including but not limited to bagasse fibers, areca, coir, jute, or any combination thereof. The natural fibers may be used in various forms, such as random discrete fibers, sheets, mats, or layers. Additionally, the method enhances the shear strength of the soil with aging and is applicable to earth structures such as road embankments, rail embankments, slopes, structural fills, or any combination thereof.

[0047] The present disclosure uses areca, bagasse, coir and jute as natural fiber, which can be taken forward with other natural fibers. The natural fiber is treated with a ureolytic bacteria in the presence of a calcium source, and produces insoluble calcium carbonate. Sporosarcina pasteurii, Escherichia coli, Bacillus megaterium, B. pasteurii and the like are some of the commonly used urease bacteria in MICP, while Calcium chloride is the calcium source. The present disclosure can be described in enabling detail in the following examples, which may represent more than one embodiment of the present disclosure.

[0048] The advantages achieved by the process of the present disclosure can be clear from the embodiments provided herein. The method provides effective utilization of highly generated natural fibers such as bagasse, coir, etc. ensuring high durability to the reinforced soil. The method explores the usability of natural fibers, a highly generated waste, in the MICP process as a carbon source. The method effects biodegradability of natural fibers are also being compensated using MICP. The method uses natural fiber with MICP to account for strength as well as biodegradation.

[0049] The method uses agricultural waste fiber in the process of soil reinforcement combined with MICP. The method suggests the use of heavily generated natural waste fibers with MICP to mix with soil to improve the mechanical properties of the soil mix. Further, the method explores the applicability of coating the microbial-nutrient solution with the fiber and then mixing the treated fiber with sand to obtain a uniform pattern for the mix. The description of terms and features related to the present disclosure shall be clear from the embodiments that are illustrated and described; however, the invention is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions, and equivalents of the embodiments are possible within the scope of the present disclosure. Additionally, the invention can include other embodiments that are within the scope of the claims but are not described in detail with respect to the following description.

[0050] FIG. 1 illustrates an exemplary application of Microbially induced Calcite Precipitation (MICP) to improve the life of natural fiber-reinforced soil, in accordance with an embodiment of the present disclosure.

[0051] Referring to FIG. 1, the present disclosure develops a methodology with the application of Microbially induced Calcite Precipitation (MICP) to improve the life of natural fiber-reinforced soil. The continuous strength imparted by the insoluble calcium carbonate produced by MICP is used to compensate for the strength reduction due to the biodegradation of natural fibers. Initially, the natural fiber may provide sufficient strength to the reinforced soil, later it is taken over by the MI CP -produced calcium carbonate. Also, the produced calcite during MICP helps bind the soil particles, providing additional strength to the aged, reinforced soil.

[0052] The system 100 can include the preparation of nutrient solution (also referred to as bacterial solution, herein) in a container 102. The nutrient solution with culture media is prepared with microbes, and calcium chloride is prepared as solution in water (i.e., calcium source). The fiber, as presented in the example is selected from areca, bagasse, coir and jute. As can be appreciated, the present disclosure may not be limited to these filler materials butmay be extended to other filler materials such as residues of com, straws of grasses and husks of wheat grains, com, rice, and barley. The fiber is soaked in nutrient solution and is mixed with the calcium choloride and soil when required.

[0053] The application of MICP in the soil is a new methodology to improve the strength of soil. The researchers have also used synthetic fibers to add additional strength to the MICP-treated soil. The method increases the life of reinforced soil by producing insoluble calcium carbonate by degrading the natural fiber.

[0054] The container 102 is provided for the preparation of a bacterial solution, wherein natural fiber is employed as a carbon donor in the MICP process. The bacterial solution is applied to the natural fiber to promote microbial activity. Subsequently, a calcium chloride solution is introduced to the treated natural fiber, initiating calcium carbonate precipitation, with the calcium carbonate being deposited on the surface of the natural fiber. This deposition of calcium carbonate fortifies the natural fiber and improves its reinforcement properties when integrated into soil.

