干湿循环下常春藤根系对云南红土的阻裂效应

Anti-cracking effect of hedera nepalensis roots on Yunnan laterite under wetting and drying cycles

摘要:

为研究常春藤根系对云南红土经历干湿循环作用后裂缝扩展的效应,为边坡生态防护提供参考依据,取典型云南红土土料和常春藤根系,配制一定含水率的云南红土,分别制作纯红土击实试样和不同根系掺量的混合土击实试样,试样压实系数为94.4%。在室内用喷淋和自然风干的方式模拟工程中的红土经历多次降水与蒸发这一干湿循环过程,对经历1-8次循环次数的试样进行裂缝宽度测定并对各组试样的平均最大裂缝宽度值进行统计分析。结果表明:纯红土试样在经历第1次干湿循环后即有微裂缝发育,经历多次干湿循环后,裂缝宽度逐渐增大,在第4次干湿循环后最大裂缝达到毫米级宽度,第6次干湿循环后裂缝扩展趋于稳定;掺10%和20%根系时,第1次干湿循环后就显示出明显的阻裂效应;掺30%根系时,在第4次干湿循环后才显示出较弱的阻裂效应;第8次干湿循环后,掺10%、20%和30%根系试样的平均最大裂缝宽度为纯红土试样的17%、17%和82%,统计分析表明,20%掺根量时阻裂效果最优。

Abstract:

In order to study the constraint effect of hedera nepalensis roots on crack propagation in Yunnan laterite after wetting and drying cycles,and to provide a reference for the slope ecological protection,the typical Yunnan laterite and hedera nepalensis root system are selected to prepare Yunnan laterite with a certain moisture content for research.The compacted pure laterite samples and compacted mixed soil samples with different root content are made respectively.The compacting coefficient for both pure and mixed samples is 94.4%.In the laboratory,spray and natural air drying were used to simulate the drying and wetting cycle of laterite in engineering,and the crack width of samples with 1~8 cycles was measured and the average maximum crack width of each sample was statistically analyzed.The results show that there are microcracks in the pure laterite samples after the 1st dry-wet cycle.The crack width increases gradually after several dry-wet cycles.The maximum crack width reaches millimeter level after the 4th dry-wet cycle,and the crack expansion tends to be stable after the 6th dry-wet cycle.When 10% and 20% of root system is mixed,it shows obvious crack resistance effect after the 1^st dry-wet cycle;when 30% of root system is mixed,it shows weak crack resistance effect after the 4^th dry-wet cycle.After the 8th dry-wet cycle,the average maximum crack widths of the samples with 10%,20% and 30% root systems are 17%,17% and 82% respectively of those of the pure laterite samples.The results of statistical analysis show that the crack resistance effect is the best when the root content is 20%.