December 21, 2016

3K133011

Mechanical and Environmental Properties
of Plastics-included Landfills with Elastic Behavior(Resilient)Atsushi YAMAWAKI

1

Japan Industrial Waste Management Foundation

Period of research : 2013 – 2015
Subsidy amount by the government：¥50,163,000

INTRODUCTION・・・ SLOPE STABILITY OF DEPOSITED SOLID WASTE
in Japanin JapanUpright Waste Wall (h=11.5m)

50m in height deposited (θ=40°)

High slope stability cannot be explained by the conventional method.
No collapse,
No displacement

surcharge 8.6 kN/m2

Fs=0.56
by conventional method9m(φ=38°c =5kN/m2)
63.5°

Loading Test in Shanghai

2Explanation for slope stabilityof fibrous materials-containing depositby previous research (2010-2012)
in Shanghai

Slopesliding

Fs=0.56 → 0.93
with tensile resistance(φ=38°c =5kN/m2 ζ=15°)High slope stability
can be explained bytensile resistance.
Model of fibrous materials-containing deposit31. Aims
Waste ground including plastic inside and outside of Japan

Inert waste landfill site Controlled type landfill site
(1,164 locations in Japan)(753 locations in Japan)

Measured site ofillegal dumping● Experts pointed out that
"It cannot be used because the ground is too soft“● No heavy structures have been ever built on landfills in Japan.

Our previous research has confirmed high shear strength.

Temporaldeposit site ofdisaster waste

Overseas
Landfill(in Indonesia)

Mechanical behavior of incineration
ash ground is similar to soil ground.
Unclear properties remains
on waste ground including plastic.

● To clarify the mechanical and environmental properties ofplastics-included landfills.
● To propose the investigation methods of these characteristics.
● To investigate possibility of using landfill sites.

42. Materials and Method
Study of slope stability （2010-2012）
Field data of 12 locations in 9 sites

Field tests for mechanical properties
Field data of 17 locations in 10 sites

Mechanical properties
・ strength parameters
・ settlement behavior
Study of new on-site tests
・Repose angle test
・impact acceleration test

laboratory experiment・ shake table experiment・ column experiment

Earthquake behavior
Drainage behavior

Full-scale experiment・ Installing concrete foundation
for a small wind turbine

Differential settlementEnvironmental impact“Proposed Manual for Utilization of Plastics-included Landfills”

5

3. Experiment Sites
Inert waste landfillin Tohoku districtin Kanto districtin Chubu district

Controlled type landfillin Tohoku districtin Kanto districtin Chugoku district

Overseas landfill

in Chubu districtin Turkey
6

4. Test Method
4.1 Plate load test

Plate Load Test is a fieldtest for determining theUltimate Bearing Capacityof soil and the likely
settlement under a givenload.

Given load;
0 - about 1000 kN/m2

Plate we used；dia. 0.3m - 1.0m7

4.2 Direct Shear Test

Direct shear test equipment
It can be installed on site without disturbing waste.

84.3 Impact Acceleration Test (CASPOL)
In the CASPOL test, a rammer isfallen from a height of 45 cm.
Impact acceleration is measured
by the built-in accelerometer ofthe rammer and the maximum
value is detected and expressed as
impact value (Ia).

Rammer (weight 4.5 kg
and diameter of 50 mm)

CASPOL, a simple bearing capacity measuring method for earth grounds, has been developed by the Kinki
Construction Engineering Office, Ministry of Infrastructure, Land, Transportation and Tourism of Japan.

We investigated the possibility of using CASPOL for approximate assessmentof the bearing capacity of landfills.

94.4 Repose angle test
Repose angle test we designed
is for investigating stable slope
angle .
And repose angle test isexpected to enable estimationof the bearing capacity.
Solid waste spread out by backhoe

10

Measuring slope angle

Measuring heightInert waste Landfill in Kanto

Controlled type landfill in Tohoku

Inert waste Landfill in Chubu

Landfill in Turkey

REPOSE ANGLE TESTS INSIDE AND OUTSIDE OF JAPAN11The heap piled up
with the steep angle ;Critical angle of repose

1-1.5 mSlope angle become looser; Repose angle after avalanching
12Illustrations of repose angle test

4.5 On-site air content test

Air content is expected to be related to various strength parameters.

