Samenvatting

In 2006 a mud volcano erupted in Sidoarjo, a town south of East Java’s industrial hub, Surabaya. The volcano has continued to produce mud until the present day (2016) resulting in a mud depot of over 500 hectares. The mud has caused damage to the people living in the area and continues to bring destruction as it is not expected to stop within the coming years. This research thesis is on the post disaster management of the mud volcano, specifically the dike surrounding the depot. The mud depot is at its full capacity and that has resulted in an unstable dike. Flooding occurs outside the depot affecting important infrastructure and all mud is currently pumped away to the Porong river.
The objective of the research was to determine what hydraulic failures are present in the dike retaining the mud and design a solution to prevent these failures from occurring. The solution should improve ecological conditions by accommodating the mud so that pumping of mud to the Porong river is no longer necessary.
Currently the mud outflow from the mud volcano is 10 000m³ and is comprised of hot water (70%) and fine sediment (30%). The outflow is expected to last for the next 26 years and the new solution therefore has a design life of 50 years. The geological conditions of the existing dike include underlying layers of clay and sand and the dike was constructed with pebbly-sandy soil.
The solution was designed in two phases where different failure mechanisms were analysed. The settlement, macro-stability and slip circle of the solution was analysed globally. The overflow, erosion of the outer slope and piping were analysed in detail. The requirements for the dike were based on Indonesian design standards and where these were not available were based on Dutch design standards. These requirements are stated in a functional and technical program of requirements as a result of the research.
Once the requirements were defined an alternative analysis was done on three solutions to accommodate the mud. The first was to create a depot within the current depot at the location were dredging is taking place. The mud would be separated into water and sediment with the water pumped away to the Porong river. The second solution was to create a new depot next to the existing one and to pump the mud there instead of to the river. After analysing the three solutions however the third solution was found to be the most viable.
The third (chosen) solution is a combination of the first two. It is a new depot next to the existing one which will act as a buffer zone where the sediment and water are separated. The sediment will be stored in the buffer zone and the water will be pumped away to the Porong river. This solution is able to accommodate the mud for required 26 years and has possibilities for testing and expansion.
The final design of the new solution determines the overflow and piping risk of the existing dike as well as the new dike design. The outcome is that the existing dike should be heightened to include a pipe through the dike to accommodate for overflow and a piping berm for piping risk. This in combination with the new design will reduce the risk of hydraulic failure in the existing situation.
The outcome of the research is based on limited information and the analyse done should be implemented for each cross section of the existing dike. The recommendation for further research and design of the separation of the mud is given if the chosen solution is to be realised. If the solution is not realised options to reduce the risk of hydraulic failure are provided for the existing dike.