SOIL TRANSITION MODELS | BTSYM
Proportion of cohesive soil is greater than 10%
30% 1.0 1.0 95% 0.8 0.8 0.6 0.6 0.4
Soil transition 2 Sands
Clays 0.2 5% 0.0
350 400 450 500 550 600 650 700 Ring #
-30 -28 -26 Elevation (m) -24 -22 0.4 0.2 0.0
Left, figure 4: Family of empirical cumulative distribution function curves for soil transition 2 in the
longitudinal direction and transition at ring #1100 in the face
Ring # 1100 50%
70%
number of occurrences in all realizations to the total number of realizations) in the voxel is assigned as the most-probable SU. Uncertainty in the SUs was quantified using an information-entropy-based approach, which for a system with a discrete number of probable outcomes (or categorical data outcomes) is a relative measure of ‘missing information’.
SOIL TRANSITION LOCATION UNCERTAINTY - Longitudinal Direction The quantification of soil transition location uncertainty begins with evaluating the proportion of G1/G2 and G3/G4 soils within the tunnel envelope from multiple realizations, and visualization of soil proportions and Confidence Interval (CI) bands help to do so.
The results can be interpreted quantitatively, such as
‘at ring #500, the proportion of cohesive soil (for 95% CI) within the tunnel envelope ranges between 20% and 50% of the excavated soil volume.’ The quantitative assessment adds insights on expected ground conditions and therefore helps to characterize the soil transition location uncertainty compared to the qualitative information in the GBR. With the data, the varying proportions of G1/G2 and G3/G4 at transition locations are used to generate a family of empirical cumulative distribution function (ECDF) curves. These are a stepped function and display the cumulative occurrence probability of a specific soil proportion versus ring#. ECDF curves serve as a robust tool to quantify the probability of occurrence of
P95 P95
0
-10 -20 -30 -40
0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 Ring #
Above, figure 5: The spatial location of transitions (P95) for varying cohesive and cohesionless soil proportions, superimposed on the most-probable model from geostatistical modeling. The black line shows the deterministic interpretation of the boundary between two materials from the GBR
Fall 2023 | 47
≥ 10% (G3/G4) ≥ 50% (G3/G4)
P95 P95
≥ 10% (G1/G2) ≥ 50% (G1/G2)
Transition(GBR) G.W. level
G1 (Cohesive) G2 (Cohesive)
G3 (Cohesionless) G4 (Cohesionless)
Elevation (m)
Probability of occurrence
Probability of mixed-face condition
TBM invert
TBM springline
TBM crown
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