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1.
In this study,accumulation and distribution of Pb,Cu,Zn,Co,Ni,Mn and Fe in water,bottom sediments and four plant species (Myriophyllum verticillatum,Hydrocharis morsus-ranae,Nymphaea alba and Typha latifolia) were investigated in (C)ernek Lake of Kizihrmak Delta.The Kizdirmak Delta is one of the largest natural wetlands of Turkey and it is protected by the Ramsar convention since 1993.Selected physico-chemical parameters such as pH,conductivity and dissolved oxygen and also trace metal concentrations were monitored in water.All the parameters obtained were found higher than that of the national standards for the protected lakes and reserves.The accumulated amounts of various trace metals in bottom sediments and wetland plants were found in the following order of Fe ＞ Mn ＞ Zn ＞ Ni ＞ Co ＞ Cu ＞ Pb and Fe ＞ Mn ＞ Zn ＞ Ni ＞ Co respectively.The historical trace metal intake of Myriophyllum verticillatum,Hydrocharis morsus-ranae,Typha latifolia and Nymphaea alba were obtained higher than that of the toxic metal levels and these plants may be accepted as accumulators for the detected trace metals and also bioindicators in the historically polluted natural areas. 相似文献
2.
In all kinds of tunnel excavations, especially those excavated in cities, it is important to control surface settlements and prevent damage to the surface and subsurface structures. For this purpose, in weak rocks and soils, the umbrella arch method (UAM) has been used in addition to the new Austrian tunneling method (NATM). NATM and UAM are the best-known classical methods used in tunnel excavation. In classical tunneling, NATM is usually preferred in normal rocks. However, in some cases, NATM may be insufficient. UAM is a very effective alternative especially in soils and weak rocks. In soil and weak rocks, UAM is especially necessary to prevent excessive deformations. Selection of UAM or NATM is based on the following factors: cost comparison of NATM and UAM, allowable deformations, quality of rock or soil, application time of NATM and UAM, availability of skilled workers, and qualification level of the workers. Therefore, selecting the excavation method in these kinds of grounds is vital in terms of achieving the project goals in time, managing the project costs effectively, and controlling the probable deformations on nearby structures. A critical issue in successful tunneling application is the ability to evaluate and predict the deformations, costs, and project time. In this paper, application times, costs, and deformation effects are compared between NATM and UAM in sensitive regions at the Uskudar-Umraniye-Cekmekoy metro project (UUCMP). Also, efficiency of the deformation control of UAM is demonstrated by using the 2D numerical analysis method. UUCMP is part of the Istanbul metro network. The tunnels have a cross section of 75.60 m2 for NATM and 83.42 m2 for UAM. Geology in this section is composed of weak sandstone. Diabase and andesite dykes are also rarely observed. This study shows that the construction cost of UAM are 1.7 times more expensive than NATM. Although application time of UAM is 2.5 times longer than NATM, it is 2.5 times more efficient in controlling the deformations. This efficiency in controlling the deformations is confirmed via two-dimensional numerical analyses. 相似文献
3.
Interaction of longitudinal surface settlements for twin tunnels in shallow and soft soils: the case of Istanbul Metro 总被引：1，自引：1，他引：0
Ibrahim Ocak 《Environmental Earth Sciences》2013,69(5):1673-1683
Increasing demands on infrastructures increases the attention on shallow soft ground tunneling methods in urbanized areas. Especially, in metro tunnel excavations, it is important to control the surface settlements observed before and after excavation, which may cause damage to surface structures. To solve this problem, earth pressure balance machines (EPBMs) have widely been used throughout the world. This study focuses on surface settlement measurements, the interaction of twin tunnel surface settlement, and the relationship between shield parameters and surface settlement for parallel tunnels using EPBM shields in clay and sand soils. In this study, the tunnels were excavated using two EPBMs. The tunnels were 6.5 m in diameter, as twin tubes with a 14 m distance from center to center. The EPBM in the first tube followed about 100 m behind the other tube. Segmental lining with 1.4 m of length was employed as a final support. The results from this study showed that (1) the most important parameters for the maximum surface settlements are the face pressure and backfill; (2) in twin tunnel excavation with EPBM for longitudinal profile, the settlement rate reached its peak value when the shield came to the monitoring section and this peak value continued until the shield passed the monitoring section; (3) every shield affected the other tunnel’s longitudinal surface settlement profile by approximately 35–36.8 %; (4) S A, S B and S C values were found to be 38.0, 35.8 and 26.2 %, respectively for an EPBM, and (5) ensuring good construction quality is a very effective way to control face stability and minimize surface settlement. 相似文献
4.
