\documentclass[twoside]{article}
\usepackage[silent,pdf,hyper]{elxfinal}
\usepackage{color}
\usepackage{hyperref}
\journalid{ES}{19}{6}{19}
\subident{proceedings of the round table}
{Using underground space to solve problems of nuclear energy}
{30 January 2019 $\bullet$ Moscow, Russia\vspace*{-2pc}}
\citnumber{}{9}
\paperid{2019ES000670}
\papertype{RAR}
\cpright{}{2019}
\lefthead{gupalo}
\righthead{spatial characterization} % of the physical process parameters in rock mass during construction of the underground facility for the RW disposal
\received{5}{April}{2019}
\accepted{18}{June}{2019}
\published{16}{December}{2019}
\definecolor{brown}{RGB}{157,23,4}

\authaddr{V. S. Gupalo,  Depart. %ment
``Physical processes of mining and geocontrol'' of NUST \mbox{``MISiS''}, Moscow, Russia.
(gupalo177@gmail.com)}


\begin{document}

\title{Spatial characterization of the physical process parameters in rock mass during construction of the underground facility for the RW disposal}

\author{1}{Gupalo}{V. S.}{}{1}{}{}
\affil{1}{Department ``Physical processes of mining and geocontrol'' of NUST ``MISiS''}{Moscow}{}{Russia}

\keywd{Underground research laboratory}
\keywd{in situ set of research}
\keywd{condition of the mass}
\keywd{construction of URL}

%Spatial characterization of the physical process parameters in rock mass during construction of the underground facility for the RW disposal
%SPATIAL CHARACTERIZATION OF THE PHYSICAL PROCESS PARAMETERS IN ROCK MASS DURING CONSTRUCTION OF THE UNDERGROUND FACILITY FOR THE RW DISPOSAL
%V.S. Gupalo, PhD, Professor of the Department ``Physical processes of mining and geocontrol'' of NUST ``MISiS''
%VS_Gupalo@misis.ru

\abstract{Substantiation of the suitability of the subsoil area for the construction of a radioactive waste repository in deep geological formations is a consequential multistage process, including the studies on the scale of ``district'', ``site'', ``plot''. In near future in Russia it is planned to start work on sinking permanent mine openings of the underground research laboratory (URL).
The purpose of this article is to provide a brief analysis of international and local research experience in underground research laboratories and their equivalents, as well as the deep
geological repository (DGR) safety requirements to determine the scope of work on scientific and technical support for the URL construction.
A brief review of the applied research methods is presented on the following aspects:
	Parameters characterizing structural and tectonic condition of the rock mass -- rupture zones, fracture zones of various origins, monolith areas;
	geomechanical characteristics (stress-strain state, deformability and strength);
	hydrogeological characteristics of the mass elements and groundwater flow patterns;
	characteristics of the physical and chemical processes of interaction between groundwater and rocks and materials of engineering barriers.}

\section{Introduction}

\enlargethispage{-.5pc}

\def\dbltopfraction{.85}
\begin{figure*}[t]                     % Fig 1
\figurewidth{35pc}
\setimage{}{}{33pc}{}{2019es000670-f01}
\crosscaption{Stages of work to substantiate the suitability of the subsoil area for the
radioactive waste repository facility
[\itc{Gupalo et al.,} \reflink{Gupa05}{2005}].}
\end{figure*}

     Substantiation of the suitability of the subsoil area for the construction of a
radioactive waste repository in deep geological formations is a consequential
multistage process, including the studies on the scale of ``district'', ``site'', ``plot''
(\figref{1}).           %     (Fig.1).
 For the purpose of performing detailed (extended) researches and final
confirmation of the suitability of geological sites for the placement of the deep
geological repository (DGR), the practice of establishing underground research
laboratories is applied
[\itc{Blechschmidt,} \reflink{Blec10}{2010}],
OECD/NEA No. 78122 Nuclear Energy Agency. Underground Research
Laboratories (URL), 2013.\vspace*{1ex}

     The results of researches performed by such labs are to provide major data
necessary for assessment of safety of the facility, and to contribute to
demonstration of the reliability of the radioactive waste (RW) repository in
general. The representativeness and completeness of such field researches will
largely determine the credibility of the developed safety assessments.

