Experimental Study on the Physical and Mechanical Properties of Modified Clay Using Xanthan Gum and Guar Gum Composite Materials

Abstract

Biopolymer stabilization of soils has emerged as a viable solution for enhancing the engineering properties of soils in recent years. Xanthan gum and guar gum are two commonly used biopolymers. When combined, these materials have the ability to create stronger gels or gel strengths comparable to those achieved by using xanthan or guar gum individually, but at lower total concentrations. However, the extent of this synergistic viscosity-enhancing effect on soil improvement remains unclear. This study analyzes the effects of xanthan gum and guar gum on the physical and mechanical properties of clay under both individual and combined conditions using Atterberg limits tests, compaction tests, and triaxial consolidation undrained tests. At a 2% biopolymer content, the liquid limit of clay treated with a combination of XG and GG compounds increases by up to 8.0%, while the plastic limit increases by up to 3.9% compared to clay treated with a single colloid. With an increase in the mixing ratio, the optimal water content initially rises and then declines, peaking at 27.3%. The maximum dry density follows a pattern of initially decreasing and then increasing, with the lowest value recorded at 1.616 g·cm⁻³. Moreover, the shear strength of specimens treated with the XG and GG combination generally surpasses that of specimens treated with XG or GG alone. Furthermore, the combined treatment results in increased plasticity, highlighting its potential to enhance safety and stability in engineering applications.

1. Introduction

Soil improvement is a crucial step in sustainable construction projects, with the three main methods being physical, chemical, and biological improvement. Physical methods involve techniques like ramming, static compaction, and aggregate mixing. Chemical improvements entail mixing chemical additives, such as cement, to enhance the soil’s strength and durability. However, the widespread use of cement can lead to groundwater contamination and contribute to the urban heat island effect [1,2,3]. Furthermore, cement production releases significant amounts of carbon dioxide, exacerbating the global greenhouse effect [2,3]. In 2018, cement production accounted for 8% of the world’s total anthropogenic carbon dioxide emissions [4]. Biological improvement methods include Microbially Induced Calcium Carbonate Precipitation (MICP) and biopolymer amendment. MICP involves introducing Pasteurella to bind with calcium in the soil, forming calcium carbonate precipitation that gels the soil [5,6]. While both MICP and biopolymers can enhance soil mechanical properties, biopolymers offer advantages over MICP. MICP is only suitable for large-grained soils like sand, as fine-grained soils lack the necessary pore size for bacterial survival [2,7]. Additionally, MICP requires specific environmental conditions and nutrients for bacterial survival, whereas biopolymers do not necessitate such treatment [7,8].

Biopolymers, derived from natural sources such as plants, wood, and animal shells, have shown no documented negative impact on the environment. Among these polymers, xanthan gum (XG) and guar gum (GG) have garnered significant attention from scholars due to their remarkable effects on soil amendment. XG and GG have demonstrated the ability to stabilize various types of soils, including tailings [9]. Soils treated with XG or GG have exhibited substantial improvements in their geotechnical properties, such as consistency limits, compaction characteristics, shear strength, hydraulic conductivity, metal encapsulation capacity, erosion resistance, durability, and moisture retention capacity. A summarized overview of these improvements is provided in

Table 1. Summary of effect of biopolymer treatment (XG/GG) on the geotechnical properties of various soils.

Soil	Biopolymer	Observations	Reference
Poorly graded sand and high-plasticity silt	XG/GG	After treatment with XG and GG (2%), the permeability coefficient of sand decreased to 4% and 1%, respectively. For silt, after adding XG and GG (2%), the permeability coefficient value decreases to 10%.	[10]
Sand/Natural soil/Red yellow soil/Clay	XG	The compressive strength of sand/natural soil/red yellow soil/clay treated with xanthan gum (1%) and cured for 28 days is 880 kPa, 3680 kPa, 4940 kPa, and 2540 kPa, respectively.	[11]
Residual soil	XG/GG	Reinforcing soil at 5% XG and GG decreased the specific gravity from 2.69 to 2.19 and 2.24.	[12]
Sand	XG	After treating sand with xanthan gum (5%) and curing for 7 days, the internal friction angle increased by 1.9 times.	[13]
Sand/Clay/Silty sand	XG	After 5 days of XG treatment and curing of silicon sand/clay, the deviatoric stress increased to 1.70 MPa and 1.47 MPa, and the maximum deviatoric stress value of plain sand was extremely low.	[8]
Silty–clay soil	XG/GG	After treatment with XG and GG (2%), the maximum dry density of clay decreased to 17.55 kN/m3 and 17.65 kN/m3, respectively, and the optimal moisture content increased to 17.2% and 16.1%, respectively.	[14]
Kaolin	XG/GG	After treatment with XG and GG (2%), the liquid limit of Kaolin were increased to 74% and 83%, respectively. The UCS values of the soil samples treated with XG/GG increased, and the samples prepared at the optimal moisture content reached the maximum strength value.	[15]
Red mud waste	XG/GG	The turbidity value of untreated RMW ranges from 35 to 374 NTU. In contrast, the turbidity values of GG and XG corrected samples were 3 to 24 NTU and 2 to 18 NTU, respectively.	[16]