The objective of this study is to evaluate the seismic hazard in Eastern Marmara Region using an improved probabilistic seismic hazard assessment methodology. Two significant improvements over the previous seismic hazard assessment practices are accomplished in this study: advanced seismic source characterization models in terms of source geometry and recurrence relationships are developed, and improved global ground motion models (NGA-W1 models) are employed to represent the ground motion variability. Planar fault segments are defined and a composite magnitude distribution model is used for all seismic sources in the region to properly represent the characteristic behavior of the North Anatolian Fault without the need for an additional background zone. Multi-segment ruptures are considered using the rupture model proposed by the Working Group on California Earthquake Probabilities (2003). Events in the earthquake catalogue are attributed to the fault zones and scenario weights are determined by releasing the accumulated seismic energy. The uniform hazard spectra at 10 % probability of exceedance in 50 years hazard level for different soil conditions (soil and rock) are revealed for specific locations in the region (Adapazar?, Düzce, Gemlik, Izmit, Iznik and Sapanca). Hazard maps of the region for rock site conditions at the selected hazard levels are provided to allow the readers perform site-specific hazard assessment and develop site-specific design spectrum for local site conditions. 相似文献
5.
The modulus of elasticity of intact rock (E i) is an important rock property that is used as an input parameter in the design stage of engineering projects such as dams, slopes, foundations, tunnel constructions and mining excavations. However, it is sometimes difficult to determine the modulus of elasticity in laboratory tests because high-quality cores are required. For this reason, various methods for predicting E i have been popular research topics in recently published literature. In this study, the relationships between the uniaxial compressive strength, unit weight (γ) and E i for different types of rocks were analyzed, employing an artificial neural network and 195 data obtained from laboratory tests carried out on cores obtained from drilling holes within the area of three metro lines in Istanbul, Turkey. Software was developed in Java language using Weka class libraries for the study. To determine the prediction capacity of the proposed technique, the root-mean-square error and the root relative squared error indices were calculated as 0.191 and 92.587, respectively. Both coefficients indicate that the prediction capacity of the study is high for practical use. 相似文献
6.
Calculation of surface settlements caused by EPBM tunneling using artificial neural network, SVM, and Gaussian processes 总被引：2，自引：2，他引：0
Increasing demand on infrastructures increases attention to shallow soft ground tunneling methods in urbanized areas. Especially in metro tunnel excavations, due to their large diameters, it is important to control the surface settlements observed before and after excavation, which may cause damage to surface structures. In order to solve this problem, earth pressure balance machines (EPBM) and slurry balance machines have been widely used throughout the world. There are numerous empirical, analytical, and numerical analysis methods that can be used to predict surface settlements. But substantially fewer approaches have been developed for artificial neural network-based prediction methods especially in EPBM tunneling. In this study, 18 different parameters have been collected by municipal authorities from field studies pertaining to EPBM operation factors, tunnel geometric properties, and ground properties. The data source has a preprocess phase for the selection of the most effective parameters for surface settlement prediction. This paper focuses on surface settlement prediction using three different methods: artificial neural network (ANN), support vector machines (SVM), and Gaussian processes (GP). The success of the study has decreased the error rate to 13, 12.8, and 9, respectively, which is relatively better than contemporary research. 相似文献
7.
A new approach for estimating the transverse surface settlement curve for twin tunnels in shallow and soft soils 总被引：1，自引：1，他引：0
Ibrahim Ocak 《Environmental Earth Sciences》2014,72(7):2357-2367
Increasing demand on infrastructures has led to increased attention to shallow soft ground tunneling methods in urbanized areas. Especially in metro tunnel excavations, it is important to control the surface settlements which are observed before and after excavation, which may cause damage to surface structures. Unlike motorway, sewage and other infrastructure tunnels, metro tunnels generally have to be excavated as twin tunnels and must have a larger diameter. Metro tunnels also have shallow depth. Due to their shallow depth, metro tunnels generally have been constructed in weak rocks or weak soils in cities. The construction of twin tunnels will generate ground movements which have the potential to cause damage to existing surface and subsurface structures. To solve this settlement problem, experts have used the Earth pressure balance machine (EPBM) and the slurry balance machine. In such excavations, especially in twin tunnels, the main challenges for constructers are estimating the maximum surface settlement, controlling the interaction of transverse surface settlement and shaping the settlement curve. Incorrect estimation of these parameters can lead to significant problems above the tunnels and in nearby structures. This paper focuses on surface settlement measurements, on the interaction of twin tunnel transverse surface settlement and on the relationship between shield parameters and transverse surface settlement for parallel tunnels using EPBM shields in clay and sand soils in shallow depth. Also, a new equation is proposed for estimating the transverse settlement curve of twin tunnels. The results from this proposed equation are compared with the results of field observations. The transverse settlement curve values obtained from the proposed equation have good agreement with the actual results for the Otogar–Kirazli metro case studies. 相似文献
8.
