Bamboo is a kind of natural resource that has ability to grow in varying conditions. Besides its high water absorbability as the main advantage of bamboo, effect of bamboo material structure can be utilized to improve characteristic of loose and poorly graded sand soil under saturated condition. This type of soil is very susceptible to liquefaction. An understanding of production process influence to the performance of bamboo materials type, influence of cement addition in the mixture and curing time to the mechanical behaviour were observed by static triaxial CU test. In addition, SEM (Scanning Electron Microscopic) analysis was also conducted to understand the particle interaction in mixture. This study can be developed as one of the proposed ideas in the utilization of environmental friendly materials in geotechnical field.

The Palukoro fault, an active sinistral fault that cuts through Sulawesi Island, was the cause of the earthquake and liquefaction disaster in Palu and Sigi Regency in 2018. A series of studies related to liquefaction have been carried out since then but more focused on the west side of the Palu River. This research will raise the potential for liquefaction on the eastern side of the Palu river, precisely in the sabo dam area at Poi and Bangga River. These rivers are located on the opposite side of the Sibalaya liquefaction area. Liquefaction potential was calculated using the Simplified Procedure Method based on NSPT values. Fifteen and twelve boreholes are located at Bangga and Poi rivers, respectively. The qualitative analysis assessed the criteria of vulnerability based on geological factors, groundwater levels, and seismicity. The Liquefaction Potential Index method was used and calculated using several earthquake scenarios based on historical data and potential earthquakes of The Palu-koro fault. Based on LPI analysis, the Poi River has meager potential at the middle stream area and moderate level potential at the downstream. Bangga River has moderate to high liquefaction potential downstream and low to very low potential at the middle stream.

In the medium to high seismic zone, prestressed hollow concrete (PHC) pile for structural foundation should be designed with elastic behavior due to low ductility and dissipated energy. However, some Indonesian practical engineer has chosen PHC pile for pile-supported slab viaduct (PSSV) with medium seismic moment-resisting frame concept in a high-risk earthquake zone. Therefore, some nonlinear numerical simulations of PSSV structure in medium to high seismic zone need to be conducted to investigate its seismic performance. In the initial stage, a numerical model for investigating the seismic performance of PHC pile under flexural test was conducted. By implementing an appropriate plastic hinge length of forced beam-column with hinge elements, the flexural behavior of PHC piles to be simulated under both monotonic and cyclic loading. The fiber section was adopted to accommodate non-linear behaviour of material in the PHC pile cross section. As the results, the skeleton curves, the sectional strain distributions, and the hysteresis curves have good agreement results compared with the experimental results. Furthermore, based on the equal damping ratio calculation of the hysteresis curve, the PHC pile only achieve low energy dissipation, though the ductility capacity around 3. Finally, this numerical model approach could be adopted in the non-linear simulation of PSSV structure under seismic load.

Soft and expansive clay is a soil type mostly found in Indonesia. Cement addition is one of the treatments common applied in soft clay improvement. However, its utilization requires to be controlled considering the effect to environment. Bamboo is a very abundant natural resource. On the other hand, bamboo leaf still requires attention in terms of management and utilization. In the form of ash, bamboo leaf contains high silica that could be used as pozzolan material. This research investigated the effect BLAsh addition in reducing cement utilization to the CBR value parameter of soft clay soil by experimental analysis. The total content of stabilizer material in the soft clay soil is 12% of the dry soil mass. Then, BLAsh content was varied in 0%, 25%, 50%, 75%, and 100% of the total content of stabilizer material. The result depicted that 25% of cement substitution by BLAsh proved the improvement of CBR value both in dry and critical condition. In addition, improvement of expansive soil was proven by the decreasing of swelling percentage in the mixture with 25% of BLAsh content. Also, the longer curing time is important in providing perfect reaction of the chemical contents in the mixture.

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