A Computer Aided Learning Package for Teaching Geotechnical ...

A Computer Aided Learning Package for Teaching Geotechnical Engineering Basuony El-Garhy Professor of Geotechnical Engineering and Foundations Civil Engineering Department, University of Tabuk, KSA e-mail: [email protected]

Tarek Ragab Assistant Professor of Structural Engineering Civil Engineering Department, University of Tabuk, KSA Civil Engineering Department, University of Alexandria, Egypt e-mail:[email protected]

Fahmy Asal Assistant Professor of Surveying Engineering Civil Engineering Department, University of Tabuk, KSA e-mail: [email protected]

ABSTRACT A Computer aided learning package has been developed as a support aid for students learning some principles of geotechnical engineering. The package called CALP_GE_I (Computer Aided Learning Package for Geotechnical Engineering I course) has been evolved over a period of one year as a result of research into student learning. This paper discusses the development and use of the CALP_GE_I. The package has been designed in such a way that users are made to work interactively with the programs, and are often required to provide numerical input or select from multiple choice questions. In this way, the users are involved in the solution process, thereby ensuring that the concepts are reinforced. Each of the programs is briefly described, and a tutorial is provided which guides the user through each program. CALP_GE_I is shown to be an effective learning tool in addition to the conventional methods of learning.

KEYWORDS:

Computer aided learning; geotechnical engineering; undergraduates

teaching.

INTRODUCTION The use of technology in civil engineering design has increased significantly in recent years. This has led to an increased need for graduating engineers that have been able to apply this technology while still in the classroom. Computer Aided Learning, CAL, has been shown to provide a useful facility for enhancing learning. CAL has provided important and useful additional learning resources to those traditional methods of instruction such as lectures, tutorials, text books, practical sessions and videos (Jaksa and Kuo 2009). A number of researches discussed - 1437 -

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the advantages and limitations of the CAL (Jaksa et al. 2000; Yuen et.al. 2005; Budge 2006; Ebner and Wolder 2007). Reviewing the literature pertaining to CAL revealed that geotechnical engineering among the early developments of CAL were GeotechniCAL package of programs (Davison, 1996), CATIGE (Jaksa et al., 1996), Geotechnical Courseware (Budhu, 2006), and the Delft Software and Resources (Verruijt, 2006). Several geo-engineering software companies have provided student versions of their programs (e.g., Geo-slope Int., 2009; Oasys, 2009; Soil Vision Systems, 2009). Each of these software packages contains several powerful geotechnical analysis and design programs, which have been scaled down for student use. These programs developed primarily to facilitate analysis and design and not necessarily to assist students in learning, are however extremely valuable tools for use in geotechnical engineering education (Jaksa and Kuo 2009). Recently Chegenizadeh and Nikraz (2012) presented the various CAL resources currently available in geotechnical engineering. An excellent internet site, which lists an extensive source of links to geotechnical engineering software, is provided by the Geotechnical and Geoenvironmental Software Directory (www.ggsd.com) which also provides a list of educational links. The development and use of the CAL package, CALP_GE_I, is the main focus of this paper. Here, CALP_GE_I is viewed as an aid to the learning process and used to supplement the traditional lecture course. It should not however be seen as a replacement for traditional teaching methods.

FRAMEWORK OF CALP_GE_I The framework of the developed package CALP_GE_I is shown in Figure 1. The CALP_GE_I contains main six modules, these are: (1) self assessment exercises, (2) stresses in a soil mass, (3) soil classification, (4) soil testing using excel, (5) course material, and (6) help.

Figure 1: Framework of CAL package CALP_GE_I

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Self Assessment Exercises Module Figure 2 shows the main window of self assessment exercises module. The module presents seven exercises (i.e., seven VB programs) which cover different topics in geotechnical engineering. These exercises include: Exercise 1 covers the types of rocks and weathering processes topic, Exercise 2 covers soil properties topic, Exercise 3 covers the index properties of soil topic, Exercise 4 covers the soil classification topic, Exercise 5 covers the soil compaction topic, Exercise 6 covers the soil permeability, and Exercise 7 covers stresses in a soil mass topic.