     At that, the key requirement of the contemporary safety assessments concept
is the need to ``build-up credibility'' of the obtained assessments, based on the
actual characteristics of the rock mass and guaranteeing isolation for the required
periods of time
(IAEA Safety Standards SSR-5 ``Disposal of radioactive waste. Specific safety requirements'').
% [IAEA Safety Standards SSR-5].     %%% ???

     I. e. for safety substantiation to be successful it should meet several criteria:
favorable assessment solved by conscientious performance of a certain set of
measuring and calculation procedures, and also the submission of safety case of the
facility in the distant future, considering the influence of possible features, events
and processes (FEPs) of a natural and man-made origin. Such assessment can only
be performed based on a representative set of comprehensive field researches of
the dynamic patterns of properties and depends on status of the engineering and
geological elements of the facility after their long-term interaction, which requires
consideration when planning the URL researches.

     In near future in Russia it is planned to start work on sinking permanent
mine openings of the underground research laboratory (URL) %%% ???
[\itc{Kryukov,} \reflink{Kryu18}{2018};
\itc{Rosatom,} \reflink{Rosa18}{2018};
%\itc{Abramov,} \reflink{Abra17}{2017}]
Abramov A. A., Beygul V. P. The creation of an underground research laboratory
on the site ``Yeniseyski'' of Nizhnekanski rock mass, available on
\href{http://www.atomic-energy.ru/articles/2017/08/22/78690}
{http://www.atomic-energy.ru/ articles/2017/08/22/78690}].
     	
     The special feature of the planned stage of work -- URL opening sinking -- is
the possibility to perform a detailed research of the structure of the rock mass at
different hypsometric levels, to record the distribution and internal structure of the
ruptured zones and to perform sampling. The resulting impact of driving
operations on rocks with the accompanying changes in natural and artificial
physical fields of the mass can also serve as a source of data on its structure and
possible groundwater filtering patterns.

\begin{figure*}[t]                     % Fig 2
\figurewidth{35pc}
\setimage{}{}{37pc}{}{2019es000670-f02}
\shortcaption{Stages of the rock mass structure research.}\vspace*{\baselineskip}
\end{figure*}

     Due to this, the purpose of this article is to provide a brief analysis of
international and domestic research experience in underground research
laboratories and their equivalents, as well as the DGR safety requirements to
determine the scope of work on scientific and technical support for the URL
construction.

\section{Selection of Research Areas}

     Safety assessment of isolation of the RW in DGR during the required time
periods are based on estimates of migration of contamination resulting from the
penetration of groundwater to the wastes and subsequent release of radionuclides
through existing (natural) or additional (man-made) fractures. Consequently, the
rock mass condition, will be characterized by physical processes and their
benchmark indicators, which can change under the influence of natural
(geodynamics, ground pressure, erosion, ...) and man-made loads (explosive
impact during construction works, water disposal during operation, thermal impact
of isolated waste) during the construction and operation of the facility.

 \begin{sloppypar}    Regardless of the stage of research of the rock mass planned for repository,
the results of researches of these processes can be grouped into the following
benchmark data segments
[\itc{Gupalo et al.,} \reflink{Gupa05}{2005}]:
\end{sloppypar}

\begin{itemize}
\item
	parameters characterizing structural and tectonic condition of the rock
mass -- rupture zones, fracture zones of various origins, monolith
areas;
\item
\begin{sloppypar}
	geomechanical characteristics (stress-strain state, deformability and
strength)
\end{sloppypar}
\item
	hydrogeological characteristics of the mass elements and groundwater
flow patterns;
\item
	characteristics of the physical and chemical processes of interaction
between groundwater and rocks and materials of engineering barriers.
\end{itemize}

     In view of the above, further consideration of the types of work will be
performed in relation to these areas.\vspace*{\baselineskip}


\section{Study of Natural Fracture of Rock Mass and Details of its Structure}

    Fracture is one of the most significant factors affecting the safety of RW
repository in solid rock. The mass fracture indicators will also largely determine
the strength and stability of rocks; nature and intensity of deformations; water
capacity and permeability; temperature pattern of the mass; its seismic
characteristics, etc.

     The choice of research methods is determined by engineering and geological
conditions, tasks to be solved, relief and geological features of the construction site
[\itc{Rac,} \reflink{Rac86}{1986};
\itc{Sergeev,} \reflink{Serg85}{1985};
\itc{Zelanski et al.,} \reflink{Zela81}{1981}].
At the early stages of research,
profiling techniques (on the earth's surface) are used for spatial characteristics of
large disturbances.

