柔性壁酸渗透条件下花岗岩残积土力学特性试验研究

Experimental Study on Mechanical Properties of Granitic Residual Soil Under Acid Infiltration in Flexible Wall Permeameter

自然条件下的残积土经酸雨侵蚀,发生化学-力学耦合作用。酸污染残积土性状与土颗粒特征、粒间胶结物和污染浓度、粒间液体介质等有关。三轴柔性壁渗透法通过模拟真实的土体固结应力状况,利用一定渗透压使酸液在土体内部渗流,有效模拟酸雨的淋滤作用,该方法可以精准控制及检测围压、渗透压、及渗透时间等参数。完成酸液渗透试验之后,利用三轴仪检测酸渗透试样的抗剪强度,同时收集过滤处理的酸液对花岗岩残积土试样进行三轴柔性壁渗透试验,可模拟酸雨加速侵蚀过程,反映残积土在长期酸雨作用下的力学特性规律。试验结果表明:渗透液pH值降低加快残积土渗透系数衰减,渗透系数随反应时间呈幂指数衰减;利用原子光谱分析法检测渗透液Fe^(3+)、Ca^(2+)、Mg^(2+)浓度,发现随着渗透液pH值降低,渗透流量和渗透液离子浓度减小;不同酸渗透条件下花岗岩残积土重塑样的不排水剪切试验应力应变曲线呈应变硬化,有效偏应力峰值大小依次为:pH1>pH7>pH3,超静孔隙水压力变化随轴向应变增大呈现先增大而后逐渐减小的趋势,黏聚力随着渗透液pH值升高,渗透时间增长而降低。柔性壁渗透法可作为一种酸雨加速侵蚀试验方法,探讨残积土在长期酸雨作用下的力学性质变化规律。

Natural residual soil is eroded by acid rain,resulting in chemo-mechanics coupling.Characteristics of acid residual soil are related to soil particles,intergranular cement,pollution concentration and intergranular liquid medium,etc.Triaxial flexible wall infiltration method simulates consolidation stress,uses a certain osmotic pressure to make acid solution flow in the soil,and effectively simulates acid rainleaching.It can accurately control and detect the parameters such as confining pressure,osmotic pressure and infiltration time.When the acid permeation test is completed,the triaxial apparatus is used to detect shear strength of acid permeation specimens,collecting filtered acid to conduct a triaxial flexible wall permeating test,which can simulate acid rain erosion and reflect residual soilmechanical characteristics under long-term acid rain.The decrease of seepage solution pH value accelerates permeability coefficientattenuation,and permeability coefficient decays exponentially with reaction time;Permeate flow and ion concentration decrease with pH value decline,considering concentrations of Fe^(3+),Ca^(2+)and Mg^(2+)detected by atomic spectrometry.Under different acid infiltration conditions,the CU teststress-strain curve appears to strainhardening,and the deviatoric stresspeak value is as follows:pH1>pH7>pH3.Excess pore-water pressure first increases and then decreases gradually with axial strain increase.Cohesion decreases with pH value and infiltration time increase.Flexible wall infiltration can be used as an accelerated acid rain erosion test method to explore residual soil mechanical properties under long-term acid rain.