.

The effect of xanthan gum and guar gum on soil improvement has been extensively studied. The existing literature suggests that the interaction between xanthan gum (XG) and galactomannan (GG, such as locust bean gum and Cassia tora gum) molecules can result in a synergistic effect, enhancing the viscosity and gel properties of the mixed colloid [17]. For instance, the combined use of XG and GG has been found to notably boost the viscosity of mixed colloids [18]. XG and LBG exhibit a synergistic relationship, forming a thermally reversible gel [19]. Additionally, the viscosity of CTG solution significantly increased with the addition of a small amount of XG, reaching maximum instantaneous viscosity when the ratio of CTG:XG was 3:1 [20]. However, there is a scarcity of research on soil enhancement through the synergistic thickening effect of xanthan gum and galactomannan (such as GG). This study aims to investigate whether the combined use of xanthan gum and guar gum can enhance soil strength. The improvement effect of blending these biopolymers on clay strength was analyzed through Atterberg limits tests, compaction tests, and triaxial tests on xanthan gum- and guar gum-amended soil.

2. Materials and Methods

2.1. Test Materials

2.1.1. Clay

Soil samples for this experiment were collected from the South District Ecological Base of Hubei University of Technology. The soil underwent a process where impurities were initially removed, followed by air-drying, crushing, and passing through a 2 mm sieve for subsequent analysis. The basic physical properties of the soil samples were assessed in accordance with the ‘Standard for Geotechnical Test Methods’ GB/T50123-2019 [21] as outlined in

Table 2. Basic physical properties of experimental soil.

Liquid Limit/%	Plastic Limit/%	Plasticity Index	Specific Gravity	Optimum Moisture Content/%	Maximum Dry Density/g·cm−3
38.8	24.0	14.8	2.79	22.7	1.70

.

2.1.2. Biopolymer

The biopolymers xanthan gum and guar gum, sourced from Shangde Food Chemical Factory in Guangdong Province, China, were utilized as modified binders in the experiment.

Xanthan gum (XG) is a natural anionic polysaccharide produced through the fermentation of glucose or sucrose by Xanthomonas campestris [3,22,23]. Comprising mainly cellulose chains with a molecular weight ranging from 0.9 to 1.6 × 10⁶ g/mol, its rigid rod-like helical structure remains unaffected by temperature, pH, shear, and enzymatic degradation. Xanthan gum can display high viscosity and pseudoplastic behavior even at low concentrations [24].

Guar gum (GG) is a polysaccharide extracted from the seeds of guar beans, consisting of water (8–14%), galactomannans (75–85%), proteins, fibers, and ash [25]. In comparison to other natural water-soluble polysaccharides, GG has a higher molecular weight and more galactose branching points, leading to increased viscosity in liquids [26,27].

2.2. Specimen Preparation and Test Program

The biopolymers were mixed evenly based on the specified mixing ratio of xanthan gum to guar gum, followed by mixing with clay in the container according to the designated amount. Water was sprayed into the container until reaching a predetermined level, and the mixture was stirred to achieve a uniform sample. Throughout the test, the concentration of xanthan gum and guar gum in the stabilized soil decreased with the addition of water, while the ratio between xanthan gum and guar gum in the stabilized soil remained constant.

To explore the engineering properties of clay treated with xanthan gum and guar gum composite materials, various tests including the Atterberg limit, compaction, and triaxial consolidation without drainage were carried out on both treated and untreated specimens. The mixing design for these tests is outlined in

Table 3. Mixing design of samples under each test.

