Stability Analysis and Reliability Evaluation in Cataclastic Loose Rock Mass Blocks

Advances in Civil Engineering ◽

10.1155/2021/5314937 ◽

2021 ◽

Vol 2021 ◽

pp. 1-9

Author(s):

Liguo Zhang ◽

Dong Wang ◽

Guanghe Li ◽

Jiaxing Dong ◽

Junpeng Zhang

Keyword(s):

Rock Mass ◽

System Reliability ◽

Laser Scanning ◽

Failure Modes ◽

Reliability Evaluation ◽

Rock Slopes ◽

Hydropower Project ◽

Rock Masses ◽

Cataclastic Rock ◽

Key Block

Cataclastic rock masses with multiple failure modes and mechanisms are critical geological problems in the construction of rock slopes. Cataclastic rock masses are widely distributed in slopes of a hydropower project located on Lancang River, which is located in Tibet, China. In this study, the potentially unstable block of the slope is divided into key block and secondary key block based on the key block theory, and the system reliability evaluation theory is introduced. The method for quantitatively analyzing the rock mass stability of cataclastic slopes with sliding failure is established. Then, the spatial distribution of cataclastic rock masses and discontinuities in several rock slopes of a hydropower project are determined using traditional geological surveying and 3D laser scanning. At last, combining the BATE 2.0 software and the stereographic projection of the vector, the proposed method is applied to the study area. The results show that the main failure mode of the studied slope is wedge failure, and the system reliability is 1.69. With the increase in the instability probability of the key block, the increase in the instability probability of the system block is obvious, which reflects the controlling effect of the key block on the stability of the system block. The calculated system instability probability is slightly larger than the key block instability probability.

Download Full-text

Mechanical Characteristics and Failure Modes of Low-Strength Rock Samples with Dissimilar Fissure Dip Angles

10.3233/atde210291 ◽

2021 ◽

Author(s):

Y L Wang ◽

D S Liu ◽

K Li ◽

X M Hu ◽

D Chen

Keyword(s):

Rock Mass ◽

Mechanical Characteristics ◽

Failure Modes ◽

High Strength ◽

Rock Masses ◽

Deformation And Failure ◽

Deformation Features ◽

Low Strength ◽

Dip Angle ◽

Strength Rock

The mechanical characteristics and failure modes of low-strength rock sample with various fissure dip angles were investigated by conventional uniaxial compression test and three-dimensional (3D) crack reconstruction. The results indicated that compared with high-strength rock masses, cracks had different influences on the low-strength rock mass mechanical deformation features. Thereinto, the dip angle of fissures can cause post-peak failure stage of stress-strain curve change from swift decline to multi-step down, showing obvious ductility deformation and failure characteristics. Peak strength and elastic modulus owned an anti-S-shaped growth tendency with the growth of fissure dip angle, which was positively correlated and greatest subtle to the fissure dip angle α < 21° and α > 66.5°. The axial peak strain reduced first and enlarged rapidly with growing fissure dip angle, suggesting a V-shaped change trend. Increasing the fissure dip angle will change the sample failure mode, experienced complete tensile failure to tensile-shear composite failure, and ultimately to typical shear failure. Also, the crack start angle decreased with enlarging fissure dip angle, larger than that the high-strength rock mass fissure dip angle. The above research findings can complement and improve the study of fissured rock masses.

Download Full-text

Rock Mass Rating and Geological Strength Index of rock masses of Thopal-Malekhu River areas, Central Nepal Lesser Himalaya

Bulletin of the Department of Geology ◽

10.3126/bdg.v16i0.8882 ◽

2013 ◽

Vol 16 ◽

pp. 29-42 ◽

Cited By ~ 10

Author(s):

Jaya Laxmi Singh ◽

Naresh Kazi Tamrakar

Keyword(s):

