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Structural Geology, Rock Mechanics and Their On-Site Testing Analysis

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

Deadline for manuscript submissions: closed (20 February 2023) | Viewed by 18797

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Prof. Dr. Nuwen Xu

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Guest Editor

State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource and Hydropower, Sichuan University, Chengdu 610065, China
Interests: rock mechanics
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Biao Li

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Assistant Guest Editor

School of Geoscience and Technology, Southwest Petroleum University, Chengdu 610500, China
Interests: underground engineering; microseismic monitoring; rock mechanics

Special Issue Information

Dear Colleagues,

As the social economy develops, construction of civil and infrastructure projects is in a great demand all over the world. The safety of geotechnical engineering has been a hot topic. To assess the stability of engineering rock mass, many researchers have been working on structural geology, rock mechanics and their experiments and monitoring. In the past few decades, various methods and techniques have been developed and applied to geotechnical engineering, which have provided significant references for engineering construction.

Due to the significance of engineering construction, many researchers are still working hard to develop better theories, methods and techniques used in rock mechanics and rock engineering. Research results are of both scientific and practical significance on rock mechanics and rock engineering. In this Special Issue, the recent efforts and advances made for structural geology, rock mechanics and their experiments and monitoring will be discussed. The topics of interest for this Special Issue include but are not limited to the following:

Dep rock mechanics and engineering
Mechanism, monitoring and forecasting of rockburst
Geostress characteristics and monitoring technology
Rock slope stability analysis and safety evaluation
Deep and long tunnel construction method and monitoring
Microseismic monitoring and its theory, method and technology
Application of artificial intellegent in rock mechanics and structural geology
Application of big data and cloud computing in rock mechanics
New development of real time monitoring, early warning, and risk assessment methods for rock mechanics and structural geology

Prof. Dr. Nuwen Xu
Prof. Dr. Biao Li
Guest Editors

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Keywords

rock mechanics
Deep rock mechanics
physical experiments
numerical simulation
in-situ monitoring
deep learning
big data
cloud computing

Published Papers (9 papers)

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15 pages, 2404 KiB

Open AccessArticle

Identification of Impact Frequency for Down-the-Hole Drills Using Motor Current Signature Analysis

by Diego Brito, René Gómez, Gonzalo Carvajal, Lorenzo Reyes-Chamorro and Guillermo Ramírez

Appl. Sci. 2023, 13(8), 4650; https://doi.org/10.3390/app13084650 - 7 Apr 2023

Cited by 1 | Viewed by 2466

Abstract

In rotary-percussion drilling, the impact frequency is a crucial variable that is closely linked to operational factors that determine the efficacy of the drilling process, such as the rate of penetration, bit wear, and rock mass characteristics. Typical identification methods rely on complex simulation models or the analysis of different sensor signals installed on specially adapted setups, which are difficult to be implemented in the field. This paper presents a novel study where the impact frequency is identified by motor current signature analysis (MCSA) applied to an induction motor driving a DTH drilling setup. The analysis of the case study begins with the definition of characteristic drilling stages where the pressure and sound signals allow the detection of an impact frequency of 14.10 Hz, which is then used as a reference to validate three MCSA identification approaches. As a result of the analysis, the envelope approach is the most robust for nearly real-time implementations considering its simplicity and range of coverage. Experimental results provide evidence about the feasibility of the proposed MCSA methods to be integrated into Measurement-While-Drilling (MWD) systems to improve drilling condition monitoring and rock mass characterization. Full article

(This article belongs to the Special Issue Structural Geology, Rock Mechanics and Their On-Site Testing Analysis)

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15 pages, 14234 KiB

Open AccessArticle

Research on Mechanical Properties and Failure Mode of Conglomerate Based on Discrete Element Method