     At later stages and while studying the man-made loads, a set of observation
methods is used at the internal points of the rock mass -- mapping, \mbox{x-raying},
logging -- as more detailed % one. (Fig. 2)
one
(\figref{2}).           %     (Fig. 2).


     Due to this, the study of fracture parameters which clarify the model of the
rock mass structure at this stage is based on the study of rock exposure along the
entire length of mines, and is performed at the site of the temporary backlog of the
mine support
[\itc{Magnor,} \reflink{Magn04}{2004};
\itc{Raven et al.,} \reflink{Rave07}{2007}].
%Geoscientific site characterization plan for the deep geologic repository %at the Bruce site, Kincardine, Ontario. Avis Intera Engineering Ltd., %available at
%\href{https://www.opg.com/generating-power/nuclear/nuclear-waste-management/Deep-Geologic-Repository/Documents/HPD/4.3.55_geoscientificsitecharacter.pdf}
%{https://www.opg.com/generating-power/nuclear/n %uclear-waste-management/Deep-Geologic-Reposito %ry/Documents/HPD/4.3.55\underline{ }geoscientificsitecharact er.pdf}].     %%% ???
%\itc{Raven et al.,} \reflink{Rave07}{2007}].
During the study, a mapping of
loose areas (detailed geological description), description of the rocks composition,
their structural and tectonic features, degree of weathering, shape and size of
individual rocks is performed. The main systems of fractures with the description
of their surface morphology, composition and structure of the filler are visually
identified. This investigation also includes the mass measurement of the elements
of the occurrence of fractures and their characteristic parameters such as the visible
length, opening, filler composition, distances between the fractures etc.

     Moreover, at this stage, the sampling is carried out to obtain detailed
petrological, mineralogical and structural characteristics of various elements of the
mass.

     However, this scope of research does not allow to characterize the
distribution of fractures at the depth of the mass. This determines the need to
supplement the measurement data by borehole methods of research using a range
of geophysical methods.


\begin{table*}[t]                                   % Table 1
\tablewidth{41pc}
\caption{Solid Rocks Features According to Geological Data}
\vspace{5pt}
\begin{tabular}
{@{}l@{\hspace{30pt}}
c@{\hspace{20pt}}
c@{\hspace{20pt}}
c@{\hspace{25pt}}
c@{}}
\hline
\\ [-7pt]
Degree of & Description of          &   Fracture index & Blocky         & Total fracture \\
fracture  & rocks                   &                  &  structure, m  &  opening, mm/m \\
 [7pt]  \hline   \\ [-4pt]
Highly    &  Highly weathered rocks, &    $>25$         & $ 0.05\times0.05\times 0.1$        &  \\
fractured & crumbled when struck     &                &            &   10--20  \\
          & with a hammer, ferrum    &                &              &  \\
          & oxides in fractures      & & &  \\
Slightly  & Slightly fractured       &   15--25        &  $0.1\times0.2\times0.2 $   &    1--10  \\
fractured & rocks,  mildly           &   10--15        &  $0.2\times0.5\times0.1 $   &    1--2  \\
          & weathered, solid         &    5--10        &  $0.5\times0.5\times0.3 $   &  \\
Monolithic& Rocks with the           &   $<5$           & $ 0.5\times0.5\times1.0$    &     $<1$  \\
          & presence of closed       & & &  \\
          & fractures, very solid,   & & &  \\
          & monolithic               & & &  \\
[4pt] \hline
\end{tabular}
\end{table*}






     The practice of comprehensive geophysical studies shows that for many
rocks there is a clear quantitative relationship between the speed of elastic waves,
electrical resistance and fracture parameters.
\tabref{1}  % Tables 1
and
\tabref{2}  % 2
present a statistical
generalization of such characteristics of solid rock mass.
[\itc{Gupalo,} \reflink{Gupa17}{2017};
\itc{Rac,} \reflink{Rac86}{1986};
\itc{Savich,} \reflink{Savi86}{1986};
\itc{Sergeev,} \reflink{Serg85}{1985}].

