Pengaruh Penambahan Serat Karung Plastik dan Abu Kayu Pada Tanah Lempung Terhadap Peningkatan Nilai CBR Subgrade Jalan Pengembur-Pantai Selong Belanak Lombok Tengah

Abstract

Akses jalan menuju kawasan wisata Pantai Selong Belanak, khususnya di Desa Pengembur, Kecamatan Pujut, Kabupaten Lombok Tengah, mengalami banyak kerusakan pada struktur lapisan jalan. Kondisi ini disebabkan oleh keberadaan tanah lempung yang rentan terhadap kerusakan akibat erosi dan perubahan kadar air, serta nilai California Bearing Ratio (CBR) yang rendah. Tanah dengan stabilitas yang buruk memerlukan upaya stabilisasi untuk meningkatkan daya dukungnya, khususnya di wilayah yang mendukung pengembangan pariwisata. Penelitian ini bertujuan untuk menganalisis pengaruh penambahan abu kayu dan serat karung plastik sebagai bahan campuran stabilisasi tanah lempung terhadap peningkatan nilai CBR. Sampel tanah diambil dari Desa Pengembur dan diuji di Laboratorium Mekanika Tanah, Fakultas Teknik, Program Studi Teknik Sipil, Universitas Muhammadiyah Mataram. Variasi campuran meliputi abu kayu sebesar 20%, 25%, 30% dan serat karung plastik sebesar 1%, 2%, 3%. Hasil pengujian menunjukkan bahwa nilai CBR tanah asli tanpa rendaman adalah 6,36%. Setelah penambahan abu kayu 30% dan serat karung plastik 1%, nilai CBR meningkat menjadi 9,96% (peningkatan sebesar 56,60%). Pada variasi abu kayu 30% dan serat karung plastik 2%, nilai CBR meningkat signifikan menjadi 15,35% (peningkatan sebesar 141,35%). Namun, penambahan serat karung plastik hingga 3% menyebabkan nilai CBR menurun menjadi 11,83% (penurunan sebesar 86,00%). Penelitian ini menyimpulkan bahwa kombinasi abu kayu dan serat karung plastik secara signifikan meningkatkan nilai CBR tanah lempung, efektif untuk stabilisasi tanah, serta mendukung pembangunan infrastruktur jalan di kawasan pariwisata.

Abstract:  The road access to the Selong Belanak Beach tourism area, particularly in Pengembur Village, Pujut District, Central Lombok Regency, has experienced significant damage to the road structure. This condition is caused by clay soil, which is prone to damage due to erosion and changes in moisture content, as well as a low California Bearing Ratio (CBR) value. Soil with poor stability requires stabilization efforts to improve its bearing capacity, especially in areas that support tourism development. This study aims to analyze the effect of adding wood ash and plastic sack fibers as a soil stabilization mixture on improving the CBR value. Soil samples were taken from Pengembur Village and tested in the Soil Mechanics Laboratory, Faculty of Engineering, Civil Engineering Study Program, Muhammadiyah University of Mataram. The mix variations include 20%, 25%, and 30% wood ash and 1%, 2%, and 3% plastic sack fibers. The test results show that the CBR value of the original soil without soaking is 6.36%. After adding 30% wood ash and 1% plastic sack fibers, the CBR value increased to 9.96% (a 56.60% increase). In the variation with 30% wood ash and 2% plastic sack fibers, the CBR value significantly increased to 15.35% (a 141.35% increase). However, adding plastic sack fibers up to 3% caused the CBR value to decrease to 11.83% (an 86.00% decrease). This study concludes that the combination of wood ash and plastic sack fibers significantly increases the CBR value of clay soil, effectively stabilizes the soil, and supports the development of road infrastructure in tourist areas.