Research ArticleA Case Study of Combined Drainage Consolidation-PreloadingMethods for a Highway Subgrade on Peat Soils

Yue Gui ,1 Shengjun Liu,1 Xiaqiang Qin,2 and Jianfei Wang3

1Department of Civil Engineering, Kunming University of Science and Technology, Kunming 650504, Yunnan, China2China MCC20 Group Corp. Ltd, Shanghai 201900, China3Yunnan Construction and Investment Holding Group Co., Ltd, Kunming 650504, Yunnan, China

Correspondence should be addressed to Yue Gui; gydrgui@kmust.edu.cn

Received 19 August 2020; Revised 16 October 2020; Accepted 10 November 2020; Published 1 December 2020

Academic Editor: Qiang Tang

Copyright © 2020 YueGui et al.)is is an open access article distributed under the Creative Commons Attribution License, whichpermits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

A highway project of up to 100 km/h is currently being constructed between Colombo and Katunayake International Airportacross a Sri Lankan muskeg area. At this site, peat deposit was initially 0.8∼15.3m thick and was underlain by sand, clay, or gneiss.)e ground improvement methods adopted in the project were combined drainage consolidation-preloading methods, pipe pilefoundation, and geogrids. )is paper provides a detailed insight into the implementation of combined drainage consolidation-preloading methods used in the project, including sand pile, gravel pile, and plastic drainage plate as the prefabricated verticaldrains. Periodical field-level observations were taken during the ten years, including the construction and postconstructionperiods. )e results show that peat soils’ consolidation coefficient has been increased several times to tens of times due to groundimprovement. After removing the temporary surcharge, the highway embankments did not heave and was followed by long-termsettlements totaling 1.3∼7.4 cm over the following seven years of observations. Analysis of the settlement records shows thatcombined drainage consolidation-preloading methods have helped accelerate drainage consolidation and reducepostconstruction settlement.

1. Introduction

Peat soils are distributed in 59 countries and regionsglobally, accounting for 5% and 8% of the earth’s surface area[1]. Peat soils, which have considerably high organic content,high water content, high compressibility, and low shearstrength, are considered one of the worst foundation ma-terials. )eir behavior may deviate from traditional soilbehavior rules, often unsuitable for supporting structures ofany kind. )ey mainly cause large and primary long-termsettlement [2–5] and slope stability problems under staticconditions [6–10].

When peat deposits are relatively shallow (less than 5m),excavation and replacement by granular materials arecommonly performed. However, special foundation treat-ment is usually required when the deposits are deeper or of alarge lateral extent. Combined drainage consolidation-pre-loading methods are widely accepted in soil engineering

practice [11–14]. )is technique involves removing porewater from the soil, leading to soil skeleton [15, 16].

However, the application of this method in the amor-phous peat foundation has not been reported. Given this,this paper reports the application of combined drainageconsolidation-preloading methods in the amorphous peatsoil foundation. Based on the analysis of the changes insettlement monitoring values and consolidation parameters,the foundation treatment scheme’s applicability of com-bined drainage consolidation-preloading methods (sandpile, gravel pile, and prefabricated vertical drains) inamorphous peat soil foundation is evaluated.

2. Description of the Site

Sri Lanka is an island country in the Indian Ocean with atropical monsoon climate, which is located between latitude5°55′ to 9°50′ north and longitude 79°42′ to 81°53′ east. )e

HindawiAdvances in Civil EngineeringVolume 2020, Article ID 8816619, 10 pageshttps://doi.org/10.1155/2020/8816619

mailto:gydrgui@kmust.edu.cnhttps://orcid.org/0000-0003-4067-0001https://creativecommons.org/licenses/by/4.0/https://creativecommons.org/licenses/by/4.0/https://doi.org/10.1155/2020/8816619

highway connecting Colombo, the capital of Sri Lanka, andKatunayake International Airport is adjacent to the IndianOcean, which is called the CKE principle line. )e length ofthe mainline is 25.8 kilometers, and the length of ramps andbranch lines is 4.8 kilometers; the site location is presented inFigure 1. )e project began in August 2009 and was com-pleted in September 2013. It has been open to traffic forseven years. )e aerial view of the expressway duringconstruction is provided in Figure 2(a), and the aerial viewtwo years after completion is provided in Figure 2(b).

