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17 pages, 13988 KiB

Open AccessArticle

Numerical Modelling and Sensitivity Analysis of the Pitztal Valley Debris Flow Event

by Mohammad Wasif Naqvi, Diwakar Kc and Liangbo Hu

Geosciences 2023, 13(12), 378; https://doi.org/10.3390/geosciences13120378 - 11 Dec 2023

Cited by 1 | Viewed by 1853

Debris flows characterized by their rapid velocity and composition of water, mud, soil, and boulders, have the potential to inflict significant harm and present hazards to human life, infrastructure, and the natural surroundings. Numerical simulations provide a cost-effective approach for investigating different scenarios, [...] Read more.

Debris flows characterized by their rapid velocity and composition of water, mud, soil, and boulders, have the potential to inflict significant harm and present hazards to human life, infrastructure, and the natural surroundings. Numerical simulations provide a cost-effective approach for investigating different scenarios, hence boosting comprehension of flow dynamics and interactions. However, accurate modelling of these flows typically face difficult challenges arising from inherent modeling constraints and insufficient historical event data. The primary objective of the present study is to conduct numerical modeling and sensitivity analysis of the debris flow event that occurred in the Pitztal Valley, Austria in August of 2009, based on a multi-phase model for debris flows. The validation of the simulation results involves the comparison with the observed deposition patterns in the field. Various validation factors are employed to evaluate the accuracy of the simulated deposit and demonstrate a satisfactory level of precision in predicting deposition patterns. A sensitivity analysis is also conducted to examine the influence of in situ conditions on the effects of debris flow. The results demonstrate that numerical modelling can play an important role in engineering hazard assessment by analyzing the existing model’s effectiveness in simulating both historical and projected debris flow events. Full article

(This article belongs to the Special Issue Advanced Numerical Modelling and Analysis in Geotechnical Engineering)

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21 pages, 70941 KiB

Open AccessArticle

Numerical Simulation of Rockfall Protection Embankments in Natural Soil

by Stefano Vigna, Maddalena Marchelli, Valerio De Biagi and Daniele Peila

Geosciences 2023, 13(12), 368; https://doi.org/10.3390/geosciences13120368 - 28 Nov 2023

Cited by 3 | Viewed by 1863

Abstract

Rockfall events represent a significant hazard in mountainous regions, putting human safety and critical infrastructure at risk. Various mitigation devices are available, among which, Rockfall protection embankments (RPEs) located in natural soil are passive defense work suitable for high-energy and high-frequency events. Currently, [...] Read more.

Rockfall events represent a significant hazard in mountainous regions, putting human safety and critical infrastructure at risk. Various mitigation devices are available, among which, Rockfall protection embankments (RPEs) located in natural soil are passive defense work suitable for high-energy and high-frequency events. Currently, limited research has been conducted in this area, with the Austrian standard ONR 24810 providing the sole codified design method. A parametrical analysis involving both the RPE geometry and the impact features was developed by Abaqus/Explicit FEM code, with 2270 cases overall. The research aims to identify conditions under which RPEs effectively stop falling blocks, focusing on two failure mechanisms: the block pass over the RPE after impacting the upstream side bank and the RPE structural collapse. Additionally, the interaction between RPEs and their foundations during the impact is explored. The results provide valuable insights into the dynamic behavior of these structures. In terms of design considerations, this study offers analytical equations to quantify crater depth and foundation stress induced by the impact. Furthermore, design charts are developed to assess the block passing over verification and the structural collapse verification. Full article

(This article belongs to the Special Issue Advanced Numerical Modelling and Analysis in Geotechnical Engineering)

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20 pages, 5115 KiB

Open AccessArticle

Influence of Localized Rainfall Patterns on Landslide Occurrence—A Case Study of Southern Hiroshima with eXtended Radar Information Network Data during the July 2018 Heavy Rain Disasters

by José Maria dos Santos Rodrigues Neto and Netra Prakash Bhandary

Geosciences 2023, 13(8), 245; https://doi.org/10.3390/geosciences13080245 - 14 Aug 2023

Cited by 2 | Viewed by 1776

Abstract

In this study, we use GIS and other analytical platforms to analyze the landslide distribution pattern in the July 2018 heavy rain disasters in the southern part of Hiroshima Prefecture in Japan in conjunction with chronological XRAIN (eXtended Radar Information Network) radar-acquired localized [...] Read more.

