Geotechnical Properties of Waste Soil from Open ...

Geotechnical Properties of Waste Soil from Open Dumping Area in Malaysia Nur Irfah M. Pauzi PhD Research Engineer, Universiti Putra Malaysia MTDRC, Level 9, Engineering Block, Faculty of Engineering, 43400 UPM, Serdang, Selangor, Malaysia e-mail: [email protected]

Husaini Omar Associate Professor, Universiti Putra Malaysia MTDRC, Level 9, Engineering Block, Faculty of Engineering, 43400 UPM, Serdang, Selangor, Malaysia e-mail: [email protected]

Zainuddin M. Yusoff Senior Lecturer, Universiti Putra Malaysia MTDRC, Level 9, Engineering Block, Faculty of Engineering, 43400 UPM, Serdang, Selangor, Malaysia e-mail: [email protected]

ABSTRACT Waste soil consists of waste material such as concrete debris, decayed wood, plastics and others. The heterogeneous content of waste soil makes the geotechnical properties difficult to categorize and analyzed. Laboratory works such as compaction test, consolidation test, triaxial and direct shear test are conducted on waste soil to know its geotechnical properties. Based on standard proctor test, the waste soil has a maximum dry density of 1567 kg/m3 with optimum moisture content of 29%. The oedometer test shows the maximum displacement of 4 mm within 100 minutes. Based on direct shear test, the undrained cohesion is in the range of 2- 4 kPa and angle of friction of 140-27o. The triaxial test on unconsolidated undrained condition showed that the cohesion is 3 kPa and angle of friction on the range of 00 to 10.50. These geotechnical properties are important to be used for foundation design for future development at open dumping area in Malaysia.

KEYWORDS:

Geotechnical properties of waste soil, open dumping area, consolidation, settlement of waste soil, major and minor principal stress of waste soil.

INTRODUCTION In Malaysia the most preferred method of waste disposal is landfill. Most of landfill areas in Malaysia are open dumping areas (Idris et. al, 2004). The geotechnical properties of waste soil of open dumping area are important since there are so many abandoned dumping areas which are to be used for future development. The open dumping area which has no post closure maintenance such as landfill would pose serious hazards to the resident due to differential settlement of the waste soil. Estimation of settlement for municipal solid waste is critical to the successful site operation and the future development as well as to - 1205 -

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the maintenance of the sites (Park et al., 2007). Thus, geotechnical properties experimental work conducted would help in the settlement estimation and design of foundation for future development in order to understand the behavior of waste soil after closure of dumping area. Settlement and stability are believed to affect the degradation of soil. Numerous studies have been previously conducted on that settlement and stability of landfill (Sowers, 1973; Bjangard and Edgers, 1990; Edil et al., 1990; Coumoulus and Koryalos, 1997; Park and Lee, 1997; El Fadel and Khoury, 2000; Dixon et al., 2005; Reddy et al., 2009; and Sivakumar et al., 2010). However limited research was done on the geotechnical properties of waste soil from open dumping area which has the characteristics of differential settlement and high moisture content due to the ponding problems at the open dumping sites. The differences between open dumping and landfill area are in terms of its design. Landfill has a proper gas collection and leachate recirculation, top cover, daily cover, proper post closure maintenance care and proper drainage system. While open dumping area has not had all of the design aspect. The open dumping area is usually not easy to be treated due to its complexity of geotechnical properties of soil. In Malaysia, the landfills could be classified into 4 levels namely Level 1, Level 2, Level 3, and Level 4. Level 1 , controlled tipping, Level 2 is sanitary landfill with bunk embankment and daily soil covering; Level 3, sanitary landfill with leachate recirculation system; Level 4 is sanitary landfill with a leachate treatment system (Ministry of Housing and Local Government, 1990). From this level, all of the landfill in Malaysia in assessed and classified into four types; (1) dumping into water bodies, (2) open dumps; (3) landfill (level 4 landfills). The result from this assessment showed that 25% of landfill sites in municipal council districts and 59% in district councils are open dumps. The major problems from open dumping is odor, lack of daily cover causes vermin and flies at the sites. This paper described a comprehensive laboratory studies of waste soil collected from open dumping area from Sri Hartamas near the TNB substation and compared with normal soil with settlement characteristics from Bukit Chuping, Perlis. Compaction characteristics, consolidation test, direct shear test and triaxial test are determined for these two types of samples collected.