)e project is a bidirectional four-lane highway, and thedesign speed is 100 km/h. According to the technicalspecification, the maximum residual differential settlementhad not to be more than 0.3% (100 km/h) and 0.6% (80 km/h) change in grade over longitudinally.)e postconstructionsettlement does not exceed 180mm within two years.

)e highway traverses through a muskeg area, and thesoils encountered on the project site are peat soils, organicsoils, and silt clay; the length of highway subgrade throughpeat soil is 13.7 km, and the thickness of the peat variesbetween 0.8 and 15.3m. )e peat soils contain incompletelydecayed plant fragments and fine woody fibers, formedthrough accumulation and decomposition of natural vege-tation. )e physical properties of peat soils, which weredetermined on samples taken utilizing a 7.6 cm pistonsampler, are given in Table 1. Before construction, the watertable was 0–0.5m below the ground surface.

3. Design Considerations

For roads with strict postconstruction settlement controlstandards, preloading treatment is more effective for peatsoil. It can reduce the settlements to acceptable values;furthermore, it has the advantage of resulting in an ap-preciable increase of its shear strength, which makes thepreloading technique extremely interesting for differentengineering applications.

Considering the cost and the technical feasibility of thedifferent alternatives, the combined drainage consolidation-preloading methods for the highway subgrade on peat soilsas the foundation improvement method are adopted anddrainage consolidation methods include sand pile, gravelpile, and prefabricated vertical drains. After seven years ofoperation, the ground improvement work is proved to besuccessful, and the expected residual settlements are belowthe contract’s allowable limit. In this paper, three typicalstations of K2 + 600, K4 + 900, and K6 + 500 are presented.Effectiveness of the sand piles, gravel piles, and plasticdrainage plate in the consolidation of peat soils are reportedand discussed.

In the three sections of K2 + 600, K4 + 900, and K6 + 500,the thickest part of peat soil is 13.8m and the thinnest part is2.7m. )e physical and mechanical properties of soil aregiven in Table 2.)e typical cone penetration test (CPT) plotat the test site on these sections is provided in Figures 3(a)–3(c).

According to the ground conditions, various drainagesystems including sand pile, gravel pile, and plastic drainageplate were adopted. Details of design parameters are given in

Table 3. )e typical section of the combined drainageconsolidation-preloading methods is given in Figures 4(a)–4(c).

4. Analysis of Settlement

4.1. Field Observations. Many settlement plates werearranged at the original ground to determine the subgradefoundation’s settlement during the construction and oper-ation period. )ree typical examples of the field settlementsmeasured at stations K2 + 600, K4 + 900, and K6 + 500plotted against the logarithm of time are given inFigures 5(a)–5(c). In station K2 + 600, the height of theembankment is 3.0m, the height of the surcharge is 1.5m,and the preloading time is 373 days, as shown in Figure 5(a).)e height of the embankment of section K4 + 900 is 6.5m,the height of the surcharge is 7.1m, and the preloading timeis 491 days, as shown in Figure 5(b). )e height of theembankment of section K6+ 500 is 3m, the height of thesurcharge is 1.5m, and the preloading time is 399 days, asshown in Figure 5(c).

During the construction period, the total settlement ofthe subgrade soil of the three stations varies greatly, which isrelated to the height of the embankment and the height ofsurcharge, the thickness of peat soil, the method of con-solidation and drainage, and so on. In station K4 + 900, the

Ending pointK25 + 800

KatunayakeAirport

Colom

bo

Colombo

0 1 2 3

Scale (km)

Sri Lanka

K0 + 000

Katunayake Airport

N

K19 + 894

K9 + 000K7 + 196

K6 + 500

K4 + 900

K2 + 600

CKE

prin

cipa

l lin

e

Starting point

Figure 1: Site location.

2 Advances in Civil Engineering

height of embankment is the highest and the roadbed set-tlement is as high as 1760mm.

4.2. Consolidation Parameter Analysis. )e coefficient ofconsolidation Cv is an important index to reflect the con-solidation rate of foundation soil. )e Asaoka method [17]and improved Asaoka method [18, 19] are used to calculatethe consolidation coefficient Cv of subgrade in differentproject sections. )e Sn–Sn–1 relationship of the K2 + 600

section, K4 + 900 section, and K6 + 500 section is presentedin Figures 6(a)–6(c). )e effects of both smear and well-resistance are considered in the improved Asaoka method,such that

S − St1S − St2

� e− π2Cv/4H2( )+βr( ) t1− t2( ) � e

π2Cv/4H2( )+βr( )Δt, (1)

where Cv is the coefficient of consolidation, H is the max-imum drainage distance, and Δt is the time interval for

(a) (b)

Figure 2: (a) View of expressway during construction. (b) View of expressway taken two years after construction.