[0055] FIG. 2 illustrates an exemplary application of Microbially induced Calcite Precipitation (MICP) to improve the life of natural fiber-reinforced soil, in accordance with an embodiment of the present disclosure in the presence of urea.

[0056] Referring to FIG. 2, the present disclosure develops a methodology with the application of Microbially induced Calcite Precipitation (MICP) to improve the life of natural fiber-reinforced soil. The continuous strength imparted by the insoluble calcium carbonate produced by MICP is used with urea to compensate for the strength reduction due to the biodegradation of natural fibers. Initially, the natural fiber may provide sufficient strength to the reinforced soil, later it is taken over by the MICP-produced calcium carbonate. Also, the produced calcite during MICP helps bind the soil particles, providing additional strength to the aged, reinforced soil.

[0057] The system 200 can include the preparation of nutrient solution (also referred to as bacterial solution, herein) in a container 202. The nutrient solution with culture media is prepared with microbes, and calcium chloride is prepared as solution in water (i.e., calcium source). The fiber, as presented in the example is selected from areca, bagasse, coir and jute. As can be appreciated, the present disclosure may not be limited to these filler materials but may be extended to other filler materials such as residues of com, straws of grasses and husks of wheat grains, com, rice, and barley. The fiber is soaked in nutrient solution and is mixed with urea, the calcium choloride and soil (when required). Adding a small amount of urea can increase the amount of produced calcium carbonate.

[0058] The application of MICP in the soil is a new methodology to improve the strength of soil. The researchers have also used synthetic fibers to add additional strength to the MICP-treated soil. The proposed method increases the life of natural fiber reinforced soil by producing insoluble calcium carbonate by degrading the natural fiber.

[0059] The container 202 is provided for the preparation of a bacterial solution, wherein urea is additionally employed as a carbon donor in the MICP process. The bacterial solution is applied to the natural fiber to promote microbial activity. Subsequently, urea and a calcium chloride solution is introduced to the treated natural fiber, initiating calcium carbonate precipitation, with the calcium carbonate being deposited on the surface of the natural fiber. This deposition of calcium carbonate fortifies the natural fiber and improves its reinforcement properties and durability when integrated into soil.

[0060] The present disclosure would receive huge demand from the construction industry. The methodology directly solves the problem of degradation of natural fibers, which can be directly used in various infrastructural activities. The methodology improves the strength properties of soil as well. Further, the common beneficiaries of the proposed disclosure may be the government and thereby the common citizens of the nation, by an economic and environment-friendly construction strategy and massive waste utilization.

[0061] FIG. 3 illustrates an exemplary method for improving the strength and longevity of natural fiber-reinforced soil, in accordance with an embodiment of the present disclosure.

[0062] The method for improving the strength and longevity of natural fiber-reinforced soil, the method includes at block 302, preparing bacterial solution in a container, at block 304 replacing urea with a natural fiber as a carbon source in a microbial -induced calcium carbonate precipitation (MICP) process. A block 306, treating the natural fiber with a bacterial solution to facilitate microbial activity. At block 308, adding calcium chloride to the treated natural fiber to initiate the precipitation of calcium carbonate. At block 310, depositing the formed calcium carbonate on the surface of the natural fibers, wherein the calcium carbonate strengthens the fibers and enhances their reinforcement properties when incorporated into soil at block 312.

[0063] FIG. 4 illustrates an exemplary method of application of MICP to improve the life of natural fiber-reinforced soils, in accordance with an embodiment of the present disclosure.

[0064] Referring to FIG. 4, the method 400 includes at block 402, preparing of nutrient solution, where the nutrient solution with culture media is prepared with microbes. The fiber is treated 404 with the nutrient solution and mixed at block 406 with urea and calciumchloride. Treating the fiber using the prepared solution. The fiber is selected from areca, bagasse, coir and jute fiber. At block 408, mixing of the fiber with soil. The treated fiber is mixed with soil, and initiates the CaCCf production consuming fibers around the length of fiber. The treated natural fiber can be used for construction, ensuring long life of the structure.