WASTE SOIL COMPOSITION AND CHARACTERISTICS Samples of waste soils are collected from open dumping area in Sri Hartamas. The samples are labeled as SHL 1, SHL 2 and SHL 3. There is also other normal soil which is collected from Bukit Chuping area which has high moisture content and settlement characteristics so that it could be compared with waste soil samples. These samples are labeled as BK 1, BK 2 and BK 3. The waste soil composition is determined by particle size distribution method. The percent of gravel, sand, silt and clay are determined based on this curve. Some percentages of concrete debris are also found in the sieve size larger than 2 mm. Table 1 show the sieve size for different types of soil based on BS 5930, 1981. Table 1: Grain size for different types of soil Type of Soil Grain Size (mm) Debris concrete particle 2–6 Gravel >2 Sand 2 to 0.06 Silt 0.06 to 0.002 Clay < 0.002

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Based on analysis of sample SHL 1, the sample consists of a bulk of waste which the sizes are more than 2 mm. Thus, the waste soils combined with gravel are 57.5%. The soil consists of 40% sand, 1.5% silt and 1% clay, 30% of concrete debris waste and 27.5% gravel. For sample SHL 2, the soil consists of 35% sand, 0% silt, 0% clay, debris concrete waste 35%, and gravel 30%. In sample SHL 3, the sample consists of 40% sand, 0% silt, 0% clay, 30% concrete debris waste, and 30% gravel. Some of the waste material that combined with clay and silt could also be found in the sample. But this result does not being captured using sieve analysis equipment. The soil BK 1 consists of 42.5% sand, 0% silt and 0% clay, 57.5% gravel. The soil BK 2 consists of 66.67% sand, 0% silt and 0% clay, 33.33% gravel. The soil BK 3 consists of 67.67% sand, 2.33% silt and 0% clay, 30% gravel. This sample is normal soil used as control parameters in order to compare the differences between the two samples. Table 2 shows the soil composition of normal soil and waste soil. Between these two samples, SHL 1, SHL 2 and SHL 3 has a soil grain size in between 0.15 mm to 2 mm and more than 2 mm. While BK 1, BK 2 and BK 3 has more than 40% of the normal soil less than 2 mm sieve size. It could be concluded that the waste soil has size more than 2 mm compared to normal soil. Figure 1 show the particle size distribution of waste soil. Figure 2 show the particle size distribution of combined result.

Sample No. Sieve Size (mm) 2.00 1.18 0.600 0.425 0.300 0.150 0.0063 Pan

Table 2: Soil composition of waste soil and normal soil SHL 1 SHL 2 SHL 3 BK 1 BK 2 BK 3 Total Percent Passed Total Percent Passed (%) (%) 42.5 35 42.5 42.5 66.67 70.00 22.5 20 22.5 22.5 41.67 42.33 12.5 12.5 12.5 7.5 20.00 21.67 10 7.5 7.5 3.75 5.00 7.33 5 2.5 2.5 1.75 1.67 4.00 2.5 0 2.5 0.25 0.00 2.33 1 0 2.5 0 0.00 2.33 0 0 2.5 0 0.00 0.00

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45 40

Percentage of Soil Passed (%)

35 30 25 SHL 1 20

SHL 2 SHL3

15 10 5 0 0.0010

0.0100

0.1000

1.0000

Sieve Size (mm)

Figure 1: Particle size distribution of waste soil

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80

Percentage of Soil Passed (%)

70 60 50

BK 1 BK2

40

BK3 30

SHL1

20

SHL2 SHL3

10 0 0.001

0.010

0.100

1.000

10.000

Sieve Size (mm)

Figure 2: Particle size distribution of waste soil and normal soil

METHOD OF TESTING In this study, the waste soil tested is not sorted and the soil is remained to have different fraction of sizes together with concrete debris, decayed wood and other unknown particles. The waste soil is tested using compaction test, oedometer test, undrained shear strength and undrained triaxial test.