In this study, we use GIS and other analytical platforms to analyze the landslide distribution pattern in the July 2018 heavy rain disasters in the southern part of Hiroshima Prefecture in Japan in conjunction with chronological XRAIN (eXtended Radar Information Network) radar-acquired localized rainfall data in order to better understand the relationship between rainfall characteristics and landslide probability. An analysis of event rainfall from the July 2018 disasters determines that landslide-inducing rainfall started from 8:30 AM on 5 July and continued until 7:30 AM on 7 July, accumulating to up to 368 mm in total precipitation, and that there were two intensity peaks, one around 7:30 PM on 6 July, and another one around 4:30 AM on 7 July. These two events are associated with particularly high landslide activity, which indicates that landslide activation is related to peak-intensity rainfall combined with accumulated continuous precipitation. The XRAIN data were also used together with landslide reports to calculate the intensity–duration (i.e., I-D) rainfall threshold for the area. The mean annual precipitation in the whole study area ranged between 2025 mm and 3030 mm, with an average value of about 2300 mm. The spatial distribution of rainfall throughout the sampled years indicates that rainfall is remarkably localized, with higher values concentrated on elevated areas. However, it was also observed that the maximum precipitation volumes are not so closely related to landslide occurrence, and the highest landslide activity was found in intermediate precipitation class zones instead. Correlating the localization patterns of event precipitation and mean annual precipitation using Pearson’s correlation coefficient, we found an r value of 0.55, which is considered a moderate correlation between the two datasets (i.e., event precipitation and mean annual precipitation). Full article

(This article belongs to the Special Issue Advanced Numerical Modelling and Analysis in Geotechnical Engineering)

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27 pages, 10435 KiB

Open AccessArticle

Tunnelling with Full-Face Shielded Machines: A 3D Numerical Analysis of an Earth Pressure Balance (EPB) Excavation Sequence Using the Finite Element Method (FEM)

by Jonathan Tyrer, Chrysothemis Paraskevopoulou, Ravi Shah, Richard Miller and Michael Kavvadas

Geosciences 2023, 13(8), 244; https://doi.org/10.3390/geosciences13080244 - 12 Aug 2023

Cited by 2 | Viewed by 2341

Abstract

Urban tunnelling can be highly challenging, especially in areas where limited ground settlements and environmental disturbance is required. Mechanised tunnelling is usually preferred in such ground environments, specifically Slurry or EPBM (Earth Pressure Balance Machine), depending on the ground properties. Being able to [...] Read more.

Urban tunnelling can be highly challenging, especially in areas where limited ground settlements and environmental disturbance is required. Mechanised tunnelling is usually preferred in such ground environments, specifically Slurry or EPBM (Earth Pressure Balance Machine), depending on the ground properties. Being able to predict the anticipated tunnel behaviour at the preliminary stages of the project can be very beneficial in optimising not only the design, but also control the construction activities and completion times. In practice, the short-term excavation response and support performance focus primarily on design, since most site characterisation inputs are focused on material properties gained from short-term testing. Although the analysis of tunnelling is a three-dimensional (3D) problem, conventional approaches and design methods employed during the design and construction of underground openings are often based on the ground’s static response in two dimensions (2D). In this paper, an initial 2D model is generated in PLAXIS2D and RS2 (Rocscience) to test advanced constitutive models and compare transverse settlement profiles; subsequently, a complete 3D FEM numerical model in RS3 (Rocscience) was used to simulate an Earth Pressure Balance (EPB) excavation sequence. The 3D numerical model simulates the relevant EPB components such as face pressure, TBM shield, backfilling of the tail void (time-dependent hardening of the grout) and gradual segmental lining erections in the longitudinal direction. The presented numerical approach can be used by tunnel designers and engineers to predict the soil response in EPBM tunnelling. Full article

