CFRD Extruded Concrete Curb Construction Technology

There are some disadvantages on traditional construction method of the transition material 2B on upstream face of concrete face rockfill dam, i.e. overtopping, slope-cutting and incline compaction. Extruded concrete curb technology was introduced in 20th Congress ICOLD held in Beijing in year 2000, this method draw more attention for its improving the compaction of transition material, excellent performance of slope protection, and convenient construction.This extruded concrete curb technology was developed in Ita dam construction in Brazil, the Ita method consists of building and extruded concrete curb by using an extruding machine before the construction of a layer of the transition material, then spread and level the transition material in layers inside the curb, and compact the layer by vib'ratory roller horizontally.After the investigation and study of this extruded concrete curb solution overseas, Shaanxi Provincial Bureau of Water & Electric Engineering (Group) Co., Ltd. (SPB) devoted to the research of this new construction method, invented BJY-40 extrusion curb placing machine, made comprehensive experiments on Heihe Dam site, and got valuable results, adopted this method in Gongboxia HPP main dam construction.Based on the productive experiment on Heihe dam site, during April to August 2002, site experiment was made on Gongboxia HPP dam site, BJY-40 extrusion curb placing machine was determined to be applied into Gongboxia Project, the batch ratio is: cement 80kg/m3, sand 651kg/m3, small stone1449kg/m3, and sand ratio 31%, w/c ratio 1.31, admixture 3%. The corresponding 28d concrete indexes are elastic modulus 5000MPa, compressive strength 2.5MPa. The curb concrete meet the predefined requirements of low strength, low elastic modulus and semi-pervious.By adopting the three-dimensional nonlinear finite element program, using Drucker E-B model, demonstrating the actual construction progress and water impounding of Gongboxia HPP main dam, comparing the two schemes of the existence and nonexistence of extruded concrete curb, made three-dimension simulation calculation, the result proved that while the existence of extruded concrete curb between face slab and rockfill, the deformation and stress of face slab are better than that while the nonexistence of extruded concrete curb.Extruded concrete curb construction technology has obvious economic and social benefits, construction quality is improved, progress is speeded up, and river diversion and flood control are much safer.Further research on extruded concrete curb technology should be made. This solution can be widely promoted for general rockfill slope protection in other fields such as railway, highway, river dike etc..