Table 1: Physical properties of peat soils.

Parameters Range value Mean valueWater content, w (%) 37.0–867.5 205.4Dry unit weight, rd (g·cm− 3) 10.0–13.0 11.2Specific gravity, Gs 1.5–2.1 1.7Void ratio, e 1.1–15.3 4.3Saturation, Sr (%) 73.5–100.0 95.1Liquid limit, wL (%) 30.8–593.0 161.9Plastic limit, wP (%) 15.6–394.0 97.6Organic content, wu (%) 10.3–59.3 27.3Fibre content, wf (%) 2.5–12.4 5.5

Table 2: Physical and mechanical properties of soil.

Station SoillayersDepth(m) NSPT

Organiccontent

wu%

Watercontent

w%

Voidratioe

Coefficient ofcompressibilitya (MPa− 1)

Horizontalconsolidationcoefficient Cv(m2/year)

Verticalconsolidationcoefficient Ch(m2/year)

Secondaryconsolidationcoefficient Cαε

K2+ 600

Backfills 0–1.6 14 — — 0.6 0.2 — — —Peat 1.6–8.0 0 31.8 293.3 5.9 5.8 3.8 3.8 1.64Clay 8.0–8.3 6 5.8 32.3 0.9 0.3 — — —Gneiss 15.7–20.5 24 — — — 0.2 — — —

K4+ 900

Peat 0–5.4 0 45.4 449.3 8.1 7.9 3.5 2.6 2.31Silty clay 5.4–8.3 8 — 25.8 0.7 0.4 — — —Mediumsand 8.3–11.0 13 5.2 — 0.6 0.2 — — —

Coarsesand 11.0–13.0 14 4.3 — 0.6 0.2 — — —

Gneiss 13.0–15.2 21 — — — — — — —

K6+ 500

Peat 0–9.4 1 45.4 449.3 8.1 7.9 — — 0.43Mediumsand 9.4–13.4 5 3.6 18.5 - 0.2 — — —

Gneiss 13.4–17.7 23 — — — — — — —

Advances in Civil Engineering 3

35

Cone resistance qc ¡Á 100 (kPa)

Sleeve resistance fs (kPa)

Soiltype

(m) (m)(m)

Boreholes-LT03 at Station K2 + 600

Backfill

Peat

CH

SM

1.80–1.251.80

8.50 –7.95 6.70

14.90 –14.35 6.4015.30 –14.75 0.40

1

70 105

Geo

logi

cal

age a

nd ca

use

Stra

ta n

o.

Dep

th o

fbo

ttom

Elev

atio

nof

bot

tom

�ic

knes

sof

stra

ta

Q4me

Q4f

Q3al–m

Q1–2

1

13

25

16el

(a)

75

Soiltype

Boreholes-LT057 at station K4 + 900

Peat

CL

150 225

3.80 –3.40 3.80

8.80 –8.40 5.00

Cone resistance qc ¡Á 100 (kPa)

Sleeve resistance fs (kPa)

(m) (m)(m)

Geo

logi

cal

age a

nd ca

use

Stra

ta n

o.

Dep

th o

fbo

ttom

Elev

atio

nof

bot

tom

�ic

knes

sof

Str

ata

Q4f

Q3al–m

13

15

(b)

27

Peat

54 81

5.60 –5.00 5.60

Boreholes-LT074 at station K6 + 500

8.60 –8.00 3.00

CH

9.00 –8.40 0.40 SM

Cone resistance qc ¡Á 100 (kPa)

Sleeve resistance fs (kPa)

Soiltype

1

Geo

logi

cal

age a

nd ca

use

Stra

ta n

o.

Dep

th o

fbo

ttom

Elev

atio

nof

bot

tom

�ic

knes

sof

stra

ta

Q4f

Q3al–m

Q1–2

3

25

16

(m) (m)(m)

el

(c)

Figure 3: CPT on the section of (a) K2 + 600, (b) K4 + 900, and (c) K6+ 500.

4 Advances in Civil Engineering

Table 3: Details of design parameters.