(This article belongs to the Special Issue Advanced Numerical Modelling and Analysis in Geotechnical Engineering)

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21 pages, 5011 KiB

Open AccessArticle

FEM Modelling of Thin Weak Layers in Slope Stability Analysis

by Roberto Valentino

Geosciences 2023, 13(8), 233; https://doi.org/10.3390/geosciences13080233 - 6 Aug 2023

Viewed by 1367

Abstract

Modelling the presence and the effect of a thin weak layer of soil or rock in a slope stability analysis performed through the finite element method (FEM) presents several problems of purely numerical nature. This paper deals with a parametric analysis of three [...] Read more.

Modelling the presence and the effect of a thin weak layer of soil or rock in a slope stability analysis performed through the finite element method (FEM) presents several problems of purely numerical nature. This paper deals with a parametric analysis of three different 2D numerical case studies (both ideal and real) of unstable or potentially unstable slopes containing a thin soft band (or weak layer). The FEM software used is RS2 (Rocscience^®). The aim is investigating the influence of some geometrical and numerical characteristics of the soft bands in the stability analyses. The Mohr–Coulomb elastic-perfectly plastic constitutive model for all the involved materials was assumed, and the mechanical parameters were kept constant. Instead, other fundamental parameters of the weak layer, such as the type of mesh elements, the mesh density, and the geometry, in terms of both thickness and outcrop shape, were changed, and results in terms of the critical Strength Reduction Factor (SRF) were compared. The main outcomes of this study represent practical suggestions on some numerical and technical aspects to users of FEM slope stability analyses, in order to obtain a precautionary assessment of slope stability. Full article

(This article belongs to the Special Issue Advanced Numerical Modelling and Analysis in Geotechnical Engineering)

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23 pages, 22227 KiB

Open AccessArticle

Comparative Numerical Study on the Weakening Effects of Microwave Irradiation and Surface Flux Heating Pretreatments in Comminution of Granite

by Martina Pressacco, Jari Kangas and Timo Saksala

Geosciences 2023, 13(5), 132; https://doi.org/10.3390/geosciences13050132 - 3 May 2023

Cited by 1 | Viewed by 1768

Abstract

Thermal pretreatments of rock, such as conventional heating and microwave irradiation, have received considerable attention recently as a viable method of improving the energy efficiency of mining processes that involve rock fracturing. This study presents a numerical analysis of the effects of thermal [...] Read more.

Thermal pretreatments of rock, such as conventional heating and microwave irradiation, have received considerable attention recently as a viable method of improving the energy efficiency of mining processes that involve rock fracturing. This study presents a numerical analysis of the effects of thermal shock and microwave heating on the mechanical properties of hard, granite-like rock. More specifically, the aim is to numerically assess the reduction of uniaxial compressive strength of thermally pretreated specimens compared to intact ones. We also compare the performance of these two pretreatments (conventional heating and microwave irradiation) in terms of consumed energy and induced damage. Rock fracture is modelled by a damage-viscoplasticity model, with separate damage variables in tension and compression. A global solution strategy is developed for solving the thermo-mechanical problem (conventional heating) and the electromagnetic–thermo-mechanical problem (microwave heating). The electromagnetic part of the microwave heating problem is solved in COMSOL Multiphysics software Version 6.1 first. The electromagnetic solution is used as an input for the thermo-mechanical problem, which is finally solved by means of a staggered explicit solution method. Due to the predominance of the external thermal sources, the thermal and the mechanical parts of the problem in both cases are considered as uncoupled. Three-dimensional finite element simulations are utilized to study the damage-viscoplasticity model. An ore-shaped three-mineral numerical rock specimen is used in uniaxial compression tests. Full article

