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Influence of Soft Soil Samples Quality on the Compressibility and Undrained Shear Strength – Seven Lessons Learned From the Vistula Marshlands

Jakub Konkol
Jakub Konkol
   | 30 wrz 2023
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Article Category: Special Issue 19th KKMGiIG
Data publikacji: 30 wrz 2023
Zakres stron: 262 - 281
Otrzymano: 15 sty 2023
Przyjęty: 23 cze 2023
DOI: https://doi.org/10.2478/sgem-2023-0012
Słowa kluczowe
© 2023 Jakub Konkol, published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.

Figure 1:

Schematic presentation of soft soil sample quality influence on (a) compressibility behavior and (b) undrained shear strength (Note: σv′ = effective vertical stress; ɛv = axial strain; σp′ = preconsolidation pressure; q = deviatoric stress according to Cambridge notation; p′ = effective mean stress according to Cambridge notation; p0′ = initial mean stress; CSL = critical state line).
Schematic presentation of soft soil sample quality influence on (a) compressibility behavior and (b) undrained shear strength (Note: σv′ = effective vertical stress; ɛv = axial strain; σp′ = preconsolidation pressure; q = deviatoric stress according to Cambridge notation; p′ = effective mean stress according to Cambridge notation; p0′ = initial mean stress; CSL = critical state line).

Figure 2:

Vistula Marshlands, Northern Poland.
Vistula Marshlands, Northern Poland.

Figure 3:

Soil sample quality according to different rating systems for peats (a,b,c), organic clay (d,e,f), and organic silt (g,h,i).
Soil sample quality according to different rating systems for peats (a,b,c), organic clay (d,e,f), and organic silt (g,h,i).

Figure 4:

Relationships between different SQD criteria for peats (a,b,c), organic clay (d,e,f), and organic silt (g,h,i).
Relationships between different SQD criteria for peats (a,b,c), organic clay (d,e,f), and organic silt (g,h,i).

Figure 5:

Influence of sample quality on oedometric modulus and compression index.
Influence of sample quality on oedometric modulus and compression index.

Figure 6:

Local relations of (a) Cc, (b) Cs, (c) Cs/Cc and (d) Cα with ρd0
Local relations of (a) Cc, (b) Cs, (c) Cs/Cc and (d) Cα with ρd0

Figure 7:

(a) Raw oedometer results (lab selected seating stress level is the reference one; usually approx. 5 kPa) and (b) “corrected” plots due to soil sample disturbance (in situ stress level is the reference one, here 100 kPa).
(a) Raw oedometer results (lab selected seating stress level is the reference one; usually approx. 5 kPa) and (b) “corrected” plots due to soil sample disturbance (in situ stress level is the reference one, here 100 kPa).

Figure 8:

General picture of undrained shear strength of soft soil in Vistula Marshlands: (a) UUC test results, (b) FVT tests, and (c) specific location values (Jazowa testing site).
General picture of undrained shear strength of soft soil in Vistula Marshlands: (a) UUC test results, (b) FVT tests, and (c) specific location values (Jazowa testing site).

Figure 9:

Different estimates of cu for Jazowa site.
Different estimates of cu for Jazowa site.

Jazowa testing site—different cu estimates.

Sample no Type (Δe/e0) Sampling/Testing depth [m] Soil type Test method cu [kPa] Rate cu normalized to 1%/h (1) [kPa]
1 In situ (B) 8 orSi UUC 24.2 70%/h 18.9
2 In situ (B) 9 orSi UUC 27.3 70%/h 21.3
3 In situ (B) 10 orSi UUC 28.2 70%/h 22.1
4 In situ (B) 10 orSi UUC 29.3 70%/h 22.9
5 In situ (N/A) 8.5 orSi FVT 30.7(2) 0.1°/s (700%/h) 30.7(2)
6 In situ (N/A) 9 orSi FVT 30.1(2) 0.1°/s (700%/h) 30.1(2)
7 In situ (N/A) 9 orSi FVT 28.5(2) 0.1°/s (700%/h) 28.5(2)
8 In situ (N/A) 10 orSi FVT 33.5(2) 0.1°/s (700%/h) 33.5(2)
9 Reconstituted (A) 9 orSi CK0UC 32.7 1%/h 32.7
10 Reconstituted (A) 9 orSi CK0UC 29.3 1%/h 29.3
11 Reconstituted (A) 9 orSi DSS 27.2 20%/h 22.8
12 Reconstituted (A) 9 orSi DSS 29.3 20%/h 24.5

Variability of constrained modulus and compression index for second group of soils (samples No. 4, 5, and 9).

Sample no. Eoed [kPa] Eoedcorr [kPa] Cc100–200kPa [−] Cc200–400kPa [−] ρd0 [g/cm3] Cceq.(5) [−] RE [%]
4 2949 2679 0.239 0.215 1.196 0.283 18.4
5 3311 3058 0.213 0.203 1.216 0.269 26.3
9 3125 2905 0.243 0.291 1.189 0.288 18.6
AVG 3128 2881 0.232 0.236 - - -
SD 147 155 0.013 0.039 - - -
COV 0.05 0.05 0.06 0.16 - - -

Variability of constrained modulus and compression index for first group of soils (samples No. 1, 2, 3, 6, 7, and 8).

