Kamis, 20 Agustus 2009

Teknik rakit bambu (bamboo raft) membantu memangkas biaya proyek


pohon bambu tumbuh subur dipelosok daratan asia timur, tenggara hingga selatan. Bambu banyak digunakan untuk keperluan rumah-tangga, dekorasi, perlengkapan makanan, perhiasan, kesenian, musik, alat-keamanan, perancah bangunan, alat transportasi dan lain-lain.
Dalam dua dasawarsa terakhir ini, fungsi bambu dikembangkan dalam bidang civil-engineering untuk memangkas biaya proyek. Proyek Pantai-Mutiara di Jakarta utara adalah proyek reklamasi pantai dengan cara menimbun pantai pada kedalaman dasar laut -2.0m hingga -4.0m dengan pasir dan tanah-merah hingga setebal rata-rata 8m.
Untuk mencegah timbunan tanah dari gerusan terjangan ombak, diperlukan struktur pelindung yang dinamakan breakwater atau seawall.Struktur seawall terdiri timbunan rubble mound ditutup armor beton (tetrapod), melindungi timbunan tanah sepanjang property-line. Karena dasar laut pantai-utara Jakarta terdiri lumpur lunak setebal rata-rata 18m, berat seawall yang diperkirakan sebesar 500 ton akan segera tenggelam kedalam lumpur tersebut.Banyak alternatif ditemui untuk mengatasinya, misalnya dengan replacement-soil, sand-column, stone-column, dynamic-compaction, geo-textile dan lain-lain.
Professor Dr.Ir.A.R.Soehoed, consultant-engineering dari PT.Puri-Fadjar-Mandiri-Indonesia, menemukan inovasi murah, alami namun aman, untuk mengatasi masalah settlement dan sliding tersebut.Settlement dari 45m seawall diatasi dengan bamboo-cluster; tujuh bambu diikat menjadi satu menjepit vertical-drain, kemudian dipancang dengan spasi 1.5m dibawah seluruh badan seawall. Diatas bamboo-cluster diletakkan bamboo-raft; terdiri tujuh lapis, masing-masing lapis terdiri 60 bamboo, diikat dengan tali ijuk (tali pengikat bamboo)menjadi satu untuk menahan sliding.Umumnya settlement diatasi dengan memancang sand-column atau stone-column, dan sliding diatasi dengan geo-textile. Namun dari inovasi bamboo-cluster dan bamboo-raft, Proyek Reklamasi Pantai-Mutiara mampu berusia 15 tahun hingga sekarang. Inovasi inipun akan digunakan untuk proyek-reklamasi yang lebih besar, reklamasi pantai seluas 2500ha di sebelah utara Pulau-Jawa, dinamakan Proyek-Pantura.
Bamboo helps decrease project expenses.
Bamboo Trees grow rapidly throughout the entire land of East, South East till South-Asia. Bamboo is used for household, artistic decoration, cooking utensils, ornaments, fine arts, music instruments, security-tools, building equipment, transportation tools and others. In the two last decades, the bamboo function is developed in the field of civil-engineering to decrease project expenses. The Pantai Mutiara Project in North Jakarta is a project of coast reclamation by piling up coast at sea floor deepness -2.0m till -4.0m with sand and thickened till the average of 8m. To prevent piling up of sand caused by wave forces scouring, a protector structure called breakwater or seawall is needed.The Structure seawall consists of hoard rubble mound which is closed by an armor concrete (tetrapod), to protect the land hoard as long as, the property line. Because the bottom of the North sea of Jakarta consist of soft mud with an average of 18m, the weight of the seawall which is predicted as heavy as 500 tons/m will immediately sink into the mud.Many alternatives are met to overcome it, for example with replacement soil, sand column, stone column, dynamic compaction, geo textile and others. Professor Dr. Ir. A.R. Soehoed, the Consultant Engineer from PT. Puri Fadjar Mandiri Indonesia, has found a cheap innovation, natural and safe, to overcome the problem settlement and sliding referred.A settlement of 45m seawall is overcome with bamboo clusters; seven bamboos are bound grow into one nip vertical drain, than it is piled forming in matrix formation with a space of 1.5m beneath the seawall. Above the bamboo clusters is laid bamboo raft; consist of seven layers, each of the layer consists of 60 bamboos, tied together to prevent sliding.Generally settlements are overcome with planting a sand-column or stone column, and sliding is overcome with geo textile. Nevertheless the innovation of bamboo clusters and bamboo raft, the Reclamation Project of Pantai Mutiara can exist 15 year up till now. This Innovation will also be used for larger reclamation projects, coast reclamation with a width of 2500ha beside North Java, named Proyek Pantura.