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Failure and Deformation Behavior of Underground Geo-Structures: Advances in Geomechanics

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A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Civil Engineering".

Deadline for manuscript submissions: closed (31 January 2024) | Viewed by 18556

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Special Issue Editors

Dr. Chiara Deangeli

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Guest Editor

Department of Environment, Land and Infrastructure Engineering, Politecnico di Torino, 10129 Turin, Italy
Interests: mechanical response of rock and soil in engineering applications: wellbore stability in transversely isotropic rocks at large depth; effect of pore fluid pressure on rock failure during drilling/excavation; behavior of porous rocks during hydrocarbon production and gas storage; stability of rock caverns used in gas storage; slope stability under climate change effect

Dr. Marco Barla

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Guest Editor

Department of Structural, Geotechnical and Building Engineering-DISEG, Politecnico di Torino, 10129 Turin, Italy
Interests: geotechnical engineering; geothermal energy; numerical analysis; rock mechanics; tunnelling

Dr. Donatella Valeria Sterpi

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Guest Editor

Department of Civil and Environmental Engineering, Politecnico di Milano, 20133 Milan, Italy
Interests: geotechnical engineering; shallow geothermal energy; tunnelling; laboratory experimental procedures; numerical and physical modeling

Special Issue Information

Dear Colleagues,

Underground engineering has rapidly grown to meet the increasing societal needs and is moving towards challenging innovations.

Mining and energy geomechanics is presently facing complex underground conditions related to uncertainties in the determination of rock strength and deformability, in situ stresses, and pore fluid pressure coupled with problems induced by high stresses at large depths. Furthermore, the processes related to CO₂ sequestration and storage require specific analysis of the rock geomechanical response induced by the geochemical reactions.

On the other hand, the need for transport efficiency in urban areas is presently addressing the construction of tunnels at narrow distances and the underground space use requires an appropriate analysis of rock damage for safety during service.

Civil, nuclear, and hydropower underground spaces, mines, wellbores for hydrocarbon production and gas storage, and geothermal energy extraction are subject to adverse factors during construction and service. Unexpected rock failures and excessive deformations can reduce or inhibit the engineering function of these works. The mitigation of these events includes post-disaster analysis in order to refocus the efforts on measures to reduce preventable failures and collapses, coupled with experimental approaches, analytical and numerical analysis, and data-driven techniques.

This Special Issue aims at constructing a channel for sharing knowledge on recent advances in Geomechanics to mitigate adverse events and to address challenges and potential solutions for the sustainable and resilient construction of underground geo-structures.

Dr. Chiara Deangeli
Dr. Marco Barla
Dr. Donatella Valeria Sterpi
Guest Editors

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Keywords

deep mining and energy geomechanics
CO₂ storage
civil tunnels and spaces
unexpected rock failures and excessive deformations
preventable failures and collapses
refocus for a better engineering practice
experimental, analytical and numerical approaches
data-driven techniques
sustainable and resilient underground constructions

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Published Papers (12 papers)

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Editorial

Jump to: Research

8 pages, 179 KiB

Open AccessEditorial

Failure and Deformation Behavior of Underground Geo-Structures: Advances in Geomechanics

by Chiara Deangeli, Marco Barla and Donatella Sterpi

Appl. Sci. 2024, 14(11), 4526; https://doi.org/10.3390/app14114526 - 25 May 2024

Viewed by 928

Abstract

Underground geo-structures play a crucial role in various aspects of modern society for several reasons [...] Full article

(This article belongs to the Special Issue Failure and Deformation Behavior of Underground Geo-Structures: Advances in Geomechanics)

Research

Jump to: Editorial

16 pages, 12499 KiB

Open AccessArticle

Improvements in Rock Mass Description for Stope Design by Geophysical and Geochemical Methods

by Mikael Rinne, Mateusz Janiszewski, Sebastian Pontow, Lauri Uotinen, Risto Kiuru, Lasse Kangas, Ilkka Laine and Jussi Leveinen

Appl. Sci. 2024, 14(3), 957; https://doi.org/10.3390/app14030957 - 23 Jan 2024

Viewed by 1201

Abstract

Stope design is an important part of mine planning, and it aims to balance ore recovery, ore dilution, and production costs without compromising the safety aspects. This paper summarizes the main results from the research, which aims to introduce new techniques to describe the ore body and surrounding rock mass at the tunnel face prior to stope excavation. The research comprises a literature review and a survey among mining professionals to assess current stope design practices. The study identifies geotechnical data, software improvements, and integration of design into mine planning as the most critical areas for improvement. The empirical part of the study proposes new techniques for fast data acquisition. The laser-induced breakdown spectrometry (LIBS) technique is developed for measurements at the tunnel face and from core boxes to provide mineralogical and geometallurgical data. Ground-penetrating radar (GPR) studies are conducted to improve discontinuity characterization, and rapid photogrammetric methods are proposed for efficient tunnel geometry characterization. The techniques discussed in this paper already have many industrial applications. This study reveals their potential to be adopted and further developed to serve ore and rock mass characterization for stope design. Full article