Sample no Eoed [kPa] Eoedcorr [kPa] Cc100–200kPa [−] Cc200–400kPa [−] ρd0 [g/cm3] Cceq.(5) [ −] RE [%]
1 1468 1304 0.601 0.557 0.973 0.511 14.9
2 1342 1125 0.788 0.687 0.811 0.783 0.5
3 1565 1351 0.525 0.434 1.037 0.432 17.7
6 983 843 1.141 1.077 0.728 0.976 14.4
7 1175 973 0.951 0.816 0.673 1.127 18.6
8 1462 1240 0.583 0.536 0.982 0.499 14.4
AVG 1332 1140 0.764 0.684 - - -
SD 198 181 0.221 0.213 - - -
COV 0.14 0.16 0.29 0.31 - - -

Natural variability of the organic silt samples for oedometric tests.

Sample no Boring no Sample depth [m] Test method wc [%] ρ [g/cm3] Gs [−] Notes
1 O3 10.5–11 24h IL 50.6 1.46 2.58 Sample few cm to no.2
2 O3 10.5–11 24h IL 59.9 1.29 2.58 Sample few cm to no.1
3 O1 9.5–10 24h IL 51.4 1.57 2.57 O1 borehole is at distance of 10 m from O2
4 O2 9.5–10 24h IL 42.9 1.71 2.54 O2 borehole is at distance of 10 m from O1
5 O3 9.3–9.8 24h IL 48.0 1.80 2.58
6 O3 10–10.5 24h IL 91.0 1.39 2.46 Very variable water content and plasticity of soil in the tube
7 O4 10–10.5 24h IL 103.5 1.37 2.26 Very variable water content and plasticity of soil in the tube
8 O4 10.5–11 24h IL 55.8 1.53 2.52 -
9 O2 9.5–10 CRS* 41.2 1.68 2.57 -

Vistula Marshlands soft soils basic physical properties.

Physical/index properties Soil Standard
Organic clay Organic silt Peat
LOI 10%<LOI<30% 5%<LOI<10% LOI>30% ASTM D2974 or PN-ISO 10694
Fines ~50% of Cl and Si ~95% of Si N/A Laser diffraction method
wc 63.5±21.0 45.5±18.5 261±110.4 ASTM D2216 or PN-EN ISO 17892-1
ρ 1.58±0.16 1.74±0.18 1.17±0.27 ASTM D854 or PN-EN ISO 17892-2
Gs 2.61±0.06 2.60±0.06 2.04±0.32 ASTM D7263 or PN-EN ISO 17892-3
LL 82.5±32.1 52.0±21.0 268.9±115.7 ASTM D4318 or PN-EN ISO 17892-12
IP 50.1±25.1 29.4±13.8 159.4±87.5 ASTM D4318 or PN-EN ISO 17892-12
Casagrande's chart Along and above A-line Above A-line N/A ASTM D2487 or PN-EN ISO 14688-2

Organic clay—different estimates of cu (location No. 3).

Sample no. Type (SQD) Sampling/Testing depth [m] Soil type Test method cu [kPa] Rate
1 In situ (D) 9–10 orSi CK0UC 26.4 1%/h
2 In situ (D) 9–10 orSi CK0UC 32.7 1%/h
4 N/A 9–10 orSi SHANSEP 25±5.2 N/A

Soil specimens used in soil sample quality evaluation.

SQD (Terzaghi et al., 1966) Δe/e0 criteria (Lunne et al., 1997) Cr/Cc (deJong et al., 2018)
ɛvol at σ′vo[%] SQD class OCR 1–2 OCR 2–4 Rating Cr/Cc Rating
<1 A <0.04 <0.03 v. good to excellent (A) <0.15 High
1–2 B 0.04–0.07 0.03–0.05 good to fair (B) 0.15–0.4 Moderate
2–4 C 0.07–0.14 0.05–0.1 Poor (C) >0.4 Low
4–8 D >0.14 >0.1 Very poor (D) - -
>8 E - - - - -

Organic clay—different estimates of cu (location No. 2).

Sample no. Type (Δe/e0) Sampling/Testing depth [m] Soil type Test method cu [kPa] Rate
1 In situ (D)* 2–3 orCl CK0UC 17.0 1%/h
2 In situ (D)* 2–3 orCl CK0UC 23.4 1%/h
3 In situ (D)* 2–3 orCl CK0UE 15.2 1%/h
4 N/A 2–3 orCl SHANSEP 18.2±9.5 N/A
eISSN:
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Język:
Angielski
Częstotliwość wydawania:
4 razy w roku
Dziedziny czasopisma:
Geosciences, other, Materials Sciences, Composites, Porous Materials, Physics, Mechanics and Fluid Dynamics
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