Compaction Test The compaction test is carried out based on ASTM D698 Standard Proctor Test. The waste soil is added about 10% of water. The empty clean standard proctor mould is weighed. The waste soil is compacted with 25 blows for 3 layers using standard Proctor hammer. The mould together with the soil is weighted. A representative sample is taken to determine its moisture content. The test is repeated for another five determinations. A dry density is plotted against moisture content, to determine the maximum dry density and optimum moisture content.

Oedometer Test The oedometer test is used to determine the one dimensional consolidation process of waste soil. The waste soil is compacted into circular ring with diameter of 50 mm and height of 19 mm. For each load increment, the displacement versus square root of time is plotted. The weights used are 0.03 kN, 0.05 kN, 0.07 kN and 0.09 kN. The tests are conducted for about 100 minutes. The displacement is recorded for

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different square root of time until primary compression process was complete. Long term compressibility and biodegradation was beyond the scope of this study.

Undrained Shear Strength Direct shear tests were conducted to determine the undrained shear strength parameters (cohesion and friction angles) of waste soil. Tests were performed in accordance to ASTM D3080. The samples were compacted in a square shear box of 60 mm x 60 mm. The height of the box is 49 mm. The samples are then sheared at constant strain rate under 3 different normal loads: 0.03 kN, 0.05 kN and 0.07 kN.

Undrained Triaxial Test Triaxial tests were conducted to determine the undrained strength of the samples. The tests were performed according to ASTM D2850. Samples were compacted in a mold, extruded and then inserted into latex membrane. The samples were setup in the triaxial undrained unconsolidated setup. The samples were 38 mm diameter and 65 mm height. The samples were then applied confining pressure of 40 kPa, 60 kPa, 80 kPa and 100 kPa. The volume changes are recorded. The tests were repeated for two more determinations. The shearing was done at low constant strain rate of approximately (0.6% to 1.0%).

RESULTS AND DISCUSSION Compaction characteristics The compaction test result gives the maximum dry density of 1540 kg/m3 at 29% optimum moisture content. The compaction curve is shown in Figure 3. Based on Reddy et al (2009), the Standard Proctor compaction conducted at fresh landfill, Orchard USA gives maximum dry density of 420 kg/m3 at 70% moisture content. Hettiarachchi (2005) reported a maximum dry density of 525 kg/m3 at 62% optimum moisture content for a MSW sample generated in the laboratory. There were approximately 66% differences between the result of maximum dry density from open dumping area and fresh landfill. The difference is approximately 40% in the optimum moisture content. The samples from open dumping area are less moisturized due to the exposed of the samples to the air without any daily cover. The difference in the maximum particles sizes (Reddy et al. 2009) is believed to be one of the reasons responsible for the difference between the three maximum dry density values reported.

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Figure 3: Compaction curve of waste soil

In Figure 4, the compaction curves show the highest maximum dry density of 1540 kg/m3 at optimum moisture content of 29% for waste soil. The highest maximum dry density of 1486 kg/m3 at optimum moisture content of 40% for normal soil which has high content of sand and gravel. As mention previously, the different in the particle sizes reported to be the reason in the maximum dry density result.

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Compaction Curve 1700.00

Dry Density (kg/m3)

1500.00 1300.00

NS 3 NS 2

1100.00

NS 1 900.00

WS 1 WS 2

700.00

WS 3

500.00 10.00

20.00

30.00

40.00

50.00

60.00

Moisture Content (%)

Figure 4: Compaction curve for two different soils (WS and NS).

