| As a mass concrete structure,due to the influence of hydration heat,the temperature field of concrete gravity dam is unevenly distributed in time and space,and its own deformation is not coordinated.At the same time,it is subject to the foundation constraint,which is easy to produce self constraint stress and foundation constraint stress.If the stress exceeds the crack resistance of concrete,it may lead to cracks in the dam body.Therefore,various measures should be taken to control temperature and prevent cracks in concrete dam construction.The material partition of concrete dam is actually a temperature control measure to reduce the temperature rise of hydration heat.In recent years,in order to improve the quality of some new or reinforcement projects of small and medium-sized concrete gravity dams,there is a trend to gradually improve the concrete grade in the selection of zoning materials.Therefore,it is necessary to study the influence of material partition on the temperature stress of concrete gravity dam.Based on the calculation theory of concrete creep stress,ANSYS and secondary development language APDL and UPFs are applied in this paper.Combined with a concrete gravity dam,three parts of concrete above the regular water level(zone II),below the regular water level(zone III)and inside the dam(Zone V)are taken as the analysis areas,Considering the change of concrete material properties and whether there are temperature control measures,the three-dimensional finite element calculation of dam temperature stress field is carried out,and the influence of different material partition and temperature control conditions on dam temperature field and stress field is analyzed.After calculation and analysis of the selected concrete gravity dam according to the proposed scheme,it is found that the internal stress of the dam without temperature control measures is 1.01 ～ 3.50 MPa,and the internal stress of the dam with temperature control measures is 0.50 ～ 2.02 MPa,with an average reduction of 10% ～ 75%.In the region of material change: when the concrete grade is increased from C20 to C30,the peak value of early stress on the upstream surface increases from 0.72 ～ 0.82 MPa to 0.76 ～ 0.86 MPa,increasing by 5 ～ 6%,the peak value of early stress on the downstream surface increases from 0.81 ～ 0.87 MPa to0.92 ～ 1.04 MPa,increasing by 14 ～ 19%,and the peak value of stress on the upstream boundary increases from 1.46 MPa to 1.62 MPa,increasing by 11%,The peak stress at the downstream junction increases from 1.47 MPa to 1.68 MPa,increasing by 14%;When the concrete grade is increased from C30 to C40,the peak value of early stress on the upstream surface increases from 0.76 ～ 0.86 MPa to 0.79 ～ 0.92 MPa,increasing by 4 ～ 7%,the peak value of early stress on the downstream surface increases from 0.92 ～ 1.04 MPa to 1.04 ～ 1.21 MPa,increasing by 13 ～ 16%,and the peak value of stress on the upstream interface increases from 1.62 MPa to 1.81 MPa,increasing by 12%;The peak stress at the downstream junction increased by 10% from 1.68 MPa to 1.85 MPa.In the region of material change: the peak value of early stress in upstream surface is 17 ～ 55% higher than the allowable stress in early stage of concrete,and the peak value of early stress in downstream surface is 25 ～ 65% higher than the allowable stress in early stage of concrete.The results show that the temperature difference of the foundation is controllable,and the internal and external temperature difference control is difficult in the early stage.The early stress on the upstream and downstream surface is greater than the allowable stress in the early stage of concrete,and cracking may occur;The higher the grade of concrete,the greater the stress,the more difficult the crack is to be controlled,the more strict the temperature control measures are needed;The temperature difference and stress are produced at the junction of the material changing area,but the overall value is small,which does not cause cracking;On the premise of meeting the requirements of impermeability,frost resistance and durability of different parts of the dam,the concrete grade should be reduced as far as possible to reduce the temperature difference between the inside and outside. |
