Pengaruh tekanan Overburden terhadap tahanan gesek dinding tiang pada tanah pasir

JAMIN, Mohamad, Ir. Agus Darmawan Adi, M.Sc.,Ph.D

2005 | Tesis | S2 Teknik Sipil

Tekanan tanah lateral dipengaruhi oleh tekanan akibat berat sendiri tanah di atasnya (overburden), hal ini akan berpengaruh terhadap tahanan gesek interface tanah-tiang. Dalam dunia teknik sipil khususnya bidang geoteknik banyak masalah yang melibatkan interaksi antara tanah dan tiang. Sebagai contoh struktur-struktur dam, pipa-pipa dalam tanah, sistem fondasi bangunan, struktur basement-dalam pada pencakar langit Penelitian ini bertujuan untuk mempelajari pengaruh tekanan overburden terhadap kuat gesek interface tanah-tiang secara eksperimental. Tiang yang digunakan dalam penelitian ini adalah pipa baja, tiang beton, dan tiang kayu masing-masing berdiameter sama sebesar 48.3 mm dengan panjang interface 200 mm. Tanah sebagai media menggunakan pasir Kali Progo, Srandakan, Bantul, Daerah Istimewa Yogyakarta yang terdiri dari fraksi gravel 4.77%, pasir 94.06% dan silt/clay 1.17% serta menurut USCS bergradasi buruk (Cu=2.8, Cc=0.75). Metode pembebanan menggunakan 2 (dua) sistem yaitu stress controlled dan strain controlled. Hasil pengamatan besarnya pengaruh tekanan overbuden terhadap tahanan gesek satuan dibandingkan dengan yang disampaikan oleh Vesic (1967) dan Coyle et al. (1981). Hasil hituingan untuk Kd dan d dibandingkan dengan yang disampaikan oleh Bowles (1981), Tavenas (1971), Mansur & Hunter (1970), dan Brown (1965b) maupun Aas (1966). Hasil penelitian menunjukkan bahwa pengaruh tekanan overburden, sv terhadap koefisien tekanan tanah (Kd) bervariasi, semakin besar tekanan overburden nilai Kd semakin kecil. Pengaruh tekanan overburden terhadap koefisien gesek satuan (fs) cukup besar untuk tekanan overbuden kurang dari 160 kN/m2, sedangkan bila lebih dari 160 kN/m2 pengaruhnya relatif kecil. Nilai sudut gesek antara tanah dan tiang (d) akibat tekanan overburden sampai dengan 400 kN/m2 penurunannya cukup besar, mulai dari sekitar 600 sampai dengan 250, sedangkan tekanan overbuden lebih besar dari 400 kN/m2 nilai d sekitar 250 sampai dengan 200.

Lateral earth pressure was influenced by soil pressure due to its own weight (overburden). This condition would influence the shear strength of soil-structure interface. There were many geotechnical problems involved the interaction between soil-structure. For instance dams, underground pipelines, building foundations and the basement of sky scrapers building. The aim of this research was to know the influence of overburden pressure to the shear strength of soil-structure interface. The materials used in this research were steel pile, concrete pile, and wooden pile. The diameter of all piles were 48.3 mm and the length of interface was 200 mm. The soil used for this research was taken from Progo river, Srandakan, Bantul, Yogyakarta. The compositions of soil were 4.77 % gravel fraction, 94.06% sand, and 1.17 % silt/clay. The gradation of the soil was poor (USCS), (Cu = 2.8; Cc = 0.75). There were two types of loading methods used in this research, they were stress controlled and strain controlled method. The monitoring results for the influence of overburden pressure to unit shear strength were the compared to unit shear strength those were explained in Vesic (1967) and Coyle et all (1981). The analysis results for Kd and d were then compared with the parameters explained in Bowles (1981), Tavenas (1971), Mansur and Hunter (1970), Brown (1965b) and Aas (1966). The results of this research showed that the influenced of overburden pressure (sv) to coefficient of lateral earth pressure was variated, when the overburden pressure increased, the value of Kd decreased. The influence of overburden pressure to the coefficient of unit shear strength was significant when the overburden pressure was lower than 160 kPa. The influence was low when the overburden pressure was higher than 160 kPa. The decreasement of effective friction angle (d) when overburden pressure reached 400 kPa was 60o – 25o. The value of d was quite constant (200 – 250) when the overburden pressure was higher than 400 kPa.

Kata Kunci : Geoteknik ,Interface Tanah Tiang, Tekanan Overburden, overburden pressure, confining pressure, unit friction resistance, granuler soil.