Soil Improvement for Seismic Retrofit of Tuttle Creek Dam

Abstract

This paper discusses the seismic retrofit of Tuttle Creek Dam near Manhattan, Kansas. Seismic analyses, construction, and stabilization techniques are presented. Constructability and dam safety issues, along with results of refined seismic deformation analyses, led to cancellation of the jet grouted upstream slope stabilization and cutoff wall. Downstream slope stabilization was to be accomplished by jet grouting or jet-assisted soil mixing, but ultimately was accomplished using self-hardening cement-bentonite slurry to construct transverse shear walls to reinforce the liquefiable foundation sands. A total of 351 transverse shear walls were constructed along the downstream toe by primarily clam shell equipment. Typical shear walls are 13.7 m long, 1.2 m wide, and extend 18.9 m deep or about 6.1 m into the foundation sands. The walls are spaced at 4.3m on center along the downstream toe for a replacement ratio of about 29%.