Study On Critical Value Of Rock And Soil Particle Size Based On Permeability And Its Hydrogeological Significance

The permeability of rock and soil is an important factor that determines the movement and occurrence forms of groundwater and other liquids and gases in rock and soil.Permeability is one of the core issues in the scientific research of groundwater.Whether it is the development and utilization of groundwater or oil and gas,or the prevention and control of groundwater hazards(such as pit water,reservoir leakage),rock and soil permeability is of great significance.In this paper,the influence of the size and mass ratio of the rock and soil particles on the permeability is studied by the seepage test of different size sand samples and the seepage test of two different size sand samples mixed according to different mass ratio.On this basis,the relationship between the particle size and its mass ratio and permeability is theoretically analyzed and applied in practice.The main research results are as follows:1)48 groups of single-diameter sand sample seepage tests were carried out,and the following permeability laws were obtained: as the sand sample size decreased,the corresponding permeability coefficient also gradually decreased,and as the sand sample size became smaller The variation range of permeability coefficient becomes smaller;the sand sample size is divided into four categories according to permeability.0.050 mm is obtained as the critical value of sand sample particle size permeability.2)The seepage test of 595 mixed sand samples was conducted,and the following permeability laws were obtained:(1)When the larger particle sand sample is mixed with the smaller particle sand sample,the permeability coefficient of the mixed sand sample is always smaller than that of the larger particle sand sample;When the proportion of small particles reaches 50% to 75%,the permeability coefficient of the mixed sand sample is less than or equal to that of the small particle sand sample.(2)In the case of the same mass ratio,when the two particles are mixed,the permeability coefficient of the sand sample after mixing decreases as the particle size of one sand sample decreases.However,when the particle sizes of the two particles are similar,the permeability coefficient will be small after mixing.(3)When two different particle sizes are mixed,the permeability coefficient of the mixed sand sample always decreases as the mass ratio of small particles increases.Large-permeability particles generally do not lose permeability when mixed with medium-permeability or small-permeability particles.When the large-permeable particles are mixed with the non-permeable particles,the permeability will only be lost when the mass ratio of the non-permeable particles reaches 75%.When the medium and small permeable particles are mixed with non-permeable particles,the permeability is easily lost.3)According to the theoretical analysis and calculation of previous studies,the critical value of the permeability rock and soil particle size is 3.4 ? 9.1mm,compared with the test results,the reason for the difference is analyzed;According to the channel generalization,the relationship between particle size and permeability coefficient is calculated.Finally,the situation after mixing two different particles is analyzed.4)According to the rock and soil permeability coefficient obtained from the test and the lithology of the loose layer in Datun mining area,the permeability coefficient of each aquifer in the Quaternary loose layer in Datun mining area is estimated,and the estimated results are compared with the measured permeability coefficient of each aquifer.The estimated permeability coefficient is in the same order of magnitude as the measured permeability coefficient,and there is a certain gap in the numerical value.This paper reveals the critical value of rock and soil particle size based on permeability.The results of this study can be used to preliminarily determine the permeability of rock and soil;Through the study of this subject,while the permeability of the rock layer is measured to obtain its permeability,it can also further understand the water resources characteristics of rock and soil with different particle sizes;When the particle size of the rock layer is measured to obtain its permeability,it can also directly determine the size of its transmission capacity to pollutants.The paper has 110 pictures,106 tables,and 87 references.