[0065] Thus, the present invention overcomes the drawbacks, shortcomings, and limitations associated with existing solutions, and provides a method that provides effective utilization of highly generated natural fibers such as bagasse, ensuring high durability to the reinforced soil. The method explores the usability of natural fiber bagasse, a highly generated waste, in the MICP process as a carbon source. The method effects biodegradability of natural fibers are also being compensated using MICP. The method uses natural fiber with MICP to account for strength as well as biodegradation.

[0066] The method uses agricultural waste fiber in the process of soil reinforcement combined with MICP. The method suggests the use of heavily generated natural waste fibers with MICP to mix with soil to improve the mechanical properties of the soil mix. Further, the method explores the applicability of coating the microbial-nutrient solution with the fiber and then mixing the treated fiber with sand to obtain a uniform pattern for the mix. The present disclosure receives huge demand from the construction industry. The methodology directly solves the problem of degradation of natural fibers, which can be directly used in various infrastructural activities. The methodology improves the strength properties of soil as well. The common beneficiaries of the proposed patent may be the government and thereby the common citizens of the nation, through an economic and environment-friendly construction strategy and massive waste utilization.

[0067] This can be applied in high earth structures and fills ensuring durability and strength. Further, the earth structures 500 are selected from road embankments, rail embankments, slopes, reinforced slopes, reinforced earth walls, backfills, foundation soils, structural filles, and the like shown in FIG. 5A to 5C respectively.

[0068] Thus, the present invention overcomes the drawbacks, shortcomings, and limitations associated with existing applications of natural fiber, and provides a method of using natural fibers with higher service life. The method results in improved soil strengthening and construction of massive earthworks and fills, eco-friendly and economical. The present invention provides a method for the effective utilization of highly generated natural fibers, such as bagasse, coir, etc. to ensure high durability in reinforced soil. This method explores the usability of natural fibers, a commonly produced waste material, in theMicrobially Induced Calcite Precipitation (MICP) process as a carbon source. Additionally, the invention addresses the biodegradability of natural fibers, which is mitigated through the MICP process. By incorporating MICP with natural fibers, the method enhances both the strength and biodegradation resistance of the soil. Furthermore, the invention utilizes agricultural waste fibers in soil reinforcement, combined with MICP, to improve the mechanical properties of soil mixtures. The method suggests coating the microbial-nutrient solution onto the fiber and then mixing the treated fiber with sand to achieve a uniform pattern in the soil mix. This invention promotes the use of natural waste materials as an effective ground improvement solution, facilitating large-scale utilization as a partial replacement for soil. It also presents a conservation approach, wherein natural fibers are utilized as a soil substitute without compromising the natural strength of the soil over time. The method offers an environmentally friendly solution for disposing of natural fibers, avoiding harmful practices like burning, which cause environmental and societal damage. The invention results in improved soil strengthening, enabling the construction of large-scale earthworks and fills in an eco-friendly and economical manner. Moreover, it enhances the liquefaction resistance of soil when used as a partial replacement and reinforcement, thereby preserving natural resources through the extensive use of natural waste fibers as a soil substitute.

[0069] FIG. 5A to 5C illustrate images of failures in earth structures and fills, in accordance with an embodiment of the present disclosure. These illustrations showcase specific scenarios where the integrity of such structures is compromised, offering visual insights into potential points of failure and the conditions that lead to structural weaknesses.

[0070] FIG. 6 illustrates the visual examination of the presence of calcite formation, when natural fiber is used as a carbon source. The examination is done for four different fibers allowing 7 days of aging. Evidently, all the fibers produced a white precipitation, which is calcium carbonate.

