Stabilisasi tanah lempung ekspansif dengan campuran kapur dan abu sabut kelapa sawit

ARIYANTI, Rini, Ir. Suryo Hapsoro Tri U., Ph.D

2005 | Tesis | S2 Teknik Sipil

Tanah lempung mempunyai kuat dukung rendah dan sangat sensitif terhadap kadar air. Kondisi seperti ini sangat tidak menguntungkan, apabila di atasnya dibangun konstruksi jalan raya. Masalah yang timbul setelah pembangunan jalan adalah kerusakan jalan yang ditandai dengan retak-retak, bergelombang maupun penurunan badan jalan. Oleh karena itu sifat fisis dan mekanis tanah tersebut harus diperbaiki. Untuk memperbaiki sifat fisis dan mekanis tanah lempung ini perlu dilakukan penelitian tentang stabilisasi tanah ini dengan bahan stabilisasi berupa kapur dan abu sabut sawit. Metode yang dilakukan adalah mencampur bahan stabilisasi kapur dan abu sabut sawit dengan persentase penambahan kapur 0%; 2,5%, sedangkan persentase penambahan abu sabut sawit 0%; 3,5%; 7%, 12% dan 18%. Untuk mengetahui perubahan sifat fisis dan mekanis dilakukan uji terhadap tanah asli maupun campuran tanah, kapur dan abu sabut sawit berupa uji batas konsistensi, uji gradasi, uji gravitas khusus, uji triaksial Unconsolidated-Undrained (UU) dan uji California Bearing Ratio (CBR). Uji triaksial UU ditinjau terhadap perawatan 3 hari dan uji CBR ditinjau terhadap perawatan 3 hari dengan perendaman 4 hari. Selain itu, dilakukan uji kandungan unsur-unsur kimia terhadap tanah, kapur dan abu sabut sawit serta uji mineralogi terhadap tanah asli. Hasil uji tanah asli menunjukan bahwa, tanah tersebut merupakan tanah dengan indeks plastisitas 63,28% dan sebagian besar terdiri dari mineral montmorillonite, nilai aktivitas sebesar 0,64 menurut ASTM merupakan CH yaitu lempung anorganik dengan plastisitas tinggi. Hasil uji CBR tanah asli dengan kondisi terendam diperoleh nilai CBR sebesar 4,14% dengan pengembangan sebesar 4,98% dan hasil uji triaksial (UU) tanpa rendaman memberikan nilai c =52,35 kN/m2 dengan sudut gesek dalam (Ï•) sebesar 12,97o. Penambahan abu sabut sawit, dapat memperbaiki sifat fisis dan sifat mekanis tanah tersebut. Nilai sudut gesek dalam (Ï•) menjadi 18,13o, terjadi peningkatan maksimum sebesar 39,78% dan nilai kohesi (c) 191,25 kN/m2, terjadi peningkatan maksimum sebesar 264,99%. Nilai CBR menjadi 6,99%, terjadi peningkatan maksimum sebesar 68,84% dan menurunkan nilai swelling sebesar 67,07%. Begitu juga pada penambahan campuran kapur dan abu sabut sawit, nilai sudut gesek dalam (Ï•) menjadi 19,50o, terjadi peningkatan maksimum sebesar 50,27% dan nilai kohesi (c) 186,72 kN/m2 terjadi peningkatan maksimum sebesar 256,68%. Nilai CBR menjadi 7,63%, terjadi peningkatan maksimum sebesar 61,35% dan menurunkan nilai swelling sebesar 82,53% .

Clay is known as soil with low bearing capacity. It also has high sensitivity with water content. This condition is not good especially if road pavement is constructed on this soil. The problems that is usually occurred after we construct the pavement are road damages, they are detected by the existance of cracks, corrugating road or settlement of the road. One of methods to overcome this problem is by improving the physical and mechanical properties of the soil itself. The method that is used to increase these soil properties is stabilization. This research was carried out to know the effect of lime and palm husk ash materials as soil stabilizer. The procedure that was carried out was mixing the stabilizer (lime and palm husk ash). The percentage of lime addition was 0% and 2,5%, meanwhile the percentage of palm husk ash addition was 0%, 3,5%, 7%, 12% and 18%. Some laboratory tests were also held to know the effect of soil, lime and palm husk ash mix to mechanical and physical properties of the original soil. The laboratory tests were consistency test, gradation test, spesific gravity test, triaxial UU test and California Bearing Ratio (CBR) test. Chemical content test and mineralogy test for original soil were also carried out. The triaxial samples were cured for three days, meanwhile in CBR test, the samples were soaked for four days. The results of the test for original soil showed that the value of plasticity index was 63,28%, the value of activity was 0,64 and most of them consisted of montmorillonite. In accordance with ASTM, the soil was classified in CH type that was anorganic clay with high plasticity. The CBR value for soaked sample was 4,14% with the value of swelling was 4,98%. Triaxial test (UU) for unsoaked sample gave the value of cohesion (c) and internal friction angle (φ), they were 52,35 kPa and 12,97o subsequently. The addition of palm husk ash could improve the physical and mechanical properties of soil. There were some increments of internal friction angle value (φ), cohesion value (c) and CBR value due to the stabilization, the maximum increment for φ was 39,78%, so the value became 18,13o. The maximum increment for c was 264,99%, so the value became 191,25 kPa. Meanwhile, the maximum increment for CBR value was 68,84%, so the CBR value became 6,99%. The reduction also occured due to the mixing of palm husk ash, the reduction of swelling value was 67,07%. The addition of palm husk ash and lime could cause some reductions and some increments. The maximum increment for c was 256,68%, so the value became 186,72 kPa. The maximum increment for φ was 50,27%, so the value became 19,5o. Meanwhile, the maximum increment for CBR value was 61,35%, so the value became 7,63%. The reduction of swelling value was 82,53%.

Kata Kunci : stabilisasi, lempung, kapur, abu sabut sawit, CBR, Triaksial, Swelling, stabilization, clay, lime, palm husk ash, triaxial