(This article belongs to the Special Issue Failure and Deformation Behavior of Underground Geo-Structures: Advances in Geomechanics)

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15 pages, 10570 KiB

Open AccessArticle

Application of a Finite-Discrete Element Method Code for Modelling Rock Spalling in Tunnels: The Case of the Lyon-Turin Base Tunnel

by Daniele Martinelli and Alessandra Insana

Appl. Sci. 2024, 14(2), 591; https://doi.org/10.3390/app14020591 - 10 Jan 2024

Cited by 5 | Viewed by 1435

Abstract

Brittle failure, or spalling, occurs around openings excavated in hard rock masses with high in situ stresses. It takes place due to the nucleation and growth of cracks around the excavation boundary, induced by the redistribution of stresses following the excavation. Modelling this failure process is a tough challenge. The hybrid finite-discrete element method (FDEM) can overcome the boundary between continuum and discontinuum, capturing emergent discontinuities associated with brittle fracturing processes. In this study, FDEM is applied using a commercial code to show its applicability to model brittle behaviour around deep underground excavations in the case of the Torino-Lyon Base tunnel in three different stress conditions. Except for the hydrostatic condition, cracking is triggered immediately after the excavation. Spalling occurring around the tunnel is quite extended; therefore, an accurately designed support must be installed to prevent blocks from falling from the tunnel boundary. The obtained results are aligned with previous results existing in the literature. However, in this case, a deeper spalling is caused by the shape change due to the gradual stress redistribution. Such a phenomenon underlines the importance of using a code able to identify crack propagation, opening, and the formation of loose blocks that progressively modify the tunnel contour. Full article

(This article belongs to the Special Issue Failure and Deformation Behavior of Underground Geo-Structures: Advances in Geomechanics)

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29 pages, 11546 KiB

Open AccessArticle

Sensitivity Analysis of Wellbore Mud Pressure towards Anisotropic Shale Properties, Pore Fluid Pressure and Far Field Stresses

by Chiara Deangeli, Wenjie Liu and Ke Yang

Appl. Sci. 2024, 14(1), 148; https://doi.org/10.3390/app14010148 - 23 Dec 2023

Cited by 1 | Viewed by 1072

Abstract

The paper investigates the mud pressure to maintain the stability of wellbores drilled in transversely isotropic shale through sensitivity analyses, carried out with analytical and numerical modeling (FLAC). To this end, we interpreted the anisotropic strength of the Tournemire shale with the Weakness Plane Model (WPM) and the modified Hoek–Brown criterion (HBm). The sensitivity analyses of synthetic case studies indicated a different trend in mud pressure for the two criteria. In some cases, the WPM predicts mud pressures higher than those predicted by the HBm and vice versa. The mud pressures predicted by the HBm resulted in being more sensitive to the increase in the anisotropy of the far field stresses for all the inclinations of the weakness planes. In this context, the WPM predicts some anomalous low mud pressures in a wide range of inclinations of the weak planes. The change in the frictional component of strength decreases with an increase in the pore fluid pressure for both criteria. The mud pressure predicted by the WPM resulted in being more sensitive to the change in frictional strength. The change in trend of the two criteria with change in input data suggests caution in the “a priori” selection of the strength criterion. A simple solution is proposed to predict a safe and reliable mud pressure with a small number of lab tests. Full article

(This article belongs to the Special Issue Failure and Deformation Behavior of Underground Geo-Structures: Advances in Geomechanics)

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19 pages, 8704 KiB

Open AccessArticle

Numerical Modeling and Back-Analysis Approach on a Monitored Underground Cavern for the Extraction of Marble for Ornamental Uses

by Pierpaolo Oreste, Claudio Oggeri, Francesco Canali and Marco Scolari

Appl. Sci. 2023, 13(23), 12893; https://doi.org/10.3390/app132312893 - 1 Dec 2023

