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.

The seismic performance of a long-span triple-tower suspension bridge is a critical consideration in engineering communities. To promote a better seismic design, this paper presents a parametric study on the structural seismic control using hysteretic steel dampers. The finite element model is firstly established, and an introduction to the mechanical properties of the E-shaped hysteretic steel damper is made. Then, a seismic analysis is conducted under uniform earthquake excitations. Considering the effect of wave passage, the performance of hysteretic steel dampers in seismic control is further analyzed. The results indicate that the travelling wave effect greatly affects seismic responses. Increasing the damper elastic stiffness can effectively reduce the relative displacement between the main girder and either the left or the central tower. This treatment is effective for the right tower only when the wave velocity is among 400-1600 m/s, while it makes little contribution in other ranges. At an arbitrary wave velocity, increasing the damper elastic stiffness would cause minor changes to the shear forces of side towers, while its influence on the central tower is significant. A reasonable damper design for the long-span triple-tower suspension bridge depends on an essential prior evaluation of the wave velocity based on soil conditions.

This paper presents a theoretical framework for approximating the gelling concentration in suspensions, with a focus on its application to the parameterization of soil consolidation processes in coastal sediment environments. The model is based on the integration of principles from rheology, colloid science and sedimentology, and the analysis of the change in rheological viscosity as a function of volumetric sediment concentration. Validation is performed against measured rheological data and shows that the model is able to accurately approximate the gelling concentration of sediment under varying environmental conditions. The model provides valuable insights into the consolidation dynamics of saturated soils in estuaries by linking micro-scale sediment properties and macro-scale geotechnical phenomena. In addition, amore robust constitutive equation for estimating effective stress was developed that accounts for both permeability and effective stress regimes by incorporating the underlying physics of each. The results show that the proposed model closely aligns with the conceptual model of sediment concentration profile, accurately depicting the transition from fluid mud to consolidated bed, and capturing the irregularities and inflection points in sediment concentration that were not represented in previous models.

Diaphragm walls are rectangular shaped cast in place deep foundations. There are two critical phenomena occurring, according to which the final quality can be affected: bentonite suspension exfiltration and concrete placement. Some imperfections seem to appear recurrently on the surface of the final wall. The defects are known as shadowing pathologies. The main reasons can be attributed to the dual effect of exfiltration mechanisms and kinematics of concrete flow. The objective of this study is developing a numerical tool to prevent the appearance of shadowing pathologies by visualizing the concrete flow in the presence of a bentonite suspension. This paper presents the results obtained from 2D and 3D models of diaphragm wall construction using COMSOL Multiphysics. The CFD model helped in solving a multifluid and particularly a two-phase flow. The 2D modeling has considered a fresh slurry and an exfiltrated (or polluted) suspension neighboring soil and followed concrete flow with two rheological behaviors in two reinforcement configurations. Then, 3D simulations were compared to actual experimentation results, which were undertaken to construct diaphragm walls in the laboratory. By comparing the results of the simulations to the experimental outcomes, it has been possible to validate the model. The resulting simulations could clearly explain the occurrence of the pathology where the flow pattern and volume fraction of the fluid flow were determined. From the results obtained, it can be conducted that a compliant concrete mix but at the lower limit for the consistency recommendations, leads to pathologies, just like a polluted slurry.

Due to high reactivity and relatively low cost, nano zero-valent iron (nZVI) has become an alternative material for in-situ remediation of contaminated sites. However, factors such as short transport distance and easy deposition in porous media also seriously restrict its injection remediation effect. The optimum ratio of bentonite and kaolin supported nano zero-valent iron (K-nZVI) in the remediation agent was determined by sedimentation and rheological tests. The transport characteristics of deionized water and bentonite suspensions carrying K-nZVI in porous media under different injection pressures were investigated using simulating column tests. The results show that bentonite suspensions could significantly improve the stability and dispersibility of K-nZVI. The proportion of bentonite and K-nZVI are 5% and 0.4%, respectively, which is the best ratio of the remediation agent. The transport capability of K-nZVI carried by deionized water increases with the increase of injection pressure, while there is a critical injection pressure for bentonite suspensions carrying K-nZVI remediation agent. The numerical simulation results show that the diffusion radius of K-nZVI is positively correlated with the injection pressure and negatively correlated with the viscosity of the remediation agent. The results provide theoretical guidance for the remediation project of heavy metal pollution in non-ferrous smelting sites.