by Jiawei Zhang, Xiangjun Liu, Jian Xiong, Lixi Liang and Wen Zhang

Appl. Sci. 2023, 13(1), 223; https://doi.org/10.3390/app13010223 - 24 Dec 2022

Cited by 2 | Viewed by 1123

Abstract

Conglomerate reservoir is an important part of unconventional oil and gas resources, which has great developmental potential. However, its sedimentary environment and structural background are complex, and its cementation types, gravel volume fraction and shape are quite different, which leads to its strong heterogeneity. When developing a conglomerate reservoir, it is extremely difficult to drill because of its strong heterogeneity. It is difficult to obtain the mechanical properties and laws of the conglomerate through physical experiments, which further restricts the development process of conglomerate reservoirs. In order to study its failure law, a three-dimensional numerical model of a conglomerate is built based on the discrete element method, and the effects of cementation strength and gravel characteristics on the mechanical properties of the conglomerate are emphatically studied. The results show that the elastic modulus and uniaxial compressive strength of the conglomerate decrease obviously with the decrease in cementation strength. With the increase in cementation strength, the normal contact force of the conglomerate model increases significantly, the distribution of normal contact force changes from cylinder to sphere, and the heterogeneity of the conglomerate decreases. There is a threshold value for the influence of cementation strength on mechanical properties of the conglomerate, and when the threshold is exceeded, the mechanical properties of the conglomerate no longer change obviously. With the increase in gravel content, the uniaxial compressive strength of the conglomerate decreases at first and then increases, the phenomenon of penetrating gravels and bypassing gravels increases, and the single diagonal crack changes into diagonal cross cracks; the cementation strength and gravel content of gravel jointly affect the mechanical properties and fracture morphology of the conglomerate, and its stress–strain relationship is the external macroscopic expression of normal contact force of internal particles. Full article

(This article belongs to the Special Issue Structural Geology, Rock Mechanics and Their On-Site Testing Analysis)

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22 pages, 10290 KiB

Open AccessArticle

Study on Permeability Stress-Sensitivity in Seepage-Geomechanical Coupling of Fractured Deep Tight Sandstone Gas Reservoirs

by Jiecheng Song, Jianjun Liu, Rui Song and Yujia Song

Appl. Sci. 2022, 12(22), 11672; https://doi.org/10.3390/app122211672 - 17 Nov 2022

Cited by 3 | Viewed by 1461

Abstract

Accurately predicting the characteristics and influencing factors of permeability stress-sensitivity contributes to improving gas production in gas reservoirs. In this paper, the effects of effective stress on the permeability of fractured deep tight sandstone reservoirs were studied by laboratory tests. With the experimental results, a coupled seepage-geomechanical model for fractured deep tight sandstone gas reservoirs was constructed. The influences of pore pressure and geo-stress on permeability characteristics and gas production were studied by numerical simulation. The results indicate: (1) When the effective stress increases from 0 to 65 MPa, the permeability of the natural sample with fractures decreases by 81.28%, and the permeability of the intact core sample decreases by 54.67%. (2) When the pore pressure decreases from 120 to 85 MPa, the three-dimensional effective stress increases. The largest increase of the effective stress was along the vertical direction, which increased by 11~19 MPa. In addition, the permeability of the fractured zone and the intact rock along the vertical direction decreased by about 40% and 16%, respectively. (3) The mean square error between the historical gas production results and the results by simulation was 2.22 when considering the permeability stress-sensitivity, and 4.01 without considering the permeability stress-sensitivity. The proposed coupled seepage-geomechanical model with permeability stress-sensitivity proved to be more accurate in historical gas production comparison and prediction. This study provides a reliable optimization scheme for the development of fractured deep tight sandstone gas reservoirs. Full article

(This article belongs to the Special Issue Structural Geology, Rock Mechanics and Their On-Site Testing Analysis)

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14 pages, 6206 KiB

Open AccessArticle

Stability Analysis and Fracture Mechanism of Surrounding Rock in a Hydraulic Tunnel Based on Microseismic Monitoring

by Zhi Li, Haoyu Mao, Biao Li, Xiang Zhou, Guo Liao and Jianjun Chen

Appl. Sci. 2022, 12(18), 9362; https://doi.org/10.3390/app12189362 - 18 Sep 2022

Cited by 2 | Viewed by 1598

Abstract

Numerous large hydropower projects have been built, are being built, or are planned to be developed in southwest China as a result of the increasing demand for clean energy in China’s social and economic development. Based on engineering geological data, site surveys, and the temporal and spatial distribution characteristics of microseismic (MS) events, an MS monitoring system was developed in this study to analyze the stability of the surrounding rock of the spillway tunnel of the Jinchuan hydropower station as well as the fracture and damage mechanism in the concentration zone. The results of the study indicated that the distribution of MS events was correlated with the construction process and geological conditions, that the concentration of MS events and their great moment magnitude could be regarded as signs of future damage to the surrounding rock, and that the surrounding rock of the spillway tunnel primarily exhibited non-shear failure, such as tensile failure, with only a small area exhibiting shear failure. The results can be used as a construction reference and as a forewarning of surrounding rock deformation. Full article

