Degradasi Harga CBR-Rendaman Lapisan Pondasi Dan Tanah Subgrade Di Bawah Perkerasan Jalan Akibat Adanya Kombinasi Genangan Air Yang Terus Menerus Dan Repetisi Beban Kendaraan Berat

Nurtjahjaningtyas, Indra (2020) Degradasi Harga CBR-Rendaman Lapisan Pondasi Dan Tanah Subgrade Di Bawah Perkerasan Jalan Akibat Adanya Kombinasi Genangan Air Yang Terus Menerus Dan Repetisi Beban Kendaraan Berat. Doctoral thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Dalam perencanaan perkerasan jalan raya, tanah subgrade dan lapisan pondasi perkerasan jalan didesain dengan menggunakan hargaCBR yang terkecil, yaitu CBR- rendaman (soaked CBR), akan tetapi pada kenyataanya masih saja terjadi kerusakan-dini pada perkerasan jalan di Indonesia. Kerusakan-dini tersebut diduga karena telah terjadi degradasi harga CBR tersebu menjadi lebih kecil dari pada harga soaked-CBR semula, sebagai akibat dari genangan air (hujan) yang terjebak di bawah perkerasan dan kendaraan berat yang lewat berulang-ulang. Dugaan tersebut berdasarkan kenyataan bahwa hampir semua kerusakan-dini pada jalanraya di Indonesia terjadi terutama pada musim hujan, dan juga hampir semua ruas jalan yang mengalami kerusakan-diniadalah yang dilewati oleh kendaraan berat. Jadi, kombinasi dari air (hujan) yang menggenang dibawah perkerasan dan kendaraan berat dengan muatan berlebihan (overloaded) yang lewat berulang-ulang dicurigai dapat menyebabkan kerusakan-dini pada jalan; sehingga perlu diketahui bagaimana dua faktor tersebut dapat menyebabkan kerusakan-dini pada jalan-jalan raya di Indonesia. Pada penelitian ini, sebagai material dasar penelitian dipilih dua jenis tanah subgrade, yaitu tanah urugan biasa (UB) dan tanah urugan pilihan (UP), dan dua jenis agregat untuk lapis pondasi perkerasan jalan, lapis perkerasan atas (LPA) dan lapis perkerasan bawah (LPB), yang semua material itu berdasarkan standard Bina Marga. Selain itu juga disiapkan geotextile sebagai bahan perkuatan, karena dari pengalaman di lapangan diketahui bahwa adanya perkuatan geotextile di bawah perkerasan dapat membuat perkerasan bertambah kuat dan awet. Ada minimal 48 buah benda uji yang diteliti, yang terdiri benda uji tanpa perkuatan geotextile dan benda uji dengan perkuatan 1 lapis geotextile. Proses pengujian CBR berdasarkan Standrad AASHTO untuk soaked-CBR, dandilakukan sebelum dan sesudah dilakukan pembebanan siklik pada setiap benda ujinya. Pembebanan siklik dilakukan dengan variasi tekanan p=50 psi (mewakili beban roda kendaraan ringan), p=100 psi (mewakili beban roda kendaraan berat bermuatan normal) dan p=150 psi (mewakili beban roda kendaraan berat bermuatan berlebihan). Test CBR dilakukan di setiap akhir pembebanan siklik pada jumlah repetisi n=0, 10, 50, 100 dan 300 untuk material urugan biasa (UB); dan repetisi n=0, 300, 600, 900, 1200, 1500 untuk material urugan pilihan (UP), untuk lapis pondasi-bawah (LPB) dan untuk lapis pondasi-atas (LPA). ======================================================================================================= In the design of pavement, the subgrade soil and the sub-base and base courses are already designed with the least CBR value, which is the soaked-CBR value; however, the reality tells us that premature pavement deterioration keeps prevailing in Indonesia. The premature deterioration is suspected due to the decrease of the soaked-CBR value in field, because of the combination of the existence of trapped water (rainwater) under the pavement and the repetition of heavy truck passing on the pavement. This suspicion is based on the condition that almost all pavement premature damages occur during the rainy season, and almost all of the roads undergoing premature deterioration are of those traversed by heavy truck traffic. Therefore, the combination of water trapped under the pavement and the heavily overloaded truck traffic are suspected to be the main causes of pavement premature deterioration, so that research is needed to explain how the two factors above will cause premature pavement deterioration in Indonesia. In this study, the