Debris flows are a type of natural disaster induced by vegetation-water-soil coupling under external dynamic conditions. Research on the mechanism by which underground plant roots affect the initiation of gulley debris flows is currently limited. To explore this mechanism, we designed 14 groups of controlled field-based simulation experiments. Through monitoring, analysis, calculation, and simulation of the changes in physical parameters, such as volumetric water content, pore-water pressure, and matric suction, during the debris flow initiation process, we revealed that underground plant roots change the pore structure of soil masses. This affects the response time of pore-water pressure to volumetric water content, as well as hydrological processes within soil masses before the initiation of gully debris flows. Underground plant roots increase the peak volumetric water content of rock and soil masses, reduce the rates of increase of volumetric water content and pore-water pressure, and increase the dissipation rate of pore-water pressure. Our results clarify the influence of underground roots on the initiation of gulley debris flows, and also provide support for the initiation warning of gully debris flow. When the peak value of stable volumetric water content is taken as the early warning value, the early warning time of soil with underground plant roots is delayed by 534 to 1253 s. When the stable peak value of pore-water pressure is taken as the early warning value, the early warning time of soil with underground plant roots is delayed by 193 to 1082 s. This study provides a basis for disaster prevention and early warning of gully debris flows in GLP, and also provides ideas and theoretical basis under different vegetation-cover conditions area similar to GLP.

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.

Collapse pits are highly susceptible to secondary hazards such as underground debris flows and slope instability under mining disturbances. These hazards significantly damage the ecological environment of the mining area. To reduce the geological hazards of collapse pits, grouting is used for management. The diffusion pattern and curing mode of slurry under different grouting pressures were investigated through indoor grouting simulation tests, and industrial tests were carried out to assess grouting effects. The results indicate that the slurry is dominated by penetration diffusion and supplemented by splitting diffusion in the moraine. The penetration distance and diffusion radius of the slurry increase linearly with grouting pressure, while the splitting uplift distance and cured volume increase exponentially with grouting pressure. Splitting diffusion consists of three stages: bulging compaction, splitting flow, and passive uplift. Horizontal splitting has a vertical uplift effect on the formation. The slurry primarily consolidates individual moraine particles into a cohesive mass by filling fractures, binding soil particles, and reinforcing interfaces with the rock mass. For different moraine layer structures, full-hole, segmented, and point-based grouting methods were applied. A composite grouting technique, layered grouting with ring solidification, was also introduced, achieving excellent grouting results. This study provides technical support for managing geological hazards in collapse pits caused by block caving mining disturbances and for green mining practices.

On the morning of July 30, 2024, a catastrophic landslide struck Wayanad, India, in the ecologically sensitive Western Ghats, claiming over 260 lives, with many still missing beneath the debris. Here, we present a comprehensive overview of the landslide event based on field, satellite, and aerial images analysis, numerical modeling, and geotechnical testing to unravel the failure mechanism and its catastrophic impact on downstream communities. Our analysis revealed that a pre-existing crack, formed in 2020, acted as the initiation point for the recent failure. The underlying weathered and sheared geology, coupled with structural discontinuities, and thick soil strata, exacerbated by intense rainfall on July 29-30, catalyzed the transition of a planar slide into a catastrophic debris flow. Numerical simulations indicate that the debris flow initiated around 01:00 h, peaked at 04:00 h, and reached a maximum velocity of 28 m/s. The estimated volume of displaced material ranged between 5.17 x 106 and 5.72 x 106 m3, ranking it among the largest debris flows in India. The flow's run-up height in the transitional zone reached 32 m, amplified by multiple damming effects and topographic features such as cascades and river sinuosity, causing extensive infrastructure damage to the downstream population. Given the terrain's known fragility and history of sequential events, this region requires urgent attention for real-time monitoring and mitigation strategies to reduce future risks.

On July 20, 2024, a rainfall-induced, group-occurring debris flow event occurred in the Malie Valley, southwestern China. This study systematically investigated the damage and rainfall-triggering conditions of the debris flow event using remote sensing data, field surveys, and satellite-based rainfall measurements. Debris flows were commonly initiated by mobilizing widespread shallow landslides on steep slopes. Among them, the Lannisanwan (LNSW) debris flow was the most extensive and destructive, and its impact was amplified due to several factors, such as steep terrain gradient, high channel sinuosity index, and significant accumulation of loose material. The LNSW debris flow reached a velocity of 5.29 m/s and a peak discharge of 2,304.30 m3/s at the catchment outlet. Furthermore, the convergence of debris flows from tributaries exacerbated the hazards alongside the main valley channel. Though the event was triggered by the short-duration night rainfall, with a peak intensity of 25.44 mm/h, antecedent rainfall played a critical role. Rainfall analysis revealed that the 3-day antecedent effective rainfall total was as high as 108.75 mm, 4 to 20 times greater than those of past heavy rainfall events in the area. This study emphasizes the importance of antecedent rainfall preceding intense rainfall on landslide-type debris flows and highlights the aggravating effects of group-occurring and night-occurring on the magnitude and consequences of debris flows.