     At that, the elastic waves of 0.1 to 100 m in length are used to evaluate the
properties of rocks varying from samples to mass. Accordingly, the method used
for determining speeds from a few centimeters to several hundred and thousands of
meters should also be changed. When constructing the graphs of speed change of
elastic waves measured in different directions, a large scale curves are made that
characterize not the general heterogeneity of the mass, but heterogeneity within the
given directions (vector characteristics). The set of such vector graphs makes it
possible to conclude on % anisotropy. [Molokov, 1987; Nikitin, 1981]
anisotropy
 [\itc{Molokov,} \reflink{Molo87}{1987};
 \itc{Nikitin,} \reflink{Niki81}{1981}].

\def\bottomfraction{.8}
\def\textfraction{.05}

\begin{table}[b]                                   % Table 2
\tablewidth{41pc}
\crosstablecaption{Change of the Sold Rocks Properties of Various Fracture Extent}
\vspace{5pt}
\begin{tabular}
{@{}l@{\hspace{40pt}}
c@{\hspace{40pt}}
c@{\hspace{40pt}}
c@{\hspace{37pt}}
c@{\hspace{37pt}}
c@{}}
\hline
\\ [-7pt]
Degree of fracture  &    $V$, km/s  &  $\rho$, Om/m & P, \% &   $\rho$, g/sm$^3$ & $\sigma$, MPa \\
 [7pt]  \hline   \\ [-4pt]
Highly fractured    &   0.4--3.5  &  50--100   &    4--6    & 2.5--2.6   &     20--80  \\
Slightly fractured  &    2--4     &  100--300  &    1--4    & 2.6--2.7   &     80--110  \\
Monolithic          &    5--6     &  300--1000 &  0.1--0.001& 2.8--3.0   &     120--140
 \\
[4pt] \hline
\end{tabular}
\end{table}


     One of the ways to obtain such information about rock mass is to perform
seismic micro profiling in mines and seismic logging in wells drilled perpendicular
to their longitudinal axis
[\itc{Savich et al.,} \reflink{Savi69}{1969}].
 Measuring sites are equipped with
an increment of 50 m along the length of the mines and the increment value
decreases in case of opening of abnormal zones (tectonic zones or fractured rocks,
areas of abundant water flow).

\section{The Research of Man-Made Fracturing and Assessment of the Impact of
Driving Operations on the Size of the Disturbed Border Zone and its Parameters}\vspace*{1.2pc}

     Due to the fact that the opening sinking in URL is planned to be performed
by drill and blast method, which causes the increased dimensions of the disturbed
border zone, special attention in the course of research should be paid to changes in
mass fracture depth %. [Siren, 2014; Emsley et al., 1997; Siren, 2015]
 [\itc{Emsley et al.,} \reflink{Emsl97}{1997};
 \itc{Siren,} \reflink{Sire14}{2014}, %%% ???+
 \reflink{Sire15}{2015}].


     Increased fracturing associated with mining operations and redistribution of
stresses around the mine openings shall cause the increase of the permeability of
the geological environment and the contact of RW containers with groundwater
(\figref{3}).           %     (Fig. 3).


     Indicators of fracturing of the mass, both in the natural condition, and as a
result of driving operations are determined on the basis of drilling and subsequent
inspection of wells of various purposes. Such criteria as the specific granulometric
composition and core recovery are used to evaluate the fracture while drilling. The
disadvantage of this method is the impossibility of separating the natural fracture
and the additionally created as a result of driving operations. It also does not
evaluate the development of the disturbed border zone through time.\vspace*{-.3ex}

     To separate ``natural'' and ``man-made'' fracture, some URL research
programs
[\itc{Raven et al.,} \reflink{Rave07}{2007}]
%(Raven et al.,  %%% ???
%Geoscientific site characterization plan for the deep geologic repository %at the Bruce site, Kincardine, Ontario. Avis Intera Engineering Ltd., %available at
%\href{https://www.opg.com/generating-power/nuclear/nuclear-waste-management/Deep-Geologic-Repository/Documents/HPD/4.3.55_geoscientificsitecharacter.pdf}
%{https://www.opg.com/generating-power/nuclear/n %uclear-waste-management/Deep-Geologic-Reposito %ry/Documents/HPD/4.3.55\underline{ }geoscientificsitecharact er.pdf}) %%% ???
%[\itc{Raven et al.,} \reflink{Rave07}{2007}]
provide for drilling steeply inclined small diameter
boreholes ahead of shaft sinking (along the design contour) and subsequently fill
them with material based on epoxy resin. Drilling out of this material after the
shaft sinking allows to identify and characterize fractures newly appeared as a
result of blast work.\vspace*{-.3ex}

\begin{figure*}[t]                     % Fig 3
\figurewidth{35pc}
\setimage{}{}{28pc}{}{2019es000670-f03}
\caption{The role of the disturbed border zone openings in the formation of
radionuclide distribution patterns during disposal.}
\end{figure*}


