When geostructures are designed poorly, projects invariably get delayed and expenses mount. That’s why it’s critical to carefully plan out these auxiliary site structures early in the design process.
Geostructures are structures that rely symbiotically on the earth to maintain their form and function. Large geostructures, such as those used for excavation support or slope stability, are typically considered early in the design process. But all too often, smaller site structures such as retaining walls, weir walls, bioretention tanks, aggregate piles, or foundations for pre-manufactured structures are overlooked until the permit or construction phases. These smaller structures are usually laid out by the civil engineer, but their structural design tends to be an afterthought.
When this happens, builders scramble to hire an engineer just as the design phase is wrapping up. The engineering design gets rushed, and the engineer no longer has the capacity to plan out an optimal structure.
One real-world example: A civil engineer recently designed bio retention tanks for a popular chain of standalone restaurants. The civil drawing showed the wall layout with wall heights and a generic wall section detail. However, the walls actually required a custom engineered design which considered their heights, property line restrictions, and the heavy traffic load behind the walls. The base building was permitted and construction underway before an engineer was engaged to design the tank walls. The resulting walls required an additional permitting review which delayed construction, and if kept as intended, would require deep and expensive keys to prevent sliding. Fortunately, simple design changes such as the inclusion of grade beams eliminated the construction costs of installing a key. Earlier involvement with the geostructural engineer may have incorporated these changes more seamlessly and allowed for the walls to be permitted with the building, reducing delays.
Similar delays occurred on a transportation center in which the site walls were placed such that they would load the deeper garage foundation walls. If there was an opportunity to incorporate easy changes, construction costs could have been significantly reduced. Open and frequent communication early in the project between the civil, site wall engineer, and garage engineer can catch conflicts like these during the schematic design phase.