基于冻融作用的氯盐渍土-钢块界面力学模型

Mechanical model of chlorine salinized soil-steel block interface based on freezing and thawing

在中国西北特殊气候环境下冻融作用是一种风化过程,反复改变着土体的微结构和物理性质,强烈影响着土体与结构的相互作用。针对冻融作用对盐渍土-结构接触面力学特性的影响,进行不固结不排水直剪试验,开展了冻融次数、含盐量、基质吸力等因素对非饱和氯盐渍土-钢块接触面力学性能影响的相关研究。试验结果表明,不含盐时接触面力学参数(黏聚力与内摩擦角)随冻融次数增加均先增大后减小,含盐时接触面黏聚力随冻融次数增加呈下降趋势,内摩擦角略有所增大;冻融前后接触面力学参数随着含盐量的增大先减小后增大,均存在含盐量阈值;未冻融时接触面力学参数含盐量阈值约为8%,随着冻融次数增加,该阈值有所变化;接触面基质吸力随冻融次数增加大体呈减小趋势并最终趋于稳定,随含盐量增加先减小后增大,基质吸力含盐量阈值约为10%;接触面剪应力-剪切位移分为线弹性变形阶段和强化阶段,竖向荷载较小时表现为弱硬化,未出现明显的应变软化现象。对接触面剪应力-剪切位移适用性模型进行评价发现龚帕兹模型能够与试验结果很好地吻合,据其建立了冻融作用的氯盐渍土-钢块界面力学模型,基于试验数据验证了其可靠性。

Freezing and thawing process,as a weathering process,is very common in the Northwest China.It repeatedly changes the microstructure and physical properties of the soil,and strongly affects the interaction between soil and structure.In view of the influence of freezing and thawing on the mechanical properties of salinized soil-structure contact surface,the shear tests under unconsolidated and undrained conditions were applied,considering the effects of freezing and thawing cycles,salt content,matrix suction and other factors on the mechanical properties of unsaturated chloride salinized soil-steel interfaces.The results showed that when the salt was not contained in the soil,the mechanical parameters(e.g.cohesion and internal friction angle)of the interface increased at first and then they decreased with the increase in the number of freezing-thawing cycles.When the salt was contained in the soil,the cohesion of the interface between the salinized soil and steel decreased,but the internal friction angle slightly increased with the increase in the number of freezing-thawing cycles.Before and after freezing and thawing,the mechanical parameters of the interface decreased at first and then increased with the increase in salt content,including threshold values of salt contents.Before the freezing-thawing process,the mechanical parameters of the interface have a salt threshold value of 8%.When the number of the freezing-thawing cycles increases,the threshold changes.The suction force of the matrix at the interface generally decreased with the increase in cycles of freezing-thawing process and it eventually stabilized.It firstly decreased and then increased with the increase in the salt content.The salt threshold of matrix suction is approximately 10%.The shear stress-shear displacement of the interface presented two stages including the linear elastic deformation and strengthening stages.When the vertical load is small,the shear stress-displacement curves show weak hardening characteristics,and no obvious strain-softening phenomenon occurs.Therefore the applicability of the shear stress-shear displacement modes at the interface were evaluated and it is found that the Gongpaz model can be well matched with the experimental results.Thus the mechanical model of chlorine salinized soil-steel block interface was established and its reliability was also verified by the experimental data.