Frost Protection for Roads and Railways

Transcription

1 Frost Protection for Roads and Railways Røros test site: 1 year of data NADim-seminar November 30, 2017 Benoit Loranger, PhD Candidate

2 Outline Introduction Frost Protection Layer Standard Røros experimental test site Results and discussion Conclusion 2

3 Introduction Frost Protection Project ( ) Frost heave problems (winters 2010 and 2011) Crushed rock material vs natural gravel? Segregation of the material? 3

4 Frost Protection Layer Prevent frost to penetrate in natural soil Maximum thickness of road: 1,8 m to 2,4 m Modified from Aksnes presentation,

5 Frost Protection Layer Material must be crushed in a controlled production. Materials up to half the thickness of the layer (never >500 mm). Material less than 90mm shall be at least 30%. Fines less than 0,063mm shall be 1-7% calculated from 90 mm. Grading uniformity coefficient Cu> = 5 (well graded). (from revised 2017 N200 design book) 5

6 Frost Protection Layer 7 1 New requirements (2017) 6

7 Roros Test site N 0 25 km Røros Test site 7

8 8 Roros Test site 8

9 Road sections Asphalt (0-8) Base (0-32) Ro-1 Ro-2 Ro-3 Ro-4 Ro-5 Ro-6 Thickness (cm) 20 4 Sub-Base (20-120) Insulation aggregates Leca Leca 0-32 Glasopor Frost protection Layer (0-120) Silt Surrounding natural terrain: Silty sand, rock boulder and top organic surface : Survey nails : Vertical deformation : Humidity gauge : Thermocouple : Flux plate

10 Percent passing, % Variation of grading curves: Road Sections Ro-1 Ro-3 3 differents grading in frost protection layers i. Ro-1: mm, Coarse ii. Ro-2: 0-32 mm, Fine iii. Ro-3: Typical Ro-1 Ro-2 Ro-3 cm ,063 0,01 0, Sieve size, mm Ro-2 Ro-3 Ro-1 32mm 120mm 500mm >30% below 90mm From: Karlis Rieksts 2016 Coarse Fine Typical mm 0-32 mm mm

11 Ro-1: mm, Ro-2: 0-32 mm, Ro-3: Coarse Fine Typical Ro-2 Ro-3 Ro-1 11

12 12 Variation of insulation material: Road Section Ro4 Ro6 2 products: Expanded clay pebbles and Foam Glass Ro-4 Ro-5 Ro-6 cm Expanded clay from Leca 0-32 mm in Ro mm in Ro-5 Leca Leca 0-32 Glasopor Foam Glass from Glasopor mm in Ro-6 80 Leca Glasopor 12 Benoit Loranger 2017, NTNU

13 Røros test site, side view: Railway section

14 Quartzite Gabbro 14

15 1 year of data CLIMATIC DATA FI: MAT (F2, F10 and F100) FI (h o C) evolution vs time in Røros Røros: 0,2 o C; 21k; 39k; 61k; Trondheim: 5,3 o C; 4k; 11k; 19k; Oslo: 6,4 o C; 5k; 12k; 21k; Bergen: 7,6 o C; 1k; 2k; 4k; Winter at Røros FI MAT = 1,3 o C 15

16 1 year of data Frost penetration depth Does FPL is actually giving expected results? Grading, insulation and mineralogy effects Looking to FDP evolution at the end of each month 16

17 5 Ro 1-3 (cm) 0 o C Depth evolution vs. time 0 Oct Nov Dec Jan Feb Mar 50 Silt FPL Sub- Base Base Ro-1 to Ro Ro-1 Ro-2 Ro-3 Vary FPL Grading Ro-1: Coarse Ro-2: Fine Ro-3: Typical Freezing Index: FPL/ Silt Ro Subgrade 17

18 Silt FPL Insulation Sub- Base Base Ro 4-6 Insulation (cm) 0 0 o C Depth evolution vs. time Oct Nov Dec Jan Feb Mar Ro-4 to Ro Insulation Ro4-6 Vary FPL insulation agg. Ro-4: Leca Ro-5: Leca 0-32 Ro-6: Glasopor Ro-4 Freezing Index: Ro-5 Ro-6 Subgrade

19 70 50 Layers thickness (cm) Varying sub-ballast grading & mineralogy: Silt FPL Subgrade Subballast Ballast 0 0 o C Depth evolution vs. time, Railway sections Nov Dec Jan Feb Mar Rw-1: mm, Quartzite; Rw-2: mm, Quartzite; Rw-3: mm, Gabbro; -250 Rw-4: mm, Gabbro; Freezing Index: Rw-1 Rw-2 Rw-3 Rw-4 19

20 20 EXPECTED VS OBSERVED Comparing necessary FI contribution to completely go through the FPL Silt layer in sections are at 2,05m Measured on site FI necessary to reach the silt layer ( C h) expected Ro-1: Ro-2: N/A Ro-3: Frost penetration depth calculated to reach 2 m: FI:

21 21 EXPECTED VS OBSERVED Comparing necessary FI contribution to completely traverse the FPL Silt layer in sections are at 2m FI necessary to reach the silt layer ( C h) Rw-1: Rw-2:10300 Rw-3: Rw-4: Frost penetration depth calculated to reach 2 m: FI:

22 1 year of data Does max thickness are enough Can better knowledge lead to better design? ($, z) Does material thermal properties are maximized? Water retention vs fine% Can cost production be optimized? Less thick layers -> less construction cost 22

23 23 Conclusions The test site is a good tool for investigating the standard assessment Data concerning frost penetration according grading, mineralogy and insulation in each sections make sense according to known theories. Contributive FI to go through FPL in Road section are higher than what expected in N200. The variation seems to be caused by the presence of water at the bottom of the layer. Contributive FI to go through the railway structure sections correspond quite well to standard evaluation. 23

24 24 Conclusions All sections of roads and railways with typical or coarse grading frost protection layer failed to prevent frost penetration inside the silt layer even with the help of water at the bottom of it FPL grading in Ro-2 and insulation material is preventing frost to reach the silt layer. Further development regarding design method is to be done. 24

25 25 13/13 Thanks to collaborators and partners The Research Council of Norway Statens vegvesen Bane Nor Leca Glasopor SINTEF Byggforsk Laval university 25