Compression behavior The compression behavior of waste soil followed by gradual time was observed and recorded during loading. The compression ratio of the sample SHL 1 with applied load of 0.09 kN, 0.07 kN, 0.05 kN and 0.03 kN are 19%, 17%, 14% and 13% respectively. Figure 5 shows the displacement versus square root of time for waste soil. The increase in loading would increase in the displacement of samples. The samples does not testing the difference in the moisture content but it tested the difference in the loading applied. Figure 6 show the comparison between the waste soil and normal soil compression behavior. This result reported that the normal soil has less displacement compared to waste soil. For Waste Soil (WS), the displacement is 3.6 mm while Normal Soil (NS) has 3.5 mm of displacement at 0.09 kN applied load at the starting of the test when (t=0). For SHL 1 at 0.03 kN loading, the displacement is varied with 2.4 mm for WS and 1.4 for NS when (t=0). The reading of displacement gradually decrease by time and became constant at 36 minutes.

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4.000 3.500 Displacement (mm)

3.000 2.500 2.000 3 kg

1.500

5 kg 1.000

7 kg

0.500

9 kg

0.000 0.00

2.00

4.00 6.00 8.00 Square Root of Time (min)

10.00

12.00

Figure 5: Displacement versus Square Root of Time for Waste Soil (WS)

4.000 3.500

Displacement (mm)

3.000 2.500 3 kg WS 5 kg WS 7 kg WS 9 kg WS 3 kg NS 5 kg NS 7 kg NS 9 kg NS

2.000 1.500 1.000 0.500 0.000 0.00

2.00

4.00 6.00 8.00 Square Root of Time (min)

10.00

12.00

Figure 6: Displacement versus Square Root of Time for Normal Soil (NS) and Waste Soil (WS)

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Undrained Shear Strength Parameters Figure 7 shows the direct shear test result for waste soil with the applied load of 3 kg, 5 kg and 7 kg. The moisture content of the waste soil is 60% to 80%. The shear stress versus displacement for the increased normal load shows an increase in the shear displacement with the increase shear stress. In Figure 8, the comparison between waste soil and normal soil shows that the waste soil has higher shear stress compared to normal stress. The higher shear stress is reported due to the different particle size and specific gravity that affected the shear displacement. The particle sizes of WS are between 2 -6 mm while NS are 2 mm – 0.01 mm as shown in Figure 2. Specific gravity for WS is 2.14 and NS is 2.53. Table 3 is tabulating the undrained cohesion values and angle of friction for normal soil and waste soil. The waste soil has higher friction angle compared to normal soil. This is reported because of the concrete debris content that increase the friction between the particles that makes the angle of friction higher. The waste soils have maximum cohesion and angle of friction of 5 kPa and 380 respectively. The normal soils have maximum cohesion and angle of friction of 4 kPa and 270. The complex content of waste soil would increase the cohesion values but the values do not varied so much. Table 3: Undrained Shear Strength parameters for WS and NS Sample No. Cohesion Angle of Friction (kPa) (o ) NS 1 (BK 1) 2 27 NS 2( BK 2) 4 17 NS 3 (BK 3) 4 14 WS 1(SHL 1) WS 2 (SHL 2) WS 3 (SHL 3)

0 4 5

38 18 11

Editor’s Note: The terms “cohesion” and “internal friction angle” are sometimes used as if they (c and φ) were two separate soil properties such as density and color---They are not; these two (c and φ) are the two parameters of the shear strength equation; they represent the shear strength property of a soil together. This parameter-pair takes on different values depending on drainage conditions and time, for the same soil.

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12.0000

Shear Stress (kN/m2 )

10.0000 8.0000 6.0000

3 kg 5 kg

4.0000

7 kg

2.0000 0.0000 0.000

2.000

4.000

6.000

8.000

10.000

Shear Displcement (mm)

Figure 7: Shear stress vs. Shear Displacement

14.0000

Shear Stress (kN/m2 )

12.0000 10.0000 NS 3 kg

8.0000

NS 5 kg NS 7 kg

6.0000

WS 3 kg 4.0000

WS 5 kg WS 7 kg

2.0000 0.0000 0.000

2.000

4.000

6.000

8.000

10.000

12.000

Shear Displcement (mm)

Figure 8: Shear stress vs. Shear Displacement for NS and WS

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Undrained Triaxial Strength Parameters The triaxial tests were done to determine the undrained shear strength parameters under different confining pressure. The Mohr’s circles are plotted to determine the angle of friction and cohesion of waste soil. Figure 9, Figure 10 and Figure 11 show the Mohr’s circles for 3 samples of waste soil namely SHL 1, SHL 2 and SHL 3. Figure 12 show the Mohr’s circle for BK 1 normal soil samples without any waste particles. The major principles stress does increase with the gradual increase of confining pressure. The highest cohesion value is 3 kPa and highest angle of friction is 10.5o. This laboratory result shows the small scale testing as to provide the general understanding on geotechnical properties of waste soil from open dumping area.