materials used were two types of subgrade soils, which were the common fill (UB = uruganbiasa) and selected fill (UP = uruganpilihan) material, and two types of pavement foundation materials, which were the subbase course (LPB = lapis pondasibawah) and base course layers (LPA = lapis pondasiatas), all were in accordance with the Bina Marga standard of Indonesia. Furthermore, one layer of geotextile reinforcement was also applied since geotextile had been known to cause pavement to become stronger and more durable. There were at least 48 samples used in this study, comprising of samples without and samples with 1 layer of geotextile reinforcement. The CBR test procedures were following the AASHTO test standard for soaked-CBR, and the CBR tests were performed on every sample before and after every repetition of cyclic loading through the CBR piston with varied loading pressures of p = 50 psi (representing light vehicle tire load), p = 100 psi (representing the tire load of heavy truck with normal loading), and p = 150 psi (representing the tire load of heavily overloaded trucks). The CBR tests were conducted at the end of every load cycle repetition n= 0, 10, 50, 100 and 300 for common fill (UB = uruganbiasa) materials; and at the end of every load cycle repetitions n = 0, 300, 600, 900, 1200, and 1500 for the selected fill (UP = uruganpilihan) materials and the two types of pavement foundation layers (LPA and LPB). The results of this research can be summarized as in the following: 1. For samples that were kept in submersion (submerged samples) without geotextile reinforcement, drastic degradation of the soaked-CBR values were prevalent, especially on the LPB materials. 2. For the unsubmerged samples without geotextile reinforcement, the degradation of soaked-CBR values were less prevalent. 3. Repetitions of the light vehicle (p = 50 psi) tended to cause almost no reduction of the soaked-CBR values, for both submerged or unsubmerged conditions, and only heavy vehicles might cause degradation of the CBR values of the layers, especially for those of submerged samples and more apparent from the heaviest truck tire load (p = 150 psi). 4. The selected material (UP) and LPB layer material when submerged, but when reinforced with geotextile, would show much less degradation of the CBR values than those of the same materials without geotextile reinforcement, especially when the reinforcement was placed directly under the layer. 5. For the selected material (UP) and LPB layer when unsubmerged (representing good drainage system under the pavement), but reinforced with geotextile, there was hardly any change in the CBR values. 6. To prevent the degradation of the soaked-CBR values of the soil and foundation layers under pavement, the pavement should have a good drainage system and one layer of geotextile reinforcement should be added under the sub-base (LPB) layer. It is also suggested that a layer of selected material (UP = uruganpilihan) of at least 60- cm thickness should exist at the top of the road embankment layers. All the study here has successfully show that the presence of rainwater submersion under the pavement and the repetitions of heavy vehicle loads, especially of those of the heavily overloaded ones, are the main factors in causing premature deteriorations of the pavement in Indonesia.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: premature deterioration of pavement, degradation of CBR values, repetition of heavy vehicle load, impact of rain water on pavement, kerusakan-dini perkerasan jalan, degradasi harga CBR, repetisi beban kendaraan berat, dampak air hujan pada perkerasan jalan
Subjects: T Technology > TA Engineering (General). Civil engineering (General) > TA441 Aggregates
Divisions: Faculty of Civil, Planning, and Geo Engineering (CIVPLAN) > Civil Engineering > 22001-(S3) PhD Thesis
Depositing User: Nurtjahjaningtyas Indra
Date Deposited: 16 Dec 2020 07:21
Last Modified: 16 Dec 2020 07:21
URI: https://repository.its.ac.id/id/eprint/82324

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