Cited by 2 | Viewed by 836

Abstract

The Cava Madre of Candoglia represents an important underground rock cavern in the northwest of Italy, both for historical reasons and for the material that is extracted there: the marble for the continuous reconstruction and renovation works of the Milan Cathedral. Over time, the cavern reached considerable dimensions, and the existing state of stress (considerable horizontal stresses) required the creation of impressive structures to contrast and support the side walls. A complex and effective monitoring system guarantees the continuous control of the cavern. To improve the reliability of the geomechanical characterization and, therefore, of the numerical model that allows the analysis of the stress and strain behavior of the cavern, a back-analysis was developed. This allowed us to “calibrate” the two geomechanical parameters on which there was the greatest uncertainty: the elastic modulus of the marble at the scale of the problem and the lateral thrust coefficient at rest (k₀). Finally, the numerical model made the results of the back-analysis more effective, allowing us to verify the support and contrast structures of the walls and to proceed with a careful definition of the project relating to future mining works for the continuation of the exploitation of the existing marble bench. Full article

(This article belongs to the Special Issue Failure and Deformation Behavior of Underground Geo-Structures: Advances in Geomechanics)

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19 pages, 8710 KiB

Open AccessArticle

Analysis of Deformations of the Tunnel Excavation Face via Simplified Calculation Methods

by Alireza Kalantar and Pierpaolo Oreste

Appl. Sci. 2023, 13(23), 12683; https://doi.org/10.3390/app132312683 - 26 Nov 2023

Viewed by 1355

Abstract

The stability of the excavation face during the excavation of a tunnel is necessary to safeguard the lives of workers and to guarantee regular and rapid progress of the works. In this paper, the stability conditions of the tunnelling face were analysed using simplified numerical calculation methods (one-step approach) and analytical methods, in order to evaluate the extrusion of the tunnelling face as a representative quantity of the mechanical behaviour of the rock ahead of it. A comparison between the numerical method and the hemispherical method was illustrated, which was able to demonstrate how the latter can be used with high reliability in this type of study. An extensive parametric analysis of the typical conditions encountered in the excavation of tunnels in weak rock made it possible to determine the extent of the face extrusion and the effect on it of the main considered geometric and geomechanical parameters. Thanks to the comparison of the extrusion values obtained from the calculation with the limit value indicated by the scientific literature, it is possible to arrive at a rapid assessment on the stability of the face. A specific study on the role of the pressure applied to the face on the extent of the extrusion then made it possible to understand how to proceed to define the intensity of the main stabilisation systems (TBM thrust and longitudinal fiberglass bolts) to avoid the risk of collapse of the excavation face. Full article

(This article belongs to the Special Issue Failure and Deformation Behavior of Underground Geo-Structures: Advances in Geomechanics)

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14 pages, 3515 KiB

Open AccessArticle

Application of Bonded-Block Models to Rock Failure Analysis

by José V. Lemos

Appl. Sci. 2023, 13(22), 12207; https://doi.org/10.3390/app132212207 - 10 Nov 2023

Cited by 2 | Viewed by 1215

Abstract

Discrete element models are being increasingly applied to model rock failure processes. Bonded-particle models, based on circular or spherical particle systems, have been successfully used for two decades. More recently, bonded-block models, using polygonal or polyhedral elements, have proven to be a powerful alternative. This paper describes the basis of the application of these models in the numerical simulation of failure in rock materials. The critical governing parameters are identified, and their influence is discussed. The model calibration procedure based on the analysis of laboratory tests is discussed. An application example of an underground excavation problem is presented using a simple bonded-block model employing rigid blocks and a bilinear softening contact model. The results show the capability of this approach to reproduce observed failure modes involving block fractures. Full article

(This article belongs to the Special Issue Failure and Deformation Behavior of Underground Geo-Structures: Advances in Geomechanics)

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19 pages, 9424 KiB

Open AccessArticle

Feasibility Assessment of Acid Gas Injection in an Iranian Offshore Aquifer

by Marilena Cardu, Oveis Farzay, Ali Shakouri, Seyedyasin Jamali and Seyedkhashayar Jamali

Appl. Sci. 2023, 13(19), 10776; https://doi.org/10.3390/app131910776 - 28 Sep 2023

