CIVE1105 Rock Mechanics – Assignment 2

Interpretation of Rock Mass Properties for

a Tunneling Project

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 Table Of Content

Introduction................................................................................................3

Literature Review.......................................................................................4

Review and Interpretation of Rock Mass Information............................4-5

Interpretation of Rock and Rock Mass Information...............................5-6

Rock Mass Classification (RMR and Q Systems)..................................7-8

Derivation of Rock Mass Engineering Parameters...............................8-10

Discussion and Recommendation.......................................................10-11

References................................................................................................11

Appendix.............................................................................................12-18

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1. Introduction

The objective of this assignment is to conduct an exhaustive analysis of the geological and
geotechnical conditions critical to the design and construction of a sewage tunnel. The
assignment encompasses a detailed literature review, comprehensive interpretation of
available rock data, application of rock mass classification systems, derivation of rock mass
engineering parameters, and a thorough discussion on suitable tunnel construction
methods.

Central to this endeavor is a detailed literature review, which serves as the foundational
cornerstone of our analysis. By delving into authoritative sources such as "Engineering Rock
Mechanics" by Hudson and Harrison, and supplementing this with pertinent lecture notes,
we establish a robust understanding of the principles underpinning tunneling
methodologies and rock mass classification systems.

Subsequently, the assignment delves into the comprehensive interpretation of available

rock data. Through meticulous review and analysis, we aim to elucidate critical parameters
such as Rock Quality Designation (RQD), Uni axial Compressive Strength (UCS), and
discontinuity characteristics. A geological section is meticulously prepared to visually depict
the spatial distribution of these properties along the proposed tunnel route, aiding in the
identification of potential challenges and opportunities for optimization.

Building upon this foundation, the assignment proceeds to apply esteemed rock mass
classification systems such as the Rock Mass Rating (RMR) and Q systems. Through
systematic categorization of rock mass conditions, we aim to gain invaluable insights into
stability considerations and construction feasibility. Elaborate calculations are undertaken to
determine the RMR and Q values for each delineated section, thereby facilitating informed
decision-making.

Furthermore, the assignment endeavors to derive essential rock mass engineering

parameters, including cohesion, friction angle, and deformation modulus. By leveraging
established correlations proposed by Bieniawski, these parameters serve as pivotal inputs
for structural analyses and support system design, ensuring the structural integrity and
stability of the tunnel.

Finally, a comprehensive discussion ensues on suitable tunnel construction methods.

Drawing upon the insights gleaned from our analysis, we aim to provide actionable
recommendations to stakeholders involved in the design and construction process. Through
a holistic approach, we endeavor to ensure the seamless realization of the sewage tunnel
project, safeguarding its long-term functionality and structural integrity.

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2. Literature Review

A literature review was conducted to understand the fundamental principles and

methodologies for assessing rock mass characteristics and tunnel construction techniques.
Key references include:

 Hudson, J.A. & Harrison, J.P. (1997). "Engineering Rock Mechanics: An Introduction to
the Principles."

 Bieniawski, Z.T. (1989). "Engineering Rock Mass Classifications."

 Project Handbook, School of Civil & Chemical Engineering, RMIT University, Melbourne,
2008.

These sources provide critical insights into rock mass classification systems (RMR and Q
systems), methods for deriving rock mass properties, and tunnel construction techniques.

3. Review and Interpretation of Rock Mass Information

A meticulous review of available rock data has been conducted to discern the salient
parameters crucial for robust tunnel design. This encompasses a comprehensive
interpretation of Rock Quality Designation (RQD), Uni axial Compressive Strength (UCS),
discontinuity characteristics including spacing, orientation, and persistence, as well as an
assessment of groundwater conditions along the envisaged tunnel alignment. A detailed
geological section has been meticulously prepared to visually depict the spatial distribution
of pertinent rock properties along the proposed tunnel route.

 Here's a detailed table for the review and interpretation of rock mass information:

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 Rock Mass Class: This classification categorizes the overall quality of the rock mass
based on parameters such as RQD, UCS, and discontinuity characteristics. It provides
insights into the overall behavior of the rock mass and its suitability for tunneling.

 Rock Mass Quality: This classification further refines the assessment by considering the
engineering implications of the rock mass class. It provides an indication of the expected
difficulty in excavation and the level of support required for tunnel construction.

 Explanation:

For example, in the depth interval of 0-10 meters, the rock type is sandstone with an RQD
of 85% and a UCS of 150 MPa. The discontinuity spacing is > 1 meters, oriented vertically.
Groundwater conditions are dry . Based on these parameters, the rock mass class is
categorized as "Good," indicating favorable conditions for tunneling. However, the rock
mass quality is classified as "Fair," suggesting moderate support requirements due to the
presence of discontinuities.

4. Interpretation of Rock and Rock Mass Information

The interpreted rock and rock mass information, inclusive of RQD, UCS, discontinuities, and
groundwater conditions, has been meticulously analyzed to elucidate the overarching
behavior of the rock mass. This insightful interpretation offers invaluable insights into the
stability characteristics, as well as the strength and deform-ability attributes of the rock
mass, all of which are pivotal for informed tunnel design and construction decisions.
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 Here's a detailed table for the interpretation of rock and rock mass information:

 Explanation:

 Rock Mass Class: This classification categorizes the overall quality of the rock mass
based on parameters such as RQD, UCS, and discontinuity characteristics. It provides
insights into the overall behavior of the rock mass.

 Rock Mass Quality: This classification further refines the assessment by considering the
engineering implications of the rock mass class. It provides an indication of the expected
difficulty in excavation and the level of support required for tunnel construction.

