在中国黄土高原,黄土和秸秆等农作废弃物最为常见。黄土-秸秆混合料几十年来被广泛应用于冻融循环下使用的民用住宅建筑,但少有文献讨论这种混合料的剪切行为,关于其剪切行为的共识还没有达成。通过一系列大型直剪试验,研究了农作废弃秸秆加筋黄土混合料的抗剪性能,探讨了提高抗剪强度参数的机理。制备试样前,先用热水煮沸法软化秸秆,然后与黄土混合,分别以14%,18%,22%的含水率制备方形试件。大型直剪试验结果表明:①加入到试样中的秸秆阻碍了颗粒的重新排列,导致颗粒间的互锁效应,从而抑制剪切面附近剪切带的发展,增大了摩擦角;②考虑到试样的均匀性和试验的可靠性,秸秆的最优掺量介于0.55%~0.65%;③在剪切盒前后观察到的竖向位移可用于解释应变硬化曲线(持续发展)、应变硬化曲线(小位移斜率和大位移斜率阶段持续发展)逐渐增加的现象。
Abstract
Post-harvest Straw(termed PHS hereafter) and loess are easily accessible in Chinese Loess Plateau. The loess-PHS mixture has been widely applied to the construction of residential houses that have been utilised over decades under freeze-thaw cycles. Notwithstanding that, the shearing behavior of such a mixture has rarely been discussed by published literatures. Thus,a consensus about its shearing behavior has not been reached yet. In this study,the shearing behavior of loess-PHS mixture is investigated using a series of large-scale direct shear(LSDS) tests and the mechanism of improving the shear strength parameters of loess-PHS mixture is analyzed as well. The PHS is firstly treated with hot water and then blended with loess for preparing cubic specimens with moisture content of 14%,18%,and 22%,respectively. The LSDS test results demonstrate that:(1) the PHS added into specimen impedes particle rearrangement and results in particle inter-locking,thereby restraining the development of shear bands in the adjacent of shear plane and leading to an improvement of friction angle;(2) the optimal dosage of PHS is deemed as 0.55%-0.65% considering specimen homogenisation and testing reliability;(3) the vertical displacement observed before and after the shear box can be used to explain the gradual increase of the strain-hardening curve(continuous development) and the strain-hardening curve(two stages of continuous development).
关键词
加筋黄土 /
农作废弃秸秆 /
直剪试验 /
抗剪强度 /
最优掺量 /
黄土高原
Key words
reinforced loess /
post-harvest straw /
direct shear test /
shear strength /
optimal dosage /
Chinese Loess Plateau
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