Lauritzen Gardens Stone Gate Stabilization
Challenge
Lauritzen Gardens is one of the most recognized botanical gardens and horticultural conservation sites in the United States. It is a tourist attraction and a place that thousands of people visit each and every year. Among the 100-plus-acre facility, one area is dedicated to the display of a replica Japanese garden – including a large stone gate that was donated by the local Japanese community. Over time, the stone-gated entrance to this area of the gardens had settled due to softening soil. At the request of the gate's donors, the project engineer, Lamp, Rynearson & Associates (Lamp Rynearson), chose Thrasher to assist with lifting and leveling this imposing structure that had settled over one-half inch. Lamp, Rynearson & Associates, the project engineer, and Thrasher had partnered together on previous projects. All parties involved were confident that Thrasher could create the end results the donors wanted with the project. The repair work also needed to be completed in time for the garden's 10-year anniversary celebration. It was essential to the donors and Lamp, Rynearson, and Associates that the stone gate was repaired and returned to its original condition. And, the gate does not experience any additional damage due to the repair.
Solution
Thrasher was able to schedule the project quickly to ensure that it would be completed in time for the 10th-anniversary celebration. After Thrasher was finished with their portion of the project, additional work was needed to complete the project before the celebration. As a result, Thrasher wanted to mobilize quickly and keep their portion of the project on time to complete the entire project. Thrasher and the project engineer worked together to design the appropriate solution for the project.
To permanently halt the large stone gate's settling, Thrasher used retrofit helical piers to stabilize the gate's foundation. Using soil composition data provided by Lamp Rynearson, the Thrasher team determined that a total of six (6) Model 288 piers with an 8"-10" helix plate configuration would need to be installed to a depth of approximately 50 feet to find competent bearing soils. Since the soil itself was the issue and was unable to provide the support the stone gate it needed, a soil boring was done to determine the depth the helical pier needed to be advanced to find competent soil. The helical pier would then ensure the stone gate was stabilized and would no longer experience any additional settlement.
Helical piers were the perfect solution to provide the lift and the stabilization that the stone gate needed. They would not put extensive pressure on the stone gate so Thrasher could prevent causing additional damage to the stone gate. Not only was it essential to advance the helical pier to an appropriate depth to support the stone gate, the project engineer, Thrasher and the Supportworks engineering team needed to determine the proper design working load to ensure the stone gate was supported correctly. By reviewing the stone gate's construction plans, it was determined that the stone gate itself was 14,900 pounds and had a concrete foundation that weighed an additional 103,500 pounds. The foundation itself was 23 feet by 10 feet by 3 feet. With input from the Supportworks engineering team, it was determined that a design working load of 25 kips per pier would protect the gate foundation against future settlement.
The project team leader reviewed the project with the project engineer, the donors, and Lamp Rynearson to ensure everyone was on the same page, and the desired outcomes would be achieved. By installing helical piers, the gate was successfully stabilized and re-leveled back to its original condition. The project was a success and completed on time and within budget. As a result, the entire project was completed well before the 10th-anniversary celebration.
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