| As a typical mass concrete,piled concrete is mainly composed of self-compacting concrete to fill the piled stone skeleton by its gravity,forming a piled concrete with certain strength and safety.Since pile concrete uses a large number of inert materials such as boulders and fly ash in construction,the pile concrete construction process has the advantages of low heat of hydration,high strength and low cost,which makes the pile concrete construction process widely used in arch dam construction.In some of the constructed or under-construction rockfill concrete arch dam projects,they are poured through the silo without dividing the horizontal joints and greatly reduce or even eliminate the temperature control measures.However,the structural characteristics of arch dams make them more sensitive to temperature loads and often produce cracks due to temperature changes.At present,there are few studies on the relationship between the amount of fly ash and the rate of stacked stone concrete and the adiabatic temperature rise,and simulation studies are scarce on the temperature and stress fields of stacked stone concrete arch dams with through-bin casting and no temperature control measures.In this paper,we investigate the relationship between fly ash admixture and stone stacking rate and adiabatic temperature rise by changing the admixture of fly ash in self-compacting concrete and reducing the size of stone stacking concrete to investigate the change of fly ash admixture and stone stacking rate.The following conclusions are drawn.(1)The adiabatic temperature rise of self-consolidating concrete is linearly and negatively correlated with the amount of fly ash,and the adiabatic temperature rise decreases with the increase of fly ash,and a large amount of fly ash mixes significantly reduces the adiabatic temperature rise of self-consolidating concrete,which reduces the risk of cracking of pile concrete.In addition,with the increase of fly ash admixture,the temperature rise induction period of self-compacting concrete is prolonged and the maximum temperature rise rate peak level is reduced.(2)The adiabatic temperature rise of stacked stone concrete is linearly and negatively correlated with the stacking rate,and the adiabatic temperature rise decreases with the increase of the stacking rate.Due to the existence of piled stone blocks,when the self-compacted concrete is hydrated and heated,the piled stone inside the specimen will absorb part of the heat from the self-compacted concrete due to the temperature difference until the temperature converges with that of the self-compacted concrete,which makes the temperature rise of the specimen much lower,the higher the piled stone rate is,the more heat is absorbed by the piled stone,the less heat is released from the specimen,and the adiabatic temperature rise is smaller.At the same time,the ambient temperature of cement hydration also decreases,which reduces the cement activity to a certain extent,resulting in a delay in the peak temperature rise rate of stacked stone concrete compared with that of self-compacting.(3)During the construction period,the high-temperature zone of the arch dam is generally concentrated in the interior of the casting layer,reaching a maximum of 43.5°C.The hydration temperature rise of the dam body is around 14°C,which is similar to the adiabatic temperature rise test results of the rockfill concrete.The high tensile stress area of the dam body is mainly concentrated in the left and right shoulders of the upstream and downstream face of the dam at the elevation of 1/2 to 2/3,which changes periodically with the temperature,and the maximum tensile stress is 1.51 MPa after the equivalent force calculation.The maximum tensile stress occurs in the construction period and the empty storage period and the tensile and compressive stresses of the whole cycle are by the stress control specification of the arch dam,and the possibility of cracks in the arch dam is small. |
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