千枚岩土⁃红黏土混合土抗剪强度试验研究

Experimental Study on Shear Strength of Phyllite Soil-Red Clay Mixed Soil

江西省中北部地区分布着大量千枚岩土和红黏土,其中千枚岩土由于强度低不能满足强度要求常作弃方处理。研究首次提出了用红黏土胶结千枚岩土来提高强度的方法,并开展了千枚岩土-红黏土混合土浸水与未浸水抗剪强度试验。试验结果表明:浸水与未浸水状态下,当红黏土掺和比λ≤60%时,混合土样黏聚力c和内摩擦角φ均随掺合比的增大而显著增大;当λ>60%时,抗剪强度指标增长不明显甚至发生了降低;混合土浸水后,黏聚力和内摩擦角都有一定程度的下降。采用折减系数来描述抗剪强度降低幅度,含水量为14%时,黏聚力折减系数随红黏土掺和比的增长而增长,黏聚力折减系数最大为4.63;含水率为18%和22%时,变化规律不明显,可以取2.7作为保守黏聚力折减系数;混合土样内摩擦角折减系数变化范围为1.04~1.72,当红黏土掺合比为40%和60%时变化范围较小,可取最大值1.44作为掺和比40%~60%时的保守折减系数;基于强度与液塑限试验,提出红黏土掺合比的优选范围为40%~50%。

There are a lot of phyllite soil and red clay in the middle and north of Jiangxi Province.Among them,phyllite soil can’t meet the strength requirements due to its low strength and is often treated as spoil.The method of using red clay to cement phyllite soil to improve the strength was proposed for the first time,the tests of immersion and non-immersion shear strength of phyllite soil-red clay mixed soil were carried out.The test results show that in the state of immersion and non-immersion,the cohesion(c)and the internal friction angle(φ)of the mixed soil samples increase significantly with the increase of mixing ratio,when the mixing ratio of the red clayλ≤60%.Whenλ>60%,the shear strength index doesn’t increase significantly or even decreases.After the mixed soil is soaked in water,both the cohesion and internal friction angle decrease to a certain extent,and the reduction coefficient is used to describe the reduction range of shear strength.The cohesion reduction coefficient increases with the increase of the red clay mixing ratio,and the maximum cohesion reduction coefficient is 4.63 when the water content is 14%.The variation law of cohesion reduction coefficient is not obvious,and 2.7 can be taken as the conservative cohesion reduction coefficient when the water content is 18%and 22%.The variation range of internal friction angle reduction coefficient of the mixed soil samples is 1.04~1.72.The variation range is small when red clay mixing ratio are 40%and 60%,and the maximum value of 1.44 can be taken as the conservative reduction coefficient when the mixing ratio is 40%~60%.Based on the strength and liquid plastic limit tests,it is proposed that the optimal range of red clay mixing ratio is 40%~50%.