[0071] A detailed examination of each sample is conducted using Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Analysis (ED AX), as depicted in FIG. 7A to 7D. Referring to FIG. 7A, embodiment 700 illustrates the SEM image of areca fiber with calcite deposition during Microbially Induced Calcite Precipitation (MICP). Embodiment 702 presents the mapping of carbon, while embodiment 704 demonstrates the element distribution in the sample, revealing the presence of carbon (C), calcium (Ca), and oxygen (O). Embodiment 706 shows an overlaying mapping of calcium, carbon, and oxygen, with theregion in embodiment 700 indicating the presence of calcite distinctly displaying the presence of Ca, C, and O.

[0072] Referring to FIG. 7B, embodiment 708 illustrates the SEM image of bagasse fiber with calcite deposition during Microbially Induced Calcite Precipitation (MICP). Embodiment 710 presents the mapping of carbon, while embodiment 712 demonstrates the element distribution in the sample, indicating the presence of carbon (C), calcium (Ca), and oxygen (O). Embodiment 714 displays an overlaying mapping of calcium, carbon, and oxygen, with the region in embodiment 708 exhibiting calcite clearly showing the presence of Ca, C, and O.

[0073] Referring to FIG. 7C, embodiment 716 illustrates the SEM image of coir fiber with calcite deposition during Microbially Induced Calcite Precipitation (MICP). Embodiment 718 presents the mapping of carbon, while embodiment 720 demonstrates the element distribution in the sample, revealing the presence of carbon (C), calcium (Ca), and oxygen (O). Embodiment 722 displays an overlaying mapping of calcium, carbon, and oxygen, with the region in embodiment 716 exhibiting calcite clearly showing the presence of Ca, C, and O.

[0074] Referring to FIG. 7D, embodiment 724 illustrates the SEM image of jute fiber with calcite deposition during Microbially Induced Calcite Precipitation (MICP). Embodiment 726 presents the mapping of carbon, while embodiment 728 demonstrates the element distribution in the sample, indicating the presence of carbon (C), calcium (Ca), and oxygen (O). Embodiment 730 displays an overlaying mapping of calcium, carbon, and oxygen, with the region in embodiment 724 exhibiting calcite clearly showing the presence of Ca, C, and O.A11 the above results evidently show the formation of calcium carbonate, when natural fiber is used as a carbon source in MICP. This directly reflects on the life of the natural fiber reinforced soil.

[0075] The proposed disclosure receives huge demand from the construction industry. It is directly applied to problems of social importance like soil improvement as well as waste management. The proposed methodology can be applied to increase the static and dynamic shear strength, liquefaction resistance of soil, static and seismic slope stability, and the like.

[0076] The common beneficiaries of the proposed disclosure include engineers and infrastructure industry, which helps them designing structures with good strength and life without the use of huge quantity of non-renewable resources. The application offers an economic and environment-friendly construction strategy and massive waste utilization of natural fibers.EXPERIMENTAL RESULTS:

[0077] The series of experiments consists of two different phases. The first one is to prove the hypothesis of formation of calcite using MICP with natural fiber as a carbon source. The second series is its application. Although, the application selected here is as a soil reinforcement, this can be extended to any application.Materials

[0078] The soil utilized in this research originates from the Solani riverbed located in India and is denoted as Solani sand. Predominantly, about 97% of the sand is composed of fine particles, while the remaining segment falls within the spectrum of coarse and medium sand, silt, and clay. The sample's void ratio ranges from 0.53 to 0.87, encompassing the minimum and maximum values, respectively. Additionally, the sand's specific gravity is measured at 2.64.

