1. Methodologies for Geotechnical Characterization in Railways in Operation.
An Experience.
Nuno Cruz, Eduardo Fortunato, Francisco Asseiceiro, Jorge Cruz, Carin Mateus

2. 1. Introduction Evaluation of mechanical behavior of railway platforms
Different means of evaluation
Foundation layers
Ballast
Usually through trial pits, bore-holes, Plate Load and DCP tests
What if…
…this as to be performed with the line in operation?
The short interdition times and the flexibility for going in and out of the railway are the major limitation to the quality of results

3. 2. Survey Principles We need specific tests that allow for
Rapid execution
Ensuring results quality
Example performed by Mota-Engil in two railway lines:
Strategy
Sena Railway Line (200 km)
Corridor of Nacala (90 km)
Georadar to characterize ballast;
22 sampling points to lab characterization;
DPSH tests to evaluate density levels of under-ballast layers;
Marchetti Dilatometer tests (DMT) when the density is of loose/soft soils;
72 sampling points to lab characterization;
72 Tests with Deflectómetro de Impacto Portátil Light Impact Defletometer (DIP)
DPSH tests to evaluate density levels of under-ballast layers;
Marchetti Dilatometer tests (DMT) when the density is of loose/soft soils
These procedures reveal themselves very efficient in terms of execution TIME, DATA QUALITY AND COSTS

4. 2. Ballast Characterization
Nacala Corridor, Section 5
Fixed to a special vehicle that can go on road or track
Tests with Georadar
2D e 3D Systems
Evaluation of thickenesses of clean and contaminated ballast;
Locating the interface between both layers;
Selection of locations for sampling and for in-situ testing;
2D very efficient distinguishing the strata
3D generates a huge amount of data
Gives na excellent answer in the evaluation of volumes

5. 3.Superficial layer characterization
Geotechnical characterization of superficial layers
Physical Characterization:
Grain size distribution;
Atterberg Limits;
Unit weight;
Moisture content;
Solids density.
Mechanical Characterization:
Light Impact Deflectometer, (DIP)
Evaluation of Deformability Modulus in the top of superficial layer
E – Deformability Modulus evaluated after 10 impacts on the same (kPa);
d – Plate diameter(m);
s – Applied stress (kPa);
d – Deflection (m).

6. 4. Characterization in depth
Evaluation in Depth
Correlation of DPSH results with SPT (they generate the same energy so directly comparable) and then to geotechnical parameters
DPSH tests in the centre line for primary evaluation of density/consistency
Density Level:
Medium to High
(NSPT >10, N20DPSH > 6,5)
Density Level :
Loose to very loose
(NSPT < 10, N20DPSH < 6,5)
NSPT = 1,5 N20DPSH
Modulus determination is too rough with dynamic tests, especially in loose/soft ground
Execution of DMT tests

7. 4. Characterization in depth
DMT tests
Deduced from Theory of Elasticity, considering a semi-espherical expansion in an elastic medium :
Test Parameters:
Material Index – ID
Dilatometer Modulus– ED
Horizontal Stress Index– KD
Pore Pressure Index- UD
ED = E / (1 – ט2) = 34,7 Δp
Introduction of correction factor– RM
Obtain Constrained Modulus – M
From M, Young Modulus or Small Strain Shear Modulus). For Poisson’s = 0.25 then EDMT ≈ 0,8M e GDMT ≈ M/3

8. 5. Obtained Results

9. Foundation Superficial Layer Characterization in depth
6. Final Considerations
Both experiences performed with the line in operation were very successful showing a sustainable methodology for characterizing soils in these specific conditions:
Ballast
Foundation Superficial Layer
Georadar
DIP Tests
Laboratory characterization
2D allowed to distinguish contaminated frome clean ballast;
3D allowed for volume determination.
Evaluation of compaction level and modulus at the surface layer
Characterization in depth
Medium to high density
Low density
DPSH tests
DMT tests
Continuous profiles with rough quality
High quality continuous profiles

10. 6. Final Considerations High Quality of the final result,
Comparison with traditional approaches the adopted methodology, using geo-radar, DIP, DMT, DPSH and laboratorial tests:
High Quality of the final result,
Shorter Time of execution
Lower Costs

11. Thanks for your attention