CONSTRUCTION TECHNOLOGY AND QUALITY CONTROL OFSHAPAI RCC ARCH DAM

摘要

Shapai Dam used to be the world’s highest full-section RCC arch dam, with a height of 130 m,rnand the basis of “ Study of RCC High Dam Construction Technology”, a state task-force research projectsrnduring the “9th Five-year Plan Period”. The dam is raised continuously by full-face thin layers, with RCCrnconcrete mixed in new-type forced mixers with a mixing time of 12s only. The average C3A content ofrncement incorporated into the dam is 4.7%, and C4AF content 18.8%. The high-iron and low-aluminumrnformula produces cement of low fragility and high crack resistance, and in turn RCC of high tensilernstrength and low elasticity modulus, with an average ultimate tension of 1.36x10-4, modulus ofrncompression 16.65GPa, and modulus of elasticity in tension 20.12GPa. According to the equation based onrnthe findings of state task-force researches during the “9th Five-year Plan Period”, as retrieved from outletrntest results, Grade 2 RCC used to the project has a 90d crack resistance of 1.08, and Grade 3 has 1.06.rnAccording to calculations of core test results, Grade 3 has a crack resistance of 1.65, while ordinaryrnconcrete has a value of 0.4-0.6, I.e. a difference of 100% approximately. Thus, this dam has never shownrnany crack after having experienced cold winters and hot summer in despite of poor insulation andrnprotection measures (due to financial reasons), which is undoubtedly related to the crack resistance of RCCrnper se. On the other hand, a lot of techniques are employed during construction, such as repeated groutingrnof reduced joint, vertical transport via vacuum chute, wider use of modified concrete, and application ofrnloaded/unloaded consolidation (contact) grouting. Due to the particularity of weather conditions and therncomplexity of raw materials, a project-specific quality control process is deliberated in the process ofrnconstruction. The RCC cores taken out of the completed embankment is 13.2 m long to the maximum,rnsmooth in surface, even in aggregate distribution and good in layer contact. Core test results indicate thatrnall performance indexes meet the design requirements, suggesting excellent quality of construction.