Viewed by 975

Abstract

Acid gas injection operations function as the commercial equivalent of certain aspects within the realm of geological CO₂ storage. Acid gas, composed of H₂S and CO₂, alongside minor quantities of hydrocarbon gases stemming from either petroleum production or processing, constitute the composition of acid gas. The primary aim of acid gas injection operations lies in the disposal of H₂S. Nevertheless, substantial volumes of CO₂ are concurrently injected due to the economic impracticality of segregating the two gases. This investigation delves into the comprehensive, step-by-step procedure that can be employed to determine the suitability of a field or formation for acid gas injection, utilizing all accessible data, including the literature and data from neighboring fields. This approach incorporates sensitivity analysis of various parameters to ascertain the feasibility of AGI while minimizing costs and time consumption. The focus of this study centers on evaluating the feasibility of Acid Gas Injection (AGI) in a saline aquifer offshore in Iran. The assessment encompasses the examination of reservoir properties, geomechanical aspects, caprock integrity, and gas plume dynamics. The Surmeh formation emerges as a promising candidate for AGI due to the presence of upper dolomite and lower carbonate within the rock formations. Geomechanical analysis reveals a pore pressure of 3800 psi and a fracture pressure of 6100 psi. Caprock integrity, particularly within the Hith formation, emerges as pivotal for both containment and long-term stability. Seismic mapping highlights variations in caprock thickness, influencing containment effectiveness. Capillary trapping emerges as a significant factor in short-term gas entrapment and plume distribution. Numerical simulations elucidate the impact of heterogeneous rock properties on capillary trapping and gas plume movement. The projection estimates approximately 2 TCF (Trillion Cubic Feet) of acid gas injection into the Surmeh formation. Based on the acid gas content and the gas in place at the source of injection, the recommended injection rate stands at 180 MMSCFD (million standard cubic feet per day). The formation’s inherent tightness limits injectivity, allowing for a maximum achievable rate of 7 MMSCFD with a permeability of 1 mD (millidarcy). However, a higher porosity (12%) and a permeability of 100 mD enable more efficient injection without fracturing the formation. To achieve this, it becomes imperative to implement two injection wells, each with a capacity of 90 MMSCFD. Full article

(This article belongs to the Special Issue Failure and Deformation Behavior of Underground Geo-Structures: Advances in Geomechanics)

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13 pages, 1579 KiB

Open AccessArticle

Feasibility Study of Controlled-Source Electromagnetic Method for Monitoring Low-Enthalpy Geothermal Reservoirs

by Mahmoud Eltayieb, Dieter Werthmüller, Guy Drijkoningen and Evert Slob

Appl. Sci. 2023, 13(16), 9399; https://doi.org/10.3390/app13169399 - 18 Aug 2023

Cited by 1 | Viewed by 1472

Abstract

Tracking temperature changes by measuring the resulting resistivity changes inside low-enthalpy reservoirs is crucial to avoid early thermal breakthroughs and maintain sustainable energy production. The controlled-source electromagnetic method (CSEM) allows for the estimation of sub-surface resistivity. However, it has not yet been proven that the CSEM can monitor the subtle resistivity changes typical of low-enthalpy reservoirs. In this paper, we present a feasibility study considering the CSEM monitoring of 4–8

Ω \cdot

m resistivity changes in a deep low-enthalpy reservoir model, as part of the Delft University of Technology (TU Delft) campus geothermal project. We consider the use of a surface-to-borehole CSEM for the detection of resistivity changes in a simplified model of the TU Delft campus reservoir. We investigate the sensitivity of CSEM data to disk-shaped resistivity changes with a radius of 300, 600, 900, or 1200 m at return temperatures equal to 25, 30, …, 50 °C. We test the robustness of CSEM monitoring against various undesired effects, such as random noise, survey repeatability errors, and steel-cased wells. The modelled differences in the electric field suggest that they are sufficient for the successful CSEM detection of resistivity changes in the low-enthalpy reservoir. The difference in monitoring data increases when increasing the resistivity change radius from 300 to 1200 m or from 4 to 8

Ω \cdot

m. Furthermore, all considered changes lead to differences that would be detectable in CSEM data impacted by undesired effects. The obtained results indicate that the CSEM could be a promising geophysical tool for the monitoring of small resistivity changes in low-enthalpy reservoirs, which would be beneficial for geothermal energy production. Full article

(This article belongs to the Special Issue Failure and Deformation Behavior of Underground Geo-Structures: Advances in Geomechanics)

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20 pages, 12884 KiB

Open AccessArticle

Interaction of Segmental Tunnel Linings and Dip-Slip Faults—Tabriz Subway Tunnels

by Asma Ramesh, Alireza Rashiddel, Mohsen Hajihassani, Daniel Dias and Majid Kiani