\enlargethispage{-9.2\baselineskip}

     Assessment of the evolution of the disturbed border zone through time
(including the result of the impact of work on the creation of adjacent mines)
entails organization of long-term observations using a set of measurement
processes
[\itc{Gupalo,} \reflink{Gupa17}{2017}].
In this case, identification of the initial condition of the
mass is an important stage of such work.

     Methods of video and ultrasonic logging have been widely used for such
works. Systems of acoustic or optical video logging allow to record the expanded
3D image of the well wall along the entire circumference and to solve the problem
linked to the analysis of core, dealing with restoration of its orientation. Evaluation
of the mass fracture opening parameters is performed by means of acoustic
methods -- using changes in the propagation speeds of longitudinal, transverse and
surface waves, attenuation coefficients, as well as frequency and phase spectra of
elastic pulses.

      At the same time, due to the importance of rock permeability indicators
formed by the fracture system, an important task during safety assessments is to
establish correlation relationships between the degree of disturbance of the mass
and its filtration properties. Nowadays, there is only one way to establish such
correlations, which is an experimental one. This determines the need to supplement
the given scope of work by filtration methods. The change in the permeability of
the rock mass, occurring as a result of the formation of a disturbed border zone, is
estimated by the method of staged water injection in wells drilled from mines. For
the purpose of the integrated assessment of mass disturbance, drilling of such wells
shall be undertaken in close proximity to geophysical wells
(\figref{4}).           %     (Fig. 4).


     The process of establishing the intensity of the man-made fracturing
development requires the organization of performance measurements of mine
border deformations -- at the stage of sinking, with the expansion of control points
deep into the mass -- during the operation period.

\begin{figure}[t]                     % Fig 4
\figurewidth{20pc}
\setimage{}{}{20pc}{}{2019es000670-f04}
\caption{Combination of direct and indirect methods when studying the condition of the mass.}
\end{figure}


     Identification of local areas with active fracturing (and determination of the
stress strain behavior pattern) is performed on the basis of acoustic emission
method
[\itc{Brojerdi et al.,} \reflink{Broj14}{2014};
\itc{Greshnikov and Drobot,} \reflink{Gres76}{1976}].
 The method is based on the
registration of elastic waves resulting from the formation of defects under the
influence of various external and internal factors. The acoustic emission in rocks
occurs due to growth or closure of micro- and macro-fractures, pore collapse --
processes associated with changes in the structure of solids under the influence of
various external and internal factors. Defects are activated under the influence of
loads, and the defects are able to emit acoustic and emission signals long before the
occurrence of macro-destruction.

     Researches conducted from the earth's surface represent an additional set of
works at the opening sinking stage, aimed at spatial detailing of structural-tectonic
and geomechanical conditions of rocks around the openings.

\begin{sloppypar}
The method of spatial detailing of structural-tectonic and geomechanical
conditions of rocks around openings during sinking is a reverse vertical seismic
profiling. This method is widely used by the foreign URLs and presuppose the
presence of various sources of vibration originating from underground openings
[\itc{Juhlin et al.,}  \reflink{Juhl02}{2002};
\itc{Yanitsky,} \reflink{Yani79}{1979}].
For that purpose, geophones are placed at the
construction site during the research process.
\end{sloppypar}

     The emanation and helium survey serve a significant addition to the
geological and geophysical work aimed at the evaluation of the fault tectonics of
the mass. These researches, being one of the major methods of detection and
mapping of permeable deep faults, are performed to identify such zones,
assessment of their activity, assessment of the origin, dynamics and depth of
groundwater circulation pattern (including determination of the duration (time) of
water exchange) and establishment of their discharge zones
 [\itc{Tsang et al.,}  \reflink{Tsan15}{2015}].
The set of researches includes field quantitative determination of helium and radon
content in underground waters, bottom silt and soil gases and their geological and
geochemical interpretation.

\begin{sloppypar}
Thus, the implementation of the mentioned set of researches shall provide
information about the nature of fracturing from the opening border deep into the
mass, its stress condition, elastic and strength properties, anisotropy and
heterogeneity of rocks.
\end{sloppypar}


