THE ASSESSMENT OF BURIED OBJECT ON GROUND PENETRATION RADAR, GPR WITH SPECIFIC DEPTHMuhamad Iqbar Bin Ahmad Maliki, Dr.Aziman Bin MadunJKIG,FKAAS, Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja,Batu Pahat, Johor.Corresponding E-mail : mr.iqbar@gmail.comAbstract

Ground penetration radar or known as GPR is a device that uses a technique of electromagnetic waves in detecting objects that are below the ground surface. This technology is also use geophysical method in which it allows the process of observing the ground subsurface profile without having to damage the soil structure and known as "non-destructive method". GPR works by using simple methods where, the electromagnetic waves through a transmitting antenna is reflected from objects that are embedded and then detected by other antennas called the receiving antenna. The research conducted will use two types of devices known as GPR (New) and GPR NOGGIN where the main focus of this study is to examine the effects GPR tool to size and material of buried objects with the specified depth and to compare the results of both type of GPR. The study will use two different research sites, where the use of GPR (New), study will be conducted in the laboratory while the use of GPR Noggin, study will be conducted at field in existing site. Through this research, the results that are able to be observed by the GPR by using the different type of material and size of the objects with specified depth will be analysed in the form of 2D hyperbolic using existing software, where, for the GPR (New), the analysis will be conducted using the software of MATLAB while for the GPR NOGGIN, the analysis will be done using REFLECT W software. Based on the results that have been analyzed, we can know the effect of both type of GPR in term of materials, sizes in the form of hyperbolic 2D. GPR can be considered as a simple technology that does not involve methods that destroying the soil structure.

Keywords: GPR, Electromagnetic Waves, Non-destructive method, Geophysical, Antenna, Hyperbolic 2D, Reflect W, MATLAB

1.0 Introduction

At present, there are various types of sophisticated technology which is able to bring the construction industry towards a better and easier. This technology was created and developed to find a solution in the course of any construction activity to a higher level in terms of cost savings, time and more economic. An example is ground penetration radar, known as GPR where this technology has been widely used around the world to this day, particularly in the fields of engineering, environmental and archaeological [1]. GPR is a device which has a high resolution of electromagnet specially created to detect underground objects or embedded objects such as detecting the location and size of the object [2], while widely used, particularly in the field of research involving issues such as detecting underground embedded objects such as water pipes, electricity cables, explosives and so on [3]. This technology also allows the use of geophysical methods to observe an underground profile without having to dig, and can save certain costs [1]. In engineering field, especially in civil engineering, GPR has been used for road pavement evaluation process, to detect voids as well as water level under the ground and many more [1]. Theoretically, GPR operates when the wave of electromagnetic emitted by the antenna reflected from the embedded object and then detected by the other antenna called receiver antenna Data and results obtained are illustrated in a graph of time against distance where it has much similarity with seismic reflection method where wave energy is converted to electromagnet seismic [1]. It can be said, GPR technology is compatible with the needs of society today, such as the researchers, civil engineers and others in helping them to do their jobs on any matter relating to the problem underground, such as detecting objects embedded, investigate the profile of the soil and so on. Hence, this technology allowing job that is done more effectively where it can save cost, time and energy.. 2.0 Literature Review

Table 2.1: Explanation of the influence of electric properties and frequency toward the GPR(Sorces Richard J. Yelf, 2007)The table above explains about the influence of the electric properties which is dielectric constant and conductivity as well as the influence of frequency towards the GPR.

Table 2.2: Permittivity values of sub surface of the type of soils.

(Sources: Jim Lester and Leonhard Bernold, (2006) Davis and Annan (1989) and Geophysical Survey Systems, Inc. (1987)

Table above shows the value of permittivity of every type of soils. This value will influence the results of GPR where the highest value of permittivity of the sub surface will cause the result in term of image in hyperbolic 2D form produced will become poor but the lower value will produce the more clear results.

3.0 Methodology

This study will be conducted at research centers in soft soil (RECESS) UTHM and the Establishment (RECESS) is to undertake research and development of technology engineering soft soil. It is difficult to detect buried objects under the ground without knowing the location and depth of the object. The situation of Underground is difficult to assess through soil surface [6]. Therefore the use of GPR is suitable since the GPR using the geophysical methods that are designed to investigate the matter under the earth's surface [7, 8]. The study was conducted using two types of GPR which are GPR (New) and GPR NOGGIN. The objectives are to make the comparison results between these two GPR and to assess the capability of these tools in observing the objects that are embedded underground. For the GPR (New), the experiment is only carried out in the laboratory where appropriate to their small size and the site for the experiments is only use a box filled with sand and the object will be separately buried at a depth of 10cm and 20cm. The process of data analysis will use the MATLAB software. For experiment of GPR NOGGIN, it will be carried out at RECESS UTHM area where ground will be excavated to a depth of 1 foot and the object will be buried. This is because the size of GPR NOGGIN is 630mm x 410mm x 230mm and use a frequency of 250GHz. This research uses two type of soil which is laterite soil and sand to see the comparison the results between the GPR (New) and GPR NOGGIN. The process analyzing the data will use the software of REFLECT W