Appl. Sci. 2023, 13(13), 7866; https://doi.org/10.3390/app13137866 - 4 Jul 2023

Cited by 2 | Viewed by 3828

Abstract

In some subsurface urban development projects, bedrock faults intersecting with the tunnel path are inevitable. Due to the high costs of urban tunnel projects, it is necessary to study the behavior of such concrete structures under fault movement risks. Using an advanced 3D numerical finite difference code and a plastic hardening constitutive model for the soil, this paper examined the performance of the straight and oblique segmented structures of Tabriz Subway Line 2 under large deformations. The Tabriz Line 2 tunnel passes through a reverse fault called the Baghmisheh Fault. The fault–tunnel simulations were validated by centrifuge tests on the segmental tunnel for normal faulting. In the centrifuge tests and validation models, there was a maximum difference of 15%. According to the results of the Tabriz Line 2 tunnel under reverse faulting, segmental structures outperform no-joint linings when it comes to fault movement. During reverse fault movement, line 2 segments did not collapse but showed slight deformations. However, continuous structures collapsed under faulting, i.e., the structural forces created exceeded the section strength capacity. Among the segmental structures, the lining with oblique joints showed better behavior against faulting than the lining with straight joints. For better tunnel performance under fault movement, oblique joints should be used in segmental structures in faulting areas. Full article

(This article belongs to the Special Issue Failure and Deformation Behavior of Underground Geo-Structures: Advances in Geomechanics)

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17 pages, 7618 KiB

Open AccessArticle

Application of Image Processing in Evaluation of Hydraulic Fracturing with Liquid Nitrogen: A Case Study of Coal Samples from Karaganda Basin

by Sotirios Nik. Longinos, Azza Hashim Abbas, Arman Bolatov, Piotr Skrzypacz and Randy Hazlett

Appl. Sci. 2023, 13(13), 7861; https://doi.org/10.3390/app13137861 - 4 Jul 2023

Cited by 16 | Viewed by 1420

Abstract

Research of microstructure and permeability evolution of coal following LN₂ treatment elucidate the process of cryogenic fracturing due to environmentally friendly behavior in comparison with conventional hydraulic fracturing. The evolution of the 2D microstructure of bituminous coal before and after LN₂ treatment was examined using a high-resolution camera. The image processing was implemented using functions from the OpenCV Python library that are sequentially applied to digital images of original coal samples. The images were converted into binary pixel matrices to identify cracks and to evaluate the number of cracks, crack density, total crack area, and average crack length. Results were visualized using Seaborn and Matplotlib Python libraries. There were calculations of total crack area (TCA), total number of cracks (TNC), crack density (CD), the average length of cracks (Q2), first (Q1) and third (Q3) quartiles in fracture length statistics. Our findings demonstrate a progressive increase in the Total Crack Area (δTCA) with longer freezing times and an increased number of freezing–thawing cycles. In contrast, the change in crack density (δCD) was generally unaffected by freezing time alone but exhibited a significant increase after several freezing–thawing cycles. Among the freezing times investigated, the highest crack density (CD) value of 300 m⁻¹ was achieved in FT60, while the lowest CD value of 31.25 m⁻¹ was observed in FT90 after liquid nitrogen (LN2) treatment. Additionally, the FTC4 process resulted in a 50% augmentation in the number of cracks, whereas the FTC5 process tripled the number of small cracks. Full article

(This article belongs to the Special Issue Failure and Deformation Behavior of Underground Geo-Structures: Advances in Geomechanics)

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15 pages, 7128 KiB

Open AccessArticle

Influence of Preconditioning and Tunnel Support on Strain Burst Potential

by Adeline Delonca, Francisco Gonzalez, Victor Mendoza and Andrea Ceron

Appl. Sci. 2023, 13(13), 7419; https://doi.org/10.3390/app13137419 - 22 Jun 2023

Cited by 1 | Viewed by 1513

Abstract

Strain burst hazard is one of the main challenges that faces deep underground environments. To manage it, it is needed to assess its probability occurrence (or potential). Various methods have been proposed over the years to assess the phenomenon early on. However, due to uncertainties in rock mass properties and the physical processes of the phenomenon, mitigation measures are an additional important line of defense to ensure workplace safety. While work has been carried out to assess the rockburst hazard better and improve support systems, the effect of mitigation measures on strain burst hazard potential is unclear. This paper studies the influence of the implementation of shotcrete and rockbolts support and destress blasting in tunnels on strain burst potential, based on two-dimensional numerical models of circular tunnels. The results highlight that, as expected, the use of mitigation measures allows the strain burst occurrence to decrease. However, the strain burst hazard level does not decrease easily, even when using mitigation measures. In the case of serious overbreak hazards, only a combination of system support and destress blasting seems to have an impact on these events, and not for all the simulated cases. Full article

(This article belongs to the Special Issue Failure and Deformation Behavior of Underground Geo-Structures: Advances in Geomechanics)

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