Science Journal of Civil Engineering and Architecture ISSN:2276-6332 Published By Science Journal Publication International Open Access Publisher http://www.sjpub.org/sjcea.html © Author(s) 2014. CC Attribution 3.0 License. Volume 2014, Article ID sjcea-165, 8 Pages, 2014. doi: 10.7237/sjcea/165 Research Article USING NEURAL NETWORKS FOR THE PREDICTION OF PERMEABILITY IN ROCK FOR DERIK EMBANKMENT EARTH DAM Houtan Jebelli ¹, Melika sharifironizi², Vandad Mazarei³ and Esmail Aflaki⁴ ¹Department of Construction Engineering, University of Nebraska-Lincoln ,NE,US E-mail:jebelli.houtan@huskers.unl.edu ²Department of Civil & Environmental Engineering & Earth Sciences, University of Notre Dame, Notre Dame, IN 46556, US. E-mail:Msharifi@nd.edu ³Department of Civil and Environmental Engineering, Oregon State University, OR, US Email:Vandad@aut.ac.ir ⁴Department of Civil and Environmental Engineering, Amirkabir University of Technology, Tehran, Iran E-mail: eaflaki@aut.ac.ir Accepted 27�� February, 2014 ABSTRACT In this study, an artificial neural network has been modeled that is able to predict the permeability of the jointed rocks of the Derik embankment earth dam in the north west of Iran. In jointed rocks the nonlinear relationship exists between the absorption rate and pressure so water pressure test frequently used for evaluating the permeability of jointed rock masses. Different pressures were used during the water pressure test that may result changes in the behavior of rock masses. An artificial neural network is a biologically inspired computing method that is capable of predicting the permeability values of rock masses with high accuracy. The neural networks have shown high potential in interpreting the raw data obtained from Leugon test and predicting the final permeability of a testing section in a borehole. The result showed that, the network that contains five hidden neurons has the best results among other networks and the neural networks are capable of predicting permeability values of jointed rock with high accuracy. This method can be used to analyze the permeability of jointed rocks of dams and grouting zones. KEYWORDS:Permeability, Artificial Neural, Network, jointed rocks, water pressure test INTRODUCTION One of the most important parameters that used for the design of large structures like dams and water reservoirs is the permeability (Ewert, 1985). Knowledge of Permeability has got a paramount importance as one of the petrophysical parameters of a rock that cannot be over emphasized; however, the estimation of formation of permeability without actual laboratory measurement of cores or interruption in production is one of the basic problems (Osmanet al., 2001) In natural rocks, permeability depends on several orders of magnitude. It is usually obtained from direct measurements on core samples or from empirical models that relates permeability to parameters calculated from well logs like porosity and water saturation. The first method is very expensive and in the second method, the coefficients of the equations must be defined for every well and the equation obtained for one formation does not perform well in the other fields (Salanet al., 1995). One of the widely accepted methods is the water pressure test that was introduced by Lugeon (Lugeon, 1933).It is a pump-in test where the volume of water is taken in a section Corresponding Author: Houtan Jebelli Department of ConstructionEngineering, University of Nebraska-Lincoln ,NE,US E-mail:jebelli.houtan@huskers.unl.edu of a borehole and measured during given time intervals (Hashemi, 2006). The use of artificial neural network eliminates some of the problems associated with costs and generalization of developed models for the prediction of permeability distribution. The artificial neural network was designed and trained to acceptably predict the permeability without overall reliable results. (Edison, 2000) An alternative approach to the parametric modeling approach is the application of artificial neural networks (ANNs). In recent year, ANNs have emerged as powerful tools for modeling complex systems (Jamial ahmadi, Javadpour, 2000) Parametric methods like statistical regression require the assumption and satisfaction of multi-normal behavior and linearity. Therefore, neural network as a non-linear and non-parametric tool is becoming increasingly popular in well log analysis. The neural network is a computer model that attempts to mimic simple biological learning processes and simulate specific functions of human nervous system. The neural network can be used as a nonlinear regression method to develop transformation between the selected well logs and core analysis data. ( Jong-Se Lim , 2005) Artificial neural networks are a large class of parallel processing architectures, which can mimic complex and non-linear relationships through the application of many non-linear processing units called neurons. The relationship can be 'learned' by a neural network through adequate training from the experimental data (Lin et al., 2008).Artificial neural network provides a parameterized, non-linear mapping between inputs and output. . It has the inherent capability to deal with fuzzy, non-linear, whose functional relations are not clear (Mandal et al., 2007). Geology of the dam site Derik dam is located in the north west of Iran at the latitude 44̊.38N and the longitude 38˚.10E. It has been