4.0 Result and Discussion

GPR (New)

Figure 4.1: Scale for intensity of energy

Steel pipe for depth 10cm and 20cm

Figure 4.2: Results of hyperbolic 2D form for 10cm and 20cm of steel pipe

PVC pipe for depth of 10cm and 20cm Figure 4.3: Results of hyperbolic 2D form for 10cm and 20cm of PVC pipe

Poly pipe for depth of 10cm and 20cm

Figure 4.4: Results of hyperbolic 2D form for 10cm and 20cm of poly pipe

GPR NOGGIN

Three steel pipes with diameter of 30mm, 25mm and 20mm

Figure 4.5: Results of hyperbolic 2D for three steel pipes with diameter 30mm, 25mm and 20mm

Three PVC pipes with diameter 90mm, 45mm and 30mm

Figure 4.6: Results of hyperbolic 2D for three PVC pipes with diameter 90mm, 45mm and 30mm

Three Poly pipes with diameter of 30mm, 25mm and 20mm

Figure : 4.7 Results of hyperbolic 2D for three Poly pipes with diameter 30mm, 25mm and 20mm

GPR (New)

The intensity of energy of electromagnetic waves due to the depth

The figure 1.0 shows the scale level of wave energy where the more red the result, the stronger the resulting of wave reflection. Based on the results as stated, the waves are very strong at a depth of 10cm compared to 20cm depth. The results of this can be seen as it has been shown, when the object with type of steel buried at a depth of 10cm, there is a red color which mean the intensity of energy is at the highest scale and scale of the intensity of energy is reduced at a depth of 20cm, followed by the object of other materials. It can be said that, the intensity of energy of the electromagnetic wave reflected by the wave is very strong because as we know, the steel has a very good level of reflection. For other objects, the energy intensity of electromagnetic wave is declining but still perpendicular to the theory where, the deeper, the less intensity of energy of the wave. The level of energy strength would be significantly reduced if the depth increases. For depth at 10cm, wave energy level is still strong compared to the depth of 20cm. So, the hypothesis can be stated here is, the more the objects are buried, the less the level of energy intensity of the waves that can be generated

Image of hyperbola 2D based on the materials and size.

According to the results of GPR (New) obtained, the analysis showed unsatisfactory results where the level of the resulting image is poor. By comparing the results, show that it was still the right decision based on theory of electromagnetic waves where, steel objects still show the images of hyperbolic 2D more clear than objects of Poly and PVC pipe. This is because iron has a good level of reflection. Other objects also provide image of 2D hyperbolic but is not so obvious when compared to the objects of iron. Based on the results obtained, object show better results of 2D hyperbolic image at a depth of 10cm compared to 20cm. This is because, the level of frequency used is limited to shallow depths because the antennas are designed was not yet stabled and strong. However, the results obtained are still not satisfactory as it can be seen, the image produced is poor and this would complicate the process for determining the depth of the object and the type and size of the object. The size of the curves of the result will depend on the diameter of the objet. However, from the results, we can see that the curve show almost the same even the used of the diameter of pipe is different this is due to the system developed is still no stable yet.

GPR NOGGIN

Based on the study that has been done, and through the analysis of the data found that, the properties of the object will definitely affect the GPR it results. The properties of the objects are in term of type of materials, and size of the object. Based on the analyzed results, the object form steel has shown the clearest image in hyperbolic 2D compared to others object. We can see from the result, the PVC pipe shown the better image than poly. This is because, the GPR NOGGIN using the electromagnetic wave to detect the object underground. When this technology used, the antenna of the GPR will emitted the waves of electromagnetic and then reflected back through the receiver antenna and form the hyperbolic image. Hence, steel will show the better image due to his properties that has good reflection properties compared to others materials. We can said here, the better the reflection properties of the object, the better the result will produced and the object will more easier to detect as well as know the size and type of the object. The curve of the hyperbolic will not influenced if it is only in the range of 2 until three inch. That is why, the curve of the result look almost the same since the biggest diameter of the object is only 90mm which is less than 3 inch. The curve also depend on the size of the object buried and the bigger the size will cause the curve formed look wide but the clear of the image is still depend on the materials of the object.

5.0 Conclusion

As a conclusion, the result of both GPR showed that the steel pipe has the clearest image of hyperbolic 2D followed by PVC pipe and lastly was Poly pipe. It shows that, the materials of the buried objects will affect the results of the GPR. The GPR technology was definitely can solve the problem in term of to determine the depth of the buried object and also to assess the object underground in term of size, materials and many more. This technology was able to help human to facilitate them as well as can save time, energy and cost of maintenance. As for the GPR (New), this technology has showed the positive results but alteration in term of technology developed and used in this GPR need to be improved so that it can compete with the GPR NOGGIN. We can say that, the objectives in this researched were achieved.

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