(This article belongs to the Special Issue Advanced Numerical Modelling and Analysis in Geotechnical Engineering)

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16 pages, 15620 KiB

Open AccessArticle

Automating the Process for Estimating Tunneling Induced Ground Stability and Settlement

by Jim Shiau, Mathew Sams, Mohammad Reza Arvin and Pornkasem Jongpradist

Geosciences 2023, 13(3), 81; https://doi.org/10.3390/geosciences13030081 - 10 Mar 2023

Cited by 1 | Viewed by 1599

Abstract

An automatic process for estimating ground stability and settlement of circular tunnels is developed for practitioners in this paper using finite difference method FLAC code. The numerical model aims to simulate the movement and relaxation of the soil around the shield and lining [...] Read more.

An automatic process for estimating ground stability and settlement of circular tunnels is developed for practitioners in this paper using finite difference method FLAC code. The numerical model aims to simulate the movement and relaxation of the soil around the shield and lining annulus that occurs due to the overcutting and grouting of the tunnel void by a tunnel boring machine. To achieve this, the model uses a pressure relaxation technique that progressively reduces the tunnel support pressure from the initial at rest condition until a point of failure is detected. At this stage, the stability number is calculated, and settlement data are exported for analysis. This is conducted for a range of geometry and soil ratios which cover most practical cases for cohesive soils. These stability numbers are then compared to rigorous upper and lower bound solutions. Using the settlement data, a trough width parameter i_x is also determined for each case using regression of the commonly used Gaussian equation. The results of this study are quite positive, with the stability results from this study remaining within 5% of the upper and lower bound solutions; settlement results also compare well with previous experimental and observational results. The proposed automatic process can be used effectively and efficiently in most practical design projects. Full article

(This article belongs to the Special Issue Advanced Numerical Modelling and Analysis in Geotechnical Engineering)

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23 pages, 7658 KiB

Open AccessArticle

Laboratory-Scale Investigation on Shear Behavior of Non-Persistent Joints and Joint Infill Using Lattice-Spring-Based Synthetic Rock Mass Model

by Mariam Al-E’Bayat, Taghi Sherizadeh and Dogukan Guner

Geosciences 2023, 13(2), 23; https://doi.org/10.3390/geosciences13020023 - 20 Jan 2023

Cited by 1 | Viewed by 1841

Abstract

Discontinuities mainly control the mechanical behavior of rock mass and cause a significant reduction in the rock mass strength. Joint persistency and joint infill conditions are considered the most significant joint parameters that control the mechanical response of rock mass. In this study, [...] Read more.

Discontinuities mainly control the mechanical behavior of rock mass and cause a significant reduction in the rock mass strength. Joint persistency and joint infill conditions are considered the most significant joint parameters that control the mechanical response of rock mass. In this study, numerical and statistical analyses were performed on pre-cracked specimens with two flaws to investigate the effect of joint persistence parameters on shear strength. In addition, an extensive study was conducted to explore the effect of infilled mineral strength, infill thickness, and infill wall roughness on shear strength. The Lattice-Spring-Based Synthetic Rock Mass (LS-SRM) approach was utilized to perform the numerical models. The results showed that the tensile crack propagation is limited at higher normal stresses as tensile damage is largely suppressed. The increases in rock bridge angle slightly increased the shear strength and caused a change in the failure mechanisms of the rock bridge from tensile to shearing. The results of the models with infilled minerals revealed that infilled minerals mainly controlled the shear strength of specimens when the infill thickness was 4.0 mm or greater. The infill wall roughness had no apparent effect on the shear strength. In contrast, it governed the failure mechanisms; cracks initiated at the asperity of the rough filling wall and propagated through the hosted rock mass. Full article

(This article belongs to the Special Issue Advanced Numerical Modelling and Analysis in Geotechnical Engineering)

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