Simulation Study On Seepage Characteristics And Temperature Control Of Cemented Sand And Gravel Dam

The cemented granular dam is proposed on the basis of hard-filled dams and rockfill concrete.It is a new type of dam between earth-rock dams and concrete dams.It has the characteristics of high safety,economical cost,and environmental friendliness.Cemented sand and gravel,as a typical cemented granular material,has been popularized and applied in our country.As a basic material,cemented sand and gravel has accumulated a wealth of experimental results in terms of physical and mechanical properties.At the same time,the cemented sand and gravel aggregate has not been strictly screened and adjusted by gradation,and it has a large dispersion,and has a large porosity and permeability.Compared with concrete materials,although the amount of cement is less and the adiabatic temperature rise is lower,when developing towards high dams,under different construction environments and construction techniques,its temperature stress is also one of the issues that have to be considered.Therefore,this paper takes the basic mechanical properties and compressive strength of cemented sand and gravel as the research object,and establishes a data set of its mix ratio and its corresponding compressive strength.With the aid of response surface methodology,a response model with fly ash content,sand ratio,and water-binder ratio as influencing factors is built,and the influence of each factor and their interaction on compressive strength is analyzed,and the key to cemented sand and gravel is established by BP algorithm Prediction model of mix ratio parameters on basic mechanical properties.At the same time,taking our country’s Shoukoubao cemented sand and gravel dam as the research object,the improved node virtual flow method and temperature stress simulation program are used to calculate and analyze the seepage characteristics and temperature stress distribution of the cemented sandgravel dam.The results show that:(1)The response surface methodology can establish a high-precision multivariate simplified regression model for the 28 d compressive strength of cemented sand and gravel with fly ash content,sand ratio and water-binder ratio as the influencing factors.At the same time,a single regression model can be obtained based on the significance test.The significant degree of influence of factors on compressive strength is water-binder ratio> fly ash content> sand ratio;the significant degree of influence of two-factor interaction on compressive strength is water-binder ratio and sand ratio> water-binder ratio and fly ash Blending quantity> fly ash content and sand ratio;at the same time,according to the optimization results,when the 28 d compressive strength value reaches the maximum predicted value of 8.08 MPa,the optimum content of fly ash is 50%,and the optimum sand ratio is 0.2,The best water-binder ratio is 1.0.(2)Using Boxplot method to preprocess the 28 d compressive strength data of cemented sand and gravel,after removing the three sets of large dispersion values,the skewness kurtosis test and the single-sample KS test are used to obtain the cemented gravel The 28 d compressive strength of stone conforms to the law of normal distribution.On this basis,based on the BP neural network,the main indicators of cemented sand-gravel mix ratio are used to predict the compressive strength,and the average relative error and average absolute error are 7.16% and0.39 MPa,respectively.The predicted value is in good agreement with the measured value.Higher,the forecast effect is better.(3)Based on the improved node virtual flow method,the three basic working conditions and two special working conditions of the Shoukoubao cemented sand and gravel dam were analyzed.The results show that the structure of the cemented sand-gravel dam is reasonable and feasible.The upstream impervious layer and the downstream protective layer play a vital role in the distribution of the seepage field of the dam.Therefore,the construction quality of the upstream and downstream slabs must be ensured.It is recommended that in order to effectively reduce the infiltration line,drainage facilities can be set downstream to induce the discharge of unfavorable water seepage,such as drainage prisms,drainage holes,etc.(4)With the help of temperature stress simulation analysis program,numerically simulate the temperature field and stress field distribution from the construction period to the completion period of the Shoukoubao cemented sand and gravel dam,and analyze the evolution law of the two.The results show that,due to the large volume of the dam body,the temperature stress of the cemented sand-gravel dam cannot be ignored.There are many influencing factors.The necessary and simplified temperature control measures should be taken according to the actual situation to effectively reduce the surface and special location cracking problems.Such as windshield and low temperature seasons,pay attention to the insulation of the warehouse surface,and ensure the quality requirements of the outsourcing concrete,which provide references for the same type of projects.