THE ROLE OF GEOTEXTILE TUBE AS LOW-CRESTED BREAKWATERS IN RESTORING SEVERE BEACH EROSION PROBLEM AT PEBUAHAN BEACH IN BALI ISLAND

Pebuahan Beach in Jembrana Regency, Bali has experienced severe beach erosion since the construction of the Nusantara Pengambengan fishing port, 10 km east of Pebuahan. Efforts to countermeasure the coastal problem has been carried out by many local residents, but failed due to strong longshore drift. Through a collaboration between the Research Center for Water Resources, the Bali Penida River Basin, and PT. Geotechnical Systemindo, the implementation of low-crested breakwaters (LCB) or PEGAR, made of Woven Geotextile Tubes was initiated. Four woven geotextile tubes C12.9 m with length varied from 20 m to 25 m were installed to form LCB with the length of 60 m, at distance to the coast of 50 m. The monitoring of shoreline changes was conducted over the 3 months after its installation, which shows the formation of a new shoreline with the amount of deposited sand of 185.8 m3. The breaking wave on LCB crest results in successfully controlling the longshore current, hence the longshore drift settles behind the LCB to form a new coastline. It is expected this field study can be treated as an additional input to improve LCB Guideline and to expand LCB effectiveness scope not only apply to shallow wave conditions and beaches such as on North coast of Java, but also can be applied more universally to a deeper coastal waters with high wave conditions.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/AFzvkvYY2Do

GEOTEXTILE TUBE REVETMENT WITH TETRAPODS IN MAYU ISLAND, MYANMAR

Mayu Island (formerly known as Oyster Island) is a very small island of 7,284 squared-meter located off the north-western coast of Myanmar, Bay of Bengal. In mid-April 2006, Cyclone Mala had caused partial damages to the stone revetment. Over the years, the raft foundation of the lighthouse was badly affected and starting to give way. In addition, the safety of the Navy personnel stationed on the island is a major concern as well. Therefore, rectification works has to be carried out to protect the island from total destruction. This paper presents the proven viability of integrating geotextiles tubes into a rock revetment facing harsh weather conditions from the open sea, and the fastest method of filling up geotextile tubes.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/fsTsdqbVAc4

Geotextile Tube Dewatering Performance Assessment: An Experimental Study of Sludge Dewatering Generated at a Water Treatment Plant

Using geotextile tubes as dewatering technology may significantly contribute to sustainable treatment of sludge generated in different industries, such as the water industry. This is an economical alternative for dewatering sludge from a Water Treatment Plant (WTP), which prevents sludge from being directly deposited in water bodies and makes it possible to then transfer the sludge to landfills. This paper presents a laboratory study and a statistical analysis, carried out to evaluate the geotextile tube dewatering of sludge from a WTP, discussing the relation between the independent variables (initial Total Solids (TS) of the sludge and polymer dosing) and dependent variables (performance indices used in the literature) evaluated using semi-performance tests. Sludge from a WTP and three different types of geotextiles bags were used. Changes in the geotextiles’ characteristics after dewatering were also evaluated, quantitatively using permittivity tests and qualitatively by Scanning Electron Microscopy (SEM). The results indicated turbidity of effluent that met the Brazilian regulations for the discharge of effluents into Class 2 water bodies, as well as higher percent-solids than those obtained with mechanical dewatering technologies. This study underscores the importance of semi-performance tests to understand dewatering in geotextile tubes.

Semiempirical Model for Assessing Dewatering Process by Flocculation of Dredged Sludge in an Artificial Reservoir

Understanding sedimentation behaviour of clay material is crucial in planning project for sediment removal from bottom of a reservoir. The sedimentation of samples taken from Occhito reservoir ( Italy) is investigated. Samples containing and not containing polyacrylamide have been monitored. Results reveal that polymer induces bridging flocculation and the particle-size distribution tends to become uniform. The sedimentation profiles follow a mater curve. Such experimental observation is used to develop a semi-empirical model for assessment of dewatering process by flocculation of dredged sludge in artificial reservoir. A two-step stage model for assessing the volume of solids in a geotextile tube is suggested. Such model is based on the idea that for very long dewatering times solids reach the configuration of free sedimentation.