[0079] Four different natural fibrous materials are selected for verifying the hypothesis: Areca, bagasse, coir and jute fiber.Areca fiber

[0080] Areca, commonly known as the betel nut palm, is a species found extensively across the tropical regions of the Pacific, Asia, and parts of East Africa. In India, areca is predominantly grown in Karnataka, Kerala, and Assam. For this study, areca fibers were sourced from Kerala, India. The dry, brown areca nut shells were collected for the study, and the fibers were manually extracted from these shells in the laboratory. These fibers were used to reinforce soil and soil beds and have shown significant improvement in strength in the past.Bagasse fiber

[0081] Bagasse fiber, derived from sugarcane residue, is an effective and sustainable material for soil improvement. Its fibrous nature provides excellent reinforcement, enhancing the shear strength and load-bearing capacity of the soil. Lightweight, biodegradable, and abundant, bagasse fiber is a cost-effective option for soil stabilization. When mixed with soil, it significantly improves strength and contributes to a better soil structure. Utilizing bagasse fiber in construction promotes sustainable practices by recycling agricultural waste and minimizing environmental impact. Its natural properties make it an ideal choice for eco- friendly soil reinforcement projects.Coir fiber

[0082] Coir, derived from the husk of coconuts, is an eco-friendly and sustainable material used for soil improvement. Its natural fibers are strong, durable, and resistant toroting, making it ideal for reinforcing soil. Coir enhances soil stability, reduces erosion, and improves water retention. When mixed with soil, it increases shear strength and load-bearing capacity, making it suitable for construction and landscaping projects. Its availability and cost-effectiveness further make it a viable option for soil reinforcement, contributing to sustainable development and ecological conservation efforts. Coir has been used in the past to improve soil strength, showing significant strength improvements.Jute fiber

[0083] Jute is an affordable and widely available material. Jute fibers can withstand greater strains compared to other fibers. Although jute is inexpensive and efficient, its extensive use is hindered by its high moisture absorption, which can be mitigated by treating it with certain lubricants. The advantages of jute fiber include its low cost, atainable specific strength, low density, lightweight, ease of availability, and recyclability. Jute has been used in the past to improve soil strength, showing significant strength improvements.Methodology and ExperimentsBacterial culture

[0084] The urease-producing bacterium S. pasteurii (also known as Bacillus pasteurii), collected from the National Chemical Laboratory in Pune. The bacteria were grown and maintained in a lab-prepared NH4-YE medium, which consists of 20 g / L of yeast extract, 10 g / L of (NH4)2SO4, 20 g / L of agar for solid media, and a 0.13 M Tris buffer with a pH of 9.0. In this medium, the bacteria use (NH4)2SO4as a nitrogen source and yeast extract as a nutritional resource, providing vitamins, minerals, and amino acids for cell growth. The pure bacterial strain received in a glass ampoule was transferred to NH4-YE solid media and incubated in sterile aerobic conditions at 30°C for 48-72 hours to allow colony growth. The colonies were then transferred to NH4-YE broth and incubated with shaking at 30°C for 12- 24 hours until reaching the desired optical density at 600 nm (OD60Q). The bacterial cells were harvested by centrifuging at 8,000 rpm for 20 minutes at 4°C. The supernatant was discarded, and the bacteria were resuspended, washed with a saline solution (0.85% NaCl), and stored at 4°C until used in experiments. To promote the bacterial activities that lead to calcium carbonate precipitation, natural fibers were used as a carbon source, and CaCl2can be used as a calcium source.Specimen preparationSpecimen Setl

[0085] The specimen set 1 is prepared to see and understand the proposed hypothesis and formation of calcite.

[0086] The fibers were initially soaked in bacterial solution and transferred to transparent test tubes and flask. CaCT is then added to the test tubes and flask and kept for aging.Specimen Set 2

[0087] The specimen set 2 is prepared to understand the efficiency of developed technique in soil strength applications.

[0088] The fiber is soaked in the bacterial solution for 30 minutes prior to the specimen preparation. The soaked fibers are mixed with sand and CaCT with fiber content 0.25%. The mix is then transferred to the mould and the cylindrical specimen is prepared. The prepared specimen is extracted from the mould and covered with punctured plastic sheets. These punchers in the sheets helps the specimen to take additional CaC solution and moisture from the outside environment and maintain the moisture of the specimen for bacterial life.

