Garuda - Garba Rujukan Digital

Ahmad Rifa’I

Universitas Gadjah Mada

Author-ID : 2749636

Civil Engineering, Building, Construction & Architecture Engineering Environmental Science Materials Science & Nanotechnology Transportation

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Pengaruh Penambahan Abu Vulkanik pada Tanah Lunak terhadap Modulus Geser Maksimum Berdasarkan Pengujian Triaksial U-U Hadi Wira Nasarani; Ahmad Rifa’I; Hary Christady Hardyatmo
Jurnal Tekno Global Vol 8, No 1
Publisher : UNIVERSITAS INDO GLOBAL MANDIRI

ABSTRACTAs one country that has 83 volcanoes that are still active, Indonesia has natural resources in the form of volcanic ash which is pozzolan. In addition Indonesia is also a vast country so to support the equitable distribution of supporting facilities such as roads to support the development process. In the implementation of road construction is often found soil conditions that have low bearing capacity. Therefore, it is necessary to handle the subgrade of road that has low carrying capacity through stabilization with agent material.One material that meets the pozzolan material is volcanic ash. Volcanic ash of Mount Merapi has pozzolanik nature that is the nature of materials that will wake solid mass that increases harder as time increases and is difficult to dissolve in water when reacted with CaO contained in clay and lime.The study was conducted with a mixture of volcanic soil with 14 days of curing. Through triaxial testing of the efective confining pressure (σ0) of 547 kN / m2 with void ratio (e) of 1,059. The calculation of shear modulus (Gmax) was done by empirical formula proposed by Zen et al (1978) and obtained Gmax value of 134,044 Mpa as the biggest shear modulus with 25% volcanic ash and 5% lime.Keywords : pozzolan, stabilization, effective confining pressure, void ratioABSTRAKSebagai salah satu negara yang memiliki banyak gunung api yang masih aktif, Indonesia memiliki sumber daya alam berupa abu vulkanik yang melimpah dan bersifat pozzolan. Selain itu indonesia juga merupakan negara yang luas sehingga untuk menunjang pemerataan pembangunan diperlukan sarana penunjang berupa jalan untuk mendukung proses pembangunan. Dalam pelaksanaan pembangunan jalan sering dijumpai kondisi tanah yang memiliki daya dukung rendah. Oleh karena itu perlu penanganan terhadap tanah lunak yang memiliki daya dukung rendah melalui stabilisasi dengan bahan tambah. Salah satu material yang memenuhi material pozzolan adalah abu vulkanik. Abu vulkanik Gunung Merapi mempunyai sifat pozzolanik yaitu sifat bahan yang akan membentuk massa padat yang bertambah keras seiring bertambahnya waktu dan sukar larut dalam air apabila bereaksi dengan CaO yang terdapat pada lempung dan kapur. Penelitian dilakukan dengan campuran tanah-abu vulkanik dengan pemeraman 14 hari. Variasi kadar campuran yang diberikan adalah 0%, 20%, 25%, dan 30%. Selain itu dilakukan penambahan kapur 5% yang bertujuan memberikan ikatan yang baik apabila dicampur dengan tanah lempung.Melalui pengujian triaksial UU diperoleh tahanan kekang efektif (σ0)sebesar360kN/m2 dengan angka pori (e) sebesar 1,059. Perhitungan modulus geser (Gmax) dilakukan dengan rumus empiris yang diusulkan Zen dkk (1978) dan diperoleh nilai Gmax sebesar 134,044 Mpa sebagai modulus geser terbesar dengan kadar abu vulkanik 25% dan kapur 5%.Kata kunci : pozzolan, stabilisasi , tahanan kekang efektif, angka pori

Analisis Kelongsoran Lereng Akibat Pengaruh Tekanan Air Pori di Saluran Induk Kalibawang Kulonprogo Hesti Subiyanti; Ahmad Rifa’i; Rachmad Jayadi
Semesta Teknika Vol 14, No 1 (2011): MEI 2011
Publisher : Universitas Muhammadiyah Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/st.v14i1.566

