| The cementitious sand-gravel material is a material with a certain strength and shear resistance formed after mixing,paving and vibrating rolling,using a small amount of cementitious materials and the sand-gravel material which is not screened and not washed in the engineering site.With the advantages of safety,environmental protection and economy,the cemented sand&gravel dam with low water head has wide application foreground in various types of hydraulic engineering.In this paper,the effects of water cement ratio and sand ratio on the strength and dispersion of cemented sand&gravel materials are studied by means of the combination of experiment and mathematical calculation,and the strength time-varying model and the corrosion degradation model are established,and the reliability of the cement-gravel dam is analyzed based on the dispersion and permeability of strength.After a series of experimental studies and theoretical analysis,the following results have been obtained:(1)Under the condition of fixed sand ratio and water consumption,the maximum strength is obtained when the water cement ratio is 0.7,and the sand ratio is 30%when the cement ratio is fixed.Water-cement ratio and sand ratio too large or too small will reduce the strength of the material,but the water cement ratio is the main factor affecting strength with the sand rate on the strength of the effect of slow;Dispersion studies show that the specimen group with the greatest strength is less discrete,For example,the coefficient of variation is 0.58 when the water-cement ratio is 0.7,which indicates that the optimum mixing ratio is effective to reduce the dispersion of cementitious gravel materials.(2)The water-cement ratio is the main factor affecting the strength of the material,so combining the amount of cement,the maximum slurry strength that means the internal topological structure of the material and the time parameter,a series of mathematical calculation and analysis is used to establish the time-varying model for predicting the change of strength over time.By comparing the experimental value and model calculation of cementitious gravel material,the maximum error is 14.29%(less than 15%),and the calculation precision is higher,which can provide some reference value for predicting the strength of cementitious gravel material at different time points.(3)Through the dissolution and infiltration test,it can be learned that under water pressure,the strength of cementitious gravel material decreases due to the increase of the weak layer caused by the dissolution of the hydration product and the increase of porosity,and the dissolution model of strength is established by experimental data.After some series of durability experiments,it is shown that adding admixture can improve the durability of cementitious gravel material,and it is suggested to add admixture for enhancing the durability of cement-sand-rock dam.(4)In this paper,the reliability analysis method of cementitious gravel materials is studied,then,by using this method to calculate the data,we can know that the smaller the discreteness of the material is,the larger the reliability of dam is.Under the effect of various factors,as long as the individual discrete factors are within reasonable range,the reliability of the whole dam body system can meet the engineering requirements.In a word,the dispersion of material has a negative effect on the stability of the dam,and it is necessary to reduce the material’s discreteness to meet the engineering safety requirements. |
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