Rock Mass ◽

Surface Condition ◽

Geological Strength Index ◽

Rock Mass Rating ◽

Rock Slopes ◽

Lesser Himalaya ◽

Rock Masses ◽

Strength Index ◽

Rock Mass Structure ◽

Exposed Rock

The rock slopes of the Thopal-Malekhu River areas, Lesser Himalaya, were characterized applying various systems of rock mass classification, such as Rock mass Rating (RMR) and Geological Strength Index (GSI), because the study area comprises well exposed rock formations of the Nawakot and Kathmandu Complexes, across the Thopal-Malekhu River areas. In RMR system, mainly five parameters viz. Uniaxial Compressive Strength (UCS) of rock, Rock Quality Designation (RQD), spacing of discontinuity, condition of discontinuity, and groundwater condition were considered. The new GSI charts, which were suitable for schistose and much disintegrated rock masses, were used to characterize rock slopes based on quantitative analysis of the rock mass structure and surface condition of discontinuities. RMR ranged from 36 to 82 (poor to very good rock mass) and GSI from 13.5±3 to 58±3 (poor to good rock mass). Slates (of the Benighat Slate) are poor rock masses with low strength, very poor RQD, and close to very close spacing of discontinuity, and dolomites (Dhading Dolomite) are fair rocks with disintegrated, poorly interlocked, and heavily broken rock masses yielding very low RMR and GSI values. Phyllites (Dandagaun Phyllite), schist (Robang Formation) and quartzite (Fagfog Quartzite, Robang Formation and Chisapani Quartzite), dolomite (Malekhu Limestone), and metasandstone (Tistung Formation) are fair rock masses with moderate GSI and RMR values, whereas quartzose schist and gneiss (Kulekhani Formation) are very good rock masses having comparatively higher RMR and GSI. The relationship between GSI and RMR shows positive and good degree of correlation. DOI: http://dx.doi.org/10.3126/bdg.v16i0.8882 Bulletin of the Department of Geology Vol. 16, 2013, pp. 29-42

Download Full-text

System Reliability Evaluation of a Bridge Structure Based on Multivariate Copulas and the AHP–EW Method That Considers Multiple Failure Criteria

Applied Sciences ◽

10.3390/app10041399 ◽

2020 ◽

Vol 10 (4) ◽

pp. 1399 ◽

Cited By ~ 1

Author(s):

Hanbing Liu ◽

Xirui Wang ◽

Guojin Tan ◽

Xin He

Keyword(s):

System Reliability ◽

Failure Modes ◽

Failure Criteria ◽

Reliability Evaluation ◽

Bridge Structure ◽

Copula Functions ◽

Entropy Weight ◽

Joint Failure ◽

Simply Supported ◽

Bridge System

The system reliability evaluation of a bridge structure is a complicated problem. Previous studies have commonly used approximate estimation methods, such as the wide bounds method and the narrow bounds method, but neither could obtain an accurate result. In recent years, the copula theory has been introduced into the system reliability evaluation, which can obtain more accurate results than the approximate methods. However, most studies simply construct binary copula functions to consider the joint failure of two failure modes. For a complex bridge structure composed of multiple components and failure modes, the joint failure of multiple failure modes needs to be considered. Before evaluating the system reliability, it is necessary to determine the failure criteria of the system. Different failure criteria for simply supported beam bridges have been proposed. However, there is no standard available to determine which failure criterion to choose, and the selection of failure criteria is ambiguous. In this paper, a novel method is proposed to evaluate the system reliability of a simply supported beam bridge by considering multiple failure criteria based on multivariate copulas and the analytic hierarchy process entropy weight (AHP–EW) method. The method first considers multiple failure criteria comprehensively and constructs multivariate copulas for the joint failure of multiple components in a bridge system reliability evaluation. The AHP–EW method is a comprehensive weighting method combining the analytic hierarchy process and entropy weight methods, which is used to establish the hierarchical analysis model between system reliability and multiple failure criteria. By considering the joint failure of multiple failure modes in the system reliability evaluation under a single failure criterion, multivariate copula functions were constructed. In order to verify the applicability of the proposed bridge system reliability method, a simply supported reinforced concrete (RC) hollow slab bridge composed of nine slab segments was selected as the numerical example. The results indicate that the method proposed in this paper could evaluate the bridge system reliability more comprehensively and reasonably.

