Download Engineering geological assessment of the Diyarbakir solid waste

Bull Eng Geol Env (2005) 64: 433–440
DOI 10.1007/s10064-005-0008-z
Sedat Türkmen
Hıdayet Taga
Received: 26 March 2004
Accepted: 20 June 2005
Published online: 8 October 2005
Springer-Verlag 2005
S. Türkmen (&) Æ H. Taga
Department of Geological Engineering,
Mersin University, Mersin, Turkey
E-mail: [email protected]
Tel.: +90-324-3610102
Fax: +90-324-3610032
ORIGINAL PAPER
Engineering geological assessment of the
Diyarbakir solid waste landfill site (SE Turkey)
Abstract The paper reports a study
to investigate the geological, hydrogeological and geotechnical properties of a proposed solid waste landfill
site for Diyarbakır city, southeastern
Anatolia. The study area is located
in the vicinity of the Diyarbakır–
Mardin highway and 6 km away
from the city. The paper describes
the topography, geology and hydrogeological characteristics of the
bedrock and based on water absoprtion (Packer) and laboratory
measures, gives permeability values
for the firm to stiff clays on which
the landfill will be placed as well as
the secondary permeabilities of the
basalts and the intergranular permeabilities of the sand and gravel
layers within the claystone–mudrock
sequence. Recommendations are
made for the construction of the
landfill.
Résumé L’article présente une caractérisation géologique, hydrogéologique et géotechnique d’un site de
stockage de déchets solides pour la
ville de Diyarbakir dans le sud-est de
l’Anatolie. Le site est proche de
l’autoroute Diyarbakir-Mardin, à 6
km de la ville. L’article décrit le
contexte géologique et hydrogéologique relatif au site. A partir
d’essais d’absorption et de mesures
au laboratoire, les perméabilités des
argiles fermes à raides, sur lesquelles
le stockage sera placé, ont été précisées, de même que les perméabilités
des basaltes et celles des niveaux de
sables et graviers intercalés dans la
série argileuse. Des recommandations sont faites pour la réalisation
du stockage.
Mots clés Diyarbakir Æ Géologie de
l’ingénieur Æ Propriétés géotechniques Æ Site de stockage
Keywords Diyarbakır Æ Engineering
geology Æ Geotechnical properties Æ
Landfill site
Introduction
The purpose of this study was to determine the geological, hydrogeological, engineering and geotechnical
properties of the new Diyarbakır landfill site. The proposed landfill site is located within the Diyarbakır
Province, in south-eastern Anatolia (Fig.1), adjacent to
the Diyarbakır – Mardin highway and 6 km from the
Diyarbakır city centre. As seen in Fig. 2, the topography
varies between 600 and 705 m asl.
Landfilling constitutes a major component of solid
waste disposal systems in most countries as the disposal
system can be above or below ground water level. The
depths of landfills vary from 2 to 13 m and depend upon
the site conditions (General Elec Comp 1975). In general, there are three types of filling methods used in
operating natural attenuation-type landfills: the trench,
area and cell methods. Each of these methods is characterised by the way the site is excavated. Natural
attenuation landfills without sophisticated barriers
434
Fig. 1 Location map of the
Diyarbakır (Turkey) landfill
area
(liners) and leachate collection systems are used for
disposing non-hazardous waste only.
The basic principle of landfill operations is to spread
the waste materials and compact it in layers within a
confined area which is then covered completely with a
thin, continuous layer (minimum 150 mm). Above this is
at least 0.5 m of compacted soil designed to minimise
infiltration of surface water (Abacı 1993). Solid waste,
hazardous and non-hazardous materials are split into
three categories according to their sources. These are
industrial wastes, domestic wastes and commercial
wastes.
