Filling contents of earth-rock dam:
According to different construction methods, earth-rock dams are divided into dry filling and rolling (rolling type), water filling, hydraulic filling (including falling dams) and directional blasting construction. Among them, the roller compacted earth-rock dam is the most common.
The construction work of RCC earth-rock dam includes preparatory work, basic work, auxiliary work and additional work.
Factors affecting the filling strength of earth-rock dams;
1. Strength of brick and mortar
The strength index of brick and mortar is the most important factor to determine the strength of masonry. Brick and mortar have high strength, so does the compressive strength of masonry. The test shows that improving the strength grade of brick can improve the compressive strength of masonry more than improving the strength grade of mortar. In general, the strength grade of brick is increased by one grade, and the compressive strength of masonry is only increased by about 15%, while the compressive strength of masonry is increased by one grade, which can be increased by about 20%. Due to the increase of cement consumption after the mortar strength grade is improved, it is not advisable to increase the mortar strength grade too high under the condition of a certain brick strength grade. However, in rubble masonry, improving mortar strength grade has great influence on masonry compressive strength.
2. Elastoplasticity of mortar
Mortar has obvious elasticity and plasticity. When mortar with large deformation rate is used in masonry, the bending, shear stress and transverse tensile stress in a single brick increase, which adversely affects the compressive strength of masonry.
3. The fluidity of mortar paving
Mortar has great fluidity, and it is easy to pave mortar joints with uniform and dense thickness, so it can reduce the bending and shear stress generated in the brick body, that is, it can improve the tensile and compressive strength of masonry to a certain extent. Mixing mortar instead of cement mortar is to improve the fluidity of mortar. The fluidity of pure cement mortar is poor, so the strength of pure cement mortar masonry is reduced by about 5%~ 15%. However, we can't overestimate the beneficial influence of mortar fluidity on masonry strength, because mortar fluidity is large and the deformation rate after hardening is also large, so in some cases, the strength of masonry may be reduced. Therefore, the best mortar should have good fluidity and high compactness.
4. Masonry quality
The fullness of horizontal mortar joint, the thickness of horizontal mortar joint, the moisture content of brick and the bonding method are all related to the quality of masonry. From the analysis of compressive stress state of masonry, it can be seen that the influence of masonry quality on compressive strength of masonry essentially reflects its adverse influence on complex stress in masonry. Experiments show that the fuller the horizontal mortar, the higher the compressive strength of masonry. When the fullness of horizontal mortar joint is 73%, the compressive strength of masonry can reach the specified strength index. Therefore, in the Code for Construction and Acceptance of Masonry, the plumpness of horizontal mortar joint is required to be greater than 80%. When laying clay brick masonry, the brick should be watered and wetted in advance. The research shows that the compressive strength of masonry increases with the increase of water content of clay brick masonry. Compared with clay brick masonry with general water content, the compressive strength of dry brick masonry and saturated brick masonry decreases by 15% and increases by 10% respectively. However, the moisture content of clay brick masonry has different degrees of influence on the shear strength of masonry. When the moisture content is above 90%, the shear strength of masonry decreases. In addition, the clay brick is too wet during construction, which makes it difficult to operate, and the wall can't be kept clean because of slurry flow. Therefore, as the standard of normal construction quality, it is required to control the moisture content of clay brick at 10% ~ 15%. The thicker the horizontal mortar joint in masonry, the greater the lateral deformation of mortar, the greater the lateral tensile stress in brick, the more complicated the stress state in masonry and the lower the compressive strength of masonry. Usually, the horizontal mortar joint thickness of brick masonry is required to be 8 ~ 12 mm, and the bonding mode of masonry has obvious influence on the strength and integrity of masonry. Usually, the masonry with one roof, plum blossom roof and three roofs has good integrity, and the compressive strength of masonry can be guaranteed. However, if the masonry method is adopted, its compressive strength will be greatly reduced due to the poor integrity of masonry.
5. Shape of brick
The regularity of brick shape significantly affects the strength of masonry. When the surface is distorted, mortar joints with different thicknesses will be formed, which will increase the inhomogeneity of mortar layer, cause greater additional bending stress and make bricks break prematurely. When the thickness of some bricks in a batch is different, the thickness of mortar joint will be different, which will have a very bad influence. This factor can reduce the strength of masonry by 25%. When the brick strength is the same, the compressive strength of lime-sand brick and dry-pressed brick masonry is higher than that of plastic-pressed brick masonry. The reason is that the shape of the former is neater than the latter. Therefore, improving this index of brick is also one of the important tasks of brick-making industry. The size of brick, especially the height (thickness) of brick has great influence on the compressive strength of masonry. The bending, shearing and tensile capacities of large height blocks are improved, and the compressive strength of masonry is obviously improved. However, it should be noted that the brittleness of masonry under compression also increases with the increase of block height. In addition, the factors that affect the compressive strength of masonry include age, filling degree of vertical mortar joint and test method. I won't go into details here.
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