Studies On Cemented Sand And Gravel Dam Material And Its Application

Two main popular dam types in the world are embankment dams (including Rock-Fill Dams) and Concrete Dams (including Roller Compacted Concrete Dams), and Cemented Sand and Gravel (CSG) Dams are the transitional dams between the two. CSG materials are produced by mixing sand, gravels and a few cementitious materials and placing, vibration and compacting, will gain compressive and shearing strengths. The K.I.S.(Keep It Simple) concept for building dams aims to simplicity and economy. The design philosophy of CSG dam is to make full use of on-site materials and to make use of fast and convenient construction method. So there is a lot of work to be done to make sure of their safety when building CSG dams in China.Supported by the Water Ministry of China, the mixing design method for CSG dam, the mechanical properties and durability of full-grade CSG specimens especially the leaching mechanisms of CSG materials under long-term water pressure, which are core contents for compiling Cemented Materials Dam Technology Guide, are investigated in this thesis. The main achievements and findings are as follows,1) A CSG mixing design method is proposed and improved. A CSG mixing design method needs the strength of CSG with the finest and average grade sand and gravel to meet two different targets, considering the guaranteed rate and standard deviation of strength.The Fuller similarity coefficient is proposed, which can be used as a tool to evaluate the scattering degree for hardened CSG strength from the scattering degree of the grading of on-site sands and gravels.2) Effects of mixing parameters on CSG strength are studied and an appropriate range of mixing parameters, such as water/cementitious materials ratio, cement content, fly ash content, sand ratio and mud content for CSG dams are recommended. The experimental results show that CSG strength decrease significantly with the sand ratio greater than30%and water/cement ratio is still the predominant factor for CSG strength. Moreover, the mud content in sand has less impact on CSG strength if it is below28%.3) A thorough investigation on the CSG mechanical properties are made. The differences and relationship between the mechanical properties of large-size full-grade CSG specimens (the maximum size of aggregates is150mm) and small-size specimens are studied. Results show that CSG strength of cubic specimens with side length450mm is around83%of specimens with side length of150mm. The creep, autogeneous deformation, abrasion resistance and shearing strength are also studied and results show that the abrasion resistance is satisfactory and it won’t be washed way with water flowing above.4) The properties and mechanism of leaching dissolution, air-frost resistance as well as water-frost resistance of large-size full-grade CSG materials are well studied. Results show that the leaching of Ca2+almost stagnated after1.5years of water pressure. The testing method of air-frost is different from the Japanese. Results also show that CSG has a high air-frost resistance, and is reliable if placed in the dam body above the water level.5) Application of CSG in Shoukoubao Project in Shanxi Province. The mixing parameters for Shoukoubao CSG Project are accepted and applied in the construction which will soon be started and grout-enriched vibrated CSG and paste-rich CSG materials are developed to be used as protection materials in the project.6) Results also show that the elastic wave velocity has a high exponential correlation with CSG strength indicating that the elastic wave method could be developed as an on-site inspecting method for CSG dam.