The population of the Diyarbakır increases every
year. According to the 1995 census, it is almost 780,000,
which is 1.7% of the Turkey’s population such that it
ranks 16th among the provinces with a population of
more than half a million (Anonymous 1998). The
increasing population is a major problem in the city as
the existing solid waste landfill site, which is a former
quarry, is situated near an urban area. Located in
basaltic rocks, the waste landfill is not secure and
threatens the environment and also causes pollution of
the ground water. As a consequence, it was decided to
create a sanitary landfill site as part of the GAP
435
Fig. 2 Engineering geological map of the Diyarbakır landfill area
Fig. 3 Geological cross section of the Diyarbakır landfill area
436
Assuming an increase in the amount of solid waste of
0.01 kg/person for each year, the compressed solid
waste density was estimated to be 0.85 t/m3 (Anonymous 1998).
Geological and Climatic Setting
Fig. 4 Composition of solid waste of the Diyarbakır city
(Southeastern Anotolian Project) Regional Transportation and Urban Project based on the US EPA (1978)
requirements. Site selection was carried out in the following three stages (Urban Sanitation and Planning
Project 1998).
(a) Preliminary stage: Field investigation of proposed
landfill sites.
(b) Second stage: Comparison of proposed landfill sites.
(c) Final stage: Landfill site selection.
An estimate of population and amount of solid
waste was made for each 5 year period to 2015.
Fig. 5 Typical layout of Diyarbakır landfill area
The study area is located on a plateau dissected by the
Tigris River. The oldest geological unit in the study area
belongs to the Upper Miocene–Pliocene and is composed of claystones, clayey sandstones, sandstones and
loosely cemented (grain supported) conglomerates with
detrital materials referred to as the Fars Formation by
Türkünal (1980). The thickness of the unit ranges between 850 and 1,000 m. The Upper Miocene–Pliocene
units are overlain by the Quaternary basalts and fluvial
deposits.
Basalt eruptions are a natural consequence of the
NNE movement of the Arabian Plate and originated
from the Karacadağ volcanic centre during Plio-Quaternary times (Ercan et al. 1991). The thickness of lava
flows decreases from northwest to southeast.
The Upper Miocene–Pliocene units are overlain by
basalt lavas in the southern part of the study area which
is bounded by a NW–SE trending mountain chain. Due
to recent erosional processes, weathering and rock
quarry operation, basalt lavas are well exposed in the
northwestern part of the hills.
A lowland area of the study site is composed of recent
organic soils, blocky soils and sandy gravelly river bank
437
Fig. 6 Schematic block diagram of the proposed sanitary landfill area
deposits (Figs. 2, 3). The proposed landfill site is composed of Tertiary units, consisting of claystones intercalated with conglomerate and sandstones. The
claystones have generally weathered into a 5 m thick
firm-stiff clayey soil which forms the base of the landfill
site.
Fig. 7 Average rainfall records of the Diyarbakır region (1950–2000)
The study area is located within the southeast Anatolian region and is classified as a seismically active zone
(ERD 1996). The cultivated soil of the Diyarbakır region is being eroded and transported from an inactive
volcanic mountain. The summer is characterised by a
hot climate, whereas the winter period is mild.
438
Table 1 Geotechnical properties of claystone (A3)
Unit and map symbol
Claystone: Diagenetic period incomplete hence not well-solidified
Geological age
Soil description
Unified soil classification
Unit weight
Surface drainage
Upper Miocene–Pliocene (Türkünal, 1980)
Brown firm-stiff clay intercalated with sand and gravel
CL: Clay of low plasticity. CS: Sandy clay. CG: Gravelly clay
19.42–21.56 kN/m3
Surface runoff generally high; however, on rolling topography small seepages
are present on many slopes
Impermeable, except in sandy and gravelly levels. Coefficient of permeability
is 9.25·10)8 m/s
3.0–21.5%
Generally few problems in upper 4 to 5 m, but shear zones and joints result
in unstable walls especially where water is present in fractures. If drainage
initated during construction period, discontinuity drainage may be insignificant
Clay matrix is resistant to erosion
Weathered zone at upper levels of excavation walls is soft to firm locally.
Unweathered zone at depth firm to stiff . Unweathered material
has shear strength values between 980–1,470 kPa
If there is no water, temporary vertical cuts generally stable
to depths of 3 to 4 m. Traces of landslides observed in the field.