Download Full-text

Engineering Geological Investigation of dam site of proposed Sunkoshi-2 Hydropower Project, Khurkot area, eastern Nepal

Journal of Nepal Geological Society ◽

10.3126/jngs.v58i0.24603 ◽

2019 ◽

Vol 58 ◽

pp. 181-188

Author(s):

Bipin Adhikari ◽

Ujjwal Acharya ◽

Kamala Kant Acharya ◽

Subesh Ghimire

Keyword(s):

Rock Mass ◽

Geological Mapping ◽

Hydropower Project ◽

Rock Masses ◽

Geological Investigation ◽

Dam Foundation ◽

Rock Types ◽

Stability Against Sliding ◽

Dam Site ◽

Selection Of

The dam site of proposed Sunkoshi-2 Hydropower Project and its surrounding mainly comprise the Tawa Khola Formation, which is the basal formation of the Bhimphedi Group. Although garnet schist and micaceous quartzite bands are the main rock types; three rock units namely- Schist Unit, Quartzite Unit, and Gneiss Unit were identified. Engineering geological mapping followed by discontinuity survey were carried out. The result exhibited differences in fracture intensity and discontinuity characteristics of rock masses according to rock type. Since joint orientations were found to be consistent over fairly large areas, surface studies of joints were used in predicting subsurface orientations. Rock mass classification was made in line with the Rock Mass Rating System (RMR) and the Dam Mass Rating (DMR) classification for the dam foundation. The rock masses were classified onto fair to good rock classes according to RMR value. Dam foundation analysis regarding stability against sliding using DMR classification helped in selection of suitable dam-axis among two alternatives. Water Quality Standards (2005).

Download Full-text

Key block theory application for surrounding rock mass of underground powerhouse in Dagangshan Hydropower project

Frontiers of Discontinuous Numerical Methods and Practical Simulations in Engineering and Disaster Prevention ◽

10.1201/b15791-51 ◽

2013 ◽

pp. 371-376

Author(s):

J Dong ◽

G Xu ◽

Z Li ◽

Y Shen ◽

J Teng

Keyword(s):

Rock Mass ◽

Surrounding Rock ◽

Hydropower Project ◽

Block Theory ◽

Underground Powerhouse ◽

Theory Application ◽

Key Block

Download Full-text

The Engineering Characteristics and Classifications of Rock Masses along Road Section from Prambanan to Patuk, Yogyakarta, Indonesia

Journal of Applied Geology ◽

10.22146/jag.58034 ◽

2021 ◽

Vol 6 (2) ◽

pp. 119

Author(s):

Aisyah Shahirah Juhari ◽

I Gde Budi Indrawan, Dr. ◽

Wahyu Wilopo

Keyword(s):

Rock Mass ◽

Jointed Rock ◽

Research Area ◽

Geological Strength Index ◽

Rock Slopes ◽

Rock Masses ◽

The Road ◽

Road Section ◽

Rock Mass Quality ◽

The Relationship

Several attraction places and agriculture area that essentials for tourism and villager to do their activities are located approximately 6 km along the road of Candi Ijo to Ngoro-Oro in between Prambanan and Patuk sub-districts, Yogyakarta, Indonesia. Many jointed rock masses along the road have the potential to fail. This paper describes the rock mass characteristic and quality determined using the Geological Strength Index (GSI) and Rock Mass Rating (RMR) classifications. The rock mass characteristic and quality were essentially the preliminary results of a study to evaluate stability of the rock slopes along the road of Candi Ijo to Ngoro-Oro. Field observation and laboratory tests were carried out to determine parameters of the GSI and RMR. The results show that the slopes in the study area consisted of tuffaceous sandstone, vitric tuff, lithic tuff, cemented tuffaceous sandstone, lapilli tuff, subarkose, laminated mudrock, and laminated tuffaceous sandstone. The intact rocks were classified as weak to very strong. The research area consisted of three rock mass qualities, namely fair rock mass quality having GSI between 30 and 45 and RMR between 41 and 60, good rock mass quality having GSI between 46 to 65 and RMR between 61 and 80, and very good rock mass quality having GSI > 65 and RMR between 81-100. The relationship between GSI and RMR obtained in this study was in good agreement with that proposed by Hoek et al. (1995).

Download Full-text

Griffith’s Strength Loci for Jointed Rock Masses

Journal of Energy Resources Technology ◽

10.1115/1.3231436 ◽

1989 ◽

Vol 111 (4) ◽

pp. 270-278

Author(s):

B. A. Chappell

Keyword(s):