[0089] Control specimens were also prepared in the same manner without soaking the fiber and application of CaCT.

[0090] All the prepared specimens were kept inside a chamber. The complete chamber can be set to maintain a moist environment. Frequent wet dry cycles were applied to all the specimens to expedite the process of degradation. The MICP treated specimens were sprayed with CaCT at regular intervals.Results and DiscussionsVisual Examination of presence of calcite

[0091] The specimens prepared as specimen set was taken after 7 days for visual examination. The presence of calcite formation was evidently visible in the test tubes and flask for all the fibers as shown in in FIG. 6.Micro examinations of the presence of calcite

[0092] To confirm the presence of presence of calcite, Scanning Electron microscopy, Energy Dispersive X-ray Spectroscopy is carried out. As clearly seen from FIG. 7A to 7D all fibers are found with the presence of C, Ca and O confirming the presence of CaCXX. The figure also illustrates the mapping of different elements. The peaks in the figures show the presence of the elements.Monotonic strength of natural fiber reinforced sands

[0093] Monotonic triaxial tests demonstrate the behavior of specimens at different conditions. The experimental results are illustrated in terms of deviatoric stress, axial strain, and volumetric strain of the specimens prepared with different fibers.

[0094] The required experimental tests were conducted using a triaxial system supported by a hydraulic actuator for precise loading. Since all the earth structures may be compacted well enough to make in dense, soil bagasse mixes for testing were also prepared in a dense state.

[0095] The deviatoric stress versus axial strain of all the specimens with different fibers after 7 days is shown in FIG. 8. As evident from the plot, the MICP treated fiber reinforced specimens show a clear enhancement in the strength of the soil as compared to the untreated fibers. This is due to the presence of produced calcite.The deviatoric stress versus axial strain of bagasse reinforced specimens with different fibers after 7, 14, 21, 28 days of aging is shown in FIG. 9. As evident from the plot, the MICP treated fiber reinforced specimens show a clear enhancement in the strength of the soil with aging as compared to the untreated fibers. In fact, untreated fiber specimens showed strength degradation with aging due to biodegradation of natural fibers. The effect of cementation achieved through interaction of carbon present in the natural fibers and CaCT increases with age of the structure.

[0096] For better understanding, the peak deviator stress observed for different fiber specimens is shown in FIG. 10 and Table 1. It is observed that, irrespective of fiber type the peak deviator stress increases, when the fibers are treated with MICP at 7thday.Table 1

[0097] To further understand the effect of aging, FIG. 11 and Table 2 is shown. The peak deviator stress of MICP treated bagasse reinforced specimen show an increase in strength with number of aging days, However, under the continuous dry wet cycles, the untreated fiber reinforced specimens start experiencing a drop in strength due the degradation of fibers.Table 2

[0098] It will be apparent to those skilled in the art that the method 300 of the disclosure may be provided using some or all of the mentioned features and components without departing from the scope of the present disclosure. While various embodiments of the present disclosure have been illustrated and described herein, it will be clear that the disclosure is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions, and equivalents will be apparent to those skilled in the art, without departing from the spirit and scope of the disclosure, as described in the claims.ADVANTAGES OF THE PRESENT INVENTION

[0099] The present invention provides a method that provides effective utilization of highly generated natural fibers like areca, bagasse, coir, jute, etc. ensuring high durability to the reinforced soil.

[0100] The present invention provides a method that explores the usability of natural fiber bagasse, a highly generated waste, in the MICP process as a carbon source.

[0101] The present invention provides a method that effects the biodegradability of natural fibers that are also being compensated using MICP.

[0102] The present invention provides a method that uses natural fiber with MICP to account for strength as well as biodegradation.

[0103] The present invention provides a method that uses agricultural waste fiber in the process of soil reinforcement combined with MICP.

[0104] The present invention provides a method that suggests the use of heavily generated natural waste fibers with MICP to mix with soil to improve the mechanical properties of the soil mix.