Residual strength parameters should always be used for design
of permanent structures
Internal drainage and permeability
Natural water content w (%)
Excavation properties
Susceptibility to erosion
Shear strength and compressibility characteristics
Slope stability
Table 2 Geotechnical properties of silty sandy gravel (A2)
Unit and map symbol
Silty sandy gravel-A2: Terrace deposits
Geological age
Soil description
Plio-Quaternary
Primarily rounded-subrounded, very coarse-grained and coarse-grained,
locally fine-grained. Moderately well-sorted to well-sorted. As much as 3 m thick,
averaging about 1 to 2 m. Typically has lenses of sand, silt and clay commonly
up to 300 mm. Areal extent of thin beds very limited in places
GS: Sandy gravel
14.00–18.00 kN/m3
Highly permeable. Surface drainage is high
Permeability is high. Soil commonly wet and saturated locally
19.0–33.0%
Soil is weakly cemented, easily excavated
Resistant to erosion. But, sandy levels are more susceptible
Effective friction angle 35 to 40. Residual effective friction angle 30 to 35
Typically compact
If there is no water temporary vertical cuts generally stable to depths of 3 to 4 m
Remedial works necessary for permanent slopes if water content high
and soil weakly cemented locally. Residual strength parameters should always
be used for design of permanent structure
Unified soil classification
Unit weight
Surface drainage
Internal drainage and permeability
Natural water content, w (%)
Excavation properties
Susceptibility to erosion
Shear strength and
compressibility characteristics
Slope stability
Sources of waste in Diyarbakir
Engineering Geology
The main sources of solid waste in Diyarbakır are residential, commercial, construction and demolition,
industrial, municipal services and agricultural (Fig. 4).
Modern domestic waste consists of 70% biodegradable material. The amount of solid waste per
person is 0.961 kg/day with some 750,000 t/day being
generated in the city centre. The domestic solid waste
is collected and compressed within the vehicles, following which the waste is transported to the eventual
landfill site by larger trucks. A plan view of the
Diyarbakır landfill indicating the site units is given in
Figs. 5 and 6.
Six test pits (Fig. 2) were opened to determine the
engineering properties of the units and 14 samples taken
for laboratory testing following ASTM (1990). The main
engineering units are weathered claystone, intercalated
sandstone and conglomerate. These units are reddish in
colour upwards and grey to green with depth. Based on
these investigations, an engineering geological map of
the landfill site was prepared according to ISRM (1976)
and Matula (1981).
The very steep side slopes of the landfill site are
composed of weathered sedimentary and volcanic units,
classified into the following five engineering groups:
439
Table 3 Geotechnical properties of silty sand (A1)
Unit and map symbol
Silty sand-A1: Terrace deposits
Geological age
Soil description
Unified soil classification
Unit weight
Surface drainage
Internal drainage and permeability
Plio-Quaternary
Yellow-grey, poorly cemented, uniform, silty sand with some gravel
SP:Poorly graded sand, SM: Silty sand, SG: Gravelly sand
16.00–19.00 kN/m3
Surface drainage is high due to high permeability
High permeability. Coefficient of permeability is 2.5·10)2 cm/sc.
Soil commonly wet and saturated locally
16.8–26.5%
Easily excavated due to poor cementation
Extremely susceptible to erosion
Weathered material has shear strength values between 80–1,470 kN/m2 .
Peak effective friction angle of normally consolidated soils 25–35.
Residual effective friction angles commonly 17–25
Temporary slopes normally stable at 60 to depths of 3 to 4 m.
Remedial works are necessary for permanent slopes if water content
is high and soil weakly cemented
Natural water content, w (%)
Excavation properties
Susceptibility to erosion
Shear strength and compressibility
characteristics
Slope stability
1. Unit A3—Claystone—described as a firm-stiff clay.
Field observations indicate the thickness of the unit
near the landfill site is greater than 200 m, with the
strata dips varying from 15 to 25.
2. Unit A 2—Old terrace deposit—composed of loose,
well-sorted, silty, sandy gravels with no cohesion.
3. Unit A 1—Old terrace deposit—silty sand locally
observed at high altitudes in the study area. The
thickness of the unit is variable and reaches up to 5 m
at the uppermost levels.
