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Over the years, Dr Evert Hoek has prepared a number of documents for a variety of purposes, which have never been published. Some of the documents are intended as replacement chapters for an eventual update of "Practical Rock Engineering", some are extracts from consulting reports and others are simply discussions written during the development of rock engineering concepts or methodologies.
There is no intention to publish these documents but they are being made available on the Rocscience web site in the hope that they will be of interest to those who visit this site. Additional documents will be added to this collection as they become available. Comments, criticism and discussion of the ideas presented in these documents would be welcomed and should be sent directly to Evert Hoek at ehoek@attglobal.net.
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Design of Large
Underground Caverns (3,461 KB)
A case history based on the Mingtan Pumped Storage Project in Taiwan
Large underground caverns are used for a variety of purposes in civil engineering. These include caverns housing turbines, electrical generators and transformers in hydroelectric projects, caverns for storing liquid or gaseous fuels, underground warehouses and underground sports facilities. An example of a large underground hydroelectric complex in Taiwan will be used to illustrate the design and construction process for this type of civil engineering facility.
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Anchored Crane Beams in Hydroelectric Caverns (1,691 KB)
In designing an underground powerhouse, the choice of the crane and
its associated supporting structure can have a major impact on the
cavern sidewalls and on the construction sequence. In many cases,
the crane structure is designed by structural engineers who treat
the underground cavern as a building, designing the crane supporting
structure to be independent of the surrounding rock.
While this approach is appropriate for surface buildings, it is misguided
in the case of underground caverns since it ignores the enormous load
carrying capacity of the rock mass, resulting in designs that are
inefficient in terms of the overall design and construction of the
cavern. An alternative approach is to attach the crane beams to the
cavern walls by means of a tensioned and grouted anchor system.
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Numerical Modelling of Shallow Tunnels (2,090 KB)
In designing very shallow tunnels the proximity of the ground surface
and the tendency for the material ahead of and above the tunnel face
to “cave to surface” have to be taken into account. These
factors introduce issues that are not present in the analysis of deep
tunnels and approaches such as the convergence-confinement method
are not applicable to shallow tunnels. By means of an example, some
of the problems of numerical modelling for shallow tunnels are discussed
and practical solutions to these problems are presented.
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Estimates of Strength and Deformation Modulus (799 KB)
In the preliminary stages of a rock engineering design the need for
approximate estimates of rock mass strength and deformation modulus
frequently arises. Several authors have published empirical estimates
of these properties, based on rock mass classification systems.
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Role of Tunnelling Experts (76 KB)
Experts play an important role in tunnelling, particularly in difficult
geological conditions, such as those that occur in Greece. Selection
of these experts must be made very carefully since their advice can
have a significant impact upon the cost and schedule of a major project.
This paper explores the various roles that these experts play in tunnelling
projects.
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Rockbolt Model (3,661 KB)
In the 1960s, I visited the laboratories of the Snowy Mountains Authority
in Cooma, Australia where I was shown a model used by Mr. Tom Lang
to demonstrate how rockbolts work. I was so impressed by this model
that I used a version of it in teaching a graduate course on rock
engineering at the University of Toronto. The series of photographs
included in this document were taken during a project where the students
assembled this model from scratch to discover for themselves how the
rockbolts work.
Dr. Carlos Carranza-Torres of the Itasca Consulting Group has provided
a movie of a UDEC numerical simulation of the rockbolt model. To view
this movie, click
here.
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History of the Hoek-Brown Criterion (95 KB)
The original Hoek-Brown failure criterion was developed during the
preparation of the book Underground Excavations in Rock,
published in 1980. The criterion was required in order provide input
information for the design of underground excavations. Since no suitable
methods for estimating rock mass strength appeared to be available
at that time, the efforts were focussed on developing a dimensionless
equation that could be scaled in relation to geological information.
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