Analisis deformasi dua dimensi pada Geogrid akibat beban lalu lintas kendaraan

HANMI, A. Adhe Noor P. Santhika, Prof.Dr.Ir. Kabul Basah Suryolelono, Dip.HE.,DEA

2005 | Tesis | S2 Teknik Sipil (Geoteknik)

Konstruksi embankment jalan raya di atas tanah lempung lunak (soft clay) sering menimbulkan kendala baik dalam tahap pembangunan maupun pada tahap pasca konstruksinya. Penggunaan floating piles dan geogrid merupakan salah satu cara yang dapat digunakan untuk mengatasi kendala tersebut. Kombinasi geosintetik dan floating piles merupakan suatu kombinasi yang spesifik, karena selain terjadi perilaku tegangan-regangan yang beragam pada luasan geosintetiknya, terjadi pula perilaku jepit pada pertemuan pile caps dan bahan geosintetik. Studi terhadap deformasi embankment selama fase konstruksi, akhir – akhir ini dilakukan dengan analisis berdasar pada metode elemen hingga. Software yang digunakan dalam analisis ini adalah Plaxis Version 7.0. Tanah dasar dan timbunan dimodelkan sebagai model material Mohr-Coulomb, sedangkan geosynthetics dimodelkan sebagai geotextile element. Floating piles dan pile caps dimodelkan sebagai beam element. Beban kendaraan dimodelkan sebagai beban terbagi rata dan beban titik statis yang bersifat permanen di bagian atas permukaan embankment. Bidang kontak antara tanah dan reinforcement dimodelkan dalam dua tipe yaitu rigid embankment dan interface embankment. Perbandingan hasil simulasi dilakukan dengan membandingkan output simulasi numeris terhadap hasil pengukuran lapangan pada unreinforced embankment (normal embankment). Hasil simulasi numeris menunjukan bahwa pertambahan perpindahan terbesar terjadi pada awal penimbunan (H=1,1 m) sebesar 0,6585 m pada arah horisontal (hasil pengukuran lapangan sebesar 0,36235 m) dan -0,2512 m pada arah vertikal (hasil pengukuran lapangan sebesar -0,079 m). Aplikasi geogrid dan floating piles mengurangi perpindahan tanah dasar dan geogrid. Nilai maksimum perpindahan terjadi pada model interface embankment saat ketinggian embankment mencapai 3,1m yaitu sebesar 0,7866 m pada arah horisontal dan - 0,2849 m pada arah vertikal, sedangkan defleksi geogrid yang terjadi sebesar - 0,288 m. Aplikasi beban terbagi rata dan beban titik kendaraan menambah perpindahan tanah dasar dan geogrid, dengan nilai maksimum terjadi pada model interface embankment. Perpindahan akibat beban terbagi rata kendaraan 50 kPa sebesar 2,2248 m pada arah horisontal dan sebesar -1,4206 m pada arah vertikal, defleksi geogrid yang terjadi sebesar -1,4206 m. Beban titik kendaraan sebesar 60 kN mengakibatkan perpindahan tanah sebesar 1,12802 m pada arah horisontal dan sebesar -0,65675 m pada arah vertikal, sedangkan defleksi geogrid yang terjadi sebesar -0,65675 m.

Construction of embankment for roadway on soft clay often caused problems either during the construction phase or after the contruction phase. The usage of floating piles and geogrid was one of methods to over come the problem. The combination of both material was spesific because there were various stress – strain behaviours in geosynthetic. There was also a fixed behaviour at the contact area of geogrid and floating piles. In the present study, deformation of embankment during construction phase was analysed by finite element method, using Plaxis computer program package (version 7.0). Mohr Coulomb model was used for foundation soil and fill material. Geosynthetics reinforcement was modelled in simulation as geotextile element, floating piles and pile caps were modelled as beam element. Vehicle load was modelled as static surcharge and static point load that permanently worked on the surface of embankment. The interface between soil and other material were modelled in two type of modelling, they were non-interface (rigid) and interface embankment model. The comparations of research results were obtained by comparing the outputs of numerical simulation and original field measurement datas for unreinforced embankment (normal embankment). The results of the research showed that the increments of soil displacement were 0.6585 m for horizontal direction (field measurement result was 0.36235 m) and -0.2512 m for vertical direction (field measurement result was -0.079 m). The usage of geogrid and floating piles as reinforcements decreased soft clay displacement. The maximum displacements in interface embankment when the height of embankment was 3.1 m were 0.7866 m for horisontal direction and - 0.2849 m for vertical direction, the deflection of geogrid was -0.288 m. The application of surcharge vehicle load and point vehicle load increased the displacements of soft clay and geogrid with the maximum displacements were occurred in interface embankment models. The displacements of soft clay caused by vehicle surcharge load (50 kPa) were 2.2248 m for horizontal direction and -1.4206 m for vertical direction, the deflection of geogrid was -1.4206 m. The displacements of soft clay and geogrid caused by vehicle point load (60 kN) were 1.12802 m for horizontal direction and -0.65675 m for vertical direction, the deflection of geogrid was -0.65675 m.

Kata Kunci : Konstruksi Jalan Raya,Tanah Lempung,Embankment,Geogrid,embankment, floating piles, geogrid, vehicle surcharge load, vehicle point load