Figure 2: The main window of self assessment exercises module Each exercise consists of a number of multiple choice questions covering the concepts of the topic. Using these exercises will help students to improve their understanding for the concepts of the topic and to make self assessment. As an example exercise 1 consists of ten multiple choice questions covering the concepts of the topic (i.e., types of rocks and weathering processes). Exercise 1 include 5 pages (i.e., windows), each window contains three questions. For each question, the student will select the answer and the program will inform the student if this answer is correct or wrong. Figure 3 shows the window of page 1 from exercise 1 (i.e., questions 1, 2 and 3).

Stresses in a Soil Mass Module The module of stresses in a soil mass consists of six VB programs to calculate the stresses in a soil mass due to different types of load and stress isobar. The main window of the stresses in a soil mass module contains two buttons named "Stress Distribution" and "Isobar". Under the first button, there are five VB programs to calculate stresses in a soil mass due to different types of load (i.e., point load, line load, strip load, uniformly distributed load over rectangular area, uniformly distributed load over circular area) as shown in Figure 4 and under the second button there is a VB program to calculate the stress isobar due to point load as shown in Figure 5.

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Figure 3: Sample of questions from exercise 1 Only, calculation of the stresses in a soil mass due to point load using the program will be presented here as an example. The program is able to calculate the vertical stresses at any point inside the soil mass by using Boussinesq equation or Westergaard equation (Das 2010). As shown in Figure 4, the user is asked to enter the value of the point load (P), the coordinates (z, r) of the points at which the vertical stresses is calculated and select Boussinesq or Westergaard equation. The program is able to calculate the vertical stresses for eight points inside the soil mass as shown in Figure 4. The program can be also used to calculate the distribution of vertical stress with depth along vertical plane parallel to z-axis by entering constant value for r-coordinate and entering different values for z-coordinate. Using the same way, the program can be used to calculate the distribution of vertical stress along horizontal plane parallel to the ground surface by entering constant value for z-coordinate and entering different values for r-coordinate. The program can be used by students to understand the effect of different parameters on the value of the vertical stress inside the soil mass. An isobar is a line which connects all points of equal stress below the ground surface. In other words, an isobar is a stress contour. We may draw any number of isobars as shown in Figure 5 for any given load system. Each isobar represents a fraction of the load applied at the surface. Since these isobars form closed figures and resemble the form of a bulb, they are also termed bulb of pressure or simply the pressure bulb. Normally isobars are drawn for vertical, horizontal and shear stresses. The one that is most important in the calculation of settlements of footings is the vertical stress isobar. The program of stress isobar due to point load is able to calculate the coordinated (z, x) of points of equal stress using Boussinesq equation as described by Das (2010).

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As shown in Figure 5, the user is asked to enter the value of the point load (Q) and the value of stress isobar. The program will calculate the values of coordinates (z, x) for five points of that stress isobar. The values of coordinates (z, x) can be used to draw the stress isobar using excel.

Figure 4: Window of program stresses in a soil mass due to point load

Figure 5: Window of program stress isobar due to point load

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Soil Classification Module The soil classification module is a VB program aimed to classify the soils according to the Unified Soil Classification System (USCS) as described by Bowles (2001). The soil classification program will help students to understand the concepts of the soil classification using USCS. Also, the effect of different soil parameters on the classification of the soil can be investigated by the program. The program consists of a number of windows. In each window the user will be asked to input some soil classification parameters and based on the values of these parameters the program will open the next window and so on till classifying the soil and assigning symbol. The program will be explained through the following two examples. The other tracks of the program will not be presented here for space limitations

Example 1: Classification of Coarse Grained Soil For a given soil, the following are known: percentage passing No. 200 sieve = 30, percentage passing No. 4 sieve = 70, liquid limit, LL, = 33, plastic limit, PL, = 12. The soil classification program can be used to classify this soil as follows. In the first window the user asked to input the percentage passing No. 200 sieve as shown in Figure 6.

Figure 6: The first window for classification of the soil of example 1 Press next to go to the second window based on the value of the percentage passing No. 200 sieve. In the second window, the user is asked to input the values of the percentage passing No. 4 sieve as shown in Figure 7. Press next to open the third window. In the third window, the user is asked to input the plasticity index, PI = LL-PL, and liquid limit, LL, as shown in Figure 8. Press classify button to classify the soil. The group symbol is SC and the group name is clayey sands or sand-clay mixtures as shown in Figure 8.

Example 2: Classification of Fine Grained Soil For a given soil, the following are known: percentage passing No. 200 sieve = 70, liquid limit = 55 and Plastic limit = 20. This soil can be classified by the soil classification module as follows. In the first window the user asked to input the percentage passing No. 200 sieve as shown in Figure 9.

