Consolidation settlement is a general geotechnical problem particularly found in the area where is composed of soft soil. It is caused by the discharge of pore water pressure induced by the increase of stress in the soil mass. Construction of runway above soft soil requires analysis for stability related to the reduction of consolidation settlement and the recovery. This study aims to analyze the settlement comprehensively using empirical methods of Prefabricated Vertical Drains (PVD) and preloading installation. Preloading is a technique by which consolidation of soil can be achieved to a substantial amount before the imposition of actual construction load. According to soil investigation, the characteristic of the soil layer is clay soil, which has the potential to consolidation settlement. The result of the settlement analysis of the taxiway in the research area is from 33 cm to 214 cm. It takes ten years for primary consolidation to reach a 90% degree of consolidation. However, in the Hansbo method of Prefabricated Vertical Drains (PVD) and preloading are applied, with triangular configurations in depth of 11 meters and duration for variation embankment spacing of 1 m is 79 days, 1.5 m is 202 days and 2 m is 390 days. The conclusion of efficient distance of PVD installation and preloading is spacing of 1 m with 79 days for primary consolidation.

Increasing development of infrastructure in Indonesia has driven the need for effective ground improvement methods to accelerate the consolidation of soft soil, which is estimated to occupy around 10% of the country’s land area. A prefabricated vertical drain combined with vacuum preloading is among the most effective methods for this purpose. However, the prefabricated vertical drain creates a smear zone in the surrounding soil area during installation. This study examines the effectiveness of a newly developed mandrel system in reducing the smear zone during prefabricated vertical drain installation. Large-scale consolidation tests at a macro level and microstructure analysis using scanning electron microscopy at a micro level were employed to investigate the effect of soil water content and shear strength. The results show that the water content and shear strength of the soft soil gradually increased in the inner smear zone and transition zone, while both decreased in the radial distance. Furthermore, the soil structure underwent a transformation in which the particle area and pore area became a closed flake structure, and apparent agglomeration occurred. The test results indicate that the newly developed mandrel system can effectively reduce the smear zone. The macro to micro test results demonstrated that the mandrel system is successful in reducing the smear zone effect.

Liquefaction is a liquefied soil phenomenon caused by cyclic load or earthquake. One of the soil liquefaction prevention methods is the installation of stone column. The stone column is a column filled with compacted rock fragments. It has 50 cm in diameter and 5 m deep This method is believed to reduce the excess pore water pressure that occurs during an earthquake. The stone column has been applied in many construction projects which located in high potential of liquefaction area. This research aims to know the effectiveness of stone column in reducing the liquefaction potential. This research conducted by using borelog data and soil laboratory test. This research also runs the numerical simulation of soil liquefaction with stone column stabilization. The variations in column spacing (2 m; 1.5 m; and 1 m) and subsurface review point (1 m; 1.5 m; 2 m; and 2.5 m) will be applied by using Quake/W from Geostudio 2012 software. The results show that the liquefaction potential can be reduced with the closer stone column spacing up to 1.5 m. Reduction of pore water pressure and liquefaction potential only occurs in the initial period of the earthquake before reaching the peak of earthquake acceleration.ABSTRAKLikuefaksi merupakan fenomena pencairan tanah akibat adanya beban siklik atau gempa. Salah satu metode penanganan likuefaksi yaitu dengan melakukan instalasi stone column. Stone column merupakan suatu kolom yang diisi oleh fragmen batuan yang dipadatkan. Umumya kolom berukuran diameter 50 cm dan kedalaman hingga 5 m. Metode ini dipercaya dapat mengurangi tekanan air pori yang terjadi pada tanah saat gempa. Penelitian ini bertujuan untuk mengetahui efektifitas stone collumn dalam mengurangi potensi likuefaksi. Penelitian ini dilakukan dengan menggunakan data bor dan uji laboratorium. Simulasi numeris juga dilakukan berupa permodelan tanah dengan stabilisasi stone column. Variasi pada jarak stone solumn (2m; 1,5m; dan 1m) dan titik tinjau (1m; 1,5m; 2m; dan 2,5m) dilakukan dengan menggunakan perangkat lunak Quake/w dari Geostudio 2012. Hasil menunjukkan bahwa potensi likuefaksi dapat berkurang dengan jarak stone column yang semakin dekat hingga 1,5 m. Pengurangan tekanan air pori dan potensi likuefaksi hanya terjadi pada periode awal gempa sebelum mencapai puncak percepatan gempa.

Slope failure in the well site area in Aceh, Indonesia caused the termination of gas distribution and resulted in financial loss. Based on the visual observation, the slope failed due to the high intensity of rainfall, which influenced the reduction of soil shear strength of the slope embankment. Moreover, the slope reinforcement has been damaged due to the collapsed trees on the slope embankment. Slope stability analysis was carried out by using a two-dimensional (2D) numerical method in several section areas to determine the appropriate slope reinforcement or countermeasures. Based on the 2D slope stability analysis, the Building Information Modeling (BIM) was performed by using a 3D projection drawing to evaluate the detailed information of the area which was applied by the countermeasures system. This method describes the total area and material quantity covered by the countermeasure system to determine the information material quantity and land acquisition area. Furthermore, the implementation of BIM in this study provides detailed information during the construction process to ensure comprehensive landslide mitigation.

Likuefaksi merupakan kejadian dimana konsistensi tanah berubah dari padat menuju cair akibat berkurangnya tegangan efektif tanah. Hal ini dapat terjadi karena adanya beban siklik ataupun gempa bumi. Kejadian likuefaksi umumnya terjadi pada tanah dengan distribusi butiran pasir halus dan muka air tanah yang dangkal. Likuefaksi dapat menimbulkan kegagalan pada konstruksi maupun tanah seperti seperti sand boils, flow failures, lateral spreads, ground oscillation, kehilangan daya dukung, bangunan turun masuk ke dalam tanah, dan lain sebagainya. Penelitian ini bertujuan untuk dapat mengetahui potensi likuefaksi tanah dengan menggunakan permodelan 2 dimensi menggunakan perangkat lunak Quake/W. Data yang digunakan dalam permodelan ini yaitu data stratigrafi tanah yang berasal dari pemboran dan data karakteristik tanah meliputi distribusi ukuran butir, persentase butiran halus, dan indeks plastisitas tanah  hasil dari pengujian laboratorium. Selain data kondisi tanah, data gempa juga digunakan dalam permodelan. Data gempa yang digunakan yaitu berupa kurva time history perubahan percepatan terhadap waktu. Permodelan dilakukan dengan skenario kondisi statis dan kondisi dinamis agar memberikan gambaran bagaimana perubahan kondisi tanah sebelum dan setelah gempa. Perubahan tegangan efektif tanah ditinjau pada kedalaman 1m; 1,5m; 2m; dan 2,5m. Hasil permodelan menunjukkan bahwa terjadi penurunan tegangan efektif tanah hingga 30% pada masing-masing kedalaman.