The Analysis of Retaining Wall Strengthening on Small Reservoir at Pilangbango Madiun as an Alternative of Existing Design

Abstract

In 2016 the government of Madiun city carried out the construction of the reservoir in Pilangbango village, Kartoharjo sub-district, Madiun, East Java. The reservoir construction work has been carried out according to the schedule, however, several wall collapse and land subsidence have arisen. To date, the condition of the Pilangbango reservoir is still damaged. The government of Madiun is planning to repair the reservoir. The analysis carried out on the retaining wall of the reservoir uses Plaxis program method to calculate the energy that occurs. The results of the analysis on the existing design using cantilever walls showed a collapse due to poor soil types and did not meet the safety requirements for rolling, sliding, and uplift with a value of 1 < 1,2 (safety factor permit). The strengthening alternative of soil retaining wall on Pilangbango reservoir is to use sheet pile and soldier pile. The result of the analysis of sheet pile walls with size W-600 with a depth of 15 m, shows that the strengthening can be applied in the field. The sheet piles that are used, meets the security requirements for rolling, sliding and uplift of 1,2 (safety factor permit) < 2,15, and the bending moment that occurs, can be held by the wall with a value of 132,98 kN.m (Bending Moment) < 506 kN.m (Moment Crack). The strengthening analysis of soldier pile with a size of 60 cm, longitudinal reinforced 10 D19, spiral reinforced Ø12-60 also applied to 12 m, shows that the reinforcement can be applied as a reservoir wall. The results obtained from the analysis show that the soldier pile meets the safety factor for rolling, sliding, and uplift 1,2 (safety factor permit) < 1,74, and the ultimate moment that occurs, can be held by the wall with a value of 169,91 kN.m (Moment Ultimate) < 369,6 kN.m (Moment Nominal).