13

5. Results
5.1 Mechanical properties
Results of strength parameters obtained from 29 locations(Next slide)

Relations between repose angle and slope stability● Slope failure or cracks occur when the slope angle exceeded the repose
angle after avalanching, provided the original ground is flat.
● It can be demonstrated that repose angle after avalanching is a guideto assess slope stability of landfills.
14plastic 54%, pottery,debris 45%
plastic 7%, soil 43%, pottery 44%
plastic 6%, soil 66%, pottery 18%

Kanto-A1
Inert
waste
landfill

Chubu-A1

plastic 17%, soil 43%, debris 28%
plastic 6%, soil 59%, pottery 30%
plastic 16%,soil/pottery 74%,
metal 4%plastc 6%, debris 50%, soil 35%
more plastics than above

Chugoku-A

Over10cmfibers

Kanto-C1
Chubu-C1 GL.2m
Illegaldumping Chubu-C1 GL.7m
Chubu-C2

Overseas
landfill

Controlled
type
landfillInternal friction
angle
Critical angle ofrepose
Repose angle
after avalanching
inclination

Cohesion

Ultimate bearing
capacity

Coefficient ofsubgradereaction

Air content°

42 16 over 2000

111

22 * 41 *

51

41 27

1.5
1.6
1.2
1.4
1.4
1.6
1.5
1.1

10
28
21
23
29
1923
25

39

340

12
24
5
8
--812824 * 41 *24
35----259
836
18
36538
1127

42
46
51
49
4656
51
46

36 27
40 27
40 27
44 27
40 27
44 27
43 27
38 2710.01.2

31 ---

---

---

34660

1.5
1.5
13.0

1.2
0.9
0.7

21 --13 --17 -----------------

451
3 * 51 *3 * 47 *53
58
55

stableFlatstableFlatstableFlatstableFlatstableFlatstableFlatstableFlatstable Inclined
surface50 90
Flatcollapse
45
60 cracksFlat
52
45 25 stable
Flat

0.5
7.0
7.0

--1.1
1.2

--- --39 --45 -----------------

--6
4

--33
43

42
-----

36 36
--63
---

37
330
21700
41
140
29320
22
--14 over 480
17 over 640

0.2

---

72 ---

---

---

---

---

55kitchen waste 49%, packaging 24%
plastic 8%, soil 73%, debris 10%
plastic 13%, soil 78%, pottery 5%
plastic 1%, soil 65%, pottery 30%
soil 80%, debris 14%, wood 6%
burnt residue
ash

0.6

1.0

45 28

---

---

4 * 52 *

0.1
0.1
0.1
0.5
0.8
0.8

1.2
1.1
1.5
1.1
1.5
1.2

31 49
26 21
19 1740 --22 39
32 38

1600
300
------565

51
9------179

Kanto-B1
Chubu-B

Tohoku-B

ash etc. (mainly soil)

Inclined

1.4

kitchen waste, plastic-bag etc.
**stable°0.115.0
0.0
0.9
1.8
8.0
15.0
0.3

Jakarta

Municipal waste Kansai-D*°

3.8Ash,Kanto-B2
soil/burnt-residue 85%, debris 12% 12.0
burntTohoku-C
debris etc. (mainly soil)
10.0
residue Illegal
Kyushu-C
halfwaydebrisetc.
(mainlysoil)
9.0(non dumping
Kyushu-C
hill-topdebrisetc.
(mainlysoil)
12.0fibers)note 1)°

plastic 50%, debris 13%
mainly debris （few plastics）
plastic 22%, soil/pottery 29%
plastic 9%, soil/pottery 52%

Disaster waste Tohoku-E
Controlledtypelandfill**

kN/m2 MN/m3 kN/m2

Chubu-C3
Shanghai GL-1m
Shanghai GL-3m

TurkeyUnder10cm

plastic 14%, soil 57%, debris 25%,rubber/leather 1%, metal 1%,
others 2%%

original ground**year g/cm3 %condition

Tohoku-A1

Composition (by weight)

Water content

Site

Wet density

Landfilltype

Deposited time

Fibers& size

Conditions of slope

40.0; by in-situ earth pressure test．（others ; by in-situ direct shear test）

1.4 --- -----over360
18 ---

---

Flat
Flat
Flat

47

stablestablestablesurface36 40collapse
36 25 stable

4238384540
38

40 --34273640 40
362736stablestablestablestable

Flat
Flat
Flat
Flat

stable

Flat

---

---

30

stableFlat

1745
333750
---

35 27
44
30
---

stable---4036 404050--------1147
45
19----over70 ---

2.0
1.4
1.7

23 ----- ---

-----

59
-----

143
18

1.1

14 --------- ---

cracks

Flat
Flat

Flat
15
Inclined(30°)

surface
Inclinedcollapse

note 2) ** ; by carry-in record. (others ; by composition investigation)

Mechanical characteristics by Landfill typeDensity of particles (g/cm3)
Impact value(by CASPOL)(Ia/5)

Water content (%)
Containing over 10cm fibers

Repose angle
after avalanching(°)

Containing under 10cm fibers

Cohesion(kN/m2)

Ash, etc. (No fibers)
Overseas landfill(Containing over 10cm fibers)

Internal friction angle (°)●The mechanical characteristics of landfill depend on the composition andsize of the waste. The mechanical characteristics vary considerably when
the waste contains long fibrous materials (plastics, etc.).
●Grounds containing fibrous materials are easily deformable and flexible,but have high shear strength and bearing capacity.