Figure 9: Mohr’s circle of waste soil (SHL 1) with σ3 = 60 kPa, σ3 = 80 kPa and σ3 = 100 kPa

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Figure 10: Mohr’s circle of waste soil (SHL 2) with σ3 = 60 kPa, σ3 = 80 kPa and σ3 = 100 kPa

Figure 11: Mohr’s circle of waste soil (SHL 3) with σ3 = 60 kPa, σ3 = 80 kPa and σ3 = 100 kPa

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Figure 12: Mohr’s circles for waste soil (BK 1) with σ3 = 60 kPa, σ3 = 80 kPa and σ3 = 100 kPa The large scale equipment is needed in order to determine the field parameters of undrained shear strength. This result does not represent 100% accuracy on the behavior of waste soil. Based on the result reported by Reddy et al. (2009), the friction angle for fresh landfill is 120 and cohesion values of 32o for total strength parameters(c and φ) , while effective stress parameters (c’ and φ’) were found to be 38 kPa and 16o. Comparing with this study, the value varies about 2o for total strength parameters. And this agreed with the result obtained. Due to the limitation of the equipment, the effective shear strength is not determined for waste soil. The validity of the laboratory test results should be examined on the in-situ test results and back analysis of field performance data. The effect of degradation on geotechnical properties of waste soil should also be investigated before any conclusion could be made. Table 4: Undrained strength parameters of waste soil, normal soil, fresh landfill soil based on triaxial testing Source Cohesion Friction Angle Stress calculation (kPa) (degrees) method SHL 1 (waste soil from open 3 0.0 TSP dumping in Sri Hartamas) SHL 2 (waste soil from open 3 10.3 TSP dumping in Sri Hartamas) SHL 3 (waste soil from open 3 10.5 TSP dumping in Sri Hartamas) BK 1 (normal soil from Perlis) 2 10.3 TSP Fresh Shredded Landfill Soil (Reddy 32 12 TSP et al., 2009) Fresh Shredded Landfill Soil (Reddy 38 16 ESP et al., 2009)

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CONCLUSION The waste soil from open dumping area near Sri Hartamas, Malaysia was tested for compaction, consolidation, shear strength properties under direct shear and triaxial testing. A maximum dry density of 1540 kg/m3 was recorded at optimum moisture content of 29%. The composition of the waste soil should be investigated before any conclusion could be made because the degradability of the soil affects the compaction curve. There were approximately 66% differences between the result of maximum dry density from open dumping area and fresh landfill from USA. The difference is approximately 40% in the optimum moisture content. The samples from open dumping area are less moisturized due to the exposed of the samples to the air without any daily cover. Consolidation test results reported that the displacement decrease gradually and became constant at 36 minutes. For Waste Soil (WS), the displacement is 3.6 mm while Normal Soil (NS) has 3.5 mm of displacement at 0.09 kN applied load at the starting of the test when (t=0). For SHL 1 at 0.03 kN loading, the displacement is varied with 2.4 mm for WS and 1.4 for NS when (t=0). Drained cohesion of waste soil varied from 2-4 kPa and angle of friction of 140-27o. The cohesion behavior is concluded based on the behavior of waste content in the soil. The waste soil has higher friction angle compared to normal soil. This is reported because of the concrete debris content that increase the friction between the particles that makes the angle of friction higher. The waste soils have maximum cohesion and angle of friction of 5 kPa and 380 respectively. The normal soils have maximum cohesion and angle of friction of 4 kPa and 270. The complex content of waste soil would increase the cohesion values but the values do not varied so much. Undrained triaxial test with increase confining pressure i.e. σ3 = 60 kPa, σ3 = 80 kPa and σ3 = 100 kPa reported that highest cohesion value is 3 kPa and highest angle of friction is 10.5o for waste soil in Sri Hartamas open dumping area. This laboratory result shows the small scale testing as to provide the general understanding on geotechnical properties of waste soil from open dumping area. The large scale equipment is needed in order to determine the field parameters of undrained shear strength. This result does not represent 100% accuracy on the behavior of waste soil. The validity of the laboratory test results should be examined on the in-situ test results and back analysis of field performance data. The effect of degradation on geotechnical properties of waste soil should also be investigated before any conclusion could be made.