Station Ground improvementmethods PatternDimension (standard)

(m) Spacing (m)Length(m)

Surcharge(m)

Surchargeperiod (day)

K2 + 600 SP + surcharge Regulartriangle 0.5 1.5 14 1 373

K4 + 900 GP+ surcharge Square 0.5 1.2 7.6 1.1 491K6 + 500 PDP+ surcharge Square a� 0.1, b� 0.0035 1.4 8 0.5 399Note: SP is the abbreviation of sand pile; GP is the abbreviation of gravel pile; PDP is the abbreviation of plastic drainage plate.

Backfill Backfill

Peat Peat

Peat

Clay

Medium sand

Elevation (m)

Clay

K2 + 600

Elevation (m)1.50

4.005.00

1:2 1:2

26m

Surcharge -- 1.0m sand

Sand pileSand pile

–12.5

1.0m compacted

sand blanket

Pavement

D

D

d

Sand pile (SP)–25

–20

–15

–10

–5

0

–25

–20

–15

–10

–5

0

d = 0.5m D = 1.5m

Embankment

(a)

1:2

Surcharge -- 1.0m sand

1:2

0.6

7.908.90

Gravel pile

-6.9

Pavement

K4 + 900

Peat

ClayMedium sand

Clay

Gneiss

26m

Gravel pile

D D

D

D

d

d

Gravel pile (GP) d = 0.5m D = 1.2m–25

–20

–15

–10

–5

0

Elevation (m) Elevation (m)

1.0m compacted

sand blanket

–25

–20

–15

–10

–5

0

Embankment

(b)

Figure 4: Continued.

Advances in Civil Engineering 5

1.00

2.704.20

Plastic drainage plate

-7.00

Peat

Medium sand

Gniess

Pavement

K6 + 500

1:2Surcharge -- 1.5m sand 1:2

26m

Plastic drainage plateD D

D

D

Plastic drainage plate(PDP)D = 1.4m

–25

–20

–15

–10

–5

0

Elevation (m)Elevation

(m)1.0m

compactedsand blanket

–25

–20

–15

–10

–5

0

Embankment

(c)

Figure 4: Schematic of the ground improvement method of sand piles, gravel piles, and plastic drainage plate as prefabricated verticaldrains. (a) K2 + 600; (b) K4+ 900; (c) K6 + 500 (cross-station).

Opened to traffic

K2 + 600

Final stage

Loading heightSettlement

Surcharge stage

–1000

100200300400

Load

ing

heig

ht (c

m)

–900–800–700–600–500–400–300–200

Settl

emen

t (m

m)

10 100 10001Time (day)

(a)

K4 + 900

Opened to traffic

Surcharge stage2# - loading stage

1# - loading stageFinal stage

Loading heightSettlement

–2500

250500750

1000

Load

ing

heig

ht (c

m)

–2000–1750–1500–1250–1000

–750–500

Settl

emen

t (m

m)

10 100 10001Time (day)

(b)

Figure 5: Continued.

6 Advances in Civil Engineering

K6 + 500

Loading heightSettlement

Opened to traffic

2#- surcharge stage

Final stage

1#- surcharge stage

0

100

200

300

400

500

Load

ing

heig

ht (c

m)

–400

–300

–200

–100Se

ttlem

ent (

mm

)

10 100 10001Time (day)

(c)

Figure 5: Settlement observations.

K2 + 600

Surcharge stage

Slope = β = 0.79

400

500

600

700

800

S n (m

m)

500 600 700 800400Sn–1(mm)

(a)

K4 + 900

Slope = β = 0.83

Slope = β = 0.66

Slope = β = 0.68

1#-loading stage2#-loading stageSurcharge stage

600

800

1000

1200

1400

1600

1800

S n (m

m)

800 1000 1200 1400 1600 1800600Sn–1(mm)

(b)

Figure 6: Continued.

Advances in Civil Engineering 7

settlement plot according to Asaoka [17]. )e parameter βrcan be calculated as

βr �8Cv

Fa + J + πG( d2e

, (2)

where G is the factor expressing the effect of well-resistance,G � (kh/ks)(H/dw)

2, ks is the horizontal permeability of thesmear zone, kh is the coefficient of horizontal permeability; Jis the factor expressing the effect of smear,J � ln(rs/rw)((kh/ks) − 1), Fa � (ln((n/s) + (kh/ks))lns−(3/4))(n2/n2 − 1) +(s2/n2 − 1)(1 − (kh/ks))(s2/4n2) + (kh/ks)(1/n2 − 1)(1 − (1/4n2)), n is the drain spacing ratio,s � (rs/rw), rs is the diameter of the smear zone, and rw is theequivalent diameter of the drain.

