Matthew C. Pierson

Laterally Loaded Shaft Group Capacities and Deflections behind an MSE Wall

Design of laterally loaded cast-in-place shafts that pass through the reinforcement behind a mechanically stabilized earth (MSE) wall often requires isolation of the shafts from the MSE mass and socketing of the shafts into the underlying stable foundation material, such as bedrock. Sizeable cost and time savings could be realized, while maintaining stability if the shaft could be supported by the MSE mass alone with no rock socket. Construction, instrumentation, and testing of multiple 0.9-m-diameter shafts solely supported by the geogrid-reinforced mass behind a 6-m-high MSE block wall were conducted for the Kansas Department of Transportation (KDOT). This paper describes the design, construction, and instrumentation of the wall and shafts and the results from the lateral load tests of three shafts tested together as a group compared with shafts that were tested individually. This testing protocol was adopted to evaluate the shaft group effect and the effect of shaft distance from the back of the wall f...

Lateral Load Capacity of Cast-in-Place Shafts behind an MSE Wall

Current practice for designing laterally loaded cast-in-place shafts that pass through an MSE Wall involves isolating the shafts from the MSE mass and anchoring the shafts into the underlying foundation material. Sizeable cost and time savings could be realized, while still maintaining stability and reliability, if a method were available to evaluate the lateral load capacity of a shaft that is supported by the MSE mass alone with no rock socket. Construction, instrumentation, and testing of multiple 0.9m (36in.) diameter shafts solely supported by a 6m (20 ft) MSE block wall was conducted for the Kansas Department of Transportation (KDOT). This paper describes the design and construction of the wall and shafts, and the results from the lateral load tests of two of the shafts. These shafts had lengths that were equal to the full height of the wall and 75 percent of the full height of the wall to evaluate the reduction in capacity if shorter foundation elements suspended in the MSE mass were used. Results for both load and deflection of the shafts and the relative deflections of the shafts and wall facing during loading are presented.

Lateral Resistance of Short Rock Sockets in Weak Rock: Case History

The results from full-scale cyclic and repeated lateral load testing of two short rock sockets in weak rock and the recommendations developed for p-y analysis using those results are presented. Two drilled shafts were constructed in rock sockets 42 in. in diameter to depths of approximately 7 ft in limestone in Wyandotte County, Kansas. The shafts were loaded laterally during three tests. The shafts were tested under cyclic loading (load reversal) for loads up to 400 kips, repeated loading in one direction up to 820 kips, and to failure near 1,000 kips. Test data showed that socket behavior was essentially elastic during cyclic loading for loads of 400 kips (40% of nominal resistance) and lower. The shafts experienced permanent, accumulating deformations during repeated loading to 610 and 820 kips. Modeling of the results showed that the lateral load behavior could be effectively modeled in LPILE with the Reese weak-rock model included with LPILE software. Recommendations for use in modeling are presented.