\section{Measurement of Values and Directions of Stresses in Force, Deformation
and Strength Properties}

     Stress values and their direction are the factors determining the occurrence
of water conducting fractures in the rock mass and thus forming its permeability
[\itc{Markov,} \reflink{Mark78}{1978}].

\begin{sloppypar}
Currently, there are 3 different groups of methods of studying the stress state
of rocks under conditions of their natural occurrence, which are fundamentally
different in their physical basis
[\itc{Kurlenya et al.,} \reflink{Kurl94}{1994};
\itc{AN USSR,} \reflink{ANUS82}{1982}; %Nature and methodology�, 1982            %%% ??? VA
\itc{Parfenov et al.,} \reflink{Parf84}{1984};
\itc{Siren and Hakala,} \reflink{Sire17}{2017};
\itc{Shkuratnik and Nikolenko,} \reflink{Shku12}{2012};
\itc{Tsang et al.,}  \reflink{Tsan05}{2005};
\itc{Zang,} \reflink{Zang10}{2010}]:
\begin{itemize}
\item
     tectonophysical;
\item
     geotechnical (complete or partial removal of stress, hydraulic fracturing);
\item
     geophysical (ultrasonic, seismic).
\end{itemize}
\end{sloppypar}

     Depending on the location of the measurements and the stage of the
research, it is possible to apply the methods of hydraulic fracturing, crack and end
unloading, as well as their combinations with other methods.

     Thus, when sinking vertical openings, to determine the natural stress field
and change of its components with a depth of measurement are performed at
several levels of wells drilled along the course, across the course and at an angle of
$45\deg$  to the large tectonic faults course.

     At the same time, the direction of one of the wells should coincide with the
orientation of future horizontal openings, and the other should be orthogonal to it.
In this case, the stresses parallel and perpendicular to the axes of these openings
will be determined, which is important for the calculations of their stability.

     A significant addition to these types of work on the earth's surface shall be
the implementation of high-precision compilation measurements of the location of
the structural and tectonic disturbance elements, including
[\itc{Bulange,} \reflink{Bula78}{1978};
\itc{Tatarinov et al.,} \reflink{Tata14}{2014};
\itc{Zolotarev,} \reflink{Zolo83}{1983}]:

\begin{itemize}
\item
	high-precision first class leveling of close faults;
\item
	compilation measurements of the location of the structural and tectonic
disturbance elements;
\item
\begin{sloppypar}
	linear-angular measurements and first-class leveling in geodesic
triangles.
\end{sloppypar}
\end{itemize}

     Based on these measurements, the permeable zones are allocated,
quantitative assessments of the relationship of disintegration of the rock mass due
to man-made and natural factors with hydrological and hydrogeological processes
are carried out. The reconstruction of the stress state of the rock mass as well as its
forecast considering its relation to permeability are also performed.

\section{Hydrogeological Researches}

     Another important area of work that determines the safety of waste isolation
in the underground environment is the establishment of the groundwater flow
patterns.

     The study of the hydrogeological conditions of the host rocks at the opening
sinking stage should also be performed in cycles continuously along the entire
shaft wall. The set of measurements includes a visual characterization of the rock
mass water permeability, assessment of the filtering capacity in different fractured
zones, establishing the dynamics of their water inflows
[\itc{ONKALO,} \reflink{ONKA03}{2003}].

     However, the main factor determining the filtration properties of solid rock
mass is fracturing      %.
[\itc{Chernyshev,} \reflink{Chern87}{1987};
\itc{Muller,} \reflink{Mull71}{1971}].

\begin{sloppypar}
In terms of their water permeability solid rock masses are generally
heteroogeneous and anisotropic. Water flow patterns are explained by the nature of
fracturing and the parameters of the largest fractures -- their length, opening, wall
morphology, degree and properties of the filling material. While assessing the
hydrogeological features of a mass, fractures are divided into 4 classes by the type
of a filler:
\end{sloppypar}

\begin{enumerate}
\item
open;
\item
     filled with mylonite or tectonic breccia;
\item
      lodes covered by the material chemically deposited from the solution;
\item
      filled with loose weathering products.
\end{enumerate}

     For the vast majority of rock masses water permeability is determined by
macro-fractures. Open fractures of big length and degree of openness are
characterized by the highest water permeability.

