PHYSICAL PARAMETER EFFECTS ON 3D NUMERICAL MODELING OF GROUND PENETRATING RADAR (GPR): DNAPL CASE STUDY

Öz

In this study, the effect of the physical parameters directly affecting the performance of the ground radar (GPR) method on the field was investigated by using a three-dimensional numerical model. While the medium was designed as saturated sand, the properties of dense non-aqueous phase liquids (DNAPL) were used as buried mass. Trichloroethylene (TCE), Tetrachlorethylene (PCE), Trichloroethane, and Dichloroethane were selected as DNAPL types. 1.5GHz center frequency GSSI brand GPR antenna was used as a source. In the first stage, while the physical parameters of the medium were gradually increased, the physical parameters of the DNAPL mass were kept constant. In the second stage, the opposite process was applied. When the radargrams were examined, it was observed that the reflections of the DNAPL mass were delayed due to the increase of the relative dielectric permittivity of the medium. In addition, TCE was the most detectable DNAPL type that causes the most obvious reflections. When the electrical conductivity value was increased gradually, electromagnetic energy was absorbed and recorded as weak reflections. It was observed that the gradual increase of the relative magnetic permeability value caused strong multiple reflections.

Anahtar Kelimeler

• Ground penetrating radar
• Numerical modeling
• DNAPL
• gprMax

YER RADARI (GPR) İÇİN 3B SAYISAL MODELLEMEDE FİZİKSEL PARAMETRE ETKİLERİ: DNAPL ÖRNEĞİ

Öz

Bu çalışmada yer radarı yöntemi için sayısal modelleme benzetimleri yapılmıştır. Bu amaçla 3B sayısal model seti tasarlanmıştır. Model seti içerisinde ortama ve gömülü nesneye ait fiziksel parametre değerleri değiştirilerek radargramlara etkisi incelenmiştir. İncelenen bu parametreler göreceli dielektriksel geçirgenlik, elektriksel iletkenlik ve göreceli manyetik geçirgenlik değerleridir. Aranan gömülü nesne olarak ise yeraltı su sistemleri için büyük tehlike arz eden Dense non-aqueous phase liquids (DNAPL) olarak adlandırılan kirleticilere ait özellikler kullanılmıştır. Modellemelerde kullanılan DNAPL türleri; Trikloroetilen (TCE), Tetrakloroetilen (PCE), Trikloroetan ve Dikloroetan seçilmiştir. Sayısal modellemelerde kaynak olarak GSSI firmasına ait 1.5GHz anten frekansına sahip anten modeli kullanılmıştır. Elde edilen sentetik radargramlar hem izler hem de profiller üzerinden karşılaştırılmıştır. Tüm bu sonuçlar irdelendiğinde fiziksel parametrelerin yer radarı yöntemi üzerindeki etkisi ayrıntılı bir şekilde ortaya konmuştur.

Anahtar Kelimeler

• Yer radarı
• sayısal modelleme
• DNAPL
• gprMax

Kaynakça

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