COMPARISON OF REPAIR METHODS FOR CRACKED EARTH DAMS BASED ON DIFFERENT TECTONIC EARTHQUAKE EFFECTS
President, Institute of Mitigation for Earthquake Shear Banding Disasters
Professor, Department of Civil Engineering, Feng-Chia University, Taiwan R.O.C.
Student, Ph.D. Program for Civil Engineering, Water Resources Engineering, and
Infrastructure Planning, Feng-Chia University, Taiwan, R.O.C.
Zong-Lin Wu, Shey-En Chiu, Po-Liang Lin, Jia-De Lai
Directors, Institute of Mitigation for Earthquake Shear Banding Disasters,
Assistant Professor, Feng-Chia University, Respectively, Taiwan, R.O.C.
The Hutoupi Earth Dam is the first dam built in Taiwan. Since the dam was completed in 1863, it has suffered from cracks and piping failures from numerous tectonic earthquakes. After damage to the dam, the reservoir management agency immediately repaired it. However, as the seismic design only fortified the dam against the secondary ground vibration effect of tectonic earthquakes and ignored the primary shear banding effect, the problem of cracking or piping failure continued to occur after the repairs were completed. Therefore, in this study, two different cracking mechanisms are proposed for earth dams: ground vibrations and shear banding. The performance of the repair methods is then compared based on these two cracking mechanisms. Three findings are drawn from the results. (1) When the engineering design for the repair is based on the ground vibration cracking mechanism, only a limited crack extension and depth can be repaired; therefore, the shear bands and shear textures in the deeper sections of the earth dam are ignored, causing cracking problems that cannot be resolved completely. (2) When the engineering design of the repair is based on the shear band extension mechanism, an appropriate extension range and depth for the shear bands can be selected after weighing safety and costs. Designing for these ranges can effectively suppress the occurrence of cracks. (3) Restoration projects must choose backfill materials that have low permeability and are resistant to shear banding and ground vibration. By implementing comprehensive quality management methods, the compacted soil can perform according to its functional needs. Based on these three findings, it is recommended that the shear banding effect be included in the seismic design code for earth dams to prevent cracks and piping failure in the earth dams and thus perform according to the design goals.
Keywords: tectonic earthquakes, shear banding, ground vibrations, cracking, piping failure.