A METHOD TO IMPROVE SOIL STRENGTH

Abstract

The present invention discloses a method to improve soil strength by adding bitumen coated jute fibers. The present invention further provides a method of coating jute fiber with bitumen and use of strengthened soil in the construction sites. Further, the present invention also provides a comparative result of % CBR values for soil strengthened by using different length of bitumen coated jute fibers .

Specification

Description:A METHOD TO IMPROVE SOIL STRENGTH

FIELD OF THE INVENTION
The present invention relates to the field of civil engineering. In particular, it relates to the field of soil stabilization using jute fibers.

BACKGROUND OF THE INVENTION
Soil stabilization is a very essential part before starting any construction activities. Weak subgrade soils such as clay or silt often face challenges like excessive deformation, low strength, and moisture sensitivity.

Soil stabilization can be performed by employing methods that utilise natural and chemical treatments. The construction cost can be considerably decreased by selecting local materials including local soils for construction of the lower layers of the pavements such as the sub-base course. Naturally available materials are generally preferred to ensure the cost cutting in construction of low-cost road in the view of design and construction. Traditional solutions involve soil stabilization with the help of using chemical additives like lime, cement, etc. or geosynthetics. The biggest hurdle to provide a complete network of road system is the limited finance available to build road by the conventional method.

Hence, there is a need for methods to enhance the strength of soil with subgrade characteristics using low-cost construction techniques to meet the growing demands of road traffic.

OBJECT OF THE INVENTION
The object of the present invention is to provide an efficient method for strengthening the soil subgrade characteristics.

SUMMARY OF THE INVENTION
The present invention discloses a method to stabilize and strengthen soil by mixing bitumen coated jute fibers of specific characteristics.

The bitumen coated jute fiber preparation comprises the steps of:
i. cutting of jute fiber,
ii. coating of jute fibers in a bitumen emulsion bath,
iii. drying the coated jute fiber obtained after step (ii),
iv. curing of jute fibers obtained after step (iii) to achieve full strength of the bitumen coating.

The present invention also discloses various methods and use of jute fibres in subgrade strengthening of soil.

The present invention also discloses the use of strengthened soil prepared by the above method.

BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 depicts CBR Graph with 0% jute fibres.
Figure 2 depicts the graph of CBR values for 15mm jute fiber length with 0.4% jute fibers.
Figure 3 depicts the graph of CBR values for 15mm jute fiber length with 0.8% jute fibers.
Figure 4 depicts the graph of CBR values for 15mm jute fiber length with 1.2% jute fibers.
Figure 5 depicts the graph of CBR values for 30mm jute fiber length with 0.4% jute fibers.
Figure 6 depicts the graph of CBR values for 30mm jute fiber length with 0.8% jute fibers.
Figure 7 depicts the graph of CBR values for 30mm jute fiber length with 1.2% jute fibers.
Figure 8 depicts the comparison graph of CBR values vs % of jute fibers.

DETAILED DESCRIPTION OF THE INVENTION

The present invention discloses a method to stabilize and strengthen soil by mixing bitumen coated jute fibers of specific characteristics. The bitumen coated jute fiber preparation comprises the steps of:
i. cutting of jute fiber,
ii. coating of jute fibers obtained after step (i) in a bitumen emulsion bath,
iii. drying the coated jute fiber obtained after step (ii),
iv. curing of jute fibers obtained after step (iii) to achieve full strength of the bitumen coating.

The method of coating jute fibers with bitumen is briefly explained as follows:
(i) Cutting of jute fiber: Jute fibers are cut into to the fibers of specified lengths using precision cutting tools to ensure uniformity.
(ii) Coating of jute fibers: Jute fibers are immersed in a bitumen emulsion bath at room temperature by ensuring that the fibers are fully submerged and saturated with the emulsion.
(iii) Drying the coated jute fiber: Jute fibers are removed from the bath and hung to air dry in a well-ventilated area. Once the surface is non- tacky to touch, proceed to the next step.
(iv) Curing of jute fibers: Once the surface is non- tacky to touch the coated fiber is placed in a curing chamber set at 20-30 degree C for 22-26 hours to achieve full strength of the bitumen coating.