1616

Plate load test results
Settlement
loading
Inert waste landfill in Tohoku
Inert waste landfill in Kanto

Inert waste landfill in Chubu(0.9 year after deposit)
Controlled landfill in Tohoku(only ash)
Inert waste landfill in Chugoku
Inert waste landfill in Chubu(just after deposit)●Except for the Tohoku B site which comprises only ash,increased loads do not cause significant settlement. This suggeststhat the actual ultimate bearing capacities may be yet larger.

17Strength parameters across the ages
at Chubu inert waste landfill

Ultimate bearing
capacity
Impact value (Ia)
Coefficient ofsubgrade reaction
Repose angle
after avalanching
Air contentRatio
afterdeposit

Deposition time (year)●At a landfill which contains plastics of over 10 cm in length, air content
inside the ground became lower over passage of time after the depositing, andthe ultimate bearing capacity has increased remarkably.
Air content is thus believed to be related to various strength parameters.

18

5.2 Settlement characteristics of solid waste grounds

A settlement measurement was conducted at an inert waste landfill site in
Chubu district.
During April – June 2014, three new layers of solid waste were filled (totalheight :about 10 meters including two layers of intermediate cover soil) on
top of solid waste of about 20 meters in height deposited over a period of
15 years over a rock bed.

19

期
間毎の表
層沈
下量、
降水量

Settling
velocity:s (mm/day)regression
equations=9.29/(t+9.89)

Period Settlement,
Precipitation (mm)1501005000Time t (day)306090150180

Time t(day)
表層沈下量(mm)settlement

Time – Settling velocity

120

降水量(mm)precipitation

Time – Settlement, Precipitation● settlement progressed significantly during the initial period of about a month.
Then the settlement progresses along hyperbolic curve. In the left figure, when
the layer thickness is 10 m, settlement is 9 mm/year after ten years.
●The initial settlement appears to be heavily influenced by the surcharge andrainfall.

20

5.3 Seismic Earth Pressure of Waste Ground by Shaking Table Test

The situation of shaking table test

21

Outline of the experimental device

Result of the shaking table test on the waste groundwith over 10cm fibers and comparison with theprevious test on Toyoura standard sand
● The seismic earth pressure of retaining wall on the waste groundis smaller than that of the sandy ground.
● It is considered that the waste ground with plastics has resilient
property in comparison with sandy soil.

225.4 Applicability of the on-site test methods we devised
Result of Impact Acceleration Test

21 locations insideand outside of Japan
Cohesion(kN/m2)c = 2.7 Ia – 8.3(coefficient of correlation R=0.79)

Impact value (Ia)Impact values (Ia) obtained by CASPOL are related to the cohesion (c)obtained by direct shear test.

23

Influence extent confirmation test of Impact Acceleration Test
Ia
Impact value

Width (square)
Depth

Width (square) & Depth of waste layer (cm)●The extent of influence, namely the points where Ia reaches the lowest value,
is in the range of 110 cm in width (13 - 24 cm in the case or earth grounds) and40 cm in depth (earth ground 9 -22 cm). The influence is substantially more
extensive in the width direction than in the case of earth grounds.

24

Result of Repose Angle Test
18 locations insideand outside of Japan

Internalfriction
angle
by direct
shear
test
φ（°)

c ≦ 5 kN/m2

φ= 1.3 Ia – 14(coefficient of correlation R=0.55)

Repose angle after avalanching (αr)●Repose angle after avalanching is related to the angle of internal friction fromin-situ direct shear test.
●Repose angle after avalanching is almost equal to the angle of internal friction
when the cohesion (c) obtained from the direct shear test is in the range of c≦5kN/m2.

25

Critical angle of repose by landfill type
Critical angleof repose(°)

Over 10cm
fiberscontaining

Under 10cmfibers
containing

Individual value

Ash etc.
(Non fibers)

Average
26●Landfill containing plastic waste with length of 10 cm or more, the repose
angle, which indicates the stable inclination of the slope, increases considerably.
The ground is fairly stable even when its slope is sharp.