Variable	Atterberg Limit Test	Compaction Test	Consolidation Undrainage Test
Biopolymer content (%)	0; 0.5; 1.0; 1.5; 2.0	0; 0.5; 1.0; 1.5; 2.0	2
XG:GG	0:1; 1:3; 1:1; 3:1; 1:0	0:1; 1:3; 1:1; 3:1; 1:0	1:0; 1:1; 0:1

, with all tests conducted in accordance with GB/T50123-2019 [21].

A series of liquid limit (falling cone test) and plastic limit tests were conducted on clay samples mixed with varying amounts and ratios of xanthan gum and guar gum biopolymers. This study focused on the effects of biopolymer content, single and multiple blending ratios, on the plastic limit of clay liquids. The sample mix design for the Atterberg limit test included biopolymer contents of 0%, 0.5%, 1%, 1.5%, 2%, and blending ratios of 0:1, 1:3, 1:1, 3:1, and 1:0. The biopolymer–clay mixture, prepared according to the specified moisture content, was placed in an aluminum box for 24 h prior to testing. For the test, the mixture was then filled into a sample cup and subjected to repeated vibration with a scraper to release any internal gas.

In order to determine the shear strength properties, triaxial consolidation undrained (CU) tests were conducted on the treated specimens. The CU test samples were prepared at the optimum moisture content, with a biopolymer dosage of 2%, and a dosage ratio of 1:1. The biopolymer–clay mixture was compacted using a cylindrical mold with a height of 80 mm and a diameter of 39.1 mm. Following preparation, the test samples were wrapped with plastic to prevent drying and then placed in a curing box at a temperature of (20 ± 2) °C and humidity of 90% until the test date (28 days). To minimize variability, three specimens were prepared for each group, and triaxial consolidation tests without drainage were performed for each case.

3. Results and Discussion

3.1. Atterberg Limits of Biopolymer-Treated Clays

The Atterberg limit tests of xanthan gum- and guar gum-treated clay were conducted, and the results are depicted in Figure 1. Increasing the biopolymer dosage led to improvements in all liquid–plastic limit indicators. When clay was treated with 2% of XG and GG, the liquid limit increased from 38.8% to 59.4% and 62.8%, respectively, while the plastic limit increased from 24.0% to 35.8% and 37.1%, respectively, compared to samples without biopolymer. Analysis revealed that guar gum-treated samples had higher liquid–plastic limits than xanthan gum-treated samples at the same dosage. This is attributed to biopolymers inducing soil particles to form a flocculating structure, with higher biopolymer content accelerating this tendency. The resulting flocculated structure traps water, enhancing shear strength and the liquid–plastic limit [12,28,29]. Additionally, biopolymers form hydrogels with pore water, increasing pore fluid viscosity, which may impact the liquid–plastic limit. Viscosity is influenced by factors such as biopolymer type, content, solubility, and temperature [30]. Given guar gum’s higher viscosity compared to xanthan gum, its treated samples exhibited more viscous pore hydrogels. Furthermore, differences in biopolymer bonding types can affect the liquid–plastic limit. Xanthan gum, an anionic polysaccharide, forms cationic bridges with clay particles, while guar gum and clay particles bind through hydrogen bonding [31].

The liquid–plastic limit values of the treated samples increased when the clay was treated with a combination of xanthan gum and guar gum, aligning with previous findings for samples treated with XG or GG individually. Interestingly, at the same biopolymer dosage, the LPL of the treated samples exhibited a trend of increasing and then decreasing with the XG to GG ratio, peaking at XG:GG = 1:1. This behavior can be elucidated by examining the chemical structure and viscosity properties of xanthan gum and guar gum. The interaction between xanthan gum and guar gum molecules in pore water results in a synergistic increase in viscosity. Specifically, the unique conformation of XG when interacting with galactomannan facilitates enhanced interaction with hydroxyl and water molecules, leading to higher pore fluid viscosity and larger liquid–plastic limit values. Overall, the liquid limit is influenced by the viscosity of the pore structure and the specific biopolymer combination, with flocculation being the primary factor impacting the liquid plastic limit [32,33]. Molecules with a high degree of branching tend to exhibit increased hydrogen bonding and hydration, leading to slight variations in plasticity indices [12].