The present invention also discloses various methods for using jute fibers in soil strengthening. The methods are enlisted as follows:
a. Hybrid Reinforcement with Jute-Geosynthetics
In this method, jute fibers are combined with traditional geosynthetics like geogrids or geotextiles to enhance the stabilization effect. While the geosynthetics provide long-term stability and tensile strength, the jute fibers offer immediate improvement in the soil's mechanical properties. This approach is particularly useful in areas prone to flooding or heavy moisture.
b. Use of Treated Jute Fibers
The natural biodegradability of jute, while beneficial in ecological terms, poses a challenge in the long-term performance of the subgrade. To extend the life of jute fibers, innovative chemical treatments (such as bitumen coating or bio-polymer treatment) can be applied. These treatments slow down the degradation process and provide additional protection against moisture absorption, increasing the fibers' durability.
c. Pre-mixed Jute Fiber-Soil Blends
Another approach is to pre-mix jute fibers with the soil before laying the subgrade. This method ensures an even distribution of fibers and enhances the mechanical interaction between soil particles and fibers. In construction practices, fiber percentages ranging from 0.2% to 1% by dry weight of soil are commonly tested for optimal performance, depending on the soil type and project requirements.
d. Layered Jute Fiber Reinforcement
In this technique, layers of jute fibers are placed within the subgrade at varying depths. This creates a multi-layered reinforcement system, improving the distribution of stresses over a wider area, thus reducing the risk of localized failures. Layered reinforcement is particularly effective in pavements that experience high traffic loads.
e. Incorporation with Green Infrastructure
Integrating jute fiber-reinforced subgrades into green infrastructure projects, such as eco-roads or nature-based urban drainage systems, could offer a sustainable approach to infrastructure development. The biodegradability of jute fits well with concepts like vegetated pavements, where the gradual breakdown of fibers provides organic material that enriches the soil and supports plant growth.

The present invention further discloses the use of jute fibers in subgrade strengthening of soil based on the principle that they improve the shear strength, bearing capacity, and reduce settlement under loading conditions. Jute fibers act as micro-reinforcements, interlocking with soil particles to enhance the load-carrying capacity. By bridging soil particles, they improve the overall stiffness and reduce deformation, preventing rutting and cracking of the pavement.

In high-moisture conditions, subgrades tend to weaken. Jute fibers reduce permeability and increase the water retention capability of the soil, improving the long-term stability of the subgrade. While jute is biodegradable, it retains its tensile strength for a considerable period during construction, providing immediate reinforcement before gradual degradation.

The use of strengthened subgrade soil includes but not limited to construction of roads, pavements, construction of retaining walls, bridge abutments for highways, industrial and mining structures, etc.

ADVANTAGES
Advantages of bitumen coated jute Fiber offers in enhancing the strength of soil subgrade characteristics are given as follows:
• improved shear strength, bearing capacity, and reduced settlement under loading conditions,
• improved overall stiffness and reduced deformation, preventing rutting and cracking of the pavement,
• reduced permeability and increased water retention capability of the soil thereby improving the long-term stability of the subgrade,
• retention in its tensile strength for a considerable period during construction, providing immediate reinforcement before gradual degradation.

EXAMPLES
Example 1: Standard Proctor Test:

The Standard Proctor Test as approved by American Society for Testing and Materials (ASTM) D968 provides a standardized method for determining the moisture-density relationship of soils. A representative soil sample was collected from the construction site and it was ensured that the sample represents the soil being tested and is sufficient in quantity for the desired number of tests. A clean and dry compaction mold ensuring that there is no debris or moisture present , was prepared. The inner volume of the mold (V mold) was measured and prepared. A portion of the soil was taken and large aggregates were broken into smaller particles. The soil was thoroughly mixed to achieve the uniform consistency. The soil sample was then divided into several portions, each with different moisture contents. The test was started with the dry soil and gradually the moisture content was subsequently increased for tests. The moisture content range that includes both lower and higher expected values was used.

