Q_(3)古土壤强度及其结构性研究

Strength and structure of Q_(3) paleosol

古土壤是黄土地层的重要组成部分,但目前对古土壤力学性质的研究相对较少。为研究古土壤的强度及其结构性,以西安某地Q3古土壤为研究对象,通过土力学途径,对原状、重塑、饱和原状古土壤进行无侧限抗压强度试验,得到了相应状态古土壤的无侧限抗压强度,计算得出其初始结构性指标;通过复合幂指数模型,得到了原状、重塑古土壤无侧限抗压强度随含水率变化的表达式,分析了原状、重塑古土壤无侧限抗压强度、扰动灵敏度、浸水灵敏度及构度指标的变化规律。结果表明:古土壤的结构性强,在饱和状态时,其破坏形态仍然为脆性破坏。在密度、湿度、粒度相同条件下,原状古土壤的强度小于重塑古土壤的强度,其扰动灵敏度小于1,与一般黄土的规律截然相反;古土壤的浸水灵敏度、构度指标随着含水率的增加而减小,但在含水率较小或较大时,构度随含水率的变化均不大,且构度指标也可小于1,说明古土壤具有与黄土不同的结构特征。

Paleosol is an important part of loess stratum,but there are few researches on its mechanical properties.In order to study the strength and structure of paleosol,Q3 paleosol in Xi’an is taken as the research object.Through the way of soil mechanics,the unconfined compressive strength test is carried out for undisturbed,remolded and saturated paleosol.The unconfined compressive strength values of the paleosol in the corresponding states are obtained,and the initial structure index is calculated.Based on the composite power exponent model,the expressions for unconfined compressive strength of the undisturbed and remolded paleosol with the water content are obtained,and the rules of the unconfined compressive strength,the disturbance sensitivity,the immersion sensitivity and the structure index of the undisturbed and remolded paleosol are analyzed.The results show that the structure of paleosol is strong,and its failure mode is still brittle when it is saturated.Under the same density,humidity and particle size,the strength of undisturbed paleosol is less than that of remolded paleosol,and its disturbance sensitivity is less than 1,which is contrary to the law of general loess.The immersion sensitivity and structure index of the paleosol decrease with the increase of water content,but when the water content is small or large,the change of structure with water content is not large,and the structure index can be less than 1,which shows that the paleosol has different structure characteristics from loess.