3.2. Compaction Properties of Clay Treated with Biopolymer Compounding

The figure displays the optimal moisture content and maximum dry density of clay samples with varying biopolymer types and incorporation levels. Findings indicate that the inclusion of xanthan gum and guar gum led to a decrease in maximum dry density and an increase in the optimum moisture content of the clay. As the biopolymer incorporation rose from 0 to 2%, the maximum dry density of xanthan gum- and guar gum-treated samples decreased from 1.701 g/cm³ to 1.652 g/cm³ and 1.642 g/cm³, respectively. Additionally, the optimal water content of xanthan gum- and guar gum-treated samples increased from 22.7% to 25.4% and 25.9%, respectively, aligning with the findings of Chang et al. [11]. The impact on maximum dry density varies based on the soil type, with the biopolymer interacting directly with soil particles and water. Higher biopolymer content leads to the absorption of more water, forming a viscous suspension that disperses soil particles and fills voids [16], ultimately increasing the space between clay particles and reducing maximum dry density. The rise in the optimum water content can be attributed to the increased water absorption from higher biopolymer incorporation [8].

The results presented in Figure 2 demonstrate that the maximum dry density decreases and the optimum water content increases in clay specimens treated with a combination of xanthan gum and guar gum, as opposed to specimens treated with only xanthan gum or guar gum, across various dosing conditions. Specifically, the maximum dry density and optimum water content were found to be the lowest at a blending ratio of 1:1. The interaction between xanthan gum and guar gum can lead to the formation of stronger gels or gels with similar strengths at lower total concentrations compared to the gelation of individual biopolymers, resulting in what is known as a synergistic tackifying effect [34]. This synergistic effect increases viscosity, inhibits inter-particle interactions, and enhances pore volume after treatment with xanthan gum and guar gum, ultimately causing a decrease in maximum dry density. As the mixing ratio of xanthan gum and guar gum increases, fluid viscosity initially rises and then falls, reaching a peak at a mixing ratio of 1:1. This is when the stabilized clay exhibits its lowest maximum dry density. The higher water content required to form gel particles when xanthan gum and guar gum are combined, particularly at a 1:1 mixing ratio, leads to an increase in the optimal water content.

3.3. Shear Strength Characteristics of Biopolymer Compound-Treated Clay

3.3.1. Stress–Strain Characteristics of Clay Treated with Xanthan Gum and Guar Gum Compounding

The stress–strain curves of the biopolymer single-doped and double-doped treated specimens under various peripheral pressures are depicted in Figure 3, all exhibiting a strain softening behavior. As the peripheral pressure increased, the stress–strain curves of the treated specimens shifted upwards. Specifically, when the peripheral pressure rose from 50 kPa to 200 kPa, the maximum bias stresses of xanthan gum-treated specimens, guar gum-treated specimens, and xanthan gum- and guar gum-combined-treated specimens increased from 164.22 kPa, 200.04 kPa, and 225.04 kPa to 269.42 kPa, 287.61 kPa, and 302.28 kPa, respectively. This indicates that, compared to single colloid treatment, the maximum shear strength was higher for xanthan gum and guar gum compounded-treated clay specimens, while the minimum shear strength was observed in xanthan gum-treated clay specimens.

The enhancement of shear strength in clay treated with xanthan gum/guar gum has been supported by numerous studies [8,35]. To better understand the interaction and strength enhancement mechanism between clay and these biopolymers, it is important to consider the structural and chemical properties of each. Xanthan gum, a natural anionic polysaccharide, interacts with clay particles, which are primarily flat and arranged face-to-face or face-to-face linearly. The bonding between soil particles is mainly facilitated by electrostatic attraction and van der Waals force [36,37]. Biopolymers can form gels in pore water and effectively interact with clay particles [38]. Upon treatment with xanthan gum, exchangeable cations present between lamellar clay layers can bind to the biopolymer through cation bridging [15]. Furthermore, a reticulation formed by the biopolymer–clay interaction encapsulates clay particles, bridging distant particles and contributing to improved shear strength and cohesion in xanthan gum-treated soils [11]. This enhanced strength is attributed to the continuous formation of xanthan gum–soil reticulation.