constructed on the Derik River, one of the Ashnak river branches. A data bank containing a large number of data points was compiled over a wide range of reservoir depth, porosity and Science Journal of Civil Engineering and Architecture( ISSN:2276-6332) page 2 permeability. The basin formed in surface deposit mainly of sediments of the Cretaceous Derik formations and is typically clay-marl and shale as is shown in Fig 1. More recent geological deposits are alluvium sediments in the valley bottom (Geological survey of Iran, 1985). A geological section of the formations along the axis of the Derik river dam is shown in Fig 1. Results of several site investigations show four faults on the left side of the embankment dam (from 0+000 km to 0+800 km) that identified as F1 to F4 (Table1). Plot of poles of planes of joints and four faults in hard rocks is given in Fig 2. , Table 1:Faults in the left side of the dam F1 F2 F3 F4 Dip 80 75 78 70 Dip Direction 230 230 225 30 Fig. 1: Geological section showing the geological How to Cite this Article: Houtan Jebelli, Melika sharifironizi, Vandad Mazarei and Esmail Aflaki, "Using Neural Networks for the prediction of Permeability in Rock for Derik Embankment Earth Dam" Science Journal of Civil Engineering and Architecture, Volume 2014, Article ID sjcea-165, 8 Pages, 2014. doi: 10.7237/sjcea/165 page 3 Science Journal of Civil Engineering and Architecture( ISSN:2276-6332) Fig. 2: Plot of poles of joints and faults in hard rock mass DESCRIPTION OF DATA Then, all the data were entered into an Excel application program for calculations before the analysis began. Lugeon tests were performed to obtain the Lugeon value, which gives the permeability of that specific borehole section. The tablelists the data analyzed for 51 boreholes. All of the data were collected from the inspection chart of the grout-curtain construction of the Derik dam in 2010. Table 2, 3 and 4 shows the number of boreholes in each zone of the Derik dam. The location of the boreholes and the Lugeon changes referring to depth in left zone and the main zone shown in Fig.3 and Fig.4. Table 2. Number of boreholes in left zone Zone Left Zone Bore hole number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Lu=2.5 1 2 0 2 0 0 0 0 1 2 1 3 4 3 3 1 2 3 0 Lu=12.5 1 1 2 2 1 1 4 5 3 2 1 3 1 0 3 2 2 3 0 Lu=35 Lu=75 0 1 1 1 2 1 0 1 0 1 3 0 0 0 0 0 1 2 0 1 0 1 0 1 2 1 1 1 0 1 0 0 1 1 2 5 2 2 Lu>100 1 0 1 0 1 1 1 0 1 1 0 0 0 2 0 2 3 1 2 Total number of Lugeon Test 4 4 5 5 5 5 6 7 6 6 6 6 5 6 7 7 13 11 4 How to Cite this Article: Houtan Jebelli, Melika sharifironizi, Vandad Mazarei and Esmail Aflaki, "Using Neural Networks for the prediction of Permeability in Rock for Derik Embankment Earth Dam" Science Journal of Civil Engineering and Architecture, Volume 2014, Article ID sjcea-165, 8 Pages, 2014. doi: 10.7237/sjcea/165 Science Journal of Civil Engineering and Architecture( ISSN:2276-6332) 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 4 3 3 4 6 4 5 5 3 2 7 3 4 5 2 4 3 2 4 6 4 5 0 3 5 1 1 1 1 7 Page 4 0 3 0 0 1 0 2 2 1 2 0 0 0 0 0 3 1 1 2 0 1 1 0 1 1 1 4 2 1 1 3 3 2 1 0 1 0 3 1 1 1 3 1 0 1 14 13 8 11 13 10 13 10 9 11 10 11 8 7 11 Table 3:Number of boreholes in main zone Zone Bore Hole Number Lu=2.5 Lu=12.5 Lu=35 Lu=75 Lu>100 Main Zone 1 2 3 4 5 6 7 8 9 10 11 12 13 14 2 1 0 4 4 5 3 3 3 2 3 3 6 4 3 1 1 5 1 0 0 0 2 4 4 2 1 5 0 0 2 0 0 0 0 0 0 1 1 2 2 0 3 2 1 0 0 0 0 0 0 1 1 1 1 2 2 2 0 0 0 0 0 0 0 0 0 1 1 2 Total Number of Lugeon tests 10 6 4 9 5 5 3 3 5 8 9 9 11 13 Table 4:Number of boreholes in right zone Zone Right Zone Bore Hole Number Lu=2.5 Lu=12.5 Lu=35 Lu=75 Lu>100 Total Number of Lugeon tests 1 8 1 1 2 2 14 2 3 2 0 0 0 5 3 2 4 1 1 0 8 How to Cite this Article: Houtan Jebelli, Melika sharifironizi, Vandad Mazarei and Esmail Aflaki, "Using Neural Networks for the prediction of Permeability in Rock for Derik Embankment Earth Dam" Science Journal of Civil Engineering and Architecture, Volume 2014, Article ID sjcea-165, 8 Pages, 2014. doi: 10.7237/sjcea/165 page 5 Science Journal of Civil Engineering and Architecture( ISSN:2276-6332) Fig. 3: Lugeon changes referring to depth in left zone Fig. 4: Lugeon changes referring to depth in main zone How to Cite this Article: Houtan Jebelli, Melika sharifironizi, Vandad Mazarei and Esmail Aflaki, "Using Neural Networks for the prediction of Permeability in Rock for Derik Embankment Earth Dam" Science Journal of Civil Engineering and Architecture, Volume 2014, Article ID sjcea-165, 8 Pages, 2014. doi: 10.7237/sjcea/165 Science Journal of Civil Engineering and Architecture( ISSN:2276-6332) NEURAL NETWORK APPROACH An artificial neural network is a parallel-distributed information processing system. It stores the samples with distributed coding, thus forming a trainable nonlinear system. Given the inputs and the desired output, it is also self-adapt to the environment so that responding to different inputs rationally (Jianget al., 2008). The aim is training the network to achieve a balance between the ability to respond correctly to the input patterns (Fausett, 1994). Page 6 A simple network has a feed-forward structure where signals flow of inputs through any hidden units and eventually reaches the output units (Figure 5). To train neural networks as a learning algorithm is used for specifying the initial set of weights and indicates how weights should be adapted to improve performance by minimizing