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

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

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

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

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).

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

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

5. Obtained Results

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

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

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