Statistical pre-processing and analyses of hydrometeorologic time series in a geologic clay site (methodology and first results for Mont Terri

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Statistical pre-processing and
analyses of hydrometeorologic time series in a
geologic clay site (methodology and first
results for Mont Terris PP experiment)H. Fatmi 
1, R. Ababou 1, J.M. Matray 2 1 Institut de
Mécanique des Fluides de Toulouse, Allée du
Professeur Camille Soula, 31400 Toulouse, France.
Email  fatmi_at_imft.fr ababou_at_imft.fr 2
IRSN - Institut de Radioprotection et de Sûreté
Nucléaire, Av. General Leclerc, BP n17, 92262
Fontenay-aux-Roses, France. Email 
jean-michel.matray_at_irsn.fr
Geologic cross-section (x,z) at Mont Terri
Study site the Mont Terri underground laboratory
in Switzerland (Jura)
3D positioning of tunnel, galleries and boreholes
at Mont Terri
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Statistical Analyses of Time Series Statistical
Analyses of (Pre-Processed) Signals,and
Identification of Clay Material Properties.
Pre-Processing of Time Series
Objective of this work. The Mont Terri time
series (pATM(ti), p1(ti), ...) are affected by
several defects common to many such data banks.
These defects need to be (i) detected and
(ii) corrected. Here, the problems are (i)
Missing data (e.g., isolated gaps, but also, much
longer gaps involving hundreds of time steps).
(ii) Variable time step ?t(i) (e.g. 
?t  1 min, 30 min, 4 days) . (iii) Outliers or
spurious data (aberrations), affected by very
large measurement errors and bias, e.g.
defective instruments or uncontrolled human
intervention (for example, negative values of
PATM). Note  Missing data and variable time
step can be interchanged in some cases. Indeed,
the raw time series from Mont Terri contain
explicit markers of missing data and have a
variable sampling time step. In some cases, it
may be necessary to pre-process the raw signals
for the specific purpose of re-classifying
unreasonably large time steps ?t(i) as additional
missing data.
Pre-processed time series X(t) p(t)-pATM(t)
and Y(t) pATM(t)

• General objectives
• Evaluate direct and coupled pressure transfer
  processes involving fluctations of pore pressure
  under the influence of natural forcings (earth
  tides, barometric fluctuations, rainfall,
  humidity,...) at various time scales.
• Specific objectives
• Estimate the hydraulic properties (specific
  storativity, compressibility, porosity, ...) of
  Mont Terri opaline clays, as well as their
  evolution in time over long time scales, and
  compare them to properties estimated from
  hydraulic tests (pulse and slug tests conducted
  over short time scales).

Flowchart of Pre-Processing Tasks
Application (I) identification of SS (m-1)
Raw pressure signal (1 month)
Pre-processed signal (15 months)
Pre-processing example reconstruction of
atmospheric pressure signal
Reduced spectrum of ?PP1(t), the first
difference of relative pore pressure PP1(t) (kPa)
at Mont Terri. Time span Tmax ? 1 month (from
02/08/2002 to 04/09/2002). Time step ?t  30 min
(sampling step k1).
Reduced spectrum of ?PP1(t), the first
difference of relative pore pressure (kPa) at
Mont Terri. Time span 15 months (from
29/01/2004 to 12/04/2005). Time step of
pre-processed signal ?t 30 min (and k1).
Multiresolution wavelet analyzis time evolution
of one of the dyadic components of PP1(t),
obtained at time scale T8h (near 12h). Note
unprocessed signal with Tmax? 1 month and ?t
30 min (same as above).
Multiresolution wavelet analyzis time evolution
of one of the dyadic components of PP1(t)
obtained at time scale T8h (near 12h). Note
pre-processed signal with Tmax? 15 months and ?t
30 min (same as above).
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