Depending on the Asaoka method and the consolidationtheory of saturated soil with vertical drainage, an inverseanalysis formula for the coefficient of consolidation isdeduced:

St2 � k1St1 + k0, (3)

where k1 � e− ((π2Cv/4H2)+βr)Δt, k0 � (1 − k1)S, and k1 � β,

where β can be obtained by the Asaoka method.

)e results of an inverse analysis of the consolidationcoefficient after the drainage consolidation treatment aresummarized in Table 4. It can be seen that the coefficient ofconsolidation (Cv) of natural peat soils from laboratory tests

K6 + 500

Slope = β = 0.52

Slope = β = 0.75

1#- surcharge stage2#- surcharge stage

240 260 280 300 320 340220Sn–1(mm)

220

240

260

280

300

320

340

S n (m

m)

(c)

Figure 6: Sn− Sn− 1 relationship.

Table 4: Results of back analysis of consolidation parameter.

Station Construction stageCv (m

2/year)

Asaoka method Improvedasaoka method

K2 + 600 Surcharge stage 421.6 268.8

K4 + 9001#-loading stage 203.3 76.12#-loading stage 219.1 82.3Surcharge stage 98.2 32.5

K6 + 500 1#-surcharge stage 56.3 16.7 0

0 K2 + 600

K4 + 900

K6 + 500

400 800 1200 1600 2000 2400 2800 32000Time (day)

75

50

25

Settl

emen

t (m

m)

75

50

25

Settl

emen

t (m

m)

20

15

10

5

Settl

emen

t (m

m) 0

Figure 7: )e long-time settlement of the subgrade by time afterremoving the surcharge.

8 Advances in Civil Engineering

is only 2.6–3.8m2/year, which shows that the consolidationcoefficient of foundation soil has increased several times totens of times after using the drainage consolidation method.From the back-calculation results, the consolidation effect ofsand pile and gravel pile drainage body is better than that ofplastic drainage plate.

4.3.PostconstructionSettlement. )e long-time settlement ofthe subgrade by time after removing the surcharge is drawnin Figure 7.

It can be seen from Figure 7; after unloading, there havenot been prominent rebound stages of the subgrade, whichwere different from the rebound phenomenon observed bySamson in the peat soil preloading project near Saint-Laurent River [20]. It experienced a period of settling sta-bilization, which was about 150, 350, and 800 days to thestations of K2 + 600, K4 + 900, and K6 + 500, respectively.After the stable settlement period, the foundation had ex-perienced the settlement increase period, but the total set-tlement amount was not large; the settlement rate was9.7mm/year, 10.9mm/year, and 1.8mm/year, respectively.However, in section K4 + 900, the settlement was close to thewarning value, worthy of great attention.

5. Conclusion

)is paper presents a case study on peat soil ground im-provement using combined drainage consolidation-pre-loading methods in Sri Lanka. )e drainage consolidationmethod (sand pile, gravel pile, and plastic drainage plate)combined with an overloading preloading scheme inamorphous peat foundation is evaluated based on the field’sstatistical analysis data. )e major conclusions drawn aresummarized as follows:

(1) )e consolidation coefficient of foundation soil hasincreased several times to tens of times after usingthe drainage consolidation method. From the back-calculation results, the consolidation effect of sandpile and gravel pile drainage body is better than thatof the plastic drainage plate.

(2) After removing the temporary surcharge, the high-way embankments did not heave and was followedby long-term settlements totaling 1.3∼7.4 cm overthe following seven years of observations.

(3) Combined drainage consolidation-preloadingmethods have been beneficial in acceleratingdrainage consolidation and reducing post-construction settlement.

Data Availability

)e data used to support the findings of this study are in-cluded within the article.

Conflicts of Interest

)e authors declare that they have no Conflicts of Interest.

Acknowledgments

)is work was supported by the National Natural ScienceFoundation of China (Nos. 51568030, 51768027, and52068039) and the Yunnan Basic Research Key Project (No.2018BC013).

References

[1] G. Mesri and M. Ajlouni, “Engineering properties of fibrouspeats,” Journal of Geotechnical and Geoenvironmental Engi-neering, vol. 133, no. 7, pp. 850–866, 2007.