errors. By sequentially applying a set of input while adjusting network weights, the network weights gradually converge to values that are able to produce desired sets of outputs (Tarassenko, 1998). Fig.5. The structure of a simple Neural Network DESIGN OF THE NEURAL NETWORKS In this study, NeuroSolutions version 6.0 was used for design purposes (NeuroDimentions, 2002). Two models were considered in order to design Neural Networks that predicting the final permeability of rock and the flow regime. In the first model, the values of absorption rate and water pressure data are the inputs. Therefore, the network needs 10 inputs (two Q and P in each five testing stages). In the second model, the network uses Lugeon values for calculation for each stage of the test as input, which means that the network requires five inputs. One Lugeon value calculated for each five tests and the Lugeon value for the test sections in the boreholes is the output of the test. Currently there is no way to estimate the number of hidden layers or hidden units, which is an optimal layer in these layers, other than by experiments. However, one layer in the network is capable to solve any problems (Goh, 1995 and Shi et al., 1998). The number of inputs and outputs of the neural networks is determined by considering the characteristics of the application (Saemiet al., 2007). In this study, one hidden layer used for designing the network for both models, but the number of hidden neurons changed to find the most appropriate network topology. The backpropagation learning algorithm was used in this study in order to train the neural networks (Rumelhart et al., 1986). This algorithm executes the patterns into steps. In the first step a forward flow of signals produce from the input layer to the output layer. Then from the difference between the calculated and desired output, the error of each output neuron was computed. In the second step, the weights in the hidden layers and output layer re-adjusted in order to reduce the difference between the exit output and the desired output (Rumelhart et al., 1986). The network performance may be evaluated quantitatively in terms of the coefficient of correlation (R2), mean summed square of errors (MSSE), and the error rate. The error rate was defined by (1), (2) and (3). (Yehet al., 2003) 1 2 3 Where T and O are targeted and network output values, respectively; Np is the number of input patterns; Nout is the How to Cite this Article: Houtan Jebelli, Melika sharifironizi, Vandad Mazarei and Esmail Aflaki, "Using Neural Networks for the prediction of Permeability in Rock for Derik Embankment Earth Dam" Science Journal of Civil Engineering and Architecture, Volume 2014, Article ID sjcea-165, 8 Pages, 2014. doi: 10.7237/sjcea/165 page 7 Science Journal of Civil Engineering and Architecture( ISSN:2276-6332) number of output neurons, for a network with one output neuron, as in this study. Result of the networks cross validation. Also the data were randomized after normalizing the data to prevent the network being influenced by similar or redundant data. The results of the neural networks presented in Table 1. Obtained data from 445 water pressure tests (Leugon) were considered in this study. 356 leugon's results were used for training the network, 44 sets for cross validation and 47 for testing the network. In order to omit the over fitting in the network and check the progress of the algorithm we used In order to analyze and compare the performances of the networks the mean absolute error (MAE) and the correlation coefficient (r) were used and to distinguish the performance of the network, the maximum value of r and the minimum value of MAE should be considered. Table 5: Results of different networks using Lugeon values as input Number of hidden neurons 20 15 10 7 5 3 Training r MAE 0.991 2.563 0.994 2.101 0.996 1.911 0.996 1.855 0.997 1.823 0.992 2.001 For this model, the network that contains five hidden neurons has the best results among other networks. Using 3 hidden neurons is very simple and also using too many hidden neurons is making the network complex and it causes the network longer in time so the network show lower performance. CONCLUSION There are some disadvantages during water pressure test which cause bad effects on the results. For example, using different pressures during the tests in the rock masses may result changes of the behavior of the rock masses. In addition, the relation between the absorption rate and the water pressure in jointed rocks is non-linear that it can make the interpretation of the flow type more difficult, but neural networks have the ability to recognize the relative importance of a particular parameter in a given pattern. By using neural networks, determination of the permeability of rock masses from lugeon values calculated for each testing stage become more capable. Neural networks could be a useful mean for predicting and analyzing the permeability of rock masses of foundations for dams and grouting zones. REFERENCES 1. Edison Gil.,2000.Improving the Simulation of a Water flooding Recovery Process Using Artificial Neural Networks, A thesis submitted to the college of Engineering and Mineral Resources at West Virginia University, USA. 2. Ewert, F.K. 1985. Rock Grouting with Emphasis on Dam Sites. Springer Verlag, Berlin 3. Fausett, L.V. 1994. 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