Study On Lateral Pressure Of Precast Formwork In Rockfill Concrete Da

In recent years,the rock-filled concrete technology has been rapidly developed and applied in China,the continuous development of this technology has led to the production of prefabricated block templates.The formwork has the characteristics of high strength,no deformation,simple construction,economic and environmental protection,etc.,and is better than the steel formwork used in conventional construction.However,due to the fact that the self-compacting concrete used in rockfill concrete technology generates greater lateral pressure than conventional concrete,and there is still a lack of research on the stress conditions of precast block formwork in such projects,and at the same time,with the continuous changes of construction technology,it remains to be verified whether the calculation formula for formwork side pressure in the current specifications is applicable to the calculation of prefabricated block formwork side pressure.Therefore,the research on the lateral pressure of precast block formwork in rockfill concrete dams has important theoretical value and practical significance for the design and use of precast block formwork in related projects.This article first summarizes the development history of the formwork lateral pressure formula given in the four industry standards and specifications of domestic housing construction,railway construction,road and bridge construction,and water conservancy construction,and on the basis of a certain engineering condition,calculating the formwork side pressure using typical domestic and foreign formwork side pressure formulas,then comparing and analyzing the problems existing in the calculation of formwork side pressure.The results show that the concrete slump,pouring velocity of the concrete,the ambient temperature,and the initial setting time₀ have a negligible effect on the pressure side of the form,but there is no standard formula to consider the above factors at the same time,as a result,even under the same calculation condition,there are differences in the side pressure of the formwork calculated by each standard formula.Secondly,the self-concrete concrete lateral pressure test of the preformed block formwork is carried out at the construction site,and using an earth pressure box to collect data at different template heights,and analyzing the distribution and change rule of lateral pressure on prefabricated block formwork.At the same time,based on the test conditions,compare the theoretical values calculated by typical domestic and foreign standard formulas with the measured values.The results show that the lateral pressure of self-compacting concrete on prefabricated block formwork varies approximately linearly along the height of the formwork,approaching the trend of hydrostatic pressure,and the maximum value is at the bottom of the formwork;finally,it tends to be stable,which will be significantly reduced after reaching the peak;the calculation results of the Code for Construction of Hydraulic Concrete（SL677-2014）are more consistent with the measured value,and the use of this formula has important reference value in the calculation of the lateral pressure of dense concrete on precast block formwork.Finally,on the basis of the experimental results,the finite element software is used to simulate and analyze the preforms of different masonry height and age of preforms,and the stability and safety coefficients are checked for all the simulated working conditions.The results show that,with the increase of the masonry height,although it can enhance the dead weight of the formwork,making the stress distribution more uniform,it will also lead to the increase of the load on the side of the form,the displacement of the formwork and the loss of mortar stiffness between the precast blocks;as the age increases,the formwork displacement and mortar stiffness loss decrease;the safety coefficient of anti-sliding and anti-overturning stability decreases with the increase of formwork height and increases with the increase of age.Comprehensive consideration is given to the stress,displacement,mortar stiffness loss and stability of the prefabricated block formwork under different working conditions,it is recommended to use the formwork with a age of 3 days and 4 layers of prefabricated blocks for construction.