Transforming Challenges into Solutions with Diaphragm Walls
Zilker Point, a remarkable architectural project located in Austin, Texas, boasts not only a 7-story above-grade office building but also a 5-story below-grade parking garage. The construction of the below-grade parking garage presented unique challenges that required innovative solutions. Malcolm Drilling undertook the design of the entire Support of Excavation (SOE).
Malcolm constructed a 59-foot-deep excavation to ensure the structure’s stability and longevity and selected a robust diaphragm wall system to shore this deep excavation, involving the installation of approximately 60,000 square feet.
The soil conditions at the construction site posed significant obstacles. The presence of a high groundwater table coupled with gravelly sands underlain by limestone bedrock demanded careful consideration of several shoring options. The diaphragm wall emerged as the ideal solution, offering a multi-functional approach to address the soil complexities.
The structural wall, with a thickness of 30 inches, served as a pivotal element in the construction process. Firstly, it acted as a full groundwater cut-off wall, effectively mitigating the challenges posed by the high-water table. Secondly, it facilitated the mass excavation required for the below-grade parking garage. Lastly, the diaphragm wall served a dual purpose by becoming the permanent basement walls of the structure. This not only enhanced the overall stability of the garage but also optimized space utilization.
Alongside the diaphragm wall, a comprehensive excavation support system was implemented to ensure the safety and integrity of the construction process. The system incorporated 5 rows of temporary tie-backs. These tie-backs provided crucial reinforcement to the diaphragm wall, lending it additional strength and stability. Moreover, to bolster the structure further, approximately 250,000 pounds of temporary steel corner bracing and 1,100 square feet of temporary soil nails and shotcrete were employed.
