Pengaruh pemasangan kelompok tiang terhadap keniakan pelat dalam sistem "Nailed Slab" yang terletak di atas tanah dasar ekspansif

TAA, Peregrinus Dhae Siga, Dr. Ir. Hary Christady H, M.Eng.,DEA

2010 | Tesis | S2 Teknik Sipil

Konstruksi perkerasan kaku sering menimbulkan masalah bila terletak pada tanah dasar (subgrade) jenis lempung ekspansif. Penambahan kadar air menyebabkan lempung mengembang dan sebaliknya pengurangan kadar air lempung menyusut. Salah satu penanganannya adalah dengan kelompok tiang Sistem “Nailed Slab” (Pelat Terpaku). Sistem Pelat Terpaku memanfaatkan perlawanan tiang vertikal dan tekanan tanah lateral yang bekerja di sekeliling dinding tiang-tiang beton. Pada saat tanah mengembang dan dibebani tiang-tiang akan berfungsi sebagai paku pelat yang melawan rotasi tiang dan memperkecil lendutan. Pada penelitian ini dilakukan pengamatan terhadap perilaku model Sistem “Nailed Slab” (Pelat Terpaku) dari pelat ukuran 75 x 9 x 1,5 cm3 dengan atau tanpa perkuatan tiang dimana jarak antar tiang ialah 5d dan 6d dimana d ialah diameter tiang beton 2 cm, serta tinggi tiang yang bervariasi yakni 10 cm, 15 cm dan 20 cm. Pengamatan terhadap perilaku pengembangan pada model Sistem Pelat Terpaku di laboratorium dengan metode pembasahan dari saluran drainase (lapisan pasir) samping kiri dan kanan pelat. Variabel yang ditinjau pengaruh adanya tiang, jarak tiang, panjang tiang adalah pengembangan, gaya tekan pengembangan, koefisien subgrade reaksi vertikal PLT, koefisien subgrade reaksi vertikal akibat tekan, dan koefisien subgrade reaksi vertikal pengembangan. Lendutan pelat dibandingkan antara pengamatan dengan perhitungan metode Beams on Elastic Foundation (BoEF). Hasil penelitian menunjukkan dengan adanya tiang dapat mereduksi defleksi akibat pengembangan dan pembebanan dengan perlawanan tiang vertikal, berat sendiri dari tiang dan adanya momen perlawanan tiang. Gaya tekan akibat pengembangan tanah dasar semakin ketengah semakin kecil. Hal ini menggambarkan kondisi resapan air dari pinggir ketengah pelat. Dengan adanya tiang, mampu mereduksi lendutan pelat dan menaikan nilai kv, dan nilai kv semakin besar seiring dengan semakin panjang tiang (L). Analisis lendutan dengan metode Beams on Elastic Foundation (BoEF) finite dengan beban (Q) = 0,4 kN pada penggunaan kv-tekan (kv-sistem) mendekati lendutan pada pengamatan.

Rigid pavement structure often creates problems when located over an expansive clay subgrade. The increase in water content cause swelling of the clay, whereas, water decrease could make the clay shrink. Since the loads which against soil swelling under the plates are the concretes and piles weights, one way to handle the problem is by using pile groups in Nailed Slab System. Nailed Slab System utilizes pile resistance and lateral earth pressure which works around the skin of concrete piles. When soil is swelling and loaded, the piles will serve as plate nails which against pile rotation and reduces deflection. In this research, observation the behaviors of model of Nailed Slab Sistem from 75 x 9 x 1.5 cm3 plates, with or without pile strengthening, in which piles spaced are 5d and 6d with d is the diameter of 2 cm concrete pile, and pile heights are 10, 15, and 20 cm. The observation on swelling behavior in Nailed Slab System was conducted in laboratory and using wetting method from drainage channel (sand layer) in the right and left sides of the plate. Observed variables which effected by pile existence, pile spacing, and pile heights are soil swelling, swelling pressure, coefficient of vertical subgrade reaction PLT, pressured coefficient of vertical subgrade reaction, and swelling coefficient of vertical subgrade reaction. Plate deflection was compared between observations by using Beams on Elastic Foundation (BoEF) calculation method. The results shows that pile existence could reduce the deflection which caused by swelling and loading by pile resistance, pile weight itself and pile resistance moment. Pressure force caused by subgrade swelling is become smaller to the center. This reflects the condition of water infiltration from edge to center of plates. Pile existence could reduce plates deflection and increases coefficient of subgrade reaction (kv) value which higher with length of the pile (L). Deflection analysis using Beams on Elastic Foundation (BoEF) method was finite with load (Q)=0.4 kN when kv-press(kv-system) near to deflection in observation.

Kata Kunci : Pengembangan, Sistem pelat terpaku, Koefisien reaksi subgrade, Beams on elastic foundation (BoEF)