The Pernote landslide event in the Ramban area on April 25, 2024, caused significant damage and displaced many residents. Preliminary investigations identified the landslide as a massive, complex debris slide and flow, primarily involving overburden materials such as mud, silt, clay, and rock fragments. The slide was characterized by several rotational slip planes and debris flow channels. The severity of the event was attributed to explicit geological conditions, including fault and thrust zones, loose consolidated and deformed rocks from the Murree Formation, and thick deposits of Quaternary sediments exceeding similar to 20 m. Heavy antecedent rainfall (100-175 mm) from April 20th to 24th saturated the debris and soil cover, triggering the landslide on the steep slopes (angle > 45 degrees). The total displacement was approximately 40 m, with a depth of about similar to 12 m. The slide zone extended from the crown to the toe, reaching up to the River Chenab, covering approximately 1250 m. The Pernote landslide was not entirely unexpected, as early signs of movement-such as deep fissures, ground cracks, and bulges-were observed as early as 2021. Temporal analysis of high-resolution Google Earth images from 2012 to 2022 supports these observations, revealing signs like old landslide scars, ground cracks, and ongoing landslide activity. Additionally, during the past decade, significant changes in vegetation cover and a 19.2% increase in built-up areas were noted. These findings highlight the importance of monitoring early surface indications as warning signs for effective landslide mitigation, preparedness, and public awareness to prevent loss of life and infrastructure in future events.

Natural cementation of rock debris is a spontaneous geochemical process that plays an important role in geotechnical stabilization. The focus of this study is to analyze the natural cementation phenomenon in mudslide-prone areas using mineralogical and biological methods. We analyzed the formation of the natural cementation phenomenon by studying its mineral composition, elemental endowment distribution, mechanical properties, and community structure. Similarly, simulated cementation experiments of rock debris by carbonate mineralizing bacteria were carried out in the laboratory to assess the feasibility of biomineralization in the stabilization of rock and soil. The results show that the natural cementation of rock debris in mudslide-prone areas is caused by the formation of calcite under chemical action, and microorganisms also contribute to it; this cementation has multiple environmental protection significance, including improving the compressive properties of rock debris (up to 2.58 Mpa), slowing down or preventing the occurrence of geologic hazards such as slumps, landslides, etc., and significantly decreasing the migratory properties of heavy metal ions and its ecological risks. Laboratory simulation conditions showed that carbonate mineralizing bacteria were enabled to utilize the Ca2+ provided by weathering to achieve rapid cementation of the rock debris, which played an important role in the increase of their compressive strength and the improvement of their pore parameters. This study provides a theoretical basis for future engineering applications of biomineralization technology.

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.

This study explores the impact of granular materials with varying moisture contents and particle sizes, as well as block materials with different volumes and layer strengths, on landslide fragmentation, motion, and deposit. The experimental results show that as particle size increases, the maximum dam height (Hmax) and width (Wmax) increase, while the minimum dam height (Hmin) decreases, indicating an improvement in the stability of landslide dams. Larger particle sizes are less sensitive to changes in moisture content. Additionally, moisture content inhibits Wmax, with mixed particle-size materials showing a greater reduction compared to single particle-size materials. As Wmax increases, the maximum dam length (Lmax) decreases exponentially. Sliding time (Ts), deposition time (Td), and total time (T) decrease as particle size increases. For mixed particle-size materials, a more continuous particle size distribution further reduces Ts, Td, and T. Block material experiments show that with increasing block volume, Wmax, Lmax, and Hmax increase significantly, with corresponding increases in Ts, Td, and T. When the strength of the lower layer material decreases, Wmax and Hmax decrease, while Ts, Td, and T increase. Conversely, when the lower layer material strength increases, the opposite effect is observed. Frictional energy loss (Ef) is the primary energy loss pathway, with both total energy loss and Efdecreasing with increasing particle size. Localized energy losses are mainly due to terrain collisions, independent of moisture content.

Debris flows pose significant threats due to their high velocity and fluid-like consistency. This research evaluates the intricate failure mechanisms of the rainfall-induced debris-flow event in Nenmara, Palakkad district, Kerala, India, on August 16, 2018, through detailed investigations. A geophysical (Multi-channel Analysis of Surface Waves (MASW)) test was carried out to obtain the shear wave velocity (Vs) of substrata. The dewpoint potentiometer and ring shear test were used to assess unsaturated soil strength and residual shear parameters to analyse the progressive failure mechanism of the landslide using the numerical model LS-RAPID. The mineralogical studies in the Nenmara region reveal that the soil originated from charnockite rocks containing quartz and clay minerals. The low Vs of 197 m/s at 2 m depth indicates the loose and unconsolidated soil layer at the site. The debris flow initiates when the pore water pressure ratio (ru) rises to 0.40 with a peak velocity of 11.9 m/s and 13.9 m/s in the X and Y directions, which led to the demolition of 3 buildings and the loss of 8 lives. The deterministic analysis reveals that ru above 0.30 can trigger a landslide near the Nenmara location. The rainfall threshold analysis suggests that 148 mm of daily or 210 mm of continuous rainfall over five days can trigger landslides around the Nenmara region. This research combines geophysical, geotechnical, and numerical simulations to make a substantial contribution to disaster management in comprehending the mechanism of debris flow by identifying triggering factors, and it will help to find the appropriate mitigation measures for future hill area development.