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An assessment of how penetration curve adjustment affects the California bearing ratio (CBR)

Łukasz Bednarek
Łukasz Bednarek
   | 09 oct 2021
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Article Category: Original Study
Publicado en línea: 09 oct 2021
Páginas: 323 - 336
Recibido: 09 feb 2021
Aceptado: 18 may 2021
DOI: https://doi.org/10.2478/sgem-2021-0017
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© 2021 Łukasz Bednarek, published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.

Figure 1

Cross section of pavement structure (Judycki et al., 2012).
Cross section of pavement structure (Judycki et al., 2012).

Figure 2

Nomograph for determining the thickness of base and subbase layers (Çelik et al., 2017)
Nomograph for determining the thickness of base and subbase layers (Çelik et al., 2017)

Figure 3

CBR test.
CBR test.

Figure 4

Adjusted penetration curve.
Adjusted penetration curve.

Figure 5

Map of the places where samples were taken for testing (http://redstone-exploration.com/country-profiles/poland/, 2021).
Map of the places where samples were taken for testing (http://redstone-exploration.com/country-profiles/poland/, 2021).

Figure 6

The curves of grain composition of the mixtures of 0–31.5 mm.
The curves of grain composition of the mixtures of 0–31.5 mm.

Figure 7

The curves of grain composition of the mixtures of 0–63 mm.
The curves of grain composition of the mixtures of 0–63 mm.

Figure 8

Sample no. 1 of 0–31.5 mm mixture (directly after compaction).
Sample no. 1 of 0–31.5 mm mixture (directly after compaction).

Figure 9

Sample no. 2 of 0–31.5 mm mixture (directly after compaction).
Sample no. 2 of 0–31.5 mm mixture (directly after compaction).

Figure 10

Sample no. 1 of 0–31.5 mm mixture (after four days of soaking in water).
Sample no. 1 of 0–31.5 mm mixture (after four days of soaking in water).

Figure 11

Sample no. 2 of 0–31.5 mm mixture (after four days of soaking in water).
Sample no. 2 of 0–31.5 mm mixture (after four days of soaking in water).

Figure 12

Penetration curves with adjustments for 0–31.5 mm granite aggregate (sample no.1 directly after compaction).
Penetration curves with adjustments for 0–31.5 mm granite aggregate (sample no.1 directly after compaction).

Figure 13

Penetration curves with adjustments for 0–-31.5 mm granite aggregate (sample no.1 after four days of soaking in water).
Penetration curves with adjustments for 0–-31.5 mm granite aggregate (sample no.1 after four days of soaking in water).

Figure 14

Penetration curves with adjustments for 0–31.5 mm granite aggregate (sample no.2 directly after compaction).
Penetration curves with adjustments for 0–31.5 mm granite aggregate (sample no.2 directly after compaction).

Figure 15

Penetration curves with adjustments for 0–31.5 mm granite aggregate (sample no.2 after four days of soaking in water).
Penetration curves with adjustments for 0–31.5 mm granite aggregate (sample no.2 after four days of soaking in water).

Figure 16

Sample no. 1 of 0–63 mm mixture (directly after compaction).
Sample no. 1 of 0–63 mm mixture (directly after compaction).

Figure 17

Sample no. 2 of 0–63 mm mixture (directly after compaction).
Sample no. 2 of 0–63 mm mixture (directly after compaction).

Figure 18

Sample no. 1 of 0–63 mm mixture (after four days of soaking in water).
Sample no. 1 of 0–63 mm mixture (after four days of soaking in water).

Figure 19

Sample no. 2 of 0–63 mm mixture (after four days of soaking in water).
Sample no. 2 of 0–63 mm mixture (after four days of soaking in water).

Figure 20

Penetration curves with adjustments for 0–63 mm dolomite (1) aggregate (sample no.1 directly after compaction).
Penetration curves with adjustments for 0–63 mm dolomite (1) aggregate (sample no.1 directly after compaction).

Figure 21

Penetration curves with adjustments for 0–63 mm dolomite (1) aggregate (sample no.1 after four days of soaking in water).
Penetration curves with adjustments for 0–63 mm dolomite (1) aggregate (sample no.1 after four days of soaking in water).

Figure 22

Penetration curves with adjustments for 0–63 mm dolomite (1) aggregate (sample no.2 directly after compaction).
Penetration curves with adjustments for 0–63 mm dolomite (1) aggregate (sample no.2 directly after compaction).

Figure 23

Penetration curves with adjustments for 0–63 mm dolomite (1) aggregate (sample no.2 after four days of soaking in water).
Penetration curves with adjustments for 0–63 mm dolomite (1) aggregate (sample no.2 after four days of soaking in water).

Figure 24

Regression analysis results.
Regression analysis results.

Figure 25

Residuals from analysis results.
Residuals from analysis results.

Properties of the tested mixtures.

Mine Rock type Mixtures Mass fraction of passing 0.0063 mm, f [%] Flatness index, Fl [%] Shape indicator, Sl [%] Sand equivalent, SE [%] Optimum moisture content [%] Maximum dry density [g/cm3] Uniformity coefficient, Cu [−] Coefficient of gradation, Cc [−]
Dubie Dolomite (1) 0–31.5 mm 4.3 - 19.7 48.7 5.8 2.21 37.5 2.4
0–63 mm 3.3 - 14.8 47.0 6.2 2.16 44 2.1
Grochów Magnesite 0–31.5 mm 5.7 14.8 14.5 17.5 6.9 2.02 36.7 4.4
0–63 mm 6.1 13.0 12.6 18.2 7.3 1.98 56.0 5.5
Winna Góra Basalt 0–31.5 mm 4.1 49.3 63.7 50.5 6.5 2.23 16.5 1.4
0–63 mm 2.4 35.1 53.7 50.7 3.9 2.22 17.9 1.4
Rogoźnica Granite 0–31.5 mm 3.6 15.3 20.5 35.6 3.1 2.08 52.5 7.6
0–63 mm 2.7 12.9 14.5 33.7 2.1 2.05 42.4 7.4
Żelatowa Dolomite (2) 0–31.5 mm 10.9 - 31.0 18.0 6.3 2.07 193.3 12.6
0–63 mm 8.6 - 29.0 16.0 5.6 2.04 178.6 11.0
Osielec Sandstone (2) 0–31.5 mm 8.7 35.5 44.2 12.0 4.3 2.05 253.3 2.0
0–63 mm 4.6 27.2 30.0 12.0 4.7 2.02 280.0 1.4
Barcice Sandstone (1) 0–63 mm 12.7 22.5 24.4 13.0 4.5 2.10 269.8 1.6

Minimum CBR values for specific materials by layer and traffic class (Judycki et al., 2012).

Stuff Layers
Roadbase Subbase Capping layer Improved subgrade
KR1-KR2 KR3-KR4 KR5-KR7 KR1-KR2 KR3-KR7 KR1-KR2 KR3-KR7 KR1-KR7
Unbound mixtures 60 80 The layer does not exist for these traffic categories 60 25 35 20
Non-expansive soil Does not apply Does not apply 25 35 20

Regression statistics.

Coefficients Standard error t Stat p-value Lower 95% Upper 95% R square
Intersection −1.07964 0.9721 −1.11063 0.269592 −3.01004 0.850757 0.9471
CBR 1.01623 0.029785 34.1188 2.22E-54 0.957083 1.075377
SE 0.130287 0.025822 5.045615 2.23E-06 0.07901 0.181564
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