(This article belongs to the Special Issue Structural Geology, Rock Mechanics and Their On-Site Testing Analysis)

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12 pages, 36404 KiB

Open AccessArticle

L^p-Order Time–Frequency Spectra and Its Application in Edge Detection

by Houjun Liu, Junxing Cao, Zhenhua He, Yong Li, Kai Lin and Gulan Zhang

Appl. Sci. 2022, 12(6), 2836; https://doi.org/10.3390/app12062836 - 10 Mar 2022

Viewed by 1347

Abstract

Generalized Hilbert transform (GHT) has been widely and successfully used in signal processing and interpretation for many years. However, the order parameter in GHT can only be chosen in a certain range, and the GHT result is not stable with respect to the chosen order parameter, which usually leads to poor-stability and low-resolution outputs. To improve the stability of GHT and broaden its order parameter chosen range, and finally achieve high-efficiency and high-resolution results, we extend GHT by introducing the sign function, the two frequency integration parameters, and propose the L^p-order time–frequency spectra (LTFS). In LTFS, the sign function aims to broaden the chosen range of the order parameter into any positive numbers, and then leads to high-stability and high-resolution LTFS results; the two frequency integration parameters aim to optimize the computation efficiency and output resolution of LTFS. Synthetic one-dimensional (1D) channel data testing, synthetic two-dimensional (2D) seismic data, and actual three-dimensional (3D) seismic data examples demonstrate favorable capability of LTFS for edge detection. Full article

(This article belongs to the Special Issue Structural Geology, Rock Mechanics and Their On-Site Testing Analysis)

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15 pages, 2785 KiB

Open AccessArticle

Influence of Super Absorbent Polymer on Root Characteristics and Anchorage of Amorpha fruticosa on Rocky Slope

by Shujun Hou, Hailong Sun and Yinghua Zhou

Appl. Sci. 2022, 12(5), 2640; https://doi.org/10.3390/app12052640 - 3 Mar 2022

Cited by 2 | Viewed by 1772

Abstract

Super absorbent polymer (SAP), known as a water retention agent, has a high capacity for water absorption, which can help enhance the soil structure. This paper studied the effects of SAP dosages on the root characteristics and anchorage of Amorpha fruticosa on rock slopes. The internal relationship between root growth effect and soil was discussed, and a specific reference was provided for the rational application of SAP on slopes. Using the pull-out and tensile resistance tests, we systematically studied the changes of soil properties, root distribution, root tensile strength, and root anchorage under six different SAP dosages. The results indicated that: (1) With the increase in SAP dosage, the natural soil water content and water content after 24 h of watering increased significantly, whereas the contents of TN, TP, and TK decreased dramatically. (2) With the increase in SAP dosage, the amount and length of first-order and secondary lateral roots decreased significantly, and there was no significant difference in diameter. The amount of downslope first-order and unembedded secondary lateral roots is greater than upslope. The amount of upslope embedded secondary lateral roots is greater than in downslope. (3) Tensile strength: embedded secondary root > non-embedded secondary root > first-order lateral root; upslope root > downslope root. (4) With the increase in SAP dosage, the plant anchorage drops noticeably. This study concluded that the significant addition of SAP could enhance the tensile strength of upslope embedded secondary lateral roots but would adversely affect soil nutrients, root distribution, and root anchorage. The addition of SAP in this test had no significant effect on improving slope stability. From the perspective of reinforcement capacity, we cannot blindly pursue the survival rate and other high dosage use of water retention agents to increase the risk of slope destabilization. Full article

(This article belongs to the Special Issue Structural Geology, Rock Mechanics and Their On-Site Testing Analysis)

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14 pages, 5250 KiB

Open AccessArticle

Stability Analysis of Surrounding Rock in Multi-Discontinuous Hydraulic Tunnel Based on Microseismic Monitoring

