Interaksi dinding tiang bambu dengan pasir dalam model bidimensional

LILIWARTI, Prof.Dr.Ir. Kabul Basah Suryolelono, Dip.HE.,DEA

2005 | Tesis | S2 Teknik Sipil

Potensi bambu di Indonesia mempunyai prospek yang sangat baik, karena bambu mempunyai keunggulan, sifat mekanik (kuat lentur dan kuat tarik) yang relatif tinggi, sehingga dapat dimanfaatkan sebagai pengganti material fondasi lainnya pada konstruksi fondasi tiang. Bambu sebagai bahan dasar pembuatan tiang pancang banyak digunakan untuk perkuatan tanah (soil reinforcement), khususnya pada lapisan tanah lunak. Untuk itu, perlu adanya tinjauan interaksi antara bambu dengan tanah. Pada penelitian ini bambu yang digunakan yaitu bambu Apus (Gigantochloa Apus) yang telah diawetkan dengan cara direndam, tanah yang digunakan yaitu pasir pantai yang bergradasi seragam (bulat). Bambu yang digunakan terdiri dari 3 variasi yaitu, bambu tanpa ruas, bambu dengan ruas di tengah dan bambu dengan ruas selang seling, dilaksanakan uji beban dan uji geser langsung. Uji beban dilakukan dalam model bidimensional. Beban diberikan saat tahanan ujung dan tahanan friksi bekerja (Qu), kemudian beban diberikan saat tahanan ujung saja yang bekerja (Qb). Tahanan friksi didapat dari selisih tahanan total dan tahanan ujung. Masing-masing variasi dilakukan sepuluh kali pengujian dan diambil reratanya. Pada uji beban juga diamati deformasi butiran tanah di sekitar benda uji. Hasil uji geser langsung menunjukan perilaku interaksi antara pasir dengan bambu, bambu tanpa ruas menghasilkan sudut geser antar bambu-pasir lebih kecil dari pada bambu yang ada ruasnya. Pada uji beban memberikan hasil yang sama, karena pada permukaan yang kasar tegangan geser yang terjadi cendrung menuju ketegangan geser ultimit tanahnya. Sudut geser dalam antara pasir-pasir 370, pasirbambu tanpa ruas (δ = 290), pasir-bambu ruas selang seling (δ = 300), dan pasirbambu ruas di tengah (δ = 320). Deformasi tanah memperlihatkan gerakan butiran tanah akibat beban paling besar terjadi di bawah tiang, arah gerakan searah beban, sedangkan pada dinding tiang pergerakan butiran tanah searah pergerakan tiang.

The use of bamboo in Indonesia has a good prospect because it has some advantages in the mechanical properties, for instance high tensile and bending strengths. These properties show that bamboo could be used as an alternative material for pile foundation, and soil reinforcement especially as reinforcement in soft clay. Considering these conditions, it is necessary to have a study on interaction between bamboo and soil. The bamboo used in this research was gigantochloa apus and the sand type was coastal sand with uniform gradation (rounded grain). Before the bamboo was used, it was soaked for preservation. The variations of bamboo for the sample were noninternodes, middle internodes, and varying position of internodes. The tests carried out were direct sher test and load test. Load test was carried out in two dimensional model. The first series at load test was conducted to measure the end resistance and the friction resistance (total resistance). The second series at load was carried out to measure the end resistance . Frictional resistance was obtained from the difference value between the total resistance and the end resistance. The test was carried out ten times for each variation and then the average value was calculated. The deformation of the soil particle under the pile was also observed during the test. The results of direct shear test show the interaction between sand and bamboo. Non-internodes bamboo has smaller internal friction angle compared with internodes bamboo. The results of load tests also show the same pattern. Non internodes bamboo has smaller shear resistance compared with internodes bamboo, becauce at the coarse surface shear stress trend to be ultimit shear stress of the soil. The internal friction angles (ϕ) obtained from the tests was 37o for sand-sand. The friction angle for sandbamboo (δ) were 29o for sand-non internodes bamboo, 30o for sand-bamboo with varying position of internodes and 32o for sand-middle internodes bamboo. Soil deformation showed that the soil particle movement due to the largest load occurred under the sample.The soil particle moved parallel to the direction of loading for soil under the pile. At side wall of the pile the soil particle moved parallel to the direction of pile.

Kata Kunci : Konstruksi Bangunan,Bambu,Nilai Friksi, bamboo, interface, uniformly gradated sand (rounded