Debris flows are catastrophic mass movements with significant social and environmental consequences, particularly in the Western Himalayas. Understanding the rheological properties of debris flow material is crucial for accurately modeling their behavior and predicting their impacts. In this study, rheological parameters such as yield stress and viscosity were determined through extensive laboratory testing using a parallel plate setup in a rheometer. Reconstituted soil samples from the debris flow zone were prepared using an optimized sampling approach to vary the solid volume concentration and water content (w/c). Experimental results revealed non-Newtonian behavior for all tested compositions, which closely aligned with the Herschel-Bulkley rheological model. The Herschel-Bulkley parameters were subsequently used to calibrate a smooth particle hydrodynamics (SPH) model in the open-access DualSPHysics tool. The results showed that water content and silt concentration played a significant role in influencing the rheology, with finer particles exhibiting higher viscosity and shear stress compared to coarser particles. The SPH simulations effectively replicated the flow behavior observed during the Kotrupi debris flow event (2017), providing insights into flow dynamics, such as velocity and shear distribution. This integration of experimental rheology and numerical modeling advances our understanding of debris flow mechanics and highlights the importance of incorporating rheological calibration in predictive debris flow models.

Debris flows are destructive mass movements that pose multifaceted challenges with profound social and environmental implications in the Western Himalayas. For precise modeling and flow behavior prediction, it is essential to understand the rheological characteristics of debris flow material. In the current study, rheological characteristics like yield stress and viscosity were determined by a series of lab tests using a parallel plate setup in a rheometer. An optimized sampling approach created the reconstituted soil samples of finer particles to change the solid volume concentration and volumetric water content (w/c). Later, the feature importance of finer particles in debris flow rheology was determined using a machine learning regressor. Non-Newtonian behavior was shown by each composition and was similar to Herschel-Bulkley's rheological model. The eXtreme Gradient Boosting (XGBoost) regression model was developed for rheological parameters with robust model fitting with R2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${R}{2}$$\end{document} = 0.90 for yield stress and R2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${R}{2}$$\end{document} = 0.94 for viscosity. The model helped in understanding the sensitivity of rheological parameters with solid constitutents of debris flows. The findings showed that water content and silt concentration substantially impacted the debris flow's rheology. The yield stress was more dominated by silt followed by fine sand, whereas water content influenced the viscosity more than any solid concentration. The flow behavior was also affected by the distribution of grain sizes, with finer particles exhibiting higher viscosity and shear stress than coarser particles. These results enhance understanding of debris flow rheology and highlight the complex interplay between geohazards and sustainable development.

Asphalt is considered one of the most essential materials used for road construction because of the high energy requirement for its production and its large greenhouse gas emission. VG30-grade asphalt is extensively utilized in road constructions as a binding material due to its ideal viscosity and superior performance characteristics at different climatic conditions, particularly in nations such as India. Biochar are materials, produced from organic biomass by pyrolysis. This study examined the influence of biochar produced from plant biomass as an alternative binder modifier for pavement. The investigation focused on the feasibility of using biochar at different percentages of 2.5%, 5%, 7.5%, and 10% by weight of VG30 to make it sustainable. Various physical experiments carried out included penetration test, softening point test, storage stability analysis and ductility test. Additional rheological tests carried out included rotational viscosity, original binder grading and Multiple Stress Creep and Recovery (MSCR). The findings demonstrated that using a binder modified with biochar led to significant improvement in rheological parameters, including enhanced rutting resistance, higher failure temperature and improved percentage recovery (R%). A decrease in the Non-Recoverable Creep Compliance (Jnr) value was also observed. The results showed therefore, that asphalt treated with biochar became more capable of resisting high temperatures. Thus, it can be determined that the biochar-modified binder at a 10% concentration is the most effective one regarding performance. The research emphasizes that biochar is a promisingly effective material that can enhance asphalt performance and contribute to improve agricultural waste management.

This study presents a simple, yet robust testing methodology employed for investigating the mechanical behaviour of soils under cyclic loading conditions. Small cylindrical specimens of soil (10.5 mm diameter and 35.0 mm high) were subjected to oscillatory torsional loading in either strain sweep or stress sweep mode using the dynamic shear rheometer. Key mechanical properties, including dynamic shear modulus, phase angle, and energy dissipation capacity, were obtained and used to effectively identify threshold strain levels which differentiated the linear, nonlinear, and damage response of the soil. This study further applied the proposed method to stabilized soils to evaluate the effects of stabilizers on improving soil stiffness, while also considering their potential effects on increasing soil brittleness, which could ultimately lead to reduced resistance to fatigue cracking. The successful development of this testing protocol has the potential to evolve into a specification-type method due to its efficiency, repeatability, sensitivity, and fundamental robustness.

Soil conditioning technology is usually required to modify the excavated soil to a fluid plastic state during the construction with earth pressure balance (EPB) shield. The steady pressure distribution in the excavation face is linked to soil fluidity. Compared with the slump test, the rheological behavior of the conditioned soil can better reflect the dynamic flow characteristics. A gas-loading rotational rheometer is developed to test the rheological properties of the conditioning agents and the conditioned sandy soil, which can overcome the disadvantage of uneven mechanical loading and create gas-loading conditions. The rheological properties of sandy soil conditioned by different agents under atmospheric and gas-loading pressure conditions were studied, and the influences of foam injection ratio (FIR), bentonite slurry injection ratio (SIR), and polymer injection ratio (PIR) on soil viscosity were analyzed. The test results show that the ambient air pressure only greatly influences the experimental group with foam. Under the same gas-loading pressure, the foam's apparent viscosity decreases with the foam expansion ratio (FER) increasing. The rheological behavior of the conditioned sandy soil conforms to the Bingham model under atmospheric pressure and conforms to the Power Law model when PIR 10 %, the rheological curve of three agents conditioned sand conforms to the Herschel Bulkley model. The higher content polymer reacts with bentonite to increase the soil viscosity, and blocks the foam seepage channel, making it difficult for the foam to re-enter the soil under gas-loading pressure. Investigating the rheological behavior of different conditioned sandy soil provides optimization strategies for EPB performance.