ACKNOWLEDGEMENT The authors wish to thank Universiti Tenaga Nasional of Malaysia for the laboratory facilities provided for determining the behavior of waste soil. Tenaga Nasional Berhad for supporting research activities such as sampling and testing. Universiti Putra Malaysia support for the literature paper is also acknowledged.

REFERENCES 1. ASTM (American Society of Testing and Materials), 2006, Annual Book of Standards, West Conshohocken, PA 2. British Standard Code of Practice, BS 5930: 1981, Code of Practice for Site Investigation - 1219 -

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3. Bjarngard A. and Edgers L. (1990) Settlement of municipal solid waste landfills, Proc. 13th Annual Madison Waste Conf., University of Wisconsin, Madison Wis., 192-205. 4. Coumoulus D.G. and Koryalos T.P. (1997) Prediction of attenuation of landfill settlement rates with time, Proc 14th Int. Conf. on Soil Mechanics and Foundation Engineering, Vol. 3, ISSMFE, Hamburg, Germany, 1807-1811. 5. Dixon N. and Jones D.R.V. (2005) Engineering properties of municipal solid waste, Journal of Geortextiles and Geomembrane 23, 205-233. 6. Edil T.B., Ranguette V.J. and Wuellner W.W. (1990) Settlement of municipal refuse, Geotechnics of wastefills: Theory and practice, ASTM Spec. Tech. Publ., 225-239 7. El-Fadel, M. and Khoury, R. (2000) Modeling Settlement in MSW Landfills: a Critical Review, Critical Reviews in Environmental Science and Technology, 30(3), 327-361. 8. Hettiarachchi, C.H. (2005) Mechanics of Biocell Landfill Settlement, PhD Dissertation, Department of Civil and Environmental Engineering, New Jersey Institute of Technology, Newark NJ. 9. Idris A., Inanc B., and Hassan M.N. (2004) Overview of Waste Disposal and Landfill/Dumps in Asian Country, J. Mater. Cycles Waste Management, Springer-Verlag, 6:104-110. 10. Ministry of Housing and Local Government, Malaysia, (1990), Technical guidelines on sanitary landfill design and operation (draft). Technical Section of the Local Government Division, Kuala Lumpur 11. Park H.I., and Lee S.R. (1997) Long-term settlement behavior of landfills with refuse decomposition, J. Resour. Manage. Technology, 24(4), 159-165. 12. Park H.I., Park B., Lee S.R., and Hwang D. (2007) Parameter evaluation and performance comparison of MSW settlement prediction models in various landfill types, Journal of Environmental Engineering, ASCE, 64-72 13. Reddy K.R., Hettiarachchi H., Prakalla N.S., Gangathulasi J. and Bogner J.E., (2009) Geotechnical properties of fresh municipal solid waste at Orchard Hills, Landfill USA, Journal of Waste Management 29, 952-959 14. Sivakumar Babu G.L., Krishna R.R., Sandeep K. C., and Hanumanth S.K. (2010) Prediction of long-term municipal solid waste landfill settlement using constitutive model, Practice Periodical of Hazardous, Toxic, and Radioactive Waste Management, ASCE, April 2010, 139-150. 15. Sowers G.F. (1973) Settlement of waste disposal fills, Proc. 8th Int. Conf. on Soil Mechanics and Foundation Engineering, Moscow, Vol. 1, 2(2), 207-210.

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