Influence Of Test Method On Dry-Wet Cycle Compression Characteristics And K₀ Coefficient Of Sandstone-Mudstone Particle Mixture

Sandstone and mudstone particle mixture,as one of the main building fillers,is often used in reservoir dam,reservoir bank and fill engineering.However,repeated rainfall and exposure to sunlight can affect the engineering characteristics of sandstone and mudstone particle mixture,but its mechanism is not clear.In order to find out its influence law,laboratory tests were carried out to simulate the influence of repeated rainfall and exposure to sunlight on the engineering characteristics of sandstone and mudstone particle mixture by using the sequence of dry-wet cycles and loading.Based on Chongqing Construction Science and Technology project “Engineering Characteristics and constitutive Model and Application of sand and mudstone particle mixture”,this thesis carried out experimental research on the compression characteristics and static lateral pressure coefficient of sandstone and mudstone particle mixture,and explored the influence of loading and the sequence of dry-wet cycles on both.The main research achievements of this thesis are as follows:(1)The maximum dry density and optimal water content of sandstone and mudstone particle mixture were obtained through compaction test;Through the direct shear test,the variation law of cohesion and internal friction Angle of sandstone and mudstone particle mixture with the number of dry-wet cycles is obtained and the formula is fitted.The results show that the cohesion of sandstone and mudstone particle mixture decreases with the increasing number of dry-wet cycles,and the internal friction Angle increases with the increasing number of dry-wet cycles,both of which present a logarithmic distribution with the number of dry-wet cycles.(2)Through the indoor compression test,the dry-wet cycle and loading sequence were changed,and different dry-wet cycle times,soaking time and water temperature were tested,and the differences between the two test methods on the compression characteristics of sandstone and mudstone particle mixture were obtained.The results show that the compressive capacity of sandstone and mudstone particle mixture obtained by the two test methods increases with the increase of dry-wet cycle times,immersion time and water temperature,and the pore ratio decreases accordingly.Under the three factors,the compressive capacity of sandstone and mudstone particle mixture is larger and the pore ratio is smaller.The compressive capacity and pore ratio obtained by the two test methods showed logarithmic relationship with the number of dry-wet cycles,power function relationship with immersion time,and linear relationship with water temperature.(3)Through the indoor static lateral pressure coefficient test,the dry-wet cycle and loading sequence were changed,and different dry-wet cycle times,soaking time and water temperature were tested,and the differences between the two test methods on the static lateral pressure coefficient of sandstone and mudstone particle mixture were obtained.The results show that the static lateral pressure coefficients of sandstone and mudstone particle mixture obtained by the two test methods are increased with the increase of dry-wet cycle times,immersion time and water temperature,and the horizontal load increases.The static lateral pressure coefficients obtained by the two test methods showed a logarithmic relationship with the number of dry-wet cycles and soaking time,and a quadratic polynomial relationship with water temperature.The coefficient of static lateral pressure obtained after dry-wet cycle is too large.(4)By substituting the parameters obtained from the unidirectional compression test and the static lateral pressure coefficient test into the calculation example,it is concluded that both the compression amount and the static soil pressure increase with the increase of the number of dry-wet cycles,soaking time and water temperature.Moreover,the first dry-wet cycles have a large disturbance to the sample,and the compactness decreases,and the external factors relatively increase the deterioration of the mixture,so the results obtained by this method are too larger.