Figure 4 illustrates the shear strength of clay samples treated with guar gum. Typically, the shear strength of samples treated with guar gum was higher than those treated with xanthan gum. Variations in biopolymer structures can result in differences in the shear strength of modified clays. Variations in the chemical functional groups and structures of biopolymers lead to diverse soil biopolymer matrices, ultimately enhancing strength. Guar gum, a polymeric polysaccharide, lacks functional groups that impart any charge, making it a neutral polymer [14,39]. Molecular interactions between guar gum and clay primarily involve hydrogen bonding, while interactions between xanthan gum and clay are mainly cation bridging with less hydrogen bonding. Moreover, guar gum exhibits higher viscosity in aqueous solutions compared to xanthan gum, leading to enhanced shear strength in guar gum-treated samples.

Previous research has shown that the interactions between clay and biopolymers are influenced by factors such as concentration, water content, and duration of maintenance [15,40]. However, there is limited research on the interaction of xanthan gum and guar gum with clay post-compounding. The findings presented in Figure 3 indicate that the shear strength of samples treated with a combination of xanthan gum and guar gum was higher compared to samples treated with either xanthan gum or guar gum alone. This enhancement can be attributed to the structural and chemical properties of xanthan and guar gums, as well as the viscosity synergism resulting from intermolecular interactions between xanthan side chains and galactomannan molecules [41]. A blend of xanthan and guar gum solutions exhibits greater viscosity than individual gum solutions, leading to the higher shear strength observed in samples treated with compounded xanthan gum and guar gum.

The maximum deviatoric stress of the treated samples increases to some extent under high perimeter pressure. This is attributed to the biopolymer filling the soil pores and forming a hydrosol with the pore water, which adsorbs surrounding soil particles and creates soil agglomerates. The lubricating effect of the flocculated material and agglomerates, combined with the increase in surrounding pressure, leads to densification of the consolidated specimens, thereby improving shear strength. Moreover, the upper part of the XG- and GG-treated soils showed a significant leftward shift under high enclosing pressure, indicating an enhancement in their elastic modulus and deformation modulus.

The strain value corresponding to the maximum deviatoric stress is highest for XG and GG compounding, followed by GG-treated soil samples, and is lowest for XG-treated soil samples. This is attributed to the synergistic viscosity enhancement effect resulting from intermolecular interactions between XG and GG. The increased viscosity enhances the hydrogel’s ability to adsorb clay particles, promotes the formation of a mesh structure between the biopolymer and clay particles, and enhances specimen plasticity. Consequently, the strain value increases when reaching the maximum bias stress with XG and GG compounding. Due to GG’s high molecular structure and greater viscosity compared to XG, the agglomeration of molecules and cementation between guar gum and clay particles strengthen the clay’s plasticity more than that of XG-treated clay. As a result, the strain value corresponding to the maximum bias stress in GG-treated soil samples surpasses that of XG-treated soil samples.

3.3.2. Shear Strength Parameters of Xanthan Gum and Guar Gum Compounding-Treated Clay

Based on the triaxial shear test data, the shear strength envelopes of XG- and GG-stabilized soils under different blending conditions were obtained as shown in Figure 5. The shear strength parameters are presented in

Table 4. Shear strength parameters.

XG:GG	Cohesive Force c/kPa	Internal Friction Angle φ/°
1:0	49.3	15.28
0:1	68.8	13.16
1:1	83.7	12.02

. The cohesion of the specimens was highest when XG and GG were mixed in equal amounts, followed by GG-treated specimens, with the lowest cohesion observed in XG-treated specimens. Cohesion in soil comprises initial cohesion and additional cohesion. The former arises from particle attraction in the soil, while the latter results from chemical components cementing the soil, influenced by factors like moisture content, density, and degree of cementation. Biopolymers, due to their small particle size, enhance adsorption with the soil surface, boosting initial soil viscosity. The biopolymer’s gelling properties help fill clay pores, increasing clay compactness and additional cohesion [7]. Moreover, the compounded XG and GG exhibit a synergistic viscosity increase, enhancing cohesion and gravitational force with soil particles. This synergy promotes easier aggregation of soil particles, forming agglomerates that increase density and cementation. Consequently, compounding XG and GG results in maximum cohesion in the specimen.