     Large fractures filled with mylonite and tectonic breccia often serve as
waterproof rock in the mass.  However, their echelon fractures in the adjacent zone
of the fault impact remain unfilled and are characterized by increased water
permeability. The release of such flows to the surface is characterized by springs
and other water seepages, which can be used to trace tectonical faults. It defines
the information content and applicability of thermal logging.

\begin{sloppypar}
Additionally, geophysical methods are widely used for solving
hydrogeological problems, the major one is the electric logging due to it being
most sensitive to changes in water saturation of rocks %. [Telford et al., 2004;Chernyak, 1987; Milsom, 2003]
[\itc{Chernyak,} \reflink{Cher87}{1987};;
\itc{Milsom,} \reflink{Mils03}{2003};
\itc{Telford et al.,} \reflink{Telf04}{2004}].
Identification of mass segments with various
water saturation is performed on the basis of the difference between their relative
electric resistance.
\end{sloppypar}

     For the purpose of determining the direction of groundwater flow during
sinking and mine operations development, in addition to the above-mentioned
methods, the liquid flow imaging method has been used internationally
[\itc{ONKALO,} \reflink{ONKA06}{2006}].

\begin{figure*}[t]                     % Fig 5
\figurewidth{35pc}
\setimage{}{}{25pc}{}{2019es000670-f05}
\caption{Functional diagram of the research using the charged body method.}
\end{figure*}


 This study is based on the measurement of the potential of
groundwater flow resulting from the interaction between moving water and the
artificial potential created by electrodes placed on the earth's surface
(\figref{5}).           %
 Thus, the
charged body method was widely used in Olkiluoto to study the location,
continuity and nature of previously identified fractured zones in the openings
area
[\itc{ONKALO,} \reflink{ONKA03}{2003}]. \vspace*{-\baselineskip}


\section{Hydrogeochemical Studies}

\begin{sloppypar}
Simultaneously with hydrogeological measurements, groundwater sampling
is performed for chemical analysis and hydrogeochemical studies. Such studies are
the ``direct'' (and most reliable) methods of establishing connection between
surface and groundwater, and are based on the tracing and comparison of the
chemical content of water in the area of accumulation and discharge.
\end{sloppypar}


\begin{sloppypar}
The chemical content of water in underground conditions is determined by
the sampling from: 1)~research wells drilled at different depths; 2)~drainage wells;
3)~seepage points on the open rock surface.
\end{sloppypar}

     To assess the conditions for the groundwater formation at the construction
site, it is necessary to organize a monitoring survey in a regular network of wells
on the earth's surface to detect deformation of the groundwater surface during
construction. Sampling of groundwater in the well network and in surface
watercourse for laboratory chemical analysis with the identification of marker
elements (detected in other points of geochemical survey) is a necessary measure
in determining the areas of groundwater accumulation and discharge.

\fitopen{1.038}
     Thus, the analysis of water samples from the areas of accumulation and
discharge shall provide an opportunity to estimate the time and speed of its flow, to
determine the relationship of surface and groundwater, to assess the impact on the
hydraulic properties of the environment and the chemical content of groundwater
in the fractured zones that contribute to rapid filtration to significant depths.

     The subsequent research of the hydrogeochemical pattern of groundwater at
the depth of the underground laboratory openings should be based on stationary
hydrodynamic points. In order to do this, at the opening sinking stage, in the
ground, walls and roof of the opening research and observation wells shall be
drilled.

\begin{figure*}[t]                     % Fig 6
\figurewidth{35pc}
\setimage{}{}{33pc}{}{2019es000670-f06}
\shortcaption{Combination of measuring and construction works.}
\end{figure*}



     Hydrodynamic points shall be established at the areas of the largest
disturbances and at the tectonic zones intersection.
\fitclose

     Such studies result in the establishment of the rock water content intervals,
their water abundance, filtration properties of various elements of the mass, as well
as the nature of the inter interval relationship and the chemical content of
groundwater and other hydrogeological data.

\section{Synchronization of Research Works With the Sinking Cycle}

     The conducted survey reveals that the indicators defined for the DGR safety
case can be obtained by direct and indirect methods. Direct methods make it
possible to obtain accurate and reliable data in local areas of the mass. Indirect
methods, performed from the earth's surface and from the openings, causing no
disturbances to the continuity of the mass, offer the opportunity to characterize
large areas. This determines the need for a set of such methods.