Procedure: One part of the soil sample was taken and its weight (W2) using a balance was determined. A calculated quantity of water was added to the soil sample to reach the desired moisture content. The soil was then compacted using a standard compaction effort (e.g., using a rammer). The volume of the compaction mold was measured to calculate the Maximum Dry Density (MDD). The moisture content corresponding to the MDD is the OMC. The OMC refers to the moisture level at which soil achieves its maximum dry density during compaction. In other words, it is the ideal water content for compacting soil to achieve the highest possible density. Soil must be at the right density to support infrastructure, but this rarely occurs naturally. Compaction is necessary, and it requires water. OMC ensures that soil particles stick together during compaction, resulting in a strong, long-lasting foundation.

Table 1 Optimum Moisture Content (OMC)
Determination No. Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Sample 7
Water added (%) 14 16 18 20 22 24 26
Mass of empty mould (gm) 5620 5620 5620 5620 5620 5620 5620
Mass of mould + compacted soil (gm) 9320 9400 9480 9525 9760 9795 9738
Mass of compacted soil (gm) 3660 3780 3680 3905 4140 4175 4118
Bulk density (gm/cc) 3.66 3.78 3.68 3.90 4.14 4.17 4.118
Mass of empty cylinder (gm) 14.1 13.8 13.9 14.2 14 14.3 13.7
Mass of container + wet soil (gm) 39.9 40.4 44.8 39.6 40.8 41.7 42.9
Mass of container + dry soil (gm) 36.2 37.1 40.9 37.2 36.3 37.5 40.2

Example 2: Natural water content
The natural moisture content, also known as the natural water content, provides essential information about the water present in the soil under its natural conditions.
The Apparatus Required to perform the experiments includes a non-corrodible container, a digital weight machine with an accuracy of 0.04% of mass of sample, an electric oven to maintain the temperature between 1050 C to 1100 C.
The container was cleaned and dried and weighed (W1). A specimen of the sample was added in the container and weighed (W2). The container was placed in the hot air oven at a temperature of 110o ± 5o C and allowed to dry for a period varying with the type of soil, more preferably 24 hours. The final constant weight (W3) of the container with dried soil sample was recorded.
Table 2 Natural moisture content
S.No. Content Sample 1 Sample 2 Sample 3
1 Mass of container (M1) gm 29 23.5 29
2 Mass of container and wet soil (M2) gm 89 84.5 110.5
3 Mass of container and dry soil (M3)gm 70 67.5 88.5
4 Mass of soil (M3-M1) gm 51 44 59.5
5 Mass of soil (M2-M3) gm 19 17 22
6 Water content in percent W= (M2-M3)/(M3-M1) *100 (in %) 0.37 0.38 0.37

Example 3: Preparation And Characterization Of Soil Samples
Materials required: Natural soil (specify types , e.g. , silty clay, sandy loam, etc.), jute fibers with diameter of 4mm and 8 mm, jute fibers cut to lengths of 15 mm and 30 mm, bitumen emulsion for coating fibers. Digital weighing scale with an accuracy of 0.01gm, mixing tools (e.g., spatula, mixing bowl, stirrer), molds for sample shaping (specify dimensions), curing chamber with controlled temperature and humidity.

3.1. Preparation Of Bitumen- Coated Jute Fibers
Cutting: Jute fibers were cut into to the fibers of specified lengths using precision cutting tools to ensure uniformity.
Coating: Jute fibers were immersed in a bitumen emulsion bath at room temperature. It was ensured that the fibers were fully submerged and saturated with the emulsion.
Drying: After coating the fibers were removed from the bath and hung to air dry in a well-ventilated area.
Curing: Once the surface was non- tacky to touch, the dried jute fibers were placed in a curing chamber set at 25 0 C for 24 hours to achieve full strength of the bitumen coating.

Results and Discussions: It is observed that there is remarkable increment in properties of soil according to the percentage of jute fiber by the weight of soil. But a nominal percentage of jute fiber would improve the various properties of soil. As addition of jute fiber can increase the stress bearing capacity of soil significantly.

Example 4: California Bearing Ratio (CBR)
California Bearing Ratio (CBR) is expressed as the percentage of stress a soil specimen can resist for a certain amount of penetration relative to the stress value that a standard soil could resist. Essentially, it serves as an indicator of the soil's strength. It is used to measure the strength of subgrade soil was conducted. This test is essential for evaluating the relative strength of a soil specimen compared to a standard sample.