During rainy seasons, landslide occurs every year in Talang Bawong, Kalibawang Irrigation Channel thatcan damage houses, school building, bridge and the channel. Considering this fact, a numerical analysis by modeling the slope at the site was conducted. The objectives of this research were to identify the rain characteristic in the research site and to recognize its influence towards the change of water pressure in soil as well as the slope failure. The input data of this analysis were slope topography, physical and mechanical properties of soil applied. Groundwater flow in the slope model was numerically simulated by using SEEP/W software. Designed rainfall with appropriate return period was determined by analizing the maximum daily rainfall data with the aid of HAVARA software, while rainfall depth distribution was completed by applying frequency analysis. The historical daily rainfall data (1985 – 2004) were obtained from Kalibawang rain stasiun. Six rainfall models, as follow: initial condition (no rain) (model I), heavy rain in a short duration (model II), normal rain 25 mm and 40 mm in a long duration (model III), normal rain 20 mm in a long duration (model IV), heavy rain followed by normal rain 20 mm (model V), and normal rain 20 mm followed by heavy rain (model VI) Were analyzed. The output of the simulation was water pressure distribution data, which in turn being used as input data in analyzing slope stability using the SLOPE/W software. The result of the research showed that the highest rainfall with 2-year-return period was 114 mm while the dominant duration was 4 hours/day, and it was applied in the model II. The result showed that, a normal rain in a long duration is more severely influenced the change in water pressure than a heavy rain in a short duration. The safety factors are 1,444 for no rain condition, 1,418 for 114 mm rain for 4 hours, 1,208 for 25 mm and 40 mm rains, 0,982 for 20 mm rain, 1,397 for heavy rain followed by normal rain, and 1,402 for normal rain followed by heavy rain. In addition, a 20 mm normal rain on the 61st day resulted in the most severe influence on the slope failure.

Analisis Potensi Likuifaksi Di Kawasan Underpass Yogyakarta International Airport (YIA) Muhamad Agung Rahman; Mochammad Syidik Hidayat; Teuku Faisal Fathani; Ahmad Rifa’i
JUTEKS : Jurnal Teknik Sipil Vol 5 No 1 (2020): JUTEKS (Jurnal Teknik Sipil)
Publisher : P3M- Politeknik Negeri Kupang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.32511/juteks.v5i1.643

Fenomena likuifaksi akibat gempa merupakan hilang/berkurangnya daya dukung tanah karena hilangnya inter-granular stress antar butir-butir tanah untuk menahan beban getaran gempa akibat naiknya tegangan air pori. Dampak likuifaksi dapat menimbulkan kerugian dan kerusakan yang besar pada infrastruktur. Evaluasi potensi likuifaksi dilakukan di kawasan Underpass Yogyakarta International Airport (YIA) dengan menggunakan data N-SPT sebanyak lima data bor. Analisis potensi likuifaksi bertujuan untuk mengetahui nilai safety factor (SF) di kawasan tersebut. Peristiwa likuifaksi akan terjadi jika nilai SF lebih kecil dari satu. Nilai safety factor (SF) adalah perbandingan nilai Cyclic Resistance Ratio (CRR) yang merupakan tahanan tanah terhadap likuifaksi dan Cyclic Stress Ratio (CSR) yang merupakan tegangan geser yang timbul akibat gempa. Hasil analisis potensi likuifaksi di kawasan Underpass YIA menunjukan bahwa lapisan tanah pasir di Underpass YIA berpotensi mengalami likuifaksi pada kedalaman 4-6 m dari permukaan tanah pada titik bor BH01 dan BH05. Sedangkan pada titik bor BH02, BH03, dan BH04, lapisan tanah pasir di lokasi Underpass YIA tidak berpotensi terjadi likuifaksi. Untuk menghilangkan potensi terjadinya likuifaksi pada struktur underpass dilakukan penggalian di kedalaman 4-5 m serta dilakukan penggantian material (replacement) tanah asli dengan material sirtu setebal 50 cm.

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