Page - 511 - in Book of Full Papers - Symposium Hydro Engineering

2.1. DMSI Application at Wonogiri Reservoir Rehabilitation The Wonogiri reservoir has an annual problem of sedimentation with main river (Keduang) mouth discharging within 0.5 km of the main power /irrigation release intake. Nearly continuous dredging has been required to maintain the operation. The solution is to divide the reservoir into two; - a sediment reservoir to trap Keduang River sediments and a clear water reservoir leading to the intake. The division of the reservoir will be accomplished with three closure dikes and one overflow dike acting as an overflow spillway. Two of the closure dikes, will be the conventional embankments which is constructed on relatively hard ground, but the main dike, Closure Dike A, is a 700 m long dike, which will be constructed on soft reservoir deposits, up to 20 m thickness or more. This soft deposit of soil is built up of Keduang River sediments over the years can NOT support the weight of conventional embankment without improving the soil strength. Therefore, deep mixing soil improvement, DMSI, is used. Typical Section of Closure Dike A – Embankment Construction on DMSI Columns Figure 6. Typical Section of Closure Dike A – from Bidding Documents of ICB Civil Works – Construction of Closure Dike and Overflow Dike (Package No. 2-1) 2.2. Stage-1. Installation Working Platform, First Construction Season (15- Aug to Dec 2017) The DMSI equipment including the deep mixing machine and the supporting slurry plant with associated facilities, are heavy and not easily or quickly moved. This becomes a very real problem when the project is being implemented within a reservoir subjected to flash flooding. Therefore, in order to execute the work a working platform is needed that can be made relatively free 511