[0105] The present invention provides a method that explores the applicability of coating the microbial-nutrient solution with the fiber and then mixing the treated fiber with sand to obtain a uniform pattern for the mix.

[0106] The present invention also promotes usage of natural waste material as an effective solution for ground improvement which also helps in large scale utilization as a partial replacement of soil.

[0107] The present invention provides a solution for conservation of natural resources that natural fibers can be utilized as a replacement for the soil.

[0108] The present invention provides a method that also inclusive of the massive utilization of natural fibers without compromising the natural strength of the soil with time.

[0109] The present invention provides a method that points towards an environment- friendly solution for the disposal of natural fibers rather than burning it into ashes which causes severe damage to the environment and society.

[0110] The present invention provides a method that results in improved soil strengthening and the construction of massive earthworks and fills, which is eco-friendly and economical.[oni] The present invention provides a method that results in improved liquefaction resistance of soil, when used as a partial replacement and as a reinforcement.

[0112] The present invention provides a method which helps in preserving the natural resources by using natural waste fibers in huge quantity as a partial replacement to the soil.

Claims

We Claim:

1. A method (300) for enhancing life and strength of natural fiber-reinforced earth structure by utilizing carbon present in natural fiber as a carbon source for microbially induced calcite precipitation (MI CP), the method comprising: preparing (302) a bacterial solution in a container; using (304) the natural fiber as the carbon source in the MICP; treating (306) the natural fiber with the bacterial solution to facilitate microbial activity; adding (308) calcium chloride solution to the treated natural fiber to initiate precipitation of calcium carbonate; and depositing (310) formed calcium carbonate on surface of the natural fiber, wherein the calcium carbonate strengthens the natural fiber and enhances reinforcement properties when incorporated into soil.

2. The method (400) as claimed in claim 1, , the method comprising: preparing (402) the bacterial solution in the container; using the natural fiber and urea as the carbon source in the MICP; treating (404) the natural fiber with the bacterial solution to facilitate microbial activity; adding (406) urea and calcium chloride solution to the treated natural fiber to initiate precipitation of calcium carbonate; and depositing (408) formed calcium carbonate on surface of the natural fiber, wherein the calcium carbonate strengthens the natural fiber and enhances reinforcement properties when incorporated into soil.

3. The method as claimed in claim 1, wherein the MICP is applied with natural carbon source, so as to enhance shear strength of natural soil.

4. The method as claimed in claim 1, wherein the MICP increases cyclic resistance and liquefaction strength, providing an effective liquefaction mitigation measure.

5. The method as claimed in claim 1, wherein the natural fiber is a carbon source material comprises natural waste material.

6. The method as claimed in claim 5, wherein the natural waste material is selected from bagasse fiber, areca, coir, jute, any other natural fiber or combination thereof.

7. The method as claimed in claim 1, wherein the natural fiber used in various forms, the various forms selected from random discrete fibers, sheets, mats, or layers.

8. The method as claimed in claim 1, wherein the shear strength of the soil is enhanced with aging, wherein durability of the natural fiber-reinforced earth structures are enhanced by applying the bacterial solution in combination with the calcium chloride and the urea through sprinkling, injecting, grouting, or any combination thereof9. The method as claimed in claim 1, wherein the earth structures selected from road embankments, rail embankments, slopes, structural fills, and any combination thereof.

10. A system (100) for enhancing life and strength of of natural fiber-reinforced earth structure by utilizing carbon present in natural fiber as a carbon source for microbially induced calcite precipitation (MICP), the system comprising: a container (102) for preparing a bacterial solution; a natural fiber is used as the carbon source in the MICP, wherein the bacterial solution is applied to the natural fiber before or after installation to facilitate microbial activity; and a calcium chloride solution is added to the treated natural fiber to initiate calcium carbonate precipitation, the calcium carbonate is deposited on surface of the natural fiber, wherein the calcium carbonate strengthens the natural fiber and enhances reinforcement properties when incorporated into soil.

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