Test On The Penetration Law Of Dump Clay-Sandstone Mixture Based On Fractal Theory

The loose soil-rock mixture is an important part of the dumping ground of open-pit coal mine.Due to the existence of rainfall infiltration,its hydraulic properties directly affect the stability of the dumping site.In this paper,will take the dump site of Antaibao Open-pit Coal Mine as an example,and the clay-sandstone mixture sample was made in the field.Due to the discontinuity of the earth-moving operation in open-pit coal mines,the stress state of the soil-rock mixture was determined.A similar simulation test of the clay-sandstone mixture was designed.The clay-sandstone mixture was subjected to a grading loading consolidation test through a GDS-based triaxial apparatus.The triaxial permeability test was carried out to study the influence of different stone content and different particle size fractal dimension on the penetration law of the sample under different osmotic pressures.The fractal theory and the mathematical foundation of fractal are introduced.Based on the research results of the fractal characteristics of the clay-sandstone mixture and the theoretical basis of the fractal dimension calculation,the clay-sandstone mixture samples with different stone contents are sieved and tested.The particle size gradation curve and the particle size fractal dimension curve distinguish the good gradation and the optimal gradation according to the number of fractal dimension values,and serve as a variable index of the penetration test.The clay and sandstone in the dump of Antaibao Open-pit Coal Mine were selected as test materials.The particle size of sandstone was 1-10 mm after the clay was sifted through 1mm screen.The liquid limit,plastic limit and plastic index of clay,the proportion of sandstone and the maximum dry density of sandstone were determined.Based on the fractal theory,a clay-sandstone mixture sample with 30%,40%,50%,60% of stone content and two fractal dimension values and only one particle size fractal dimension was prepared to determine the match ratio distribution of clay and sandstone.The sample size was determined to be 50 mm in diameter and 100 mm in height.The sample moisture content was set to 13%.The triaxial permeation test is designed and implemented.The composition and working principle of the GDS triaxial apparatus are introduced.The GDS permeation module is used to carry out the permeation test.During the test,confining pressure and axial pressure are applied to the sample,and triaxial permeation test is carried out by setting different pressure differences between upper and lower heads,and according to the variation curve of seepage water flow with time,we can see the seepage velocity of clay-sandstone mixtures when they form stable seepage.The seepage characteristics of clay-sandstone mixtures are characterized by the relationship between seepage velocity and seepage pressure.Based on the analysis of triaxial permeability test data,the non-linear seepage characteristics of clay-sandstone mixture samples with high stone content were obtained.With the increase of seepage pressure,the seepage compaction phenomenon appeared in the samples with the same stone content,and the seepage velocity showed a decreasing trend,when the seepage pressure reaches a certain value,the seepage failure will occur in the samples with high stone content,and the larger the stone content,the smaller the seepage pressure corresponding to the seepage failure phenomenon.The seepage velocity of the sample with only one fractal dimension of particle size varies linearly with the seepage pressure,and its internal structure is more compact,and its ability to resist seepage damage is stronger.