Book Description

"Mechanically stabilized earth (MSE) walls are an inexpensive and aesthetically attractive means of retaining soil. While the design principles for MSE structures have been accepted for several decades, space restrictions at MSE wall sites have led to new demands on MSE wall structures to support laterally loaded deep foundation elements constructed within the reinforced mass. Current design procedures for such configurations are by necessity based on very conservative design assumptions due to the lack of test data. This report contains estimates of the capacity of concrete columns, commonly referred to as drilled shafts, constructed behind the facing of a mechanically stabilized earth wall within the reinforced mass. This is the first of two reports on this topic and contains design capacity recommendations for 36 inch diameter shafts constructed behind an MSE wall with a height of 20 feet based on full scale field testing. It also contains recommendations for P-Y curve analyses for similar wall-shaft configurations. These recommendations and a discussion of their development were prepared by Dan Brown and Associates and are presented in Appendix B. The second report will contain capacity recommendations for walls and shafts with a range of heights and diameters based on computer models calibrated with the field data reported herein. A 20 foot tall, 140 foot long MSE block wall was built in accordance with AASHTO and KDOT specifications using the Mesa system developed by Tensar International. The wall supported eight 36 inch diameter vertical shafts constructed at four different distances from the back of the facing to the center of the shaft. These shafts were then loaded toward the wall facing using a displacement control method. The shafts and wall were monitored using multiple methods as each shaft was loaded to failure. Shafts were determined to have substantial lateral capacity, with capacity and width of shaft influence increasing as the distance of the shaft from the wall increased. The wall facing was very effective at concealing large deformations. Cracks appeared at the back of the reinforcement, suggesting that additional capacity may be achieved by lengthening the reinforcement. Recommendations for design lateral shaft capacities based on ultimate shaft load and on allowable deformations are presented in Chapter Five of this report"--Technical report documentation page.