     At the same time, the analysis of indicators of the sinking cycle revealed that
only part of its operations in terms of duration and conditions of performance
would allow their combination with research works. The total duration of these
operations will be sufficient for performance of only a small part of the given
scope of research activities. It determines the need for a temporary, technological
and organizational link between the sinking stages and the measurement
procedures.

     One of the ways of such organization of research works (based on the
assessment of requirements for spatial and time conditions of research), in order to
reduce the load on the bottom hole area, will be their division into the following
groups
(\figref{6}):           %     (Fig. 5):             6!!!
\begin{itemize}
\item
regular inspection in the mine, repeated with each cycle of shafts
sinking;
\item
measurements that allow for work with a small backlog from the mine face;
\item
a thorough examination performed on separate elevations of shafts, or
when mine face passing through characterized sections of the mass;
\item
	long-term measurements (monitoring), including the installation of equipment.
\end{itemize}

     The final choice of methods, instrument base of measurement performance
shall be made on the basis of their comparative assessment by indicators: stability
of the measured parameter, work content, requied time spent on measurements,
availability of technology. This determines the need to develop a program of
scientific support of mining operations, one of the requirements to which will be
non-increase of the total duration of construction process.

\section{Conclusions}

\begin{enumerate}
\item
	The given review of research works in foreign URLs, as well as
contemporary requirements of safety case revealed that the study of the rock
mass condition during mining operations with the definition of its
benchmark indicators is an important stage of research.
\item
	Implementation of a representative field cycle of field studies is associated
with the need to conduct at the opening sinking stage:
in terms of detailing the geological and structural features and insulating properties
of the rock mass, accommodating underground facilities:
\begin{itemize}
\item
detailed geological documentation of rock exposures; photo record of
characteristic details of the geological structure;
\item
mapping of fractures on the basis of mass measurements of elements
of occurrence of fractures, with record of their morphology, density
relationship, openness value, content of filler, study the internal
structure of the fractured zones;
\item
special studies of the rock mass fracture openness in undisturbed
conditions;
\end{itemize}
in terms of details of geomechanical conditions of a facility placement:
\begin{itemize}
\item
special studies of rock mass stress strain behavior;
\item
high-precision compilation measurements of the location of the
structural and tectonic disturbance elements;
\end{itemize}
in terms of characteristics of hydrogeological conditions of adjacent strata:
\begin{itemize}
\item
measurements of water inflows in the fractured zones, identifying
their water inflow dynamic patterns;
\item
identification of watered and dry rock segments;
\end{itemize}
in terms of the forecast of physical and chemical conditions of interaction of
groundwater, rocks and engineering barriers materials:
\begin{itemize}
\item
groundwater sampling and preservation;
\item
\begin{sloppypar}
sampling of rocks (including filling material from disturbed areas) to
study their material composition and physical and mechanical
properties in the laboratory, formation of reference collections of rock
samples, laboratory experiments with samples;
\end{sloppypar}
\end{itemize}
in terms of assessing the impact of opening sinking work on the change in the
properties of the mass:
\begin{itemize}
\item
\begin{sloppypar}
	characterization of disturbed border zones of openings in different
parts of the mass;
\end{sloppypar}
\item
assessment of the impact of mining operations on the rock mass,
including the physical and mechanical properties and permeability of
rocks;
\item
special studies using pilot wells drilled from the mine openings, to
detail the geological conditions of mine and change of the sinking
modes.
\end{itemize}
\item %3
	Obtaining of such information is based on coordination of programs and
methods of various types of direct and indirect ways of rock mass research, including:
\begin{itemize}
\item
	comprehensive processing and joint analysis of the whole amount of
the obtained data to forecast changes in the rocks condition;
\item
	evaluation of changes in its insulating properties based on the
establishment of correlation relationships.
\end{itemize}
\item %4.	
%\begin{sloppypar}
Identifying \ the \ relationship \ between \ direct and indirect methods will provide
an opportunity to assess the initial state of a mass, and subsequently use them to
characterize changes in its properties.
%\end{sloppypar}
\item % 5.	
A wide range of measurement methods, as well as the combination of
research and construction processes impose time constraints on the experiments
and determine the need to coordinate these works. This requires development of a
program for scientific support of mining operations with appropriate adjustment of
the parameters of sinking cycle, without breaching the total construction time.
\end{enumerate}


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