Analisis Geostatistik dalam Menentukan Keseragaman Nilai Kepadatan Tanah Dasar
DOI:
https://doi.org/10.5614/jts.2018.25.3.4Keywords:
kepadatan tanah dasar, variabilitas spasial, geostatistik, krigingAbstract
Abstrak
Prediksi nilai kepadatan tanah dasar dalam pekerjaan jalan biasanya dilakukan dengan pendekatan non-spasial sampling. Metode prediksi spasial dengan pendekatan geostatistika yang diterapkan bertujuan untuk memprediksi dan memetakan nilai kepadatan. Metode yang digunakan adalah metode kriging berdasarkan model semivariogram. Hasil prediksi diuji melalui validasi dengan menggunakan data nilai kepadatan kering hasil pengukuran sandcone. Hasil analisis menunjukkan bahwa nilai kepadatan memiliki korelasi spasial dengan keragaman yang dipengaruhi jarak dan tipe sebaran, serta arah sebaran data kepadatan tanah dasar. Model semivariogram dipengaruhi oleh nilai range dan sill. Nilai range pada data lapangan zona 1 (mean γD =1,1845 gr/ cm 3 ) sebesar 135,667 meter sedangkan zona 2 (mean γD =1,332 gr/cm3 ) sebesar 319,80 meter. Sehingga dapat dikatakan bahwa besarnya nilai γD akan mempengaruhi jarak pengambilan sampel. Keseragaman hasil pemadatan pada bagian jalan dapat dievaluasi dengan menggunakan pendekatan geostatistik. Nilai mean dari data kepadatan dan nilai standar deviasi menentukan tingkat keseragaman hasil pemadatan tanah dasar. Standar deviasi 0,003 memberikan nilai RMS error sebesar 0,0025 sedangkan jika standar deviasi 0,005 nilai RMS error menjadi 0,005.
Abstract
Prediction of the value of subgrade density in road works is usually done with a non-spatial sampling approach. The spatial prediction method with the applied geostatistical approach aims to predict and map density values. The method used is the kriging method based on the semivariogram model. Prediction results were tested through validation by using dry density value data from the measurement results of sandcone. The results of the analysis show that the density value has a spatial correlation with diversity influenced by distance and type of distribution, as well as the direction of distribution of subgrade density data. The semivariogram model is influenced by range and sill values. The range value in zone 1 field data (mean γD =1,1845 gr/cm3 ) is 135,667 meters while zona 2 (mean γD =1,332 gr/cm3 ) is 319,80 meters. So that it can be said that the magnitude of the value of γD will affect the sampling distance. Uniformity of the results of compaction on parts of the road can be evaluated using a geostatistical approach. The mean value of the density data and the standard deviation value determine the level of uniformity of subgrade compaction results. The standard deviation of 0,003 gives the value of the RMS error of 0,0025 while if the standard deviation of 0,005 the value of the RMS error becomes 0,005.
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