4. Unit B—Plio-Quaternary basalts—massive structures
with flow banding. They are generally aphanitic and
composed of plagioclase and mafic minerals. The
massive basalt has a blocky structure as a consequence of cooling fractures. The orientations of the
dominant joints are N70E/84NW, N10E/80SE,
N40W/64NE and N45E/65NW. The discontinuity
sets are widely spaced and their persistence decreases
with depth. The rock mass has a secondary permeability with springs/water seepage through the discontinuities observed during the rainy season. Rock
falls and toppling failures are commonly observed
along the foot of the very steep basalt slopes.
5. Units Of and S—Unconsolidated recent units and
deposits present in troughs between the sloping flanks.
They consist of blocky, sandy, gravelly old embankment rock talus, colluvium and organic soils. The
thickness in the uppermost level ranges from 0.20 to
Table 4 Impermeability system of landfill site
Protection layer
200 mm, sand-soil
Drainage layer
for leakage water
Protection layer
Geosynthetic (impermeable)
Mineral impermeable layer
300 mm, pebble,
grain size 8–16 mm
Geotextile (600 g/cm3)
2 mm geomembrane
300 mm +300 mm,
two clay layers
3.0 m below which is a blocky soil with a clayey matrix up to 10 m in depth although in general the
maximum thickness of the unit is about 5 m. The
thickness of the cross-bedded sandstone and conglomerates may reach up to 4 m but they are usually
found as lenses within the claystone mudstone succession.
The engineering properties of the units are given in
Tables 1, 2 and 3 (ISRM 1978, 1979).
Hydrogeological Conditions at the Landfill Site
The hydrogeological data were compiled from
field observations and records from previously drilled
boreholes. The upper units and the bedrock are semipermeable and impermeable, respectively. The conglomerate and sandstone layers within the bedrock result
in a noticeable increase in the overall permeability.
The depth to the perched groundwater level varies
from 6 to 10 m with elevations averaging some 585 m
above mean sea level, ie similar to the water level in the
Tigris River. The morphological appearance of the area
is characterized by a wide valley lying between parallel
hills. The units located in the middle part of the study
area are generally impermeable. Groundwater is recharged from the valleys in the west and seeps through
open discontinuities in the basalt rock mass (Fig. 2).
Seepages are also observed along the boundary between
the basalts and the Tertiary deposits.
Water absorption (Packer) tests were carried out at
2 m intervals in the boreholes and indicated the Tertiary
deposits have permeabilities in the order of 10)6 to
10)7 m/s (3–5 lugeons). Based on the laboratory tests the
permeability coefficient of the coarse-grained soil
samples collected within the impermeable strata is
2.5·10)4 m/s and that of the fine-grained soil samples
9.25·10)8 m/s.
440
The meteorological records between 1950 and 2000
indicate the maximum rainfall is in January (monthly
mean total rainfall 77 mm). High precipitation is also
recorded in December (74.60 mm) and April (74.0 mm)
with the lowest rainfall occurring in August (1.15 mm)
and July (1.47 mm) (Fig. 7). The characteristics of the
various layers within the proposed landfill site are given
in Table 4.
Conclusions
The proposed landfill area was classified into five engineering units; weathered claystone (A3), silty-sandy
gravel (A2), silty sand (A1), basalt (B) and unconsolidated recent units (OF and S).
Surface run off is generally high and internal drainage
and permeability very low, except in the sandy and
gravely levels. However, the almost horizontally bedded
silty sandy gravels which make up the very steep slopes
have a high permeability. The Plio-Quaternary basalts in
the upper part of the area have high secondary permeabilities due to the cooling fractures/joints.
It was concluded that the geotechnical, hydrogeological and topographical properties of the proposed
landfill site indicated suitable conditions if some remedial measures are taken. In particular, it was recommended that the superficial and unconsolidated units
should be removed from the site before landfilling is
commenced as they are likely to result in differential
settlement and instability problems.
Acknowledgements The authors are very grateful to the YERCET
Company (Adana/TURKEY) for contributing data. The authors
also would like to thank Dr. Altay Acar (Cukurova University) for
his help during this study.
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