 Rock Mass Behavior: This describes the stability and behavior of the rock mass based on
its classification. It indicates the likelihood of rockfall, collapse, or deformation during
tunnel excavation.

 Stability Considerations: This provides recommendations for support system design and
construction methods based on the stability of the rock mass. It helps in mitigating
potential risks and ensuring safe tunneling operations.

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5. Rock Mass Classification (RMR and Q Systems)

The esteemed Rock Mass Rating (RMR) and Q systems have been judiciously applied to
systematically categorize the prevailing rock mass conditions at pertinent sections along the
tunnel alignment. This robust classification methodology provides a structured framework
for evaluating the geological and geotechnical factors governing tunnel stability and
construction feasibility. Elaborate calculations have been meticulously executed to ascertain
the RMR and Q values for each delineated section.

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6. Derivation of Rock Mass Engineering Parameters

Critical rock mass engineering parameters, comprising cohesion, friction angle, and
deformation modulus (Em), have been meticulously derived utilizing established

correlations proposed by Bieniawski. These fundamental parameters serve as the

cornerstone for comprehensive tunnel design and construction planning, furnishing
indispensable inputs for rigorous structural analyses and the design of optimal support
systems.

Table : Derived Rock Mass Engineering Parameters

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Graph:

 Detailed Calculation for Derived Parameters

1. Cohesion (c) Calculation

2. Friction Angle (φ) Calculation

3. Deformation Modulus (Em) Calculation

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7. Discussion and Recommendation

In light of the comprehensive analysis of rock mass properties, classification outcomes, and
derived engineering parameters, it is unequivocally recommended to leverage the proven
efficacy of the New Austrian Tunneling Method (NATM) for the seamless construction of the
sewage tunnel. The NATM methodology offers unparalleled versatility in tackling the myriad
challenges posed by variable rock conditions, thereby facilitating the implementation of
tailored support systems attuned to the diverse geological characteristics encountered
during excavation.

The utilization of NATM offers several distinct advantages that align with the project's
objectives and constraints. Firstly, its adaptability allows for real-time adjustments to
excavation and support strategies based on the encountered geological conditions, ensuring
optimal safety and efficiency throughout the construction process. This dynamic approach
minimizes the need for extensive per-planning and enables rapid response to unforeseen
challenges, thereby reducing project delays and cost overruns.

Furthermore, NATM's emphasis on observational methods empowers construction teams to

closely monitor and evaluate ground behavior during excavation, facilitating early detection
of potential instabilities and enabling proactive measures to mitigate risks. This proactive
stance is crucial for safeguarding the integrity of the tunnel structure and ensuring the long-
term stability and penetrability of the sewage system.

Additionally, the NATM's compatibility with a wide range of support systems, including
shotcrete, rock bolts, steel ribs, and lattice girders, allows for the implementation of
customized solutions tailored to the specific geological conditions encountered along the
tunnel alignment. This flexibility in support design ensures optimal utilization of available
resources while effectively addressing the challenges posed by variable rock properties,
discontinuities, and groundwater conditions.

Moreover, the proven track record of NATM in successfully navigating complex geological
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formations and adverse ground conditions underscores its suitability for the present project.
By drawing upon lessons learned from previous NATM projects and leveraging best
practices in tunnel construction and support design, the project stands to benefit from
enhanced operational efficiency, reduced construction risks, and improved long-term
performance of the sewage tunnel infrastructure.

In conclusion, the adoption of the New Austrian Tunneling Method represents a prudent
and strategic decision that aligns with the project's objectives of ensuring safe, efficient, and
cost-effective construction of the sewage tunnel. By embracing NATM's adaptive approach,
the project can navigate the complexities of variable rock conditions with confidence,
ultimately delivering a robust and resilient infrastructure that meets the needs of the
community for years to come.

8. References

1. Hudson, J.A., & Harrison, J.P. (1997). Engineering Rock Mechanics: An Introduction to
the Principles. Elsevier.

2. Lecture Notes on Tunnel Construction Methods.

3. Project Handbook, School of Civil & Chemical Engineering, RMIT University, Melbourne,
2008.

Appendix

Appendix A: Detailed Table for Review and Interpretation of Rock Mass Information

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Appendix B: Derived Rock Mass Engineering Parameters

Appendix C: Graphs

 Rock Mass Rating Components by Section

Rock Properties by Section

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Appendix D: Detailed Calculation for Derived Parameters

1. Cohesion (c) Calculation

The cohesion values have been derived from empirical correlations based on the RMR
values and rock type characteristics. The values are cross-referenced with established
literature for accuracy.

2. Friction Angle (φ) Calculation

Friction angle values are derived using empirical relationships tied to the RMR and Q
systems, ensuring alignment with standard geotechnical practices.

3. Deformation Modulus (Em) Calculation

The deformation modulus is calculated based on empirical correlations proposed by

Bieniawski, which link the modulus to the rock mass classification parameters and the intact
rock properties.

Appendix E: Additional graphs

 Geological Section

A detailed geological section has been prepared to visually depict the spatial distribution of
rock properties along the proposed tunnel route. This section aids in identifying potential

challenges and opportunities for optimization in tunnel design and construction.

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 Discontinuity Characteristics Table

A table summarizing the discontinuity characteristics, including spacing, orientation, and

persistence, is included to provide a comprehensive understanding of the rock mass
behavior.

Additional comparison Graphs

Graph 1: RQD vs. Depth

Graph 2: UCS vs. Depth

Graph 3: RMR vs. Depth

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Graph 4: Q Value vs. Depth

RMR

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Q-System

Derived Rock Mass Engineering Parameters

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Graph 5: Cohesion vs. Depth

Friction Angle vs. Depth:

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Friction Angle vs. Depth:

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