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Improving the work instructions of emergency measures against piping

Castelijns, M. (2018) Improving the work instructions of emergency measures against piping.

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Abstract:Almost 60% of the Netherlands is at risk of flooding due to high water or extreme weather and almost 3800 kilometres of levees are in place to protect against this. These levees can fail due to different failure mechanisms, and piping is one of the most important ones. Piping can occur during high water; due to the water head difference water can start to flow underneath the levee. This flow of water can result in particle transport and if this is not stopped eventually a pipe can form and finally the levee can fail. Several emergency measures are possible to combat piping, three of which will be discussed in this research: the creation of an impoundment, raising the water level in the ditch behind a levee, and the construction of a filter. Whether these emergency measures are effective or not is dependent on three aspects: the detection of a failure, the design of the emergency measure and the implementation of the measure. If the detection is done timely, the correct emergency measures is chosen and designed, and this measure is implemented correctly and stops the sand transport, the emergency measure is deemed effective. Currently there is no method to determine the effectiveness of an emergency measure and to determine the effect they have on the safety of levees. However, some water boards have indicated that the presence of work instructions during the implementation positively affect the quality of the emergency measure. Not all water boards use work instructions and the work instructions that are used are not uniform. This research’s objective is to give recommendations for the adjustment of the work instructions for the three emergency measures. This research will also try to give an indication of the effect the adjustments have on the effectiveness of the three emergency measures. The research goal is defined as: To assess, evaluate, and improve the work instructions for the implementation phase of the three emergency measures against piping. The process surrounding the implementation of an emergency measure is divided into three phases: detection, design, and implementation. These three phases are affected by many different factors which can be placed into two categories: factors that can be influenced by the water boards and factors that cannot be influenced. The work instructions must include information on how to deal with all these factors. The work instructions need to support decisions concerning the design and the implementation of emergency measures. They must be user friendly and help the executing party (a contractor, the waterboards, or a combination of the two) to construct the measure quickly and safely and to minimize the probability of failure of the emergency measure. Currently the existing work instructions only give an indication on the needed materials and address some of the factors that can be influenced, but they lack in some areas. They also address the steps that need to be taken to construct an impoundment and a filter construction, but the steps necessary for raising the water level are not stated. The instructions also do not mention the non-influenceable factors and how to deal with them. To make the work instructions more complete, data is gathered in three different instances: observations at WDOD during the training exercise Deining en Doorbraak, interviews with contractors from two different water boards, and a workshop conducted with experts from six different water boards and calamiteitenteam waterkeringen (CTW). Based on the gathered information, and the information gaps in the current work instructions, recommendations are made to adjust the work instructions. The indication of the needed materials should be adjusted to comply with the minimum standards found in the literature. Other additions that must be made to the work instructions are: a quality check for the used materials, a checklist for the mobilisation, a division of tasks for the construction, clear instructions how to handle sandbags, the addition of an additional step for the construction of an impoundment and a filter, all the necessary steps to construct a dam to raise the water level in the ditch behind a levee, and an overview of the biggest risks during construction for each of these emergency measures. The step that must be added to the work instructions of the impoundment and filter construction is the removal of excess sand surrounding the damage. The implementation phase can be separated into two sub-phases: the mobilisation and the construction. Both these sub-phases will have a probability of failure of about 1e-3 when the adjustments are implemented. The adjustments comply with the method to mitigate the probability of human error stated in the literature (the procedures are well organized and documented and not excessively complex, and training for normal and abnormal conditions). This probability of failure is based on the human performance in the implementation phase. There are also factors that do not dependent on human actions, however, there is no method to determine how much effect they have on the probability of failure of the emergency measures available at the moment. Another method to reduce the probability of failure of the implementation phase is to train the mobilisation sub-phase more realistically. At the moment the mobilisation, as it would be in real high water situations, is not a part of the current training exercises. By including the mobilisation it will become a more routine task and therefore the probability of failure could be lower. It is also important that the lessons learnt from training exercises are continuously being used to improve the entire process. Mistakes that are made during exercises must be documented and communicated to the participants in order to learn form them and prevent them from happening in other training exercises. The water boards would like the work instructions to be more uniform between all water boards. To reach that goal three steps have to be taken. First of all, the presented adjustments should be included in the work instructions. Secondly, members from different water boards should discuss these work instructions to see if there are still shortcomings to them. Thirdly, if everybody is satisfied they should be tested during training exercises at different water boards. If step two and three are completed successfully the work instructions can be distributed, if further changes have to be made the steps have gone through again.
Item Type:Essay (Master)
Clients:
Wiki Noodmaatregelen
Deltares
Drents Overijsselse Delta
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering and Management MSc (60026)
Link to this item:http://purl.utwente.nl/essays/76201
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