Strength and Micro-Mechanism of Tailings-Type Vegetation Substrate Improved by Cement-BPSF
In order to solve the problem of lack of natural soil required for ecological restoration of mine slope,low-alkali cement and bagasse-polyacrylamide-super absorbent polymer-acid fertilizer(Bagasse-PAM-SAP-Fertilizer,BPSF)were used as modifiers to improve the properties of tailings.The vegetation substrate which can be used for ecological restoration of mine slope was prepared.Through the L9(34)orthogonal design,the shear tests were carried out on the initial samples of vegetation substrate with different ratios.Taking the initial(3 d)shear strength as the evaluation index,the optimal ratio of the substrate was determined by range analysis.The effect of curing age on the shear strength of the substrate was studied by the shear tests on the samples with the optimal ratio of the substrate at different ages.The shear strength characteristics and micro-mechanism of cement-BPSF synergistically improved tailings-type vegetation substrate were analyzed by thin section identification,scanning electron microscopy(SEM)and X-ray diffraction(XRD)tests.The results show that the contents of cement and bagasse is the most significant factor affecting the strength of the substrate.The initial shear strength of the substrate increases with the increase of the content of cement and bagasse.With the increase of age,the internal friction angle of the substrate begins to decrease after reaching the peak,and the failure mode of the substrate changes from the initial ductile failure to brittle failure.The tailings-type vegetation substrate improved by cement-BPSF has the soil-like structure and strength required for the growth of each plant.The optimal substrate ratio is 12％of cement,4％of bagasse,0.6％of PAM,0.15％of SAP and 1.2％of acid fertilizer.
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