Safe and Sustainable: DPE Applies Tried-and-Tested Strategies for Building Singapore’s First 230kV Underground Substation

Published on 16 February 2021

DPE is enlisted as the Advanced Works Consultant for Singapore’s first 230kV underground substation, located at Labrador Park Villa Road. In order to work in line with the client’s intent to deliver a robust, safe and yet timely construction, DPE has implemented a peanut-shaped double cell retaining wall system each with a diameter of 95m using diaphragm walls. Combined with the raft foundation it works as both a foundation and a base slab.

Photo courtesy of Pan-United

Due to the complex nature of the project and the need to use materials and equipment that are suitable for the subterranean environment, the development requires specialised engineering capabilities and planning. Analysis and design were conducted using Finite Element Modeling (FEM) software which produced data on both the performance of the structural elements as well as the impact to the surrounding facilities induced by the excavation works. The findings concluded that the peanut-shaped structure is naturally better at withstanding ground lateral forces as opposed to its rectangular-shaped counterparts and therefore able to provide good control of ground movement without the provision of temporary strutting during excavation. This, in turn, promotes big savings in terms of time and cost. During the course of the design work, intensive coordination with all the related stakeholders was also carried out to ensure that the structural provision is adequate so that the underground substation can run its operation as intended.

To further increase the construction speed, DPE’s innovative approach also led to the adoption of the raft foundation instead of a typical pile foundation. The raft foundation concrete mix-design was formulated to include Ground Granulated Blast Slag (GGBS). DPE’s decision of utilising GGBS, an industrial by-product, contributes to sustainability as it repurposes materials that would otherwise contribute to land pollution. Ultimately, these methods contribute to reducing the development’s carbon footprint. As a founding signatory of Singapore’s Construction Declares, this is in accordance with the company continuing commitment to advocating positive and practical measures that can mitigate the impact of the built environment on climate change.

Photo courtesy of Pan-United

The concrete pour, which DPE oversaw, was the largest continuous one completed within a month with the first at 18,916 cubic metres of ready-mix concrete for 57 hours non-stop from 31 October to 2 November 2020 and the second at 18,342 cubic metres of concrete for 42 hours non-stop from 27 to 28 November 2020, to complete the raft foundation. The total concrete volume of the two pours is equivalent to filling 14 Olympic-sized swimming pools, which set a new Singapore record, which surpassed the previous record of 18,000 cubic metres in March 2015 for the Marina One raft foundation.