by Xiang Zhou, Biao Li, Chunming Yang, Weiming Zhong, Quanfu Ding and Haoyu Mao

Appl. Sci. 2022, 12(1), 149; https://doi.org/10.3390/app12010149 - 24 Dec 2021

Cited by 2 | Viewed by 2241

Abstract

The diversion tunnel of a hydropower station is characterized by low quality surrounding rock and weak structural planes. During excavation, rock mass spalling and cracking frequently occur. To evaluate the stability of a rock mass during tunnel excavation, high-precision microseismic monitoring technology was introduced to carry out real-time monitoring. Based on the temporal and spatial distribution characteristics of microseismic events, the main damage areas and their influencing factors of tunnel rock mass were studied. By analyzing the source characteristic parameters of the concentration area of microseismic activities, the rock fracture mechanism of the concentration area was revealed. The 3D numerical model of diversion tunnel was established, and the deformation characteristics of the rock mass under the control of different combination types of weak structural planes were obtained. The results showed that the microseismic event was active between 29 October 2020 and 6 November 2020, and the energy release increased sharply. The main damage areas of the rock mass were located at Stakes K0 + 500–K0 + 600 m. Microseismic source parameters revealed that shear failure or fault-slip failure induced by geological structures had an important influence on the stability of the surrounding rock. The numerical simulation results were consistent with the microseismic monitoring results and indicated that among the three kinds of structural plane combination types, including “upright triangle”, “inverted triangle” and “nearly parallel”, the “upright triangle” structure had the most significant influence on the stability of the surrounding rock. In addition, the maximum displacement of the surrounding rock had a trend of lateral migration to the larger dip angle in the three combined structural plane types. The research results will provide significant references for the safety evaluation and construction design of similar tunnels. Full article

(This article belongs to the Special Issue Structural Geology, Rock Mechanics and Their On-Site Testing Analysis)

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16 pages, 5965 KiB

Open AccessArticle

High-Precision and High-Resolution Synchrosqueezing Transform via Time-Frequency Instantaneous Phases

by Yong Li and Gulan Zhang

Appl. Sci. 2021, 11(24), 11760; https://doi.org/10.3390/app112411760 - 10 Dec 2021

Cited by 2 | Viewed by 2133

Abstract

Synchrosqueezing transform (SST) can effectively improve time-frequency precision and resolution by squeezing time-frequency spectra via instantaneous frequencies, and it has been applied in many diverse disciplines; however, the precision of estimated instantaneous frequencies during SST is usually affected by the time-sample interval of the inputted signal; this usually leads to low-precision or inaccurate SST results and limits its further application. To obtain high-precision and high-resolution SST results with high efficiency, we propose a high-precision and high-resolution SST via time-frequency instantaneous phases (HSST); in HSST, time-frequency instantaneous phases with period-jumps removal are used for high-precision instantaneous frequencies estimation and SST. Two synthetic signal examples show that HSST can minimize the impact of the time-sample interval to achieve high-precision and high-resolution SST results with high efficiency. A real 3D seismic data application demonstrates that HSST has fantastic performance in time-frequency precision and resolution enhancement, and it can be widely used in digital signals processing and interpretation fields. Full article

(This article belongs to the Special Issue Structural Geology, Rock Mechanics and Their On-Site Testing Analysis)

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18 pages, 12889 KiB

Open AccessCase Report

Seismic Wave Field Anomaly Identification of Ultra-Deep Heterogeneous Fractured-Vuggy Reservoirs: A Case Study in Tarim Basin, China

by Xiangwen Li, Jingye Li, Lei Li, Zhonghong Wan, Yonglei Liu, Peiling Ma and Ming Zhang

Appl. Sci. 2021, 11(24), 11802; https://doi.org/10.3390/app112411802 - 12 Dec 2021

Cited by 9 | Viewed by 2935

Abstract

Ultra-deep (7500–9000 m) Ordovician tight limestone heterogeneous fractured-vuggy reservoir is an important target of FuMan Oilfield in Tarim Basin. The strike-slip fault controlled reservoir is related to formation fracture and dissolution caused by geological stress. The seismic wave-field anomaly characteristics with different energy and irregular waveform are displayed in the seismic profile. Accurate identification of fractured-vuggy reservoirs wrapped in tight limestone is the direct scheme to improve production efficiency. Therefore, a new combination method flow of seismic wave-field anomaly recognition is proposed. In this process, the seismic data must be preprocessed initially, and on this basis, robust formation dip scanning is carried out. Secondly, the dip data is applied to the transverse smoothing filter to obtain the formation background data. Eventually, the seismic wave-field anomaly data is the residual between background data and original seismic data. This method has been applied in blocks with different structural characteristics and can effectively improve the resolution of strike-slip fault controlled reservoirs. Based on the results, the drilling success rate is increased to more than 95%, and the high-yield rate of oil tests is increased to 75% in 2021. Multiple applications indicate that the method is robust and can be popularized. Full article

(This article belongs to the Special Issue Structural Geology, Rock Mechanics and Their On-Site Testing Analysis)

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