为了探究农业生产实践中经过人工夯实的田坎在自然营力作用下的垮塌变形机理,通过采集黄土区梯田土壤,对其进行室内击实、模拟干湿交替处理和剪切试验,探究了干湿交替过程对夯实土壤抗剪强度的影响。结果 表明:在试验条件下,随着干湿交替次数的增加,土壤的粘聚力呈现逐渐增加的趋势。土壤的内摩擦角逐渐降低,并在第7次干湿交替时达到最小值。在100 kPa垂直压力作用下,土壤的抗剪强度受影响不明显; 在200 kPa垂直压力作用下,土壤抗剪强度先增加然后趋于稳定; 而在300,400 kPa垂直压力作用下,土壤的抗剪强度先增加然后逐渐降低,并趋于稳定,并在第2次干湿交替时达到最大值。此外,在相同干湿交替次数的情况下,随着垂直压力的增大,土壤的抗剪强度逐渐增大,说明垂直压力与土壤的抗剪强度呈正相关。经过显著性分析,干湿交替过程对土壤内摩擦角的影响大于相同条件下对粘聚力的影响。干湿交替过程对夯实土壤的抗剪强度有显著影响,随着干湿交替次数的增加,土壤的抗剪强度降低,其中土壤粘聚力增加,而内摩擦角下降。
The chief aim of this paper is to explore the mechanism of deformation of manual rammed ridges under natural forces in agricultural production practice. Several terrace soil samples were collected from loess area, rammed and then put into wet-dry cycle to observe its impact on shear strength in laboratory. The results showed that with the increase of the frequency of wet-dry cycle, cohesion of soil increased gradually; internal friction angle decreased gradually, and reached the minimum at the 7th cycle; under 100 kPa vertical pressure, no significant impact was found on shear strength; under 200 kPa vertical pressure, shear strength first increased and then stabilized; under 300 kPa and 400 kPa vertical pressure, shear strength first increased then decreased and at last stabilized and reached the maximum at the 2nd cycle; in addition, with the same frequency of wet-dry cycle, shear strength increased gradually with the increase of vertical pressure, indicating that there was a positive correlation between them; the significance analysis proposed that wet-dry cycle had a greater impact on internal friction angle than on cohesion under the same condition. These findings implicate that shear strength is affected significantly by wet-dry cycle. With the increase of the frequency of the latter, shear strength decreases, cohesion of soil increases, and internal friction angle decreases.