Environmental effects of tunnel excavation in soft and shallow ground with EPBM: the case of Istanbul 总被引：8，自引：4，他引：4
Ibrahim Ocak 《Environmental Earth Sciences》2009,59(2):347-352
In metro tunnel excavations, it is important to control surface settlements observed before and after excavation, which may
cause damage to surface structures. Otherwise, the metro tunnel cannot perform the task expected, and the advantages of the
tunnel are lost. In this study, short-term surface settlements and their effect on buildings are examined in three zones for
twin tunnels, which have been excavated between the Otogar and Kirazlı 1 stations of the Istanbul Metro line, and are 5.8 km
in length. Geology in the study area is composed of fill, stiff clay, dense sand, very dense sand, and hard clay, respectively,
starting from the surface. Tunnels are excavated by using two Earth Pressure Balance Tunnel Boring Machines (EPBMs) with a
6.5 m diameter as twin tubes with 14 m distance from center to center. The EPBM in the right tube is followed about 100 m
behind the other tube. Segmental lining with 1.4 m of length is currently employed as final support. The results of this study
indicate that, with EPBM excavation method in shallow depths and soft grounds, the damage done to the environment prolonged
project costs up to 15.8% more. In addition, tunnel conditions prolonged the project schedule to 29.3%. 相似文献
9.
Environmental problems caused by Istanbul subway excavation and suggestions for remediation 总被引：3，自引：0，他引：3
Ibrahim Ocak 《Environmental Geology》2009,58(7):1557-1566
Many environmental problems caused by subway excavations have inevitably become an important point in city life. These problems
can be categorized as transporting and stocking of excavated material, traffic jams, noise, vibrations, piles of dust mud
and lack of supplies. Although these problems cause many difficulties, the most pressing for a big city like Istanbul is excavation,
since other listed difficulties result from it. Moreover, these problems are environmentally and regionally restricted to
the period over which construction projects are underway and disappear when construction is finished. Currently, in Istanbul,
there are nine subway construction projects in operation, covering approximately 73 km in length; over 200 km to be constructed
in the near future. The amount of material excavated from ongoing construction projects covers approximately 12 million m3. In this study, problems—primarily, the problem with excavation waste (EW)—caused by subway excavation are analyzed and suggestions
for remediation are offered. 相似文献
10.
In this study, short-term surface settlements are predicted for twin tunnels, which are to be excavated in the chainage of
0 + 850 to 0 + 900 m between the Esenler and Kirazlı stations of the Istanbul Metro line, which is 4 km in length. The total
length of the excavation line is 21.2 km between Esenler and Basaksehir. Tunnels are excavated by employing two earth pressure
balance (EPB) tunnel boring machines (TBMs) that have twin tubes of 6.5 m diameter and with 14 m distance from center to center.
The TBM in the right tube follows about 100 m behind the other tube. Segmental lining of 1.4 m length is currently employed
as the final support. Settlement predictions are performed with finite element method by using Plaxis finite element program.
Excavation, ground support and face support steps in FEM analyses are simulated as applied in the field. Predictions are performed
for a typical geological zone, which is considered as critical in terms of surface settlement. Geology in the study area is
composed of fill, very stiff clay, dense sand, very dense sand and hard clay, respectively, starting from the surface. In
addition to finite element modeling, the surface settlements are also predicted by using semi-theoretical (semi-empirical)
and analytical methods. The results indicate that the FE model predicts well the short-term surface settlements for a given
volume loss value. The results of semi-theoretical and analytical methods are found to be in good agreement with the FE model.
The results of predictions are compared and verified by field measurements. It is suggested that grouting of the excavation
void should be performed as fast as possible after excavation of a section as a precaution against surface settlements during
excavation. Face pressure of the TBMs should be closely monitored and adjusted for different zones. 相似文献