Rock Mass ◽

Equilibrium Model ◽

Failure Modes ◽

Shear Failure ◽

Soft Rock ◽

Jointed Rock ◽

Rock Masses ◽

Loaded Rock ◽

Deformation Models ◽

Composite Moduli

Stress distribution in a rock material containing cracks, without thickness, and joints, with thickness, is controlled by two basic principles, namely equilibrium and compatibility. Two deformation models representing these two basic requirements are used to construct the rock mass’ local composite moduli that are then combined to obtain the rock mass’ global moduli. Deformational modes in the form of compliances give upper and lower value moduli representing the constraints of compatibility and equilibrium, respectively. In a loaded rock mass there is no stress redistribution involved in the application of the equilibrium model, while for the compatibility model there are stress redistributions. For cracks, with no thickness, only the equilibrium model defines the deformation moduli, whereas for joints both the equilibrium and compatibility models are required because of the joint’s volume effects. Using both the joint’s shear strength and the Griffith’s crack initiation criteria, the Griffith’s strength loci for firm-hard and soft rock masses are produced. The strength loci representing normal and shear failure modes for the firm-hard rock mass are significantly different, whereas for the soft rock mass they are similar.

Download Full-text

Distribution System Reliability Assessment for Improved Feeder Configurations

International Journal of Engineering and Advanced Technology - Regular Issue ◽

10.35940/ijeat.f8964.088619 ◽

2019 ◽

Vol 8 (6) ◽

pp. 4416-4421 ◽

Cited By ~ 1

Keyword(s):

System Reliability ◽

Power Distribution ◽

Distribution System ◽

Failure Modes ◽

Electrical Power ◽

Distribution Network ◽

Reliability Evaluation ◽

Power Distribution System ◽

Reliability Indices ◽

Analytical Technique

This Paper enlightens the significance of the reliability evaluation for an electrical power distribution network using the analytical technique FMEA. The power distribution system is subject to interruptions frequently as a lot of devices are responsible for its effective operation. All the possible failures of each component are considered and the reliability is evaluated in terms of system reliability indices like SAIFI, SAIDI, ENS, and ASAI. FMEA method observes the failure modes of a procedure and reduces it by ranking over its impacts. In this paper, RBTS bus2 distribution network is used for the analysis. The influences of various feeder reconfigurations are considered and the system reliability indices are obtained. The obtained results show that the reliability of the distribution system is enriched with various feeder reconfigurations. Reliability Evaluation helps to design the future Distribution system and its expansion.

Download Full-text

Geomechanical characterization of rock masses by means of remote sensing techniques

10.5194/egusphere-egu2020-13961 ◽

2020 ◽

Author(s):

Lidia Loiotine ◽

Marco La Salandra ◽

Gioacchino Francesco Andriani ◽

Giovanni Barracane ◽

Marc-Henri Derron ◽

...

Keyword(s):

Remote Sensing ◽

Rock Mass ◽

Point Cloud ◽

Laser Scanning ◽

Mitigation Measures ◽

Rock Masses ◽

Testing Procedures ◽

Remote Sensing Techniques

Improving the methods for the characterization of rock masses by integrating traditional field surveys with remote sensing techniques is fundamental for practical and realistic discontinuous modelling, in order to identify the failures and kinematics, develop landslide susceptibility assessment and plan prevention and mitigation measures.A 20 m-high cliff at Polignano a Mare (Southern Italy) was selected as case study for the presence of well-developed discontinuities (bedding and joints) and due to the local morphology, consisting of a valley with opposite slopes at a distance of 150 m, and a pocket beach at their toe. This configuration allowed to perform both traditional and remote sensing surveys. First, photogrammetry methods were carried out on the ground and with the help of a boat. Structure from Motion (SfM) technique was then used to process and combine the pictures, in order to elaborate a raw point cloud of the case study. Secondly, high resolution Terrestrial Laser Scanning (TLS) and Unmanned Aerial Vehicle (UAV) techniques were conducted after positioning Ground Control Points (GCPs) all over the rock mass, with the aim of obtaining a more detailed point cloud. Eventually, a unique and optimized georeferenced point cloud was obtained by combining the previous models, also removing the non-geological objects. Furthermore, Infrared Thermography (IT) was carried out in order to investigate the fracture pattern, the areas of concentrated stress, and the presence of humidity and voids.The structural analysis of the rock mass was performed directly on the point cloud, by testing procedures and algorithms for the automatic identification of discontinuity sets and of their orientation, spacing, persistence and roughness.The next step of this research will concern the evaluation of the instability mechanisms with the help of kinematic analyses, by means of stereographic projections. Finally, the reliability of the procedure for a complete rock mass characterization, which is expected to be obtained as the final result, will be tested by means of numerical stability solutions, after calibrating the geomechanical model and importing the fracture system in an appropriate software.&#160;

Download Full-text