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Figure 7: The second window for classification of the soil of example 1

Figure 8: The third window for classification of the soil of example 1

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Figure 9: The first window for classification of the soil of example 2 Press next to go to the second window based on the value of the percentage passing No. 200 sieve. In the second window (Figure 10), the user is asked to input the values of plasticity index, PI = LL-PL, and liquid limit. Press classify button to classify the soil using plasticity chart. The soil is classified as CH-OH and the symbol name is Clay of high plasticity.

Figure 10: The second window for classification of the soil of example 2

Soil Testing Using Excel Module The module of soil testing using excel consists of four excel sheets that can be used to analyze and interpret the results of four Geotechnical Engineering laboratory tests. Figure 11 shows the main window of this module along with the laboratory tests. As an example, only the sheet of liquid limit test will be presented here for space limitation. After pressing the button

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named "Sheet 1", the liquid limit excel sheet will open as shown in Figure 12. The user has to input the collected laboratory data from liquid limit test into the Excel sheet as shown in Figure 12. The program can be also used to draw an x-y scatter graph between number of blows, N, on x-axis (logarithmic scale) and water content on y-axis as shown in Figure 13

Figure 11: Main window of soils testing using excel module

Figure 12: Liquid limit test excel sheet The program calculates the LL by two methods: the first method is the approximate method of the U.S Army Waterways Experiment station (i.e., LL = 21.3 as shown in Figure 12). In the second method, the liquid limit can be determined from the liquid limit chart shown in Figure 13. From Figure 13 at 25 blows yields a liquid limit of 19.5, which is probably more accurate than the approximate method.

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Figure 13: Liquid limit chart

Course Material Module Course material module contains twelve lectures cover the following geotechnical engineering topics: (1) what is geotechnical engineering i course?, (2) introduction to geotechnical engineering, (3) types of rocks, (4) weathering process, (5) origin and formation of soil, (6) definitions and weight-volume relationships, (7) index properties of soils, (8) soil classification, (9) soil compaction, (10) permeability, (11) total and effective stresses and (12) stresses in soil. The lectures prepared first as PowerPoint presentations and converted to PDF format. The main window of the course material module is shown in Figure 14. To open the lectures from the program you have to keep the CD of the package in the disk drive.

Figure 14: Main window of course material module

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CONCLUSIONS This paper presents a CAL package called CALP_GE_I. The package consists of a number of computer programs and self assessment exercises specifically written to assist with teaching some principles of geotechnical engineering to university students at undergraduate level. The package has been designed to be user interactive, and is often required to provide numerical input or select from multiple choice questions. In this way, the users are involved in the solution process, thereby ensuring that the concepts are reinforced. CALP_GE_I is easy to use, user friendly, user interactive and therefore is shown to be a useful facility to enhance students’ understanding the concepts of Geotechnical Engineering. We recommend the package to be integrated into the curriculum at University of Tabuk.

ACKNOWLEDGEMENTS The authors gratefully appreciated the support of the University of Tabuk under Grant No. S1433-0009.

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10. Jaksa, M. B., Kaggwa, W. S. & Gamble, S. K. (1996) "CATIGE for windowsteaching basic concepts of geomechanics by computer," In M.B. Jaksa, W.S. Kaggwa & D.A. Cameron (Eds.), Proc. of the 7th Australia New Zealand Conf. on Geomechanics Adelaide, Australia, 976–980. 11. Jaksa, M. and Kuo, Y. L., (2009) "Java applets in Geotechnical Engineering," AAEE, 20th Australasian Association for Engineering Education Conf., University of Adelaide, 249-254. 12. Oasys (2009) "Geotechnical software," software.com/products/geotechnical/.

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13. Soil Vision Systems (2009) "Next generation geotechnical software," Accessed at http://www.soilvision.com. 14. Verruijt, A. (2006) "Geotechnical software by Arnold Verruijt," Accessed at http://geo.verruijt.net/. 15. Yuen, S. T. S., Naidu, S., Kodikara, (2005) "Collaborative Development of Multimedia Courseware in Geotechnical Engineering Education," Proc. of the 2005 ASEE/AaeE4th Global Colloquium on Engineering Education, Australian Association for Engineering Education. 16. www.ggsd.com, Geotechnical and Geoenvironmental Software Directory

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