The specimens treated with equal mixing of XG and GG exhibited the smallest angle of internal friction, followed by the GG-treated specimens, with the XG-treated specimens showing the largest angle of internal friction. The angle of internal friction in clay is heavily influenced by factors such as particle composition, size, smoothness, and occlusion mode between particles. Biopolymers were encapsulated within smaller clay particles, forming agglomerated structures with larger particle sizes. As particle size increases, the contact area between particles decreases, leading to weaker linkages and a lower angle of internal friction. Moreover, the addition of biopolymer increases surface friction between soil particles, with some biopolymer particles embedding in the soil and occluding with soil particles, further enhancing the angle of internal friction. Under the combined effect of the two, neither mixed nor single biopolymers have a significant impact on the internal friction angle of the sample. When these two polymers are mixed, an excess of glue is produced, which then becomes adsorbed on the soil particles’ surfaces. This leads to an increase in the bonding water between soil particles, resulting in a decrease in the sliding resistance and ultimately lowering the internal friction angle. Guar gum has a spherical molecular structure, while xanthan gum has a chain structure. This difference in molecular structure affects the interaction between these gums and soil particles, resulting in a smaller internal friction angle compared to specimens with only xanthan gum.

3.3.3. Triaxial Shear Failure Characteristics of Xanthan Gum- and Guar Gum-Treated Clay

Figure 6 illustrates the damage morphology of the consolidated undrained (CU) test samples under different enclosure pressures, using a doping ratio of xanthan gum and guar gum at 1:1. When subjected to an enclosing pressure of 50 kPa, the specimen exhibited a clear through-fracture surface post shear damage. Conversely, at an enclosure pressure of 200 kPa, the samples displayed bulging and dwarfing deformation without a significant shear surface. This observation implies that the biopolymer–clay system is more stable under triaxial stress conditions and higher perimeter pressures. This increased stability could be attributed to the ability of XG and GG complexes to densely fill the gaps between clay particles at higher perimeter pressures, resulting in a compact arrangement of biopolymer and soil particles. Consequently, this compact arrangement enhances the density and stiffness of the soil [13].

4. Conclusions

Xanthan gum and guar gum are commonly used as additives for soil consolidation through biopolymers. This study aimed to investigate the synergistic viscosity-increasing effect of xanthan gum and polysaccharide on soil improvement. By replacing the traditional stabilizer with xanthan gum and guar gum, and using clay as the research material, various tests including Atterberg limits, compaction, and solidification undrained triaxial tests were conducted. The study analyzed the changes in physico-mechanical properties when stabilizing clay with XG and GG under different amounts and conditions of doping. The main conclusions drawn from this research are as follows:

(1)

The liquid limit, plastic limit, and plasticity index of clay increase with higher biopolymer content. For a specific biopolymer content, the liquid–plastic limit of clay initially rises and then falls as the XG and GG mixing ratio increases. The liquid–plastic limit of clay peaks at a 1:1 ratio of xanthan gum to guar gum.

(2)

The maximum dry density of the clay decreases and the optimum moisture content increases with the increase in biopolymer dosage. Additionally, the maximum dry density showed a trend of decreasing and then increasing with the increase in the mixing ratio, while the optimal water content showed a trend of increasing and then decreasing. Interestingly, at the mixing ratio of 1:1, although the maximum dry density is the smallest, the optimal water content is the largest.

(3)

The stress–strain curve of biopolymer–clay displays a strain-softening behavior. As the perimeter pressure increases, the shear strength and modulus of elasticity of the specimen also increase, resulting in a more stable biopolymer–clay specimen. Furthermore, the stress–strain relationship of biopolymer–clay shows an increase with higher biopolymer doping. When XG and GG are compounded in equal amounts, the stress–strain curves shift to the right, indicating higher plasticity. Additionally, the peak stress of the biopolymer–clay is observed to be the highest in this scenario.

(4)

The disordering of XG is crucial in the interaction process with guar gum. This interaction enhances the viscosity of the mixed colloid, leading to the formation of a more densely intertwined network structure with clay particles, thereby improving the engineering properties of clays.

(5)

The compounded XG- and GG-treated clay exhibited stronger cohesion, a smaller internal friction angle, and higher shear strength compared to the single-colloid-treated clay. Following this, the specimen with single-doped guar gum showed intermediate results, while the specimen with single-doped xanthan gum displayed the lowest cohesion, the largest internal friction angle, and the smallest shear strength. This suggests that the increase in cohesion has a greater impact on shear strength than the reduction in the internal friction angle. Therefore, compounding biopolymers is advantageous in enhancing the integrity of soil samples and improving the ability of specimens to withstand damage and deformation, ultimately contributing to the safety and stability of the project.