To facilitate the design of seismic remediation for Tuttle Creek Dam in east central Kansas, a seismic finite difference analysis of the dam was performed using the software FLAC and the UBCSAND and UBCTOT soil constitutive models. The FLAC software has a key advantage because it can use calibrated site-specific constitutive models. Earlier deformation analyses using a hyperbolic constitutive model for the foundation fine-grained materials did not properly represent the modulus and strength reduction and predicted extremely large permanent deformations. Cyclic triaxial laboratory tests using high-quality samples and in situ vane shear tests were used to calibrate the FLAC constitutive model herein. The resulting FLAC analysis of the unremediated dam predicted an upstream slope toe deformation of about 0.6 m, a crest settlement of about 0.6 m, and a downstream slope toe deformation of about 1.5 m using the design ground motion. Based on the estimated permanent deformations and other factors, it was decided that the anticipated upstream slope and crest deformations were tolerable and only the downstream slope had to be remediated to protect the downstream seepage control system.

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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%.