Structural Design Research On Cemented Sand And Gravel Dam And Engineering Application

As a new dam type, Cemented Sand and Gravel Dam, abbr. for CSG dam, conforms to the dam construction concept, which is to build a dam with cemented material based on better use of local materials. The CSG dam has many advantages, such as safety in overtopping, being economic and environmental friendly, and short construction period. The structural characters of CSG dam include low cemented material usage, larger cross section, low and mean stress distribution, ability to adjust kinds of base, good aseismatic capacity and high overloading capacity.In this thesis, aiming at application requirements, characters of stress and deformation, adaptability to kinds of base, overloading and critical loading capacity, aseismatic capacity and durability of CSG dam are analyzed. Based on this research, principals of CSG dam structural design are proposed, some of which are adopted by the Cemented Materials Dam Technology Guide and applied to the structural design of Shoukoubao project. Main achievements and innovations are abstracted as following:(1) Stress and stability requirements for the design of CSG dam is proposed. By comparing CSG dam design specifications of Japan, Turkey and gravity dam design specification in China, stress and stability requirements for the design of CSG dam is proposed.(2) Analysis method and control index of Finite Element Method Equivalent Stress Method, abbr. for FEMESM, are proposed. Based on the nonlinear and non-even distribution of stress result of FEM, improvements of FEMESM and control index are made and applied to the analysis of CSG dam. FEMESM can reflect the influence of base stiff and holes in dam on stress distribution, which is suitable for the stress analysis of dams with holes. Except for the local stress concentration on dam toe and heel, stress distribution of CSG dam is quite even and low. The concentrated stress can be bore by the protecting concrete slab. The percentage of uplift on the vertical force of CSG dam is smaller than that of concrete gravity dam.(3) Base requirements for CSG dam are proposed. Due to the large cross section and inclined upper stream slop, the anti-sliding ability of CSG dam is enhanced, at the same time, the adaptability to base is enhanced. The suitable stiffness ratio of dam and base elastic modulus is0.5-2.0. When the dam is built on soft base, larger cross section with smaller elastic modulus than base can be taken to satisfy the strength and anti-sliding requirements.(4) Principals of dam protection design are proposed. CSG dam has small and even deformation distribution. Result of analysis of stress, deformation and durability of CSG dam demonstrate that the deformation difference between dam crest and dam bottom is little, which is good for the protection panel. Principals of dam protection design, that are to set anti-seepage panel in the upstream slope and protection panel in the downstream slope, are proposed.(5) Analysis model and damage pattern of CSG overloading are discussed. Safety margin of CSG dam is analyzed. CSG is a typical elasto-plastic material. Elasto-plastic constitutive model, smeared cracking constitutive model and elasto-plasitic damage constitutive model all can reflect the strain-stress relationship to some extent. Research shows that elasto-plasitic damage constitutive model is more suitable for CSG, although it may increase some calculation price. The difference of seepage stress on different elevation should be considered properly. For critical analysis, except the instability of dam-base system, dam stability and vibration characteristics should be checked at the same time. In this thesis, point anti-sliding safe factor method is tried to the critical analysis. The overloading capacity of CSG dam is quietly large. In a large scale of overloading, the dam works in elastic condition. Comprehensive study shows that, for a100m high CSG dam, the critical loading capacity is about7.0.(6) Seismatic capacity of CSG dam is analyzed. The difference between CSG and concrete and the influence factors on dynamic performance of CSG are analyzed. Based on the analysis, dynamic performance parameters of CSG are recommended. Seismatic response analysis is modeled. It is recommended that during seismatic analysis of CSG dam, dynamic properties of CSG material, dynamic pressure of reservoir water and the damping of infinite base should be considered properly. The seismatic analysis shows that, for a100m high CSG dam, when it’s subjected to7intensity earthquake, the dam works in elastic condition, and almost all area of CSG dam is under compressive condition. Compared with the static result, the seismatic stress is quite small, which shows good aseismatic capacity of CSG dam.(7) Comprehensive structural analyses are made to Shoukoubao Project. Based on the analysis, dam-base interface, cross section, material strength and structural measures on dam protection are advised and are adopted by the designer.