[2] R. W. Day, “Performance of fill that contains organic matter,”Journal of Performance of Constructed Facilities, vol. 8, no. 4,pp. 264–273, 1994.

[3] K. Sobhan, H. Ali, K. Riedy, and H. Huynh, Field and Lab-oratory Compressibility Characteristics of Soft Organic Soils inFlorida, )e Geotechnical Special Publication, Denver, CO,USA, 2007.

[4] M. A. Ajlouni, Geotechnical Properties of Peat and RelatedEngineering Problems, Ph. D. thesis, University of Illinois,Urbana-Champaign, IL, USA, 2000.

[5] P. J. Fox and T. B. Edil, “Effects of stress and temperature onsecondary compression of peat,” Canadian GeotechnicalJournal, vol. 33, no. 3, pp. 405–415, 1996.

[6] G. Mesri, T. D. Stark, M. A. Ajlouni, and C. S. Chen, “Sec-ondary compression of peat with or without surcharging,”Journal of Geotechnical and Geoenvironmental Engineering,vol. 123, no. 5, pp. 411–421, 1997.

[7] R. Munro, Dealing with Bearing Capacity Problems on LowVolume Roads Constructed on Peat, )e Highland Council,Environmental and Community Service, HQ, Scotland, 2004.

[8] T. Qiang, Z. Yu, G. Yufeng, and G. Fan, “Use of cement-chelated solidified (MSWI) fly ash for pavement material:mechanical and environmental evaluations,” CanadianGeotechnical Journal, vol. 54, no. 11, pp. 1553–1566, 2017.

[9] N. Gofar and Y. Sutejo, “Long term compression behavior offibrous peat,” Malaysian Journal of Civil Engineering, vol. 9,no. 2, pp. 104–116, 2007.

[10] W. G. Weber, “Performance of embankments constructedover peat,” Journal of the Soil Mechanics and FoundationsDivision, vol. 95, no. 1, pp. 53–76, 1969.

[11] R. A. A. Soemitro, E. C. Leong, and H. Rahardjo, “Soil im-provement by surcharge and vacuum preloadings,” Geo-technique, vol. 50, no. 5, pp. 601–605, 2000.

[12] D. T. Bergado, J. C. Chai, N. Miura, andA. S. Balasubramaniam, “PVD improvement of soft Bangkokclay with combined vacuum and reduced sand embankmentpreloading,” Geotechnical Engineering, vol. 29, no. 1, pp. 95–122, 1998.

[13] B. Indraratna, I. Sathananthan, A. S. Balasubramaniam, andC. Rujikiatkamjorn, “Analytical and numerical modeling ofsoft soil stabilized by prefabricated vertical drains incorpo-rating vacuum preloading,” International Journal of Geo-mechanics, vol. 5, no. 2, pp. 114–124, 2005.

[14] J. Chu, S. W. Yan, and H. Yang, “Soil improvement by thevacuum preloading method for an oil storage station,”Géotechnique, vol. 50, no. 6, pp. 625–632, 2000.

[15] S. G. Kumar, G. Sridhar, R. Radhakrishnan, andR. G. Robinson, “A case study of vacuum consolidation of softclay deposit,” Indian Geotechnical Journal, vol. 9, no. 2,pp. 104–116, 2007.

[16] Q. Tang, F. Gu, Y. Zhang, Y. Zhang, and J. Mo, “Impact ofbiological clogging on the barrier performance of landfill

Advances in Civil Engineering 9

liners,” Journal of Environmental Management, vol. 222,pp. 44–53, 2018.

[17] A. Asaoka, “Observational procedure of settlement predic-tion,” Soils and Foundations, vol. 18, no. 4, pp. 87–101, 1978.

[18] Z. P. Zheng and H. L. Ma, “Study on improving inversecalculation of consolidation coefficient with Asaoka method,”Journal of Zhejiang Sci-Tech University, vol. 39, no. 3,pp. 367–371, 2018.

[19] Y. F. Deng, S. Y. Liu, and Z. S. Hong, “Study on the method ofinversion of consolidation coefficient based on settlementdata,” Rock and Soil Mechanics, vol. 26, no. 11, pp. 1807–1809,2005.

[20] L. Samson and P. L. Rochelle, “Design and performance of anexpressway constructed over peat by preloading,” CanadianGeotechnical Journal, vol. 9, no. 4, pp. 447–466, 1972.

10 Advances in Civil Engineering