English：

In the reconstruction and expansion project of compact operation substation, facing morecompact space resources and more complex technical conditions, the construction site conditions aroundsome operating equipment or structures are limited, and the civil construction does not have conventionalsupport conditions. The excavation of foundation excavation is very easy to affect the surroundingequipment in operation and existing buildings and structures. Therefore, based on the traditional opencaisson technology, this paper proposes a modified open caisson foundation construction method,which ischanged from the conventional deep foundation design to the shallow foundation design, and its shape canbe flexibly designed as irregular polygon according to the surrounding environmental conditions andsupport needs. In the civil construction support, the characteristics of good foundation integrity, goodstability, large bearing area and large vertical and horizontal loads are used to play the function ofretaining cofferdam and reduce the impact on the surrounding live running equipment and structures.Taking the GIL utility tunnel foundation construction in the reconstruction project of Kangbao Substationin the new energy base of Bashang region in Zhangjiakou City, Hebei Province as an example, this paperintroduces the application of modified open caisson method in substation reconstruction and expansion construction from the perspectives of design, mechanical analysis and engineering implementation.