26

Relations between water content and repose angle

critical angle of repose (αc)
repose angle after avalanching (αr)αc - α rregression equation

Water content (%)●The higher is the water content, the bigger is the difference between the criticalangle of repose and the repose angle after avalanching.
●If the water content of the ground increases for the reasons of dumping of kitchen
waste and others, the repose angle after avalanching, which is the guide for actual
slope stability, diminishes considerably by the reduction of friction resistance.

27

Bearing capacities from Impact acceleration test and Repose angle test
Ultimate bearing
capacity bybearing capacity
formula (kN/m2)

except a landfill by ash
a landfill by ash
no ultimate bearing
capacity was reachedbecause no sufficientload
Ultimate bearing capacity by Plate loading test (kN/m2)

Bearing capacity formula
qu＝ic・α・c・Nc(φ)＋ir・β・r1・B・η・Nr(φ)

by Impact acceleration test

(qu：Ultimate bearing capacity)

by Repose angle test

●Ultimate bearing capacity found by the plate loading test and that calculated by substituting
the c and φ obtained by the impact acceleration test and the repose angle test into thebearing capacity formula showed certain relations.
●Impact acceleration test and repose angle test are believed to be cost effective tests forpreliminary determination of the bearing capacity in the early stage of land use project studies.

28

5.5 Water behavior in the waste ground
Drainage

Storage

Injection 100mm/30min
Injection 50mm/30min

Column experiment
Test pitting on an inert waste landfill

Time (min)Time (min)Specimen (50mm/30min)
Specimen (100mm/30min)
2cm sieve pass (50mm/30min)

Result of column experiment (t-q and t-S)

Pitting (h=2.6m) ending July 31, 2014 10:30

Slow flow

Specimen from an inert waste landfill in Kanto district

flow

rainfallstorageplastics etc.

Illustration of flow in waste ground

After 6 hours (July 31, 2014 16:50)
Water at a position 25 m higher
than the internal water level29

Flow in waste ground can be expressed by storage function
Drainage

S = K・qp
dS/dt = q
Provided, if S > C
q = qin

Storage function(K=20, p=0.2, C=45mm, t0=4min)

Where, S：Storage (height)(mm)

C：Internal storage capacity (height) (mm)K, p：Storage function constant

Column test (50mm/30min)

q ：Drainage (height)(mm)
qin：Injection (height) (mm)Time (min)Comparison of column test data andresult of storage function●Some rainwater is retained on the surface of plastics or the like inside thelandfill for a rather long period of time and then flows down slowly.
●Storage function equations reproduce the drainage fairly well, enabling
analysis on site.

30

5.6 On-site full-scale loading test
Concretefoundation

1.5m

Cover soil

Waste plastics included

Concrete foundation on a landfill in Chubu district (7m in diameter, 1m thick）
Eccentric load test (1.5 year deposit)

Generated gas test

Ordinary loadConcretefoundation

Design 32.7kN/m2
Test
34.3kN/m2

Storm load
Design 50.9kN/m2
Test
58.7kN/m2

Coversoilgravel

Assumed small wind turbine
Weight ; 9.8 kN
Hub height ; 30m
Generation capacity; 10kW
(Excel10 by TenArrows)31Ordinary load 34kN/m2

Storm load
52 – 59 kN/m2

Load

Edge of opposite loadingside on foundation

Tensile resistance by entangled plastics, etc.
Settlement(mm)（Load was received by larger horizontal area)
Time (hr)Edge of loading sideon foundation

6.5m away fromedge of foundation

Result of on-site full-scale loading test

Result of Generated gas test
TimeLocation

CH4CO2H2 S

Beforefoundation

surface

NDND

ND

0.5m awayfrom edge offoundation

ND

ND

ND

boundary

5～14ppm------------

inEccentricload test●The settlements were 4mm maximum on the foundation load side and 3mm on
the opposite side. The settlement was almost even and no uneven settlement wasobserved. One likely reason for the absence of uneven settlement in the eccentricloading test is the presence of entangled plastics and others.
●There was no change in gas generation before and after the loading test, but aslight methane was generated from the boundary between the concrete foundationand the cover soil.

32

6. Conclusions●Landfills containing long plastics and like materials are soft and prone tosettlement, but they have large friction resistance and unique tensile
resistance, both of which contribute to their high slope stability andgenerally larger ultimate bearing capacity than common earth landfills.

●Meanwhile, the repose angle test suggested that landfills which have
high, near-saturation water content have considerably poor slopestability.
●Repose angle test was found to provide a good guide to assessing theslope stability, and the simple on-site test methods of impact acceleration
and repose angle enable estimation of the ultimate bearing capacity.

33

Thank you !

In front of a landfill in Turkey.
34

Contact‘s e-mail address ; yamawaki@sanpainet.or.jp