## 1 Introduction  
In parallel with the acceleration of economic growth, the construction of reservoirs and dams has markedly increased. Of these, earth-rock dams are the most prevalent type of dam, typically utilizing locally available soil-rock mixtures. In comparison to other conventional materials, soil-rock mixtures, which are primarily composed of red sandstone and silty clay, exhibit lower rock strength and are susceptible to disintegration and fragmentation as a result of external environmental factors [1, 2]. Furthermore, the combined effects of water leaching and sunlight exposure can cause silty clay to become soft [3; 4], which may potentially compromise the stability of earth-rock dams and the safety of personnel. It is common practice among those utilizing traditional stabilizers to employ inorganic materials, including lime, cement, and fly ash, with the objective of enhancing soil properties. Some researchers have demonstrated that traditional stabilizers can enhance soil strength [5; 6; 7; 8], cohesion and friction angle [9; 10; 11], as well as water stability [12; 13; 14] and freeze-thaw durability [15; 16; 17]. However, these stabilizers may also have an adverse impact on the environment. To address the issue of environmental pollution, a technique known as microbial-induced carbonate precipitation (MICP) [18; 19] has been developed. [PERSON] et al. [20] demonstrated that MICP significantly enhances the shear strength of expansive soils, as well as improves cohesion and friction angle. [PERSON] et al. [21] observed that MICP enhances the strength of silty clay and provides a long-lasting urease reaction. As reported by [PERSON] et al. [22], the stabilization of soft soils through the mixing of cement with MICP resulted in notable improvements in cohesion, friction angle, compressive strength, elastic modulus, and toughness. However, current MICP technology is confronted with a number of challenges, including limited microbial activity periods, considerable environmental interference, and inconsistent curing. The use of xanthan gum and lignocellulosic as novel sustainable stabilizing materials effectively addresses the aforementioned issues. Xanthan gum is a biopolymer with low concentration and high viscosity, which can effectively bind soil particles, improve soil integrity, and control water movement in the soil to improve soil water retention compared with traditional soil improvement methods [23]. [PERSON] et al. [24] found that clay treated with a xanthan gum and guar gum composite had a stronger cohesive force, smaller friction angle, and higher shear strength than that treated with a single colloid. [PERSON] et al. [25], using scanning electron microscopy, found that xanthan gum and guar gum can form filamentous and reticulated structures with clay particles and that this flocculation is the main factor in increasing strength. [PERSON] et al. [26] demonstrated that xanthan gum has a significant impact on the strength and slope stability of laterite. Lignosulfonate, which is composed of negatively charged polycyclic organic compounds, exhibits a strong affinity for high-valent metal ions present in the soil. Furthermore, lignosulfonate offers additional benefits, including high economic value, renewability, and non-pollution [27]. [PERSON] et al. [28] demonstrated that lignocellulosic enhances the compressive strength of loess through a chemical reaction with clay minerals via hydrolysis. [PERSON] et al. [29] demonstrated that lignosulfonate enhances soil water stability without the formation of new minerals. Most scholars tend to focus only on soil improvement, and relatively few studies have been carried out on improving gravel soil. [PERSON] et al. [30] found that bipolymeric materials can significantly improve the cohesion and friction angle of gravelly soils; [PERSON] et al. [31] found that the addition of lime can increase the strength of gravelly soils, and that the curing effect is most significant at a dosage of 9%.