Experimental Study on Restoration Materials of Earthen Sites Based on Polypropylene and Lime Modification Technology
The main building material of earthen sites is soil and has been exposed to the natural environment for a long time,their damage is common and serious,and urgently needs to be restored.Especially in northwest China,there are many silty sites with poor engineering properties and difficult reinforcement.The modified soil samples were prepared by adding lime and polypropylene fibers separately and in a mixed manner in loess.Direct shear,compression,wind sand erosion,freeze-thaw,and water stability tests were conducted to verify the feasibility of using polypropylene and lime as restoration materials for silty sites.The test shows that the shear strength of the soil can be improved by adding lime or polypropylene fiber alone.When 9%lime or 0.25%polypropylene fiber is added,the internal friction angle and cohesion of the modified soil can be as high as 48.9°and 107.11kPa,and the compressibility of the soil is also significantly reduced.However,the addition of polypropylene fiber alone will lead to the deterioration of the water stability of the modified soil,which is due to the fact that the polypropylene fiber in the soil increases the infiltration channel of water.By using 0.25%polypropylene fiber and 9%lime to make mixed modified soil samples,the cohesion and internal friction angle are not only 66.7%and 28.9%higher than those of single-doped modified soil,but also the water stability of the samples is significantly enhanced.The ability to resist wind-sand erosion and freeze-thaw is also greatly improved,and the overall performance is better.Therefore,the mixed use of lime and polypropylene fiber can more effectively improve the engineering performance of silt.
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