Abstract:
The Peregrine Slide Project and the Westport Slide Complex are both large soldier pile ground anchor wall projects under construction in Mendocino County in Northern California. Peregrine Slide is a 423 feet long wall with 7 rows of ground anchors and a max ground anchor length of 230 feet. The Westport Slide Complex consists of two separate walls that each have a length close to 500 feet. The max factored test load on the Westport project is 300 kips. Some of the constructability issues that have been encountered with ground anchor installation on these large walls include the following:
i. Ground anchor interference when drilling adjacent ground anchors and horizontal drains
ii. Ground anchor elongations come close to failing 80-percent criterion
iii. Larger diameter holes have been required to accommodate increased factored test loads
Some of the mitigation measures taken to avoid these issues are as follows:
i. Increased care taken when setting angle of drill steel ii. Increased pile spacing
iii. Ground anchor inclination angle increased to 20 degrees. This allows for easier ground anchor installation and reduces friction loss
iv. Anchor spacing adjusted to keep factored test load under approximately 300 kips depending on soil type
Soldier pile ground anchor retaining wall systems are becoming increasingly large and complex as we try to combat large scale slides that occur on our state highway system. Construction issues are revealing themselves in real-time. Through partnering with the construction industry and providing feedback to designers we can improve our construction practices and produce better wall designs.