岩土工程监测
Castillo de San Marcos National Monument, St. Augustine,Florida. Taken in 1995, this view looks across the moattoward the southwest bastion, where several major cracks arevisible.
The Castillo de San Marcos National Monument, St. Augustine,Florida, is a17th Century historic, cultural, structural, and civilengineering landmark. The Park Superintendent, Gordie Wilson,together with the Southeast Region of the National Park Service,has commenced a long-range monitoring effort at the fort. Thegoal is to better understand the causes of movement—and theresulting cracks—that have plagued areas of the fort walls for twohundred years.
岩土工程监测
The fort’s bastions are earthen-filled, masonry ramparts,constructed on shallow foundations. Two of the four bastionshave evidenced cracks since the early 1800s. The fort’sfoundations ought to be structurally sound according to anextensive investigation of both the foundations and the soilbearing capacity. An emerging theory postulates that the wallconstruction is near its structural limit in retaining the earthfill. Rainwater infiltration may increase the internal loadon the walls, causing the structure to move. A design teamwas formed to investigate this theory. Headed by architects GrievesWorrall Wright & O’Hatnick, the team proposed that the parkmonitor:
•existing cracks in three-dimensions
•tilt of the large segments between the major cracks
•change of soil moisture within the bastion at two levels, onenear the surface and one 16 feet deep
•weather conditions at the site to assess their impact ongeotechnical activity
岩土工程监测
Sensors are installed across a crack in the south west bastion.
Monitoring equipment was assembled from several vendors.Campbell Scientific provided the datalogger, multiplexers, weatherstations, and soil moisture probes. The equipment was integratedwith crack and tilt sensors manufactured and installed by Geokon(Lebanon, NH). AMJ Equipment(Lakeland, FL) and PSIEngineering (Jacksonville, FL)provided technical and installationassistance. To reduce the installation’s aesthetic impact onthe park, cables were concealed in custom conduit with the help ofthe park’s maintenance staff.
The sensors are measured and the data are stored by the CR10Xat5 a.m. and 5 p.m. On a quarterly basis, the data stored intheCR10X is downloaded via phone modem to computers located in theoffices of the engineers and architects for analysis andinterpretation. The project is scheduled to collect data forfive to ten years.