The soil specimen was sieved using a ¾-inch (19 mm) sieve. The soil was mixed with water content equal to the optimum water content determined through light or heavy compaction tests. A rigid metal cylinder (mold) was filled with the soil specimen. The soil in three equal layers was compacted using a 5.5 lb hammer (56 blows per layer). After compaction, the top and bottom surfaces of the sample were trimmed to level of the soil surface. The mold (filled with the compacted soil) was mixed in water for a specified period. The mold was then attached to a loading machine having a penetration measuring device (dial indicator) for accurate measurements, capable of applying compressive force to the piston. A metal piston with a diameter of 1.954 ± 0.005 inches (49.63 ± 0.13 mm) and a length of not less than 4 inches (101.6 mm) was used. The load on the piston was gradually applied causing it to penetrate through the soil. The load values corresponding to specific penetrations were recorded. A proving ring to measure the load applied to the surface was attached.

Table 5 CBR values
S. no. Fiber length (mm) % of Fiber by dry weight of soil CBR% Increment in CBR value
1 15 0 5.67 0
2 0.4 5.89 0.22
3 0.8 7.2 1.31
4 1.2 16.59 10.7
5 30 0 5.67 0
6 0.4 11.13 5.24
7 0.8 11.57 5.68
8 1.2 19.86 13.97

As per the above analysis, the 30mm length of jute fiber gave better stability as compared to the 15mm length of jute fiber. (Figure 1-7)

Example 5: Comparison On the Basis of The Length Of Jute Fiber
Experimental studies of jute fiber stabilization based on the length of the jute fiber were performed. According to the above analysis, the length of jute fiber which has 30mm give better stability as compared to the length of jute fiber which has 15 mm length.

Example 6: Comparison on the Basis of The Different Percentage of Jute Fiber With Respect To Weight of Soil.
According to the above analysis, the strength of soil and stress bearing capacity of soil is increasing with increasing percentage of jute fiber with respect to weight of the soil as depicted in figure 8.

While the invention is amenable to various modifications and alternative forms, some embodiments have been illustrated through examples in the drawings and are described in detail above. The intention, however, is not to limit the invention to those examples, and the invention is intended to cover all modifications, equivalents, and alternatives to the embodiments described in this specification.
The embodiments in the specification are described progressively and the focus of description in each embodiment is the difference from other embodiments. For the same or similar parts of each embodiment, reference may be made to each other.
It will be appreciated by those skilled in the art that the above description was in respect of preferred embodiments and that various alterations and modifications are possible within the broad scope of the appended claims without departing from the spirit of the invention with the necessary modifications.
Based on the description of disclosed embodiments, persons skilled in the art can implement or apply the present disclosure. Various modifications of the embodiments are apparent to persons skilled in the art, and general principles defined in the specification can be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is not limited to the embodiments in the specification but intends to cover the most extensive scope consistent with the principle and the novel features disclosed in the specification. , Claims:WE CLAIM:
1. A method to stabilize and strengthen soil with the help of mixing bitumen coated jute fibers of specific characteristics.

2. The method as claimed in claim 1, wherein the bitumen coated jute fibers are prepared with the help of a method comprising steps of:
i. cutting of jute fiber;
ii. coating of jute fibers obtained after step (i) in a bitumen emulsion bath;
iii. drying the coated jute fiber obtained after step (ii);
iv. curing of jute fibers obtained after step (iii) to achieve full strength of the bitumen coating.

3. Strengthened soil prepared by the method as claimed in claim 1, wherein the strengthened soil has 0-1.2% of 30mm jute fiber coated with bitumen having California bearing ratio (CBR) in the range of 5-20%.

4. Strengthened soil prepared by the method as claimed in claim 1, wherein the strengthened soil comprising bitumen coated jute fiber has 10-15% increase in California bearing ratio (CBR) than normal soil.

5. Strengthened soil prepared by the method as claimed in claim 1, is used in the construction of roads, pavements, construction of retaining walls, bridge abutments for highways, industrial and mining structures, etc.

Documents