生物炭对三峡库区紫色土力学性能的影响OA

To investigate the effects of biochar particle size and mixing ratio on the mechanical properties of purple soil in the Three Gorges Reservoir area,we used purple soil from the area as the research object.Biochar dosages were set at 2%,4%,and 8%,with particle sizes of<0.25 mm,0.25～0.5 mm,0.5～1.0 mm,and 1.0～2.0 mm;a control check(CK)group without biochar addition was also established.Direct shear tests and unconfined compressive strength tests were conducted to analyze the stress-strain curves,cohesion,internal friction angle,and unconfined compressive strength of specimens under different dosages and particle sizes,in order to clarify the effects of biochar particle size and dosage on the mechanical properties of purple soil.The results showed that:① The reinforcement effect of medium-sized biochar(0.25～1.0 mm)was significantly stronger than that of fine-sized(<0.25 mm)and coarse-sized(1.0～2.0 mm)biochar;② Biochar dosages of 2%and 4%significantly im-proved the mechanical properties of purple soil(P<0.05);③ However,the improvement weakened when the dosage reached 8%,especially for the particle size of 1.0～2.0 mm,where the unconfined compressive strength was even 22.95%lower than that of CK;④ The specimen exhibited the best mechanical properties at a biochar particle size of 0.25～0.5 mm and a dosage of 4%,with shear strength and compressive strength increasing by 47.96%～58.00%and 49.35%,respectively,compared with those of CK.Biochar incorporation affects cohesion and internal friction angle by modifying the arrangement and contact character-istics of soil particles,and also absorbs strain energy when subjected to stress,thereby retarding crack propagation.