Analisis Daya Dukung Loading Test Tiang Pancang Tunggal Diameter 600 Mili Meter pada Proyek PLTU Pangkalan Susu dan Pemodelannya

Abstract

Supporting capacity and foundation settlement are the main criteria in planning and constructing foundation because they have an important role in carrying the distribution of structural load and other loads to hard soil layer under the ground. Loading test is one of the means in determining supporting capacity and pile foundation settlement. The objective of the research was to obtain the quantity value of axial supporting capacity of single pile foundation, using the result of Sondir data, Standard Penetration Test (SPT), Kalendering and Loading test in the field. Finite Element Method with Mohr Coulomb soil model, using Plaxis program, were used in order to compare them. The whole result of the analysis was then compared with loading test which had been conducted in the field. The result of the calculation of ultimate supporting capacity of the piles (Qu) was based on Davisson method, Chin Kondner method, and Mazurkiewicz method of 345 tons, 556 tons, and 400 tons consecutively. The result of calculation of the settlement of the element modeling, followed by the use of Plaxis program media showed that the settlement of pile foundation was 16.97 mm, while the result of loading test conducted in the field showed the settlement was 16.15 mm. In ASTM D1143/81, it was found that the permitted settlement was 1 inch = 25.4 mm which indicated that vertical load test met the requirements of ASTM D1143/81. The result of the analysis on foundation supporting capacity, using some methods, showed that there were varied supporting capacities. The calculation of ultimate supporting capacity of the piles was based on Davisson method because it could give the quality value which was smaller than the calculation of ultimate supporting capacity of the piles, using other methods. There was significant difference of the settlement of bored pile foundation between Plaxis modeling and the result of loading test.

Daya dukung dan penurunan pondasi merupakan kriteria utama didalam perencanaan dan pembangunan pondasi karena memiliki peranan penting dalam memikul penyaluran beban struktur dan beban lainnya ke lapisan tanah keras yang terletak di dalam tanah. Pengujian loading test adalah salah satu sarana didalam penentuan daya dukung dan penurunan pondasi tiang. Tesis ini bertujuan untuk memperoleh nilai besaran daya dukung aksial pondasi tiang pancang tunggal, menggunakan hasil data Sondir, Standard Penetration Test (SPT), Kalendering dan Loading Test di lapangan. Membandingkannya menggunakan metode elemen hingga (Finite Element Method) dengan model tanah Mohr Coulomb menggunakan program Plaxis. Hasil keseluruhan analisis ini dibandingkan dengan hasil uji pembebanan (Loading Test) yang telah dilakukan di lapangan. Hasil perhitungan kapasitas daya dukung ultimit tiang pancang (Qu) berdasarkan dengan metode Davisson, metode Chin Kondner dan metode Mazurkiewicz secara berurutan yaitu 345 ton, 556 ton, dan 400 ton. Untuk perhitungan nilai penurunan (settlement) dari hasil pemodelan elemen hingga menggunakan media program Plaxis diperoleh nilai penurunan (settlement) pondasi tiang pancang sebesar 16,97 mm, sedangkan hasil pengujian Loading Test yang dilakukan di lapangan diperoleh nilai penurunan (settlement) sebesar 16,15 mm. Dalam ASTM D1143/81 untuk penurunan yang diijinkan adalah sebesar 1 inchi = 25,4 mm, hal ini mempertegaskan bahwa uji pembebanan vertikal yang dilakukan memenuhi persyaratan ASTM D1143/81. Dari hasil analisis daya dukung pondasi dengan menggunakan beberapa metode, diperoleh hasil daya dukung yang bervariasi. Perhitungan nilai kapasitas daya dukung ultimit tiang pancang berdasarkan metode Davisson yang diambil, karena memberikan nilai besaran yang lebih kecil dari perhitungan nilai kapasitas daya dukung ultimit tiang pancang dengan metode lainnya. Selisih nilai penurunan (settlement) pondasi tiang pancang antara hasil pemodelan Plaxis dan hasil pengujian Loading Test tidak terdapat perbedaan yang jauh.